Preoperative Autonomic Tests of Geriatrics: Does it Predict the Effect of Labetalol on Cardiovascular Responses to Tracheal Intubation?

Lee, Il Ok

Abstract

BACKGROUND: This study was to evaluate the relationship of preoperative autonomic tests to the labetalol effect on cardiovascular responses to intubation of geriatrics(65 years of age or older, n=23). The autonomic tests consisted of heart rate response to deep breathing(HRdb), Valsalva ratio(VR), 30/15 ratio(30/15) to assess parasympathetic function. The systolic blood pressure change response to standing(delta SBP) and mean arterial pressure change response to standing(delta MAP) were to assess sympathetic function.
METHODS
These autonomic tests were taken preoperatively. At a separate time, labetalol 1.0 mg/kg was injected as a bolus 3 minutes before induction with thiopental sodium (4 mg/kg), succinylcholine (1 mg/kg). The anesthesia was maintained with enflurane, oxygen, nitrous oxide and vecuronium (0.08 mg/kg). The blood pressure and heart rate(HR) were recorded at one minute intervals for 5 minutes after intubation. The hypotension (SBP<90 mmHg) or bradycardia (HR<60 beats/minute) were recorded for 10 minutes after intubation. After anesthesia, they were divided two groups according to presence(old abnormal group, n=10, who required intraoperative vasopressors) or absence(old normal group, n=13, who did not require intraoperative vasopressors) of hypotension or bradycardia.
RESULTS
The VR and delta MAP revealed significant correlation with SBP and HR after intubation and 5 minutes later(p<0.05). The autonomic test results revealed significant autonomic dysfunction(p<0.05) among old abnormal group compared with old normal group. HR and SBP declined to a greater degree(p<0.05) during induction of anesthesia in old abnormal group compared with old nortnal group. There was less(p<0.05) increase in the same parameters following intubation in old abnormal group. The highest sensitive autonomic test was VR and the highest specific autonomic test was delta MAP.
CONCLUSIONS
Geriatric patients are at increased risk for cardiovascular instability during intubation. The preoperative evaluation with autonomic tests may be useful in identifying those at high risk for perioperative hypotension or bradycardia when pre-induction intravenous labetalol 1.0 mg/kg is indicated.