A scholarly review of 80 randomized clinical trials looked for evidence of preemptive analgesia.1 Injection of local anesthesia before incision was performed under general anesthesia. Ten percent of the randomized clinical trials administered systemic N-methyl-D-aspartate receptor antagonists, but not using a dissociative model (i.e., hypnosis first, then dissociation).2 Møiniche et al. concluded there was a negative potential benefit of preemptive analgesia on postoperative pain.2 General anesthesia may only provide a stupefaction that prevents the brain from generating an immediate response to afferent noxious stimuli (i.e., injection of local analgesia). The dissociative model may provide nonresponsiveness by blocking afferent stimulation.2
Using opioids and inhalational agents to provide general anesthesia may be iatrogenic causes for postoperative nausea and vomiting.3 Under general anesthesia, surgeons may be unwittingly inflicting pain on nonreactive patients. Postoperative pain, which may also produce postoperative nausea and vomiting, may simply be a function of intraoperative pain. The literature is replete with accounts of postoperative pain issues for patients emerging from general anesthesia1 but not with those receiving bispectral index (BIS; Aspect Medical Systems, Norwood, Mass.)–monitored propofol-ketamine anesthesia care.2
Note well that N-methyl-D-aspartate receptors are located only in the spinal cord and midbrain. The weight of the adult brain does not appear to vary in tandem with body weight. The brain weight of a 250-pound man is clearly not 2.5 times greater than that of a 100-pound woman. Therefore, dosing ketamine on the basis of body weight to saturate N-methyl-D-aspartate receptors may be illogical.
The “ketamine-dose-independent-of-body-weight concept” may explain the empirical observation (over 16 years, in more than 4000 patients of more than 100 different surgeons) of successful repetition, that most adult patients will have their N-methyl-D-aspartate receptors saturated with a 50-mg ketamine dose2 and thus be unresponsive to local anesthetic injection. Absent noxious afferent stimuli, the brain cannot experience the wind-up phenomenon.
Hypnotic doses of propofol block ketamine hallucinations. Reproducibility of the hallucination-free administration of the ketamine has been achieved by incrementally titrating propofol to a bispectral index of 70 to 75 before administration of the ketamine.2 Although a transient rise in bispectral index may occasionally be seen with a 50-mg ketamine dose, the rise does not preclude successful propofol monitoring with bispectral index.4 Propofol hydroxylation has a 19-fold interindividual difference.5 Therefore, greater consistency of propofol dosing and hypnosis (ensuring hallucination-free ketamine administration) is more apt to occur with bispectral index monitoring than conventional milligrams-per-kilogram or blood level dosing regimens.
If the patient moves during the procedure, demonstrating propofol-titrated bispectral index levels of 60 to 75 (moderate or deep sedation with amnesia2) may convince the surgeon to inject more local anesthetic despite the appearance of a blanched operative field.
By eliminating both the before and during surgical sources of pain, bispectral index–monitored propofol-ketamine anesthesia care has allowed patients to emerge without sufficient discomfort to require opioids.2 Conducting cases without opioids or inhalational agents has also enabled these high-risk patients (i.e., nonsmoking women with previous postoperative nausea and vomiting, undergoing elective cosmetic surgery3) receiving bispectral index–monitored propofol-ketamine anesthesia care to experience a 0.5 percent postoperative nausea and vomiting rate without the use of antiemetics.2
Improved safety6 and greater patient satisfaction has been reported with bispectral index–monitored propofol-ketamine anesthesia care.2 Eliminating anesthesia machine purchase/maintenance, dantrolene acquisition/replacement, scavenging system, and staff overtime for prolonged emergence or treatment of pain or postoperative nausea and vomiting are additional, substantial, economic benefits of bispectral index–monitored propofol-ketamine anesthesia care over general anesthesia for cosmetic surgery.2
Barry L. Friedberg, M.D.
Cosmetic Surgery Anesthesia
3535 East Coast Highway, PMB 103
Corona del Mar, Calif. 92625
The author has no financial relationship with Aspect Medical Systems, Inc., makers of the BIS monitor.
1.Friedberg BL. Propofol ketamine with bispectral (BIS) index monitoring. In: Friedberg BL, ed. Anesthesia in Cosmetic Surgery.
New York: Cambridge University Press; 2007:1–13.
2.Møiniche S, Kehlet H, Dahl JB. A qualitative and quantitative systemic review of preemptive analgesia for postoperative pain relief. Anesthesiology
3.Apfel CC, Korttila K, Abdalla M, et al. A factorial trial of six interventions for the prevention of postoperative nausea and vomiting. N Engl J Med
4.Friedberg BL. The effect of a dissociative dose of ketamine on the bispectral (BIS) index during propofol hypnosis. J Clin Anesth
5.Court MH, Duan SX, Hesse LM, Venkatakrishnan K, Greenblatt DJ. Cytochrome P-450 2B6 is responsible for interindividual variability of propofol hydroxylation by human liver microsomes. Anesthesiology
6.Friedberg BL. Lethal pulmonary embolisms are avoidable. Plast Reconstr Surg.
2008;122:245–250; discussion 251–253.
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