Caudal blocks safe but do not improve pain scores following RARP
While caudal block does not pose serious safety threats, it also does not seem to significantly improve pain control or reduce analgesic use in patients following robot-assisted laparoscopic radical prostatectomy (RARP), a recent Singapore study has shown.
Median pain scores, as measured by the operating theatre and ward nurses, were statistically comparable between those who received a caudal block and controls (recovery room scores: 3 vs 2; p=0.34). [Asian J Urol 2018;5:122-126]
This trend in median pain scores persisted until 6 (2 vs 2; p=0.94), 12 (0 vs 0; p=0.62), 24 (0 vs 1; p=0.58), 48 (0 vs 1; p=0.36) and 72 (0 vs 0; p=0.78) hours after the surgery.
The absence of a beneficial effect of caudal block on pain scores was confirmed by the patterns in opioid usage in the recovery room, which was statistically similar between the two groups (caudal vs control: 4.3±1.3 vs 2.8±1.2 mg; p=0.41).
Notably, participants who received the caudal block were given nonsignificantly higher doses of opioid analgesics at all time points tested: 24 hours (2.3±1.4 vs 0 mg; p=0.11), 48 hours (1.3±1.0 vs 0.3±0.3 mg; p=0.35) and 72 hours (0.3±0.3 vs 0 mg; p=0.32) hours postoperation.
Paracetamol usage was likewise comparable between the caudal block and control groups at all time points (recovery room: 300.0±105.1 vs 250.0±99.3 mg; p=0.76; 24 hours: 2,150.0±232.6 vs 1,950.0±256.2 mg; p=0.57; 48 hours: 1,850.0±334.6 vs 1,927.5±271.4 mg; p=0.86; 72 hours: 650.0±181.7 vs 527.7±233.6 mg; p=0.68).
No cases of complications related to the administration of caudal block were reported; clinical success was achieved in all patients in the caudal block group. Opioid-related adverse events were also absent in the whole study cohort.
The findings of the present study agree with that of a previous Chicago retrospective study, which showed no elevated risk of complications following caudal blocks in children. However, the treatment also appeared to have no comparative advantage over standard analgesia in terms of improving pain scores. [Anesth Analg 2015;120:151-156]
This may have been due to the study having insufficient statistical power to detect the impact of caudal block on postoperative pain, given that the median pain scores within the first 24 hours indicated that participants had only mild pain, according to researchers.
“This study revealed low pain scores throughout the postoperative recovery. It was likely that the efficacy of caudal block was overestimated, which, on the contrary, underpowered the study given its small cohort of 40 patients,” said researchers.
In obtaining the above data, researchers randomized 40 consecutive RARP patients to receive either postoperative caudal block with analgesia (n=20) or analgesia alone (controls; n=20). Standard analgesia included opioids and oral paracetamol. Patients were recruited from the Singapore General Hospital.
Despite its prospective and randomized design, some study limitations are worth noting. Among them is the failure to standardize the method and timing of pain assessments. These may have led to biases and inaccuracies in pain measurements.
Therefore, while the study has shown no appreciable safety concerns for caudal block, further large-scale studies with more objective pain assessments are required to conclusively determine if caudal blocks have a beneficial effect on postoperative pain.