ABSTRACT
BACKGROUND: The incidence of hypotension after spinal anesthesia is highest in cesarean section. The authors' first retrospective study identified three risk factors that included two non-modifiable (patient's height and low baseline systolic blood pressure) and one modifiable risk factor (sensory analgesia equal to or higher than TS) associated with hypotension. OBJECTIVE: To create a prospective record of the event in the patients who received successful spinal anesthesia for cesarean section. MATERIAL AND METHOD: A prospective data collection, together with questionnaires that were completed by the responsible anesthetic team at the end of the operation for each consecutive patient. All parameters were coded and recorded in SPSS11.5. To assess the association between two categorical variables in a univariable analysis, chi-square test was used along with odds ratio (OR) and its 95% confidence interval (CI). Mutivariable analysis via multiple logistic regressions was employed to determine the effect of each independent variable. RESULTS: Eight hundred and seven full-term pregnant women received successful spinal anesthesia for cesarean section at Siriraj Hospital from July 1 to December 31, 2004. Hypotension was defined as lowest systolic < 100 mmHg and the pressure was lower to equal to or more than 20% of baseline. Incidence of hypotension was 65.1%. Age > 35 yr BMI > 35 were two non-modifiable risk factors that increased the incidence of hypotension in the crude odds ratio (OR) 1.62 and 2.83 respectively with narrow 95% confidence interval. The level of sensory analgesia equal to or higher than T5 was the only one modifiable risk factor that increased the incidence of hypotension with crude OR 1.55 and narrow 95% CI. CONCLUSION: Limitation of the dose of local anesthetic agent or addition of some opioids could reduce the incidence and severity of hypotension after spinal anesthesia for cesarean section.