Incidence and Risk Factors of Hypotension and Bradycardia after Spinal Anesthesia for Cesarean Section
Wanna Somboonviboon MD*, Oranuch Kyokong MD*, Somrat Charuluxananan MD*, Arunchai Narasethakamol MD*
Affiliation : * Department of Anesthesiology, Faculty of Medicine, Chulalongkorn University Bangkok
Background : Hypotension or bradycardia after spinal anesthesia for cesarean section remain common and
are serious complications. The current study evaluated factors associated to the incidences of hypotension or
bradycardia in this context.
Material and Method: A prospective cross sectional study from November 1, 2004 to July 31, 2005 was
conducted on 722 parturients undergoing cesarean section under spinal anesthesia. T-test and Chi-square
test were used in univariate analysis to compare continuous data and categorical data respectively. Multi-
variate logistic regression was performed on the variables hypotension (systolic pressure decrease > 30% of
baseline value) and bradycardia (heart rate < 60 bpm) p-value < 0.05 was considered significant.
Results : Incidence of hypotension and bradycardia were 52.6% and 2.5%. The probability of hypotension
increased with estimated blood loss 500-1000 mL (odds ratio [OR] = 1.86; 95% CI 1.30-2.67, p = 0.001),
estimated blood loss > 1000 mL (OR = 5.31; 95% CI 1.47-19.19, p = 0.011), and analgesia level > T4 (OR =
1.94; 95% CI 1.18-3.19, p = 0.009). Hypotension occurred despite left uterine displacement (OR = 1.56;
95% CI 1.11-2.19, p = 0.01). Risk factors associated with bradycardia were adding intrathecal morphine 0.2
mg (0.2 mL) (OR = 4.61; 95% CI 1.31-16.19, p = 0.017) to local anesthetics.
Conclusion : The present results indicated that the incidence of hypotension after spinal anesthesia for
cesarean section increased with amount of estimated blood loss > 500 mL and analgesic level > T4. Adding
intrathecal morphine 0.2 mg (0.2 mL) to local anesthetics increased incidence of bradycardia.
Keywords : Spinal anesthesia, Cesarean section, Hypotension, Bradycardia, Complication, Adverse events
