Dr. S. Parthasarathy MD., DA., DNB, MD (Acu), Dip. Diab. DCA, Dip. Software statistics PhD (physio) Mahatma Gandhi medical college and research institute, puducherry, India

 Shivering of patients

 Shivering is an involuntary, oscillatory muscular activity that augments metabolic heat production.  Vigorous shivering increases metabolic heat production up to 600% above basal level

 Thermoregulatory  The fundamental tremor frequency on the electromyogram in humans is typically near 200 Hz.  This basal frequency is modulated by a slow, 4– 8 cycles/ min, waxing- and-waning pattern

 a tonic stiffening and appeared to be largely a direct, non–temperature-dependent effect of isoflurane anesthesia.

 Thermosensors  Skin ( C ) to hypothalamus  Integration area  Spinal cord  Modulate: NRM( serotonin),NE(LC)  Integration inputs: - PO AH  Efferent pathway  Central descending shivering pathway: PH  Multiple inputs>common efferent signal  Spinal α motor neurons, 6

 C fibres – spinal cord modulation – Nucleus Raphe Magnus and Locus ceruleus preoptic anterior hypothalamus   Spinal cord possible recurrent inhibition of renshaw cells  Motor activity

 Pickering wrote in 1956: “The most effective system for cooling a man is to subject him to anaesthesia”.  mid of 1960’s -- first case of malignant hyperthermia

 Regional  0.6 * C  More with GA

 Does the vasoconstriction cause ischemia ??  Does the vasoconstriction decrease blood flow to the peripheries ??  NO  Dormant blood vessels in the forearm

14  Phase I: 1st hour  Internal redistribution: from center to peripheral  Phase II: 2-4 hours  Heat loss: skin, viscera  Phase III:  Steady-state RARA

 Cold --- SNS stimulation ---- brown fat --- mitochondrial oxidation ---- uncoupling --- heat production  Infants  Propofol fentanyl abolishes NST

 Uninhibited spinal reflexes,  postoperative pain,  pyrogen release,  adrenal suppression,  respiratory alkalosis

 Shivering occurs in approximately 40% of unwarmed patients who are recovering from GA and in about 50% of patients with a core temperature of 35.5 C and in 90% of patients with a core temperature of 34.5 C.

 0 – no – shivering even in palpation of masseter  1 – shivering neck and thorax  2. – grossly seen includes upper extremities  3 – through out the body

 Shivering can double or even triple oxygen consumption and carbon dioxide production  Marked increase in plasma catecholamine  Level  Three times more likely to have adverse myocardial outcomes

 Shivering increases intraocular and intracranial pressures.  Disturbing to mother  Reduced in elderly and frail patients

 Uncomfortable, and some even find the accompanying cold sensation worse than surgical pain.  Increased surgical bleeding, wound infection  may aggravate postoperative pain simply by stretching surgical incisions.

OCCCCCO- pneumonic Oxygen, carbon dioxide,comfort, clotting, catecholamines, cardiac,, cranial, ocular

Management

prevention

 Cutaneous heat loss can be decreased by covering the skin (e.g. with surgical drapes, blankets or plastic bags).  Single covering can decrease heat loss by 30 %  Maintain above 36 as far as possible

 most cases some form of active warming is required to prevent hypothermia  Forced air warming or a combination of forced air warming along with fluid warming is required to maintain normal intra operative and postoperative core temperatures.

 biogenic monoamines,  Cholino mimetics,  cations, endogenous peptides  N-methyl-D- aspartate (NMDA) receptor antagonists

 Pharmacological intervention does not raise body temperature,  but resets the shivering threshold to a lower  level, thereby decreasing rigors and its episodes

 Physostigmine a nonselective centrally acting cholinesterase inhibitor is a potent antishivering drug  Availability ??

 Fentanyl,alfentanyl morphine has got antishivering properties  But pethidine  Twice more effective  The antishivering activity of meperidine may be partially mediated by k- opiod receptors

 morphine (2.5 mg),  fentanyl (25 mic g),  alfentanil (250 mic. g),  Pethidine ( 25 mg)

 Epidurally administered sufentanil in patients produces a dose-dependent decrease in shivering response and body temperature.  Epidural fentanyl also reduced the shivering threshold when added to lidocaine for epidural

 Pre induction IV pethidine -- minimal role in a few studies 

 The effects of nefopam and tramadol at the level of the pons may partially explain their antishivering effect.  In the rat locus coeruleus, tramadol and its main metabolite, O-desmethyl tramadol, reduce neuronal firing rate and hyperpolarize neurons in a concentration-dependent manner.

 Butorphanol had an edge over tramadol in controlling shivering with lower chances  of recurrence,  Both were superior to clonidine for this purpose with an early onset of action.

 It is a nonsedative benzoxacine analgesic  0.15 mg/kg IV  As effective as clonidine  But less effects on hemodynamics

 Excess of Ca2+ into the posterior hypothalamus leads to a decrease in body temperature  Magnesium may be considered as physiologic calcium channel blocker

 Magsulf – NMDA antagonism  Orphenadrine is both antimuscarinic and has noncompetitive NMDA receptor antagonist properties

 Ketamine,  which is a competitive NMDA-receptor antagonist, also inhibits postanaesthetic shivering.  0.25 mg / kg of IV ketamine as prophylaxis

 Methylphenidate is an analeptic agent that binds presynaptic sites on dopamine, nor epinephrine and 5-HT transport complexes, which in turn blocks reuptake of the respective neurotransmitters  10 – 20 mg IV dose

 5 HT antagonism  10 mg IV  Effective as 150 mic gm of clonidine  Vasodilation also occurs

 Differential recovery of brain and spinal cord  Hence doxapram effective against shivering

4 mg of IV ondansetron Buspirone 60 mg prior 75 mic. gm Clonidine -- best option

Definition Pathway BSAS Prophylaxis ( hypo and drugs ) Treatment --- opiods, 5 HT, cholinomimetics,NMDA, analeptics,analgesics (Clo and nefo)

 More than 20 references  Anybody can shiver when this is the situation