Understand hypothermia and its causes
Hypothermia, defined as a core temperature of less than 37 degrees Celsius or 98.6 degrees
Fahrenheit, can adversely affect a patient’s cardiovascular, respiratory, immune, vascular, and
renal systems. It can result in hypertension and increased myocardial oxygen demand which
causes cardiac arrest, fast breathing, a decrease in respiratory minute volume, bronchorrhea and
bronchospasm, hypoventilation, pulmonary edema, bleeding, decrease in blood flow to all
organs, kidney failure and other adverse conditions.
According to Sandy Berreth RN, MS, CASC, administrator of Brainerd Lakes Surgery Center in
Baxter, Minn., and the Clinical Guideline for the Prevention of Unplanned Perioperative
Hypothermia published by the American Society of PeriAnesthesia Nurses, hypothermia is often
exasperated in surgery by the following factors:
- extremes of ages;
- female sex;
- ambient room temperature;
- length and type of surgical procedure;
- pre-existing conditions (peripheral vascular disease, endocrine disease, pregnancy, burns,
- open wounds, etc.);
- significant fluid shifts;
- use of cold irritants;
- use of general anesthesia;
- use of regional anesthesia;
- patients with pre-existing medical conditions;
- anxiety and fear, which can trigger changes in body temperature; and
- weight.
Other factors potentially exasperating hypothermia include general anesthesia, which depresses
the hypothermia thermoregulation center; depressants, which eliminate important bodily
mechanisms that create heat; and various drugs can also accelerate heat loss.
Cost of hypothermia
A study that’s often referred to when talking about the costs of hypothermia is the 1999 study
"Maintaining intraoperative normothermia: A meta-analysis of outcomes with costs" by
Christine Brown Mahoney, RN, PhD, MS, and Jan Odom, RN, MS, CPAN, FAAN. It concludes
that hypothermia averaging just 1.5 degree Celsius less than normal can add between $2,500 and $7,000 per surgical patient because of adverse affects; post-surgical hypothermia increases a
patient’s need for blood products and increases ventilator and recovery stay. Patients who
experience hypothermia are also more likely to be readmitted and get surgical site infections.
"By keeping the body warm, you help it perform better by maintaining its immune function,"
says Mike Walters, general sales manager of Progressive Dynamics, a manufacturer of six
different types of warming covers used to treat and prevent hypothermia.
Preventing hypothermia is also a critical component of maintaining the quality care patients
expect from your surgery center.
"One of the reasons we want to keep them warm is that when a patient’s temperature drops, it
can cause pain, nausea and vomiting," says Ms. Berreth. "We want to make them comfortable. Also, if a patient remains normothermic, they’re recovery times are quicker and they do better, which leads to reduced costs.”
Here are four steps to help your center prevent and also be prepared for the possible onset of
hypothermia.
1. Warm preoperatively, intraoperatively and postoperatively
"Usually the one thing people complain about is the hospital/ASC room’s temperature — they’re
cold," says Ms. Berreth. "The key is to keep patients warm. Some surgery centers (warm
patients) preoperatively, some do it intraoperatively, some do it postoperatively. The key, however, is to start before surgery— it’s a best practice."
Studies have shown that you only need 30 minutes of warming to build up protection in the body
against hypothermia, which is vital because of what happens when surgery starts.
"When [you] open the patient, the body temperature decreases," says Mr. Walters. There are
many passive and active techniques an organization can use to warm a patient, according to Mr.
Walters. These include:
- insulation: warm blankets, socks, head coverings and circulating water mattress;
- increasing ambient air;
- reflective thermal drapes;
- insulating blankets;
- convective patient warmers;
- IV fluid warmers;
- radiant warmers;
- heated humidified gases;
- washing of the bladder, stomach, chest and abdominal cavities;
- underbody gel; and
- heated surgical tables
2. Get forced air
Mr. Walters and Ms. Berreth agree that forced-air warming is the most effective method for
warming.
"The most effective warming is over-body, not under-body," says Mr. Walters. "Your heat loss
is going up. When you heat from the bottom, you need something on top to hold it in."
Surgery centers should consider investing, if they have not already, in a forced-air machine.
"What most surgery centers do to guard against a person’s temperature dropping, is have some
sort of forced air machine, whether a Bair Paw, Bair Hugger, an air-heated cover (such as LIFE-
AIR manufactured by Progressive Dynamics) — something which will keep patients continually
warm," Ms. Berreth says.
3. Continuously monitor the patient’s temperature
Whichever warming technique or equipment you use, make sure to consistently monitor the
patient’s temperature. The Clinical Guideline for the Prevention of Unplanned Perioperative
Hypothermia notes that, “The greatest temperature decline occurs during the first hour of
surgery.”
"Most surgery centers have standards for doing vital signs," Ms. Berreth says. "Vital signs
should always include monitoring temperature — before, during and after surgery. Basically, the
patient may complain of cold, may shiver or experience a drop in temperature. Treat these things
accordingly. Examine and respond to the whole situation. Just add a blanket, for example, if [the
patient’s] chilliness is simply a result of anxiety. If a patient is not conscious, look for signs and
symptoms that they are getting cold."
These symptoms according to the Clinical Guideline for the Prevention of Unplanned
Perioperative Hypothermia include:
- bouts of shivering;
- grogginess and muddled thinking;
- violent shivering
- stilted, jerking movement;
- slow, shallow breathing;
- slow, weak or irregular pulse;
- cold, pale, or blue-gray skin.
- trunk of the body is cold to the touch;
- muscle stiffness;
- trembling on one side of the body;
- little or no breathing; and
- non-existent pulse.
If you have operations that last longer than a half hour, make sure to check the patient’s
temperature every 30 minutes. "This kind of monitoring is extremely important," Ms. Berreth says.
4. Make sure fluids and other warmers are available
"Some ASC feel they can’t afford a lot of these warming devices," Ms. Berreth says. "But they can afford warming fluids, cabinets, and gowns. It is essential to do something; you can’t just let it go because that, in turn, causes complications that an ASC don’t even want to think about. It is standard in most surgery centers to use warmed fluids preoperatively and intraoperatively."
14 million surgical patients suffer from inadvertent hypothermia each year1. It is much easier to prevent hypothermia than to treat it, and with new warming technologies, there is no excuse for surgery centers to regard hypothermia complacently, says Ms. Berreth. "This is one of those easier slam-dunk things," she says, "Keep body temperature at a normal level and you stop a lot of complications."
Note: View Clinical Guideline for the Prevention of Unplanned Perioperative Hypothermia available at: www.aspan.org/hypothermia.htm.
1. Cuming R and Nemec J. Perioperative hypothermia: complications and consequences. Vital Signs. XII No. 22, Nov. 6, 2002.
