[4] In treating hypovolemic shock, it is important to determine the cause of the underlying hypovolemia, which may be the result of bleeding or other fluid losses.

[3] The body in hypovolemic shock prioritizes getting oxygen to the brain and heart, which reduces blood flow to nonvital organs and extremities, causing them to grow cold, look mottled, and exhibit delayed capillary refill.

[3] The lack of adequate oxygen delivery ultimately leads to a worsening increase in the acidity of the blood (acidosis).

Severe hypovolemic shock can result in mesenteric and coronary ischemia that can cause abdominal or chest pain.

[4] Early signs and symptoms include tachycardia given rise to by catecholamine release; skin pallor due to vasoconstriction triggered by catecholamine release; hypotension followed by hypovolaemia and perhaps arising after myocardial insufficiency; and confusion, aggression, drowsiness and coma caused by cerebral hypoxia or acidosis.

[3] A substantial amount of blood loss to the point of hemodynamic compromise may occur in the chest, abdomen, or the retroperitoneum.

[3] The sequence of the most-commonly-seen causes that lead to hemorrhagic type of hypovolemic shock is given in order of frequencies: blunt or penetrating trauma including multiple fractures absent from vessel impairment, upper gastrointestinal bleeding e.g., variceal hemorrhage, peptic ulcer., or lower GI bleeding e.g., diverticular, and arteriovenous malformation.

[4] Diuretic therapy and osmotic diuresis from hyperglycemia can lead to excessive renal sodium and volume loss.

[4] Hemorrhagic shock is due to the depletion of intravascular volume through blood loss to the point of being unable to match the tissues' demand for oxygen.

In the latter process, pyruvate is produced and converted to lactic acid to regenerate nicotinamide adenine dinucleotide (NAD+) to maintain some degree of cellular respiration in the absence of oxygen.

As diastolic ventricular filling continues to decline and cardiac output decreases, systolic blood pressure drops.

While prolonging heart and brain function, this also leads to other tissues being further deprived of oxygen causing more lactic acid production and worsening acidosis.

Due to these factors, heart rate and blood pressure responses are extremely variable and, therefore, cannot be relied upon as the sole means of diagnosis.

Hypothermia (less than 34 C) compounds coagulopathy by impairing coagulation and is an independent risk factor for death in hemorrhagic shock.

ED Emergency department, GCS Glasgow coma scale, HR Heart rate, SBP Systolic blood pressure, SI = Shock index.

The American College of Surgeons Advanced Trauma Life Support (ATLS) hemorrhagic shock classification links the amount of blood loss to expected physiologic responses in a healthy 70 kg patient.

Ventilator settings, chest wall compliance, and right-sided heart failure can compromise CVPs accuracy as a measure of volume status.

The accuracy of pulse pressure variation also can be compromised in right heart failure, decreased lung or chest wall compliance, and high respiratory rates.

[4] Physical findings suggestive of volume depletion include dry mucous membranes, decreased skin turgor, and low jugular venous distention.

[3] With a broader understanding of the pathophysiology of hemorrhagic shock, treatment in trauma has expanded from a simple massive transfusion method to a more comprehensive management strategy of "damage control resuscitation".

The aim is to achieve a systolic blood pressure of 90 mmHg in order to maintain tissue perfusion without inducing re-bleeding from recently clotted vessels.

Permissive hypotension is a means of restricting fluid administration until hemorrhage is controlled while accepting a short period of suboptimal end-organ perfusion.

A recent study has shown no significant difference in mortality at 24 hours or 30 days between ratios of 1:1:1 and 1:1:2 of plasma to platelets to packed RBCs.

The CRASH-2 study was a randomized control trial of tranexamic acid versus placebo in trauma has been shown to decrease overall mortality when given in the first three hours of injury.

[3] For patients in hemorrhagic shock, early use of blood products over crystalloid resuscitation results in better outcomes.

Therefore, it is prudent to start with 2 liters of isotonic crystalloid solution infused rapidly as an attempt to quickly restore tissue perfusion.

Fluid repletion can be monitored by measuring blood pressure, urine output, mental status, and peripheral edema.

Crystalloid fluid resuscitation is preferred over colloid solutions for severe volume depletion not due to bleeding.

Some evidence suggests that patients who need large volume resuscitation may have a less renal injury with restrictive chloride strategies and use of balanced crystalloids.

While trauma spans all demographics, it disproportionately affects the young with 40% of injuries occurring in ages 20 to 39 years by one country's account.