Hypovolemic shock is a medical emergency and an advanced form of hypovolemia due to insufficient amounts of blood and/or fluid inside the human body to let the heart pump enough blood to the body. More specifically, hypovolemic shock occurs when there is decreased intravascular volume to the point of cardiovascular compromise. The hypovolemic shock could be due to severe dehydration through a variety of mechanisms or from blood loss.
People with hypovolemic shock have severe hypovolemia with decreased peripheral perfusion. If left untreated, these patients can develop ischemic injury of vital organs, leading to multi-system organ failure.
The first factor to be considered is whether the hypovolemic shock has resulted from hemorrhage or fluid losses, as this will dictate treatment. When etiology of hypovolemic shock has been determined, replacement of blood or fluid loss should be carried out as soon as possible to minimize tissue ischemia. Factors to consider when replacing fluid loss include the rate of fluid replacement and type of fluid to be used.
Trauma is the most common cause of hemorrhagic shock, but causes can span multiple systems. Tachycardia is typically the first abnormal vital sign of hemorrhagic shock. As the body attempts to preserve oxygen delivery to the brain and heart, blood is shunted away from extremities and nonvital organs. This causes cold and mottled extremities with delayed capillary refill. This shunting ultimately leads to worsening acidosis. The "lethal triad" of trauma is acidosis, hypothermia, and coagulopathy. Trauma-induced coagulopathy can occur in the absence of the hemodilution of resuscitation. Damage control resuscitation is based on three principles: permissive hypotension, hemostatic resuscitation, and damage control surgery. Permissive hypotension targets a systolic blood pressure of 90 mmHg accepting suboptimal perfusion to end organs for a limited time to achieve hemostasis.
Patients with volume depletion may complain of thirst, muscle cramps, and/or orthostatic hypotension. Severe hypovolemic shock can result in mesenteric and coronary ischemia that can cause abdominal or chest pain. Agitation, lethargy, or confusion may characterize brain mal-perfusion.
Dry mucous membranes, decreased skin turgor, low jugular venous distention, tachycardia, and hypotension can be seen along with decreased urinary output. Patients in shock can appear cold, clammy, and cyanotic.
Early signs and symptoms comprise tachycardia given rise to by catecholamine release, skin pallor due to vasoconstriction triggered by catecholamine release, hypotension followed by hypovolaemia and perhaps come after myocardial insufficiency, confusion, aggression, drowsiness and coma either caused by cerebral hypoxia or acidosis. Tachypnoea owing to hypoxia and acidosis, general weakness caused by hypoxia and acidosis, thirst induced by hypovolaemia and oliguria caused by reduced perfusion.
Abnormal growing central venous pressure indicates either hypotension or hypovolemia. Tachycardia accompanied by declined urine outflow implies either tension pneumothorax, cardiac tamponade or cardiac failure which is thought secondary to cardiac contusion or ischaemic heart disease. Echocardiography in such case may be helpful to distinguish cardiac failure from other diseases. Cardiac failure manifests a weak contractibility myocardium; treatment with an inotropic drug such as dobutamine may be appropriate.
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