Abstracts of Posters Presented at the International Anesthesia Research Society; 72nd Clinical and Scientific Congress; Orlando, FL; March 7-11, 1998: Cardiovascular Anesthesia
Previous investigators have observed a consistent increase in heart rate and mean arterial blood pressure after a rapid increase in inspired desflurane concentration from 7.2 % (MAC 1.0) to 11% (MAC 1.5). This response has been attributed to sympathetic hyperactivity, possibly mediated by airway irritation. However, these studies were conducted in healthy young male volunteers. Since there is evidence that tracheobronchial irritability is reduced in elderly patients sympathetic changes mediated by the tracheobronchial responsiveness may be accordingly reduced. Therefore, we wished to compare the cardiovascular effects of desflurane increased incrementally from 4% to 10% in elderly and non elderly patients undergoing general anesthesia.
METHODS: Nonsedated ASA physical status I or II patients, not receiving vasoactive medications, and scheduled for peripheral operations not requiring muscle relaxation, signed an Institutional Review Board approved informed consent form. Anesthesia was induced with propofol (2 mg/kg IV) and a. laryngeal mask airway was positioned. Heart rate, systolic, diastolic and mean arterial blood pressure were recorded immediately after induction of anesthesia Patients then were given 4% desflurane while they breathed spontaneously. When stable, data were collected and inspired concentration of desflurane was increased to 10% in increments of 2% every two minutes. Data were collected after each incremental increase of desflurane. There was no surgical stimulation during the study. Measurement data were summarized as mean +/- 1SD. Intergroup comparisons were made using a Chi Square test (gender distribution) and an analysis of variance for repeated measures.
RESULTS: Twenty non-elderly and 20 elderly patients were studied. Percent change in heart rate associated with an increase in desflurane from 4% to 10% was statistically similar in non-elderly (10 +/- 28%) and elderly (17 +/- 26%) patients (P=20). Systolic, diastolic and mean arterial blood pressure also changed in a statistically comparable manner as desflurane was increased in non-elderly and elderly patients.
CONCLUSIONS: Desflurane induced sympathetic hyperactivity is not blunted in the elderly patient. If airway irritability is age dependent, the mechanism for desflurane induced sympathetic stimulation should be reconsidered.