The number of deaths associated with general anesthesia used in childbirth has dropped in recent years, which is likely a result of better drugs and more sophisticated procedures. But researchers are still puzzling over the fact that deaths due to regional anesthesia (for example, epidurals) have risen slightly over the last several years.

The mortality rate for general anesthesia during a c-section dropped considerably…However, over the same periods of time, the rate of regional anesthesia (epidural, spinal block) rose from 2.5 to 3.8 per million regional anesthetics.

Researchers reviewed data from 1979 to 2002, looking at how many women died from any kind of anesthesia during childbirth, and how many died from each type of anesthesia independently. They found that the average number of all anesthesia-related deaths dropped from 2.9 deaths per 1 million births between 1979-1990 to 1.2 deaths in 1 million births over the years 1991-2002. This change represents a decrease of 59%, which is a significant drop.

The mortality rate for general anesthesia during a c-section dropped considerably, from 16.8 to 6.5 deaths per million between the years 1991-1996 and 1997-2002. However, over the same periods of time, the rate of regional anesthesia (epidural, spinal block) rose from 2.5 to 3.8 per million regional anesthetics.

The authors also write that as recently as the 70s and 80s, "17 women died of general anesthesia for every one who died from regional anesthesia." But by the 1990s, this ratio had dropped to six-to-one, a much better statistic.

The causes of death were different for general vs. regional anesthesia. The leading causes of death with general anesthesia, accounting for two-thirds of this death rate, were "intubation failure" or problems with induction. On the other hand, for region anesthesia, the causes were more evenly divided between problems with the epidural or spinal block procedures, respiratory failure, and reactions to the medication used.

Why the death rate – as well as other problems – associated with regional anesthesia has increased in recent years is still a bit of a mystery. The authors of the paper say that there are a variety of reported complications, from cardiac and respiratory arrest to neurological problems, including brain damage and nerve injury. Devising a better system to report and track complications may help the medical community understand why the statistics regarding childbirth shift over the years. This way, write the authors, all complications outside of death, including "bad outcome[s] or near miss[es]’" are still acknowledged and addressed.

The research was carried out by researchers at the University of Colorado, Aurora, and published in the December 20, 2010 issue of Obstetrics and Gynecology.