Hantavirus pulmonary syndrome

Joseph Kaminski, DO, R. Ryncarz, MD, B. Carlin, MD, FCCP, B. Veynovich, DO, A. Zikos, DO, P. Kaplan, MD, FCCP--Allegheny General Hospital, Pittsburgh, Pennsylvania, USA

Introduction: Hantavirus pulmonary syndrome (HPS) is a febrile illness characterized by bilateral interstitial pulmonary infiltrates which often results in adult respiratory distress syndrome (ARDS). We present a case of HPS refractory to conventional mechanical ventilation including pressure control and inverse ratio ventilation. High Frequency Oscillatory Ventilation (HFOV) was used with a successful outcome.

Case Presentation: A previously healthy 43 yr. old man presented with a 10 day history of non productive cough, malaise, headache, and a low grade fever. The patient was seen in an emergency department where CXR was noted to be normal. The patient was placed on a macrolide antibiotic and discharged home.

He represented to another hospital within 24 hours with worsening shortness of breath, fever of 102 F, and bilateral infiltrates on CXR. The patient developed hypoxemic respiratory failure and was intubated and placed on mechanical ventilation. The patient had been hypotensive with systolic pressures in the 70's but improved with volume resuscitation and dopamine. WBC count was 20.3 with a Hgb of 17.1, Hct 52 and platelets 92,000. LFT's were markedly elevated with AST 424 and ALT 435. Urine, blood, and BAL cultures were sterile. Urinalysis, hepatitis panel, and HIV testing were normal. Broad spectrum antibiotics were started. Due to persistent hypotension a Swan-Ganz catheter was inserted which revealed a cardiac index of 1.6 L/min/[m.sup.2], SVR 1204 dyne/sec/[cm.sup.-5], PCWP 15 mmHg, PA pressure 37/20 mmHg and CVP 15 mmHg. Despite high levels of PEEP, oxygen saturation remained [is less than] 80%. The patient was transferred to our facility for further evaluation and treatment.

On arrival, physical exam revealed a well developed man who was sedated on mechanical ventilation with a BP of 75/50 mmHg. The patient had coarse breath sounds bilaterally with few crackles, a normal S1/S2 without murmurs, rub, or gallop. Abdominal exam was normal and no skin rash or petechiae were noted. CXR progressed from an interstitial pattern to a diffuse alveolar pattern with severe bilateral involvement, small bilateral effusions and a normal cardiac silhouette. Initial ABG's were PH 7.27, PCO2 38 torr, PO2 45 torr, saturation 75%, on pressure control ventilation with an inspiratory pressure of 30 cm H20, I:E 1:2, Fio2 100%, PEEP 12.5 cm H20, rate 20. Mixed venous saturation was 44%. An echocardiogram showed a hyperdynamic underfilled left ventricle with an ejection fraction of 70%. Because of the low cardiac index, the patient received further volume resuscitation and dobutamine was started and titrated with improvement in CI to 2.3 L/min/[m.sup.2]. He was continued on broad spectrum antibiotics. Despite progressing to inverse ratio ventilation and PEEP of 17.5 cm H20, oxygen saturations remained 75-80%. Chemistries were normal except for a BUN of 30, creatinine of 1.7 and albumin 2.3. PT and PTT were 20.7 and 41 respectively, while CBC showed an elevated white count of 31.9, Hgb 18.2, Hct 54% and plts 58,000. Differential was remarkable for increased metamyelocytes. Serologies to rule out vasculitis were normal. Further history was obtained revealing that file patient had a recent exposure to mouse feces while renovating the basement of a building. The patient's family consented to enrollment into the HFOV trial and the patient randomized to HFOV. Prior to the use of HFOV, consideration was given to using ECMO. Initial HFOV settings were 5 Hz, 33% inspiratory time, MAP 40 cm H20, 100% Fio2 and amplitude of 75. Within 20 minutes of instituting HFOV, oxygen saturation improved to 93% with a PO2 of 87 mmHg and the Fio2 was gradually decreased. The patient continued to improve over the next several days. Hantavirus-specific immunoglobulin M was positive which was confirmed by the CDC. After spending 6 days on HFOV, the patient was converted back to conventional mechanical ventilation and eventually weaned. He was transferred to a rehabilitation facility and discharged home approximately 3 months after presentation.

Discussion: Hantavirus Pulmonary Syndrome (HPS) is an illness caused by the Sinombre virus and results from inhalation of aerosolized feces of (he deer mouse, the main carriers of the virus. Mortality rates of 40-70% have been documented. Treatment is mainly supportive with inotropes, fluids, and mechanical ventilation. The use of intravenous ribavirin is currently tinder investigation. ECMO has been implemented as salvage treatment with some success.

HFOV is a mode of ventilation accepted for use in neonates and pediatric patients with acute lung injury and respiratory failure. It's use is being investigated in adults with ARDS. Proposed mechanisms of improvement include ability to recruit alveloi with an increased mean airway pressure while limiting peak airway pressure. It has been shown to improve oxygenation and limit pulmonary barotrauma.

Conclusions: This case demonstrates a patient with ARDS secondary to Hantavirus Pulmonary Syndrome who responded well to HFOV. In this instance it was beneficial in a patient with hypoxemic respiratory failure refractory to other modes of mechanical ventilation. Further investigation into its use is ongoing, including the Randomized Prospective Multicenter Oscillator ARDS Trial (MOAT 2) using the SensorMedics model 3100B HFOV in which our institution is a participant. HFOV may represent a rescue technique in ARDS, particularly in Hantavirus Pulmonary Syndrome and may be an alternative to ECMO in severe cases refractory to other modes of therapy.

COPYRIGHT 2000 American College of Chest Physicians
COPYRIGHT 2001 Gale Group