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Postanaesthetic shivering

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					Postanaesthetic shivering
Report by R1 Lan,Cheng-Yen
Department of Anesthesiology ,National Taiwan University Hospital

Case 1
李x伶,36 y/o F,G2P0, pregnancy at 39th gestational weeks with labor pain Denied systemic disease except asthma hx Prenatal care:smooth PE:WNL, vital sign:stable

168cm,55/78kg,ASA:II C/S Vital sign:71,129/42mmHg,98% Epidural anesthesia:2% xylocaine:7% sodium bicarbonate=10:1 15ml

Case 2
曾x蒲,17 y/o M,sudden onset of left chest pain for one day PH:R’t side spontaneous pneumothorax s/p mini-VATS bullectomy and mechanical pleurodesis 94/1/25 PI:acute onset L’t chest pain,progressive,aggravated by movements,dull CXR:L’t side pneumothorax

PE: decreased breath sound over L’t field CBC: WBC:7.15K/uL RBC:5.53M/uL Hb:16g/dL Hct:49.3% MCV:89.2fL Plt:235K/uL BCS: T-bil:2.01mg/dL AST:16U/L BUN:14.4mg/dL Cre:0.9mg/dL Na:140mmol/L K:4.2mmol/L Cl:103mmol/L AC:83mg/dL Ca:2.47mmole/l PT/PTT:12.5/28.7 INR:1.05

173cm,50kg,ASA class:I Vital sign:36.4/110/13,139/74mmHg,100% VATS 35#L’t double lumen, fix:29cm

Induction
Fentanyl:100ug Atropine:0.5mg Pentothol:250mg S.C.C.:80mg Rocuronium:30mg Maintenance:propofol infusion

Case 3
許x鳳,74y/o F,left knee pain and swelling PH: HTN,bilateral OA knee s/p TKR in 2004/8,endometrial ca s/p R/T in 2004/4 PI:painful sensation over left knee on1/8,knee aspiration:yellow,turbid fluid Impression:L’t TKR infection

PE:WNL Lab: WBC:5.62K/uL RBC:3.93M/uL Hb:10.9g/dL Hct:33.3% MCV:89.2fL Plt:298K/uL BCS: T-bil:0.61mg/dL AST:18U/L BUN:12.2mg/dL Cre:0.7mg/dL Na:138mmol/L K:5mmol/L Cl:104mmol/L AC:83mg/dL

160cm,63.5kg,ASA class III Remove L’t TKR Vital sign:97,131/77mmHg,99% Spinal anesthesia:0.5%heavy marcaine 15mg,para T3-4, level:T6 Fentanyl:50ug

Case 4
江x城,63 y/o M,for TUR-BT for tumor restaging PH:BPH,hyperthyroidism,CVA PI:frequency,incomplete emptying,painful urination,nocturia s/pTURP ,patho showed:prostatic adenocarcinoma and urothelial carcinoma,bone scan:susp L-spine meatstasis

PE:DRE showed moderated enlarge,diffuse,stony-like Lab: WBC:7.22K/uL RBC:4.1M/uL Hb:11.6g/dL Plt:256K/uL BCS: T-bil:0.46mg/dL AST:20U/L BUN:11.8mg/dL Cre:0.7mg/dL Na:140mmol/L K:2.9mmol/L Cl:108mmol/L AC:82mg/dL

63kg, 163.4cm,ASA class II Vital sign:37.3,90,119/57mmHg,98% Induction:fentanyl:100ug,propofol infustion

Postanaesthetic shivering

Epidemiology
6.3-66% after GA 33% during epidural anesthesia Young adult,male, length of anaesthesia or surgery,no active perioperative rewarming procedure,anticholinergic premedication Halogenated agent, pentothol,opiates Less common with propofol

Pathophysiology -EMG
Tonic EMG activity Spontaneous EMG clonus Tonic waxing and waning signals

Normal shivering
200Hz Slow,4-8 cycles/min waxing-and-waning pattern

Abnormal tremor pattern

Clonic tremor 5-7Hz Bursting pattern

Pathophysiology –two types
Normal thermoregulatory defense-the most likely cause of postoperative shivering Non-thermoregulatory shivering-not fully known

Non-thermoregulatory shivering-not fully known
Postoperative pain Decreased sympathetic nervous system activity,sympathetic overactivity Administration of anesthetic drugs Loss of descending control Release of endogenous pyrogens Adrenal suppression Respiratory alkalosis

Effect of GA on thermoregulation
Increase interthreshold range to 4 oC Inhalation anesthetic agents Thresholds lowered further in elderly pt by 1 oC

Effect of GA on thermoregulation
Propofol-induced vasodilation Midazolam 0.075mg/kg

Effect of RA on thermoregulation
Decrease thresholds to 0.6 oC Not directly interact with hypothalamic control centers Regional block upon afferent thermal information Core hypothermia after epidural anesthesia

Effect of RA on thermoregulation
Awareness of core hypothermia is impaired Accelerate heat loss Epidural anesthesia+general anesthesia

Consequences
Discomfort,stressful sensation of coldness,increased pain by muscular contraction, impede monitoring Increased O2 consumption (40-120%)and CO2production Catecholamine release Increased CO Tachycardia,HTN Raised intraocular and intracranial pressure Decrease mixed venous oxygen saturation

Prevention
Limit internal redistribution Increase heat content by generating endogenous production Limit radiation and convection on skin IV solution rewarming Respiratory path Active heat transfer

Management
Mainstay of treatment of postoperative shivering is pharmacological

Management-physical treatment
Forced air warmer

Management-medical treatment-opiates
µ-receptor agonists:contradictory Meperidine(pethidine):0.4-0.85mg/kg Postop:plasma meperidine:0.6mg/L>analgesia,lower shivering threshold by 1.6oC Via K-opioid receptors<->nalbuphine, no antishivering effect Non-opiate property:local anaesthetic activity and central anticholinergic action(shivering?)

Meperidine
Decrease shivering threshold twice as vasoconstriction threshold Monoamine reuptake inhibition NMDA receptor antagonist Stimulation of ą2 adrenoceptors

Management-medical treatment-α2-adrenergic agonists
Clonidine 1.5 0r 3µg/kg, bolus injection, stop shivering within 5 mins, 5µg/kg perfusion over 1 hr, no effect As premedication:with clonidine 200-300 µg; with dexmedetomidine 2.5 µg/kg ,reduced postop shivering Strengthen inhibiting control of preoptic anterior hypothalamic region

Management-medical treatment
Ketanserin10mg,ondansetron8mg,trama dol 1 mg/kg,nefopam 0.15mg/kg Inhibition of serotonin re-uptake

Management-medical treatment-other drugs
Methylphenidate 20mg,physostigmine0.04mg/kg,doxapra m 100mg Facilitate recovery of descending inhibitor control of supraspinal effecting centres on spinal centres Megnesium sulfate30mg/kg

Conclusions
Reduce threshold for activation of thermoregulatory effector mechanisms under anesthesia Emergence from anesthesia, normal thresholds are restored,hypothermic pt may shiver Hypothermia remains the most common cause of postoperative shivering

Conclusion
Core temperature monitoring Prevention of hypothermia Discomfort and metabolic stress associated with shivering If shivering occurs:skin surface rewarming,medical treatment:  Meperidine 0.4-0.85mg/kg  Tramadol 1-2mg/kg  Magnesium sulfate 30mg/kg

No single structure of pathway is responsible for mediation of the thermoregularoty shivering response. In contrast, several mechanisms are able to modulate various thermoregulatory responses.

References
Jan De Witte,M.D.,Eaniel l. Sessler,M.D.: Periooperative Shivering -physiology and pharmacology.Anesthesiology 2002;96:467-84 D.J.Buggy and A.W.A. Crossley:Thermoregulation,mild perioperative hypothermia and post-anaesthetic shivering. British Journal of Anaesthesia 2000;84(5):615-28 Pascal Alfonsi:Postanaesthetic Shivering Epidemiology,Pathophysiology,and Approaches to Prevention and Management.Drugs 2001;61(15):2193-2205 Peter MD; Sessler, Daniel I. MD: Non-thermoregulatory Shivering in Patients Recovering from Isoflurane or Desflurane Anesthesia. Anesthesiology 1998; 89(4): 878886


				
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