HIGH RISK SURGICAL PATIENTS
INTRODUCTION
Despite improvements in our understanding of the pathogenesis of postoperative organ dysfunction,
death and serious morbidity are still common following major surgery. Outcome following major
surgery varies significantly both within and between countries.
Critical care techniques and therapies are increasingly utilised in the operating room. Improved
perioperative care of the high-risk patient has resulted in significant improvements in outcome. This
approach requires a detailed understanding of patient and operative risk to facilitate the most
appropriate use of scarce resources and to obtain the best postoperative outcomes.
Critical care does not solely occur on critical care units but can be achieved with a combination of
postoperative care units, step down units and outreach. Quality care does not mandate critical care but
can be achieved by a dedicated multidisciplinary care team starting from preoperative assessment
through quality recovery to a speedy return home.
When a high-risk surgical patient is cared for on a critical care unit the management strategy should be
proactive (preventing the onset of organ failure) rather than reactive (treating established organ
failures that might have been prevented). Improvement in outcomes of high-risk surgical patients is a
success story of modern critical care medicine.
This module assumes standard preoperative work up including clinical history and examination, routine
bloods, electrocardiogram for those with risk factors for or a history of cardiac disease, and chest X-ray
where appropriate.
You will find it helpful to read the following references before starting this module.
1/ HOW TO RECOGNISE THE HIGH-RISK SURGICAL PATIENT
Defining the high-risk surgical patient
Definition
The high-risk surgical patient can be defined as: An individual with a higher probability of suffering
excess morbidity and mortality following surgery as a result of co-morbid medical factors or the nature
of the surgical intervention itself or a combination of these.
Multidisciplinary approach and communication
Anaesthetic and surgical colleagues should identify high-risk surgical patients prior to surgery. It is
therefore essential that the critical care team be in close communication with their anaesthetic and
surgical colleagues in order to be aware of these surgical patients and to facilitate the planning of
postoperative care. Many high-risk patients undergoing elective surgery are identified in preoperative
assessment clinics, either by anaesthetists or trained nurse practitioners. A critical care consult can be
requested from such a screening clinic.
The PACT module on Communication skills contains a helpful section on communicating with
coworkers
.
Clinical identification of the high-risk surgical patient
History and examination
In addition to information about past episodes of surgery and anaesthesia, the patient history should
also be used to identify the presence and determine the severity of co-morbid medical factors and
intercurrent illness that may influence operative outcome (e.g. ischaemic heart disease (IHD), chronic
obstructive pulmonary disease (COPD), diabetes).
For those with risk factors for or a history of cardiac disease, initial history, examination and ECG
evaluation should focus on identification of potentially serious cardiac disorders, including:



Coronary artery disease e.g. prior myocardial infarction, angina pectoris
Congestive heart failure
Electrical instability e.g. symptomatic arrhythmias
For more information see the PACT module on Basic clinical examination
Specific risk factors
The following factors are associated with an increased risk of mortality and morbidity following surgery.
Patient factors
Age
Patient age tends to profoundly influence clinicians' preoperative perceptions of risk. However as an isolated
indicator of risk, chronological age should be treated with caution since it may be confounded by comorbidity which is more common in the elderly. Physiological age or physiological reserve may be more
useful concepts and cardiorespiratory reserve, in particular, is likely to be an important factor in determining
patient outcomes.
Pathophysiology and chronic illness/disease
The presence of systemic illness can lead to increased perioperative risk particularly where pathology
impacts upon cardiorespiratory function. Comorbid problems such as chronic obstructive pulmonary
disease, ischaemic heart disease and diabetes contribute to increased risk in an additive way (e.g. the
mortality associated with abdominal surgery more than doubles if the patient has chronic heart failure; see
Pedersen reference, below). It is important to quantify the nature and severity of these illnesses and to
recognise when specialist input from medical teams is required. The goal of these preoperative interventions
is to optimise the physiology of the patient prior to the onset of surgical stress.
A NECDOTE
A 54-year-old woman with exertional angina presented for elective hip replacement. She
needed appropriate diagnostic and interventional procedures.Investigation and management of
cardiac problems is independent of the need of surgery. If this patient were not having surgery
there would still need to be investigation and management of the exertional angina. Although
there is no demonstrated benefit from specific cardiac investigation and management in terms
of modifying outcome following elective surgery per se, it is considered prudent to delay
elective surgery in the majority of cases.
Surgical factors
Overall surgical mortality in Europe and the USA is thought to be less than 1% and for minor procedures in
healthy patients (e.g. day surgery) the mortality risk is extremely low. However, this masks the fact that for
certain procedures there is significant associated mortality and risk of perioperative complications.
General considerations
As a general rule, intra-cavity surgery is associated with poorer outcomes when compared with extra-cavity
procedures. Similarly, emergency surgery is associated with higher mortality and morbidity than scheduled,
elective work. In all of these cases prolonged surgical procedures with larger volumes of blood loss are, as to
be expected, associated with poorer outcomes.
Type of surgical procedure
For example, data from the United States suggest that carotid endarterectomy is associated with in-hospital
30-day mortality of between 1.5 and 1.7% while lower extremity bypass grafts exhibit mortality of 4.1 to
5.1% and mitral valve replacement is associated with figures as high as 15.1% (see Birkmeyer reference,
below). It is clearly important to recognise the risks specific to a given procedure and prepare appropriately.
Elective versus emergency procedures
Emergency procedures are associated with a higher operative mortality than elective procedures
(reference below). This is likely to be attributable to multiple factors including the acute physiology
associated with the emergency, surgical diagnosis and out-of-hours hospital infrastructure
considerations, for example pre and post surgical care, and the seniority of surgical and anaesthetic
staff.
Appropriate preoperative investigations
A range of invasive and non-invasive investigations may be available to the anaesthesiologist in the
preoperative period. It is important that these are appropriate and guided by the findings of history and
examination. It is important to understand the value, risks and benefits of each investigation and how
management will be altered in light of results. There is almost no evidence to support many of the
more sophisticated investigations that exist to stratify cardiac risk (e.g. thallium scan).
Preoperative testing should be limited to circumstances where the result will influence patient
treatment and outcome.
Assessment and initial management of cardiac risk
C OMMUNIC ATI ON
Assessment and initial management of cardiac risk in the perioperative
setting does not differ from management in the non-operative setting. A
number of guiding principles apply. Good communication between
anaesthesiologist, surgeon, critical care specialist and cardiologist is
essential. Indications for testing and treatment should be the same as those
outside the perioperative setting. Timing of tests and treatment will be
governed by the urgency of surgery, and by the estimated level of risk from
cardiac and non-cardiac causes.
Clearly no tests or preoperative cardiological interventions will be appropriate or possible on acute
presentation of ruptured aortic aneurysm whereas in less urgent cases appropriate management of
cardiac problems can be planned. The ECG, echocardiogram and exercise test are commonly helpful.
There is no evidence to support pre-emptive angioplasty or coronary artery surgery except where that
would have been indicated in the patient irrespective of their surgical condition and when there is no
urgency to the surgical problem.
N OTE
Coronary revascularisation before non-cardiac surgery to enable the patient to
get through the non-cardiac procedure is appropriate only for a small subset of
patients at very high-risk.
Assessment of exercise tolerance
Exercise tolerance is a key determinant of outcome following surgery. Patients who are able to perform
well (higher anaerobic threshold/VO2 max and absence of evidence of ischaemia) when challenged
physiologically by either an exercise challenge (bike/treadmill) have improved outcome (see Task 4 –
pathogenesis of perioperative morbidity
).
The patient history may be used to perform a rough estimate of exercise tolerance allowing the
anaesthesiologist to gain an indirect assessment of cardiorespiratory reserve. The limitations of such
an assessment tool should however be acknowledged. Questioning needs to be specific e.g. 'Did you
have to stop when walking from the car park to the entrance of the hospital?'
Practical clinical assessment of exercise tolerance can be achieved using a number of objective
systems although the ability of these methods to identify those who will be at risk in this situation has
not been formally tested.
Where available, formal cardiopulmonary exercise testing of patients prior to high-risk surgery can
provide very useful information. This technique has been shown to discriminate well between those at
high and low risk of mortality following major surgery (Older reference below). Physiological profiling
using a pulmonary artery flotation catheter can also be used for this purpose.
Scoring systems for surgical risk
Various methods are available for describing perioperative risk in patients. Simple categorical systems
(e.g. the American Society of Anesthesiologists Physical Status Score (ASA) score) are commonly and
easily used. Whilst they only discriminate very broadly between levels of risk they are useful for
'flagging up' patients who may require a higher level of care.
More complex scoring systems (e.g. the Physiological and Operative Score for enUmeration of
Mortality and Morbidity (POSSUM)) can provide rich datasets for comparison of outcomes between
individuals or institutions but are not currently commonly used in day-to-day practice. This type of data
could potentially be incorporated into clinical IT systems and used to provide clinicians with more
sophisticated information on a day-to-day basis. However, it is important to understand that whilst
these data can provide robust comparisons when populations of patients are studied they do not
provide precise estimates of risk at an individual patient level.
This means that they can be used to guide levels of care, for example elective postoperative critical
care, but a high-level of caution should be attached to making decisions about withholding care or
futility based on this type of information.
American Society of Anesthesiologists Physical Status Score
ASA score
This classification only describes physical status and does not take into account operative status. It is
quick and easy to use but there is a degree of subjectivity in allocation of scores. Increasing ASA score
is associated with worse outcome following surgery.
Patient examples
for Q1 to Q3
What are the ASA scores for each patient?
How would you rank the patients for surgical risk? Justify your answer
How much weight do you give in your assessment of risk to the patient's exercise tolerance?
The Physiological and Operative Score for enUmeration of Mortality and Morbidity
POSSUM is more complex to calculate and requires variables that may not be routinely collected in
lower risk patients. However, it is more sophisticated and enables comparison with benchmark
populations. Entry of the physiological and operative severity scores (tables below) into a regression
equation produces an expected event risk for that patient. Note that physiological component alone is
not predictive – the expected risk is only available after surgery when the operative severity score is
available.
POSSUM
physiological
score
POSSUM
operative severity
score
Raw mortality
Five surgeons (A-E) perform different types of surgery and therefore have a spectrum of risk profiles
for their patients and operations. Case-mix adjustment achieved by comparing observed and expected
mortality using the POSSUM system allows meaningful comparison of their data and demonstrates
that all are performing to a similar standard which is consistent with historical POSSUM data.
Case-mix adjusted
mortality
observed:expected Ratio
Source: Copeland et al. Br J
Surg 1995
For the next ten surgical patients you see, try calculating the surgical risk using the
POSSUM calculator from the following website.
http://www.edu.rcsed.ac.uk/lectures/lt1.htm
Discuss with your colleagues the utility of this score in assessment of patients prior to
surgery.
Assessing cardiac risk in non-cardiac surgery
Several scoring systems have been developed with the specific aim of evaluating cardiac risk in noncardiac surgery. Goldman (reference below) described a system based on assigning different
numerical scores to specific diagnoses and then summing the score for an individual to provide an
index of overall risk of cardiovascular complications.
This was subsequently developed by Detsky and then Lee (reference below) into the Revised Cardiac
Risk index. The revised index includes the following six independent predictors of cardiovascular
complications: high-risk type of surgery, ischaemic heart disease, history of congestive heart failure,
history of cerebrovascular disease, insulin therapy for diabetes, and preoperative serum creatinine
>177 µmol/l (>2.0 mg/dl). Patients are then placed into categories of increasing risk based on the
presence of 0, 1, 2 or ≥3 factors.
Clinical predictors of increased perioperative cardiovascular risk for non-cardiac surgery
The joint ACC/AHA guidelines for perioperative cardiovascular evaluation for non-cardiac surgery
divide patients into groups of low, intermediate and high levels of cardiovascular risk based on a set of
clinical predictors (see table below). These guidelines also include some useful recommendations for
additional preoperative investigations to further evaluate cardiovascular risk.
Clinical predictors of
increased perioperative
cardiovascular risk
ACC/AHA Guideline Update for Perioperative Cardiovascular Evaluation for Noncardiac Surgery 2002.
Full Text available from:
http://www.americanheart.org/ [Science & Professional/Library/Statements & Guidelines/ View
scientific statements by topic/ACC/AHA Joint Guidelines]
Scoring system summary
The ASA score is almost universally used in clinical practice and is a useful way of recording and
communicating risk between clinicians. Functional capacity based on exercise tolerance is important.
Subjective assessment of exercise tolerance is known to be unreliable so objective exercise testing
may be appropriate in those in whom it is not possible to be confident that exercise tolerance is good.
In those with cardiovascular risk factors, the ACC/AHA guidelines provide a useful framework for
perioperative cardiovascular evaluation.
More complex scoring systems such as POSSUM are capable of providing rich comparative audit data
about outcome following surgery but have limited utility in the day-to-day assessment of patients prior
to surgery.
T HINK
Screening by objective cardiorespiratory testing could potentially be used to allocate
scarce resources e.g. critical care beds.
Using the ten patients that you previously scored using the POSSUM system compare the
level of risk suggested using the ASA system and the ACC/AHA guidelines for
perioperative cardiovascular evaluation. How did the results obtained compare with your
initial clinical evaluation?
2/ HOW TO DESCRIBE PERIOPERATIVE COMPLICATIONS
Perioperative adverse outcome is common, and is frequently under-reported. No common system has
been widely adopted for describing morbidity or complications following surgery, making comparison
between surgeons, institutions or clinical trials difficult. On the critical care unit, established organ
failure scores can be used. On normal wards, the Postoperative Morbidity Survey (POMS) is the only
validated tool available.
Intra-operative complications
Pre-morbid state and the nature of surgery influence the likelihood of adverse intra-operative events.
These intra-operative events in turn contribute to postoperative outcome. Because of this they are
integral to scoring systems employed to compare postoperative outcomes. For example, the
Operative Severity Score (OSS) of the POSSUM system includes measures of perioperative blood
loss and intra-peritoneal soiling by gut contents.
Intra-operative complications influence both short-term operative outcomes and may also influence
long-term outcome. For example, intra-operative cardiac events seem to have an influence on
mortality for at least 12 months in high-risk surgical patients.
Postoperative complications
When efforts are made to actively identify and record complications following surgery it is clear that
postoperative complications are common following major surgery and are frequently under-reported in
routine practice. Placing patients in an environment which facilitates close supervision and monitoring
with a view to early recognition and treatment of complications is believed to result in improved overall
outcome following surgery.
Classically, postoperative events have been classified according to early, intermediate and late, based
on their timing relative to operation and local (directly related to the site of surgery) and general.
Although this approach has provided a common language for categorising complications it has not
aided understanding of pathogenesis.
Reporting of complications following surgery has been very variable, making comparisons between
studies and institutions very difficult. Reporting of postoperative complications has frequently focused
on specific adverse outcomes directly related to the conduct of the operation, for example the
breakdown of a bowel anastamosis.
It has long been recognised that many patients have multiple organ dysfunction following major
surgery (some progress to multiple organ failure) and this is well documented within the intensive care
environment using scoring systems such as the SOFA and SAPS (for further information, see the
PACT module on Clinical outcome
).
Outside of intensive care units many patients have prolonged hospital stay related to relatively 'minor'
organ dysfunction (from a critical care perspective) and this is commonly under-diagnosed. Attempts to
describe this phenomenon have been very limited and inconsistent, and interventions aimed at treating
or preventing these problems have the potential to significantly improve outcomes following surgery.
Early warning systems
Early identification and treatment of postoperative complications is aided by a proactive approach to
surveillance in postoperative patients. Critical care outreach staff have an important role to play in this
area. Surgical wards commonly have low staffing levels that are not consistent with adequate
surveillance for postoperative complications. The use of early warning criteria based on simple
physiological variables has become more common to facilitate identification of patients developing
postoperative complications. An example of a scoring system for identifying deteriorating patients is
the MEWS score. Its use is documented in the Goldhill reference on the next screen.
Patients identified to have complications should be aggressively managed by individuals with
appropriate knowledge and skills and it is therefore important that the critical care team is involved
early. An increase in level of care will almost always be appropriate. This can be achieved either by
moving the patient to a critical care unit (ICU, High Dependency Unit (HDU), Post Anaesthetic Care
Unit, or similar) or by bringing the environment to the patient by means of provision of augmented level
of monitoring and nursing care (ongoing outreach).
Operational definitions
An alternative approach to reporting postoperative morbidity is to use multifactorial systems of
assessment, which take into account both interventions and physiological scoring based upon
objective clinical observations. One example of such a system is the Postoperative Morbidity Survey
(see reference below); the only validated prospective system for describing short-term, postoperative
harm.
A NECDOTE
T HINK
A 79-year-old woman returned to a general, post-surgical ward following a total hip
replacement. She was prescribed two litres of normal saline over 24 hours as
postoperative fluid replacement and took no oral fluids because of nausea associated
with her patient-controlled analgesia. The house officer was finally called when she
was found to have been anuric for more than four hours. Review of the fluid balance
chart revealed a decreasing urine output over the preceding 12 hours. She required
admission to ICU for acute renal failure and eventually required renal replacement
therapy leading to a prolonged stay in the critical care setting. This admission was later
complicated by severe sepsis secondary to intravenous catheter colonisation.
Can you think of similar scenarios in which close observation, early recognition of a
postoperative complication and a simple clinical intervention (in this case appropriate
fluid management) may have successfully prevented adverse clinical outcome.
3/ HOW TO PREVENT/TREAT PERIOPERATIVE COMPLICATIONS
Two approaches are needed to reduce the incidence and impact of perioperative complications.
Firstly, prevention is vital and it is clear that a number of strategies are available which reduce mortality
and morbidity following surgery when used in the immediate perioperative period. Secondly, effective
treatment depends on early recognition (see Task 2) and appropriate management of specific
morbidities.
Preventive strategies can be divided into those that have been shown in clinical trials to reduce the
mortality and morbidity following surgery and those that have been shown to reduce the level of
specific morbidities following surgery.
Only two strategies of perioperative care, haemodynamic goal-directed therapy and β-adrenoreceptor
blockade, are claimed to reduce both mortality and morbidity following surgery and these will be
discussed later in this module.
An additional group of interventions that have been shown to improve outcome in other aspects of
critical care may also provide benefit in the perioperative setting. Some clinicians extrapolate from
these critical care studies and allow them to guide their perioperative practice. These interventions
await formal evaluation in the perioperative setting.
Interventions influencing specific morbidities
Interventions that have been demonstrated in randomised controlled trials to reduce the level of
specific postoperative morbidities in surgical patients:
Maintenance of normothermia has been shown to reduce wound infection rates and shorten length
of hospital stay.
Thromboembolic prophylaxis has been shown to reduce the incidence of deep vein thrombosis
(DVT) and pulmonary embolism (PE) following surgery.
Maintenance of good oxygenation has been shown to reduce wound infection rates and nausea and
vomiting.
Early enteral feeding following gastrointestinal surgery, either orally or directly into the small bowel,
reduced infectious complications and length of stay when compared with a 'nil by mouth' strategy.
Choice of resuscitation fluid
Although the crystalloid colloid debate is still unresolved (large RCTs are currently underway), the
electrolyte composition of the solution seems to have an effect on outcome. Use of isotonic saline
(0.9% NaCl solution) or of colloid solutions dissolved in isotonic saline appears to result in
increased metabolic acidosis, decreased urine output/renal function and increased coagulopathy when
compared with more physiologically balanced solutions such as Hartmann's solution.
Prophylactic antibiotics administered pre-emptively reduce infection rates but there is no evidence of
any benefit of further doses beyond the first postoperative day. Commencing antibiotics before the
immediate preoperative period provides no benefit. High dose regimens are no better than standard
dosage.
Haemodynamic goal-directed therapy and β-adrenoreceptor blockade are discussed below.
A multimodal approach incorporating many of the elements listed above coupled with careful
preoperative preparation, regional analgesia, early removal of nasogastric and urinary catheters and
early mobilisation has been shown to be beneficial in colo-rectal surgery and this type of approach is
likely to become more common in other types of surgery.
Other interventions
Certain interventions that have been demonstrated in randomised controlled trials to influence mortality
or morbidity in other patient groups that may be of benefit in high-risk surgical patients:
Transfusion triggers
There is evidence that wound infection rates and tumour recurrence rates are increased following
transfusion of autologous blood. Although perioperative data are sparse, the current recommendation
(based on clinical trial data from the ICU setting) is a transfusion trigger when the haemoglobin level is
7 g/dl (4.4 mmol/l). However patients with known cardiac disease or significant risk factors for cardiac
disease were not included in this study. The introduction of leukodepletion and improved storage
methods for red cells make translation of these data into current practice difficult. New data in this area
are awaited. Although a transfusion trigger of 7 g/dl (4.4 mmol/l) is commonly accepted, it is important
to consider this in the context of other risk factors.
Glycaemic control Tight control of blood sugar levels has been demonstrated in a randomised
controlled trial to reduce mortality on the ICU. The patient population in this study were predominantly
postoperative. These patients received both insulin and glucose with K+ supplementation where
necessary.
A 69-year-old man with insulin-dependent diabetes mellitus, hypercholesterolaemia, and mild
congestive cardiac failure is listed for an emergency laparotomy for peritonitis. There is no time for
investigation of his cardiac status beyond ECG and he is taken to theatre immediately. What
perioperative interventions are needed to reduce cardiac risk?
N OTE
Optimal perioperative management will reduce cardiac risk as much as possible.
Goal-directed therapy
Maximising DO2 improves outcome
The mortality associated with major surgery can be substantially reduced by prior optimisation of
circulating volume and adjunctive inotropic agents to improve cardiac output and systemic oxygen
supply. Pooling results of the studies discussed above in a meta-analysis can provide additional
information about different approaches to this strategy. Commencement of therapy in the preoperative
phase, intra-operatively or up to six hours postoperatively seems to provide benefit. However, a study
of fixed dose inodilator therapy perioperatively failed to show benefit in the intervention group. A
variety of types of cardiac output monitor (pulmonary artery catheter, oesophageal Doppler
velocimetry, pulse contour-based technology) have been used effectively to achieve similar results.
Similar benefits have been obtained in patients presenting to an emergency department with severe
sepsis or septic shock. Benefits are more likely to be realised the earlier optimisation is applied, and if
the control group has a high mortality risk. However, not all research supports this approach.
Earlier work in patients with established septic shock found either no benefit or an adverse effect from
use of high dose dobutamine infusions to achieve oxygen delivery goals (see references below for
further details).
T HINK
Discuss the possible reasons for the divergences noted above with your colleagues
when you next care for high-risk patients presenting for surgery or in the early phase of
severe sepsis.
Is placement of a pulmonary artery catheter mandatory?
Fundamental to the process of maximising oxygen delivery, cardiac output or global blood flow is the
measurement of a variable reflecting blood flow and titration of therapy to this variable. The majority of
studies in this area have used thermodilution through a pulmonary artery flotation catheter (PAFC) to
measure cardiac output. The Canadian Critical Care Clinical Trials Group, however, did not
demonstrate improvements in outcome with the use of pulmonary artery catheters in high-risk surgical
patients. Published studies have also used heating coil-based 'continuous' cardiac output monitoring
techniques (via a PAFC), oesophageal Doppler monitoring (ODM) of stroke volume and pulse contour
analysis of arterial wave forms to guide perioperative haemodynamic management. While there is still
a role for the PAFC there is increasing interest in less invasive techniques.
Fluid challenge
The core intervention in perioperative goal-directed studies has been adequate fluid therapy. The
optimal strategy for fluid administration is to use a fluid challenge- based regimen. The response of the
cardiac output or stroke volume (or CVP if blood flow monitoring is not utilised) to a small increment of
intravascular volume expansion (colloid bolus) is used to guide further fluid therapy.
Fluid challenge
If the cardiac output or stroke volume increase in response to a fluid challenge, the cardiac filling curve
(Starling curve), is on the ascending slope of its compliance curve (A, in figure), further fluid challenges
are appropriate. If there is no increase in the flow parameter in response to a fluid challenge (B) this
suggests that further fluid challenges would not lead to further increases in flow. A fall in flow in
response to a fluid challenge
(C) suggests that the intravascular space is becoming overfilled and cardiac efficiency is decreasing
with increased filling, therefore no further fluid should be given at that time.
Perfusion guided therapy
Studies using monitors of tissue perfusion to guide fluid therapy (e.g. gastric tonometry guided
therapy) have so far failed to show benefit from this strategy.
Beta-adrenoreceptor blockade
Several studies have suggested that the use of perioperative β-blockade in patients with risk factors for
ischaemic cardiac disease reduces the incidence of postoperative cardiac events and mortality from
cardiac causes. However, a recent systematic review and meta-analysis concluded that although this
area looks promising there is currently an insufficient evidence base to recommend this for all patients.
Retrospective analysis of large clinical databases supports the notion that patients at high risk of
cardiac complications receive some benefit, but that for lower risk patients there is no benefit and
possibly even harm from perioperative β-blockade.
It is also known that withdrawing long standing β-blockade preoperatively increases the risk of
perioperative adverse cardiac events.
Care environment
The care environment is an essential element of postoperative management. Rational use of
resources is also very important. Sending someone to a critical care environment for HDU care is an
appropriate use of resources, however sometimes surgery needs to proceed in the absence of the
necessary beds. In these circumstances it is important to be resourceful e.g. 24-hour recovery,
outreach. Perfect intra-operative management is not on its own adequate but needs to be continued
into the postoperative phase.
A NECDOTE
A 44-year-old male presented with faecal peritonitis requiring urgent laparotomy. He
was rapidly transferred to the operating suite and fluid resuscitated via peripheral
cannulae whilst central venous, arterial and pulmonary artery catheters were placed.
Oxygen delivey goals (per Shoemaker) were adopted perioperatively and he had a
prolonged recovery for six hours in a postoperative care unit. He was transferred to the
postoperative ward where blood gases were regularly monitored and fluid resuscitation
was continued along with all routine intra-operative care (e.g. normothermia, adequate
oxygenation). All abnormal metabolic variables were normalised overnight and he had
a successful outcome returning home within seven days.
Increasing global blood flow to specific goals has been shown to improve outcome in which of the
following groups of patients: cardiac surgery, fractured neck of femur, trauma, major general
surgery?
How may goal-directed therapy and β-blockade interact?
The relative places of goal-directed therapy often involving adrenergic drugs to maximise global blood
flow, and β-blockade to diminish adrenergic activity, are not clearly defined. Although β-blockade
appears to reduce postoperative mortality this is in a small selected group of patients with multiple risk
factors for ischaemic cardiac disease. However, there is also data to support the use of goal-directed
augmentation of global blood flow in this same patient group. It may be that the limitation of the cardiac
response to hypovolaemia imposed by β-adrenergic blockade results in increased administration of
fluids and improved tissue perfusion. At present there is insufficient data to provide firm
recommendations in this area.
N OTE
In general the continuation of preoperative cardiac medications is recommended
although some clinicians recommend omitting ACE inhibitor therapy. Betaadrenoreceptor blockers should not be omitted unless there is a specific clinical
reason to do so (see above).
CAUTION! Stopping β-blockers in a patient who is already taking them is likely to be deleterious for
them.
4/ UNDERSTANDING PERIOPERATIVE PATHOPHYSIOLOGY
There are three pathological processes contributing to perioperative morbidity and mortality.



Myocardial ischaemia leading to an increased risk of arrhythmia, infarction and cardiac
failure.
Hypovolaemia leading to inadequate tissue perfusion and subsequent organ dysfunction
due to hypoxic damage or ischaemia reperfusion injury.
Impaired cardiorespiratory performance and inability to respond to the increased demands
associated with surgery.
Although specific interventions exist which appear to reduce the incidence of perioperative adverse
cardiac events (e.g. β-adrenergic blockade), the risk of cardiac ischaemia or infarction perioperatively
can be reduced by attention to the following aspects of good anaesthetic practice.
Maintenance of stable haemodynamics
Hypotension may result in inadequate perfusion pressure across critical coronary stenoses leading to
ischaemia or infarction. Hypertension causes increased myocardial work leading to ischaemia due to
increased oxygen demand.
Fluid balance
Avoidance of hypovolaemia reduces sympathetic outflow and ensures an adequate circulating volume
available to perfuse the myocardium. Maintenance of adequate tissue perfusion to other tissues (e.g.
gastrointestinal tract) also avoids the proinflammatory effects of hypoperfusion and ischaemiareperfusion.
Adequate pain control
Minimising the sympathetic response to surgical stimulus and postoperative pain reduces tachycardia
and cardiac work which in turn reduces the risk of ischaemia.
Myocardial ischaemia
N OTE
If myocardial oxygen demand persistently exceeds supply, ischaemia will arise.
Myocardial ischaemia can in turn cause arrhythmia, infarction and cardiac
failure.
Hypothermia is associated with catecholamine release and has been shown to increase the incidence
of perioperative ischaemia in susceptible individuals. Maintenance of adequate oxygenation is clearly
also essential to maintain an adequate supply of oxygen to the myocardium.
The factors below predispose to perioperative myocardial ischaemia and should be avoided.
Perioperative β-blockers may reduce the myocardial ischaemia in patients with ischaemic heart
disease. For more information see the PACT module on Acute myocardial ischaemia
Factors that increase myocardial oxygen demand:




Tachycardia increases myocardial demand due to increased rate of work. Also contributes
to ischaemia because the period of diastole, during which most coronary flow occurs, is
reduced.
Shivering increases oxygen demand due to the increase in mechanical work performed by
skeletal muscle.Systemic Inflammatory Response Syndrome (SIRS)
Sepsis and the accompanying inflammatory response lead to hyperdynamic circulation
characterised by high cardiac output, tachycardia, low systemic vascular resistance and low
mean arterial and diastolic pressures. All of these may contribute to myocardial ischaemia.
Magnitude of tissue injury – Prolonged, extensive surgery is associated with greater
tissue damage which results in a greater oxygen demand associated with tissue healing
and the associated inflammatory insult.


Endogenous catecholamines – An increase in the circulating levels of endogenous
catecholamines may be caused by pain or anxiety in the postoperative period. The
associated increase in sympathetic activation leads to positive chronotropy and inotropy
and hence further myocardial ischaemia.
Exogenous catecholamines – Inotropic support may be necessary perioperatively. When
used appropriately, exogenous catecholamines may improve oxygen delivery. They may,
however, also contribute to myocardial ischaemia through the same mechanisms as
endogenous catecholamines.
Factors that reduce myocardial oxygen supply:



Hypoxaemia – Inadequate ventilation and oxygenation will lead to hypoxaemia, reducing
the oxygen content of blood and hence myocardial oxygen
supply.AnaemiaHypotensionCritical coronary stenoses
Endogenous vasoconstrictors – Increased sympathetic activation
o Pain
o Anxiety
Exogenous vasoconstrictors
o Vasopressors
Which risk factors, in a patient's history and routine investigations, would you rate as most
important as predictors of increased perioperative cardiovascular risk (myocardial infarction,
congestive heart failure, death)?
When are patients at highest risk of postoperative cardiac events?
Hypovolaemia and reduced tissue perfusion
N OTE
Although cardiac risk factors have traditionally attracted much attention,
hypovolaemia is both common and AVOIDABLE.
Hypovolaemia is the commonest avoidable cause of perioperative morbidity. Commonly measured
cardiovascular variables (heart rate, blood pressure and arterial and venous pressures) are a poor
guide to intravascular volume status. Perioperative compensated hypovolaemia is common and underrecognised. The reduced intravascular volume results in redistribution of blood flow away from 'nonvital' organs resulting in reduced tissue perfusion. Reduced tissue perfusion may cause tissue hypoxia,
leading to impairment of function and, for example, gut leak, and ischaemia reperfusion injury and
resulting in inflammatory activation.
Subsequent development of SIRS and multiple organ dysfunction syndrome (MODS) is dependent
upon the magnitude and duration of the tissue hypoperfusion compounded by other pro-inflammatory
insults (e.g. trauma, infection). It is increasingly recognised that there is a highly variable interindividual response to pro-inflammatory stimuli which is probably, to a large part, genetically
determined.
Cardiorespiratory performance
The maintenance of tissue oxygenation during surgery is largely determined by the capacity of the
cardiorespiratory system to meet the increased demands of the tissues. Pre-existing coronary artery
disease is a major determinant of the likelihood of developing myocardial ischaemia but not
necessarily reduced cardiac performance. However, pre-existing cardiac failure or functional
impairment such that the increased demands of the tissues for oxygen delivery during surgery cannot
be met will result in tissue hypoxia and poor outcome. An understanding of the factors in individual
patients and the appropriate targeting of therapies to minimise risk of ischaemia whilst maximising
oxygen delivery is the key to success.
DO2 level predicts poor outcome
The association between perioperative cardiac output and survival following major surgery was first
noted in the 1950s: survivors having higher cardiac output values than non-survivors. From these
observations the hypothesis developed that using the cardiac output and oxygen delivery values
exhibited by the survivors, as goals for all patients, would reduce overall mortality.
Indices of poor tissue perfusion also predict poor outcome
Poor global perfusion, suggested by an increase in plasma lactate and the acute development of a
metabolic acidosis, or impaired regional perfusion, suggested by, for example, elevated intragastric
CO2measured using a gastric tonometer, are associated with adverse outcome following surgery.
Explain which patient is at greater risk of worse perioperative outcome: a 48-year-old who can
walk one mile on the flat but has ischaemic changes on exercise testing or a 47-year-old with an
exercise tolerance of 20 metres but no evidence of ischaemia on ECG?
T HINK
There is an apparent conflict between pushing harder to sustain tissue perfusion in the
face of a major inflammatory insult and reducing myocardial oxygen demand by βblockade.
5/ OUTCOME FOLLOWING SURGERY
Meaningful data on outcome following surgery are hard to find. No single unified European data set
exists and national data collection is unusual. The available data suggest that there are marked
variations between countries and it is probable that these are at least in part resource related. A
comparison of patient outcomes from two hospitals, one in the United States and one in the United
Kingdom, found very different outcomes between the two groups.
Mortality related to surgery can occur for a considerable period after the surgical procedure itself.
Many of the patients who die do so in the first few days following surgery from complications directly
attributable to the operation. However, a significant proportion die many days and weeks post surgery
following prolonged multiple organ dysfunction/failure related to the initial inflammatory insult at the
time of operation. See figure 1.2 Calendar days from operation to death in the following reference.
Mortality recording is relatively straightforward but these data alone provide only a limited amount of
information regarding the quality of postoperative outcomes; indeed many patients who survive
surgery experience significant morbidity associated with prolonged hospital stays. Morbidity occurring
after surgery is commonly under-reported. When it is systematically looked for and described it
appears to occur very commonly. This morbidity impacts the patients' postoperative quality of life and
inflicts further demands on health service resources. In view of this, an accurate method for recording
the nature and extent of postoperative morbidity is clearly desirable; however, to date no validated
method capable of achieving this exists.
Find out what information is available preoperatively from the potential high-risk
patients, and how could you track their postoperative outcomes (e.g. morbidity, inhospital mortality, readmissions).
T HINK
Preoperative recognition of high-risk patients and therapeutic interventions to improve
their outcome requires close multidisciplinary collaboration. Whom should you involve
in your hospital if a clinical pathway in the pre-, peri-, and postoperative phases were
to be established for the high-risk surgical patients? What requirements would this
impose for the patient care process and infrastructure (e.g. ICU or recovery room,
staffing in anaesthesia or ICU)?
CONCLUSION
Management of the high-risk surgical patient requires careful preoperative assessment in order to
accurately define the overall risk level and identify specific risk for particular patients and types of
surgery. Several systems for scoring risk can be used and objective measurement of exercise capacity
is valuable.
Perioperative management should be guided by the preoperative assessment. A number of
management styles are known to improve outcome and, in particular, fluid management is important.
There is some evidence that an augmented level of postoperative care is associated with improved
outcome. This can be achieved by admission to a critical care unit, to a high dependency or overnight
recovery facility or by an intensive multidisciplinary approach on a surgical ward (critical care without
walls).
Measurement of outcome following surgery, including systematic recording of morbidity, is likely to
drive change and improve outcomes by highlighting best practice and drawing attention to shortfalls in
care.
Improvement in outcomes of high-risk surgical patients is a success story of modern critical care
medicine.
PATIENT CHALLENGES
A 76-year-old lady is admitted to your hospital for an elective left hemi-colectomy for carcinoma of the
colon. You are the ICU resident on-call. The anaesthesiologist who sees the patient prior to surgery calls you
and requests an intensive care bed postoperatively. She tells you that the lady is fit and well, ASA I and
walks her cocker spaniel two miles every day. Routine blood tests, chest radiograph and electrocardiogram
are normal. There are no specific anaesthetic risks. Hb 9.8 g/dl.
Learning issues
Clinical investigation of the high-risk surgical patient
Scoring systems for surgical risk
Is this high-risk surgery? Give reasons.
Learning issues
ASA I
Good exercise tolerance
High-risk surgery
How would you prepare the patient for the operation?
Learning issues
Optimum intra-operative factors
Interventions influencing specific morbidities/maintenance of normothermia
No ICU or High Dependency Unit (HDU) bed is available but the surgeon and anaesthesiologist decide to
proceed with surgery, with a plan to admit the patient to the 24-hour recovery unit postoperatively. A lumbar
epidural is inserted prior to surgery, general anaesthesia induced and a radial arterial line and central venous
catheter inserted for invasive pressure monitoring.
During the surgery there is some technically difficult dissection. The operation takes three and a half hours
and the total blood loss is 1.6 litres. On two occasions during the operation the blood pressure is noted to be
labile but the systolic pressure never falls below 80 mmHg. Total intra-operative fluid administered: 5 litres
of lactated Ringer's solution, 3.5 litres of succinylated gelatine and 4 units of packed red cells.
Learning issues
Care environment
Intra-operative complications
On arrival in recovery the patient is breathing spontaneously post extubation with an SaO2 of 95% on an
FiO2 of 35% via a variable performance face mask. Her routine cardiorespiratory observations are normal
(heart rate 90 bpm, blood pressure 110/75 mmHg, respiratory rate 18/min) but she has a temperature
(tympanic) of 35.1 °C and is shivering intermittently. Urine output is 55 ml per hour. Arterial blood gas
analysis is as follows: pH 7.3, ABE – 6.2, PaCO2 5.6 kPa (42 mmHg), HCO3 â?? 20 mmol/l, PaO2 is 12.1
kPa (91 mmHg), Hb is 10 g/dl.
Learning issues
PACT module on Basic clinical examination
How do you interpret these results and what do you conclude?
Learning issues
PACT module on Homeostasis
PACT module on Respiratory failure
What components of perioperative care can be improved in this patient?
Learning issues
Pathogenesis of postoperative organ dysfunction/hypovolaemia and reduced tissue perfusion
Maximising DO2 improves outcome
Maintenance of normothermia
Outcome
After six hours in recovery and additional treatment including fluid challenges and active surface warming,
the temperature has returned to normal and the metabolic acidosis has completely resolved. You discuss
with your colleagues the return of the patient to the general surgical ward.
Do you think she should be allowed to go to the ward? Give reasons.
Learning issues
Care environment
Given the critical care referral is there any further assistance the intensive care service can
offer?
Learning issues
Critical care outreach
The lady returns to the general surgical ward. Two days later she is nauseated and still not tolerating any oral
input. Her temperature is noted to have risen to 38.3 °C and the urine output has fallen to 15-20 ml per hour.
Heart rate 105 bpm, blood pressure 110/70 mmHg. Blood cultures are taken, antibiotics commenced and 500
ml of colloid solution are administered by the on-call surgical resident. You are called to the ward to discuss
the patientâ??s clinical deterioration. You think she may have sepsis.
Learning issues
PACT module on Sepsis and MODS
What pathological processes are taking place?
Learning issues
Sepsis and MODS
PACT module on Sepsis and MODS
What is the appropriate management?
What measures would you take to provide the necessary and optimum organ support
necessary?
Learning issues
PACT module on Homeostasis
PACT module on Acute renal failure
PACT module on Mechanical ventilation
No ICU bed is available until the following morning. On admission the patient is hypotensive and
tachycardic with increased respiratory rate, SaO2 89% on 60% FiO2, and vomiting. She has a 39 day stay
with resistant infections, prolonged mechanical ventilation for ARDS, makes a slow recovery and is
discharged home after 54 days.
Learning
issues
Outcome
N OTE
Prevention is better than cure
An 84-year-old man is admitted to the Accident and Emergency department with a fractured left neck
of femur. He has a history of ischaemic heart disease and is taking atenolol, isosorbide dinitrate and aspirin.
He gets short of breath on climbing more than one flight of stairs. He is in pain, tachycardic (heart rate
120/min) and anaemic (Hb 8.5 g/dl) with a normal blood pressure but cool peripheries. The 12-lead ECG
shows ST depression in the inferior leads.
Learning issues
PACT module on Acute myocardial ischaemia
PACT module on Heart failure
PACT module on Arrhythmia
What immediate measures are indicated?
Is this high-risk surgery? Explain your answer.
Learning issues
Specific risk factors
Myocardial ischaemia
Following provision of adequate pain relief, intravenous fluids including some blood and oxygen therapy,
the ST depression has resolved. The patient is referred to your intensive care unit.
Should he be admitted to the intensive care unit for 'preoptimisation'? Give your reasons.
Learning issues
Care environment
PACT module on Basic clinical examination
Should his cardiac medicines be continued during and after the operation? Give reasons.
Learning issues
Beta-adrenoreceptor blockade
The patient is reviewed by the anaesthesiologist who offers epidural pain relief. This was declined by the
patient. The anaesthesiologist makes a plan to use general anaesthesia and operate as soon as possible.
What type of perioperative monitoring is appropriate? Why?
Learning issues
Cardiac output measurement devices
Maximising DO2 improves outcome
The patient is continued on all preoperative cardiac medicines. Invasive arterial monitoring is inserted under
local anaesthetic prior to induction of anaesthesia that is induced using a balanced technique with minimal
haemodynamic disturbance. An oesophageal Doppler probe is inserted and stroke volume maximised using
an established algorithm. The stroke volume increased by 20% from start to finish of surgery, without any
evidence of myocardial ischaemia. The operation is completed without any haemodynamic instability or
ischaemia being recorded. On admission to the high dependency unit after surgery he is extubated, breathing
spontaneously with entirely normal cardiorespiratory profile.
How long would you plan to keep him on the HDU?
The patient was maintained on the HDU for 24 hours and reviewed by the cardiology team before being
transferred to a step-down unit for a further two days where he continued to have ECG and SaO2 monitoring
in addition to his regular observations. He was reviewed regularly by the outreach team who were called to
see him on three separate occasions for two episodes of ischaemia and one transient episode of atrial
fibrillation, all of which responded to simple measures. He left hospital on day 10 having been reviewed by
the cardiology team who arranged out-patient follow-up.
Learning issues
Myocardial ischaemia
PACT module on Acute myocardial ischaemia
PACT module on Heart failure
PACT module on Arrhythmia
Outcome
On reflection, proactive use of critical care to prevent predictable sequelae of high-risk major surgery is a
more appropriate use of resources than reactive care of preventable problems. There is an apparent dilemma
offered by the evidence favouring on the one hand perioperative β-agonist infusion and on the other
favouring perioperative β-blockade.
What are your views regarding the delays in admission of the first patient to the ICU?
Learning issues
PACT module on Transportation
Do you think the second patient should have been maintained on the HDU for longer?
From this account what conclusions have you come to about the utility of intensive care following
high-risk surgery?
Q1. Risk factors for major cardiac events following non-cardiac surgery include:
A. Smoking
True
False
B. Type II diabetes mellitus
True
False
C. Heart failure
True
False
D. Unstable angina
True
False
E. Abnormal ECG
True
False
Q2. The following methods of monitoring cardiac output have been used in randomised controlled trials of
goal-directed therapy in the perioperative period
A. Pulse contour analysis
True
False
B. Bolus thermodilution using a pulmonary artery catheter
True
False
C. Transoesophageal echocardiography
True
False
D. Thoracic bioimpedance
True
False
E. Oesophageal Doppler aortic velocimetry
True
False
Q3. Outcome following major surgery has been demonstrated in a randomised controlled trial to be
improved by:
A. Maintenance of a haemoglobin level of >10 g/dl (6 mmol/l)
True
False
B. Maintenance of tight glycaemic control during surgery
True
False
C. Maximising oxygen delivery
True
False
D. Beta-blockade of patients undergoing surgery for repair of fractured neck of
femur
True
False
E. Beta-blockade of patients with a positive dobutamine stress test undergoing
major vascular surgery
True
False
A. Normal blood pressure
True
False
B. Normal arterial pH
True
False
C. Normal lactate
True
False
D. Urine output >1 ml/kgZ-1
True
False
E. Cardiac index >3 l/min-1
True
False
A. Activated protein C
True
False
B. Beta-adrenoreceptor blockade
True
False
C. Angioplasty of critical coronary stenoses
True
False
D. Surgical revascularisation of critical coronary stenoses
True
False
E. Intra-operative thrombolysis
True
False
Q4. The following exclude clinically significant hypovolaemia
Q5. Cardiac outcome following non-cardiac surgery is improved by: