Diagnosis

Hypovolemia

Etiology

Cause [iwf][foe]

1. Renal

   • Diuretic excess

   • Mineralocorticoid deficiency

   • Ketonuria

   • Osmotic diuresis

   • Cerebral salt wasting syndrome

   • Salt-wasting nephropathies

2. Gastrointestinal

   • Vomiting

   • Diarrhea

   • Bowel obstruction (GI secretes 3-6 liters of fluid daily)

   • Stoma/fistula

3. Skin

   • Burns

   • Hot and dry climate

4. Third spaceing

   • Sepsis

   • Pancreatitis

   • Trauma

   • Bleeding (internal hemorrhage, GI bleeding, uterine bleeding)

   • Postoperative phase

   • Anaphylaxis

Pathophysiology [foe]

1. Blood pressure = Cardiac output × systemic vascular resistance

2. Cardiac output = heart rate x stroke volume

3. Classification

   • Mild hypovolemia: 3% to 5% volume loss

   • Moderate hypovolemia: 6% to 9% volume loss

   • Severe hypovolemia: >10% volume loss

4. Hypovolemia: reduced SV --> reduction of CO:

   • Tissue hypoxia

   • Metabolic acidosis

   • Anaerobic metabolism

   • Elevated lactate levels

   • Progressive cellular damage

5. Compensation:

   • Increased SVR (vasoconstriction and redistribution to the brain, heart, and kidneys)

   • Increased heart rate and myocardial contractility

   • Pituitary gland: Antidiuretic hormone --> promotes salt and water resorption

   • Renin --> angiotensinogen --> angiotensin I --> angiotensin II:

     • Vasoconstrictor

     • Stimulate aldosterone --> sodium reabsorption and water conservation

Complications [iwf]

• Shock

• Ischemic stroke

• Myocardial infarction

• Stroke

• Sheehan syndrome

• Liver failure

• Acute Renal failure

• Multi-organ failure

• Death

Epidemiology

Incidence per 100.000 [zqv]

Approach

• Blood test: Hemoglobuline, hematocrit, creatinine, blood urea nitrogen, sodium (Na), potassium (K), glucose

• Urine: Sodium (Na), volume, osmolality

• Blood gas: Lactate, pH

• Weight

• Leg raise

• Ultrasonography: IVC or jugular vein diameter and collapsibility

• CVP

• Volumetric preload parameter: Intrathoracic blood volume index

Treatment

1. Fluid resuscitation [iwf] [foe]

   • Chronic hypovolemia --> gradual resuscitation

   • Excessive fluid resuscitation --> risk of cardiac and pulmonary complications

   • Warm isotonic crystalloid solution of 30 ml/kg infused rapidly

   • If hemorrhagic shock --> Transfusion 1:1:1 of plasma to platelets to RBC

   • Effective resuscitation can be monitored by heart rate, blood pressure, urine output, mental status, and peripheral edema

2. Vasopressor after sufficient volume resuscitation

3. Urinary catheter to measure urine output 

4. Arterial line to measure arterial blood pressure

Differential diagnoses

Abdominal compartment syndrome, Acute liver failure, Acute pancreatitis, Amniotic fluid embolism, Anaphylaxis, Anemia, Aortic regurgitation, Aortic stenosis, Aortoenteric fistula, Arrhythmia, Atrial myxoma, Beriberi, Burn wound, Cardiac contusion, Cardiac tamponade, Cardiomyopathy, Diarrhea, Drug side effects, Fat embolism syndrome, Gastroenteritis, Gastrointestinal hemorrhage, Heart failure, Hemothorax, Hypoaldosteronism, Hypoglycemia, Internal hemorrhage, Myocardial infarction, Myocarditis, Neurogenic shock, Perforated ulcer, Pericarditis, Pneumothorax, Pregnancy, Pulmonary embolism, Pulmonary hypertension, Renal failure, Retroperitoneal hemorrhage, Ruptured aortic aneurysm, Ruptured ectopic pregnancy, Sepsis, Shock, Takotsubo cardiomyopathy, Tension penumothorax, Thyrotoxicosis, Toxic shock syndrome, Trauma