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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
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Shivering of patients
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Shivering is an involuntary, oscillatory muscular activity that augments metabolic heat production. Vigorous shivering increases metabolic heat production up to 600% above basal level
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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
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a tonic stiffening and appeared to be largely a direct, non–temperature-dependent effect of isoflurane anesthesia.
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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
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C fibres – spinal cord modulation – Nucleus Raphe Magnus and Locus ceruleus ----- preoptic anterior hypothalamus Spinal cord possible recurrent inhibition of renshaw cells Motor activity
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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
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Regional 0.6 * C More with GA
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Does the vasoconstriction cause ischemia ?? Does the vasoconstriction decrease blood flow to the peripheries ?? NO Dormant blood vessels in the forearm
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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
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Cold --- SNS stimulation ---- brown fat --- mitochondrial oxidation ---- uncoupling --- heat production Infants Propofol fentanyl abolishes NST
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Uninhibited spinal reflexes, postoperative pain, pyrogen release, adrenal suppression, respiratory alkalosis
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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.
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0 – no – shivering even in palpation of masseter 1 – shivering neck and thorax 2. – grossly seen includes upper extremities 3 – through out the body
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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
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Shivering increases intraocular and intracranial pressures. Disturbing to mother Reduced in elderly and frail patients
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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.
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OCCCCCO- pneumonic Oxygen, carbon dioxide,comfort, clotting, catecholamines, cardiac,, cranial, ocular
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Management
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prevention
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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
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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.
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biogenic monoamines, Cholino mimetics, cations, endogenous peptides N-methyl-D- aspartate (NMDA) receptor antagonists
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Pharmacological intervention does not raise body temperature, but resets the shivering threshold to a lower level, thereby decreasing rigors and its episodes
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Physostigmine a nonselective centrally acting cholinesterase inhibitor is a potent antishivering drug Availability ??
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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
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morphine (2.5 mg), fentanyl (25 mic g), alfentanil (250 mic. g), Pethidine ( 25 mg)
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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
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Pre induction IV pethidine -- minimal role in a few studies
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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.
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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.
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It is a nonsedative benzoxacine analgesic 0.15 mg/kg IV As effective as clonidine But less effects on hemodynamics
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Excess of Ca2+ into the posterior hypothalamus leads to a decrease in body temperature Magnesium may be considered as physiologic calcium channel blocker
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Magsulf – NMDA antagonism Orphenadrine is both antimuscarinic and has noncompetitive NMDA receptor antagonist properties
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Ketamine, which is a competitive NMDA-receptor antagonist, also inhibits postanaesthetic shivering. 0.25 mg / kg of IV ketamine as prophylaxis
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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
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5 HT antagonism 10 mg IV Effective as 150 mic gm of clonidine Vasodilation also occurs
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Differential recovery of brain and spinal cord Hence doxapram effective against shivering
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4 mg of IV ondansetron Buspirone 60 mg prior 75 mic. gm Clonidine -- best option
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Definition Pathway BSAS Prophylaxis ( hypo and drugs ) Treatment --- opiods, 5 HT, cholinomimetics,NMDA, analeptics,analgesics (Clo and nefo)
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More than 20 references Anybody can shiver when this is the situation
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