One Year of Experience with H1N1 Infection: Clinical Observations from a Tertiary Care Hospital in Northern India.

Sir,

We describe the clinical and demographic characteristics of patients with H1N1 infection admitted in our hospital from May 2009 to May 2010.

Flu-like illness was reported by 19,279 patients, but testing for H1N1 using real-time reverse-transcriptase–polymerase-chain-reaction (RT-PCR) assay was done in 11.1% only. Percentage positivity of samples ranged from 17.34% in month of August to 44.70% in December which is much higher in comparison to other countries with high population density like Mexico which reported 13% positivity in their samples.(1)

Percentage of H1N1+ requiring hospitalization was 2.13% which was similar to worldwide trends (2-5%).(2) In all, 213 H1N1+ patients were admitted in isolation ward, out of which 52 developed severe lung injury and were thus shifted to swine flu intensive care unit (ICU). Percentage of pediatric patients admitted in isolation ward was maximum (61%) in month of June. None of them required critical care services and no mortality was reported. Comorbidities were present in 39% of patients in ICU with diabetes, hypertension, chronic obstructive pulmonary disease, and tuberculosis in decreasing order of frequency.

Clinical characteristics of H1N1+ patients are compared with those who tested negative for H1N1 admitted in ICU with acute lung injury during the swine flu pandemic [Table 1]. Modes of ventilation used in H1N1+ were as follows: Pressure controlled ventilation (PCV, 30%), synchronized intermittent mandatory ventilation-pressure controlled; SIMV-PC (30%); synchronized intermittent mandatory ventilation-volume controlled; SIMV-VC (20%), volume controlled ventilation; VCV (18%), pressure controlled ventilation-volume guaranteed; and PCV-VG (2%). Recruitment maneuvers, prone positioning, and advanced ventilatory techniques such as high frequency oscillatory ventilation and rescue therapy such as extra corporeal membrane oxygenation were not used. Maximum PEEP of 20 cm H2O, tidal volume upto 4 ml/kg, respiratory rate upto 30 breaths/minute, and inverse ratio ventilation (I: E = 1:1) were used. Plateau pressure more than 35 cm H2O was present in all those who died. Median value of worst compliance was 15 ml/cm H2O (4–22). Muscle relaxants were administered to all patients and infusion of midazolam and fentanyl were used to maintain deep sedation (Ramsay sedation scale 5).

Table 1

Characteristics of H1N1+ and H1N1– patients in ICU

Alternate day sampling of respiratory secretions for RT-PCR was done in 32 patients, but conversion from H1N1 positive to negative status was documented in 12 patients only. Median time for conversion was 5 days with range of 3–18 days.

Overall mortality of H1N1-positive patients in our center was 5% which is higher than that reported from world over (0.3%–0.4%).(2) Mortality of patients with acute lung injury was 86.9% in comparison to reports from critical care units in Mexico,(1) Michigan,(2) Australia and New Zealand,(3) and Canada(4) with 41%, 30%, 21%, and 17% mortality, respectively. Causes of death were refractory shock, acidosis, and acute renal failure [Figure 1]. Multiorgan dysfunction syndrome was present in 20%, and incidence of ARF was significantly higher in H1N1+ patients in comparison to H1N1– patients. Survival of 84% at end of 28 days has been reported in patients admitted with H1N1 infection in a corporate ICU in Bangalore.(5) Favorable factors present in their study population were better lung compliance, single organ failure, low mean APACHE II score, use of prone position and high frequency oscillation for cases with refractory hypoxia. Obesity was commonest risk factor in their study.

Figure 1

Causes of death

Most of the patients admitted in our ICU belonged to low socioeconomic status and were malnourished. Four-fifth of our patients were referred which led to delay in diagnosis and management. Further studies are needed to assess the impact of nutritional status, serum albumin levels, and immunity on outcome from viral infections such as H1N1.