Body temperature is a numerical expression of the body's heat and metabolic activity balance and can be a major indicator of a person's health status. Assessing a patient's body temperature is a common procedure nurses perform to monitor for signs of infection, environmental exposure, shock, ovulation, or therapeutic response to medications or medical procedures. A normal body temperature can be a potentially positive sign that the patient isn't experiencing a disease process, infection, or trauma and that the body's cells, tissues, and organs aren't under metabolic distress.
We'll review 12 different ways to assess a patient's temperature but, first, let's take a closer look at temperature norms, highs, and lows.
Body temperature can vary among individuals. Certain things can affect a person's body temperature, such as gender, age, and environmental exposure. Women typically have a higher body temperature than men, especially during ovulation. Older patients may have a lower body temperature, and babies may have a higher normal body temperature. Environmental exposure to cold or heat can raise or lower a patient's body temperature. Other common factors that can influence body temperature include emotions, stress, depression, metabolic disturbances, cancer (such as brain tumors), medications, and medical or surgical procedures.
With all of this in mind, an oral temperature for adults normally ranges from 97° F to 99.5° F (36.1° C to 37.5° C); tympanic temperatures read 0.5° F to 1° F higher (97.5° F to 100.5° F [36.3° C to 38° C]); rectal temperatures are 1° F higher (98° F to 100.5° F [36.6° C to 38° C]); and axillary temperatures read 1° F to 2° F lower (96° F to 97.5° F [35.5° C to 36.3° C]). Core body temperature is the internal temperature within the central body cavity, such as areas near the heart or abdomen. Measuring core body temperature is the most accurate method of assessment.
The highs and lows
The body can tolerate fleeting periods of hyperthermia or hypothermia. However, continuous exposure to extremely high or low body temperatures can be potentially lethal and may cause profound localized and systemic tissue and organ damage. If a person is hypothermic (very low temperature), his or her body will try to generate heat by shivering. Hypothermia begins at 95° F (35° C), and patients will lose consciousness at 91° F (32.7° C). A temperature below 95° F is a medical emergency and you should consult with the healthcare team immediately. Common medical treatments to reverse hypothermia include application of warming blankets or a warming device or infusion of warm saline solution through a peripheral I.V.
If a person is hyperthermic (very high temperature), his or her body will try to cool itself by sweating to cool the skin's surface. During hyperthermic episodes, the heart rate, cardiac output, and metabolic rate increase, resulting in increased global tissue and organ oxygen consumption. Monitor a hyperthermic patient's oxygen level frequently; supplemental oxygen may be needed. According to recent research, patients with underlying pulmonary disease and sepsis are more likely to require supplemental oxygen.
Temperatures of 114° F (45.5° C) are incompatible with life. Children less than age 6 can have febrile seizures when their temperature is only 100.4° F (38° C). Typically, when temperatures reach 106° F (41.1° C), it's a medical emergency because patients are at high risk for convulsions and heatstroke. Emergency medical treatment to reverse hyperthermia may include infusing chilled saline solution through a peripheral I.V., applying a cooling blanket, or placing ice packs to the groin and armpits.
When your patient has a temperature that's above or below the normal range, perform a thorough head-to-toe clinical assessment to help identify potential underlying causes, such as infection or metabolic disturbances. Don't medicate the patient for an elevated temperature until you've consulted with the healthcare team. The healthcare provider may ask for further testing, such as serum blood cultures, to be performed before administering antipyretics or antibiotics.
Immediately document your patient's temperature and closely follow temperature trends because these can be an early indicator of worsening clinical status. Many healthcare facilities have introduced care bundles that direct nursing interventions when patients are hypothermic or hyperthermic (see Care bundle interventions for hypo- and hyperthermia).
The most common methods of temperature assessment that carry the least amount of risk for patient injury are the use of glass or electronic digital thermometers to measure oral, rectal, axillary, or vaginal temperatures; basal thermometers; temporal artery thermometers; tympanic thermometers; and liquid crystal forehead temperature strips. These methods can be utilized in healthcare settings and also within the patient's home.
Although the more invasive methods are more accurate, they carry a higher risk of potential complications, so they aren't routinely utilized in areas outside of a critical care or surgical setting. Examples of invasive methods of temperature assessment are esophageal and rectal temperature probes, temperature-sensing indwelling urinary catheters, temperature-sensing pulmonary artery (PA) catheters, a cardiopulmonary bypass (CPB) machine, and extracorporeal membrane oxygenation (ECMO). Although a CBP machine and ECMO can be utilized to assess and control the patient's body temperature, they're labor intensive and only rarely utilized during specific, controlled medical and surgical procedures, such as open-heart surgery and in acute heart or lung failure, by specially trained OR and critical care teams.
Potential risks associated with invasive methods of temperature assessment include hemorrhage, esophageal tissue perforation, cardiac arrhythmia, cardiovascular collapse, myocardial infarction, and even death. When utilizing one of these invasive methods, ensure that the patient is closely monitored by the advanced cardiovascular life support (ACLS) certified healthcare team and a crash cart equipped with ACLS medications and equipment is readily available. As the patient's clinical condition stabilizes and improves, you should transition the patient to a less invasive method of temperature monitoring.
Below are basic descriptions of each temperature assessment device.
• Glass thermometers
—Mercury thermometer: This type of thermometer is a fragile glass tube with a thin internal line of mercury that extends from the bulb to the end of the tube. The mercury within the bulb of the tube reacts to the temperature it senses and drives a specific volume of mercury up the tube. When the thermometer is tilted, a solid line of mercury that ends beside the correlating temperature can be visualized. Although mercury thermometers are no longer recommended for use because of the potential health risks of mercury exposure if the thermometer breaks, you may still see them in practice. Mercury can quickly vaporize into a toxic gas that has no smell, causing potentially irreversible damage to the central nervous system, liver, and kidneys if inhaled. If you're using a mercury thermometer and it breaks, quickly open the window to allow ventilation, evacuate all patients and staff from the area, and securely close all doors in the room. Follow your healthcare facility's policy on how to safely dispose of a mercury spill. If your facility has no mercury spill policy, you should contact the Poison Control Center or Environmental Protection Agency for guidance.
—Galinstan thermometer: This is a glass tube that has a thin line of a liquid chemical compound mixture of alloy metals inside the length of the tube from the bulb to the tip. As the temperature is sensed in the bulb, it causes the nontoxic metal alloy mixture to slowly rise inside the tube, eventually stopping at the correlating temperature. The FDA approved Galinstan thermometers as user- and environmentally friendly, with easy cleanup if broken—just use soap and water.
• Electronic digital thermometer
A digital thermometer is a small, handheld plastic device with a window that digitally displays the temperature. For infants, pacifier thermometers are also available. Electronic digital thermometers can be designated to assess axillary, rectal, or oral temperatures. However, ideally any thermometer that has been utilized to take rectal temperatures shouldn't be utilized to assess axillary or oral temperatures. Despite stringent cleaning techniques, it remains difficult to absolutely eradicate the risk of E. coli contamination.
• Basal thermometer
A basal thermometer can detect small, incremental, elevated changes in a woman's body temperature that can signal ovulation and increase the likelihood of conception. Basal temperatures should be measured consistently in the same way each morning orally, vaginally, or rectally. Basal thermometers look similar to a digital thermometer; however, they register temperature in increments of 0.1° F, whereas a regular digital thermometer typically only displays in increments of 0.2° F. Basal thermometers usually only require 30 to 60 seconds to display an accurate result. An elevation of 0.4° F or higher typically signals ovulation has occurred.
• Temporal artery thermometer (TAT)
The TAT is an accurate, portable, lightweight, wandlike instrument with a tilted infrared sensor at the tip. TATs use an infrared scanner to measure the temperature of the temporal artery in the forehead. The thermometer captures heat that's naturally released from the skin over the temporal artery. Because arteries receive blood directly from the heart, this is a good option for noninvasively detecting core temperature. In a recent research study that compared the TAT with the highly accurate PA catheter that measures blood temperature, the TAT was found to be very accurate. Unlike the PA catheter, the TAT is noninvasive, painless, and can be reused for many years. The TAT is gently applied to the dry skin of the forehead and moved in one quick, fluid motion across the forehead, behind the ear, and down the neck. A digital reading will appear with the temperature result on the scanning tip display window within 2 to 10 seconds. According to manufacturer, TATs recognize changes in temperature quicker than axillary, oral, or rectal methods. TATs work best for patients over age 6 months.
• Tympanic thermometer
This is a handheld, wandlike device with a curved scanning sensor that works by using an infrared light to detect thermal radiation that's emitted from the tympanic membrane. The device calculates this emission into a numeric temperature result that appears on the display screen. The scanning tip should be gently placed in the ear canal and then slowly inserted against the tympanic membrane snugly. Poor technique, such as simply placing the scanning sensor in the ear canal and not snugly against the tympanic membrane, can result in an inaccurate reading of up to 2.8° F. Also, if cerumen (ear wax) is present or if you don't wait 3 minutes between taking repetitive tympanic temperatures, an inaccurate reading may result. Don't use a tympanic thermometer if the patient is complaining of an ear ache, has had Eustachian tubes placed, or has facial or head trauma.
• Liquid crystal forehead temperature strip
This is a latex-free, disposable, adhesive strip that can be applied to the forehead. These strips contain imbedded liquid crystals and chemical compounds that react to the temperature (heat) of the skin by changing colors. After it has been on the forehead for approximately 2 minutes, the color will illuminate a line and correlating numeric temperature. The strips measure temperatures ranging from 96.6° F to 104.6° F (35.8° C to 40.3° C). Consider use for infants, children, and adults with cognitive deficits because they're painless.
• Esophageal temperature probe (ETP)
The ETP is an 18-in (45.7 cm) long, thin, flexible catheter that has a rounded tip that should be lubricated with water-soluble lubricant before being placed through the nares or mouth, extending into the esophagus at least 2 to 3 in (5 to 7.6 cm). The external end portion of the catheter has a small, coated wire with a plug that can be attached to a telemetry monitor for continuous temperature monitoring. After you have the sensor in the correct place, secure it in place by wrapping a thin piece of hypoallergenic tape around the sensor and attaching it firmly to the nares. This will prevent the ETP from migrating into the stomach or out of the naris. Only place an esophageal core temperature sensor into the mouth of a sedated patient on a ventilator because it can cause gagging and result in discomfort and aspiration pneumonia. The ETP is reported to be one of the most accurate methods of obtaining temperature results because it's inside a central body cavity. It's contraindicated in patients with facial trauma, esophageal strictures, and nasopharyngeal or esophageal cancer. This method can only be utilized in patients who are N.P.O. because consuming food or water will cause an abnormally false high or low temperature for up to 30 minutes after consumption.
• Rectal temperature probe (RTP)
The ETP and RTP are the same device but can be used in either orifice depending on the patient's medical condition. Again, the tip should be lubricated with water-soluble lubricant, and then placed approximately 3 in (7.6 cm) inside the rectal vault. The RTP can also be attached to a telemetry monitor cable for continuous temperature monitoring. It's most commonly used in patients who are unconscious, have facial trauma, are critically ill, have suspected hypothermia or heatstroke, or those with altered mental status. The RTP is contraindicated in patients who have rectal trauma, rectal bleeding, recent rectal surgery, a colostomy, hemorrhoids, proctitis, or fecal impaction/diarrhea, and in patients who are taking anticoagulants. If the patient experiences a vasovagal response or a sudden drop in heart rate or BP while you're inserting the RTP, remove the sensor immediately and call for the assistance of the healthcare team. Although vasovagal responses are rare during placement, they can occur.
• Temperature-sensing indwelling urinary catheter
This is a special type of indwelling urinary catheter with a sensor that measures bladder temperature. The sensor is imbedded within the catheter and extends the length of the catheter to a small, flexible, external wire below the inflation balloon lumen that can be attached to a telemetry monitor for continuous temperature monitoring. Frequently utilized in CCUs, the benefit of this device is that it can provide continuous monitoring of extremely accurate core body temperature and causes no additional discomfort or risks than a basic indwelling urinary catheter.
• Temperature-sensing PA catheter
This is a large-bore, highly accurate multi-lumen catheter that's placed in a large vein and advanced until it reaches the PA. Its primary purpose is to monitor PA pressures and diastolic function. One of the internal lumens is a thermistor that directly monitors the temperature of the blood within the PA as it passes over the catheter with each heartbeat. The external portion of the thermistor is then connected securely to a telemetry monitor that displays the PA blood temperature on the monitor screen. PA catheters are generally only placed for short periods of time in critically ill patients with severe symptomatic systolic dysfunction. Both the placement and maintenance of PA catheters carry great risk; they're typically removed within 24 to 72 hours.
• CPB machine
The CPB machine is utilized in a cardiac surgical suite to divert blood away from the heart and lungs during open-heart surgery. Incisions are made in the right atrium, vena cava, or femoral artery, shunting blood from entering the heart. The vessel is then attached to a cannula tube that diverts the oxygen-depleted blood into the CPB machine where blood temperature is continuously monitored. The blood can be cooled or warmed by the CPB machine's heat exchanger and filtered to remove carbon dioxide and replenish it with oxygen. A second cannula is placed in the ascending aorta or femoral vein to shunt filtered oxygen-replenished blood back into the circulatory system where it delivers oxygen-rich blood to the body's tissues and organs. Although a CPB machine can be used to induce medical hypothermia and resolve extreme hyperthermia, it's very rarely used for this purpose because of the surgical complication risks, costs, and labor demands of the healthcare team. A CPB machine can only be utilized for short periods of time, typically less than 45 minutes, to minimize the risk of permanent neurologic or cardiac insult.
An ECMO machine can be used for longer periods of time than a CPB machine. It's labor intensive and requires a dedicated perfusionist, nurse, and respiratory therapist to maintain. During cardiac and acute pulmonary procedures, as the blood is filtered through the ECMO machine, the blood temperature is monitored by the heat exchanger component and cooled or warmed, as needed, as carbon dioxide is removed and oxygen is replenished. ECMO is rarely utilized to correct severe hyperthermia or induce medical hypothermia because of the risks of medical complications, costs, and labor required for the healthcare team to maintain.
When you're informed about the various options available to assess your patient's body temperature, you can choose the most appropriate medical device for the patient's specific clinical needs. And now you know!
Care bundle interventions for hypo- and hyperthermia
- Initiate two large-bore (18 gauge or larger) peripheral I.V. lines or place a central venous catheter that will allow the healthcare team to administer large volumes of warmed I.V. fluid, blood, or blood products.
- Assess all invasive lines for signs of potential infection.
- Assess complete blood cell (CBC) counts for pancytopenia, leukopenia, or elevated white blood cell (WBC) count.
- Assess the fibrinogen, prothrombin time, partial thromboplastin time, and international normalized ratio for potential coagulopathies because these patients are prone to increased bleeding tendencies when rewarmed and increased clotting tendencies when hypothermic.
- Consider placing a nasogastric (NG) tube unless it's contraindicated because NG tube lavage can be effective at safely raising the core body temperature.
- Consider placing a three-way bladder irrigation catheter because bladder catheter lavage can be effective at safely raising the core body temperature.
- Place an esophageal or bladder thermometer immediately to allow for accurate temperature monitoring.
- Patient should be immediately placed on a continuous ECG monitor because they're at risk for potentially lethal arrhythmias during both the hypothermic and rewarming phase.
- Perform frequent and thorough skin assessments to observe for areas of localized tissue ischemia (frostbite).
- Obtain a thorough social, medical, and medication history because patients who take beta-blocker medications; have peripheral vascular disease, Raynaud phenomenon, or diabetes; or who smoke are most at risk for frost bite.
- Apply a warming blanket or another warming device.
- In emergent situations, healthcare teams may consider inserting a peritoneal dialysis catheter to lavage the peritoneal cavity with warmed saline solution.
- Perform frequent neurologic assessments to monitor for neurologic injury or deficits caused by vasoconstriction to the brain.
- Practice meticulous hand washing.
- Obtain blood cultures before initiating antibiotic or antipyretic therapy.
- Administer broad-spectrum antibiotics.
- Remove unnecessary I.V. catheters.
- Monitor the patient's temperature every hour and as needed until the body temperature is less than 101.5° F (38.6° C), then monitor temperature every 4 hours for 72 hours.
- Assess all invasive lines for signs of potential infection.
- Assess CBC counts for pancytopenia, leukopenia, or elevated WBC count.
- Apply a cooling blanket if the patient's temperature remains above 101.5° F after antipyretic medication.
- Utilize seizure precautions if the patient's temperature remains above 102.9° F (39.3° C).
- Perform a thorough physical exam and medical-surgical history, asking specifically if the patient has had any recent surgeries (general anesthesia can cause malignant hyperthermia) or falls and observing for neurologic deficits.
12 temperature assessment devices
- Glass thermometers
- Electronic digital thermometers (oral and pacifier)
- Basal thermometers
- Temporal artery thermometers
- Tympanic thermometers
- Liquid crystal forehead temperature strips
- Esophageal temperature probes
- Rectal temperature probes
- Temperature-sensing indwelling urinary catheters
- Temperature-sensing PA catheters
- CPB machine
Want to know more about temporal artery thermometers? Check out our blog at www.NursingMadeIncrediblyEasy.com
did you know?
As of October 2008, 13 states have laws that limit the manufacture, sale and/or distribution of mercury thermometers: California, Connecticut, Illinois, Indiana, Maine, Maryland, Massachusetts, Michigan, Minnesota, New Hampshire, Oregon, Rhode Island, and Washington. Mercury thermometer swaps are offered. These thermometer swaps allow citizens to trade their old mercury thermometers for a new mercury-free thermometer at no charge. To find out additional information, contact your local state department of health or department of environment and conservation.