Page 62 - TNFlipTest

A28 Anesthesia
Uncommon Complications Toronto Notes 2019
Temperature Regulation
• vulnerabletohypothermia
• minimizeheatlossbyuseofwarmingblankets,coveringtheinfant’shead,humidificationofinspired
gases, and warming of infused solutions
Central Nervous System
• MACofhalothaneisincreasedcomparedtotheadult(0.75%adult,1.2%infant,0.87%neonate)
• NMJisimmatureforthefirst4wkoflifeandthusthereisanincreasedsensitivitytonon-depolarizing
relaxants
• parasympatheticsmatureatbirth,sympatheticsmatureat4-6mothusautonomicimbalance
• infantbrainis12%ofbodyweightandreceives34%ofCO(adult:2%bodyweightand14%CO)
Glucose Maintenance
• infants<1yrcanbecomeseriouslyhypoglycemicduringpre-operativefastingandpost-operativelyif feeding is not recommenced as soon as possible
• after1yr,childrenareabletomaintainnormalglucosehomeostasisinexcessof8h
Pharmacology
• higherdoserequirementsbecauseofhigherTBW(75%vs.60%inadults)andgreatervolumeofdistribution • barbiturates/opioidsmorepotentduetogreaterpermeabilityofBBB
• musclerelaxants
■ non-depolarizing
◆ immature NMJ, variable response
■ depolarizing
◆ must pre-treat with atropine or may experience profound bradycardia and/or sinus node arrest
due to PNS > SNS (also dries oral secretions)
◆ more susceptible to arrhythmias, hyperkalemia, rhabdomyolysis, myoglobinemia, masseter
spasm and malignant hyperthermia
Uncommon Complications
Malignant Hyperthermia
• hypermetabolicdisorderofskeletalmuscle
• due to an uncontrolled increase in intracellular Ca2+ (because of an anomaly of the ryanodine receptor
which regulates Ca2+ channel in the sarcoplasmic reticulum of skeletal muscle)
• autosomaldominantinheritance
• incidenceof1-5in100,000,maybeassociatedwithskeletalmuscleabnormalitiessuchasdystrophyor
myopathy
• anestheticdrugstriggeringMHinclude:
■ all inhalational agents except nitrous oxide ■ depolarizing muscle relaxants: SCh
Clinical Picture
• onset:immediateorhoursaftercontactwithtriggeragent ■ increased oxygen consumption
■ increased ETCO2 on capnograph
■ tachycardia/dysrhythmia
■ tachypnea/cyanosis
■ diaphoresis
■ hypertension
■ increased temperature (late sign)
• muscularsymptoms
■ trismus (masseter spasm) common but not specific for MH (occurs in 1% of children given SCh
with halothane anesthesia)
■ tender, swollen muscles due to rhabdomyolysis
■ trunk or total body rigidity
Complications
• coma
• DIC
• rhabdomyolysis
• myoglobinuricrenalfailure/hepaticdysfunction
• electrolyteabnormalities(e.g.hyperkalemia)andsecondaryarrhythmias • ARDS
• pulmonaryedema
• canbefatalifuntreated
Signs of Malignant Hyperthermia
• Unexplained rise in ETCO2
• Increase in minute ventilation • Tachycardia
• Rigidity
• Hyperthermia (late sign)