Temperature Balance and Regulation In Health Care

Regulation In Health Care and Temperature Balance

What is Thermal Balance,Thermal Regulation,Nursing Care and Thermal Assessment,Thermal Regulation Patterns,Temperature Measuring Issues In Nursing,Newer Researches For Clinical Aspects of Thermal Regulation.

What is Thermal Balance

    Thermal balance is defined as a thermal “steady state” in which the loss of body heat is equal to the heat gain. In health, this balance produces a thermoneutral state, optimal for cellular function. 

    In humans, this state averages about 37°C±.05 for internal temperatures and 33.5°C±.05 for skin. Variations in body temperature respond to both homeostatic and circadian influences. 

Thermal Regulation 

    Circadian rhythm of core temperature is regulated by a remarkably stable endogenous “clock” which has helped to make it the most widely used circadian indicator. Hypothalamic thermoregulatory controls keep internal temperatures fairly stable, despite environmental changes and the propensity of heat to escape to cooler regions. 

    Metabolic and physical activity continually generates heat, even as it is constantly lost to the cooler environment. Current theory is that elaborate thermoregulatory control systems maintain temperatures within the optimal set point range. Compensatory cooling or warming mechanisms respond to deviations above or below this range. 

    Temperatures rising above this range evoke vasodilation and sweating, while falling temperatures cause vasoconstriction, shivering, and increased metabolic activity.Each physiological response increases or inhibits the transfer of heat by affecting the thermodynamics of conduction, convection, radiation, and evaporation. 

    Vasodilation warms the skin where heat is more easily lost to air, contact surfaces, or liquids. Vasoconstriction creates a poorly perfused insulative layer of tissue that conserves heat. In infants, cold exposure causes metabolic breakdown of brown fat to generate heat. In older children and adults, the primary means of heat generation is shivering.

Nursing Care and Thermal Assessment 

    Nurses have recognized the importance of assessing thermal balance as a vital health indicator for as long as the profession has existed. Body temperature provides an important vital sign of metabolic, neurological, and infectious activity. 

    Circadian rhythms, monthly cycles, and daily body temperature ranges are assurances of healthy variations. The pregnant mother provides heat exchange both for herself and the fetus; therefore, high maternal body temperatures, from fever, hyperthermia, or prolonged “hot tub” use, put the unborn infant at risk for neurological damage. 

    Temperature elevations in the acutely ill and injured may indicate either fever or hyperthermia. Each has its own dynamics and treatment. Fevers are usually self limiting. Thermoregulatory control is lost during hyperthermia and requires aggressive cooling treatment. 

    Temperatures above 42”C can cause irreversible neural cellular damage. Conductive cooling blankets, ice packs, and cooling fans are used to lower core temperatures. In immunosuppression associated with cancer treatment, fevers may indicate fulminating systemic infection. However, the immunosuppressed HIV-infected patient may become febrile from high cytokine levels, without obvious secondary infection. 

    In both groups, constant assessment of other indicators is necessary to rule out infection. Situations that promote heat loss or interfere with heat generations put patients at risk for hypothermia. The neonatal nurse must be extremely sensitive to the low-birthweight infant's need for external heat source. 

    Unable to shiver, the neonate expends oxygen to metabolize brown fat and can easily become hypoxic from cold exposure. Declining metabolic and vasomotor activity makes elders particularly susceptible to heat loss during surgery, trauma, or outdoor exposure. Hypothermic states can destabilize thermoregulatory function further, eventually leading to death.

Thermal Regulation Patterns 

    Fever patterns were used to detect the onset and progress of infections since early times. It was recognized that high temperatures could lead to brain damage, so nurses routinely cooled patients with fever or heat stroke with ice packs, cooling sponge baths, or circulating fans. 

    In the 1970s, nurses used conductive cooling blankets, with refrigerated circulating coolant, to treat refractory hyperthermia. Sharp gradients between skin and core temperatures stimulated vigorous and distressful shivering. Interventions to prevent shivering were among the earliest to be tested by nurses. 

    Interest in and awareness of temperature variations became more acute among nurse researchers when advanced technology in thermometry was introduced to clinical settings. In the 1970s, thermistor probes in hemodynamic monitoring systems made pulmonary artery temperatures possible in some critical care settings. As probes became available for bladder, tympanic membrane, and skin temperatures, studies of gradients between body regions and measurement sites were common. 

    Variation in quality and precision of instruments made studies of reliability and accuracy important. Recognition of malignant hyperthermia, a rare but lethal genetically-linked disorder occurring when susceptible persons receive anesthetic agents, led to closer surveillance of peri-operative body temperature. 

    This precaution reduced mortality from hyperthermia in this uncommon condition, but also brought to awareness the high incidence of low body temperatures in most surgical patients. 

    Increased survival of preterm infants in the 1970s created increased concern for thermal balance of vulnerable infants. Studies of environmental influences, warming devices, and skin-to-skin contact were made possible by sophisticated continuous skin temperature monitors.

Temperature Measuring Issues In Nursing 

    Temperature measurement issues continue to dominate clinical nursing research, stimulated by commercial development of new technology in thermometers. There is an on-going program of research in body temperature measurement by Erickson and colleagues (Erickson, RS, 1999; McKenzie & Erickson, 1996), who have compared oral, skin, rectal, and tympanic membrane measurement sites in children and adults. 

    Findings reassure nurses that oral measurement provided reliable intermittent thermal assessment in afebrile patients. While placement site and method of insertion yield statistically significant differences, they are of less clinical importance. 

    Erickson's work was set apart from other contemporary studies by her appropriate statistical treatment beyond simple correlations and by meaningful interpretation of device reliability, accuracy, and linearity. In the past decade, nurse researchers began drawing inferences from observed relationships between thermal changes and other variables. 

    Gradients between skin and core temperatures initiate thermoregulatory responses (see Shivering). Studies have shown the importance of thermal gradients and rate of cooling in initiating shivering in a comparison of cooling blanket temperatures (Caruso, Hadley, Shukla, Frame, & Khoury, 1992; Sund-Levander & Wahren, 2000). 

    Nursing research has also tested methods to alleviate adverse effects of warming and cooling in patients of all ages. Particularly vulnerable are the preterm infant, the elderly, and patients recovering from surgery, cardiopulmonary bypass, or traumatic injury. 

    Anderson (Anderson, Chiu, et al., 2003) pioneered “kangaroo care” as a method of maintaining thermal balance in preterm and term infants. Drawn from perinatal practices of Western Europe, this method uses skin-to-skin care for infants held against the skin under the mother or father's clothing. 

    Self-demand breast-feeding and lactation were promoted by close constant maternal contact. More recently, the relationships between the infant's body temperature and environment, circadian rhythm, and parental co-sleeping have been investigated (Thomas & Burr, 2002). 

    Several studies have compared cooling interventions in febrile adults with similar findings (Caruso et al., 1992; Henker et al., 2001). Most concluded that antipyretic drugs are as effective as cooling without inducing distressful shivering. In a controlled trial with febrile patients with HIV disease, insulating skin against heat loss actually kept peak febrile temperatures lower (Holtzclaw, 1998). 

    While numerous small studies in nursing have tested various products that cool febrile patients or restore heat loss in perioperative patients, they are often empirical in nature. By contrast, the investigations mentioned above are theoretically based on principles of thermodynamics and physiological responses. They seek to explain mechanisms, predict consequences, and alleviate hazards of altered thermal balance.

Newer Researches For Clinical Aspects of Thermal-Regulation

    Some of the newer areas of research conducted by nurse scientists related to thermal balance are studies using animal models to demonstrate effects of exercise on thermoregulatory responses (Rowsey, Metzger, & Gordon, 2001) and circadian influences on thermoregulation in obesity (Jarosz, Lennie, Rowsey, & Metzger, 2001). 

    As more nurses enter fields of genetics, immunology, and molecular biology, they will play important roles in seeking origins and mechanism of thermoregulatory responses. New avenues for nursing research in thermal balance emerge as new situations of vulnerability develop and measurement techniques are advanced. 

    At particular risk is the rapidly growing population of the frail elderly. Declining metabolic rate, lower vasomotor sensitivity, and diminishing insulation from body fat make this group vulnerable to extremes in heat or cold. The existence and treatment of thermoregulatory failure in home bound patients is an area that nursing has not yet systematically studied. 

    Improved survival of individuals with neurological, vasomotor, and endocrine impairments and with extensive burns creates new situations where thermal balance is altered. Only recently have nurses begun to investigate relationships between the circadian city of body temperature and the effectiveness of other therapies. 

    Study and intervention are needed in addressing thermal balance, thermal perception, and thermal comfort during a health alteration variety of life events and