Intraoperative Management Flashcards
Hypothermia temp
<36
Hyperthermia temp
37.5 - 38.3
Causes of hypothermia
- 90% of intraoperative heat loss is transcutaneous
- OR environment (cold room, IV fluids, instruments)
- open wound
Causes of hyperthermia
- Drugs (ex. atropine)
- Blood transfusion reaction
- Infection/sepsis
- Medical disorder (ex. thyrotoxicosis)
- Malignant hyperthemia
- Over-zealous warming efforts
Impact of hypothermia
- Increased risk of wound infections due to impaired immune function
- increases period of hospitalization by delaying healing
- reduces platelet function and impairs activation of coagulation cascade increasing blood loss and transfusion requirements
- triples incidence of VT and morbid cardiac events
- decreases the metabolism of anesthetic agents prolonging post-operative recovery
Which cardiac rhythms can cause pulseless cardiac arrest? Which are shockable and which are non-shockable?
■ shockable: ventricular fibrillation (VF) and ventricular tachycardia (VT)
■ non-shockable: asystole and pulseless electrical activity (PEA)
Key for survival in VF/VT
good early CPR and defibrillation
Key for survival in asystole/PEA
key to survival is good early CPR and exclusion of all reversible causes
Reversible causes of PEA arrest
■ 5 Hs: hypothermia hypovolemia, hypoxia, hydrogen ions (acidosis), hypo/hyperkalemia
■ 5 Ts: tamponade (cardiac), thrombosis (pulmonary), thrombosi (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)
Causes of sinus tachycardia
■ 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
Causes of sinus bradycardia
■ 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. SCh, opioids, edrophonium, neostigmine, halothane, digoxin, β-blockers) ■ high spinal/epidural anesthesia
Concerning types of bradycardia
2nd degree Mobitz type II and 3rd degree heart block, which can both degenerate into asystole
Causes of intraoperative shock and usual presentation
SHOCKED
Sepsis or Spinal shock
■ decreased sympathetic tone
■ hypotension without tachycardia or peripheral vasoconstriction (warm skin)
Hypovolemic/Hemorrhagic
■ most common form of shock, due to decrease in intravascular volume
Obstructive
■ obstruction of blood into or out of the heart
■ increased JVP, distended neck veins, increased systemic vascular resistance, insufficient cardiac output (CO)
■ e.g. tension pneumothorax, cardiac tamponade, pulmonary embolism (and other emboli – i.e. fat, air)
Cardiogenic
■ increased JVP, distended neck veins, increased systemic vascular resistance, decreased CO
■ e.g. myocardial dysfunction, dysrhythmias, ischemia/infarct, cardiomyopathy, acute valvular dysfunction
anaphylactiK
Extra/other
■ transfusion reaction, Addisonian crisis, thyrotoxicosis, hypothyroid, aortocaval syndrome
Drugs
■ vasodilators, high spinal anesthetic interfering with sympathetic outflow
Causes of intraoperative hypertension
- inadequate anesthesia causing pain and anxiety
- pre-existing HTN, coarctation, or preeclampsia
- hypoxemia/hypercarbia
- hypervolemia
- increased intracranial pressure
- full bladder
- drugs (e.g. ephedrine, epinephrine, cocaine, phenylephrine, ketamine) and withdrawal
- allergic/anaphylactic reaction
- hypermetabolic states: malignant hyperthermia, neuroleptic malignant syndrome, serotonin syndrome, thyroid storm, pheochromocytoma
Maintenance fluids composition and calculation
• average healthy adult requires approximately 2500 mL water/d
■ 200 mL/d GI losses
■ 800 mL/d insensible losses (respiration, perspiration)
■ 1500 mL/d urine (beware of renal failure)
• 4:21 rule to calculate maintenance requirements (applies to crystalloids only)
■ 4 mL/kg/h first 10 kg
■ 2 mL/kg/h second 10 kg
■ 1 mL/kg/h for remaining weight >20 kg