from Anesthesiology.com
Case Report:
A 50-yr-old man undergoing resection of the upper right lung for neoplasia developed hypoxemia 15 min after the start of OLV. Preoperative examination revealed satisfactory cardiopulmonary status. Preoperative rest and dobutamine stress echocardiography revealed normal left ventricular function without any wall motion abnormalities. Doppler ultrasound examination of the carotid arteries was normal.
Preoperative pulmonary function tests were normal without any obstructive disease (forced expired volume in 1 s was 3.7 l and forced expired volume in 1 s/vital capacity was 73%). Blood electrolytes, hemoglobin concentration, and renal function were normal. There was no history of bronchopulmonary infection, and arterial blood gas values in room air were Pao2 83 mmHg, Paco2 38 mmHg, pH 7.40, and HCO3 25 mm. Electrocardiogram showed regular sinus rhythm, and blood pressure on the morning of surgery was 128/65 mmHg. The patient refused epidural anesthesia for management of postoperative pain. Selective bronchial intubation of the left main-stem bronchus was performed with a 39F left-sided double lumen tube (DLT) (Broncho-part; Rüsch, Kermen, Germany). The correct position of the tube was immediately confirmed with a fiberoptic bronchoscopy, and the patient was then placed in the lateral position. Volume-controlled ventilation, including a 7 ml/kg tidal volume (VT) of predicted body weight under 100% Fio2, a 12 cycles/min respiratory rate, and a 5 cm H2O positive end-expiratory pressure (PEEP), was used. End-tidal carbon dioxide and plateau pressure were 31 mmHg and 19 cm H2O, respectively. No intrinsic PEEP was observed.
OLV was initiated without any change in ventilator settings. Fifteen minutes later, the patient exhibited profound hypoxemia with a significant decrease in pulse oxymetry from 94% to 88%. Arterial blood gas values were pH 7.41, Pao2 52 mmHg (100% Fio2), Paco2 40 mmHg, HCO3 24.8 mM, and 87% Sao2. The patient's hemodynamics and electrocardiogram remained stable. Expiratory flow and expiratory VT were unchanged, and no leak was noticed. The correct position of the DLT was immediately confirmed by fiberoptic inspection. End-expiratory flow was not interrupted by the next insufflation and reached zero before the next respiratory cycle, therefore no dynamic hyperinflation or intrinsic PEEP (iPEEP) was observed. Once the surgeon was informed, the nondependent lung (nonventilated lung) was expanded manually by administration of pure oxygen, and a continuous positive airway pressure (CPAP) at 5 cm H2O was subsequently applied. This strategy allowed rapid improvement of the patient's oxygenation, and oxymetry pulse could be maintained above 95% throughout the surgical procedure under OLV. During the manual expansion of the nondependent (nonventilated) lung, hemodynamics remained stable. Because the surgical procedure was a right open thoracotomy, it was not impeded by the application of CPAP to the nondependent lung, which was stopped at the end of OLV. The postoperative course of this patient was uneventful. He did not exhibit any hypoxemia after tracheal extubation.
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