War Against H1N1 Likely to Be Fought in Intensive Care Units

Pediatric Critical Care Columnist · Sep 1, 2009

Our medical director was saying just today that our unit is going to be hammered by H1N1. He used the words "overwhelmed" and "inundated". Then he said, "But we'll manage." I asked him if he was furiously knitting nurses in his spare time and he looked at me like I was from Mars. But the fact is, we're short about 15 full-time equivalents and are staffing our unit with OT already. What will we do when we have a full house and have expanded across the hall into the vacant old 8 bed CVICU that moved into a new building six weeks ago? That's in effect 150% capacity, with only about 80% staffing. It's going to be a disaster.

My friends in Winnipeg have only just started recovering after their crazy spring and early summer. They're not anxious to return to the mandatory OT and CO2 narcosis of the N95 mask. BUT... they'll send their sickest patients to us because we do ECMO and they don't. Yippee.

oramar · Sep 1, 2009

Like I have been saying all along, add this to the fact that many healthcare institutions in the US have been cutting staff all summer and you got a problem.

indigo girl · Sep 1, 2009

http://scienceblogs.com/effectmeasure/2009/09/how_the_flu_pandemic_looks_to.php

Excerpt from Effect Measure post commenting on the latest WHO assessement of the pandemic:

The difference between seasonal flu and swine flu is primarily one of epidemiology, that is, the pattern and distribution of the disease in the population. Younger age groups are affected (and older ones not affected), and the increased infections in the young are producing increased severe and fatal infections. By most accounts we've seen, the virus doesn't seem more virulent than seasonal flu virus. Seasonal flu always kills a certain proportion of its victims, usually in the oldest age groups.

The Editors of Effect Measure are senior public health scientists and practitioners. Paul Revere was a member of the first local Board of Health in the United States (Boston, 1799). The Editors sign their posts "Revere" to recognize the public service of a professional forerunner better known for other things.

oramar · Sep 1, 2009

http://scienceblogs.com/effectmeasure/2009/09/how_the_flu_pandemic_looks_to.php
Excerpt from Effect Measure post commenting on the latest WHO assessement of the pandemic:
The Editors of Effect Measure are senior public health scientists and practitioners. Paul Revere was a member of the first local Board of Health in the United States (Boston, 1799). The Editors sign their posts "Revere" to recognize the public service of a professional forerunner better known for other things.

Another excellent article. People were spreading those false rumors about "pulling the plug on grandma" in August. What is happening here is that grandma will have to make it without being plugged in or maybe not make it at all. All resources will be allocated to the young. What are you going to do, put the 76 year old on the only vent or the 30 year old mother of four. The choices are going to be extremely harsh. The only thing that might help is that the severest outbreaks may be regional. So that perhaps resources can be moved from one place to another. If all major cities are hit at same time with roughly same severity it won't be pretty. As one ICU nurse here said, "we will be dealing with 150% capacity with staffing at 80%". When it is winding done and the blame game starts perhaps the people picking the situation apart to see what went wrong can come here and read how it was all predicted by nurses.

Katnip, RN · Sep 1, 2009

Not only will the staffing be at 80%. If the staff can't or won't be vaccinated, you can count on the staffing to be less than 80% because a percentage of them will be sick at any given time.

I really, really feel for all the ICU nurses out there. It's going to be really tough. I'm starting back into the ER at the end of this month, and as bad as that will be, I think ICUs are going to get it much worse. Bless you all.

Pediatric Critical Care Columnist · Sep 1, 2009

Not only are we running at 80% of staffing on our unit, but as I mentioned on another thread, our catchment area is roughly 1.26 million square kilometers or about 783,000 square miles. In Canada our aboriginal population has been more severely affected in some provinces, including the ones my unit is responsible for when it comes to ECMO support. So far we haven't had any H1N1 patients requiring ECMO but I fear it's only a matter of time.

While I was eavesdropping yesterday I heard our medical director also discussing the issue of our air ambulance pilots refusing to transport H1N1 patients out of concern that they can't adequately protect themselves from it in the air. There's a meeting tomorrow to discuss the issue with their union and the public health people to see if some sort of arrangement can be ironed out.

The Mountains Voice · Sep 6, 2009

war against h1n1 likely to be fought in intensive care units

[color=#818181]the canadian press
[color=#818181]mon. aug 31 - 11:45 am
toronto — intensive care specialists who fought to save desperately sick swine flu patients this spring and summer have a warning for hospitals that haven't yet dealt with an influx of these difficult-to-treat patients. prepare. now.

http://thechronicleherald.ca/front/9013059.html

Editorial Team / Admin · Sep 6, 2009

Threads merged.

MedSurgeMess · Sep 7, 2009

Not only will the staffing be at 80%. If the staff can't or won't be vaccinated, you can count on the staffing to be less than 80% because a percentage of them will be sick at any given time.
I really, really feel for all the ICU nurses out there. It's going to be really tough. I'm starting back into the ER at the end of this month, and as bad as that will be, I think ICUs are going to get it much worse. Bless you all.

Right now I have elderly patients who tell me that they deserve the vaccine more than any health care worker, because of all the sacrifices that they have made in the past. I just ask them who will take care of them when all of the healthcare workers are sick d/t lack of access to vaccines......Oh well, all of these new grads can step in and take the jobs, with no training on top of that!

indigo girl · Sep 9, 2009

The Depressing Math of Swine Flu, ICU's and Ventilators

http://scienceblogs.com/effectmeasure/2009/09/the_depressing_math_of_swine_f.php#more

One of the most feared outcomes of infection with influenza is Acute Respiratory Distress Syndrome (ARDS; in less severe form it may be called Acute Lung Injury, ALI). For reasons we still do not understand, cells deep in the lung that are involved in gas exchange (oxygen and carbon dioxide) become so damaged that the basic work of supplying the body with enough oxygen for life and getting rid of the carbon dioxide generated by metabolism is too much for the patient and either some intervention to relieve the lungs of some of the work is made or the patient dies. ARDS is so severe that often no intervention works, and fatality ratios of 50% are quite typical. The most common intervention is a mechanical device called a ventilator to do some of the work of breathing for the patient. Critical care respiratory therapy is much more than pumping air in and out of the lungs, however. It is a very complex and tricky art, and it is now believed by many that conventional mechanical ventilation can make ARDS worse and decrease the odds of survival. The literature on ventilation in ARDS is highly technical, and advanced methods using sophisticated computer-controlled devices are often needed.
Both the devices and the expertise to use them in ARDS are in short supply and will be a significant bottleneck if the flu pandemic is severe this fall. Even trying to figure out how serious the situation might be is fraught with difficulty, as a recent paper in PLoS Currents/Influenza demonstrates. It was an attempt to figure out how much stress will be put on Intensive Care Unit capacity given reasonable assumptions about how swine flu might evolve. The method used to make the estimate is easy to understand because it is is so simplistic, but even so, illustrates the difficulties.
The short paper, more of a back-of-the-envelope calculation, was done by researchers from a consulting group and hospitals in California and Washington DC (Swine origin influenza A (H1N1) virus and ICU capacity in the US: Are we prepared?, Zilberberg et al., PLoS Currents/Influenza). Here's what they did. They start with the population of the United States, which they give as 307,024,641 (NB: all their estimates are expressed with the same degree of meaningless excess of significant figures, so I am going to round their numbers for clarity; for example, in this case I'd just will say 300 million). They then assume that the attack rate (per cent of the population infected) will be 15%, but allow it might be as low as 6% or as high as 24%. Thus they are acknowledging uncertainty around the 15% number, which they will use in a way I'll describe shortly. These figures were taken from numbers given at a CDC press briefing on August 24, so they represent CDC's estimates at that time of the pandemic. Once flu season starts in earnest, attack rates of 30% may be more likely, but for this paper 15% was used. That attack rate represents about 46 million flu cases, but with the uncertainty included, they come up with numbers between 37 and 55 million. You can think of this as a confidence interval around the 46 million point estimate. How did they get these numbers?
They used something called a Monte Carlo simulation and it works like this. The 46 million number is easy to see. It's 15% of 300 some odd million. If you were using an Excel spreadsheet (which is what they used), you would enter the US population in one cell, the attack rate in another cell and then have a formula that multiplied the two together in a third cell. The problem with this is that while the population of the US is a fairly stable number, the 15% attack rate is a guess. There might be quite a lot of plausible attack rates, of which you judge that 15% is the most likely but many others possible. Think of a bell-shaped curve with 15% in the middle and many values higher and many lower. This bell curve can be very spread out or very sharp and peaked, depending on how sure you were about the 15%. What the authors did is construct a bell curve that used the two other figures expressing the uncertainty (the 6% and the 24%) in terms of its spread. Imagine, now, a gigantic pile of tokens with attack rates written on them (many will have 15% written on them, somewhat fewer that say 14% or 16%, and even fewer that a percent or two of numbers that are less than 6% or higher than 24%). Now instead of putting 15% into your spreadsheet cell, you reach into this gigantic pile of tokens and pull one out and put its value in the cell instead. Maybe it's 19% or 11% or 15% (since there are more 15% tokens than anything else, but depending on the spread of the bell, there still may not be that many). Now let the spreadsheet calculate the number of cases (the token-drevied attack rate times the population). That will give you a number of infected cases. Now put the token back in the pile and do it again. And again. And again. The authors did just that ten thousand times, although of course they used a computer and an add-on to Excel called Crystal Ball which allows you to stipulate various kinds of statistical distributions for your token pile. Theirs was bell shaped, as described. When you do this you get another bell shaped curve representing the range of infectives, complete with the peak value (the center of the distribution) and the 95% confidence interval (in this case the part of the bell with 95% of the stuff under it).
Now you can do the same thing for the rest of the calculation. Let's go back to the single calculation. You've got the number of infected cases in the cell with the formula (population times attack rate) and you multiply that by the proportion of cases you expect to be hospitalized. They used data from California for swine flu H1N1 which was estimated at that point to be 6% with a low of 2% (assumed) and a high of 10% (from the early Mexico data). Some of those hospitalized will be so sick that they wind up in the ICU on ventilators (12% from Mexican data, low and high guesses of 6% and 18%), and of those, again using Mexican data, 58% end fatally (low and high guesses of 40 and 60%). Now they do the random selection in each of these cells simultaneously 10,000 times, and that's how the joint confidence intervals are figured. Here are the results (rounded estimates and 95% confidence intervals):
US pop: 300 million
Cases: 46 million (37 - 55 million)
Hospitlizations: 2.8 million (2 - 3.6 million)
On ventilators: 132,000 (228,000 - 454,000)
Deaths: 192,000 (126,000 - 226,000)
This corresponds to an overall case fatality ratio (CFR) of out 0.5%, comparable to the early estimates from Mexico. Since some of the most important data is from those early weeks, this isn't surprising. But since there has been a lot of questioning of the applicability and accuracy of the Mexican CFR to the US setting. In a paper published in Eurosurveillance, a group from New Zealand used numbers from later in the pandemic and a variety of different CFR estimation methods and came up with dramatically lower numbers (0.06% to 0.0004%). Using a 30% infection rate (twice what the ICU paper used) still resulted in dramatically lower numbers for deaths. Instead of the roughly 400,000 deaths the US would expect under the ICU paper assumption (taking account of a 30% infection rate), the estimates from the Eurosurveillance paper would run from 3600 deaths to 54,000 deaths (there were no ventilator estimates).
Thus we have point estimates for the US that go from 3600 to 400,000 deaths, with some in between. The 3600 deaths estimate (a CFR of 0.0004%) seems wildly low, given that swine flu seems much like seasonal flu in virulence. Even the 0.06% figure (54,000 deaths) seems low, given the usual seasonal flu estimate is 0.1%. But in every case where assumptions have been made, they seem plausible, even if markedly divergent. Unfortunately the differences are of great significance. The ICU figures may be too high because of the use of Mexican estimates that were biased upward, but they only used a 15% attack rate which is likely too low. And the cases will not be coming into hospitals uniformly but in huge clumps or bunches. No hospital has a reserve of expensive mechanical ventilation equipment.
One can easily see that the scenario depicted by Helen Branswell in her piece, "War against H1N1 likely to be fought in intensive care units" is likely right on target. Given the numbers, it's hard to see how we can win that war.

indigo girl · Sep 9, 2009

Swine origin influenza A (H1N1) virus and ICU capacity in the US: Are we prepared?

See this research note at PLoS Currents: Influenza.
We developed a model simulating the potential impact of influenza H1N1 pandemic on the volume of acute respiratory failure requiring mechanical ventilation (ARF-MV) and the accompanying mortality rate in the US. We calculate that 46 million people will contract the infection, resulting in 2.7 million hospitalizations, 331,587 episodes of ARF-MV and nearly 200,000 deaths, suggesting that the US may require the ability to provide MV at a volume approximately 33% over the current annual use.
INTRODUCTION
In March of 2009 a novel strain of swine origin influenza A (H1N1) virus (S-OIV) was detected in Mexico. It has now spread to the rest of the world. With over 170,000 laboratory-confirmed cases worldwide, the World Health Organization (WHO) has declared a global pandemic[1]. In the United States, current estimates suggest an attack rate of approximately 6-8% in affected communities, which according to officials from the Centers for Disease Control and Prevention (CDC) may more than double during the traditional flu season[2]. Although reports of both severe illness and fatalities are uncommon, concern exists about the potential for this virus to cause severe acute respiratory failure necessitating mechanical ventilation (ARF-MV) with specialized methods[3]. Since H1N1 is predicted to affect a significant proportion of the population, even a low incidence of concomitant ARF-MV may overwhelm the already-stretched emergency department and intensive care unit (ICU) resources[4]. To estimate what the S-OIV may portend for the ARF-MV in the US, we developed a model simulating its potential impact on the volume of ARF-MV and the accompanying mortality rate.

More at: url]http://www.ncbi.nlm.nih.gov/rrn/articlerender.fcgi?acc=RRN1009[/url]

(hat tip pfi/helblindi)