Postanesthetic shivering (PAS) is
shivering
Shivering (also called shuddering) is a bodily function in response to cold and extreme fear in warm-blooded animals. When the core body temperature drops, the shivering reflex is triggered to maintain homeostasis. Skeletal muscles begin to sha ...
after
anesthesia
Anesthesia (American English) or anaesthesia (British English) is a state of controlled, temporary loss of sensation or awareness that is induced for medical or veterinary purposes. It may include some or all of analgesia (relief from or prev ...
.
Description and treatment
Postanesthetic shivering is one of the leading causes of discomfort in patients recovering from general anesthesia. It usually results due to the anesthetic inhibiting the body's
thermoregulatory capability, although cutaneous
vasodilation
Vasodilation, also known as vasorelaxation, is the widening of blood vessels. It results from relaxation of smooth muscle cells within the vessel walls, in particular in the large veins, large arteries, and smaller arterioles. Blood vessel wa ...
(triggered by post-operative pain) may also be a causative factor. First-line treatment consists of warming the patient; more persistent/severe cases may be treated with medications such as
tramadol
Tramadol, sold under the brand name Tramal among others, is an opioid analgesic, pain medication and a serotonin–norepinephrine reuptake inhibitor (SNRI) used to treat moderately severe pain. When taken by mouth in an immediate-release form ...
,
pethidine
Pethidine, also known as meperidine and sold under the brand name Demerol among others, is a fully synthetic opioid pain medication of the phenylpiperidine class. Synthesized in 1938 as a potential anticholinergic agent by the German chemist Ot ...
,
clonidine
Clonidine, sold under the brand name Catapres among others, is an α2A-adrenergic receptor agonist medication used to treat high blood pressure, attention deficit hyperactivity disorder (ADHD), drug withdrawal (e.g., alcohol, opioids, or nic ...
, and
nefopam, which work by reducing the shivering threshold temperature and reducing the patient's level of discomfort. As these medications may react and/or synergize with the anesthetic agents employed during the surgery, their use is generally avoided when possible. The anesthetic
ketamine
Ketamine is a cyclohexanone-derived general anesthetic and NMDA receptor antagonist with analgesic and hallucinogenic properties, used medically for anesthesia, depression, and pain management. Ketamine exists as its S- (esketamine) a ...
can also be used to manage postanesthetic shivering.
Intensity
The intensity of PAS may be graded using the scale described by Crossley and Mahajan:
:0 = no shivering;
:1 = no visible muscle activity but
piloerection
Goose bumps, goosebumps or goose pimples are the bumps on a person's skin at the base of body hairs which may involuntarily develop when a person is tickled, cold or experiencing strong emotions such as fear, euphoria or sexual arousal.
The f ...
, peripheral
vasoconstriction
Vasoconstriction is the narrowing of the blood vessels resulting from contraction of the muscular wall of the vessels, in particular the large arteries and small arterioles. The process is the opposite of vasodilation, the widening of blood vesse ...
, or both are present (other causes excluded);
:2 = muscular activity in only one muscle group;
:3 = moderate muscular activity in more than one muscle group but no generalized shaking;
:4 = violent muscular activity that involves the whole body.
References
Further reading
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{{Anesthesia
Anesthesia