Objective: Hypotension and bradycardia during spinal anesthesia are common and may relate to severe adverse events such as cardiac arrest or death. The authors’ first retrospective study identified three nonmodifiable factors including females, age more than 40 years, and type of operation. Level of blockage higher than T5 was the only one modifiable factor that could be confirmed. That study was strongly limited by the nature of the retrospective anesthetic record reviewed study.

Material and Method: The authors prospectively studied the records of 2,000 patients who received spinal anesthesia at Sriraj Hospital from 1 July 2004 to 31 December 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, highest sensory level of spinal blockage, usage and doses of spinal opioids). Recording forms of hypotension and bradycardia were completed by the responsible anesthetic team in each consecutive patient.

Results: Incidence of hypotension (20% or more decrease in systolic blood pressure) in the present study was 57.9%. The highest incidence was in cesarean section. Four non-modifiable risk factors could be identified which included females, age more than 50, body mass index more than 35 (OR = 2.1, 95%CI 1.01-4.29) and type of operation. Two modifiable risk factors included high dose of heavy bupivacaine (OR 1. 88, 95%CI 1. 3-2.74) and level of sensory blockage equal to or higher than T5 (OR 2.27, 95%CI 1.73-2.97).

Conclusion: Usage of high dose of heavy bupivacaine and level of blockage higher than T5 were two modifiable risk factors associated with hypotension during spinal anesthesia. Avoidance of high block and lower dose of heavy bupivacaine can reduced the incidence and severity of hypotension after spinal anesthesia.

Keywords: Risk factors, Hypotension, Spinal bupivacaine