SAMBA Talks eNewsletter

Volume 5, Issue 1

S A M B A T A L K S - PAGE 2

June, 2005

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Need advice about a problem case in ambulatory anesthesia? Want suggestions about a difficult situation in your ambulatory surgery center? Have a reply to questions others have raised about ambulatory anesthesia issues?

If you answered "yes" to any of these questions, or would like to share with other professionals a comment or opinion on a topic related to ambulatory anesthesia then please "Join the Discussion" here.

To enter the Discussion with a question, reply, or other comment, please contact us. Your submission will be published in this section of the next available issue of SAMBA TALKS. Include your name (or initials), city, and state, if you would like these published. Please note that because of the high volume of questions we receive, there is often a delay of 1 to 2 months before the questions can be published.

Questions and responses from previous months are now available at the eNewsletter Discussion Archive. If you have any comments regarding the previous questions, please submit them to SAMBA Discussion, and they will be published here next month.

Please note: The information presented in the replies below does not represent SAMBA policy. The replies are solely the opinions of the individuals who wrote them.

?? - LAST MONTH'S QUESTION WITH REPLIES - ?? - TOP

QUESTION 1:

ENT CASES & DIFFICULT INTUBATION AT AMBULATORY SURGERY CENTER

We are having an ongoing heated discussion with our ENT physicians about doing surgery at our ambulatory surgery center on patients who are known difficult intubations or appear to be difficult intubations by our standard anesthesia exam. They argue that they are airway experts also with an entirely difficult skill set than Anesthesiologists. Also, they say they have examined the patients in their office and have determined by their criteria that the patients can be intubated. We have brought up the arguments that we don't have the equipment, they say they'll purchase all the equipment. We argue we don't have the back up help, other anesthesiologist, they argue that their presence constitutes another skilled set of hands as well as our CRNA. Their belief is that if they examined the patient and feel the airway is obtainable, it doesn't matter what our examination shows, even if the patient has been an awake fiberoptic intubation in the past after failed intubation, they will be able to safely obtain an airway in the patient. They have said they will schedule the case so no other cases are occurring so that the MDA can give the difficult airway their full attention.

Does SAMBA have any official position on taking care of patients who are known to be difficult to intubate at ambulatory surgery centers?

-- Anonymous.

REPLY:

This letter raises some very interesting points. Unfortunately, there is no clear and obvious answer to this important question, since every clinical case is different. It is certainly true that anesthesiologists and otolaryngologists have different airway management skill sets and may also have different degrees of risk perception and risk aversion by virtue of differences in clinical training and perhaps even differences in clinical culture. In the end, the question is at least partly "How much do you trust the otolaryngologist you are working with to be able to rescue you from a situation you would not have normally gotten into?"

I have certainly seen some amazing airway rescues by otolaryngologists using a Dedo laryngoscope, but I cannot help wonder if the safest course would not still be awake intubation in a regular OR in doubtful cases. Complicating this discussion is the fact that some new airway tools like the GlideScope (details available at my web page at www.glidescope.net) may make many previous difficult airways far, far easier. Personally, if ALL the tools I wanted were available and I did not have an additional concurrent case to worry about, I would be comfortable with most awake or difficult intubations in an ambulatory setting. But not all.

I do not believe that SAMBA has any official position on taking care of patients who are known to be difficult to intubate at ambulatory sugery centers. This particular issue sorely needs review and debate before any such position can be considered.

-- D John Doyle, M.D., Cleveland, Ohio

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QUESTION 2:

DISCONTINUATION OF ACE INHIBITORS

There has been a lot in the literature in the past 5 or 6 years about hypotension during anesthesia in patients treated with chronic ACE inhibitors for hypertension. We have even had a few cases over the years that have only responded to vasopressin. Does anyone have a policy about discontinuing ACE-I for 24 hours or more prior to surgery?

-- From Dana Wiener, M.D., Durham, NC

REPLY:

The decision to administer an angiotensin converting enzyme inhibitor (ACEI) or angiotensin receptor blocker (ARB) on the morning of surgery remains controversial. While considerable evidence has accumulated favoring their use in the treatment of hypertension, acute myocardial infarction and cardiomyopathy (heart failure), the continuation of ACEIs or ARBs on the day of surgery appears to cause unfavorable, sometimes intractable, intraoperative hemodynamic effects. This hypotensive effect can be exacerbated by hypovolemia.

Several studies have reported intraoperative hypotension with the use of ACEIs and ARBs in the surgical setting. Coriat et al first reported an increased likelihood of hypotension on induction of anesthesia in patients treated with ACEIs.¹ In another report from the same group, Bertrand et al reported anesthesia-induced hypotension in patients treated with ARBs.² Toraman reported an association between ACEI and an increased need for volume replacement in cardiac surgical patients,³ and, most recently, Comfere et al reported that hypotension (systolic blood pressure ≤ 85 mm) occurred more frequently in patients who had last ACEI / ARB therapy < 10 hours prior to anesthetic induction (odds ratio 1.74, 95% confidence interval 1.03-2.93).⁴

Although some investigators have reported acceptable intraoperative hemodynamics in patients treated with ACEI or ARBs, they have had to use increased doses of vasoconstrictors or modify the induction of anesthesia. Tuman et al reported an increased need for vasoconstrictors after cardiopulmonary bypass in patients taking ACE inhibitors.⁵ Although Licker et al appear to advocate the continuation of ACEI preoperatively,⁶ in one of their studies they used less midazolam and fentanyl during induction of cardiac surgical patients treated with ACEIs.⁷

To safely care for these patients, one must be prepared to treat hypotension that often responds poorly to standard treatment. Recent studies have investigated the use of vasopressin analogs or norepinephrine in treating hypotension associated with ACEI or ARBs. The use of terlipressin (not available in the United States) or norepinephrine may be more appropriate than ephedrine in this patient population.^⁸,⁹

Undoubtedly, many patients benefit from these drugs, but these patients are more likely to develop hypotension associated with anesthesia when they continue their treatment into the intraoperative setting. Treating hypotension associated with ACEIs and ARBs may require significant volume administration and / or the use of vasopressin analogs or norepinephrine.

Because the continuation of ACE inhibitors or ARBs into the perioperative setting seems to be of questionable benefit and frequently produces undesirable effects in the operating room, patients at the University of Texas MD Anderson Cancer Center are advised to discontinue their ACEI or ARB on the day of surgery. These patients’ medications can then be continued postoperatively as early as it seems appropriate, which can be in the Post Anesthesia Care Unit with intravenous preparations.

Although future research may demonstrate a presently unrecognized benefit of treating patients with ACEI or ARB in the immediate perioperative setting, we continue to base our policies on the belief that intraoperative hemodynamics can be more safely managed when ACEI or ARB is withheld.

-- Jonathan Hughes, D.O., Houston, TX

-- Marc A Rozner, M.D., Houston, TX

Reference List

Coriat P, et al. Influence of chronic angiotensin-converting enzyme inhibition on anesthetic induction. Anesthesiology 1994; 81(2):299-307.
Bertrand M, et al Should the angiotensin II antagonists be discontinued before surgery? Anesth Analg 2001; 92(1):26-30.
Toraman F, et al. Highly positive intraoperative fluid balance during cardiac surgery is associated with adverse outcome. Perfusion 2004; 19(2):85-91.
Comfere T, et al. Angiotensin system inhibitors in a general surgical population. Anesth Analg 2005; 100(3):636-44.
Tuman KJ, et al. Angiotensin-converting enzyme inhibitors increase vasoconstrictor requirements after cardiopulmonary bypass. Anesth Analg 1995; 80(3):473-479.
Licker M, et al. Preoperative inhibition of angiotensin-converting enzyme improves systemic and renal haemodynamic changes during aortic abdominal surgery. Br J Anaesth 1996; 76(5):632-639.
Licker M, et al. Long-term angiotensin-converting enzyme inhibitor treatment attenuates adrenergic responsiveness without altering hemodynamic control in patients undergoing cardiac surgery. Anesthesiology 1996; 84(4):789-800.
Meersschaert K, et al. Terlipressin-ephedrine versus ephedrine to treat hypotension at the induction of anesthesia in patients chronically treated with angiotensin converting-enzyme inhibitors: a prospective, randomized, double-blinded, crossover study. Anesth Analg 2002; 94(4):835-40.
Boccara G, et al. Terlipressin versus norepinephrine to correct refractory arterial hypotension after general anesthesia in patients chronically treated with renin-angiotensin system inhibitors. Anesthesiology 2003; 98(6):1338-1344.

?? -- THIS MONTH'S QUESTION -- ?? - TOP

UTILITY OF DEPTH OF CONSCIOUSNESS MONITORING

According to the ASA official 2003 position on MAC (monitored anesthesia care), the mere loss of consciousness (without regard to whether local or systemic analgesia is administered) transforms a MAC case into a general anesthetic.

Bispectral index or BIS levels compatible with general anesthesia are well published to occur at 45-60. Adding systemic analgesia to BIS 45-60 would be my definition of general anesthesia.

Inasmuch as the ASA has not, to date, embraced the notion of level of consciousness monitoring as worthwhile, it then places the anesthesiologist using BIS monitored propofol ketamine MAC (at BIS 60-75) in the position of having to have an anesthesia machine, scavenging and dantrolene. None of these items improves patient safety, yet enormously increases costs to the office-based OR.

Does SAMBA yet have a position on the utility of level of conscious monitors in general and BIS in specific? If not, why not?

-- From Barry L. Friedberg, M.D., Corona del Mar, CA

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