H1N1 influenza virus infection complicating a twin gestation: A case report

March 1, 2010

Influenza A virus is a type of ribonucleic acid, single-stranded, enveloped, orthomyxovirus that contains H and N surface glycoproteins.

Key Points

Influenza A virus is a type of ribonucleic acid (RNA), single-stranded, enveloped, orthomyxovirus that contains H and N surface glycoproteins. The virus generates new combinations of its surface glycoproteins continuously.1 Influenza A virus affects mammals and is transmitted through aerosol droplets and bodily fluids. The virus is a known cause of the "flu" and atypical pneumonia worldwide. The most common symptoms are fever with cough and/or sore throat. Recommendations for yearly vaccinations are well established. Pregnancy increases the risk for complications caused by influenza infection.

The Centers for Disease Control and Prevention (CDC) first identified cases of respiratory infections of the 2009 H1N1 influenza virus in the United States in April 2009.2 On July 11, the 2009 H1N1 influenza virus spread was considered pandemic. The World Health Organization (WHO) reported nearly 400,000 cases worldwide by October 11, 2009.3

According to a joint statement from the American Society for Reproductive Medicine (ASRM) and the CDC, complications from influenza can cause serious illness and even death in pregnant women.4 Pregnant women with 2009 H1N1 influenza have higher rates of hospitalization and death than the general population. As of October 2009, the CDC was aware of approximately 700 cases of 2009 H1N1 influenza in pregnant women since late April or early May 2009.5 A spokesperson for the CDC reported that about 100 pregnant women were admitted to intensive care units, and 28 pregnant women had died from the disease.

Case presentation

LK is a 35-year-old white woman, 28 weeks pregnant with twins. Her previous medical history was significant for asthma and kidney stones. Her obstetric history involves a vacuum-assisted vaginal delivery and a complete abortion. Her surgical, family, and gynecological history are noncontributory. LK's risk factors include advanced maternal age, twin gestation, and asthma.

The patient presented to Baptist Hospital in Miami, Florida, on June 7, 2009, and was complaining of a weeklong history of sinusitis and flu-like symptoms.

The patient had been taking azithromycin and Robitussin for 3 days before admission. Initial assessment revealed worsening symptoms of myalgia; dry, hacking cough; and elevated temperatures. Her temperature was 102.4° F, her pulse rate was 127 beats per minute, and her saturation on room air was 95% to 96%.

The patient denied any chest pain or shortness of breath, and there was no complaint of any obstetric symptoms. On physical exam, her lungs were clear without wheezes or rhonci, but she had faint crackles at lung bases. Chest x-ray showed decreased lung volume with no consolidation, pneumothorax, or pleural effusions.

Arterial blood gases showed a pH of 7.44, pO2 of 91, pCO2 of 26, and HCO3 of 17. Urinalysis showed greater than 80 mg/dL ketones, trace proteins, and negative for leukocyte esterase and nitrites. Fetal heart tones showed fetal tachycardia, with 170 to 175 beats per minute baseline and 160 to 165 beats per minute baseline in babies A and B, respectively. LK was admitted with a diagnosis of pneumonia secondary to no improvement of her clinical course, with elevated temperatures, despite antibiotics, and the findings on physical exam.

The patient was continued on her azithromycin 500 mg intravenous (IV) daily, and ceftriaxone 2 grams IV daily was added. Levalbuterol, a beta-adrenergic agonist, 1.25 mg nebulizer treatment was ordered 3 times daily as needed. Intravenous hydration was continued at 125 cc/hr with normal saline, and a regular diet was ordered. Guaifenesin 400 mg every 4 hours and 2 sputum cultures also were ordered. A continuous pulse oximetry was maintained, and routine vitals were taken.

The patient on the second day of admission had no improvement, and a pulmonary consult was ordered. Normal saline spray to improve her sinusitis and a repeat chest x-ray were ordered. The sputum cultures showed light growth of respiratory flora.

Results of the repeat chest x-ray showed bibasilar opacities, probable atelectasis, although pneumonia could not be ruled out. Recommendations were taken from pulmonary service, and the patient's clinical course began to deteriorate into worsening shortness of breath. Repeat arterial blood gases showed increasing hypoxemia, oxygen supplementation was given, and an infectious disease consult was called. A typical pneumonia workup showed negative results for mycoplasma (serum immunoglobulin), legionella (urine antigen), and influenza A and B (nasopharyngeal swab).

On June 12, 2009, the patient presented with worsening pulmonary status despite oxygen supplementation. The arterial blood gases showed an arterial partial pressure of 70 mm Hg. The patient was transferred to the intensive care unit for ventilatory support with BiPAP. Antenatal corticosteroids were started. On BiPAP, the patient respiratory condition was still deteriorating, and the plan was for intubation and mechanical ventilation.

Fetal antepartum surveillance using a biophysical profile was 2/8. A maternal fetal medicine consult was called, and the decision was made to deliver the twins under general anesthesia. At the time of cesarean delivery, there were viable male and female fetuses with both APGAR scores of 5, 6, and 8 at 1, 5, and 10 minutes, respectively. The patient was then transferred to the intensive care unit (ICU) and was continued on mechanical ventilation because of persistent hypoxemia.

Detailed discussion with family revealed a paternal history of exposure to and infection with 2009 H1N1 influenza virus. Despite a negative influenza A screening test, oseltamivir was started via nasogastric tube, and a nasopharyngeal swab was sent for real-time polymerase chain reaction (RT-PCR) for the detection of 2009 H1N1 influenza virus. LK was diagnosed with acute respiratory distress syndrome (ARDS), which was confirmed by repeat chest x-ray.

Mechanical ventilation was continued for approximately 10 days while the patient's respiratory function improved. Oseltamivir was given for the recommended 5-day regimen, and the RT-PCR diagnostic test confirmed the 2009 H1N1 influenza virus infection.

Once LK was extubated, she was transferred to a step-down unit and continued her clinical improvement. Three days afterward, LK was discharged home and showed no respiratory sequelae.

Babies A and B were in the neonatal ICU and are currently at home with no signs of infection with the H1N1 influenza virus.