[Circulatory] shock is tissue hypoperfusion, causing cellular injury and tissue dysfunction. Note that circulatory shock is unrelated to the emotional state of shock.

• Hypotension, although note this is a terminal Sx in children
• Tachycardia
• Low urine output
• Confusion
• LOC
• Signs of end organ perfusion

Patient information

What does it look like, when you're in shock? Are you electrifying ?
Shock looks like not enough blood is reaching a tissue. So low blood pressure. Low urine output. The heart will try to compensate by increasing heart rate. There will also be signs because organs aren't getting the blood it needs, such as confusion, loss of conciousness, that sort of thing.

• Hypoperfusion causes cellular damage, which can in turn trigger tissue inflammation, and inhibit perfusion around the body. This causes positive feedback multiplication
• There are 4 stages of shock, which at a cellular level involves oxygen demand becoming greater than oxygen supply. It includes:
  • Initial, where hypoperfusion causes hypoxia. Due to the lack of oxygen, the cells perform lactic acid fermentation. Accumulation of lactate, causes lactic acidosis
  • Compensatory, where the body tries to reverse the condition. Due to acidosis, the Pt will begin to hyperventilate in order to rid the body of CO2. CO2 acidifies blood, so removing it will raise the pH of blood. The baroreceptors in the arteries detect the resulting hypotension, thus cause release of adrenaline and noradrenaline. Although it causes vasoconstriction, it also increases heart rate. The RAAS system is activated, and ADH is released to conserve fludi via the kidneys. These hormones cause vasoconstriction of the kidneys, GI tract, and other organs, to divert blood to the vital organs (heart, lungs, brain). The lack of blood to the renal system causes characteristic low urine production
  • Progressive, where compensatory mechanisms begin to fail. The prolonged vasoconstriction will also cause the vital organs to be compromised due to reduced perfusion
  • Refractory, where vital organs have failed and the shock can no longer be reversed. Brain damage and cell death are occurring, and death will occur imminently

• Hypovolemic shock (see page), the most common type, caused by insufficient circulating volume
• Cardiogenic shock, caused by failure of the heart to pump effectively. It is caused by:
  • Damage to the heart muscle, usually from a large MI
  • Dysrhythmia
  • Cardiomyopathy/myocarditis
  • CHF
  • Cardiac valve problems
• Obstructive shock, due to obstruction of blood flow outside the heart. It is caused by:
  • Cardiac tamponade, where fluid in the pericardium prevents venous return
  • Tension pneumothorax, through increased intrathoracic pressure, prevents venous return
  • PE, the result of a thromboembolic incidence in the blood vessels of the lungs, hinders venous return
  • Aortic stenosis, hinders circulation by obstructing the ventricular outflow tract
• Distributive shock, due to impaired utilization of oxygen, and thus production of energy by the cell. Examples include:
  • Septic shock, the most common cause of disributive shock. It is caused by an overwhelming systemic infection causing vasodilation leading to hypotension. It can be caused by Gram negative bacteria (E coli, Klebsiella pneumoniae), Gram positive bacteria (pneumococci, streptococci), and certain fungi
  • Anaphylactic shock, caused by a severe anaphylactic reaction to an allergen, antigen, drug, or foreign protein, causing the release of histamine which causes widespread vasodilation, leading to hypotension and increased capillary permeability
  • Neurogenic shock, caused by high spinal injuries. It causes bradycardia due to loss of cardiac sympathetic tone, and warm skin due to dilation of the peipheral blood vessels
• Endocrinologic shock, caused by endocrine disturbances, including:
  • Hypothyroidism, in critically ill Pt's, reducing cardiac output, and can lead to hypotension and respiratory insufficient. Considered a form of cardiogenic shock
  • Thyrotoxicosis, may induce a reversible cardiomyopathy. Considered a form of cardiogenic shock
  • Acute adrena linsufficiency, is frequently the result of discontinuing corticosteroid Tx without tapering the dosage. It can also be caused by surgery and intercurrent disease in Pt's on corticosteorid therapy without adjusting dosage to accommodate for increased requirements. Also considered distributive shock
  • Relative adrenal insufficiency, in critically ill Pt's where the present cortisol levels are insufficicent to meet the higher demands. Also considered distributive shock

• Shock index (SI) = Heart rate / Systolic BP. Normally, it is between 0.5-0.8. The higher the index, the greater the suspicion of underlying shock

• Aims of Tx are to achieve:
  • Urine output>0.5mL/kg/hr
  • Central venous pressure of 8-12mmHg
  • Mean arterial pressure of 65-95mmHg
• ABC's, including:
  • Securing the airway by intubation, if necessary to decrease the WOB and for guarding against respiratory arrest
  • Oxygen supplementation
  • IV fluids, aggressively at 20mL/kg in a child. The exception is in hemorrhagic shock where there is penetrating thorax and abdominal injuries, to allow mild hypotension to persist
  • Passive leg raising
  • Administering packed RBC's, if necessary
  • Blood transfusion, if blood loss is severe
• Drugs, including:
  • Vasopressors, if BP doesnt improve w/ fluids. It is not useful in hemorrhagic shock from trauma
  • There is no evidence for activated protein C, and sodium bicarbonate
• Pain relief
• Surgery, to stop bleeding in trauma

• Life threatening condition
• Can result in hypoxemia, or cardiac/respiratory arrest
• Hypovolemic, anaphylactic, and neurognic shock are readily treatable, and respond well to Tx
• Septic shock is a grave condition w/ a mortality rate of 40%
• Prognosis of cardiogenic shock is even worse than septic shock

• One of the most common causes of death for critically ill Pt's
• Hemorrhagic shock occurs in 1% of trauma cases, affecting 33% of Pt's in ICU

• Hypovolemia
• Spinal shock (do NOT confuse)