Transversus abdominis plane block as sole anaesthetic technique for inguinal hernia repair in two patients having complex medical conditions

Abstract

Sir, Transversus abdominis plane (TAP) block has been used as a sole anaesthetic technique for the patients with multiple co-morbidities presenting for emergency laparotomy.[1,2] We share our experience of using TAP block for the surgical anaesthesia in two patients scheduled for inguinal hernioplasty who had associated complex medical conditions. First patient was a 52-year-old male, known case of congenitally corrected transposition of great arteries (CCTGA) associated with severe pulmonary stenosis and a pressure gradient of 64 mm Hg, large non-restrictive ventricular septal defect (VSD) and right ventricular (i.e., physiologic left ventricle) dysfunction. He was stable on treatment with tablet torsemide. Second case was a 54-year-old male known case of Takayasu's arteritis (TA) and hypertension on treatment with tablet metoprolol and losartan. The patient had the history of claudication and weakness of left upper limb. The peripheral pulses in left upper limb were feeble and blood pressure (B.P) was lower compared to right upper limb (112/70 mm Hg vs. 172/73 mm Hg). For surgery, ultrasound guided (USG) TAP block was administered in both cases using in-plane posterior approach with 20 ml of 0.5% bupivacaine and 10 ml of 2% lignocaine. For visceral analgesia, the TAP block was supplemented with infusions of dexmedetomidine at the loading dose of 1 μg/kg over 10 min followed by 0.5-0.6 μg/kg/min infusion and fentanyl at 75-100 μg/h, respectively, in the first and the second case. In the first patient, T10 -L1 dermatomes were blocked whereas in second patient L1 was spared; only T10 -T12 blockade was achieved as checked by pin prick. The incision line was infiltrated with 2% lignocaine in the second case before surgery. The anaesthetic monitoring in both cases included continuous electrocardiogram, continuous invasive B.P monitoring, pulse oximetry, and temperature. The intraoperative vital parameters were stable and surgery was completed uneventfully in both cases. CCTGA is an uncommon congenital cardiac anomaly characterized by TGA along with the inversion of both ventricles and thus there is both atrio-ventricular and ventriculo-great vessel discordance. The anaesthetic haemodynamic goals in these cases are to maintain systemic vascular resistance (SVR) to avoid right to left shunt by VSD and to preserve myocardial contractility.[3] TA involves a focal stenotic process in the aorta and proximal segment of its main branches. In our second case, though angiography was not done, based on the history of claudication and findings of feeble pulses and decreased B.P. in left arm compared to right is suggestive of stenotic area to be in the arch of aorta. These patients may not tolerate the sudden fall in SVR as they have compromised regional circulation and hence similar to the first patient our intraoperative haemodynamic goal was to maintain SVR. We decided to use USG TAP block in both cases as being an abdominal field, it holds the promising advantage of maintaining the haemodynamics of patients, which are altered in general or neuraxial anaesthesia and additionally provides an excellent postoperative analgesia for 24-48 h. We chose dexmedetomidine infusion in the first patient as it has the combination of analgesic, sedative, and anxiolytic properties with the preservation of respiratory functions. There are 3 main issues which need consideration while using TAP block as a sole anaesthetic modality for surgery. First, TAP block covers only the somatic component of surgical pain; for visceral pain analgesia has to be supplemented with other analgesic agents hence it cannot be a sole anaesthetic technique. Second, the extent of dermatomal block provided by TAP block is uncertain. Both pinprick using blunt needle and cold disinfectant swabs can be used to assess dermatomal extent of sensory blockade. Lee et al.[3] reported that posterior approach produced a median sensory block of three dermatomal segments, the most cephalad being T10. We found the L1 dermatome to be spared in the second case despite using 30 ml of drug for block. Since the incision for inguinal hernia repair lies over T12 -L1 segments, additional infiltration of local anaesthetics (L.A) was required before surgery. Niraj et al.[4] also observed that posterior approach TAP block usually spares L1 segment. Another disadvantage of TAP block is potential to produce L.A. toxicity since large volumes of L.A. are used. There are case reports[5] of cardiac arrests due to L.A. systemic toxicity following TAP block. Therefore the volume of drug used should be carefully determined and the patient should be observed for at least 45 min after TAP block institution during intraoperative and postoperative period. Financial support and sponsorship Nil. Conflicts of interest There are no conflicts of interest.