AUTONOMIC REFLEX DYSFUNCTION IN PATIENTS PRESENTING FOR ELECTIVE SURGERY IS ASSOCIATED WITH HYPOTENSION AFTER ANESTHESIA INDUCTION

Background: Autonomic reflex dysfunction in patients with diabetes is associated with an increased incidence of hypotension after induction of anesthesia Whether this finding can be extrapolated to patients wit h autonomic dysfunction from other causes (e.g., advanced age, hyperte nsion, altered ventricular function) has not been established. Methods : The authors investigated whether autonomic reflex dysfunction in a m ore generalized patient group (26 consecutively consenting day-surgery patients older than 39 yr) was similarly associated with the occurren ce of hypotension after induction. Preoperative tests of autonomic fun ction included: Valsalva maneuver, change in heart rate with forced br eathing, change in heart rate and blood pressure with standing, and sp ectral analysis of heart rate variability. Anesthesia was induced with 3-5 mg/kg thiopental 2 mu g/kg fentanyl, and 60% N2O; 0.1 mg/kg vecur onium was used for paralysis; 0-1.5% isoflurane was added for maintena nce of anesthesia after intubation. Noninvasive measurements of mean b lood pressure were obtained every minute for 10 min after induction an d then every 3 min until skin incision. Results: Twelve patients devel oped hypotension (mean blood pressure < 70 mmHg), and 14 patients did not. Measurements of autonomic reflex function were significantly more abnormal in the patients who developed hypotension (P < 0.006 for Val salva measurements, heart rate variability parameters, and change in h eart rate with forced breathing). Using critical test values for auton omic tests, the incidence of hypotension was 67-83% in patients with a utonomic nervous system dysfunction versus 9-17% in other patients. Co nclusions: The results document that: (1) some degree of autonomic ref lex dysfunction is not uncommon in patients older than 39 yr presentin g for elective surgery, and (2) such dysfunction is associated with an increased Incidence of hypotension when using the described induction technique.