Circadian rhythmicity and homeostatic stability in thermoregulation.

Stability and circadian variation in core body temperature (Tc) were believed to be homeostatic responses until well into the 20th century. Defense of a narrow thermoneutral range was well documented, whereas circadian oscillations were attributed to episodic biochemical and environmental stimuli or chronological stressors in life routines. Research in thermal physiology has illuminated several of the "black boxes" in the understanding of temperature regulation, and advances in chronobiology have shattered old paradigms. While these discoveries are still evolving, existing information provides valuable clues about physiological responses to heat loss or over-heating that could improve clinical assessment and intervention. Discoveries that circadian rhythm of Tc is regulated by an endogenous "clock" and is remarkably stable have helped to make it the most widely used circadian indicator. More recently, Tc was found to exert its own cyclic rhythm under free-running conditions. While some investigators claim that circadian and homeostatic processes are independent, there are conditions in which clinical distinctions are less clear. This overview reviews contemporary scientific findings about circadian and homeostatic processes in thermoregulation. Examples are drawn from human and animal research. Physiological responses and mechanisms are explained in relation to their relevance to clinical treatment or health care. Gaps in existing research and application are discussed.

New trends in thermometry for the patient in the ICU.

Modern engineering and space-age technology introduce innovations in thermometry at a crucial time in critical care history. Today's assessment and care decisions are based, in part, on emerging scientific evidence about thermoregulatory responses. Accurate body temperature measurements and the correct interpretation of their meaning are crucial for competent care. Confusion exists as to which instrument or site is "ideal." Interpretation of temperature correlations, between temperature sites or without consideration of linearity, has little meaning outside the clinical context. This article discusses hemodynamic and thermal conditions influencing regional body temperatures along with instrument accuracy, reliability, linearity, precision, safety, comfort, and need for staff training.

Perioperative problems: threats to thermal balance in the elderly.

The perioperative period is a time of thermal instability for older surgical patients. Beyond the elder persons vulnerability to intraoperative heat loss and hypothermia, the surgical procedure initiates host responses that affect body temperature. Technology and drug therapies often deliberately or inadvertently alter thermal balance. Alterations range from mild hypothermia to shaking febrile chills. A reasoned approach to preventing or caring for each of these alterations is based on an understanding of the dynamics of heat loss or heat gain. Early recognition of problems and appropriate action by perioperative nurses may forestall more serious consequences.

Mail by modem: the BITNET connection.

Nursing faculty in university settings are now able to communicate with colleagues around the country or in other parts of the world through electronic networks such as BITNET. This article describes how members of the Southern Nursing Research Society's (SNRS) Governing Board used the BITNET system for accomplishing the society's work. Essential hardware and software requirements for using the network are described. Guidelines for logging on, sending messages, and e-mail courtesy are explained. Examples are included for using the network for 1) research and manuscript collaboration; 2) organizational communication and planning; and 3) teaching activities.

Monitoring body temperature.

Vigilant and accurate assessment of thermal balance is imperative with the critically ill. Disease, injury, or pharmacologic activity can impair thermoregulation, leaving patients vulnerable to uncontrolled gain or loss of heat. Body temperature provides cues to onset of infection, inflammation, and antigenic responses, as well as indicating efficacy of treatment. With knowledge of heat transfer principles, physiologic processes that distribute body heat, and principles of thermometry, the nurse is better equipped to make reasoned clinical judgment about this important vital sign. Choices of instruments or measurement sites are influenced by needs to estimate either hypothalamic temperature or shifts in body heat. Need for continuous versus episodic assessment, availability or intrusiveness of equipment, and stability of the patient also influence choices. Monitoring devices, measurement sites and techniques, equipment limitations and precautions are discussed. Interpretation and application of assessment findings are presented as they relate to abnormally high or low temperatures, patterns of fever, and temperature gradients.

The febrile response in critical care: state of the science.

Fever is a dynamic alteration in thermal balance caused by effects of pyrogens on the hypothalamic thermostatic set point. Thermoregulatory function remains intact during fever, but temperatures are maintained at higher levels. Shivering and vasoconstriction drive temperatures higher while causing physical exertion and distress to the patient. Biomedical research reveals potential benefits of fever, because fever-producing cytokines stimulate host defense responses. Nursing care is aimed at making rational decisions for comfort and energy conservation while maximizing the immune response. In this article the pathophysiologic process and benefits of fever are reviewed and a conceptual approach to nursing care based on knowledge of thermoregulatory responses is proposed. Nursing care measures include assessment of alterations in thermal balance, selection of appropriate measures to modify or support physiologic responses, and evaluation of outcomes of therapy. Research-based direction for care is presented, as well as gaps in scientific knowledge.

Shivering. A clinical nursing problem.

Shivering is a common but complex phenomenon that occurs in many patient care situations. Its metabolic costs and cardiorespiratory consequences should not be underestimated, particularly for the seriously ill, debilitated, or elderly patient. Using a conceptual frame of reference for assessment and action, independent and collaborative actions can be planned to reduce the energy expenditure, distress, and loss of control imposed by severe shivering.

Temperature problems in the postoperative period.

Postoperative patients have difficulty maintaining thermal balance for several reasons. Normal thermoregulation is suppressed by anesthesia, neuromuscular blocking agents, and other drugs, and cool environmental conditions and exposure contribute to heat loss. Specific patient groups at high risk for hypothermia include infants, the elderly, and the neurologically impaired. Temperature drift, afterfall, shivering, malignant hyperthermia, and fever are among the temperature-related conditions requiring vigilant assessment and nursing action during the postoperative period.

Effects of extremity wraps to control drug-induced shivering: a pilot study.

Efficacy of a nursing intervention to control amphotericin B-induced, febrile shivering was tested in 40 hospitalized adult patients with cancer. Extremity wraps were used to modify the rate of heat loss from skin to prevent shivering stimulus. Duration of shivering and amount of meperidine required for shivering suppression were compared between treatment and control groups. Total shivering duration was shorter in the treatment group than in the control, p less than .005. Less meperidine was administered to the treatment group than to controls but differences were not statistically significant. The fact that nurses differ in their propensity to use a narcotic to treat shivering may make use of meperidine a poor measure of the intervention's efficacy. Shivering was found to significantly affect myocardial oxygen consumption (MVO2) among subjects who shivered. MVO2, as reflected in the rate pressure product, was found to be significantly higher during shivering (p less than .0001) than at pre- or postshivering periods.

Use of amphotericin B in immunosuppressed patients with cancer. Part One: Pharmacology and toxicities.

Potentially fatal fungal infections account for most of the prolonged fevers found in immunosuppressed patients with cancer. Amphotericin B (AmB) is the most effective drug available to treat these infections. This article, Part One of two parts, reviews the biochemical properties of AmB and its dosage and administration. Major toxicities and common side effects are discussed. Part Two uses the pharmacodynamics addressed in Part One as a basis for planning nursing interventions to prevent or suppress adverse reactions.

Use of amphotericin B in immunosuppressed patients with cancer. Part Two: Pharmacodynamics and nursing implications.

Nursing care of patients receiving amphotericin B (AmB) must address the underlying condition of the immunosuppressed patient with cancer and the iatrogenic responses induced by the drug. This review, the companion to "Part One: Pharmacology and Toxicities," focuses on nursing actions that consider both the drug's specific pharmacodynamics and the altered human responses caused by disease and therapy. Maximization of drug effectiveness and minimization of drug toxicity are key care goals.

Control of febrile shivering during amphotericin B therapy.

"Rigors" of febrile shivering often complicate therapy with amphotericin B (AmB) in immunosuppressed patients with cancer. Violent muscle contractions cause physical and emotional distress as well as dread of future therapy. This experimental study tested the effectiveness of a nursing measure in 20 hospitalized adult patients with cancer. In addition, the effects of shivering on myocardial oxygen consumption were studied. Based on Abbey's Model of Nursing Action, wraps of terry cloth toweling were applied to extremities to protect dominant skin sensors against heat loss. Patients with wrapped extremities had shorter, less severe shivering episodes than controls (p = 0.04) and required less meperidine for shivering suppression (p = 0.04). Shivering significantly elevated myocardial oxygen consumption, reflected in the rate pressure product (RPP), above pre- or post-shivering levels (p less than 0.0001). The study reflects first-year findings of a federally funded project.

Amphotericin B-induced shivering in patients with cancer: a nursing approach.

Shivering is a common and distressful reaction associated with administration of amphotericin B, a systemic antifungal agent. Shivering occurs as a result of the drug's intrinsic pyrogenicity, and thus resembles febrile shivering. This heat loss phenomenon has metabolic as well as psychologic costs. The intervention approach to amphotericin B-induced shivering includes reporting the phenomenon, restoring lost heat, modifying the rate of heat loss, altering the physiologic determination of heat loss, and giving drugs to suppress shivering. Specific suggestions for interventions are discussed. Supportive care of the patient with cancer who is receiving this drug is briefly mentioned as it relates to thermoregulatory principles. Possible areas of future inquiry into shivering suppression are mentioned.