a 53-year - old male , with functional status 2 according to american society of anesthesiologists , with no history of cardiovascular diseases , underwent elective extended right hemihepatectomy for large metastatic tumor of the liver hilum ( 155  101 mm in segments 4/5/6/8 and 108  64 mm in segment 7 ) . photographs of the anterior and posterior surface of the resected liver segments are displayed in figs . 1 and 2 respectively . anterior surface of the resected liver segments posterior surface of the resected liver segments anesthesia was induced with fentanyl and propofol . anesthesia was maintained with sevoflurane and oxygen ( fraction of inspired oxygen fio2 0,5 ) . approximately two hours after the start of procedure ( previously uneventful ) rapid decrease in end - expiratory carbon dioxide pressure ( etco2 ) to 2.6 kpa with desaturation down to 84% and subsequent fall in blood pressure to minimal value of 45/20 mm hg and raise in heart rate to 110 beats / minute was noted . the arterial blood gas analysis showed ph  7,11 , po2  12,6 kpa , pco2  9,6 kpa , hco3 -  18,3 mmol / l and be was informed about the emergency . in order to diagnose the pathology responsible for rapid haemodynamic instability toe probe differential diagnosis included venous air embolism ( vae ) , hypovolaemia due to massive bleeding and inferior vena cava compression related to liver torsion . the mid - oesophageal aortic valve short axis view demonstrated prominent air bubbles in the right atrium ( fig . there were no air bubbles on left side of the heart and left ventricle contractility was normal . as the vae was confirmed patient was turned into trendelenburg position , fio2 was increased to 1.0 and positive end - tidal pressure ( peep ) turned up to 10 cm h20 . patient was further resuscitated with intravenous fluids , blood products and vasopressors under surveillance of toe which demonstrated gradual disappearing of air bubbles from the right heart . 1 ) . 
  toe mid - oesophageal aortic valve short axis view demonstrating air bubbles in right atrium and normal appearance of the left atrium with no air bubbles serial arterial blood gas results during intraoperative period vae venous air embolism ; fio2  fraction of inspired oxygen ; etco2  end - tidal carbon dioxide pressure after completion of the surgery patient was admitted to surgical intensive care unit . the post - operative bloods showed significant increase in nt - probnp concentration up to 3410 pg / ml with only mild elevation of troponin i levels up to maximum value of 0,31 ng / ml with no ischaemic changes on ecg . patient was successfully extubated 4 hours after the end of surgery and weaned off vasopressors the next day . we present a case in which intraoperative use of toe helped to immediately identify the cause of sudden hypotension and hypoxaemia . in this case tumor size and location in close proximity of the large vessels were not only making surgical dissection challenging , but also they were predisposing to all potential major complications . air entrainment usually presents as a rapid onset of haemodynamic compromise with fall in po2 and rise in pco2 . clinical diagnosis of vae may be very difficult as it can mimic other , more common conditions like severe hypovolaemia , myocardial ischaemia or inferior vena cava compression related to torsion of the liver . the techniques available for detection of vae include toe , transthoracic echocardiography ( tte ) , pulmonary artery catheterization , and monitoring of endexpiratory carbon dioxide tension or central venous pressure . at present toe remains the most sensitive method of detecting vae , with a treshold of 0,020,19 ml of air per kg body weight . recent paper published by schulmeyer et al . demonstrated that toe performed by trained anaesthetist during non - cardiac surgeries helped to establish cause of refractory hypotension in all 42 cases . the most common cause of hypotension unresponsive to standard fluid bolus and ephedrine according to toe findings were severe hypovolaemia ( 42% ) , followed by thromboembolic events ( 14% ) . further diagnoses comprised of low ejection fraction of the left ventricle , myocardial ischaemia , dynamic left outflow tract obstruction , associated with anterior systolic motion of the mitral valve and cardiac tamponade . retrospective analysis of 22 cases where toe was used during intraoperative cardiac arrest in patients undergoing non - cardiac procedures revealed that toe confirmed suspected primary cause of cardiac arrest in 19 patients . according to the toe findings the most common cause of cardiac arrest were thromboembolic events which were diagnosed in 9 patients ( in 6 patients thrombi were visualised directly and in further 3 patients by indirect echocardiographic signs of pulmonary embolism ) . other listed causes included cardiac ischaemia ( 6 patients ) , cardiac tamponade ( 2 patients ) and severe hypovolaemia ( 2 patients ) . in our case toe was also a valuable tool for direct monitoring of efficacy of instituted treatment . demonstrated that perioperative use of toe changed management in 40% of patients undergoing non - cardiac surgery . modifications of management based on toe findings were mainly related to change in medical management ( 45% ) , confirming or invalidating diagnosis ( 30% ) and performing previously unplanned surgical interventions ( 18% ) . in other study published in 2004 toe based on toe findings initiation or change in use of vasodilator and vasopressor therapy was noted respectively in 55% and 43% of patients . these effects were mainly observed amongst patients with pre - existing regional wall motion abnormalities of the left ventricle , pulmonary arterial hypertension and with history of right heart failure . in previously mentioned paper , toe performed in patients with intraoperative cardiac arrest toe affected further management in 18 out of 22 patients , including 12 patients who were scheduled for emergency surgical interventions . these promising results with the use of toe during noncardiac surgeries were reflected in the last guidelines of the american society of anesthesiologists and the society of cardiovascular anesthesiologists . according to this document toe should also be utilised in all cases where life - threatening hypotension is anticipated . patient - related indication for intraoperative use of toe are known or suspected cardiovascular pathologies which might result in haemodynamic , pulmonary or neurologic compromise . however it is noteworthy , that due to scanty evidence coming from case reports , case series and single centre studies all above recommendations are based on expert opinion and require further investigations . in this paper we discussed a case where intraoperative use of toe by trained anaesthetist during liver resection helped to establish cause of severe hypotension and hypoxaemia , as well as guided optimization of patients haemodynamic status . further investigations are required to assess costeffectiveness of this method , as well as impact of training level of its diagnostic capabilities . authors do not report any financial or personal links with other persons or organizations , which might affect negatively the content of this publication and/or claim authorship rights to this publication .
a 53-year - old male , with no history of cardiovascular diseases , underwent elective extended right hemihepatectomy for large metastatic tumor . approximately 2 hours after the start of procedure sudden onset of severe hypotension associated with profound desaturation and significant fall in end - tidal carbon dioxide pressure was noted . 
 transoesophageal echocardiography was performed and massive air embolism was confirmed . patient was turned into trendelenburg position , inspired oxygen was increased to 100% and positive end - expiratiory pressure turned up to 10 cm h20 . 
 patient was further resuscitated with iv fluids , blood products and vasopressors under surveillance of transoesophageal echocardiography . in this report 
 we present a case in which intraoperative use of transoesophageal echocardiography by trained anaesthetist helped to immediately identify the cause of sudden hypotension and hypoxaemia . 
 transoesophageal echocardiographywas also a valuable tool for direct monitoring of efficacy of instituted treatment .