Letters to the Editor
REFERENCES
1. Sluga M, Ummenhofer W, Studer W, et al.
Rocuronium versus succinylcholine for
rapid sequence induction of anesthesia
and endotracheal intubation: a prospective, randomized trial in emergent cases.
Anesth Analg 2005;101:1356 – 61.
2. Pardo C, Chamorro C, Romera MA, et al.
Succinil-colina ¿bloqueante neuromuscular
de elección para la intubación de pacientes
crı́ticos? Med Intensiva 2001;25(Suppl 1):89.
3. Tryba M, Zhorn A, Thole H, Zenz M.
Rapid-sequence oro-tracheal intubation
with rocuronium: a randomized doubleblind comparison with suxamethonium,
preliminary communication. Eur J Anaesthesiol 1994;11(suppl 9):44 – 8.
4. Chamorro C, Martinez-Melgar JL, Romera MA, et al. Uso de rocuronio en la
secuencia rápida de inducción-intubación
de los pacientes crı́ticos. Med Intensiva
2000;24:253– 6.
5. Booij LH. Is succinylcholine appropriate
or obsolete in the intensive care unit? Crit
Care 2001;5:245– 6.
DOI: 10.1213/01.ANE.0000215219.94506.0B
Tube Design for
Nasotracheal Intubation
To the Editor:
Various methods have been advocated to prevent trauma from nasotracheal intubation (1,2), including a
recent trial by Lee et al. (3) comparing the influence of two different tip
designs on nasal trauma. In this
study, the authors demonstrated that
softening the tube with warm saline
reduced the risk of epistaxis.
However, thermosoftening a
polyvinyl chloride tube can lead to
its distortion and obstruction, particularly at the tube’s weakest point
where the inflation lumen opens into the cuff (4 – 6). Thus routine use
of thermosoftening cannot be
recommended.
Lee et al. suggest that the Magill
tip is better suited to nasotracheal
intubation under direct vision. The
use of a Magill tip may also ease the
passage of the endotracheal tube into
the trachea when a fiberoptic bronchoscope is used, as the tip of the
bronchoscope can inadvertently be
placed through the eye of a Murphy
tip, making it impossible to advance
the tube into the trachea (7,8). If retrograde nasotracheal intubation is intended using a “pulling thread technique,” the use of a Murphy tip tube
254
Letters to the Editor
is necessary, so that the thread can be
secured to the tip of the endotracheal
tube at the Murphy eye (9,10).
Rajesh Mahajan
Rahul Gupta
Anju Sharma
Department of Anaesthesia
ASCOMS
Jammu, J&K, India
[email protected]
REFERENCES
1. Mahajan R, Gupta R, Sharma A. Another
method to avoid trauma during nasotracheal
intubation.
Anesth
Analg
2005;101:928 –9.
2. Elwood T, Stallions DM, Woo DW, Bradford HM. Nasotracheal intubation: a randomized trial of two methods. Anesthesiology 2002;96:51–3.
3. Lee JH, Kim CH, Bahk JH, Park KS. The
influence of endotracheal tube tip design
on nasal trauma during nasotracheal intubation: Magill-tip versus Murphy-tip.
Anesth Analg 2005;101:1226 –9.
4. Aggarwal A. Warming the tracheal tube
and kinking. Can J Anaesth 2004;51:96.
5. Lee YW, Lee TS, Chan KC, et al. Intratracheal kinking of endotracheal tube. Can J
Anaesth 2000;50:311–2.
6. Ayala JL, Coe A. Thermal softening of
tracheal tube: an unprecedented hazard
of the Bair Hugger Active patient warming system. Br J Anaesth 1997;79:543–5.
7. Asai T, Shingu K. Difficulty in advancing
a tracheal tube over a fibreoptic bronchoscope: incidence, causes and solutions.
Br J Anaesth 2004;92:870 – 81.
8. Nichols KP, Zornow MH. A potential
complication of fibreoptic intubation. Anesthesiology 1989;70:562–3.
9. Weksler N, Klein M, Weksler D, et al.
Retrograde tracheal intubation: beyond
fibreoptic endotracheal intubation. Acta
Anesthesiol Scand 2004;48:412– 6.
10. Mahajan R, Sandhya Y, Chari P. An
alternative technique for retrograde intubation. Anaesthesia 2001;56:1207– 8.
DOI: 10.1213/01.ANE.0000215211.59302.EE
In Response:
We would like to thank Mahajan
et al. (1) for their interest in our
article (2). We reported that a
Magill-tipped endotracheal tube
(ETT) causes less nasal trauma during nasotracheal intubation than a
Murphy-tipped ETT and that the
nonthermosoftened Magill-tipped
ETT is comparable to the thermosoftened Murphy-tipped ETT.
Previous reports about thermosoftening of polyvinyl chloride
ETTs (3–5) agree with our personal
experience that ETT kinking and airway obstruction are rare, despite a
few case reports (6). No problems
were noted after immersion of ETTs
in warm saline of approximately 45°C
(4). We agree that overheating of any
polyvinyl chloride ETT can produce
serious problems, so the temperature
of the saline must be controlled.
Provided that the temperature is
adequately controlled, there is no
reason to abandon thermosoftening
of ETTs. As recommended in our
article (2), if thermosoftening is not
used, then a Magill-tipped ETT will
likely prove less traumatic than a
Murphy-tipped ETT during nasotracheal intubation.
Jae-Hyon Bahk, MD
Jong-Hwan Lee, MD
Department of Anesthesiology
Seoul National University Hospital
Seoul, Korea
[email protected]
REFERENCES
1. Mahajan R, Gupta R, Sharma A. Tube
design for nasotracheal intubation.
Anesth Analg 2006;102:xxx.
2. Lee JH, Kim CH, Bahk JH, Park KS. The
influence of endotracheal tube tip design
on nasal trauma during nasotracheal intubation: Magill tip versus Murphy tip.
Anesth Analg 2005;101:1226 –9.
3. Lu PP, Liu HP, Shyr MH, et al. Softened
tracheal tube reduces the incidence and severity of epistaxis following nasotracheal intubation. Acta Anaesthesiol Sin 1998;36:193–7.
4. Kim YC, Lee SH, Noh GJ, et al. Thermosoftening treatment of nasotracheal tube before
intubation can reduce epistaxis and nasal
damage. Anesth Analg 2000;91:698 –701.
5. Hall CE, Shutt LE. Nasotracheal intubation for head and neck surgery. Anaesthesia 2003;58:249 –56.
6. Lee YW, Lee TS, Chan KC, et al. Intratracheal kinking of endotracheal tube. Can J
Anaesth 2003;50:311–2.
DOI: 10.1213/01.ANE.0000215212.56140.A7
Electromagnetic Emission of
High-Energy Extracorporeal
Shockwave Lithotripsy to the
Shoulder Does Not Cause
Disruption of Bispectral
Index Monitoring of Propofol
or Sevoflurane Anesthesia
To the Editor:
Hemmerling et al. (1,2) in a recent series of case reports appearing in Anesthesia & Analgesia displayed disruptions of bispectral
index (BIS) monitoring (Aspect
Medical Systems Newton, MA)
ANESTHESIA & ANALGESIA
Letters to the Editor
Figure 1. Mean Bispectral Index (BIS) and electromyography (EMG) during extracorporeal shockwave therapy (ESWT) in six patients.
with a shoulder shaver device (1)
and with the use of an otorhinolaryngology electromagnetic positioning system (2). We examined the
effect on BIS monitoring of an electromagnetic emitter of a highenergy extracorporeal shockwave
therapy (ESWT) lithotripter applied
to the shoulder.
After Graz Medical University
ethics committee approval, and
written informed consent, 6 adult
patients underwent shoulder ESWT
lithotripsy for symptomatic rotator
cuff calcareous tendinopathy under
propofol general anesthesia (group
1, 3 patients) or sevoflurane-nitrous
oxide (N2O) (group 2, 3 patients).
BIS “Quattro” sensors were placed
on patients’ foreheads and connected to a BIS XP monitor (version
3.4). Data were captured from the
Serial Port onto a laptop computer
every 5 s, after verifying a signal
quality index of ⬎95% and electrodes impedance of ⬍5 k⍀. The
smoothing window was set at 30 s.
Anesthesia was induced with fentanyl 1.5 ␮g/kg and propofol
2–3 mg/kg, followed by rocuronium 600 ␮g/kg to facilitate tracheal intubation. Anesthesia was
maintained with either propofol
100 –150 ␮ g 䡠 kg ⫺1 min ⫺1 and
remifentanil 0.1– 0.3 ␮g 䡠 kg⫺1min⫺1
(group 1) or sevoflurane 1 MAC with
60% N2O in oxygen (group 2). All
patients underwent electromagnetic
Vol. 103, No. 1, July 2006
induction of high-energy shockwave
lithotripsy to the shoulder (Minilith
SL1; Storz Medical, Kreuzlingen,
Switzerland). The energy flux density in the therapy focus was 0.5 mJ/
mm2 of a total of 2000 –3000
impulses.
In all 6 patients, BIS tracings indicated a signal quality index of
⬎95%. With induction of anesthesia
the mean ⫾ sd BIS value declined
to 28.4 ⫾ 2.7. Anesthesia was maintained at BIS 36.7 ⫾ 3.1 before the
start of ESWT. The mean BIS value
during ESWT was 37.2 ⫾ 2.7,
whereas the BIS value in the 10 min
after the switching the ESWT off
remained at 37.9 ⫾ 3.4 before starting to increase with termination of
anesthesia (Fig. 1). During the anesthesia maintenance phase, using
the paired Student’s t-test there was
no statistically significant difference between mean BIS values before and during (P ⫽ 0.2384) ESWT
or between during and after (P ⫽
0.2198) switching the ESWT off.
There was no significant difference
in electromyelogram values before,
during, and after ESWT.
The literature reports demonstrating artifactual increases in
BIS give the impression that electric devices applied to the shoulder “similar” to the shoulder
shaver (1), or devices generating
an electromagnetic field (2), are
likely to result in erroneous BIS
readings. In the former case, BIS
suddenly increased from 40 to
60 during the activity of endoscopic shoulder shaver oscillations and decreased equally
abruptly after the end of the use of
the shaver device (1). Our modest
study suggests that the new BIS
algorithm is properly shielded
against shoulder vibrations caused
by the electromagnetic shock wave
emitter. In the latter report, switching a three-dimensional otorhinolaryngology electromagnetic positioning device increased the BIS
from 40 to 60 –90 despite increased
anesthetic drug doses, during both
propofol and sevoflurane maintenance of anesthesia. We failed to
find any suggestion that outside
electromagnetic field generated
during ESWT altered the BIS. This
may reflect further refinement of
the BIS to exclude such artifacts or
may reflect a difference in the electromagnetic fields between that
generated by the ESWT device
compared with the electromagnetic
positioning device.
Despite these negative findings,
the electroencephalogram (EEG)
waveform is easily altered by artifacts. The possibility of artifact
should always be considered when
evaluating the information obtained from computerized EEG
monitors.
© 2006 International Anesthesia Research Society
255
Letters to the Editor
Ashraf A. Dahaba, MD, MSc, PhD
Helmar Bornemann, MD
Department of Anaesthesiology and
Intensive Care Medicine
[email protected]
Peter H. Rehak, PhD
Biomedical Engineering and Computing Unit of
the Department of Surgery
Helfried Metzler, MD
Department of Anaesthesiology and Intensive
Care Medicine
Graz Medical University
Graz, Austria
REFERENCES
1. Hemmerling TM, Migneault B. Falsely
increased bispectral index during endoscopic shoulder surgery attributed to interferences with the endoscopic shaver
device. Anesth Analg 2002;95:1678 –9.
2. Hemmerling TM, Desrosiers M. Interference of electromagnetic operating systems in otorhinolaryngology surgery with
bispectral index monitoring. Anesth
Analg 2003;96:1698 –99.
DOI: 10.1213/01.ANE.0000215216.87039.3A
Total Intravenous Anesthesia
with Propofol and
Remifentanil for VideoAssisted Thoracoscopic
Thymectomy in Patients with
Myasthenia Gravis
To the Editor:
Total IV anesthesia (TIVA) may
preclude the need for muscle relaxants in patients with myasthenia
gravis. With IRB approval and written informed consent we anesthetized five myasthenic patients with
concurrent remifentanil and propofol infusions for elective, right,
video-assisted thoracoscopic (VAT)
thymectomy, including placement
of the double-lumen endotracheal
tube without the use of muscle
relaxants.
Patients continued their dose of
pyridostigmine up to and including
the morning of surgery. We administered IV glycopyrrolate 0.4 mg
before anesthesia induction. Anesthesia was induced with propofol
2 mg/kg and remifentanil 2 ␮g/kg,
immediately followed by infusions
of propofol, 10 mg · kg⫺1 · h⫺1, and
remifentanil, 0.5 ␮g · kg⫺1 · min⫺1.
We ventilated the patient’s lungs by
mask, and approximately 1 min
later intubated the patient’s trachea
with an appropriately sized leftsided double-lumen endotracheal
tube. The anesthesiologist assessed
the ease of mask ventilation, jaw
relaxation, laryngoscopy, vocal
cord position, and patient response
to intubation (coughing, limb
movement). Table 1 compares patients, disease status, and intubating conditions. The procedure was
then performed using one-lung
ventilation. The lung was ventilated without difficulty or excessive
pressure. We infused propofol at
10 mg · kg⫺1 · h⫺1 for the first
10 min, 8 mg · kg⫺1 · h⫺1 for the
next 10 min, and then at
5– 6 mg · kg⫺1 · h⫺1 for the duration
of the procedure. Remifentanil was
maintained at 0.5 ␮g · kg⫺1 · min⫺1
throughout the procedure. At chest
closure, the propofol rate was decreased to 4 mg · kg⫺1 · h⫺1 and the
remifentanil rate was decreased to
0.25 ␮g · kg⫺1 · min⫺1, which were
further reduced to 2 mg · kg⫺1 · h⫺1
and 0.15 ␮g · kg⫺1 · min⫺1, respectively, at skin closure. We also administered IV morphine 0.12–0.15 mg/kg
and infiltrated the incisions with 0.5%
bupivacaine.
Both infusions were stopped at
the end of surgery. Within 10 min
of ending the infusions every patient was awake and generating adequate tidal volumes. Patients were
tracheally extubated in the operating room and monitored overnight
in the intensive care unit. None of
the patients were excessively sedated or had evidence of respiratory compromise.
A recent report described delayed awakening after administration of sevoflurane and remifentanil anesthesia in a myasthenic
patient undergoing transsternal
thymectomy (1). Our report does
not confirm these findings. Rather,
our findings are similar to those of
other reports (2– 6). Our modest series demonstrates that TIVA with
propofol and remifentanil can be
successfully used for VAT thymectomy in myasthenic patients at
doses that provide good conditions
for tracheal intubation (with a
double-lumen endotracheal tube)
Table 1. Patient information and conditions for tracheal intubation
Case
1
Age, yr/gender
Osserman classification
Disease duration, months
Medication, mg per day
Pyridostigmine
Prednisolone
Conditions for intubation
Mask ventilation*
Jaw relaxation†
Laryngoscopy*
Vocal cords‡
Coughing§
Limb movement§
2
3
4
5
33F
III
2
64F
I
6
24M
IIB
8
49F
I
2
32F
I
4
480
40
180
240
40
180
90
Easy
Complete
Easy
Open
None
None
Easy
Complete
Easy
Open
Slight
None
Easy
Complete
Easy
Open
None
None
Easy
Complete
Easy
Open
None
None
Easy
Complete
Easy
Open
None
None
*Easy, fair, difficult or impossible; †complete, slight tone, stiff, rigid; ‡open, moving, closing, closed; §none, slight, moderate, severe.
256
Letters to the Editor
ANESTHESIA & ANALGESIA