Shock

Shock

Shock: is acute circulatory failure resulting in inadequate organ perfusion and cellular hypoxia. It includes several subgroups with distinct etiologies and impaired cardiovascular function. The ultimate result of shock due to any cause is cellular hypoxia and deranged cell function.


Shock classified in to different types depending on the cause of shock.
• Hypovolaemic shock
• Cardiogenic shock
• Anaphylactic shock
• Septic shock
. Neurogenic shock

Hypovolaemic shock
In hypovolaemic shock, circulating blood volume is reduced and venous return to the right atrium falls and therefore stroke volume and cardiac output are reduced. Hypovolaemia may result due to blood loss or fluid loss. Blood loss may revealed as external bleeding or may be concealed (eg: retroperitoneal bleeding, bleeding in to the pelvic cavity in pelvic fracture). Fluid loss can be exogenous as it occurs in burns, diarrhea and diuresis or endogenous where fluid is lost in to the body cavities (eg: intestinal obstruction, peritonitis).

Septic shock
In septic shock, the presence of sever infection triggers a massive inflammatory response with systemic activation of leucocytes and release of a variety of potentially damaging mediators. Common sources of sepsis include abdomen, chest, wounds, urinary tract and intravascular line.

Anaphylactic shock
It is due to anaphylactic reaction, which mediated by immunoglobulin E (IgE) antibodies. Activation of mast cells causes release of histamine and serotonin.
Clinical features of anaphylactic shock
Cutaneous: Flushing, erythema, urticarial rashes and swelling
Respiratory: Bronchospasm, edema of the glottis and tongue result in airway Obstruction.
GIT: Abdominal pain, diarrhea, nausea or vomiting.
CVS: Hypotension, tachycardia and cardiovascular collapse.




Management of shock
• Stop the cause if possible.
• Call for help
• ABC approach
Airway: 100% oxygen or high concentration oxygen should be administered.
Circulation: Venous access should be secured using wide bore i.v. cannula and start fluid replacement including a liter of crystalloid or colloid fluids transfused rapidly.
A-Crystalloid solutions, e.g. isotonic saline, Hartmann s, Plasma-Lyte, are immediately effective, but they leave the circulation quickly.
B-Artificial colloidal solutions include dextrans (glucose polymer), gelatin (hydrolysed collagen) and hydroxyethyl starch, remain in the circulation longer.
Drugs: Adrenaline 100mcgs (1 ml of 1: 10,000 epinephrine) should be given intravenously. If i.v. route is not available then 0.5 mg (0.5 ml of 1:1000 epinephrine) should be given intramuscularly.

• Secondary management includes bronchodilators, antihistamine

Cardiogenic shock
In cardiogenic shock cardiac output falls due to the pathology in the heart itself

Neurogenic Shock
Neurogenic shock caused by the loss of sympathetic control (tone) of resistance vessels, resulting in the massive dilatation of arterioles and venules. Neurogenic shock can be caused by general or spinal anesthesia, spinal cord injury, pain, and anxiety.

Choice of drugs in shock treatment.

On present knowledge, the best drug would be one that both stimulates the myocardium and selectively modifies peripheral resistance to increase flow to vital organs.
• Dobutamine: is used when cardiac inotropic effect is the primary requirement.

• Adrenaline: is used when a more potent inotrope than dobutamine is required, e.g. when the vasodilating action of dobutamine compromises mean arterial pressure.

• Noradrenaline: is used when vasoconstriction is the first priority, plus some slight cardiac inotropic effect, e.g. septic shock