Intraoperative air embolism during hepatectomy

Sir, Vascular air embolism (VAE) is a rare and lethal complication of partial hepatectomy with a relative risk of <5%.[1] Even in the absence of intracardiac abnormalities, paradoxical embolism can occur in cirrhotic patients undergoing liver resection because of abnormal arteriovenous communications in the pulmonary circulation.[2] Anaesthetic vigilance along with thorough knowledge of surgical interventions and ensuing physiological perturbations is essential for ensuring patient survival. A 56-year-old female diagnosed with hilar cholangiocarcinoma was posted for extensive right hepatectomy. Clinical examination was normal except for the presence of jaundice with elevated bilirubin and liver enzymes. Anaesthetic technique included general anaesthesia with thoracic epidural block. Electrocardiogram (ECG), oxygen saturation, blood pressure and end-tidal carbon dioxide (ETCO2) were monitored. Left radial artery was cannulated for invasive blood pressure (IBP) monitoring and right internal jugular vein for central venous pressure (CVP), with double lumen 7 Fr central venous catheter (CVC). To reduce the blood loss and transfusion requirements, a low CVP (≈5 mmHg) was targeted. Hepatic resection using cavitron ultrasonic surgical aspirator (CUSA) began after clamping the branches of portal vein and hepatic artery to the right lobe. Three hours into the surgery, surgeon informed accidental opening of a branch of hepatic vein which got retracted into liver parenchyma. Simultaneously, a distinct sucking-in sound was heard, following which IBP dropped to 50/40 mmHg and ETCO2 to 22 mmHg from 34 mmHg while oxygen saturation and CVP (8 mmHg) remained stable. VAE was suspected and nitrous oxide was cut off and the patient ventilated with 100% oxygen. Surgical field was immediately covered with saline-soaked gauze, and then flooded with saline. Resuscitative measures were initiated rapidly with fluid resuscitation, dopamine infusion at 10μg/kg/min and adopting a Trendelenburg position. Aspiration of CVC produced 3 ml of frothy blood. As IBP remained low, epidural infusion was discontinued and a bolus of 50μg adrenaline was administered intravenously. Once vitals stabilised, surgery proceeded with 100% oxygen after giving fentanyl and midazolam. Fifteen minutes later, a second episode of VAE occurred and was accompanied by a fall in oxygen saturation, IBP, ETCO2 and a rise in CVP to 18 mmHg. ECG showed frequent atrial ectopic beats. Dopamine infusion rate was increased and CVC aspirated to obtain 3–4 ml of air. Two more episodes of haemodynamic instability occurred which was treated similarly. At the end of the procedure, her vitals were stable with dopamine support. She was shifted to intensive care unit and was weaned from haemodynamic and ventilator support next day. Factors predisposing to VAE during liver resection include surgical technique, size and site of the tumour, blood loss and low CVP.[3] There are reports of increased incidence and severity of VAE during hepatic resection using CUSA.[45] Resection of large tumours situated in the right lobe close to inferior vena cava or the cavo-hepatic junction increases the risk of VAE.[3] Low CVP further enhances the negative pressure gradient and increases the possibility of VAE. Hepatic vascular control using selective hepatic vascular exclusion (SHVE) technique reduces both blood loss and risk of VAE.[3] In our case, site of the tumour, resection using CUSA and lack of SHVE technique along with low CVP anaesthesia all contributed to the incident. Although lethal volume of venous air for adults is about 200–300 ml, the proximity of the entraining vessel to the heart makes even smaller volumes fatal in liver resection.[13] Management consists of steps to prevent further entrainment of air and haemodynamic support with inotropic agents.[1234] To conclude, both surgeons and anaesthesiologists should be aware of the risk for VAE during hepatectomy and employ appropriate surgical techniques and levels of monitoring to ensure patient safety. Financial support and sponsorship Nil. Conflicts of interest There are no conflicts of interest.