The online publication of three papers and a commentary yesterday in the Journal of the American Medical Association (JAMA; free access, links at bottom of post) provides some further data on what demand for critical care resources might be from the current swine flu pandemic. One paper reports on the Mexican experience, where mortality seemed unusually high but where access to services may have made the outcome worse. The papers from Canada are perhaps most pertinent to what might be experienced in the US and Europe. It appears that in terms of demand for ICU beds, the first wave from last spring and summer may have been less demanding than the first reports out of the southern hemisphere during its now concluding flu season.
We posted on the details of the southern hemisphere paper a few days ago. There, admission to an adult or pediatric Intensive Care Unit (ICU) was estimated to be about 25 to 30 admissions per million population (based on a complete census of ICU beds in Australia and New Zealand over a 3 month flu season period). It is more difficult to interpret the Canadian data as it does not cover all ICU beds in the country, but if we use all 215 confirmed, probable and suspect cases for the 38 reporting ICUs (the characteristics of patients in the paper only include the 168 confirmed and suspected cases) and use the figure in the paper that there were a total of 278 admitted to ICUs in the country with a 2009 population of 34 million, this represents about 8 ICU admissions per million population. Assuming similar age structures for these three developed countries, the Canadian population demand for ICU admission is about a third of the southern hemisphere figure. This could well be because the Australia/New Zealand data were from the usual influenza season while the Canadian data were from a prodromal or herald wave that occurred outside of flu season. I expect we’ll find out soon enough. It is worthwhile noting, however, that even with triple the demand for influenza-related ICU admissions, the two southern hemisphere countries were able to cope by making adjustments in schedules and practices.
The comparison just made is imperfect, at best. It doesn’t take account of the uneven distribution of demand, temporally and geographically, that is typical of influenza in general, and pandemics in particular. It doesn’t differentiate the adult and pediatric distribution nor the varying availability of skilled nursing and medical care. It is clear in the Canadian indigenous First Nations population there was greatly increased risk, and these are also the populations with the least timely, least well-staffed and least accessible critical care beds. National averages don’t tell the whole story. But the small part of the story they do tell suggests that the infrastructure to handle this pandemic exists in both Canada and the US and what is needed is planning to use it most efficiently.
Once again, the most striking features from these papers is the epidemiology:
Patients tended to be relatively healthy adolescents and young adults who developed a brief prodromal illness followed by rapidly progressive respiratory failure. Shock and multisystem organ failure were common. Hypoxemia was prolonged and severe, requiring on average 12 days of mechanical ventilation and frequent use of rescue therapies such as high-frequency oscillatory ventilation, prone positioning, neuromuscular blockade, and inhaled nitric oxide. The influenza outbreak lasted about 3 months in both countries, but the peak lasted just a few weeks, during which time hospitals struggled to accommodate the increased patient load, with 4 Mexican patients dying while awaiting ICU beds. (White and Angus, Comment in JAMA)
So these were young patients with rapidly deteriorating and catastrophic illness, unexpected in this age group. Stark differences in mortality between the Mexican and Canadian series (41% versus 17% of ICU cases) might be due to a number of differences. Many more Canadian patients were treated with antivirals than in Mexico, there was greater delay and less access to ICU beds in Mexico and the level of skilled care may have been less. In an accompanying Editorial, White and Angus put a positive but cautionary spin on the 17% mortality:
The large proportion of critically ill patients with H1N1 who survived is an important reminder that the medical response to a respiratory pandemic is very different today than it was for the 1918 influenza pandemic. The widespread availability of antibiotics, antiviral agents, vasopressors, and mechanical ventilation makes it possible to save many patients who would not have survived in 1918. With this potential comes an obligation for hospitals and public health systems to collaboratively develop strategies to ensure that, if there is a resurgence of 2009 influenza A(H1N1), the benefits of intensive care medicine can be offered to the maximum number of patients. Although guidelines and recommendations exist for augmenting hospital surge capacity, their implementation in individual hospitals is far from complete. The investigators from both Mexico and Canada noted that the health care systems struggled to meet the demands created by the increased patient volume, a sobering observation given that the absolute number of excess ICU admissions was modest. (White and Angus, Comment in JAMA)
Without denying the essential truth of this — that modern medicine can save some people who in earlier times couldn’t be saved — the fact is that with the best of critical care medicine at their disposal, 1 in 7 people in the prime of life still died. There is a mistaken impression that 1918 couldn’t happen again because “now we have antibiotics.” Even if 1918 is less likely to happen to the population, it could still happen to you. And we have no way to predict if you will be one of the chosen ones.
As White and Angus note and which our back-of-the-envelope calculations confirm, the added burden on resources from swine flu during this period was quite modest, even compared with the southern hemisphere. Yet it stressed some ICUs and their staffs to the limit. It’s possible, especially in the US, to make scheduling adjustments that will ease the burden but planning for this has to happen immediately. We are well into a swine flu season already. It is worth repeating one of their observations, quoted above:
Although guidelines and recommendations exist for augmenting hospital surge capacity, their implementation in individual hospitals is far from complete.
Said another way, too many hospitals have prepared by paying lip service to pandemic planning. It’s time to take it seriously. Very, very seriously. Lives hang in the balance.
Links to the JAMA Free Access papers:
Critically Ill Patients With 2009 Influenza A(H1N1) in Mexico
Guillermo Domínguez-Cherit, Stephen E. Lapinsky, Alejandro E. Macias, Ruxandra Pinto, Lourdes Espinosa-Perez, Alethse de la Torre, Manuel Poblano-Morales, Jose A. Baltazar-Torres, Edgar Bautista, Abril Martinez, Marco A. Martinez, Eduardo Rivero, Rafael Valdez, Guillermo Ruiz-Palacios, Martín Hernández, Thomas E. Stewart, and Robert A. Fowler
ABSTRACT | FULL TEXT
Critically Ill Patients With 2009 Influenza A(H1N1) Infection in Canada
Anand Kumar, Ryan Zarychanski, Ruxandra Pinto, Deborah J. Cook, John Marshall, Jacques Lacroix, Tom Stelfox, Sean Bagshaw, Karen Choong, Francois Lamontagne, Alexis F. Turgeon, Stephen Lapinsky, Stéphane P. Ahern, Orla Smith, Faisal Siddiqui, Philippe Jouvet, Kosar Khwaja, Lauralyn McIntyre, Kusum Menon, Jamie Hutchison, David Hornstein, Ari Joffe, Francois Lauzier, Jeffrey Singh, Tim Karachi, Kim Wiebe, Kendiss Olafson, Clare Ramsey, Satendra Sharma, Peter Dodek, Maureen Meade, Richard Hall, Robert Fowler, and for the Canadian Critical Care Trials Group H1N1 Collaborative
ABSTRACT | FULL TEXT
Extracorporeal Membrane Oxygenation for 2009 Influenza A(H1N1) Acute Respiratory Distress Syndrome
The Australia and New Zealand Extracorporeal Membrane Oxygenation (ANZ ECMO) Influenza Investigators
ABSTRACT | FULL TEXT