The incidence and risk factors of hypotension and bradycardia associated with spinal anesthesia.

Objectives: Hypotension and bradycardia after conduction of spinal anesthesia are common and may lead to intraoperative cardiac arrest or death. The present study was carried out to investigate the incidence and risk factors of hypotension and/or bradycardia in the patients receiving spinal anesthesia.

Material And Method: The authors prospectively studied 1,220 patients to identify the incidence of hypotension (> 30% decreased systolic blood pressure) and bradycardia (heart rate < 60 beats/min) after spinal anesthesia. Historical, clinical and physiologic data were correlated with the incidences by univariate analysis. Logistic regression with a forward stepwise algorithm was performed to identify independent variables. A p value < 0.05 was considered significant.

Results: Incidence of hypotension and bradycardia were 36.8% and 4.9% respectively. The risk factors of hypotension included increasing age (OR = 1.019 ; 95%CI 1.017-1.031); analgesia level > or = T4 dermatome (OR = 2.068; 95%CI 1.486-2.879); body mass index > or = 30 (OR = 1.534; 95%CI 1.120-2. 100); cesarean section (OR= 1.723; 95%CI 1.244-2.386 and prehydration fluid < 500 mL (OR 1.472; 95%CI 1.071-2.023). The risk factors of bradycardia were increasing age (OR = 1.042; 95%CI 1.023-1.061) and analgesic level > or = T4 dermatome (OR = 2.246; 95%CI 1.101-4.584).

Conclusion: The incidence of hypotension and bradycardia may increase with increasing age and analgesic level > or = T4 dermatome. Three other factors related to hypotension after spinal anesthesia were body mass index > or = 30, cesarean section, and prehydration fluid of less than 500 mL.