Effect Measure

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
JAMA. 2009;0(2009):20091536-8.
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
JAMA. 2009;0(2009):20091496-8.
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
JAMA. 2009;0(2009):20091535-8.
ABSTRACT | FULL TEXT

Comments

  1. #1 Don S
    October 13, 2009

    It must be noted that while this Canadian experience was only the herald wave, with only 1/3 of the ICU admits as were in Australia/NZ, they maxxed out their ICU capacity at points in some locations and at points 50% of ICU beds in some areas were filled with H1N1 patients.

    These patients stayed longer in the ICU than in Australia/NZ as well, which may have been part of it.

    I hope that hospital administrators start planning a bit more seriously. So far those of us in the trenches have not gotten the sense that they have.

    Is the meme still going to be that H1N1 is not so bad per case when the herald wave is causing this kind of disease and Australia/NZ with reports of not much more influenza than usual had 15x more ICU admits 20% of whom died?

  2. #2 novaccine4me
    October 13, 2009

    A friend’s son was recently in the hospital in DC with appendicitis, and asked the nurse how many cases of swine flu they had, and was shocked to hear “none.” Over the next several days she asked the different nurses and each confirmed there had been none. We have heard repeatedly the past months about the raging epidemic and that it is more seriously affecting children. On her son’s last day at the hospital, the nurse seemed in a hurry to get them out of the room, and when asked why, the nurse said there were a lot of very sick children. When asked what they were sick with, the nurse replied “asthma.”
    Two studies that were never written about in any major newspaper in the US, but which are very significant. One, “Childhood asthma is reduced by half when the first dose of diphtheria, pertussis, and tetanus (DPT) is delayed by more than 2 months vs given during the recommended period, according to the results of a retrospective longitudinal study reported in the March issue of the Journal of Allergy & Clinical Immunology.” Second, from “ScienceDaily: Children Who Get Flu Vaccine Have Three Times Risk Of Hospitalization For Flu, Study Suggests.” Reporters, let this be a call to you to end propaganda campaigns and report all the facts. Both studies paint a clear picture about the relationship between vaccination and chronic illness, and many other studies can be easily found with a few strokes of a keyboard.

    According to the Asthma and Allergy Foundation of America:
    * Asthma accounts for one-quarter of all emergency room visits in the U.S. each year, with 2 million emergency room visits. [7] (This epidemic dwarfs the swine flu epidemic)
    * Each year, asthma accounts for more than 10 million outpatient visits and 500,000 hospitalizations. [8]
    * The average length of stay (LOS) for asthma hospitalizations is 3 days. [9]
    * Nearly half (44%) of all asthma hospitalizations are for children. [10]
    * Asthma is the third-ranking cause of hospitalization children. [11]
    * Each day 11 Americans die from asthma. There are more than 4,000 deaths due to asthma each year.In addition, asthma is indicated as “contributing factor” for nearly 7,000 other deaths each year. [14]
    * Since 1980 asthma death rates overall have increased more than 50% among all genders, age groups and ethnic groups. The death rate for children under 19 years old has increased by nearly 80% percent since 1980. [15] (22 doses of childhood vaccines recommended from birth to age 6 in 1983 – 48 doses of childhood vaccines by the age of 6 recommended in 2009 – not including swine flu vaccine)
    There is no action without an equal and opposite reaction. In the effort to prevent all experience with infectious disease, children are becoming immunologically and neurologically poisoned and have developed high rates of chronic illness and disability.

  3. #3 EM tech
    October 13, 2009

    novax4me: While I’m sure we all only have our children’s best in mind, we must also be very careful not to read too much into a single blurb. Kids who get flu vaccines also have parents who provide insurance and availability as well as a proactive health stance. They are also more likely to have a higher risk category to need a flu vaccine, since kids who have asthma are already being treated for a known complicating disease. Therefore, kids who have greater access also are more likely to use it. Like so many things, it’s more complex than it appears.

    I’m sure others have far more in depth thoughts on this!

  4. #4 Paula
    October 13, 2009

    An important post, Revere, and I agree with Don S. that there’s a serious problem with hospital administrators (and some states public health administrators) who aren’t taking this planning seriously or with urgency. So—what do we do in such cases? Suggestions would be appreciated.

  5. #5 Ron Law
    October 13, 2009

    Don, the 15x increase in ICU admissions is a myth… totally false. The NZ paper in the NEJM said there had been an average of 57 patients with vital pneumonitis in previous years. This group, plus ARDS patients made up 48% of the Aus.NZ admissin cases, yet 15×57 = 855… more than the total number admitted.

    I emailed the authors for a breakdown on viral pneumonitis and ARDS patients… the response was that they didn’t have that data… so the paper compared apples with oranges, made an error re 15x and then the media took that 15x and applied it to all admissions to ICU.

    Think about it… if there was an increase of 15x and the ICUs didn’t reach capacity then they but have only been 6-7% full to start with.

  6. #6 revere
    October 13, 2009

    Ron: I’m not sure I understand your reasoning. “Viral pneumonitis” was used as a surrogate for an admission to the ICU for flu in previous years because they didn’t have flu specific info. Thus it is an overestimate. It would include ARDS from viral pneumonitis as well, but not ARDS from other causes (which might be related to flu, e.g., bacterial pneumonia, but we are in the same ballpark). That means that the actual numbers for flu admissions were probably even smaller in previous years. This year’s figures are more accurate and include only flu admissions. Since admissions to ICUs for flu are only a small percent of the total, then an ICU can cope with a 15x increase spread out over 3 months. And they did. Remember, 48% of the flu admissions is not 48% of ICU admissions.

  7. #7 Don S
    October 13, 2009

    novaccine4me,

    From your name it sounds like your mind is pretty well made up about vaccines no mater what anyone says, but your post does deserve a response.

    Beware selection bias.

    In this case two types of selection bias are present:

    1) The selection of studies that show the result you prefer and ignoring the other studies that show other results. Multiple studies have been done – many have shown no such association and a few have shown one. It has not been a clearly replicable finding and even the study regarding the DTP and asthma that you quote had the finding just barely outside a 95% confidence interval. You really need to look at the totality of the data and not just the study which has results you “knew” ahead of time. See http://www.ncbi.nlm.nih.gov/pubmed/19532091?ordinalpos=6&itool=EntrezSystem2.PEntrez.Pubmed.Pubmed_ResultsPanel.Pubmed_DefaultReportPanel.Pubmed_RVDocSum for a review of the totality of them: “… a causal relationship is not supported by the majority of observational studies. … Current evidence suggests that virus vaccination is well tolerated and does not lead to an increased incidence of asthma or atopy in children receiving vaccines…”

    2) The selection bias in the studies themselves. The kids who tend to be vaccinated for influenza tend to be the kids at high risk for serious influenza complications. Kids at many fold higher risk for asthma complications are going to have more asthma complications than low risk individuals even with vaccination, even if their own risk is substantially reduced. The issue is not whether or not vaccination reduces their hospitalization rate to lower than low risk children, but if it reduces it to lower than a similarly high risk individual who was not vaccinated.

    Ron, I am similarly confused by your confusion.

  8. #8 MoM
    October 15, 2009

    Late to the party… again. Any comment on the Southern Hemisphere paper’s discussion of ECMO for patients with severe respiratory distress? I didn’t see it in the linked post, either.

  9. #9 revere
    October 15, 2009

    MoM: No, I didn’t comment on ECMO. I don’t know that much about it and it requires a perfusionist and by-pass, an even more intensive use of critical care facilities. So it’s on the margin of my public health interests because it represents specialized and new theapy.

  10. #10 Paula
    October 15, 2009

    Still hoping for comments on how to wake up unprepared hospitals. Local hospital chain’s response to public concern re its ventilator etc. surge capacities was to announce today some limitations on visitors and to rule that “some visitors [with possible flu symptoms] may be asked to wear surgical masks.” Yeah.

  11. #11 Phillip Huggan
    October 17, 2009

    Looking for any canada thread to hijack…
    Here we have a large city that is Seattle climate, Vancouver, and the rest of the land gets real winter to varying degrees with flu-friendly low humidity mostly. Surprised to see a news headline today that Vancouver is having heavy Swine Flu. I’d’ve suspected the opposite. Thinking about it now, maybe during the Spring Vancouver was the highest humidity and probably warmest…so people weren’t cooped up and breathing dry air last spring and thus least likely to be exposed, are least likely to be immune now whereas rest of Canada got sicker in Spring and is now more immune?

    I would think think it would be possible to begin ramping up ventilator manufacturing in late April, akin to a war time economy. But it’s probably useless without the custom hospital rooms, no? If you guys had Universal Healthcare your rich right could be lobbying for the ability to buy flu ventilator insurance that would be too expensive to cover under universal. Nope, give $ to lawyers and lobbiers instead.

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