Mexico: 41% Mortality Rate for H1N1 Critically Ill
By Michele G. Sullivan
Elsevier Global Medical News
Critical illness occurred in 6.5% of patients with pandemic A (H1N1) influenza who were admitted to hospitals in Mexico from March-June, with 41% of those patients dying from the infection, a retrospective review has confirmed.
Compared with survivors, those who died had higher measures of acute illness severity and organ failure at hospital admission, as well as lower mean arterial pressure, lower oxygenation measures, and higher creatine kinase, Dr. Guillermo Dominguez-Cherit and his colleagues reported in a study published online in JAMA and presented simultaneously at the annual meeting of the European Society of Intensive Care Medicine.
"Importantly, we found in this cohort that either SOFA [Sequential Organ Failure Assessment] or APACHE [Acute Physiology and Chronic Health Evaluation] II scores may help to identify patients at high risk of death," wrote Dr. Dominguez-Cherit of the Instituto Nacional de Ciencias Medicas y Nutricion "Salvador Zubiran," Mexico City.
Some researchers have suggested using SOFA scores for triage purposes during pandemics, because they are easy to calculate, the investigators added.
"From the Mexico experience, it is clear that in certain environments, critical illness from 2009 influenza A(H1N1) may be associated with severe acute lung injury, refractory hypoxia, and a high mortality rate in young individuals," they wrote. "Early recognition of disease by the consistent symptoms of fever and respiratory illness during times of outbreak, with prompt medical attention including neuraminidase inhibitors and aggressive support of oxygenation failure and subsequent organ dysfunction, may provide opportunities to mitigate the progression of illness and mortality observed in Mexico."
The study reviewed outcomes for 58 patients who were critically ill with confirmed, probable, or suspected pandemic flu and admitted to any of six regional medical centers in Mexico from March 24 through June 1. In all, 899 patients were admitted to these facilities for pandemic flu during the study period; the 58 with critical illness represented 6.5% of the cohort. Overall, these critically ill patients were young (mean age 44 years), but only two were children (10 years and 14 years).
Presenting symptoms included fever (100%), respiratory complaints (98%), weakness (71%), myalgia (60%), headache (57%), and gastrointestinal symptoms (30%). Symptoms developed a mean of 6 days before admission (JAMA 2009; [doi:10.1001/jama.2009.1536]).
The mean APACHE II score at admission was 20, indicating an approximate mortality risk of 40%. Only two patients had a history of chronic obstructive pulmonary disease, but 36% were obese, significantly more than the population background rate of 30%. Obesity, however, was not a predictor of mortality.
A total of 55 of the 58 patients had already received some medical therapy before coming to the hospital: 95% had received antibiotics, 78% neuraminidase inhibitors, 14% amantadine, 2% rimantadine, and 69% corticosteroids. Two had received recombinant activated protein C.
Mechanical ventilation was necessary in 54 patients, including one child. The mean fraction of inspired oxygen on the first day of critical illness was 72%; the mean oxygen saturation was 88%. The mean set positive end-expiratory pressure (PEEP) was 13. Radiographs showed bilateral disease in 96% of the patients, with barotrauma occurring in six over the follow-up period.
After 60 days, 24 of the 58 patients had died (41%). Most (19) died within the first 2 weeks of becoming critically ill. Both children survived.
All deaths within the first 28 days were related to respiratory failure. One late death was related primarily to multisystem organ dysfunction.
Patients who died had significantly worse measures of acute illness than did survivors upon admission (mean APACHE II 28 vs. 14; mean SOFA 12 vs. 7). They also had lower mean arterial pressure at admission (63 vs. 76 mm Hg); evidence of kidney and liver injury; lower ratio of partial arterial oxygen to FiO2 (70 vs. 120 mm Hg), and higher set PEEP (15 vs. 10 cm H2O). Creatine levels also were significantly higher in those who died (1.4 vs. 0.90 mg/dL).
After the researchers excluded those who died with 72 hours of the onset of symptoms, survivors were seven times more likely to have received treatment with a neuraminidase inhibitor.
Neither Dr. Dominguez-Cherit nor any of his coauthors reported any conflict of interest with regard to the report.