Muscular hyperactivity after general anaesthesia

Abstract

MvsctrzA~ HYPEr~,CrlWTY during recovery from general anaesthesia variously termed "spasticity, .... shivering," and "shakes," has been described by several authors and has been particularly related to halothane. 1~ Several mechanisms have been suggested in explanation including heat loss, t respiratory alkalosis, a early recovery of spinal reflex activity) at~d sympathetic overactivity. 7 The reported incidence varies from 5 per cent to 70 per cent a.s and this suggests that perhaps different phenomena are being described. Having noticed that some patients seemed to show true shivering whilst others showed intense muscular spasticity during emergence from general anaesthesia, this study was designed to try to elucidate whether there were, indeed, two distinct phenomena, what was their incidence, and whether they were specifically i~lated to halothane anaesthesia. Spasticity was defined as sustained muscular hypertonieity most easily observed in jaw, neck and pectoral muscles, flexors of the upper limbs, and extensors and adductors of the lower limbs. Shivering, on the other hand, was a rhythmic contraction of muscle groups with irregular intermittent periods of relaxation.

The effect of prophylactic clonidine on postoperative shivering

“…Besides the discomfort for the patient, shivering can exacerbate postoperative pain and induce complications in patients with coronary artery disease or heart failure by increasing oxygen consumption [I]. Postoperative shivering has been attributed to the following factors: uninhibited spinal reflexes [2], pain [3], decreased sympathetic activity [4], adrenal suppression [5] and thermoregulatory shivering in response to intra-operative hypothermia , no relationship has been demonstrated between axillary temperature and the occurrence of shivering [8]. Postoperative shivering can be treated by skin-surface warming [9], radiant heat application [ 101 or pharmacologically [I I].…”

Relationship of Periodic Movements in Sleep (Nocturnal Myoclonus) and the Babinski Sign

“…The Babinski response has also been observed as a normal and temporary phenomenon in other situations, such as in the newborn where its gradual disappearance parallels myelinization of the pyramidal tracts (9,11). This response is also found normally during recovery from general anesthesia, which is thought to inhibit supraspinal control of the reflex mechanism (12)(13)(14)(15).…”

“…The high incidence of clonus in the present study is indicative of pyramidal tract involvement in PMS, further supporting the contention that the leg movements are related to NREM changes in pyramidal tract function. Moreover, if the response to general anesthesia is considered as a model for understanding varying degrees of pyramidal tract suppression, clonus is found to be the step following the appearance of the Babinski response during recovery from general anesthesia (14,15). This indicates the close association between the two during another type of temporary pyramidal tract suppression.…”

The ankle clonus test is not a clinically useful measure of spinal cord integrity in children

“…Our data show that ankle clonus is likely to be elicited at end-tidal concentrations of isoflurane or sevoflurane that are close to the MAC awake measured during slow emergence. 19 Other investigators 17 have demonstrated a close temporal relationship, during emergence, among onset of clonus, somatic response to pain, and awakening. In our subjects, the mean time from onset of clonus to tracheal extubation was less than five minutes in both groups.…”

“…Ankle clonus is but one of several signs of motor neuron hyperexcitability that have been variously described as "shakes", "spasticity" and "shivering". 17 Both shivering and flexion-induced clonus are large-amplitude involuntary oscillations with similar electromyographic signatures and a relatively consistent frequency range of 5 to 8 Hz. 18 This suggests that a common spinal reflex is responsible for both phenomena.…”