Anesthetics

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Many of the neuromuscular blocking agents are eliminated by the kidney and require dose adjustment in patients with renal dysfunction. For some of these drugs no data are available to allow development of guidelines for use in patients. Use of any of these drugs in the patient with renal failure requires caution, and it has been recommended that a peripheral nerve stimulator be employed to assess the degree of neuromuscular blockade. Short of this, the clinician must be aware that a patient with renal dysfunction may have slow recovery from anesthesia owing to both retention of anesthetic agents eliminated by the kidney or to additional factors that again are related to renal function. For example, patients with renal disease who either accumulate aminoglycoside antibiotics to high concentrations or who are potassium depleted may have prolonged respiratory suppression in the face of anesthetic agents as a result of the "curare like" effect that can occur with these antibiotics. The same principles apply to patients with liver disease and to drugs eliminated by hepatic routes.

Fazadinium appears to have only minor changes in pharmacokinetics in patients with end stage renal disease and may, therefore, be a preferred agent in patients with renal dysfunction.

Alfentanil, fentanyl, and propofol have been studied in the elderly. The disposition of the former two drugs was no different than in young patients. However, the pharmacodynamics were clearly altered such that half as much of either drug resulted in the same CNS depression as in young patients. The mechanism of this increased sensitivity is unknown. The initial volume of distribution and the clearance of propofol in elderly patients were about 75% of those in young patients. Thus, with this anesthetic, lower doses should also be used in elderly patients.


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