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Case Reports  |   June 1997
Laser Treatment of Endobronchial Lesions 
Author Notes
  • Received from the Departments of Anesthesiology and Pain Management, Baylor University Medical Center and University of Texas Southwestern Medical Center, Dallas, Texas. Submitted for publication August 21, 1996. Accepted for publication January 30, 1997.
  • Address reprint requests to Dr. Ramsay: Department of Anesthesia, Baylor University Medical Center, 3500 Gaston Avenue, Dallas, Texas 75246.
Article Information
Case Reports
Case Reports   |   June 1997
Laser Treatment of Endobronchial Lesions 
Anesthesiology 6 1997, Vol.86, 1387-1390. doi:
Anesthesiology 6 1997, Vol.86, 1387-1390. doi:
The neodymium:yttrium-aluminum-garnet (Nd:YAG) laser is used for palliative and therapeutic management of endobronchial lesions. The authors report three cases of what appear to be pulmonary venous gas emboli (PVGE) during endobronchial Nd:YAG laser therapy.
Case Reports 
Case 1 
A 75-kg man, aged 55 yr, with a scarred fibrotic residual left lung after a severe childhood infection that resulted in complete collapse of the left lung presented with a bronchopleural fistula after a stump infection. The patient was asymptomatic until aged 54 yr, at which time he developed a Pseudomonas infection of the remaining lung tissue that caused the formation of a bronchopleural fistula and an empyema. The empyema was drained, and the infection resolved with intravenous antibiotics. Nd:YAG laser therapy was proposed to develop an endobronchial tissue reaction so that a sealant plug could be set permanently in the bronchial stump, thereby occluding the fistula.
After placement of standard monitors and a radial arterial catheter, anesthesia was induced with propofol and mivacurium. The patient's trachea was intubated with a standard 9.0-mm endotracheal tube. Anesthesia was maintained with a propofol infusion (150–200 micro gram [center dot] kg sup -1 [center dot] min sup -1) and intermittent doses (0.2 mg/kg) of mivacurium to facilitate initial insertion of the rigid bronchoscope. Topical anesthesia was applied to the airway. An initial assessment of the bronchial stump was performed using a fiberoptic bronchoscope passed through an adapter attached to the endobronchial tube. The endotracheal tube was then replaced with a rigid ventilating bronchoscope with side ventilation slits (Shapshay Universal Ventilating Laser Bronchoscope Karl Stortz, Endoscopy-America, Inc., Culver City, CA).
Ventilation was provided using a Venturi system with a modified Sanders injector attached to the side arm of the bronchoscope. [1 ] The inspired oxygen concentration was kept as low as possible while maintaining the oxygen saturation at greater than 95%. An air-to-oxygen mixture was delivered by attaching the anesthesia circuit to the entraining side port of the bronchoscope. The inspired oxygen concentration delivered was approximately 25–35%. During the course of the laser treatment, moderate bleeding occurred. The rigid bronchoscope was advanced into the bronchial stump, and additional laser treatments were delivered. During one pulse of the laser, the patient was noted to have an acute decrease in blood pressure to 40/20 mmHg, severe bradycardia to 20 beats/min, and ST segment elevation in lead II of the electrocardiogram. The oxygen saturation was 95% immediately before the event. The procedure was terminated, but a cardiac arrest followed. The patient was quickly resuscitated within 2 min using standard advanced cardiac life support protocol.
The patient awoke but was noted to be confused and to exhibit a left hemiplegia. Computerized tomography scan of the brain revealed a gas embolus in the region of the right middle cerebral artery. Postoperatively, the patient recovered cognitive function but continued to exhibit a residual left hemiplegia.
Case 2 
A 59-kg man, aged 61 yr, with a history of a rapidly progressing bronchogenic carcinoma presented for palliative management of an endobronchial tumor occluding his right mainstem bronchus, causing severe dyspnea and complete collapse of the right lung. After placement of routine monitors and a left radial artery catheter, anesthesia was induced and maintained with intravenous propofol (150–200 micro gram [center dot] kg sup -1 [center dot] min sup -1) and mivacurium (0.2 mg/kg), and topical anesthesia was applied to the airway. The surgeon assessed the lesion by using a flexible bronchoscope; the endotrachial tube was then removed, and a rigid ventilating bronchoscope with Sanders injector attachment was placed into the trachea. Baseline hemodynamics were pulse rate, 75–81 beats/min; blood pressure, 120/60 mmHg-1.10/55 mmHg. The lungs were ventilated with an air-to-oxygen mixture that provided 40% oxygen entrained from an anesthesia circuit to maintain an oxygen saturation of 96%.
Approximately 90 min into the procedure, the surgeon encountered bleeding and stopped using the laser. Ventilation was continued through the bronchoscope, which was advanced into the right main stem bronchus. The patient rapidly developed profound bradycardia to 40 beats/min, hypotension to 60/20 mmHg, and ST segment elevation in lead II of the electrocardiogram. There was marbling of the skin of the upper extremities. The oxygen saturation initially remained at 96%. The procedure was terminated; the rigid bronchoscope withdrawn, and an endotracheal tube placed. Resuscitation was initiated, and inspired oxygen was increased to 100%. The patient responded to resuscitation efforts within 1 min. Initially on emergence, the patient followed simple commands but was encephalopathic and had a left-sided weakness.
A grand mal seizure occurred 15 min after arrival to the postanesthesia care unit. Computerized tomography of the brain demonstrated an intraparenchymal gas bubble present in the right frontoparietal region (Figure 1). The neurologic deficits slowly resolved, with only a slight residual weakness in the left upper extremity. The patient returned to the operating room on postoperative day 11 for repeated ablation of the tumor, which was found to be extending across the carina into the left main stem bronchus. The same anesthetic plan was implemented without incident.
Figure 1. Postoperative computerized tomography scan showing intracerebral gas after Nd: YAG laser bronchoscopy of patient #2.
Figure 1. Postoperative computerized tomography scan showing intracerebral gas after Nd: YAG laser bronchoscopy of patient #2.
Figure 1. Postoperative computerized tomography scan showing intracerebral gas after Nd: YAG laser bronchoscopy of patient #2.
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Case 3 
A 60-kg woman presented with a metastatic neoplasm to the left main stem bronchus. Palliative therapy was planned to debulk the tumor and open the bronchus using the Nd:YAG laser. After placement of standard monitors and an arterial catheter, the patient was induced with propofol and mivacurium. The trachea was intubated with a 9.0-mm endotracheal tube. Anesthesia was maintained with a propofol infusion (150–200 micro gram [center dot] kg sup -1 [center dot] min sup -1), and spontaneous ventilation was allowed to return and was assisted as necessary.
The surgeon first evaluated the tumor with the fiberoptic bronchoscope. The endotracheal tube was then removed, and the rigid ventilating bronchoscope was inserted. Spontaneous ventilation was maintained with intermittent, gently assisted hand ventilation via a circle circuit attached to the side arm of the bronchoscope, using air and oxygen to maintain oxygen saturation above 95%. Laser resection proceeded with removal of a large amount of tumor tissue. Significant bleeding was encountered, and the patient had a transient decrease in oxygen saturation to 85%. Hand ventilation with 100% oxygen returned the oxygen saturation to 95%, but the patient suddenly became bradycardic to a rate of 30 beats/min and hypotensive to a blood pressure of 40/20 mmHg, with ST segment elevation noted in lead II of the electrocardiogram. The patient was resuscitated within 2 min; the ST segments returned to baseline after 15 min, as did the blood pressure and pulse rate.
On recovery, the patient was noted to be confused and exhibited a left hemiplegia. The neurologic deficit returned to normal after 20–30 min, and a brain computerized tomography scan obtained after symptom resolution was normal.
Discussion 
Two reviews reported several deaths during Nd:YAG laser therapy in 1,951 patients with endobronchial tumors who underwent 3,428 procedures. [2,3 ] These deaths resulted from “cardiovascular decompensation,” described as episodes of severe bradycardia, shock, infarction, and cardiac arrest. The descriptions of these episodes are very similar to the cases of possible PVGE reported here and to those described previously in the literature. [4–6 ]
In 1929, Van Allen [7 ] performed extensive studies in dogs given pulmonary venous gas emboli. These dogs experienced one of two responses, either 1) acute hypertension and dysrhythmias, followed by hypotension and cardiac arrest, or 2) blindness, seizures, hemiplegia, and death. The distribution of gas introduced into the pulmonary vein of the anesthetized dogs was dependent on body position. In the horizontal, supine position, air was distributed mainly to the coronary arteries, and in the vertical or standing position, to the cerebral circulation.
Evans et al., [8 ] in a study involving upright ventilated cats, found that air infused into the left ventricle caused one of two responses, either 1) the cat exhibited an acute increase in blood pressure, pulse rate, and left ventricular contractile force and developed arrhythmias, or 2) the cat exhibited an immediate decrease in blood pressure and pulse and no arrhythmias. They concluded from this study that gas embolism to the cerebral circulation resulted in the hyperdynamic responses, whereas emboli to the coronary circulation resulted in a depressed response. A follow-up study was performed, and this confirmed that air infused into the cerebral circulation caused an increase in blood pressure, increased left ventricular contractility, and arrhythmias. [9 ]
In the cases reported here, patients were in a supine position with a 20 degrees head-up tilt and exhibited symptoms of coronary and cerebral emboli. The elevated ST segment in lead II could be the result of a gas embolus to the right coronary artery, the most superior coronary artery in a supine patient. All three patients described presented initially with a left-sided hemiplegia on emergence, which would correspond to an embolus entering the right carotid artery and traveling to the right brain, resulting in left-sided neurologic symptoms.
The diagnosis of PVGE in the three patients was based on the following signs: acute onset of bradycardia, hypotension, ST segment elevation on the electrocardiograph, maintenance of oxygen saturation before cardiac decompensation, and a new neurologic deficit on emergence.
The incidence of PVGE with endobronchial use of the Nd:YAG laser may be a more common complication than has been previously recognized and may have multiple etiologies. The proposed cause of gas embolism in the first case report is continued laser treatment after bleeding was encountered. The Nd:YAG laser has a coaxial gas channel that delivers compressed helium to the tip for cooling purposes. The laser treatment caused an opening in a pulmonary vein, and continued treatment with the laser with coolant gas flows of 800 ml/min resulted in a helium gas embolus. The pressure generated by the coolant gas flow at 400 ml/min has been found to be in excess of 500 mmHg measured at the tip of the the coaxial gas channel of the laser. [6 ] This pressure gradient could force gas into an open pulmonary vein when the laser tip is wedged into position. The entrance of gas follows a direct path to the left heart, coronary arteries, aorta, brain, and systemic circulation. This patient's neurologic deficit was a permanent one, probably because the physical properties of helium, an insoluble inert gas, limited its reabsorption from the cerebral circulation.
In the second case report, bleeding was encountered, and laser treatment was stopped, but ventilation was continued using a modified Sanders injector attached to a rigid bronchoscope. The surgeon advanced and wedged the bronchoscope into the right main stem bronchus to tamponade the bleeding; cardiovascular decompensation occurred immediately. The proposed etiology of PVGE in this case is that a distal, high-pressure system developed in the obstructed bronchus resulting in the direct passage of air and oxygen into the open pulmonary venous circulation. A Sanders injector can deliver 28 cm of H2O inspiratory pressure with an inspiratory flow rate of 140 l/min. [10 ] The rigid ventilating bronchoscope has side-ventilation slits to allow pressure dissipation and bilateral lung ventilation to occur when the tip of the bronchoscope is advanced into a main stem bronchus. [11 ] These vents may have been partially obstructed and failed to adequately decompress the pressurized lung. This patient was noted to have marbling of the skin immediately after cardiac decompensation began. Marbling is a sign associated with systemic gas emboli when air bubbles present in subcutaneous tissues cause venous stasis. [4,5 ] The gas embolism in this incidence was thought to be an air-to-oxygen mixture. The oxygen absorbed rapidly, resulting in a small, residual deficit caused by the slower absorption of the air component of the gas bubble.
In the third case report, the patient was allowed to breathe spontaneously, with occasional gentle assistance and hand ventilation with an air-to-oxygen mixture. During a brief desaturation, the patient was more aggressively hand ventilated with 100% oxygen, and the oxygen saturation returned to 95%; however, cardiac decompensation occurred immediately. This gas embolus was probably 100% oxygen; therefore, the neurologic sequelae resolved quickly and completely as the oxygen was rapidly absorbed.
On the basis of these three case reports, our preliminary conclusion of methods to decrease the incidence of PVGE during endobronchial laser therapy when bleeding is encountered is that airway pressure should be minimized and the bronchoscope withdrawn above the carina. A spontaneous ventilation technique may reduce the extent of PVGE. However, lung tissue involved with extensive neoplasm may lose its normal elasticity, and any abnormal communication formed between the pulmonary venous system and the airway may be held open and air entrained, even during spontaneous ventilation. [7,8 ] The standard practice of laser surgery has been to use minimal concentrations of oxygen to reduce the risk of an airway fire. [12 ] The use of high concentrations of inspired oxygen should be considered when bleeding is encountered, and the risk of airway combustion should be weighed against the risk of possible PVGE.
References 
References 
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Van Allen CM, Hrdina LS, Clark J: Air embolism from the pulmonary vein. Arch Surg 1929; 19:567-99.
Evans D, Hardenbergh E, Hallenbeck JM: Cardiovascular effects of arterial air embolism, Arterial Air Embolism and Acute Stroke. Edited by Hallenbeck JM, Greenbaum LJ. Rockville, MD, Undersea Med Soc, 1978, pp 20-33.
Evans D, Kobrine A, Weathersby P, Bradley M: Cardiovascular effects of cerebral air embolism. Stroke 1981; 12:338-441.
Giesecke AH, Gerbershagen HU, Dortman C, Lee D: Comparison of the ventilating and injection bronchoscopes. Anesthesiology 1973; 38:298-303.
Benumoff JL: Anesthesia for special elective procedures, Anesthesia for Thoracic Surgery, 2nd Edition. Edited by Benumoff JL. Philadelphia, WB Saunders, 1995, pp 500-1.
Warner ME, Warner MA, Leonard P: Anesthesia for Neodynium: YAG (nd:YAG) laser resection of major airway obstructing tumors. Anesthesiology 1984; 60:230-2.
Figure 1. Postoperative computerized tomography scan showing intracerebral gas after Nd: YAG laser bronchoscopy of patient #2.
Figure 1. Postoperative computerized tomography scan showing intracerebral gas after Nd: YAG laser bronchoscopy of patient #2.
Figure 1. Postoperative computerized tomography scan showing intracerebral gas after Nd: YAG laser bronchoscopy of patient #2.
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