Lec 2: Shock Flashcards
Induced imbalance between delivery of oxygen and other substrates. Supply is unable to meet demands
Hypoperfusion
When CO falls, systemic vascular resistance increases to maintain level of systemic pressure that is adequate for perfusion of the heart and brain at the expense of other tissues
Autoregulation
Mean Arterial Pressure equation
MAP = 2 diastole + 1 systole/ 3
Metabolic derangements of shock
Disruption in the normal cycles of carbohydrates, proteins and lipid metabolism
Increased protein catabolism
Increased lactate (due to anaerobic metabolism)
Presence of oxygen deprivation enhances hepatic production of glucose (glycogenolysis and gluconeogenesis)
Effects of sympathetic activation
Increased adrenergic output
Decreased vagal capacity
Increased Epinephrine and Norepinephrine secretion
Receptors for the neuroendocrine response during shock
Baroreceptors
Chemoreceptors
Effect of the RAAS
Water and Na retention
K excretion
Constricts vascular smooth muscle and enhances water reabsorption in distal renal tubule
Vasopressin/ ADH
Contributes to the maintenance of intravascular volume by enhancing renal tubular reabsorption of sodium resulting in excretion of low volume, concentrated, sodium-free urine
Aldosterone
Major determinant of tissue perfusion
Cardiac output
3 variables of stroke volume
Preload (ventricular filling)
Afterload (resistance to ventricular contraction)
Myocardial contractility
Most common form of shock
Hypovolemic
Treatment for hypovolemic shock
Rapid re-expansion of circulating intravascular volume (IV- normal saline)
Respiratory support (O2, intubation)
Control ongoing losses
Blood transfusion
Inotropic support (NE, vasopressin, dopamine)
Shock that may caused by inflammatory responses, direct structural injury to the heart chest or head (pericardial tamponade, tension pneumothorax)
Traumatic shock
May be caused by interruption pf sympathetic vasomotor input after a high cervical spinal cord injury
Neurogenic shock
Treatment for hypo-adrenal shock
Dexamethasone (4mg, IV)
Simultaneous volume resuscitation and pressure support
Presence of bacteria in blood, as evidenced by positive blood culture
Bacteremia
Septic shock that lasts for > 1hr and does not respond to fluid or pressor administration
Refractory septic shock
Sepsis with hypotension for at least 1hour despite adequate fluid resuscitation or need for vasopressin to maintain systolic BP >/= 90mmHg or MAP >/= 70mmHg
Septic shock
80% is due to left ventricular failure leading to pulmonary congestion
Cardiogenic shock
Clinical symptom that results from inadequate tissue perfusion
Shock
Criteria for Sepsis
Cardio: Arterial systolic BP ≤ 90mmHg or MAP ≤ 70mmHg
Renal: U/O
