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A12 Anesthesia
Impact of Hypothermia (<36°C)
• Increased risk of wound infections due to impaired immune function
• Increases the period of hospitalization by delaying healing
• Reduces platelet function and impairs activation of coagulation cascade increasing blood loss and transfusion requirements
• Triples the incidence of VT and morbid cardiac events
• Decreases the metabolism of anesthetic agents prolonging post-operative recovery
Intraoperative Management Toronto Notes 2019 Intraoperative Management
Temperature
Causes of Hypothermia (<36 .0oC)
• intraoperativetemperaturelossesarecommon(e.g.90%ofintraoperativeheatlossistranscutaneous), due to:
■ OR environment (cold room, IV fluids, instruments)
■ openwound
• preventwithforcedairwarmingblanketandwarmedIVfluids
Causes of Hyperthermia (>37 .5-38 .3oC)
• drugs(e.g.atropine)
• bloodtransfusionreaction
• infection/sepsis
• medicaldisorder(e.g.thyrotoxicosis)
• malignanthyperthermia(seeUncommonComplications,A28) • over-zealouswarmingefforts
Heart Rate
Cardiac Arrest
• pulselessarrestoccursdueto4cardiacrhythmsdividedintoshockableandnon-shockablerhythms ■ shockable: ventricular fibrillation (VF) and ventricular tachycardia (VT)
■ non-shockable: asystole and pulseless electrical activity (PEA)
• forVF/VT,keytosurvivalisgoodearlyCPRanddefibrillation
• forasystole/PEA,keytosurvivalisgoodearlyCPRandexclusionofallreversiblecauses • reversiblecausesofPEAarrest(5Hsand5Ts)
■ 5 Hs: hypothermia, hypovolemia, hypoxia, hydrogen ions (acidosis), hypo/hyperkalemia
■ 5 Ts: tamponade (cardiac), thrombosis (pulmonary), thrombosis (coronary), tension
pneumothorax, toxins (overdose/poisoning)
■ when a patient sustains a cardiac arrest during anesthesia, it is important to remember that there
are other causes on top the Hs and Ts to consider (i.e. local anesthetic systemic toxicity (LAST),
excessive anesthetic dosing and others)
• formanagementofcardiacarrest,seeAppendices,A30
Intraoperative Tachycardia
• tachycardia=HR>150bpm;dividedintonarrowcomplexsupraventriculartachycardias(SVT)orwide complex tachycardias
• SVT:sinustachycardia,atrialfibrillation/flutter,accessorypathwaymediatedtachycardia,paroxysmal atrial tachycardia
• widecomplextachycardia:VT,SVTwithaberrantconduction
• causesofsinustachycardia
■ shock/hypovolemia/blood loss ■ anxiety/pain/light anesthesia
■ full bladder
■ anemia
■ febrile illness/sepsis
■ drugs (e.g. atropine, cocaine, dopamine, epinephrine, ephedrine, isoflurane, isoproterenol,
pancuronium) and withdrawal
■ Addisonian crisis, hypoglycemia, transfusion reaction, malignant hyperthermia
• formanagementoftachycardia,seeAppendices,A30
Intraoperative Bradycardia
• bradycardia=HR<50bpm;mostconcerningare2nddegree(MobitztypeII)and3rddegreeheart block, which can both degenerate into asystole
• causesofsinusbradycardia
■ increased parasympathetic tone vs. decreased sympathetic tone
■ must rule out hypoxemia
■ arrhythmias (see Cardiology and Cardiac Surgery, C16)
■ baroreceptor reflex due to increased ICP or increased BP
■ vagal reflex (oculocardiac reflex, carotid sinus reflex, airway manipulation)
■ drugs (e.g. suprachoroidal hemorrhage, opioids, edrophonium, neostigmine, halothane, digoxin,
β-blockers)
■ high spinal/epidural anesthesia
• formanagementofbradycardia,seeAppendices,A30