Ultrasound guided Transversus Abdominis Plane block through surgical wound.

Sir,

A 47-year-old super obese (body mass index >50 kg/m2) male weighing approximately 295 kg, breathless in the supine position, presented for laparoscopic sleeve resection. As laparoscopic instruments with adequate length to reach the abdominal cavity were unavailable, he was scheduled for panniculectomy with vacuum-assisted closure (VAC) initially.

Central venous and arterial lines were inserted under ultrasonic guidance on the day of surgery, but we failed to administer epidural or transversus abdominis plane (TAP) block as thickness of adipose tissue itself was >15 cm and deeper structures could not be visualised. Hence, general anaesthesia was administered following awake fibreoptic intubation in the lateral position. The abdominal wall was lifted up with the help of hooks (run through the anterior abdominal wall) hung from a steel frame making mechanical ventilation possible in the supine position. Through a lower transverse abdominal incision 20 kg adipose tissue was excised and VAC therapy was initiated. At the end of surgery, patient was extubated.

On 3rd day, patient had tachypnoea (respiratory rate 30/min) oxygen saturation (SpO2) of 90–94% and oliguria with elevated serum creatinine. Since he was haemodynamically stable, he was posted for closure of surgical wound or reapplication of VAC (if there was infection). In the theatre after removing surgical dressings, high-frequency (13–6 MHz) linear ultrasound probe was directly placed over the wound under aseptic precautions with povidone iodine 10% solution as an acoustic couplant which also reduced chance of infection. 60 ml of 1% lignocaine with 1/100,000 adrenaline was injected in the plane between the internal oblique and transversus abdominis muscles using 23 gauge spinal needle on each side keeping the patient on lateral sides [Figure 1]. Injections were made at a depth of 4 cm from the surface, just anterior to mid-axillary line. Thickness of the tissue probably indicated possible oedema secondary to incision and surgical handling. Analgesia was adequate, debridement with reapplication of VAC was performed. The patient came for repeated procedures thrice in 2 weeks and was managed under TAP block using the same technique. Placing bilateral catheters for subsequent blocks was not considered, as catheter through a wound could potentially be a path for infections. The patient unfortunately succumbed to an acute coronary event 4 weeks after surgery.

Figure 1

TAP block being given through the surgical wound

Morbid obesity commonly results in derangements in most organ systems and is often associated with increased mortality and morbidity. Transversus abdominis plane block provides reliable analgesia to the anterior and lateral abdominal wall and is volume dependent. It can be performed blindly or using ultrasound. But ultrasound guided block helps in better localisation of the planes resulting in improved accuracy.[12] It is easier to perform TAP block in semilateral position in the obese.[3] In super obese patients, low-frequency convex probe is preferable as the deeper tissues are visualised better.[4] Since a major thickness of the anterior abdominal wall was bypassed by placing the ultrasound probe directly over the surgical area, the linear probe proved sufficient in our case.