Conventional landmark palpation vs. preprocedural ultrasound for neuraxial analgesia and anaesthesia in obstetrics – a systematic review and meta-analysis with trial sequential analyses

Summary by Kaylie Young MD, 5.14.23
https://associationofanaesthetists-publications.onlinelibrary.wiley.com/doi/10.1111/anae.15255


Take home message:

  • Preprocedural ultrasound increases first pass success rate without increasing time taken to perform the procedure. 

  • Preprocedural ultrasound shows increased benefit in those with predicted neuraxial procedure difficulty.

  • Preprocedural ultrasound decreases complications, including back pain and headache. 

  • Preprocedural ultrasound for neuraxial anesthesia in obstetric patients is recommended and should be considered standard of care.


Summary: To examine the efficacy, time taken, and safety of neuraxial blockade in pregnant patients with the assistance of preprocedural ultrasound in comparison with landmark techniques. 


Background: Recently, multiple meta-analyses of safety and efficacy of neuraxial blockade in obstetric and non-obstetric patients have been done. This meta-analysis looks to specifically examine obstetric patients as well as time taken to perform the procedure.


Study design: Identification of randomized control trials fitting the inclusion criteria. For outcomes, the mean difference was calculated using the inverse-variance method and the risk ratio with the Mantel–Haenszel method.


Methods:

  • Finding trials for meta-analysis: systemic search of electronic databases, Central, CINAHL, Embase, Global Health, MEDLINE, Scopus and Web of Science using keywords such as neuraxial analgesia, anesthesia, and ultrasound.

  • Inclusion criteria: 1) Randomized control trials including pregnant women having combined spinal-epidural or spinal or epidural with pre-procedural ultrasound as the intervention and conventional landmark palpation as the comparator. 2) Published in the english language.

  • Exclusion criteria: Two authors individually reviewed titles and abstracts found by the systemic search and reviewed full texts of those eligible for the meta-analysis based on the inclusion criteria. 


Primary Outcomes: 

1) First pass success rate (skin puncture with no redirection). 

2) Total time taken for needle insertion point identification and performance of neuraxial procedure. 


Secondary Outcomes: “first intervertebral space success rate; first skin puncture success rate; number of attempted intervertebral spaces; need to attempt more than one intervertebral space; number of skin punctures; need for three or more skin punctures; number of needle redirections; need for three or more needle redirections; total number of skin punctures and needle redirections; need for three or more skin punctures and needle redirections; preprocedural predicted ultrasound distance compared with real needle to target distance; number of attempts required to pass the epidural catheter; need to call for help; time taken for identification of exact point of needle insertion; time taken for performance of neuraxial procedure; technical inability to site neuraxial block; incidence of asymmetrical or patchy neuraxial blockade; failure rate of analgesia or anesthesia after neuraxial injection; rate of inadequate dermatomal level of blockade; need for epidural top up before skin incision, supplemental analgesia or conversion to general anesthesia; incidence of paraesthesia, ‘bloody tap’ or vascular cannulation, dural puncture, post-dural puncture headache, postpartum headache, postpartum back pain and neurological sequelae; need for epidural blood patch; patient-reported pain during performance of neuraxial procedure and in labor or cesarean section; and patient satisfaction.”


Results:

  • 4978 records identified by search. Only 22 randomized control trials met inclusion criteria. 

  • Included trials comprised of 2462 patients: 1230 had preprocedural ultrasound and 1232 had conventional landmark palpation

  • First-pass success rate was reported in 1253 patients. It was increased by a risk ratio (95%CI) of 1.46 (1.16–1.82), p = 0.001, I2 = 72% with ultrasound compared with landmark methods 

  • Time taken for the identification of the needle insertion point and the performance of the neuraxial procedure was reported in 709 patients. No difference was demonstrated between ultrasound and landmark methods (p < 0.00001, I2 = 93%).

  • For secondary outcomes: “Relative to palpation of anatomical landmarks, preprocedural ultrasound further decreased the incidence of complications, including: technical inability to site the neuraxial block; failure of analgesia or anaesthesia; ‘bloody tap’ or vascular cannulation; and postpartum back pain and headache.”


Discussion/conclusion:

  • Preprocedural ultrasound improves efficacy, including the first pass success rate, and decreases the risk of complications without increasing overall time taken to perform the procedure from identification of needle insertion point to finishing the procedure. However, the two primary outcomes were rated as low and very low on quality of evidence due to serious limitations, inconsistency, and imprecision.

  • First pass success rate and time taken to perform the procedure were not affected by the experience of the sonographer.