Pathogenesis of Cerebral Air Embolism during Neodymium-YAG Laser Photoresection

tumors and lobulation is not seen.' In addition, enhanced visualization of the masses on postcontrast computerized tomography supports the diagnosis of intrathoracic extramedullary hematopoiesis as demonstrated in our case. Although invasive diagnostic procedures, including thoracotomy and aspiration needle biopsy have been used," they are usually not necessary and are potentially hazardous because of the highly vascular nature of the thoracic masses. At thorocotomy Andras et al6 found the blood supply to derive from intercostal arteries and the esophageal plexus. Venous drainage was into the azygous system. In several reports surgical resection has been complicated by extensive hemorrhage requiring multiple transfusions." Our case provides a dramatic example of the hemorrhagic potential of this condition. Treatment is required only in the presence of complications. Treatment may in fact be deleterious due to removal of a compensatory source of erythropoiesis and exacerbation of the underlying anemia. Extramedullary hematopoietic tissue is highly radiosensitive, and relatively small doses of radiation have been effective after surgical decompression in cases of spinal cord compression.' In our patient radiotherapy was administered to prevent recurrent hemorrhage after surgical control of the acute bleeding. It is unclear whether there was some factor in our patient which provoked the hemorrhage resulting in massive hemothorax. The lacerations in the capsule of the larger mass seen at thoracotomy may have resulted from spontaneous rupture. The role of the apparently superficial trauma that she sustained prior to admission remains speculative. Awareness of this potential complication of intrathoracic extramedullary hematopoiesis may make it possible to treat future cases with radiation and chest tube drainage without resorting to thoracotomy: ACKNOWLEDGEMENT: We thank Ms. Kathy Dwenger and Ms. Ruth Schweky for secretarial assistance. REFERENCES

1 Luyendijk ~ Went L, Schaad HDG. Spinal cord compression due to extramedullary hematopoiesis in homozygous thalassemia. J Neurosurg 1975; 42:212-16 2 Braverman AS, McCurdy PR, Manos 0, Sherman A. Homozygous beta thalassemia in American blacks: the problem of mild thalassemia. J Lab Clin Med 1973; 81:857-66 3 Verani R, Olson J, Moake JL. Intrathoracic extramedullary hematopoiesis. Am J Clin Patho11980; 73:133-37 4 DaCosta JL, Loh YS, Hanam E. Extramedullary hematopoiesis with multiple tumor-simulating mediastinal masses in hemoglobin E-thalassemia disease. Chest 1974; 65:210-12 5 Ben-Bassat I, Hertz M, Selzer G, Ramot B. Extramedullary hematopoiesis with multiple tumor-stimulating mediastinal masses in a patient with Jj-thalassemia intermedia. Isr J Med 1977; 13:1206-10 6 Andras C, Klassen K£ Holaday WJ. Tumor simulating intrathoracic extramedullary hematopoiesis. Ann Thorac Surg 1970; 10:7580 7 Case Records of the Massachusetts General Hospital. N Engl J Med 1963; 278:782-91 8 Ask-Upmark E. Tumor simulating intrathoracic heterotopia of bone marrow: Acta Radiol 1945; 26:425-40 9 Sorsdahl as, Taylor PE, Noyes WD. Extramedullary hematopoiesis, mediastinal masses, and spinal cord compression. JAMA 1964; 189:343-47

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Pathogenesis of Cerebral Air Embolism during Neodymium-VAG Laser Photoresection* David] Ross, M.D.;t Zab Mohsenifar, M.D., F.C.C.E;:j: Ralph L Potkin, M.D., F.C.C.E;§ Warren L. Roston, M.D., F.C.C.E;§ Samuel M. Shapiro, M.D.;II and]ohn M. Alexander, M.D., .EC.C.E1f

We describe a case of air embolism complicating neodymium- YAG laser resection of an endobronchial carcinoid tumor, A 27-year-old man experienced an acute neurologic syndrome during laser photoresection which responded to acute hyperbaric therapy (Chest 1988; 94:660-62)

T

he phenomenon of arterial air embolism has been described as a sequela to major thoracic trauma, diving accidents, selective arterial angiography and central venous catheter malfunctions. 1-3 Recently arterial air embolism has been reported as a consequence of transthoracic needle lung aspiration. 4 In addition, the occurrence of cerebral air -embolism has been reported with transbronchial lung biopsy in a patient with miliary tuberculosis and, recently in a patient with pulmonary amyloidosis.v' In this report we present a case of acute air embolism complicating YAG laser photoresection of an endobronchial carcinoid. CASE REPORT

The patient is a 27-year-old, heterosexual, nonsmoking, Caucasian man who was admitted with persistent left lower lobe (LLL) pneumonia. Fiberoptic bronchoscopic examination was performed and demonstrated a large, exophytic, and hypervascular lesion totally occluding the LLL bronchus. The patient reported a long history of flushing associated with childhood "hyperactivity" and "panic attacks" and had been given various tricyclic medications. He described a previous episode of "tachycardia" while taking these medications, which required brief treatment with propranolol. On physical examination, his systemic blood pressure was 160/70 mm Hg, pulse rate 88/min, respirations 20/min, and rectal temperature was 38.3°C. Examination of his head and neck was unremarkable. Cardiac examination demonstrated a regular rhythm, normal S. and S2' without murmurs. There was evidence of decreased breath sounds in the area of the LLL. The results of remainder of the examination were normal. The patients data base included a WBC count of 23,900/cu mm, with a left shift. The electrolytes and hemoglobin values were normal.

Course Approximately six weeks prior to his transfer to our institution, the patient had developed fever (40.0°C), pleuritic chest pain, and a productive cough of green sputum which failed to resolve on treatment with oral erythromycin on an outpatient basis. At another institution, the patient was noted to have a LLL pneumonia and pleural effusion, while the sputum demonstrated "mixed flora." He was treated with IV ampicillin and metronidazole. His course was

*From the Division of Pulmonary Medicine, Cedars-Sinai Medical Center, Western Center for Hyperbaric Medicine, University of California, Los Angeles School of Medicine, Los Angeles. tPulmonary Fellow: :j:Associate Professor of Medicine. §Staff Physician. IIStaff Anesthesiologist. 1fAssistant Clinical Professor of Medicine. Pathogenesis of Cerebral Air Embolism (Ross et al)

complicated by a subsequent loculated empyema requiring rib resection and open drainage. On the second postoperative day, fiberoptic bronchoscopic study was performed and demonstrated a large, hyperemic endobronchial lesion totally occluding the LLL bronchus. All obtained biopsy specimens were nondiagnostic, A lobectomy was deemed hazardous owing to the recent empyema and risk of developing a stump infection. The patient was therefore transferred to our institution for photoresection and biopsy of the obstructing lesion (presumably an adenoma) to establish patency of the LLL bronchus and to facilitate resolution of the pneumonia. The patient underwent neodymium-YAG laser resection after multiple endobronchial biopsies with frozen sections and Wang needle aspirations of the lesion were obtained. Preoperatively the patient had received meperidine, hydroxyzine HCI, atropine sulfate, and fentanyl citrate; while anesthesia was maintained with atracurium besylate and isoHurane. Positive-pressure ventilation was maintained using a volume-anesthesia ventilator and a 35 percent fractional inspired O2 , Nd-YAG laser power was used in the range of 40 to 50 W and time exposure of O. 7 to 0.8 second. A total of 1,268 W/s was used to establish patency of the bronchus. Purulent secretions were noted emanating from the LLL segments. Approximately 40 to 60 mlof hemorrhage occurred during the procedure, which was well controlled with aliquots of 1:20,000 epinephrine and the hemostatic effect of the YAG laser. Near completion of the procedure, ST segment depression was noted on the ECG, followed by an episode of supraventricular tachycardia (SVf) with intermittent wide complexes at a rate of 150 to 200/min and a concomitant decrease in systolic blood pressure from 130 to 95 mm Hg. The SVf was converted with propranolol and lidocaine infusion. Oxygen saturation was 97 percent by oximetry A "Hush" was noted on the patients malar eminence associated with a blanching over the abdomen. Anesthesia was immediately reversed, and an anisocoria (OD = 4 mm;OS = 7 mm) consistent with a Homers syndrome, a left homonymous hemianopsia, left dense hemiparesis, and left ankle clonus were noted. Funduscopic study results were unremarkable. The patient was given dexamethasone (Decadron), 20 mg IVE and 250 ml of 5 percent albumisol, while a GE-9800 head CT scan, performed without contrast material, was found to be unremarkable. A two-dimensional cardiac echocardiogram showed no thrombus or valvular lesions. A presumed diagnosis of acute .air embolism was made. The patient was transferred via helicopter at a reduced altitude, receiving 100 percent O 2 , to a nearby hyperbaric center. He was treated initially with a US Navy Standard Table No. 6 (maximum depth of 60 ft, with a 1. ft/min ascent) approximately four hours after the event. It was thought that the preferred therapy for an air embolism, a Table No. 6A (maximum depth 165 ft), would be hazardous in view of the residual LLL obstruction and the risk of further embolization during the rapid ascent (26 ftlmin) from 165 to 60 ft. Marked improvement in motor function was noted almost immediately on reaching .2.8 atm. The patient received three additional hyperbaric treatments over the ensuing two days, with complete resolution of all motor defects and only subtle residual visual field defects. Magnetic resonance imaging (MRI) demonstrated two small defects in the region of the right frontal corona radiata appearing consistent with "lacunar infarctions." Serial CPK enzymes increased to a maximum of472 U/L, however, were totally of the MM fraction. No further ECG abnormalities occurred. Additional laboratory values revealed a serum: serotonin level of 129 ng/ml (normal: 50-,175 ng/ml), 24-hour urine study for 5-hydroxyindoleacetic acid (5-HlAA) of 4.9 mg (normal;<16 mg/24 hr), AM serum cortisol of 15.3 f.tg/dl (normal: 5 to 25 f.t/dl); and serum gastrin level of 32 pg/ml (normal: 0 to 200 pg/ml), The patient subsequently underwent a left pneumonectomy for what was determined on pathologic examination to be a malignant carcinoid tumor involving two carinal lymph nodes. There was no evidence of bronchial perforation on pathologic examination.

DISCUSSION

Although the "acute carcinoid syndrome" has been previously reported during flexible fiberoptic bronchoscopy in a patient with an endobronchial carcinoid' and was also a clinical consideration in our patient, this cause appears unlikely: Serotonin is reported to cause hypertension in the carcinoid syndrome, whereas hypotension has been attributed to the effects of bradykinin, histamine, and tachykinins," Also, serotonin, as mediated through norepinephrine release, and histamine may induce arrhythmias," These mechanisms appear remote in light of the normal measured values for serotonin and 5-HlAA in our patient and no severe hemodynamic aberration. In our case, an air embolism presumably occurred as a result of positive-pressure ventilation during laser photoresection of a highly vascular tumor. The introduced venous air may potentially cause arterial embolism by passing through a patent foramen ovale, which is present in 27.3 percent of the general population.w A two-dimensional echocardiogram did not reveal a septal defect in our patient. Alternatively large quantities of venous air may traverse the pulmonary capillaries and reach the pulmonary venous effluent. The observed initial tachyarrhythmia and ST segment depression may be attributed to transient coronary artery involvement. The "pale discoloration over the abdomen" is consistent with the marbling of the skin seen when subcutaneous air bubbles cause venous stasis. We do not believe that Wang needle aspirations nor endobronchial biopsies contributed to the occurrence of air embolism, since these procedures were done at the inception, 21/2 hours prior to the manifestations of embolism. The marked neurologic improvement in this patient when treated in a hyperbaric chamber is highly suggestive of an acute air embolism. We conclude that this potentially catastrophic event may complicate an endobronchial procedure such as Nd-YAG laser photoresection. Early recognition and intervention may prevent grave outcomes. REFERENCES

1 Thomas AN, Stephens BG. Air embolism: a cause of morbidity and death after penetrating chest trauma. ] Trauma 1974; 14: 633-37 2 Menkin M, Schwartzman R]. Cerebral air embolism. Arch Neuro11977; 34:168-70 3 Peters ]L, Armstrong R, Bradford R, Gelister ]K. Air embolism: a serious hazard of central venous catheter systems. Intensive Care Med 1984; 10:261-62 4 Peters E], Boyars MC. Arterial air embolism after a percutaneous needle lung aspiration. I Hyperbaric Med 1986; 1:151-55 5 Erickson AD, Irwin RS, Teplitz C, Corrao WM, Taupey ]'1: Cerebral air embolism complicating transbronchoscopic lung biopsy: Ann Intern Med 1979; 90:937-38 6 Strange C, Heffner ]E, Collins BS, Brown FM, Sahn SM. Pulmonary hemorrhage and air embolism complicating transbronchial biopsy in pulmonary amyloidosis. Chest 1987; 92:36768 7 Sukumaran M, Wilkinson ZS, Christianson L. Acute carcinoid syndrome: a complication of flexible fiberoptic bronchoscopy. Ann Thorac Surg 1982; 34:702-05 8 Longnecker M, Roizen MF. Patients with carcinoid syndrome. Anaesth Clin North Am 1987; 5:313-37 9 Houston DS, Van Houtte PM. Serotonin and the vascular system: CHEST / 94 / 3 / SEPTEMBER, 1988

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role in health and disease, and implications for therapy. Drugs 1986; 31:149-63 10 Hagen PT, Scholz DC , Edwards WD . Incide nce and size of patent foramen ovale during the first ten decades of life: an autopsy study of 965 normal hearts. Mayo Clin Proc 1984; 59: 17-20

Haziness of the Right Hemithorax in a Newborn* Robert L. Hopkins, M .D .;t and Scott H. Davis, M.D ., F.C .C.P.:f:

We describe a neonate with an acces sor y diaphragm, a rare congenital anomaly. It almost always occurs in th e righ t hemithorax, which appears diffusely hazy on the an terior chest roentgenogram. The lateral chest roentgenogram is essential in the diagnosis of this condition. (Chest 1988; 94:662-63) A ccessory diaphragm is a rare congenital pulm onary anom aly that may be det ect ed as an isolate d roent genographic finding in asymptomatic ind ividu als or it may presen t in association with major cardiopulmonary malformations. Usuall y occurring on th e right, th e accesso ry diaphragm is composed of conn ective and mu scular tissue . It arises from

1'1

*From Tulane University School of Med icine and Medical Cen ter, New Orleans. t Associate Professor of Pedi atrics and Nutri tion; Director, Pediatric Intensive Care Unit. :f:Assistant Professor of Pediatrics, Section of Pulmonology, Department of Pediatr ics. Reprint requests: D r. Hopkins, 1430 Thlane Avenue, New Orleans 70112

th e anterior diaph ragm and exte nds cephalad and dorsally to insert on th e posterior chest wall. Roen tgenographic identification of th e accessory diaphragm requires a lateral chest roentgen ogram . We present a case of acce ssory diap hragm occur ring in a neonate with transient respiratory distress. The initial chest roentgenograms did not include a late ral view, leading to diagnostic confusion regarding diffuse haziness over the right hemithorax. CASE REPORT

An ll-day-old boy was referred to the Louisiana Pediatric Pulmonary Ce nter (LPPC) for evaluation of persistent haziness in the right hemith orax. H e had bee n delivered by caesarean section because of marginal placenta pr evia and breech presentation. His trachea was intubated in th e deliver y room because of mild respirato ry distress. His condition quickly improved and he was extubated shortly after transport to a nearby Neonatal Int ensive Care Unit (NICU). Supp lemental oxygen was discontinued within 48 hours. Upon admissio n to the NICU , physical examination revealed a slightly increased respiratory rate with normal breath sounds. Results of the cardiac examination were norm al. Initi al ante roposterior (AP) chest roentgenogram showed a diffuse hazines s over the right hemithorax which did not change during the hospitalization. The child was discharged in good condition on the sixth day of life. At the LPPC, physical examination showed no abnormality except for slightly decreased breath sounds over the right upper lobe. The AP chest roen tgenog ram was unchanged from those during his hospitalization (Fig 1, left). A lateral chest film (Fig 1, right ) was obtained for the first time. DISCUSSION

Accessory diaphragm is an uncommon congenital pulmonary anomaly th at may be discovered as an incid ental finding

FIGURE 1. AP chest roentgenogram (left ) shows a diffuse hazine ss over the right hemithorax and a slight shift of th e med iastinum to the right. The lateral chest roent genogram (right) shows an ant erio r homogene ous den sity with a sharp ly defined border.

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Haziness of Right Hemithorax in a Newborn (Hopkins, Davis)