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The Economics of Patient Warming
How preventing hypothermia is more cost-effective than treating it.
Chris Mahoney
Publish Date: October 10, 2007   |  Tags:   Anesthesia

Every year, an estimated 14 million surgical patients suffer unintentional hypothermia - that is, hypothermic conditions that aren't planned, as they are in certain neurological or cardiac procedures - during their perioperative treatment.

Cost Effectiveness of Maintaining Normothermia (per-patient basis)


Cost savings (low end)

Cost savings (high end)

Red blood cells (unit)



Plasma (unit)



Platelets (unit)



Length of stay (day)



ICU time (hour)






Myocardial infarction









Total cost savings



After mortality



Source: Mahoney CB, Odom J. Maintaining intraoperative normothermia: a meta-analysis of outcomes with costs. American Association of Nurse Anesthetists Journal. 1999 Apr;67(2):155-63

Unintentional hypothermia threatens more than just patient comfort. It can result in adverse surgical outcomes and post-operative complications that may end up costing you thousands of dollars per patient in the final analysis. Here's how the cost of treating hypothermia compares to the cost of the patient care that's necessary to prevent it.

Cause and effect
Normothermia, or the body's normal core temperature, is defined as 36'C to 38'C (96.8'F to 100.4'F). In the perioperative setting, there are three major factors that can lower the body's core temperature:

  • exposure of a patient's skin to a cool environment (the most obvious)
  • exposure to cold IV fluids, irrigation fluids or blood products; and
  • use of general anesthesia, which inhibits the body's ability to conserve heat and warm itself.

Studies have shown that if patients become hypothermic, they're more likely to suffer coagulopathy and blood loss and to need more transfusions. Their weakened bodies are more at risk for surgical site infections and less able to heal from them. They may even require increased ventilator use or more time in ICU. The end result? Sicker patients with longer hospital stays.

According to the American Society of PeriAnesthesia Nurses' "Clinical Guideline for the Prevention of Unplanned Perioperative Hypothermia," issued in 2001, "The cost of perioperative hypothermia varies and can range from the cost of an extra cotton blanket to increased patient morbidity and mortality."

Jan Odom, RN, MS, CPAN, FAAN, and I pinned a price tag on hypothermia. In a 1999 study, we calculated that even mildly hypothermic patients, those whose core temperatures had dropped 1.5'C below normothermia, could suffer an increase in adverse outcomes that could add costs of as much as $2,500 to $7,000 per patient.

Prevention vs. Treatment

  • Unintentional hypothermia is said to be among the most common complications of surgery, even though it's easily preventable through proper patient warming.
  • Preventing hypothermia costs significantly less than treating the adverse outcomes of hypothermic patients does.
  • Maintaining normothermia decreases the risk of adverse outcomes and saves time and money for patients, providers and payers.
  • Studies have shown that convective or forced-air warming systems are not only the most commonly used but also the most effective method of warming patients.

We arrived at this widely cited figure through an analysis of the clinical data in 20 studies that covered 1,575 patients. The analysis showed that normothermic patients required fewer transfusions of blood components and had shorter ICU and hospital stays, while hypothermic patients had a greater probability of infection, myocardial infarction, mechanical ventilation and mortality.

To determine the costs resulting from the difference in adverse patient outcomes between the two groups, we first calculated the incidence of each outcome's occurrence: In what percentage of cases would transfusion, infection, lengthened recovery and other outcomes occur? The difference in the probability of occurrence between hypothermic and normothermic patients represents the effect size.

Then we obtained Medicare's reimbursement data for each treatment. Since these numbers are geographically weighted, with urban healthcare facilities, for instance, receiving higher reimbursement rates than their rural counterparts, we selected both high-end and low-end figures.

These unit costs multiplied by the effect size equals the cost savings. Applied to a large population, that's how much money you'd save on average per patient for each particular item (see "Cost Effectiveness of Maintaining Normothermia" on page 56).

The cost of warming
Unintentional hypothermia is said to be among the most common complications of surgery, even though it's easily preventable through proper patient warming. Such prevention also costs significantly less than treating the adverse outcomes of hypothermic patients does.

The cost of preventing hypothermia tends to be reasonably low-cost, in part because it's reasonably low-tech. It's not something that requires a lot of high-end equipment. But it's a step beyond offering patients an extra blanket or a pair of socks, or convincing your surgeons to allow the thermostat to be turned up a few degrees; it requires some purchases. On the other hand, though, once a person becomes even mildly hypothermic, it's expensive and much more complicated to reverse.

Studies have shown that convective or forced-air warming systems, in which air is directed through a blanket covering or lying beneath a patient, are not only the most commonly used but also the most effective method of warming patients.

Forced-air warming is also cost-effective as compared to treating hypothermia's complications. Many manufacturers of forced-air systems offer pay-per-use agreements, placing the equipment in surgical facilities based on the number of units needed and their expected use. An informal survey of vendors found that the cost to the facility then averages $10 or less per use for the disposable blanket through which the forced air travels.

Conductive warming systems frequently use warm water circulating through a pad or mattress beneath the patient to transfer heat to a cooling body. Warming cabinets for fluids, blankets or both offer an auxiliary solution for perioperative prevention. While some conductive warmers can cost $3,000 to $5,000, and warming cabinets can range from $4,000 to $10,000, keep in mind their multiple uses and overall effect on patient care and costs. They're not massive capital investments like MRIs; with regular use, the per-patient cost is pretty low. You'd have to spend a lot of money on equipment per patient before you'd reach the amount of money that it costs to treat the complications of hypothermia.

In the overview, it could be said that patients don't necessarily need to be warmed. The key issue is to keep them from getting cold. That issue, one that many surgeons and nurses haven't taken as seriously as patients may have felt it, has definitely been garnering more attention in recent years as more healthcare experts have been examining what happens when patients got cold.

Identifying the problem is the first priority in managing the economics of patient warming. Develop a protocol not only for a strategic, orderly response to the hypothermic patient, but also policies toward prevention. Talk to your surgeons and staff and make them aware of what the condition is and why it's urgent to treat. Minimizing the complications of hypothermia is not only a critical measure in cost-effective patient care, it's also important to the care of the patient.

Clinical Consequences Of Mild Hypothermia

  • Patient discomfort. Shivering can cause elevated heart rate, labored breathing, muscle spasms, incisional pain and cardiac effects.
  • Coagulopathy. Hypothermia can inhibit platelet formation, reduce platelet count and impair coagulation pathway.
  • Increased blood loss. Mild hypothermia significantly increases blood loss and may also increase blood loss during regional anesthesia.
  • Wound infection. Studies show hypothermic patients are at greater risk for wound infection. Intraoperative hypothermia triggers vasoconstriction, which decreases partial pressure of oxygen in tissues and lowers resistance to infection.
  • Delayed wound healing. Vasoconstriction-induced tissue hypoxia may decrease the strength of the healing wound.
  • Impaired immune response. Results in wound infections and delays in wound healing.
  • Altered drug metabolism. Hypothermia causes decreased metabolism, which results in need for higher amounts of anesthetic agents and thus delays emergence from anesthesia.
  • Delayed PACU discharge. Mild hypothermia deceases drug metabolism, thus reducing cognitive performance.
  • Prolonged hospitalization. Complications associated with hypothermia such as wound infections and delayed wound healing can result in longer hospital stays.