Shock and multiple trauma

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Shock (inadequate tissue perfusion) and multiple trauma

1. Main therapy is fluid; initial resuscitation is 1-2 L of lactated Ringer’s; if response is inadequate then give PRBCs
2. NOTE: oxygen debt in shock will cause an increase in anaerobic metabolism and thus an increase in lactate; lactate >4 mmol/L requires either slowing down metabolism with sedation or increasing VO2
3. Cardiogenic shock
   1. manifest by hypotension in the face of adequate intravascular volume
   2. initial compensatory response to diminished myocardial contraction is tachycardia that attempts to maintain cardiac output at the expense of increased myocardial oxygen consumption
   3. treatment: manipulate filling pressure, decreasing afterload if necessary with an agent such as nitroprusside, correcting arrhythmias (atrial fibrillation is best controlled with digoxin then cardioversion if necessary; tachyarrhythmias of atrial origin may be controlled with verapamil while proporanolol will slow sinus tachycardia; for ventricular arrhythmia the main treatment is lidocaine) and improving contractility
      1. nitroprusside is metabolized into cyanide when the ferrous ion reacts with sulfhydryl containing compounds in the red blood cells; cyanide is then reduced to thiocyanate in the liver
      2. with prolonged administration of nitroprusside, thiocyanate may accumulate and cause an acute toxic psychosis (thiocyanate is eliminated in the urine)
   4. dopamine may be used in life threatening hypotension
   5. intraaortic balloon pump may be used to elevate diastolic blood pressure which increases pulmonary perfusion while decreasing myocardial work