Background and rationale
Liver resection is the optimal treatment for patients with primary or metastatic liver malignancies, benign liver tumours, and some biliary diseases
[1–5]. In Canada, over 2,000 patients annually undergo liver resection, predominantly for cancer
. Over the past few decades, improvements in surgical technique, better haemostatic control, and wider indications for liver resection, especially for those with metastatic disease, has resulted in a significant increase in the prevalence of liver resection surgery. There has been an increase of approximately 12% in the number of liver resections performed each year with a cumulative increase over 5 years of more than 60%
Due to the location of the liver and the propensity for bleeding during resection, surgery is typically performed through a large right subcostal incision. The subcostal incision, however, is associated with significant postoperative pain and distress which may result in respiratory complications, delayed mobilization and physiotherapy, and prolonged hospital stay
. Inadequate postoperative pain management is associated with the development of chronic postsurgical pain which is costly to both the patient and society
[9–12]. Intense postoperative pain is a risk factor for the development of chronic postsurgical pain (CPSP)
[9–12]. Prolonged pain after surgery is the result of changes in the peripheral and central nervous system causing amplification, increased sensitivity, and prolongation of pain
. It is estimated that as many as 30% of Canadians who undergo an operation will develop CPSP and the severity of acute postoperative pain is a predictor of its development
. Chronic pain is costly to the patient and society in terms of direct health care expenditures, and indirect costs associated with lost productivity, as well as suffering and disability
. Aggressive and effective early postoperative pain relief may prevent the development of chronic pain
Conventional techniques of postoperative analgesia include epidural catheters, intravenous opioid patient-controlled analgesia, and peripheral nerve blocks
[15–17]. Peripheral nerve blocks - specifically transversus abdominis plane (TAP) blocks - have been described
[18–20]. A modification of the TAP technique which involves surgeon placement of the TAP catheters directly into the open surgical wound (medial open transversus abdominis plane; MOTAP) has been investigated both at Sunnybrook Health Sciences Centre and at the University Health Network – Toronto General Division
Epidural analgesia remains the gold standard for pain control following an abdominal surgical procedure
. However, complications from epidural analgesia include hypotension, bradycardia dural puncture, spinal infection, and rarely, but devastatingly, neurological damage
[23–26]. Furthermore, removal of epidural catheters may provide logistic challenges if patients develop coagulopathy on the basis of liver dysfunction
[27–30]. Given the above risks, many institutions do not routinely insert epidurals for patients undergoing major liver resection.
Intravenous opioid patient-controlled analgesia
Despite the variety of pain-relieving modalities available, postoperative pain following liver surgery is significant and remains a challenge to manage. Opioid analgesia, while effective at rest, fails to provide adequate pain relief associated with movement such as breathing, coughing, ambulation, and gastrointestinal motility
[11, 31]. Moreover, opioids are associated with adverse effects such as nausea, vomiting, constipation, sedation, and respiratory depression
Transversus abdominis plane
Movement-evoked incisional pain accounts for the majority of pain experienced, and the nerves responsible arise from thoracic levels T6 to T10
. These nerves lie in a plane between the internal oblique and transversus abdominis muscles, known as the TAP
[18, 33, 34]. The TAP block involves injecting local anaesthetics into this fascial plane, thereby blocking transmission of the sensory neurons responsible for abdominal surgical pain. Afferent sensory information from these nerves can be blocked by infiltrating local anaesthetic via a surgically placed catheter that runs in the lateral TAP (blocking T8 to T10) and extends into a second adjacent anatomical compartment, the posterior aspect of the rectus sheath (blocking T6 to T8). A variation of the TAP block, the oblique subcostal block, provides sensory blockade for surgical incisions between T6 and T10 dermatomes, including the subcostal or chevron incision used in liver surgery
. A retrospective study of 36 patients demonstrated that ultrasound-guided TAP blocks significantly decreased 24-hour cumulative morphine consumption
. A recent randomized controlled trial demonstrated that TAP blocks and epidural analgesia are equally efficacious in controlling postoperative pain
. However, due to the close proximity to the peritoneum and the highly vascularized liver, single-shot subcostal TAP blocks are quite challenging to perform, even under ultrasound guidance, as evidenced by two cases of liver puncture in a sample of 36 patients
. In small studies, TAP blocks decreased postoperative opioid consumption, nausea, and vomiting, while providing pain control similar to epidural analgesia
. TAP blocks are typically infiltrated using ultrasound guidance at the conclusion of the operation. Preliminary uncontrolled studies and case reports have demonstrated the potential efficacy, safety, and patient satisfaction of TAP catheters
MOTAP technique – modification of the transversus abdominis plane technique
We have recently developed a modification of the TAP technique for regional analgesia following subcostal incisions termed MOTAP catheter placement. This technique involves surgical placement of the catheter under direct vision. During subcostal incision these muscular planes are clearly visible, allowing more confident insertion of a catheter directly into the correct plane
. In a pilot study, 22 fit adults undergoing donor hepatectomies received TAP catheters at the end of surgery. The patients received the first dose of bupivacaine (0.2 cm3/kg 0.125%) at the end of surgery and this regimen was repeated every 12 hours until postoperative day 3. We compared postoperative pain scores and opioid use to historical controls and found a significant (P < 0.05) difference in cumulative postoperative opioid (hydromorphone) consumption at 48 hours (mean ± SD: 20.8 ± 15.8 mg for MOTAP catheters vs 39.1 ± 25.1 mg for patient-controlled analgesia (PCA)).
To assess the impact of MOTAP catheters plus intravenous, patient-controlled analgesia (IV PCA) compared to the standard of care (that is, IV PCA alone) on opioid consumption in patients undergoing hepatic resection requiring a subcostal incision.
To assess the effect of MOTAP catheters on:
Postoperative pain intensity.
Opioid-related adverse effects, including nausea, vomiting, pruritus, sedation, and postoperative ileus.
Time to ambulation, duration of hospital stay and reduced postoperative pain disability.
Post-surgical complications (for example, pneumonia).
Incidence and intensity of chronic postsurgical pain.