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 s ...

after

anesthesia Anesthesia 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 prevention of pain), paralysis (muscle relaxation), ...

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 Thermoregulation is the ability of an organism to keep its body temperature within certain boundaries, even when the surrounding temperature is very different. A thermoconforming organism, by contrast, simply adopts the surrounding temperature ...

capability, although cutaneous

vasodilation Vasodilation 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. The process is the opposite of vasoconstriction, ...

(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 Ultram among others, is an opioid pain medication used to treat moderate to moderately severe pain. When taken by mouth in an immediate-release formulation, the onset of pain relief usually begins within an h ...

pethidine Pethidine, also known as meperidine and sold under the brand name Demerol among others, is a synthetic opioid analgesic, pain medication of the phenylpiperidine class. Synthesized in 1938 as a potential anticholinergic agent by the German chemis ...

clonidine Clonidine, sold under the brand name Catapres among others, is an α2-adrenergic agonist medication used to treat high blood pressure, ADHD, drug withdrawal ( alcohol, opioids, or nicotine), menopausal flushing, diarrhea, spasticity, and c ...

, and

nefopam Nefopam, sold under the brand name Acupan among others, is a centrally acting, non-opioid painkilling medication, that is primarily used to treat moderate to severe pain. Nefopam acts in the brain and spinal cord to relieve pain via novel mecha ...

, 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 dissociative anesthetic used medically for induction and maintenance of anesthesia. It is also used as a recreational drug. It is one of the safest anesthetics, as, in contrast with opiates, ether, and propofol, it suppresses ne ...

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 vessel ...

, 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.

Description and treatment

Intensity

References

Further reading