Overview

Hypovolaemia is characterised by a decreased volume of circulating blood or fluid in the body. “Hypo” means “less than normal” or “below normal”, while “volaemia” refers to the volume of fluid in the bloodstream. So, hypovolaemia essentially means a lower-than-normal volume of fluid in the bloodstream. Fluids are essential to keep the body's organs functioning. Hypovolemia can lead to organ failure, shock, and even death.

Sepsis is a life-threatening condition that arises from the body's overwhelming response to an infection. This leads to organ dysfunction and potentially septic shock.¹ It is a major cause of morbidity and mortality worldwide, particularly in intensive care units. 

Causes of hypovolaemia

Dehydration

Inadequate fluid intake or excessive fluid loss through sweating, vomiting, or diarrhoea can lead to hypovolaemia. This is a common cause in cases of:² 

• Gastroenteritis 
• Prolonged physical activity without proper hydration

Bleeding

Significant blood loss due to traumatic injury, surgery, or internal bleeding disorders can result in hypovolaemia. This could be related to conditions like:³ 

• Ulcers 
• Haemorrhagic stroke

Burns

Severe burns can cause fluid loss through damaged skin, leading to hypovolaemia.⁴

Kidney disorders

Kidney disorders can impair the body's ability to regulate fluid balance, leading to hypovolaemia.⁵ For example:

• Acute kidney injury 
• Chronic kidney disease 

Endocrine disorders

Hormonal imbalances can affect fluid regulation and contribute to hypovolaemia, such as those seen in:

• Diabetes insipidus
• Addison's disease 

Medications

Certain medications can increase fluid loss and potentially lead to hypovolaemia, such as:⁶

• Diuretics
• Chemotherapy drugs 

Excessive sweating

Participation in intense activities resulting in prolonged perspiration or conditions causing abnormal sweating (hyperhidrosis) can lead to hypovolaemia.

Sepsis

Sepsis is a life-threatening condition caused by the body's dysregulated response to infection. It can lead to hypovolaemia due to increased vascular permeability and fluid loss.⁷

Pathophysiology of hypovolaemia

Hypovolaemia leads to a decrease in circulating blood volume. This can impair tissue perfusion and oxygen delivery to vital organs. The body attempts to compensate for this by activating various mechanisms. This includes increasing the heart rate, constricting blood vessels, and redistributing blood flow to prioritise vital organs. However, if the hypovolaemia is severe or prolonged, these compensatory mechanisms may fail. This can lead to organ dysfunction and shock.

Clinical presentation of hypovolaemia

The clinical presentation of hypovolaemia can vary, depending on the severity and underlying cause.

Common symptoms include:

• Thirst
• Dizziness
• Fatigue
• Weakness
• Increased heart rate (tachycardia)
• Hypotension (low blood pressure)
• Cool, clammy skin 

In severe cases, it presents as:

• Altered mental status
• Oliguria (decreased urine output)
• Pale skin or blue colour on the skin and lips (cyanosis)
• Excessive sweating

Diagnosis of hypovolaemia

The diagnosis of hypovolaemia is based on a combination of clinical assessment, laboratory tests, and imaging studies.

Physical examination findings can include:

• Tachycardia
• Hypotension
• Decreased skin turgor (slow return of skin to its normal position after being pinched between the examiner’s thumb and forefinger)⁸

Laboratory tests can provide additional information about the degree of fluid and electrolyte imbalances, including:

• Haematocrit
• Serum electrolytes
• Blood urea nitrogen (BUN)

Imaging studies may be useful in identifying the underlying cause of hypovolaemia, such as a haemorrhage or fluid shifts, such as 

• Ultrasound scans 
• Computed tomography (CT) scans

Treatment and management of hypovolaemia

The treatment of hypovolaemia involves addressing the underlying cause and restoring intravascular volume. This may include 

• Fluid resuscitation with crystalloid or colloid solutions
• Blood product transfusions in cases of haemorrhage
• Correcting electrolyte imbalances⁹

Fluid resuscitation

This is done using intravenous fluids or oral rehydration solutions, including isotonic solutions like normal saline (0.9% NaCl) or lactated Ringer's solution. These fluids help restore blood volume and electrolyte balance in the body.

Blood transfusion

Blood transfusions may be necessary in cases of significant blood loss.

Wound care

Proper wound management and dressing for burns or injuries can prevent further fluid loss.

Antibiotics

Appropriate antibiotic therapy may be required for sepsis or other infections.

Monitoring

Regular monitoring of vital signs, urine output, and fluid balance allows for the assessment of the effectiveness of treatment and adjusting fluid replacement as needed.

Medication adjustments

Reviewing and adjusting medications that may contribute to fluid loss, such as diuretics, may be necessary.

Kidney disease management

Addressing underlying kidney disorders through appropriate medical treatment and dietary modifications can help regulate fluid balance.

Lifestyle changes

Increasing fluid intake

Adequate hydration is recommended. Fluid intake can be increased by drinking water and other fluids. This can be contraindicated in specific medical conditions.

Dietary modifications

Adjusting the dietary intake of sodium, potassium, and other electrolytes as healthcare professionals recommend is encouraged.

Sepsis

Sepsis is a life-threatening condition that arises from the body's dysregulated response to an infection, leading to organ dysfunction.¹⁰ 

Causes

It can be caused by various types of infections, including bacterial, viral, fungal, or parasitic infections.

Common sources of sepsis include:

• Pneumonia
• Urinary tract infections
• Abdominal infections
• Bloodstream infections

Clinical presentation of sepsis

The clinical presentation of sepsis can vary depending on the severity and the affected organs. Common symptoms include:

• Fever or hypothermia (low body temperature)
• Tachycardia (rapid heart rate)
• Rapid breathing (tachypnea)
• Confusion or altered mental status
• Extreme pain or discomfort
• Decreased urine output
• Signs of organ dysfunction (e.g., hypotension, hypoxaemia)¹⁰

In severe cases, sepsis can progress to septic shock. Septic shock is characterised by persistent hypotension despite adequate fluid resuscitation. This leads to tissue hypoperfusion and organ failure.

Diagnosis of sepsis

Diagnosing sepsis involves a combination of clinical assessment, laboratory tests, and imaging studies. The diagnostic criteria for sepsis include:¹¹

• Suspected or confirmed infection
• Presence of at least two systemic inflammatory response syndrome (SIRS) criteria 

Examples of SIRS criteria are:

• Fever or hypothermia
• Elevated heart rate
• Rapid breathing
• Abnormal white blood cell count

Possible laboratory tests to be conducted are:

• Complete blood count 
• Inflammatory markers (e.g. C-reactive protein, procalcitonin)
• Organ function tests (e.g. creatinine, liver enzymes)

Imaging studies, such as chest X-rays or CT scans, may be useful in identifying the source of infection.

Treatment and management of sepsis

The treatment of sepsis involves a multifaceted approach. It aims to control the underlying infection, support organ function, and manage complications. Key components of sepsis management include:¹²

• Antimicrobial therapy: Prompt administration of broad-spectrum antibiotics, antiviral, or antifungal agents, depending on the suspected source of infection
• Source control: Surgical or interventional procedures to remove or drain the source of infection, if applicable
• Fluid resuscitation: Intravenous fluids to maintain adequate blood pressure and organ perfusion
• Vasopressors: Medications to support blood pressure if fluids alone are insufficient
• Respiratory support: Oxygen therapy or mechanical ventilation, if necessary
• Supportive care: Management of organ dysfunction, such as renal replacement therapy for kidney failure or insulin for blood sugar control

Complications of sepsis

 Sepsis can lead to various complications, including:⁷

• Acute respiratory distress syndrome (ARDS)
• Disseminated intravascular coagulation (DIC)
• Acute kidney injury
• Septic shock
• Multiple organ dysfunction syndrome (MODS)

Risk factors of sepsis

 Several factors increase the risk of developing sepsis, including:

• Advanced age
• Weakened immune system (e.g. cancer, HIV/AIDS, immunosuppressive medications)
• Chronic medical conditions (e.g. diabetes, kidney or liver disease)
• Recent hospitalisation or invasive procedures
• Presence of indwelling devices (e.g. catheters, ventilators)

Comparison between hypovolaemia and sepsis

Similarities

Both conditions can result from infections or trauma, leading to fluid loss or impaired blood circulation. They can cause a decrease in blood volume and impaired tissue perfusion.

Differences

Hypovolaemia is primarily caused by fluid loss (e.g. dehydration, bleeding, or excessive vomiting/diarrhoea). In contrast, sepsis is a life-threatening condition caused by the body's dysregulated response to an infection.

Hypovolaemia is a state of decreased intravascular volume, whereas sepsis involves a complex systemic inflammatory response.

Clinical features overlap

• Both conditions can present with symptoms like low blood pressure, rapid heart rate, and altered mental status
• They may share signs of poor tissue perfusion, such as cool extremities, decreased urine output, and fatigue
• However, sepsis often involves additional symptoms like fever, chills, and elevated inflammatory markers

Diagnostic challenges

• Differentiating between hypovolaemia and sepsis can be challenging, as their clinical presentations may overlap
• Laboratory tests (e.g. complete blood count, inflammatory markers, blood cultures) and imaging studies may be required to establish the underlying cause

Summary

Hypovolaemia is characterised by a decreased volume of circulating blood or fluid in the body. Sepsis is a life-threatening condition that arises from the body's overwhelming response to an infection. Hypovolaemia and sepsis are both serious conditions that require prompt recognition and appropriate management to prevent adverse outcomes. 

Management includes identifying the underlying cause and treating it accordingly, along with symptomatic treatment, which includes intravenous fluids, blood transfusion, appropriate medications, supportive and respiratory care and surgical intervention if required. Delays in diagnosis and treatment can lead to increased morbidity and mortality.