Nursing Care for Shivering What is Shivering
Shivering is defined as the involuntary shaking of the body and serves as the primary defense mechanism against cold in adult humans. It is characterized by prolonged, generalized involuntary contractions of skeletal muscles, typically beyond voluntary control. Thermo-regulatory shivering differs from transient tremors or “shivers” that occur due to emotions such as fear, joy, or other forms of sympathetic arousal.
Shivering is triggered when heat loss activates specific sensors in the skin, spinal cord, and brain. Sensory impulses are received and processed in the pre-optic area of the hypothalamus. When the integrated thermosensory information indicates that the body temperature is dropping below the optimal “set point” range (see Thermal Balance), shivering is initiated.
The shivering center located in the posterior hypothalamus is activated, sending impulses through the anterior spinal routes of the gamma efferent system. Heat is produced by the oscillation and friction of the fibrous muscle spindles within the fuse motor system. Interestingly, shivering can occur during a fever despite rising body temperatures because the set point is elevated by circulating cytokines and other pyrogens.
Results of Shivering
The effects of shivering on seriously ill or vulnerable patients are sometimes underestimated, as it may appear to be a harmless compensatory warming response. However, the aerobic activity generated by intense shivering can increase oxygen consumption by 3-5 times, comparable to activities like shoveling snow or cycling.
This leads to oxidative phosphorylation of glucose and fatty acids, thereby increasing metabolic demands. While healthy individuals may tolerate the energy expenditure of shivering for short durations, it poses risks for specific patient groups, including cardio-respiratory, metabolic, and thermal instability.
Uncontrollable shivering can be distressing for patients and frequently occurs in environments with cool ambient temperatures, patient exposure, or therapies that induce fever. Patients often recall shivering as a negative aspect of experiences such as postoperative recovery, childbirth, antifungal drug administration, blood transfusions, or other hospital-related events.
Nursing research has documented the correlates and consequences of shivering to identify adverse effects in postoperative care, febrile illnesses, and during induced hypothermia. Intervention studies have evaluated the effectiveness of nursing measures to prevent shivering during surface cooling and febrile chills. A significant aspect of these studies has been the standardization of shivering measurement using a shivering severity scale developed by Abbey and colleagues in 1973.
Shivering in Healthy Persons
Although shivering has been extensively studied by physiologists in healthy humans and animals, clinical interest remained limited until the 1970s. Abbey and Close (1979) conducted a study using ordinary terry cloth towels as insulation to protect thermosensitive areas of the skin during the use of cooling blankets.
Shivering during surface cooling was a significant issue at that time, often treated with chlorpromazine, a drug that has undesirable side effects. The wrapping intervention was based on existing physiological research that demonstrated the dominance of heat loss sensors on the hands and feet in triggering shivering.
This landmark pilot study showed that insulating the extremities effectively controls shivering and enhances comfort without the need for medication, even when surface cooling induces hypothermic temperatures.
Body Cover During Shivering
Major studies by nurse investigators, including Abbey & Close (1979) and Holtzclaw (1998), utilized extensive temperature and electromyographic measurements to further support the effectiveness of “wrapping” the extremities. The theoretical perspective was based on Abbey’s original work.
In summary, insulation dampens the neurosensory stimulus of heat loss from dominant sensors, while larger but less thermosensitive areas of the trunk allow for heat exchange without triggering shivering.
Historical Cases of Shivering in Healthcare
Historically, interest in postoperative shivering increased in the mid-1980s with the rise of hypothermic cardiac surgery. Research findings indicated a hazardous increase in oxygen consumption, carbon dioxide production, and cardiovascular exertion during postoperative rewarming from hypothermic cardiac bypass (Holtzclaw & Geer, 1986; Phillips, 1997).
Clinical predictors of shivering became important as early prevention was necessary. The mandibular hum was identified by palpating referred masseter vibrations over the jaw ridge (Holtzclaw & Geer, 1994). An increase in the temperature gradient between the skin and core body temperature was found to predict shivering in this population, likely reflecting the discrepancy between the hypothalamic set point and peripheral temperatures that initiate shivering.
Sund-Levander and Wahren (2000) discovered that tympanic temperature gradients predicted shivering in neurologically injured patients during hypothermic surface cooling. They also found that patients were more likely to shiver if cooled too rapidly. This study supported Abbey’s (1973) earlier assertion that shivering during surface cooling could be mitigated by adjusting the rate of body heat loss.
Studies have confirmed that there is little difference between pharmacologic suppressants, warmed blankets, or reflective wraps in preventing shivering during perioperative rewarming (Hershey, Valenciano, & Bookbinder, 1997). However, newer forced-air warming devices (e.g., Bair Hugger) and radiant lamps have been shown in medical studies to maintain normothermia more effectively.
Extremity wraps have been found to effectively reduce the severity and duration of febrile shivering in immunosuppressed cancer patients and individuals with HIV/AIDS (Holtzclaw, 1990, 1998).
Neuroregulatory and Immunological Evidence About Shivering
As scientific understanding of neuroregulatory and immunological factors influencing shivering expands, new research avenues are emerging. Little is known about how to control shivering in emergency situations during rescue and evacuation, and few studies have examined shivering outcomes among children.
Surgery, trauma, circulatory bypass, and hypothermia have all been linked in preliminary studies to acute phase reactions that stimulate febrile shivering (Phillips, RA, 1999). While shivering is common during the final stage of labor, its origins and management have received limited attention.
Future research directions in the study of shivering by nursing professionals will likely explore the biobehavioral interface of environmental stimuli, biochemical and neurotransmitter activity, energy expenditure, heat exchange physics, and thermal comfort.