Phasic voltage ECG variation during laparoscopy

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Editor—We would like to report a case in which atypical intraoperative ECG changes during laparoscopy alerted us to the recurrence of a pneumothorax, despite the presence of an in situ chest drain. In a 22-yr-old male, after a 2 cm stab wound in the left ninth intercostal space in the mid-axillary line, a small left-sided apical pneumothorax was seen on the CT scan, with free air in the abdomen. A left-sided intercostal chest drain was inserted under local anaesthesia, which drained 30 ml of serous fluid and a little air. Laparoscopy was planned to exclude bowel perforation. After induction of general anaesthesia that included 5 cm of PEEP, peak airway pressure was 19 cm H2O, but rose to 25 cm H2O after carbon dioxide (CO2) pneumoperitoneum was produced. Abdominal insufflation pressure was limited to 12 mm Hg. Laparoscopy revealed a 2 cm tear in the tendinous part of the left hemidiaphragm and a small serosal tear on the anterior wall of the stomach. When the laparoscope was passed through the diaphragmatic tear into the chest, the intercostal drainage tube was seen to be wedged between the chest wall and the left lung. At the same time, phasic voltage variation was noted in lead II of the ECG tracing (Fig. 1). There was, however, no change in palpable pulse, blood pressure, or plethismograph waveform. It was also noticed that the water meniscus in the intercostal drainage tube was neither swinging nor bubbling in time with ventilation. After laparoscopic repair of the diaphragmatic tear, the ECG reverted to normal and the water meniscus in the intercostal drainage tube started swinging again. Pneumothorax, though a rare complication of laparoscopic abdominal surgery, can be difficult to diagnose in an anaesthetized patient. Botz and Brock-Utne1Botz G Brock-Utne JG Are electrocardiogram changes the first sign of impending peri-operative pneumothorax?.Anaesthesia. 1992; 47: 1057-1059Crossref PubMed Scopus (21) Google Scholar reported that reduction in ECG amplitude had alerted them to the diagnosis of intraoperative pneumothorax during an open left nephrectomy. Phasic ECG voltage variation has previously been reported in non-anaesthetized patients, the majority with left-sided spontaneous pneumothorax, with the ECG variation disappearing after intercostal drainage.2Kozelj M Rakovec P Sok M Unusual ECG variations in left-sided pneumothorax.J Electrocardiol. 1997; 30: 109-111Abstract Full Text PDF PubMed Scopus (17) Google Scholar 3Kounis NG Mallioris CN Karavias D Zavras G Siablis D Unusual electrocardiographic changes in intrathoracic conditions.Acta Cardiol. 1987; 42: 179-185PubMed Google Scholar In our case, phasic voltage ECG variation was noted under anaesthesia, with QRS amplitude being 0.9 mV during expiration and 0.6 mV during inspiration (Fig. 1), repeating with each ventilation cycle. During laparoscopy, the pneumoperitoneum was in communication with the interpleural space through the diaphragmatic tear, thus CO2 collected in the pleural cavity with increasing accumulation during the thoracoscopy. The ineffective chest drain failed to vent CO2 from the thorax; this caused a localized gas collection near the left hemidiaphragm and heart. No changes in airway pressure or haemodynamics were noted, presumably because of the localized nature of the gas collection and PEEP. PEEP maintains part-inflation of the lung during expiration and decreases the pressure gradient between the abdominal and pleural cavities. It indeed has been suggested as an alternative to chest tube placement in the case of intraoperative CO2 pneumothorax, as it can reverse or prevent the deteriorating respiratory mechanisms and improve haemodynamics.4Joris JL Chiche JD Lamy ML Pneumothorax during laparoscopic fundoplication: diagnosis and treatment with positive end-expiratory pressure.Anesth Analg. 1995; 81: 993-1000PubMed Google Scholar Pneumothorax produces ECG changes because of a combination of longitudinal rotation of the heart, displacement of the mediastinum, and the insulating effect of intrathoracic air.5Master AM The electrocardiographic changes of pneumothorax in which the heart has been rotated; similarity of some of these changes to those indicating myocardial involvement.Am Heart J. 1928; 3: 472-483Abstract Full Text PDF Scopus (29) Google Scholar Our observed ECG voltage variations were probably due to the iatrogenic intrathoracic air adjacent to the heart that underwent phasic alteration in size or position in time with respiration. In conclusion, we propose that ECG changes during laparoscopy can be used to alert an anaesthetist of a probable intraoperative pneumothorax. It also illustrates that PEEP during laparoscopy can contribute not only to occasional failure of a pre-existing intercostal drain but also to the beneficial effect of limiting the severity of a pneumothorax.