Real-Time Ultrasound Improves Accuracy of Caudal Block in Children.
One in five caudal blocks are outside the caudal space in a high-volume paediatric centre
Study type: A single-blinded prospective observational trial using ultrasound to assess whether local anaesthetic was injected into the caudal space using the palpation method in 109 children up to 7 years of age.
Methods: Caudal injections were performed using landmark techniques in 109 patients. One ml/kg of 0.2% Ropivacaine was injected. An ultrasonographer confirmed whether the first 0.5 – 1 ml of injectate was in the epidural space and, guided the anaesthetist into the space for the remainder of the injection if this was not the case. The sample size was calculated by examining historical data. An 18.6% failure rate was calculated using reasonable criteria. Median age was approximately 1 year old and weight approximately 10 kg. Skill levels varied from student anaesthetic nurses to attending (consultant). Three types of needles were employed.
Findings: Only 86 of 109 (79%) of initial injections were confirmed to be in the epidural space. There was no association between proceduralist skill level, patient age or needle type and success rates of initial injection. In 2 cases the provider thought that the injectate was likely outside of the caudal epidural space when ultrasound demonstrated correct location. Four of 98 patients with ultrasound confirmed injections and appropriate conditions (adequate time from injection & < 1 MAC Et IAA) had heart rate increases of more than 5% at incision.
Take Home Message
This study confirms previous publications’ findings that expert providers in high volume paediatric institutions overestimate success rates for caudal anaesthesia. It also confirms the common clinical impression that heart rate occasionally rises with correctly performed blocks. The study was not powered to detect differences with provider level or needle type. That said, anaesthetists practicing caudal blocks using landmark techniques should probably be saying one in five fail rather than one in ten. Although not statistically satisfying, morphine consumption rates in this group where ultrasound determined final injectate location were reduced by two thirds when compared with historical controls. This study suggests that ultrasound guidance may well be a skill worth acquiring in caudal blocks.
Reviewed by: Dr Chris Brasher