Dorsal penile nerve block for circumcision in pediatric patients: A prospective, observer-blinded, randomized controlled clinical trial for the comparison of ultrasound-guided vs landmark technique.

Ultrasound-guided dorsal penile nerve block (USS DPNB) may be superior to landmark DPNB by reducing post-operative pain scores (Faraoni et al 2010, 40 patients) and reducing the requirement for post-operative opiates (O’Sullivan et al 2011, 66 patients). This observer blinded, randomised controlled trial examined 310 prepubertal patients (ASA 1-2, 52 weeks post conception to 11 years) comparing: USS DPNB using an ‘out of plane’ approach and Landmark DPNB using Dalen’s technique. For both techniques 0.1ml/kg of levobupivacaine 0.5% was injected bilaterally using a 22g Epican® needle by a single experienced anaesthesiologist in a Belgium hospital between 2012 and 2016. A standard anaesthetic technique was used consisting of 8% sevoflurane gas induction followed by a 2mg/kg propofol bolus, placement of a laryngeal mask and 2% sevoflurane maintenance.
a) Primary outcome: the difference in requirement of piritramide (a synthetic opiate) postoperatively as triggered by the Objective Pain Scale >3 was not statistically significant between the two groups (USS 47% vs landmark 38%; 95% CI 0.09 [0.2 to 0.02], P = 0.135).
b) Secondary outcomes: the median ‘anaesthesia induction time’ was two minutes longer in the USS DPNB group (median time [IQR]: 13 mins [11;15] vs landmark 11mins [9;13], P <0.001). Other outcomes were not significantly different including: the requirement for fentanyl intraoperatively; the cumulative dose of post-operative opiates; the requirement for paracetamol and ibuprofen in the first 24 hours post-operatively; incidence of nausea and vomiting; and time to discharge.
a) No local anaesthetic was injected at the ventral base of the penis, which has been associated with improved analgesia during circumcision (Serour et al 1994) by blocking sensory branches of the pudendal nerve.
b) Patients were administered post-operative opiates based on the Objective Pain Scale, which is a behavioural scale designed for non-verbal patients (<6 years). Patients up to 11 years were included in the study, and for older patients a verbal pain scale is often recommended.
c) This cohort is at risk of emergence delirium. The use of sevoflurane and omission of routine opiates increases this risk. The investigators performed a sub-analysis of opiate administration >15 minutes post extubation (USS 23% versus landmark 24%) in an attempt to address this confounder.
d) Sample size and power was calculated from an ‘historic group’ of 50 patients who had received landmark DPNB for circumcision, which showed that 10% required post-operative piritramide. Sample size was calculated on the hypothesis that USS DPNB would reduce this rate to 2%, but it is unclear how this estimate was made. A larger sample size would be required to examine a smaller difference. The rate of post-operative opiate use was much higher in both arms of the study (USS 47%, landmark 38%) compared to the ‘historic group,’ which may reflect that the ‘historic group’ routinely received fentanyl 1mcg/kg intraoperatively, and post-operative opiate administration was not administered by the Objective Pain Scale. The study was not powered to examine the secondary outcomes, which should be interpreted with caution.
e) Single anaesthetic operator: this causes the potential for performance bias. Furthermore, it does not address the important clinical question of whether USS improves the performance of less experienced operators. Variation in surgical operators was not discussed.

Take home messages. When performed by an experienced practitioner USS DPNB:
a) may not be superior to landmark DPNB
b) takes a few minutes longer to perform

Reviewed by: Dr Adam Keys