Friday, January 30, 2015

Could Spinal be the "Best" Anesthetic for Oocyte Retrieval?

image from national academies press
 Copyright © 2006 Massachusetts Medical Society
In investigating if spinal anesthesia might be the best anestheticand analgesic approach for oocyte retrieval, I found a recent and complete review. This Cochrane review was not designed to make a conclusion regarding spinal anesthesia versus procedural sedation/general anesthesia for oocyte retrieval, but provides a good overview of the limited literature, concluding only that the use of more than one pain relief modality improves patient comfort.  My informal on-line survey of information for patients provided by fertility clinics suggests TIVA incorporating propofol as procedural sedation/general anesthesia is likely the most common method employed for oocyte retrieval in the US.  

Outside of this review, several prospective1,2,3 and retrospective4 studies have found an association between spinal anesthesia and improved outcomes either in the process of anesthesia care3, or in ultimate pregnancy outcomes1,2,4.  As for other regio-local anesthetics, paracervical block has been associated with better pain control during these procedures11 and epidural anesthesia11 and topical EMLA cream12 has been associated with improved pregnancy outcomes. In some of these clinical trials the distinction between procedural sedation and general anesthesia is not clear or inhalational anesthesia was compared to spinal anesthesia.  As has been shown for regional anesthesia and major surgical procedures, the use of spinal anesthesia for oocyte retrieval attenuates hormonal stress responses5.  Several studies have compared the effectiveness of low dose spinals using different doses, baricities, and the addition of fentanyl6-9.  All spinal doses that were studied showed a high success rate with 2-3 hour injection to discharge times.  No comparisons using 2-chloroprocaine were found but doses as low as 3.75 mg of hyperbaric bupivacaine with fentanyl were studied. 

In the absence of a dose ranging study, I suspect that the success of lowering the dose of ultra-low dose spinal anesthesia to speed discharge after oocyte retrieval may be limited y two factors.  One factor is that during oocyte retrieval pain is not limited to a somatic area but is visceral as well.  Another is that good surgical conditions are required to  improve procedural success for this usually bilateral procedure (where success is complete retrieval from two ovaries quickly).  Taken together this may mean that a "walking" or "unilateral" spinal where local anesthetic is administered in extremely small doses or directed away from motor nerves by baricity may not be adequate.   

However, the argument for the utility of spinal anesthesia rests in the idea that spinal anesthesia is well suited to provide the dense analgesia, procedural success, and very best pregnancy outcome important to this population of patients and their reproductive gynecologist.  Though perhaps commonly used, the provision of anxiolysis and unconsciousness-- provided by propofol-- may be of less importance. Could the attenuation of hormonal responses by regional anesthesia during oocyte retrieval be beneficial to pregnancy outcomes in the same way this attenuation is hypothesized to improve outcomes after major cancer and orthopedic surgeries?  While this remains speculation, in nine months time--don't these same patients often choose epidural analgesia for labor or spinal anesthesia for C-section for some of the same patient-centered reasons that spinal anesthesia might make sense here as well?


1. Toon H et al. Is Spinal Anesthesia Preferable to General Anesthesia for Oocyte Retrieval? Anesthesiology 2000 abstract A24. (not published as a full study)
2. Azmude A et al. Pregnancy Outcome Using General Anesthesia Versus Spinal Anesthesia forIn Vitro Fertilization  Anesthesiology and Pain Medicine. 2013 September; 3:239-42.
5. Guasch E et al. [Comparison of 4 anesthetic techniques for in vitro fertilization]. Rev Esp Anestesiol Reanim. 2005;52:9-18. Spanish.
6. Manica VS et al. Anesthesia for in vitro fertilization: a comparison of 1.5% and 5% spinal lidocaine for ultrasonically guided oocyte retrieval. Anesth Analg. 1993;77:453-6.
7. Omi S et al. [Spinal anesthesia with 2% plain lidocaine for ultrasonically guided vaginal oocyte retrieval].  Masui. 1996;45:1507-10. Japanese.
8. Martin R et al. Anesthesia for in vitro fertilization: the addition of fentanyl to 1.5% lidocaine.  Anesth Analg. 1999;88:523-6.
9. Tsen LC et al. Intrathecal low-dose bupivacaine versus lidocaine for in vitro fertilization procedures. Reg Anesth Pain Med. 2001;26:52-6.

No comments:

Post a Comment