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TECHNOLOGY, COMPUTING, AND SIMULATION

Endobronchial Blocker Dislodgement Leading to Pulseless Electrical Activity

Department of Anesthesia & Critical Care, Massachusetts General Hospital, Boston, Massachusetts

Address correspondence and reprint requests to Warren S. Sandberg, MD, PhD, Department of Anesthesia & Critical Care, Massachusetts General Hospital, 55 Fruit St, Clinics 3, Boston, MA 02114. Address e-mail to wsandberg{at}partners.org.

	Abstract

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This is a report of a case in which an endobronchial blocker was dislodged, leading to severe air trapping and a brief episode of pulseless electrical activity. Bronchial blockade for lung deflation was successfully instituted during emergency repair of a ruptured descending aortic aneurysm. During a period not involving manipulation of aortic cross-clamps, end-tidal CO₂ decreased precipitously to zero and airway pressures increased markedly, followed by equalization of intracardiac pressures. Prompt deflation of the endobronchial blocker balloon reversed the problem. We hypothesize that when surgical manipulation dislodged the bronchial blocker into the tracheal position, leading to profound air trapping as successive, stacked tidal volumes were forced distal to the blocker.

	Introduction

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Bronchial blockade is an accepted method for achieving lung isolation, with unique advantages that sometimes recommend this technique over traditional double-lumen tubes. We successfully used bronchial blockade to facilitate emergency repair of a ruptured aortic aneurysm and encountered a heretofore-unreported complication arising from blocker malposition.

	Case Report

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A 72-yr-old, 64-inch-tall, 154-pound female was brought emergently to the operating room (OR) with a ruptured juxtarenal aortic aneurysm demonstrated by non-contrast computed tomography. An arterial catheter showed an initial systolic blood pressure of 150 mm Hg, but this decreased to the low 60s during transfer to the OR table. The patient was promptly tracheally intubated with a 7.5 mm ID cuffed endotracheal tube in the supine position and turned left side up so that emergency surgical preparation could be performed. Volume resuscitation returned the systolic blood pressure to 120 mm Hg. Surgical incision was therefore delayed to allow placement of a left internal jugular introducer and pulmonary artery catheter.

Prompt surgical intervention was thought to take precedence over lung isolation, so incision was made for a left thoracoabdominal approach. During the initial dissection, a loop guided bronchial blocker (Cook Critical Care, Bloomington, IN) was satisfactorily placed in the left mainstem bronchus following the manufacturer directions for use. Bronchial placement was confirmed by bronchoscopy while the blocker balloon was inflated. The blocker was locked in place by tightening the appropriate clamp on the multiport adapter. Lung isolation was good, as judged by a steady reduction in the volume of the left lung over the next half hour. Proximal control of the aorta was obtained at the T8–9 level.

Suddenly, the end-tidal CO₂ decreased to zero. Concomitantly, the systemic, pulmonary and central venous pressures began to equalize at approximately 40 mm Hg and became nonpulsatile over the course of a few breaths. The airway pressures were quite high (approximately 40 cm H₂O). The surgeon noted that the left lung had inflated over the same time course. During manual ventilation, delivered tidal volumes did not return to the breathing bag during exhalation.

The balloon of the bronchial blocker was swiftly deflated and the patient was disconnected from the breathing circuit. Gas rushed audibly out of the endotracheal tube. The vascular pressures become pulsatile and returned to their previous values. Bronchoscopic examination of the airway revealed that the blocker’s deflated balloon was in the trachea. Lung isolation was re-established by advancing the blocker into the left mainstem bronchus under bronchoscopic guidance and reinflating the blocker balloon. The case was concluded uneventfully.

	Discussion

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Given the site of the aneurysm, a low thoracic aortic cross-clamp in the chest would almost certainly be required. Lung isolation is seldom absolutely required for such an operation, but it can facilitate surgery in the chest by relieving the need to pack the lung out of the field (1). Lung isolation is achieved with double-lumen tubes or with a growing family of increasingly sophisticated devices for bronchial blockade (2). Double-lumen tubes have many desirable features, but they require reintubation if lung isolation is to be established in the tracheally intubated patient. If the patient is to remain tracheally intubated postoperatively, the tube may need to be changed again at the end of the case.

Tracheally reintubating a patient in the lateral decubitus position presents a needless challenge for airway management unless returning to the supine position is precluded. If the patient cannot be placed supine, then lung isolation with a bronchial blocker is preferable. Using a loop guided blocker (3–5), lung isolation can be achieved in any case where bronchoscopy is possible. In this particular case, the need for urgent surgery took precedence over returning to the supine position for tracheal reintubation, and a loop guided blocker was used successfully.

Bronchial blockade allows lung isolation by occlusion of the ipsilateral mainstem bronchus. With the exception of the Univent tube, bronchial blockers can be placed and removed without tracheally reintubating already intubated patients. Balloon occlusion bronchial blockade was first described in 1936 (6), and the subject has recently been reviewed (2). Most problems with bronchial blockade involve difficulty in achieving lung isolation or the potential for airway obstruction resulting from malpositions, and these problems typically merit mention in textbooks and reviews of the subject.

As events unfolded, the patient developed pulseless electrical activity (PEA) during aortic surgery with one-lung ventilation. The first intervention was to deflate the balloon of the bronchial blocker. The blocker was the leading suspect for causing the problem, as the surgeons were not in the process of applying or removing aortic clamps, nor were they doing anything else that might have caused PEA. Deflating the balloon was unlikely to interfere with the operation, as the lung had already inflated. Loss of isolation was an important clue to the source of the problem, as a well-positioned blocker should not allow unintentional lung inflation. Under the circumstances, the differential diagnosis of equalizing intracardiac pressures leading to PEA included (most prominently) massive exsanguination, cardiac tamponade, and profound air trapping (7,8), also known as auto-positive end-expiratory pressure (PEEP). A quick view of the surgical field excluded exsanguination and tamponade.

Auto-PEEP occurs when subsequent inspired breaths are stacked without adequate exhalation, leading to increased intrathoracic pressures and consequent inadequate preload. Absent end-tidal CO₂ is a manifestation of no cardiac output, no exhalation, or both. The fact that the end-tidal CO₂ declined to zero in a very short period followed by equalization of intracardiac pressures pointed to a mechanical problem with ventilation as the primary problem. High airway pressures also indicated a breathing circuit/airway problem. Delivered tidal volumes that visibly distended the lung during manual ventilation did not return to the breathing bag during exhalation and revealed a ball-valve type behavior in the breathing circuit/airway unit. Deflating the balloon of the bronchial blocker relieved all symptoms and confirmed a primary airway cause of PEA.

In this case, we observed that a well-positioned bronchial blocker backed out of the left mainstem bronchus into a tracheal position. We hypothesize that dislodgement into the tracheal position led to profound air trapping behind an intermittent mechanical obstruction created by the blocker’s balloon. Because the cartilaginous rings above the carina are not circumferential, the trachea is distensible. During inspiration, high inflation pressures distend the trachea and allow gas to flow past the inflated blocker into the lungs. With the release of the inflation pressure, the trachea collapses during expiration. The misplaced bronchial blocker becomes a "tracheal blocker" and acts as a one-way valve preventing exhalation. As a form of "ultimate air-trapping," this "tracheal ball valve" produced effects on cardiovascular performance almost immediately. This proposed mechanism for a ball-valve obstruction (i.e., the impact of a distensible membranous portion of the trachea) remains a theory, albeit one that could be tested in animals.

In general, airway devices for lung isolation are vulnerable to dislodgement when placed on the ipsilateral side during surgery. This is true for double-lumen tubes and for bronchial blockers. However, dislodgement of a double-lumen tube usually only leads to loss of lung isolation rather than severe air trapping and cardiovascular collapse. Bronchial blockade necessitates use of an ipsilateral device, whereas a double-lumen tube usually allows contralateral placement. The author’s institution favors right-sided double lumen tubes as first-line airway devices (when circumstances allow) for surgery in the left chest, with acceptable safety and complication profiles (9). The urgency of the situation in this case precluded using a double-lumen tube, and the bronchial blocker initially was a very useful alternative strategy. However, this case illustrates that bronchial blockade carries unique risks. These include the potential for complete obstruction of the airway manifesting, in this case, as a primarily cardiovascular problem.

	Footnotes

 
Accepted for publication October 22, 2004.

	References

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1. Campos JH. Current techniques for perioperative lung isolation in adults. Anesthesiology 2002;97:1295–301.[Web of Science][Medline]
2. Campos JH. An update on bronchial blockers during lung separation techniques in adults. Anesth Analg 2003;97:1266–74.[Free Full Text]
3. Arndt GA, Kranner PW, Rusy DA, Love R. Single-lung ventilation in a critically ill patient using a fiberoptically directed wire-guided endobronchial blocker. Anesthesiology 1999;90:1484–6.[Web of Science][Medline]
4. Arndt GA, DeLessio ST, Kranner PW, et al. One-lung ventilation when intubation is difficult: Presentation of a new endobronchial blocker. Acta Anaesthesiol Scand 1999;43:356–8.[Web of Science][Medline]
5. Arndt GA, Buchika S, Kranner PW, DeLessio ST. Wire-guided endobronchial blockade in a patient with a limited mouth opening. Can J Anaesth 1999;46:87–9.[Web of Science][Medline]
6. Magill IW. Anaesthesia in thoracic surgery with special reference to lobectomy. Proc R Soc Med 1936;29:643–53.
7. Connery LE, Deignan MJ, Gujer MW, Richardson MG. Cardiovascular collapse associated with extreme iatrogenic PEEP in patients with obstructive airways disease. Br J Anaesth 1999;83:493–5.[Abstract/Free Full Text]
8. Marini JJ, Culver BH, Butler J. Mechanical effect of lung distention with positive pressure on cardiac function. Am Rev Respir Dis 1981;124:382–6.[Web of Science][Medline]
9. Hurford WE, Alfille PH. A quality improvement study of the placement and complications of double-lumen endobronchial tubes. J Cardiothorac Vasc Anesth 1993;7:517–20.[Medline]

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Anesthesia & Analgesia® is published for the International Anesthesia Research Society® by Lippincott Williams & Wilkins with the assistance of Stanford University Libraries' HighWire Press®. Copyright 2006 by the International Anesthesia Research Society. Online ISSN: 1526-7598   Print ISSN: 0003-2999