Page 501 - Encyclopedia of Nursing Research

468 n ShIVeRIng

Thermal Balance). The shivering center in the measurement of shivering by use of a shiv-
posterior hypothalamus is stimulated, send- ering severity scale, originated by Abbey
S ing impulses via anterior spinal routes of the et al. (1973)
gamma efferent system. heat is generated by Although shivering had been stud-
oscillation and friction of the fibrous muscle ied extensively by physiologists in healthy
spindles of the fusimotor system. Shivering humans and animals, little clinical interest
occurs in fever despite rising temperatures was evident until the 1970s. Abbey and Close
because the set point level is raised to higher (1979) used wraps of ordinary terry-cloth
levels by circulating cytokines and other towels as insulation to protect thermosensi-
pyrogens. The elevated set point range causes tive regions of the skin during use of cooling
the patient’s usual body temperature to be blankets. Shivering during surface cooling
sensed as too cool and causes the warming was a significant problem treated at that time
responses known as shaking febrile chills with chlorpromazine, a drug with undesir-
(holtzclaw, 2002). able side effects. The wrapping intervention
The consequences of shivering for seri- was based on existing physiological research
ously ill or vulnerable patients are some- demonstrating dominance of the heat loss
times overlooked because they seem to be sensors on hands and feet in stimulating
harmless compensatory warming responses. shivering. This landmark pilot study demon-
however, the aerobic activity generated by strated that insulation of extremities controls
vigorous shivering activity raises oxygen shivering and improves comfort without
consumption three- to fivefold, approxi- drugs, even when surface cooling induces
mately that of shoveling snow or riding a hypothermic temperatures.
bicycle. The resulting oxidative phosphory- Federally funded studies by nurse inves-
lation of glucose and fatty acids raises meta- tigators (Abbey & Close, 1979; holtzclaw,
bolic demands, but it is only approximately 1990, 1998) using more extensive tempera-
11% efficient in raising body temperature. ture and electromyographic measurements
The energy expenditure of shivering may further supported the usefulness of “wrap-
be tolerated by healthy persons who shiver ping” extremities, with theoretical perspec-
for short periods, but it puts specific patient tive based on Abbey’s original work. Stated
groups at risk for cardiorespiratory, meta- briefly, insulation blunts the neurosensory
bolic, and thermal instability. Uncontrollable stimulus of heat loss from dominant sen-
shivering is distressful to patients, yet sors, whereas larger but less thermosensitive
it occurs frequently in situations where regions of the trunk allow heat exchange
ambient temperatures are cool, patients without inducing shivering.
are exposed, or therapies induce fever. historically, interest in postoperative
Shivering is often recalled by patients as a shivering grew in the mid-1980s with the rise
negative aspect of postoperative recovery, in hypothermic cardiac surgery. Research
childbirth, antifungal drug administration, findings show the hazardous increase in
blood transfusions, or other hospital experi- oxygen consumption, carbon dioxide pro-
ence. nursing research has documented cor- duction, and cardiovascular exertion during
relates and sequelae of shivering in an effort postoperative rewarming from hypother-
to determine adverse consequences in post- mic cardiac bypass (holtzclaw & geer, 1995;
operative care, febrile illness, and during phillips, 1997). Clinical predictors of shiver-
induced hypothermia. Intervention studies ing became of interest as early prevention was
have tested efficacy of nursing measures to indicated. The mandibular hum was detected
prevent shivering during surface cooling by palpation of referred masseter vibrations
and febrile chills. Important to these stud- over the ridge of the jaw (holtzclaw & geer,
ies has been the effort to standardize the 1986). Widening of skin to core temperature