It has always been clear that choice of anesthetic technique has some effect on the success of in-vitro fertilization. For example, most in-vitro fertilization programs have strict protocols as to which anesthetic medications should be used for anesthesia and which should be avoided. Some of these protocols are based on study results, while others are more of a theoretical concern or include drugs to be avoided because their effect is unknown. Examples include the avoidance of local anesthetics, nitrous oxide, non-steroidal anti-inflammatory drugs like ketorolac, etc.

A recent study from Massachusetts General Hospital shows that spinal anesthesia may be superior to general anesthesia for oocyte, or egg, retrieval in terms of pregnancy rates as well as patient satisfaction. While the study only included twenty-five women, those who chose to have spinal anesthesia had a fifty percent overall pregnancy rate versus a thirty-three percent rate in those patients who chose general anesthesia. The results were statistically significant despite the small sample size.

While both groups reported high levels of satisfaction rates with their anesthesia, the patients choosing spinal anesthesia all said that they would repeat that choice in the future. Not a single patient said that they would "rather have been asleep" or have had general anesthesia. The patients having spinal anesthesia also required less pain medication after the operation than the patients receiving general anesthesia. The authors of the study commented that spinal anesthesia was associated with fewer side effects, whereas general anesthesia can cause prolonged sleepiness, nausea, and/or vomiting after the operation.

It is postulated that this effect may have something to do with the fact that general anesthetics enter the bloodstream of the patient relatively quickly. Therefore, the medications do reach the ovaries of the patient during the first few minutes of the procedure. On the other hand, spinal anesthesia leads to very low levels of medication in the bloodstream - and these levels are achieved very slowly. This may mean that levels of medication in the ovaries are negligible at the time of egg retrieval.

Interestingly, some centers perform these oocyte retrieval procedures with neither general nor spinal anesthesia. Instead, a form of anesthesia called Monitored Anesthesia Care (MAC) is used - basically the patient is kept comfortable with sedation while the procedure is done. Many of these centers report comparable pregnancy rates (40-50%) using this technique. A study comparing Monitored Anesthesia Care to other forms of anesthesia has not yet been done and it remains to be seen how the data might compare.