Anesthesia is generally classified as general or regional. General anesthesia achieves central neurologic depression, and regional anesthesia is administered directly to block nerve input. The most common forms of regional anesthesia are neuraxial blockade of the subarachnoid space (spinal) or the epidural space surrounding the spinal fluid sac (epidural). Although there are many reasons that surgery is associated with an increased risk of mortality, it is unclear if the type of anesthesia influences this risk. Rodgers and colleagues studied the effect of general or spinal and epidural anesthesia on postoperative mortality and morbidity.
The authors searched electronic databases and the references of key publications to identify randomized, controlled trials involving spinal or epidural anesthesia. Each potential study was reviewed by two researchers, and the authors of the study were contacted to verify data, obtain any unpublished data and identify any additional studies relevant to the project. Of the 158 potential trials identified, 17 were excluded. The remaining 141 trials involved 9,559 patients randomized to general or regional anesthesia.
Within 30 days of randomization, 247 deaths were recorded. The rate of death was 2.1 percent in patients receiving epidural or spinal anesthesia and 3.1 percent in those receiving general anesthesia. This decline of one death per 100 patients in the regional anesthesia groups resulted from reductions in pulmonary embolism, cardiac events, stroke, transfusion requirements, infections and respiratory depression. No difference was demonstrated in mortality between epidural and spinal anesthesia groups, and the type or location of surgery did not influence the result. The odds of deep venous thrombosis were reduced by 44 percent, those of pneumonia by 39 percent and those of respiratory depression by 59 percent in the patients receiving neuraxial blockade. Use of epidural or spinal anesthetic halved transfusion requirements and was associated with a reduction in myocardial infarction and renal failure (see accompanying table).
|Complications||NB (N = 4,871)||No NB (N = 4,688)||Odds reductions|
|Deep venous thrombosis||145||220||44% (10)|
|Pulmonary embolism||30||66||55% (15)|
|Myocardial infarction||45||59||33% (17)|
|Perioperative transfusion >2 units||193||280||50% (10)|
|Postoperative bleeding requiring transfusion||31||69||55% (15)|
|Wound infection||29||33||21% (24)|
|Death from other infective causes||2||10||67% (36)|
|Respiratory depression||26||38||59% (19)|
|Renal failure||18||32||43% (22)|
The authors conclude that neuraxial blockade with spinal or epidural anesthesia significantly reduces postoperative mortality and morbidity. They call for further research to clarify the scope of the benefit and for more widespread use of regional, rather than general, anesthesia.