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Sweat gland activity is reduced to minimize evaporation.

Shivering occurs; muscles contract and relax out of sequence with each other, thus generating heat.

The body increases catecholamine and thyroxine levels, elevating the metabolic rate in an attempt to increase temperature.

(Marieb and Hoehn 2010)

All these changes contribute to a rise in metabolism with an increase in carbon dioxide excretion and the need for oxygen. This leads to an increased respiratory rate. When the body temperature reaches its new ‘setpoint’ the patient no longer complains of feeling cold, shivering ceases and sweating commences.

There are several grades of pyrexia, and these are described in Table 12.5.

Table 12.5 Grades of pyrexia

Lowgrade pyrexia Normal to 38°C Indicative of an inflammatory response due to a mild infection, allergy, disturbance of body tissue by trauma, surgery, malignancy or thrombosis

Moderate to highgrade pyrexia 38–40°C May be caused by wound, respiratory or urinary tract infections

Hyperpyrexia 40°C and above May arise because of bacteraemia, damage to the hypothalamus or high environmental temperatures

Evidencebased approaches

Rationale

Core body temperature measurements are taken to assess for deviation from the normal range that may indicate disease, deterioration in condition, infection or reaction to treatment.

Body temperature measurement is part of routine care in clinical practice and can influence important decisions regarding tests, diagnosis and treatment (Le Frant et al. 2003). Temperature needs to be measured accurately and monitored effectively to enable temperature changes to be detected quickly and any necessary intervention commenced (Watson 1998). Temperature assessment accuracy depends on several factors: measurement technique, device type, body site, healthcare professionals’ training and competence. Temperature recording is a core assessment (and reassessment) in nursing practice, but can create clinical issues if not performed appropriately (Docherty 2000).

Indications

Conditions in which a patient’s temperature requires careful monitoring include the following.

Patients with conditions that affect basal metabolic rate, such as disorders of the thyroid gland, require monitoring of body temperature. Hypothyroidism is a condition where an inadequate secretion of hormones from the thyroid gland results in slowing of physical and metabolic activity; thus the individual has a decrease in body temperature. Hyperthyroidism is excessive activity of the thyroid gland; a hypermetabolic condition results, with an increase in all metabolic processes. The patient complains of a low heat tolerance. Thyrotoxic crisis is a sudden increase in thyroid hormones and can cause a hyperpyrexia (Walsh 2002).

Postoperative and critically ill patients require monitoring of temperature. The patient’s temperature should be observed preoperatively in order to make any significant comparisons. In the postoperative period the nurse should observe the patient for hyperthermia or hypothermia as a reaction to the surgical procedures (Wagner 2006).

Patients with a susceptibility to infection, for example those with a low white blood cell count (less than 1000 cells/mm3) or those undergoing radiotherapy, chemotherapy or steroid treatment, will require a more frequent observation of temperature. The fluctuation in temperature is influenced by the body’s response to pyrogens. Immunocompromised patients are less able to respond to infection. Bacteraemia means a bacterial invasion of the bloodstream. Septic shock is a circulatory collapse as a result of severe infection. Pyrexia may be absent in those who are immunosuppressed or in the elderly (Neno 2005).

Patients with a systemic or local infection require monitoring of temperature to assess development or regression of infection.

Pyrexia can occur when patients are receiving a blood transfusion but severe transfusion reactions usually occur within the first 15 minutes of starting (BCSH