Conservative Oxygen Therapy
Mr Glenn Eastwood, Dr Satoshi Suzuki, Ms Leah Peck, Dr Neil Glassford, Prof Rinaldo Bellomo
Department of Intensive Care
Austin Hospital
Melbourne, Victoria
Australia
Massabuau, Mech Ageing Dev 124: 857‐863, 2003
Oxygen is given liberally in ICU and ED
• In emergencies O2 is given to achieve SpO2 100%
• In ICU SpO2 >96% are regularly targeted
• This means that lots more oxygen is given that may be desirable
• Excess oxygen excess can exacerbate lung injury, decrease cardiac output, generate free radicals in various organs and cost money
Is post cardiac arrest oxygenation bad?
• Avoiding further hypoxia seems desirable
• However, avoiding hyperoxia may be equally important
• Hyperoxia may increase cerebral radical oxygen species formation
• Cerebral radical oxygen species formation may worsen neurological damage
Current recommendations following cardiac arrest
• Current American Heart Association guidelines: 100% FiO2 during resuscitation. However ‐ such high FiO2 is often maintained for some time thereafter potentially exposing the patient to greater risk of cerebral ROS‐ mediated injury
• Recent consensus statement by ILCOR advocates avoiding unnecessary hyperoxia and delivering a controlled re‐oxygenation strategy targeting an arterial oxygen saturation not exceeding 94‐96%.
NB: No APACHE scores available
Oxygen therapy in other situations?
What should be the target SpO2 in ICU?
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Do we need a SpO2 >96%?
If not, do we need a SpO2 >94%?
If not, do we need a SpO2 >92%?
If not, do we need a SpO2 >90%?
• Where does the risk/benefit ratio change in favour of giving oxygen?
• Would we accept a study of lower SpO2 targeting (Conservative O2 therapy)?
Observational study
• Single‐centre observational cohort study
• Aim to describe current oxygen administration practices for mechanically ventilated patients
• Collected FiO2, PaO2 and SpO2 every 6‐hours
• Excess oxygen defined as a PaO2 >120 mmHg
• Findings
– 358 mechanical ventilation days in 51 patients
– Most patients spent most of their time with
• SpO2 >98%
• PaO2 80‐120 mmHg
– 50% of observations were hyperoxaemic
• Conclusion
– Excess oxygen delivery and liberal oxygen therapy were common in mechanically ventilated patients
Conservative oxygen therapy
• All patients expected to be on mechanical ventilation until day after tomorrow
• Observe current practice, identify such patients and do nothing different
• Except perform…”Conservative oxygen therapy”
Protocol
Step 1: For mechanical ventilated adult patients
Step 2: Expected to stay ventilated until the day after tomorrow
Step 3: Target SpO2 90‐92%
Outcomes
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Separation: how big a difference in PaO2
Therapy: how big a difference in FiO2
Efficacy: Change in PaO2/FiO2 over time
Safety: Delirium, kidney function, arrhythmias
Feasibility: will nurses/doctors do it
1st patient 1st day
PSV
FiO2
PaO2
Patient
‐ 42 female
‐ Acute hepatic failure
‐ Propofol & Noradrenaline
‐ 10% Saline & 10% Dextrose for hyponatraemia
‐ CVVHDF
‐ PiCCO monitoring
‐ CO2 monitored
Preliminary results
• Oxygen related outcomes
– FiO2
– PaO2
– SpO2
• Clinicians’ response to conservative oxygen therapy
FiO2
0.6
0.55
0.5
FiO2
0.45
0.4
Liberal
0.35
Conservative
0.3
0.25
0.2
1
2
3
4
Time (days)
5
6
7
PaO2
160
150
140
Pa02 (mmHg)
130
120
110
Liberal
100
Conservative
90
80
70
60
1
2
3
4
Time (days)
5
6
7
SpO2
100
99
SpO2 (%)
98
97
Liberal
Conservative
96
95
94
1
2
3
4
Time (days)
5
6
7
Clinicians’ responses
• 87 respondents (78 nurses/9 doctors)
• 63% considered oxygen related lung injury to be “a major concern”
• 90% felt conservative oxygen therapy was easy to perform
Clinicians’ responses (cont.)
• 93% did not find implementing conservative oxygen therapy stressful
• 85% reported they did not performed more arterial blood gases
• 91% felt that we should continue performing conservative oxygen therapy
From here…
• Continue conservative oxygen therapy at the Austin Hospital Intensive Care Unit
• Encourage further evaluation of oxygen therapy, its management and possible impact on outcome for mechanically ventilated patients
• Future interventional studies warranted
– Conservative or Liberal Oxygen Targets Safety and Evaluation In Mechanically Ventilated Patients – a Pilot Feasibility Study (CLOSE I)
Investigators: Panwar, Harrigan, Hardie, Young, Capellier, Bellomo
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For further information please contact
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Glenn Eastwood
ICU Research manager
Austin Health
[email protected]