"Continuous Thoracic Epidural Analgesia Versus Continuous Erector Spinae Plane Block for Postoperative Analgesia in Patients Undergoing Adult Living Donar Open Hepatectomies."

Thoracic epidural analgesia (TEA) is commonly used for pain management in donor hepatectomies. TEA reduces activation of the sympathetic outflow, surgical stress response, and pain-associated tachycardia and hypertension which can cause perioperative myocardial ischemia. TEA decreases stress-induced gastrointestinal disruption, immunosuppression, and decreases postoperative opioid requirement. TEA promotes expiratory intercostal and abdominal muscle tone and facilitates diaphragmatic excursion thus reduce the risks of atelectasis, pneumonia, and respiratory failure. However, TEA has its own drawbacks, e.g. hypotension caused by the inhibition of the sympathetic outflow, which can be associated with the administration of large amounts of crystalloids and colloids. Other complications may include failure to produce analgesia in 20% of patients3, intravascular cannulation leading to local anesthetic toxicity, unintentional dural punctures, paraesthesia, post-operative coagulopathies, epidural abscess, and epidural hematomas resulting in paraplegia1, 3. Considering these merits and demerits, TEA is the widely accepted choice for postoperative analgesia in living related donor hepatectomies1, 3,4, 5.

Erector spinae plane block (ESPB) is a novel ultrasound-guided regional anesthesia technique described in 2016 6 for the management of thoracic and abdominal pain. Ultrasound guidance is used to inject a local anesthetic in the interfacial plane between the erector spinae muscle and the associated transverse process of the spine. The mechanism of action is by the spread of local anesthetic anteriorly to the dorsal and ventral rami of the thoracic and abdominal spinal nerves 7. The absence of blood vessels in this vicinity shows the usefulness of this technique in the patients, who are prone to coagulopathies making it safer with lesser expertise, and with less procedural complications 8. The ESPB is an avascular plane block therefore, it results in lower plasma volumes rise due to reduced uptake of the local anesthetic by plasma hence the duration of action of local anesthetic is long. An ESPB at T5 level is sufficient to have a unilateral multi-dermatomes sensory block ranging from T1 to L3 level10 when used as a continuous block. Various case reports demonstrate its efficacy in a wide spectrum of specialities like acute and chronic pain management, thoraco-abdominal surgeries, neuropathic and post-traumatic pain 4, 7, 8,9 , 10. A comparison of continuous epidural versus single shot intrathecal morphine was made and assessed the quality of analgesia by a visual analog scale (VAS) and the additional IV analgesic requirements were 56% in cases of epidural 11 used for sample size calculation.

However, no randomized control study has been performed to compare the efficacy of a continuous ESPB with that of a continuous TEA for living related donor hepatectomies. Thus the aim of this study is to compare the postoperative analgesic efficacy and adverse effects of continuous ESPB to that of a continuous TEA in patients undergoing adult living donor hepatectomies. Investigators have hypothesized that continuous ESPB would provide better postoperative analgesia with fewer adverse effects. The primary outcome is post-operative pain scores using the visual analog scale (V.A.S) for pain at rest and at maximal inspiration during the post-operative period at PACU, 1, 6, 12, 24 and 48 hours. The secondary outcomes include lung incentive spirometry volumes, the dosage of adjunct nalbuphine used, hypotension, tachycardia, post-operative coagulopathy, early mobilization and discharge from surgical I.C.U (S.I.C.U).

Methodology After approval from the institutional and ethical review board and written informed consent, patients were randomized into either the TEA group or the ESPB group using the sealed enveloped method.

Study design The study will be a single-blinded, prospective, comparative, randomized control trial. The participants will be assigned to one of two groups; Group A will include patients receiving continuous TEA, whilst Group B will include patients receiving continuous ESPB. Both groups will receive their respective intervention after induction with standard general anesthesia.