Venous air embolism during major liver surgery

Abstract

Editor, Venous air embolism is a potentially fatal event, but its prevalence during liver resection is unknown. Although major gas embolisms have been reported during liver surgery, liver resection has not been documented as a procedure bearing a serious risk of this complication.1 Lodging of air in the pulmonary vessels results in the elevation of pulmonary arterial pressure and a rapid decrease in end-tidal carbon dioxide concentration (EtCO2).2 The sudden onset of this symptom during an operation usually raises the suspicion of possible venous air embolism. The aim of this study was to assess the incidence of embolic events during liver resection with the use of transoesophageal echocardiography (TOE), the most sensitive method for detection of pulmonary air embolism.3 Ethical approval for this study (Ethical Committee No. RNN/369/12/KB) was provided by the Ethical Committee of the Medical University of Lodz, Poland (Chairperson Prof Przedzisław Polakowski) on 22 May 2012. Intraoperative visualisation of heart chambers was obtained by inserting a TOE probe (model 6T GM Medical System, complementary with VIVID 7 PRO; General Electric, Milwaukee, USA) into the oesophagus. All the TOE examinations were made along the interatrial septum. The data were analysed using software for quantitative analysis of signal intensity (Q-analyse; General Electric, Milwaukee, WI, USA). Using the time intensity curves, data were analysed in two regions of interest: right atrium (RA) and left atrium. All statistical calculations were performed using SigmaPlot version 12.0 (Systat Software Inc., San Jose, CA, USA). To compare the differences in maximum and minimum EtCO2, heart rate and mean arterial pressure in groups with and without gas embolism on TOE, we applied the parametric t-test and nonparametric Mann–Whitney test. All data are given in the text as mean and standard deviation Thirty-eight consecutive patients scheduled for hemihepatectomy (right: 29, left: 9) for metastatic tumours of the liver were enrolled in the study. The average age was 56.3 years (range 22 to 75 years). Combined general and epidural anaesthesia was undertaken in all patients. Minor [defined as several air bubbles in the RA and right ventricle (RV)] and major air embolisms (air bubbles filling at least 50% of the RA and RV) were identified in 23 (60%) and five (13%) patients, respectively. Air embolism was accompanied by cardiorespiratory changes including a decrease in minimum EtCO2 (to 3.2 ± 0.4 versus 3.8 ± 0.4 kPA; P = 0.005) and increase in maximum heart rate (101.1 ± 12.0 versus 87.3 ± 12.1 beats per minute; P = 0.003). The difference in signal intensity (dB) between the RA and the left atrium is shown in Fig. 1.Fig. 1: No captions available.Furthermore, all serious complications, including early postoperative myocardial infarction (one case; 2.6%) and bleeding requiring intraoperative blood transfusion (six cases; 15%) occurred in patients with air embolism. Finally, the mean length of hospital stay tended to be longer in this group than in patients without air embolism (13.1 ± 7.7 versus 8.5 ± 1.7 days; P = 0.123). The prevalence of venous air embolism during liver surgery is underestimated.4 Liver resection requires intraoperative reduction of central venous pressure to minimise bleeding from transected parenchyma. The combination of general and epidural anaesthesia used for this purpose results in arterial hypotension, masking the main signs of pulmonary embolism.5,6 To the best of our knowledge, this is the first study investigating the prevalence of pulmonary air embolism during major liver surgery with the routine use of TOE. The results show that air embolism is common and generally asymptomatic. However, further studies elucidating its influence on the postoperative course of patients after liver resection are needed. Acknowledgements relating to this article Assistance with the letter: none. Financial support and sponsorship: none. Conflicts of interest: none. Presentation: none.