Incidence and Risk Factors of Hypotension and Bradycardia During Spinal Anesthesia

Abstract

Objective: Hypotension and bradycardia during spinal anesthesia are common and may relate to severe adverse events such as cardiac arrest or death. Knowledge of the incidence and risk factors as well as their patho-physiology processes will improve management, planning for anesthesia, training and practice guidelines for the patients receiving spinal anesthesia.
Methods: We retrospectively reviewed anesthetic records of 1,698 patients who received spinal anesthesia at Siriraj Hospital from 1 January 2004 to 30 June 2004. The collected parameters were patient demographic data (sex, age, body weight, height, ASA status), operative data (type of operation, emergency status, position and duration of operation),anesthetic data (type and dosage of local anesthetic agents used, intravenous fluid, vasoactive and sedative agents, sensory level of spinal blockage, usage and doses of spinal opioids as well as oxygen supplementation). The lowest systolic, diastolic blood pressure, heart rate and onset of the incidence were collected and analyzed for correlation by appropriate statistical analysis. Bradycardia was defined when heart rate is 50 beat/min or lower and hypotension when systolic blood pressure decreases to 20% or more of the baseline pressure.
Results: Incidence of hypotension in this study was 54.4% at 19.4 min. The correlated parameter with increased incidence of hypotension included female (crude odd ratio = 2.005; 95% CI 1.63-2.48), age more than 40 years (adjusted odd ratio = 3.06-6.88; 95%CI 1.55-15.74 upon age group), level of blockage higher than T5 (adjusted odd ratio =1.23; 95%CI 1.15-1.31) and finally type of operation. Operation of hip and femur and cesarean section had adjusted odd ratio = 2.13; 95%CI 1.04-4.38 and 2.32; 95%CI 1.28-4.21, respectively. Incidence of bradycardia in our study was 0.06% which was too low to analyze for correlated parameter. There was no cardiac arrest nor death reported in this study.
Conclusion: Level of blockage higher than T5 was the only one modifiable risk factor associated with hypotension during spinal anesthesia that could be identified from this study. Avoidance of high block is the only factor that can be controlled to decrease the incidence and severity of hypotension.