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Asleep at the Wheel?

Lang, Scott A. MD

doi: 10.1213/01.ANE.0000146664.83332.D5
Letters to the Editor: Letters & Announcements

Clinical Associate Professor of Anesthesia; Department of Anesthesia; University of Calgary; Foothills Hospital; Calgary, Alberta, Canada;

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To the Editor:

“Few, if any, issues in anesthetic practice have inspired such divergent opinions as placement of epidural catheters, particularly thoracic catheters, in anesthetized patients” (1).

Dr. Drasner (1) suggests that, “in a situation where one must dispense with evidence-based practice (i.e., lack of solid evidence supporting a particular practice) one must revert to logic-based practice.” (1) We are asked to believe that logic suggests, in adult patients, that thoracic epidurals should be performed, with few exceptions, in conscious patients. Logic is the science of reasoning or inference that results in a conclusion following a given premise. If the premise is invalid, the conclusion will be flawed. The premise that an awake patient consistently provides information that will prevent or mitigate damage done by an improperly placed needle or catheter or that perceived damage in a conscious patient may allow early diagnosis and intervention, thereby minimizing the extent of any harm done, is unproven and may simply represent “wishful thinking” (2,3). The recommendation to place thoracic epidural catheters in awake patients is, therefore, best deemed “intuition-based” practice, but nonetheless may be useful when taken in context.

Even if a patient reports procedural pain or paresthesia, it is not clear how we should proceed, as it is not an uncommon phenomenon, is rarely associated with clinical sequelae, and altering or abandoning the procedure may not affect outcome. The unstated corollary assumes that the needle itself causes minimal injury, and serious injury is caused predominantly by injection through the needle, or by insertion of and injection via a catheter (i.e., primarily mechanical disruption that may be compounded by toxicity, ischemia, and inflammation). A series of case reports on spinal cord injury in obstetrical patients seems to support an alternative point of view (3). Most of the cases described were examples of regional anesthesia techniques (spinal, epidural, or CSE) performed in conscious obstetrical patients, some of whom reported procedural paresthesia or discomfort (3). The author concluded that “needle injury alone might be sufficient to cause irreversible damage” (3). If this is true, paresthesia may simply “herald” injury; damage will occur whether the patient is awake or asleep.

There does not seem to be any disagreement among enthusiasts of awake thoracic epidural catheterization in adult patients that, in exceptional circumstances, exceptions can be made (1,4–5). The nature of these “exceptional” circumstances have yet to be fully delineated. In these situations, we are advised to ensure that informed consent is obtained (1,5). Can such enlightenment of the patient actually be accomplished? Who has the time? Can it be facilitated in light of the realities of “production pressure” (6)? Do our professional institutions have some responsibility in assisting individual practitioners to develop better methods of obtaining informed consent in the face of controversy (7)?

If a tragic complication occurs, it will be no less tragic for the patient and their family even if everyone can agree that a proper informed consent was obtained, although it may be less spiritually damaging and result in a more “favorable” medicolegal outcome for the caregivers. Consent is important but will not, in itself, prevent complications. Perhaps our primary focus should be on developing technology and techniques that allow us to provide safer care while we await more information and better and safer substitutes for the way we currently practice—our primary objective should be the safe positioning of the needle and catheter, regardless of whether the patient is awake or asleep (8).

As an interim and continuing measure, I agree that we should enhance vigilance in the “hope” that morbidity can be mitigated by early diagnosis and intervention as pointed out by Dr. Drasner (1,7). Furthermore, I suggest that system processes that facilitate vigilance be applied to all forms of regional anesthesia-analgesia, even those procedures “traditionally” felt to be devoid of substantial risk (e.g., intercostal or paravertebral nerve blocks).

It is my opinion that we should divest ourselves, as a profession, of the emotionally laden divergent opinions of advocates and proponents and seek middle ground. Rather than suggest that a recommendation to prohibit placement of thoracic epidural catheters in anesthetized patients is supported by science to the exclusion of alternate points of view, let us be honest with our patients about the facts as we know them. The recommendation really represents an attempt to be perceived as responsible physicians in the face of the unknown. As Dr. Drasner emphasizes, placement of thoracic epidural catheters in awake adult patients is not difficult to accomplish (1). If this is acknowledged, it is reasonable to recommend that, because of the potential for rare but tragic consequences and a “perceived but questionable” benefit of performing the task in awake patients, it may be preferable to perform thoracic epidural catheterization while patients are conscious, thus avoiding discussion about right and wrong while still hoping for benefit.

Finally, consent forms that outline the presence and precise nature of the controversy, provide a recommendation, as well as details of alternative approaches, should be developed.

Scott A. Lang, MD

Clinical Associate Professor of Anesthesia

Department of Anesthesia

University of Calgary

Foothills Hospital

Calgary, Alberta, Canada

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1. Drasner K. Thoracic epidural anesthesia: asleep at the wheal? Anesth Analg 2004;99:578–9.
2. Krane EJ, Dalens BJ, Murat I, Murrell D. The safety of epidurals placed during general anesthesia [editorial]. Reg Anesth Pain Med 1998;23:433–8.
3. Reynolds F. Damage to the conus medullaris following spinal anaesthesia. Anaesthesia 2001;56:238–47.
4. Absalom AR, Martinelli G, Scott NB. Spinal cord injury caused by direct damage by local anaesthetic infiltration needle. Br J Anaesth 2001;87:512–5.
5. Ming-Chang Kao, Shen-Kou Tsai, Mei-Yung Tsou, et al. Paraplegia after delayed detection of inadvertent spinal cord injury during thoracic epidural catheterization in an anesthetized elderly patient. Anesth Analg 2004;99:580–3.
6. Anesthesia Patient Safety Foundation Newsletter. Special Issue: Production Pressure. Spring 2001; Vol 16, No. 1. Available at
7. Lang SA. Spinal epidural hematoma: still an enigma [editorial]. J Clin Anesth. In press.
8. Lang SA, Tsui B, Grau T. Sleeping epidural: new avenues of epidural research. Anesth Analg 2003;97:292–3.
© 2005 International Anesthesia Research Society