To the Editor:—
We read with great interest the review by Dr. Joshi et al.
on intracarotid delivery of drugs.1
In spite of recent advances in functional magnetic resonance imaging, the Wada test is still an important test for presurgical evaluation of patients with epilepsy.2
The intracarotid sodium amytal test (Wada test) has been used to lateralize cerebral dominance for speech and to evaluate memory in each hemisphere.3
Anesthesiologists are generally not involved in this procedure. In some centers, an anesthesiologist is on stand-by during the procedure to manage potential complications, namely stroke.
In the article by Dr. Joshi et al.,
there is mention that baseline sedation provided by the anesthesiologist in attendance would further complicate the interpretation of the Wada test and also suggests use of a judicious amount of sedation during the procedure. We disagree with the suggestion by the authors for the use of sedation during the procedure. These tests are done for evaluation of memory and language with unilateral intracarotid injection of drugs. Any sedation during the procedure will interfere with the memory testing.4
As a result of the recurrent shortages in the availability of sodium amytal, other agents are being used for Wada testing. As mentioned in the article, propofol or methohexitone have been used with limited success.5
Jones-Gotman et al.
have published their work in the use of etomidate for the Wada test.6
They have shown that etomidate is a viable alternative to sodium amytal, and its administration by bolus followed by infusion offers an improvement over the traditional Wada test. It is given as a 2-mg initial bolus (0.03-0.04 mg/kg) over 30 to 60 s, then an infusion of 0.003 to 0.004 mg/kg/min (approximately 6 ml/h neat etomidate 2 mg/ml) until the speech assessment and memory objects have been introduced. Many centers in the world are now switching to this etomidate speech and memory test. Manufacturer’s recommendations mandate an anesthesiologist to administer etomidate, so many anesthesiologists are now involved.7
In our institution, we have been using etomidate for the Wada test for the past year with great success. In addition, bilateral injection is our standard practice. The second injection is made only after the confirmation of complete clearance of the drug effects (both clinically and electroencephalographically).
Lashmi Venkatraghavan, M.D., F.R.C.A., F.R.C.P.C.,*
Anna Perks, F.R.C.A.
*Toronto Western Hospital, Toronto, Ontario, Canada. firstname.lastname@example.org
1. Joshi S, Meyers P, Ornstein E: Intracarotid delivery of drugs. The potential and the pitfalls. Anesthesiology 2008; 109:543–64
2. Binder JR, Swanson SJ, Hammeke TA, Morris GL, Mueller WM, Fischer M, Benbadis S, Frost JA, Rao SM, Haughton VM: Determination of language dominance using functional MRI: A comparison with the Wada test. Neurology 1996; 46:978–84
3. Wada JA: Clinical experimental observations of carotid artery injections of sodium amytal. Brain Cogn 1997; 33:11–3
4. Veselis RA, Reinsel RA, Feshchenko VA, Dnistrian AM: A neuroanatomical construct for the amnesic effects of propofol. Anesthesiology 2002; 97:329–37
5. Takayama M, Miyamoto S, Ikeda A, Mikuni N, Takahashi JB, Usui K, Satow T, Yamamoto J, Matsuhashi M, Matsumoto R, Nagamine T, Shibasaki H, Hashimoto N: Intracarotid propofol test for speech and memory dominance in man. Neurology 2004; 63:510–5
6. Jones-Gotman M, Sziklas V, Djordjevic J, Dubeau F, Gotman J, Angle M, Tampieri D, Olivier A, Andermann F: Etomidate speech and memory test (eSAM). A new drug and improved intracarotid procedure. Neurology 2005; 65:1723–9
7. Bedford Laboratories. Etomidate injection. Prescribing information. Bedford, Ohio; 2004
© 2009 American Society of Anesthesiologists, Inc.