Comparison Of Two Different Doses Of Intrathecal Morphine On Postoperative Analgesia In Renal Transplant Recipients. A Non-Inferiority Randomised Controlled Trial.

Adequate pain control is an essential aspect of perioperative care. Poor pain control can lead to profound agitation, sympathetic overactivity like tachycardia and hypertension, and a higher risk of cardiovascular and pulmonary complications. However, pain management can be challenging secondary to the higher burden of comorbid disease and altered pharmacokinetics due to renal failure in this patient population. The optimal analgesic strategy for kidney transplant patients is not clearly defined. Pain control for kidney transplantation is achieved by using intravenous (IV) opioid medications, with a preference for opioids with minimal renal excretion for either the original compound or its metabolites. Additional approaches to pain management include local anaesthetic wound infiltration, transversus abdominis plane (TAP), and epidural analgesia. The use of intrathecal opioids is also a well-established pain management option for managing postoperative pain in major abdominal surgeries.It has also shown effectiveness in living donors undergoing liver transplantation. The significant benefits of intrathecal hydrophilic opioids over i.v. administration are believed to be due to their higher potency and prolonged action due to the low CSF distribution volume and remarkably slow diffusion. Single-shot intrathecal morphine has also been accepted in Enhanced Recovery After Surgery (ERAS) protocols due to its lower rate of technical failure. In addition, its use also ameliorates the need for patient-controlled analgesia (PCA) pump care and catheter care. These benefits make it an effective pain control strategy in ERAS settings. However, the adverse effects reported are pruritus, nausea, and late respiratory depression. Meylan and colleagues21 performed a meta-analysis with predominant studies related to cardiac surgery, which found higher rates of pruritus and respiratory depression. However, a wide range of dosages were used by the included studies. Gehling and Tryba, in their study, found a dose dependent effect for respiratory depression with a cut-off of 300 micrograms of intrathecal morphine. Koning et al. in their meta-analysis on the use of intrathecal opioids in major abdominal surgeries, recommended the use of dosages less than 500 micrograms intrathecally. However, low-dose intrathecal morphine is suggested as a reliable and cost effective regional anaesthesia option. We aimed to define better define the duration and effectiveness of ITM for postoperative pain control in the setting of the established ERAS protocol for kidney transplant surgeries. We hypothesized that in the setting of the ERAS pathway, including multimodal analgesia, 200 micrograms of intrathecal morphine will provide a non-inferior duration of pain control when compared to 400 micrograms of ITM.