12/11/2008 12:59:00 PM
Erika Hubbard, M.D.
UCLA Anesthesia
Shivering in the Postoperative Patient
Introduction
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In homeothermic species, a thermoregulatory system coordinates defenses against
environmental temperature to maintain internal body temperature within a narrow
range, thereby optimizing normal body function
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The primary thermoregulatory control center in mammals is the hypothalamus

Anesthetic induced thermoregulatory impairment and exposure to a cool environment
makes the majority of unwarmed surgical patients hypothermic

Core hypothermia results from redistribution of body heat from core to periphery

Shivering is an important complication of hypothermia

Although it occurs frequently, i.e. after 40-60% of volatile anesthetics, it remains poorly
understood

Shivering is present in about 50% of patients with a core temperature of 35.5 degrees C
and 90% of patients with a core temperature of 34.5 degrees C

Heat loss is normally regulated by cutaneous vasodilation or vasoconstriction, sweating,
and shivering

Shivering is a “last resort” defense that is activated only when behavioral compensations
and maximal arterio-venous shunt vasoconstriction are insufficient to maintain core
temperature

It is an involuntary, oscillatory muscular activity that augment metabolic heat production
up to 600% above basal level
Risk Factors

Incidence appears to be related to duration of surgery and the use of high
concentrations of volatile agent

Three major risk factors for shivering have been identified: young age, endoprosthetic
surgery, core hypothermia
 Age appears to be the most important risk factor
Consequences of Shivering



Can increase oxygen consumption and CO2 production by up to 200%
Has been linked with an increase in adverse myocardial outcomes in high risk patients
Can be intense enough to cause hyperthermia (38-39 C) and a significant metabolic
acidosis

Increases intraocular and intracranial pressures

Increases the risk of incidental trauma, disrupts medical devices, and interferes with
ECG and pulse oximetry monitoring
Prevention and Treatment of Postoperative Shivering

Shivering should be treated by warming the patient and then administering medication
to inhibit it

Treatment providers should not restrict themselves to combating shivering solely with
drugs, as heat recovery will still be slower and the patient will be deprived of an
important defense mechanism against core temperature loss

Studies suggest intraoperative warming is faster than comparable postoperative
warming

Cutaneous heat loss can be decreased by covering the skin; single layer of an insulator
reduces heat loss by 30% (adding additional layers does not proportionately increase
the benefit)


Forced air warming is the most effective available method
Pharmacologic interventions:

opioids (meperidine 25mg, alfentanil 250mcg, fentanyl, morphine)

other centrally acting analgesics (tramadol, nefopam, metamizol)

clonidine 150mcg (alpha 2-agonist)

methylphenidate

doxapram

ketanserin 10mg (5HT-3 antagonist)

magnesium sulfate

Physostigmine (cholinesterase inhibitor)
 Ketamine (NMDA antagonist)
References:
-Barash PG, Cullen BF, Stoelting RK. Clinical Anesthesia; 5th Edition: Lippincott Williams &
Wilkins; 2006, 1400.
-Bhattacharya PK, Bhattacharya L, Jain RK, Agarwal RC. Post Anaesthesia Shivering: A
Review. Indian J. Anaesthesia. 2003; 47 (2): 88-93.
-Eberhart LH et al. Independent Risk Factors for Postoperative Shivering. Anesthesia &
Analgesia. 2005; 101: 1849-57.
-Kranke P et al. Pharmacological Treatment of Postoperative Shivering: A Quantitative
Systematic Review of Randomized Controlled Trials. Anesthesia & Analgesia. 2002; 94: 45360.
-Morgan GE, Mikhail MS, Murray MJ. Clinical Anesthesiology: Lange Medical Books/McGraw
Hill; 2006, 1008-9.
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12/11/2008 12:59:00 PM
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