The role of propofol based total intravenous anaesthesia (TIVA) in reducing pain after surgery

Abstract

Maintenance of general anaesthesia can be achieved with inhalational agents or total intravenous anaesthesia (TIVA) with propofol. Propofol TIVA is associated with advantages such as reduced postoperative nausea and vomiting and smoother recovery. Furthermore, propofol has analgesic properties. Acute postoperative pain is a major clinical problem worldwide and management remains suboptimal. The concepts of multimodal analgesia and procedure specific analgesia were introduced with the aim of improving postoperative pain control. In this thesis, an audit that compared the acute pain service between 1992-1995 and 2009-2012 found no reduction in postoperative pain scores between the 2 periods, although there was reduction in opioid consumption. Propofol TIVA for general anaesthesia may be an additional adjunct to reduce postoperative pain. A review of randomized controlled trials suggested that propofol TIVA may improve postoperative analgesia. However, overall evidence was thin and more procedure specific evidence was needed. In this thesis, a retrospective case-control study was performed for colorectal surgery. Propofol TIVA was associated with less postoperative opioid consumption compared to inhalational anaesthesia, but there were no differences in pain scores. A large-scale retrospective cohort study of 4202 patients across 15 types of surgeries was performed. Propofol TIVA was associated with reduced overall postoperative pain scores and opioid consumption. Subgroup analysis showed that patients with propofol TIVA had lower pain scores and less opioid consumption in hepatobiliary/pancreatic, gynaecological, and upper gastrointestinal surgeries. A prospective randomized controlled trial was then performed for third molar surgery, which was a minor surgery that produced an inflammatory pain model. Propofol TIVA was associated with lower pain scores and better patient satisfaction compared to inhalational sevofurane. Another randomized controlled trial was conducted for hepatectomy, which was a major surgery associated with moderate to severe pain. Contrary to results from the earlier retrospective cohort study, no difference in postoperative analgesia was found. In the clinical studies where propofol TIVA was associated with reduced pain, the degree of pain reduction was small. Clinical significance may be limited. The analgesic mechanism of propofol was studied in the plantar incision model for postoperative pain and the chronic post-ischaemic pain (CPIP) model for complex regional pain syndrome. Inflammation is an important component of CPIP, which should make it relevant to postoperative pain. In the plantar incision model, propofol reduced the spinal dorsal horn expression of EPAC1. In the CPIP model, propofol reduced pain response and upregulated the spinal dorsal horn levels of PTEN. Propofol could provide analgesia by inhibiting EPAC1 and upregulating PTEN. This thesis has provided both clinical and laboratory evidence regarding the use of propofol TIVA for postoperative analgesia. The findings show that propofol TIVA can improve postoperative analgesia. Given that postoperative pain control is challenging, a small pain reduction can still be taken into consideration when choosing between general anaesthetic techniques. Furthermore, propofol TIVA may be a useful analgesic adjunct when given together with other non-opioid analgesic medications as part of multimodal analgesia. The effectiveness of propofol TIVA varied with different surgical procedures: suggesting that it is procedure specific.