Will transoesophageal echocardiography become a standard tool for anesthetists to assess haemodynamic status during non-cardiac surgeries? Case report and literature review.

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.

Over the last decade echocardiography has gained increasing interest amongst medical specialties other than cardiology, like anaesthesia, emergency medicine or intensive care. Currently transoesophageal echocardiography (TOE) is routinely used by anaesthetist during cardiac surgeries to guide perioperative fluid management and use of inotropic or vasopressor support. However its use during non-cardiac surgeries is less established. In this paper we present a case where TOE was used to run differential diagnosis of intraoperative hypotension, as well as helped to guide further haemodynamic optimization of the patient.

Case report

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.

Fig. 1

Anterior surface of the resected liver segments

Fig. 2

Posterior surface of the resected liver segments

Anesthesia was induced with fentanyl and propofol. Tracheal intubation was facilitated with vecuronium. 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 – –5,9 mmol/l, consistent with mixed acidosis. At that stage surgical team was informed about the emergency.

In order to diagnose the pathology responsible for rapid haemodynamic instability TOE probe was inserted (SonoSite MicroMaxx® 8–3 MHz). 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. 3). Right ventricle contractility was moderately impaired. 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. Surgical team identified and sutered up a tear of the right hepatic vein. 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. This was correlated with clinical improvement of vital parameters and ABG results (tab. 1).

Fig. 3

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

Tab. 1

Serial arterial blood gas results during intraoperative period

	After induction of anaesthesia	After onset of VAE	At the end of surgery
FiO2	0,5	1,0	0,6
EtCO2 (kPa)	4,6	2,6	4,0
pH	7,396	7,115	7,290
pO2 (kPa)	19,3	12,6	24,5
pCO2 (kPa)	5,6	9,6	6,1
HCO3 − (mmol/l)	25,4	18,3	20,5
BE (mmol/l)	1,2	−5,9	−4,3
Base excess (mmol/l)	0,9	4,8	2,1
Lactate (mmol/l)	8,5	9,8	7,3

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. A week later he was discharged from hospital.

Discussion

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. VAE can be a life threatening complication of the liver resection. 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 0,02–0,19 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. Denault et al. 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 was used to optimize haemodynamic status in patients undergoing vascular or major visceral surgery. Based on TOE findings initiation or change in use of vasodilator and vasopressor therapy was noted respectively in 55% and 43% of patients(. Fluid therapy was affected in 24% 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 it is recommended that TOE should be used during unexplained persistent hypotension or hypoxaemia. 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(.

Conclusions

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.