What Is Hypovolemic Shock

Overview

A state of shock occurs when there is an inadequate circulation of blood to the organs and peripheral areas (the hands and legs), causing a lack of nutrients such as oxygen, which leads to cell injury that progresses to organ failure and even death.¹ Following are the different types of shocks:¹

Circulatory shock:

Hypovolemic Shock - Hypovolemic shock is defined as an acute (quick) disturbance in the circulation, caused by a major blood volume loss or decrease in blood volume, that causes an imbalance between the oxygen supply and demand in the tissues.² Hypovolemic shock can happen both in and outside the hospital; common causes include- trauma (accidents), surgery, burns, gastrointestinal bleeding, diabetes, and Addison’s crisis.²   

Cardiogenic Shock – Commonly caused by myocardial infarction (heart attack) but can also result from any condition that might cause inadequate cardiac filling (filling of hearts chambers with blood).¹ 

Restrictive or Vasodilatory/Distributive shock – Also called warm shock. It is generally caused by excessive dilation of arteries which results in low blood pressure (hypotension) thus reducing the volume of blood circulated to warm extremities.¹ A common cause of it is septic shock. Septic shocks can be very severe and fatal.³

Anaphylactic shock – Allergic in origin, a common medical emergency and can also be life-threatening due to the risk of rapid progression to respiratory failure.⁴

Burn Shock - Previously classified as a state of hypovolaemia, but more recently it was found to be a more complex process not only affecting the cardiac contractions but also the cardiac output and systemic vascular resistance.⁵

The above discussed different shocks may or may not be accompanied by hypovolemic shock. Hence it is important to know what Hypovolemic Shock is. It is life-threatening and if untreated could lead to irreversible damage to tissues and also death. Knowledge of this condition is also essential as in many cases quick and adequate resuscitation with emergency medicine is mandatory to save lives.²

Stages of hypovolemic shock

In most cases, the deterioration of patients in Hypovolemic shock is continuous and progressive, with natural compensatory mechanisms becoming less effective increasingly.⁶ Thus, the progression from healthy to critically ill patients in hypovolemic shock can be categorised into the following three stages ⁶:

Compensated Shock

(< 1000 ml of blood volume lost⁶)

Also called non-progressive/initial/reversible stage of Hypovolemic shock.In this stage a decrease in blood pressure and cardiac output triggers natural compensatory mechanisms like widespread constriction of blood vessels, fluid conservation by kidneys, and stimulation of the adrenal medulla to redistribute the blood flow; which maintains sufficient tissue perfusion (process of delivering oxygen, nutrients, and other essential substances to the cells of the body through the circulatory system) to the heart, brain, and other vital organs. Adequate intervention at this stage restores fluid loss as the natural compensation initiates a recovery through restoring intravascular volume (amount of blood within the blood vessels of the body) and normalising circulation.Patients typically show increase in heart rate and cool clammy skin.⁶

Progressive decompensated shock

(Blood volume lost - 1000-1500 ml: Mild,1500-2000 ml: Moderate⁶)

This stage may be further complicated by any pre-existing cardiovascular (heart and circulation) or pulmonary (lung) diseases. Progressive inadequate decompensation of the fluid volume causes a pulmonary decrease in perfusion. Simultaneous decrease in tissue perfusion causes tissue ischemia (suffocation) which increases the lactic acid accumulation within cells thus causing further dilatation of blood vessels and blood accumulation in the peripheral circulatory system.Patients typically experience mental confusion and abnormally rapid breathing. Moreover, cardiac and urine output in this stage is also decreased.⁶

Irreversible decompensated shock

(>2000 ml of blood volume lost)

In this severe stage, blood vessels continue dilating and their permeability is increased due to damage to vessel walls which cumulatively increases the imbalance of circulating blood volume. There is a progressive fall in blood pressure and reduced blood flow to the heart that further decreases its function, output, and overall blood flow.Additionally, oxygen exchange in the lungs decreases thus worsening respiratory distress. It causes irreversible damage to vital organs (heart, kidney, and brain) and increased susceptibility to clotting of the blood. In this stage, patients show signs of coma, with progressively worsened heart and kidney function that can gradually progress to multi-organ failure.⁶

Causes of hypovolemic shock

These can be divided into the following two main categories⁷:

Haemorrhagic shock

Hypovolemic shock is referred to as haemorrhagic shock when it is caused by a reduction in the intravascular volume or acute loss of whole blood volume or blood products such as red cell mass or blood plasma alone or as a result of haemorrhage/blood loss.^6,7 It can occur due to external or internal bleeding.² Blood loss following traumatic injury is the most common cause of hemorrhagic shock.⁷ Other causes include gastrointestinal bleeding, bleeding from surgeries or any intervention, and postpartum haemorrhage.⁷

Non haemorrhagic

Unlike haemorrhagic shocks, these are caused due to reduction in the effective intravascular volume that is the result of body fluid loss.⁷ A leading cause is gastrointestinal fluid loss that occurs in the presence of diarrhoea (most commonly seen in children), uncontrolled vomiting, or in external drainage cases.⁷

Urine output is essential in maintaining the fluid-electrolyte balance on a day-to-day basis but sometimes medicine to increase urination and/or increased urination due to high blood sugars can cause excessive fluid and electrolyte loss.⁷ Other causes include excessive fluid loss due to sweating.^7,8 Furthermore, non-hemorrhagic hypovolemic shocks may also occur when intravascular fluid goes into a third space from the interstitial (space between cells) compartment in tissues such as in cases of intestinal obstructions, burns, post surgeries or any condition that might cause a massive to severe inflammatory response.⁷     

Signs and symptoms of hypovolemic shock

Signs and symptoms of hypovolemic shock are acute and more importantly progressive if untreated or unresponsive to treatment.⁶ Following are some common symptoms: ²

• Thirst
• Muscle cramps
• Diaphoresis (Unusually heavy sweating)
• Shortness of breath
• Mental apathy or confusion – seen in severe stages
• Anxiety may be noted in severe stages
• Feeble and weak pulse
• Declining body temperature
• Increasingly paleness of face and cold, clammy skin (Also an early sign)
• Chest pain (may be seen in severe cases of shock due to inadequate blood supply to the heart)
• Lethargy
• Agitated behaviour

Following are some common signs of hypovolemic shock:² 

• Hypotension (low blood pressure) – might also be more prominent with postural change
• Postural dizziness
• Tachycardia (pulse rate/heart rate higher than 100 beats per minute)  
• Atrial fibrillation and high ventricular response (seen commonly in elderly patients)
• Narrow pulse pressure due to decline in systolic blood pressure (worsening is indicative of decreased cardiac output)
• Tachypnoea (abnormal rapid breathing)
• Oliguria/anuria (decrease in urine output)

Depending on the underlying cause there might be secondary signs that might be indicative of hypovolemic shock, like spider naevi, and portal hypertension may indicate gastrointestinal bleeding. Similarly brown discolouration of the oral cavity or palms are signs of Addison’s diseases that can cause hypovolemic shock.²

Management and treatment for hypovolemic shock

Management and treatment of hypovolemic shock vary depending on the underlying cause. Treatment requires attention from medically educated/trained professionals.⁷

Haemorrhagic shock:

Timely fluid resuscitation with early bleeding control is crucial and drastically improves the survival and need for transfusion of blood products.⁷ Bleeding can be controlled by endoscopy, surgery, or interventional radiology. For the shock, transfusion of blood products has proven to be quite successful in resuscitation.⁹ It was also found that a transfusion using a ratio of 1:1:1 or 1:1:2 of plasma to platelets to packed red cells helps in faster control of bleeding.⁷

For severe hemorrhagic shock, clotting medication (like Tranexamic acid) within 1-3 hours of injury, helps control the bleeding and can improve the prognosis.^7,10  This should be under the recommendation of a medical practitioner.

Non hemorrhagic shock:

In milder cases replenishing the fluid and electrolyte balance orally and timely might be beneficial and can be done at home.¹¹ But for moderate to severe cases - I.V. (intravenous) fluid resuscitation may be indicated, and should be started promptly to normalise blood circulation.⁷ This is generally done under the care of a medical professional, by rapidly infusing a warm isotonic crystalloid solution (e.g., isotonic saline or lactated Ringer’s Solution) to restore tissue perfusion quickly.⁷

The patient's response can be monitored by the heart rate, blood pressure, urine output, mental status, and fluid build-up in hands/legs.⁷ Other options include radiological monitoring of major veins (Ultrasonography for IVC compressibility), central venous pressure monitoring and pulse pressure fluctuation.⁷ Vasopressors (Anti low blood pressure medication) should not be used unless in the initial resuscitation phases, since it may worsen the tissue perfusion.⁷ Furthermore, symptom relief and supportive care are provided as needed.^1,7

Diagnosis

​History and physical examination 

 A history of bleeding, trauma or recent surgeries is used to diagnose hemorrhagic shocks.^1,2,7 For non-haemorrhagic shocks, any gastrointestinal/renal issues, open wounds or third spacing is aimed to be identified through history or physical examining methods such as percussion.^2,7 Focus is also on identifying any of the above-discussed signs and symptoms.⁷ Low values of systolic blood pressure or a decrease in pulse pressure are both quite suggestive of hypovolemic shock.²

Shock Index 

Clinical diagnoses may often be difficult in smaller bleeds and hence for improved sensitivity doctors use shock index (heart rate divided by systolic blood pressure).²

Laboratory examination

Laboratory values are helpful in diagnosing and monitoring as they are often abnormal in hypovolemic shock.^1,2,7 In blood tests, Blood Urea Nitrogen (BUN), serum creatinine, haematocrit, and haemoglobin are often not in normal range.⁷ Additionally increased acidosis is also one of the most common findings in blood tests along with an increase or decrease in sodium and potassium levels.⁷ Urinary laboratory examination may often show lower urinary sodium levels and elevated urine osmolality.⁷

Radiography  

Radiographic imaging such as ultrasonography or X-rays etc. might be used quite often to diagnose internal bleeding in the body to help establish a diagnosis of hypovolemic shock.¹²

FAQs

How can I prevent hypovolemic shock

Mild hypovolemic shocks following severe diarrhoea, vomiting or venturing outdoors in warm weather can be prevented by maintaining hydration through frequent sips of water.⁷ Alternatively, oral rehydration solutions or drinks also help in maintaining fluid electrolyte balance.^2,7,11 For severe traumatic injuries seeking emergency medical help at the earliest may help in preventing hemorrhagic shocks.^1,2  

How common is hypovolemic shock

Hypovolemic shock is the second most common type of shock and is the most common type of shock in children caused by diarrhoea (noted more often in children from lower socio-economic backgrounds).^6,2

Who are at risks of hypovolemic shock

Children with prolonged episodes of diarrhoea or vomiting, individuals living in comparatively warmer climates, and any individual at risk or with a moderate to severe internal or external traumatic injury may be at risk for the relevant type of hypovolemic shock.^1,2,7

When should I see a doctor

In case of a serious or major traumatic injury visit the nearest Accident and Emergency Medicine department at the earliest (NHS). In cases of prolonged illness such as diarrhoea, vomiting or in case any of the above discussed symptoms such as unusual amount of sweating is noted, contact the local GP surgery at the earliest (NHS).

Summary

Hypovolemic shock is an acute and possibly life-threatening disturbance in the circulating blood volume that disturbs the critical fluid-electrolyte balance in the body resulting in a reduced flow of oxygen and other nutrients to vital organs.It is caused by loss of blood, blood products or body fluids.^6,7 Typically characterised by three stages which progressively worsen.⁶ Some common signs and symptoms include thirst, shortness of breath, cold and clammy skin, pale face, lethargy, feeble and weak pulse, low blood pressure, increased heart rate and decreased urine output.² While milder cases can be treated at home, most often treatment of hypovolemic shock needs the attention of a medical professional, which if suspected must be sought immediately for early diagnosis and prompt fluid resuscitation.^1,11,7