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  • EDUCATION

    Bruno Riou, M.D., Ph.D., Editor

    Case Scenario: Management of IntraoperativeHypoxemia during One-lung Ventilation

    Hadrien Roze, M.D.,* Mathieu Lafargue, M.D., Alexandre Ouattara, M.D., Ph.D.

    H YPOXEMIA that may reasonably be defined by an ar-terial hemoglobin oxygen saturation of less than 90%occurs in 510% of patients during one-lung ventilation(OLV).1 The physiopathology of hypoxemia is complex, andthe management of intraoperative hypoxemia during OLV re-mains a challenge for anesthesiologists. In life-threatening hy-poxemia, correct oxygenation should be restored rapidly. Thismay require discontinuing surgery to eliminate reversible causesof hypoxemia. Several strategies can then be applied to preventand correct hypoxemia during OLV.

    Case ReportsA 50-yr-old man undergoing resection of the upper rightlung for neoplasia developed hypoxemia 15 min after thestart of OLV. Preoperative examination revealed satisfactorycardiopulmonary status. Preoperative rest and dobutaminestress echocardiography revealed normal left ventricularfunction without any wall motion abnormalities. Dopplerultrasound examination of the carotid arteries was normal.Preoperative pulmonary function tests were normal withoutany 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 renalfunction were normal. There was no history of bronchopul-monary infection, and arterial blood gas values in room airwere PaO2 83 mmHg, PaCO2 38 mmHg, pH 7.40, andHCO3 25 mM. Electrocardiogram showed regular sinusrhythm, and blood pressure on the morning of surgery was128/65 mmHg. The patient refused epidural anesthesia formanagement of postoperative pain. Selective bronchial intu-bation of the left main-stem bronchus was performed with a39F left-sided double lumen tube (DLT) (Broncho-part;Rusch, Kermen, Germany). The correct position of the tubewas immediately confirmed with a fiberoptic bronchoscopy,and the patient was then placed in the lateral position. Vol-ume-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-expiratorypressure (PEEP), was used. End-tidal carbon dioxide andplateau pressure were 31 mmHg and 19 cm H2O, respec-tively. No intrinsic PEEP was observed. OLV was initiatedwithout any change in ventilator settings. Fifteen minuteslater, the patient exhibited profound hypoxemia with a sig-nificant decrease in pulse oxymetry from 94% to 88%. Ar-terial blood gas values were pH 7.41, PaO2 52 mmHg (100%FIO2), PaCO2 40 mmHg, HCO3 24.8 mM, and 87% SaO2.The patients hemodynamics and electrocardiogram re-mained stable. Expiratory flow and expiratory VT were un-changed, and no leak was noticed. The correct position of theDLT was immediately confirmed by fiberoptic inspection.End-expiratory flow was not interrupted by the next insuf-flation and reached zero before the next respiratory cycle,therefore no dynamic hyperinflation or intrinsic PEEP(iPEEP) was observed. Once the surgeon was informed, thenondependent lung (nonventilated lung) was expandedmanually by administration of pure oxygen, and a continu-ous positive airway pressure (CPAP) at 5 cm H2O was sub-sequently applied. This strategy allowed rapid improvementof the patients oxygenation, and oxymetry pulse could bemaintained above 95% throughout the surgical procedureunder OLV. During the manual expansion of the nondepen-dent (nonventilated) lung, hemodynamics remained stable.

    * Staff Anesthesiologist, Department of Anesthesiology and Crit-ical Care 2, Centre Hospitalier Universitaire (CHU), Bordeaux,France, Staff Anesthesiologist, Department of Anesthesia and Peri-operative Care, San Francisco General Hospital, University of Cali-fornia, San Francisco, San Francisco, California, Assistant Profes-sor, Chairman, Department of Anesthesiology and Critical Care,CHU.

    Received from the Department of Anesthesiology and IntensiveCare 2, Centre Hospitalier Universitaire (CHU) Bordeaux, GroupeSud, Pessac, Universite Victor Segalen Bordeaux II, Bordeaux,France. Submitted for publication May 25, 2010. Accepted for pub-lication August 3, 2010. Support was provided solely from institu-tional and/or departmental sources. The figures in this article wereprepared by Annemarie B. Johnson, C.M.I., Medical Illustrator,Wake Forest University School of Medicine Creative Communica-tions, Wake forest University Medical Center, Winston-Salem, NorthCarolina.

    Address correspondence to Dr. Ouattara: Service dAnesthesie-Reanimation 2, Hopital Haut Leveque, avenue Magellan, Pessac,France. [email protected] This article may beaccessed for personal use at no charge through the Journal Web site,www.anesthesiology.org.

    Copyright 2010, the American Society of Anesthesiologists, Inc. LippincottWilliams & Wilkins. Anesthesiology 2011; 114: 16774

    Anesthesiology, V 114 No 1 January 2011167

  • Because the surgical procedure was a right open thoracot-omy, it was not impeded by the application of CPAP to thenondependent lung, which was stopped at the end of OLV.The postoperative course of this patient was uneventful. Hedid not exhibit any hypoxemia after tracheal extubation.

    Discussion

    Management of Intraoperative HypoxemiaThe first step when a patient suffers from hypoxemia (i.e., adrop in pulse oxymetry less than 90%) during OLV is to stopsurgery, increase the inspired oxygen fraction to 100%, andrapidly restore two-lung ventilation (TLV). That can be per-formed with a manual reexpansion of the lung using thehand bag with pure oxygen flow and an airway pressure lim-ited valve between 20 and 30 cm H2O; the reexpansion ofthe deflated lung is visual. Once acceptable oxygenation hasbeen restored, two simultaneous actions must be performed:(1) a reversible cause of hypoxemia must be ruled out beforerestarting surgery and (2) oxygenation of the patient must beimproved to prevent the recurrence of hypoxemia. Becausehypoxemia during OLV is mainly related to ventilator orperfusion mismatch, strategies to restore oxygenation shouldhave two objectives: to improve alveolar ventilation and pul-monary perfusion. The first consists of restoring alveolar ven-tilation of the nondependent lung by applying oxygen infla-tion with CPAP and of the dependent lung by performing arecruitment maneuver and applying PEEP. Perfusion, on theother hand, involves strategies to limit intrapulmonaryshunt: positioning of the patient (strict lateral decubitus po-

    sition on the side of the dependent lung provides better ox-ygenation than semilateral or even supine position), surgicallung compression or clamping the pulmonary artery of thenondependent lung, limitation of airways pressure of theventilated lung including limitation of intrinsic PEEP, andthe use of moderate VT (68 ml/kg) or pressure-controlledventilation. Some pharmacological treatments, such as nitricoxide and almitrine, can also be used to decrease intrapulmo-nary shunt. An algorithm for the treatment of hypoxemiaduring OLV is summarized in figure 1.

    Diagnosis of a Treatable Cause of HypoxemiaBecause dislodgment of the DLT is a common cause of hy-poxemia, the first step is to check that the DLT is in thecorrect position and to clear secretions or blood from thetube or the respiratory tract. Initially, blinded bronchoaspi-ration can be performed on both sides of the DLT. It issometimes sufficient to clear proximal secretions and blood.Clinical examination of the correct position of the DLT withauscultation and inspection of the DLT is necessary butsometimes fails to identify DLT malpositioning. Conse-quently, correct positioning of the DLT must be systemati-cally confirmed by fiberoptic.1,2 Fiberoptic bronchoscopymust be repeated once hypoxemia occurs or in the presenceof increased airways pressure. The DLT can be misplacedleading to impaired oxygenation and inadequate lung sepa-ration with high airway pressure or significant leak.2 Hemo-dynamic conditions also need to be assessed. Although pa-tients undergoing lung resection are vulnerable to fluidoverhydration, the maintenance of cardiac output, mainly by

    Fig. 1. Algorithm recommended to be performed in case of hypoxemia during one-lung ventilation (OLV). CPAP continuouspositive airway pressure; DLT double lumen tube; FIO2 inspired fraction of oxygen; PEEP positive end-expiratorypressure; PGI2 prostacyclin; ST ST segment.

    Hypoxemia and One-lung Ventilation

    Anesthesiology 2011; 114:16774 Roze et al.168

  • fluid loading, is required for that oxygen delivery to meetpatient metabolic needs. As OLV induces increase in rightventricular overload, intraoperative assessment of ventricularfunction may be useful.3 Right ventricular dysfunction mayalso be related to volume overload or intrinsic myocardialdepression.3 Despite some limitations in the analysis of rightventricular function, transesophageal echocardiography isprobably the best intraoperative monitoring technique to useduring OLV.3 The two main signs that must be sought arethe right ventricular dilatation as well as paradoxical septalmotion.4 Moreover, maintenance of an adequate level ofanesthesia allows limiting hemodynamic disturbances relatedto a too-deep level of anesthesia.

    How Can Ventilation of the Nondependent Lung beImproved?Application of CPAP. Although it is frequently applied, in-creasing FIO2 in the ventilated lung is often not sufficient toimprove oxygenation because OLV is responsible for an im-portant shunt-like effect of approximately 30%.5 Adminis-tration of oxygen to the nondependent lung is usually used totreat hypoxemia during OLV, but it may also be used toprevent it. Oxygen may be administered with or withoutCPAP of 510 cm H2O to the nondependent lung. If noCPAP valve is available,