NurseWeek: Generation Rx: As demographics change, the patient of 2010 will pose new challenges

High on the hog
Nurse researcher uses pigs to try to unlock common ICU problem
By José Alaniz
August 7, 2000

Sandra Hanneman's research focuses on weaning patients from mechanical ventilation machines using pigs.

Photo: University of Texas-Houston School of Nursing


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Most nurses can recall difficult, even obnoxious patients they’ve dealt with – but the ones Sandra Hanneman , Ph.D., RN, FAAN, had to take care of every day in her ICU were absolute pigs.

Sus domesticus, to be precise, the sort of farm-raised 150- to 200-pound porker generally consumed as ham or bacon on breakfast tables. But these animals, which usually spend most of their lives eating and rooting on a farm in Bastrop wound up at the University of Texas-Houston Health Science Center School of Nursing as human research subjects: sedated, hooked up to ventilator machines, IVs and monitors, and sprawled on their backs on regular ICU beds.

They even had names: Mikey, Opus, Claude Jean and Juan Gabriel (six other pigs were studied, but did not get the ICU treatment). But the cute monikers shouldn’t be taken as a sign of sentimental attachment, said Hanneman, associate dean for research and evaluation and associate professor of acute and continuing care.

"I don’t like pigs, I don’t like working with them. I’m a city girl," Hanneman, 52, admitted. "I don’t like the smell. But in many ways they’re the closest thing to people that we can get for this project. And we do acknowledge each pig’s individual personality; we pay as much close attention to them as we would to human ICU patients."

The meticulous monitoring and care, Hanneman said, may eventually unlock a mystery she has been investigating as a scholar since 1990, but has wondered about since her days as an ICU nurse: Why does one out of five ICU patients on a mechanical ventilator experience trouble being weaned from it, despite no medical signs of a problem?

"We’ve made no progress in 25 years in predicting who will have trouble coming off the ventilating machine, even though lots of people have been researching this area," she said. "It seemed clear to me in reading the broader literature that we were missing some basic phenomenon."

Hanneman theorizes that the common model of medical care, based on homeostasis – the concept that bodily functions seek to maintain a constant, steady state throughout the day and night – has blinded caregivers to the body’s natural rhythms, which vary and play an important role in determining the effectiveness of a given therapy or drug.

Chronobiology, more widely known as the study of "biorhythms," emphasizes the body’s "peaks and troughs" during a roughly 24-hour cycle and might aid ICU workers in identifying windows of opportunity to start weaning patients off ventilators or administering drugs for maximum effect, Hanneman said.

"Circadian rhythms are the most well-known of the body’s variables, but depending on the time of day, hormones also get secreted, blood pressure goes up and down, body temperature changes, and this is all affected by seasonal changes, the weather, the earth’s rotation,"she said. "If we can individualize our care to the point that we understand a particular person’s peaks and troughs, we may be able to predict with much better accuracy the optimal time to administer a therapy."

But although most physicians accept the basic premise of a biological clock, Hanneman said, the medical community has been slow to apply its broader implications, preferring the homeostasis model – despite its drawbacks. Her study may help change such thinking, but not before she and her team go through reams of data reflecting more than 35 cardiopulmonary and metabolic variables for each pig.

"We’re still working out techniques to measure and glean all this information, and reconciling it with journals we kept on the subjects. This is a very expensive study, about $35,000 per pig. We need to gather lots of data and then find ways to extract the intrinsic from the extrinsic information and establish the biological patterns accurately,"she said.

"I’m not entirely convinced myself, but if this chronobiology theory holds water, it could significantly change the way we handle ICU patients. We would be more interested in finding patients’ marker rhythms as soon as they came in and identifying windows of adaptation. We may find that we were taking some patients off ventilators at the wrong time of day; the homeostatic indicators were right, but we caught them at a trough of some kind, and so they crashed.

"Instead of giving patients a steady drip all day long, we may need to vary the amount of medicine depending on the time of day or their blood pressure. Maybe we’ll discover that we shouldn’t feed intravenously at all, but turn to more episodic approaches. The changes in care could be comprehensive."

They already have been – for the pigs.