Hypovolemic shock is a life-threatening condition that results when you lose more than 15 percent of your body’s blood or fluid supply and your heart function is impaired. About 50% to 60% of your body consists of fluid. It can occur due to any type of fluid loss, for example, as a result of dehydration or diarrhea. It occurs when you don’t have enough fluid (blood) volume circulating in your body. A low volume of fluid could include water, blood (plasma) in your circulatory system and/or lymphatic fluid. Lymphatic fluid is a liquid substance full of white blood cells that helps remove toxins and waste from your body.
Hypovolemic shock occurs in stages, and the symptoms may change as the condition progresses.
The stages of the condition includes –
▪︎ Class 1
At this stage, you would be losing less than 15 percent of your blood volume, which is about 750 milliliters (mL).
Your blood pressure and breathing will still appear normal, but you may begin to suddenly feel anxious and your skin may look pale.
▪︎ Class 2
The blood volume loss in this stage ranges between 15 and 30 percent, which is typically 750 to 1,500 mL. Your heart rate and breathing may get faster. Your blood pulse pressure may narrow. Your systolic blood pressure (the top number in a blood pressure measurement) may still be normal.
Your blood pressure at the beginning of this stage may still be normal, though the bottom number of the measurement, the diastolic pressure, may be high.
▪︎ Class 3
At this stage, you lose 30 to 40 percent of your blood volume, which is between 1,500 and 2,000 mL. You’ll experience a major drop in your blood pressure and begin to see changes to your mental status.
Your heart rate will rise above 120 beats per minute (bpm), your breathing will become faster, and you’ll see a decrease in the amount you urinate.
▪︎ Class 4
Once you’ve experienced blood volume loss of more than 40 percent, your condition becomes critical. Your pulse pressure will be really low, and your heart will beat faster at more than 120 bpm.
You may experience:
• extremely rapid, shallow breathing
• extremely rapid heart rate
• little or no urine output
• weak pulse
• blue lips and fingernails
• loss of consciousness
Your mental status will be obviously abnormal, and you’ll stop urinating almost completely. You may experience external and internal bleeding from areas in your body.
Sign & Symptoms –
Symptoms of hypovolemia range in severity for each person. Signs of hypovolemia include:
• Dizziness when standing.
• Dry skin and dry mouth.
• Feeling tired (fatigue) or weak.
• Muscle cramps.
• Unable to pee (urinate) or the color of your urine is darker than normal.
Severe symptoms of hypovolemia that could indicate life-threatening hypovolemic shock include:
• Difficulty breathing or fast breathing.
• Excessive sweating.
• Losing consciousness.
• Low blood pressure.
• Low body temperature.
• Pale skin tone or a blue tone to the skin and lips (cyanosis).
The causes of hypovolemia can be characterized into two categories –
• Loss of body sodium and consequent intravascular water (due to impaired reabsorption of salt and water in the tubules of the kidneys)
• Osmotic diuresis: the increase in urine production due to an excess of osmotic (namely glucose and urea) load in the tubules of the kidneys
• Overuse of pharmacologic diuretics
• Impaired response to hormones controlling salt and water balance (see mineralocorticoids)
• Impaired kidney function due to tubular injury or other diseases
Loss of bodily fluids due to:
• Gastrointestinal losses; e.g. vomiting and diarrhea
• Skin losses; e.g. excessive sweating and burns
• Respiratory losses; e.g. hyperventilation (breathing fast)
• Build up of fluid in empty spaces (third spaces) of the body due to:
• Acute pancreatitis
• Intestinal obstruction
• Increase in vascular permeability
• Loss of blood (external or internal bleeding or blood donation)
Hypovolemia v/s hypovolemic shock
Hypovolemia describes a significant loss of fluid from the body.
If you develop hypovolemia, your body first tries to compensate for the volume loss by increasing your heart rate and the strength of heart contractions. It also constricts the peripheral blood vessels, which are vessels outside of the chest or abdomen. Constricting these blood vessels helps preserve blood flow to vital organs, like the brain, heart, and kidneys.
However, when blood volume drops to a level where blood cannot reach the body’s organs, they can no longer function properly. Tissue cannot receive oxygen and nutrients, and waste is not carried away. At this stage, the condition becomes hypovolemic shock.
Complications may include:
• Kidney damage (may require temporary or permanent use of a kidney dialysis machine)
• Brain damage
• Gangrene of arms or legs, sometimes leading to amputation
• Heart attack
• Other organ damage
A physical exam will show signs of shock, including:
• Low blood pressure
• Low body temperature
• Rapid pulse, often weak and thready
Tests that may be done include:
• Blood chemistry, including kidney function tests and those tests looking for evidence of heart muscle damage
• Complete blood count (CBC)
• CT scan, ultrasound, or x-ray of suspected areas
• Echocardiogram – sound wave test of heart structure and function
• Endoscopy – tube placed in the mouth to the stomach (upper endoscopy) or colonoscopy (tube placed through the anus to the large bowel)
• Right heart (Swan-Ganz) catheterization
• Urinary catheterization (tube placed into the bladder to measure urine output)
Because hypovolemia can quickly progress to hypovolemic shock and cause organ damage, prompt treatment for early signs of hypovolemia is critical.
Treatments at this initial stage include:
• Oral rehydration drinks: Doctors may use this treatment in cases of mild hypovolemia.
• Colloid solutions: These are intravenous (IV) fluids that contain complex sugars and proteins.
• Crystalloid solutions: These are IV fluids that contain electrolytes, most often sodium chloride or a mixture of sodium chloride. Other examples include sodium lactate, potassium chloride, or calcium chloride in water.
• Vasopressors: These are medications that constrict blood vessels and increase blood pressure.
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