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Anesthesiology:
doi: 10.1097/ALN.0b013e3181a36fed
Correspondence

Intracarotid Etomidate

Joshi, Shailendra M.D.*; Meyers, Phillip M. M.D.; Ornstein, Eugene M.D., Ph.D.

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In Reply:—

We thank Dr. Venkatraghavan for raising two specific comments on our review: The first is the use of sedation during Wada testing; the second is the use of intraarterial etomidate for the same procedure.1 Both comments reinforce our general theme that there are significant variations in handling of anesthesia and interventional drugs, selection, and doses during endovascular procedures.
With regard to the “judicious use of sedation during Wada testing,” Dr. Venkatraghavan correctly point out that Wada testing often is done without an anesthesiologist’s supervision with minimal or no sedation. However, the anesthesiologists are routinely involved when any intervention is contemplated, such as during superselective Wada testing. For these longer procedures we use small doses of midazolam (1–2 mg), propofol (10–25 μg · kg−1 · min−1) and fentanyl 0.5–1.5 μg/kg). These drugs are withheld at least 20 min before memory or psychomotor testing. Dundee and Wilson tested for anterograde amnesic action of midazolam (5 mg) and found the onset to be within 3 to 5 min, with the effect lasting 20 min.2 Bulach et al. looked at midazolam pretreatment in a dose range of 2 to 10 mg and found a dose-dependent impairment of anterograde memory, but no effect on retrograde amnesia.3 To our best knowledge there is no hard evidence to suggest that 1 to 2 mg of midazolam given 20 to 60 min before testing impairs conventional memory tests.
The question arises whether studies in healthy subjects apply to those with preexisting neurologic deficits. Low doses of residual sedative/hypnotics are known to unmask neurologic deficits and could in theory impair memory tests.4 Hence, even if data from healthy volunteers might suggest a lack of amnesic effect with low doses of midazolam, caution needs to be exercised in prescribing sedatives or hypnotics to those with suspected neurologic deficits. What helped in framing the policies at our institution was a quality improvement review of patient data to assess the use of midazolam during Wada testing that found no impairment of memory.
We are thankful to Dr. Venkatraghavan for elaborating on the use of etomidate for Wada testing that is also supported by our experimental data.5 These comments illustrate the diversity in the selection and dose of drugs used intraarterially or systemically during endovascular procedures. We emphasize that the surgeons and anesthesiologists should formulate a coherent management strategy based on the specific needs of the patient and endovascular procedure.
Shailendra Joshi, M.D.,*
Phillip M. Meyers, M.D.
Eugene Ornstein, M.D., Ph.D.
*College of Physicians and Surgeons of Columbia University, New York, New York. sj121@columbia.edu
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References

1. Joshi S, Meyers PM, Ornstein E: Intracarotid delivery of drugs: The potential and the pitfalls. Anesthesiology 2008; 109:543–64

2. Dundee JW, Wilson DB: Amnesic action of midazolam. Anaesthesia 1980; 35:459–61

3. Bulach R, Myles PS, Russnak M: Double-blind randomized controlled trial to determine extent of amnesia with midazolam given immediately before general anaesthesia. Br J Anaesth 2005; 94:300–5

4. Thal GD, Szabo MD, Lopez-Bresnahan M, Crosby G: Exacerbation or unmasking of focal neurologic deficits by sedatives. Anesthesiology 1996; 85:21–5

5. Joshi S, Wang M, Etu J, Nishanian EV: Comparison of intracarotid anesthetics for EEG silence. J Neurosurg Anesthesiol 2006; 18:112–8

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