TAP block vs. intrathecal morphine – which is better for c-section?

‘The analgesic effects of intrathecal morphine in comparison with ultrasound- guided transverse abdominis  plane block after caesarean section: a randomised controlled trial at a Ugandan regional referral hospital’ Kwikiriza A, et al. Anaesthesia 2019, 74: 167-173 

Background

  • Both transversus abdominis plane block and intrathecal morphine may produce prolonged postoperative analgesia, but the respective clinical outcomes of these anaesthetic techniques in resource-limited settings are not well described.
  • This study was performed to compare these two methods of postoperative pain control and find out which was better for the patients in resource-limited setting, and to allow them to develop robust protocols for analgesia in our institution that could be more widely applied.

Methods

  • Prospective randomised study 
  • Inclusion criteria: between 15 and 49 years old, ASA 1 or 2, spinal anaesthetic without sedation, uncomplicated LSCS, able to give informed consent 
  • Consecutive sampling to recruit following decision to LSCS
  • Patients blinded to study allocation. Blocks done by clinical investigator
  • Spinal anaesthetic with or without preservative free morphine
  • Post-op, in recovery room, dermatomal level of spinal block assessed using blunt pin
  • Pain scores assessed – before block, before discharge from recovery and in ward using numerical rating scale
  • Intrathecal morphine group received sham block and the TAP block group received B/L TAP block( 15 ml each side of 0.25% bupivacaine with 1:200,000 adrenaline
  • All patients – Paracetamol 1g and Diclofenac 50 mg at the time of block and at 8,16 and 24 hrs post-op
  • Reviewed by research assistant – qualified midwife who is blinded to group assignment collected data at 8, 26 and 24 hours
  • Pain levels – rest, on coughing and on movement (numerical rating score) 
  • Side effects – nausea, vomiting, respiratory depression, sedation and  pruritus noted
  • For breakthrough pain – rescue analgesia – rectal Diclofenac 100 mg

Results

  • For statistical power of 80% and type 1 error of 5%- 63 PST each group needed – to allow dropout 65 PST each group recruited
  • Between group and within group differences in numerical rating scores analysed using repeated measures ANOVA
  • P value < 0.05- statically significant 
  • Statistically significant low pain score in TAP block group of patients only in 24 hrs during movement. No statistically significant different in pain scores between groups in the 8 and 16 hours period, between side effects, ambulation and patient satisfaction scores

Discussion

  • Primary Outcome: Clinically similar for both groups, although pain scores statistically lower in rest and movement at 24 hr with TAP block
  • Incidence of iatrogenic side effects – low both groups
  • Satisfaction scores – good in both groups

Rescue Diclofenac PR- requested more frequently both groups at 16 and 24 hrs

Overall paper analysis/review

  • It was discussed that this study cannot be compared or applied to our current practise in the developed countries with available resources. 
  • We routinely use diamorphine intrathecally and do not have preservative free morphine
  • But the practice of TAP block in post – caesarean patients who had GA can be encouraged with these results. 

Summary by Dr Theanu Kasianandan

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