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Bạn đang xem: Hypovolemia là gì
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StatPearls . Treasure Islvà (FL): StatPearls Publishing; 2021 Jan-.
Continuing Education Activity
Patients with hypovolemic shochồng have severe hypovolemia with decreased peripheral perfusion. If left untreated, these patients can develop ischemic injury of vital organs, leading lớn multi-system organ failure. The first factor to be considered is whether the hypovolemic shoông chồng has resulted from hemorrhage or fluid losses, as this will dictate treatment. When etiology of hypovolemic shoông chồng has been determined, replacement of blood or fluid loss should be carried out as soon as possible khổng lồ minimize tissue ischemia. Factors lớn consider when replacing fluid loss include the rate of fluid replacement and type of fluid khổng lồ be used. This activity nhận xét the causes, pathophysiology và presentation of shochồng và highlights the role of the interprofessional team in its management.
Objectives:Identify the etiology of hypovolemic shock.ReĐiện thoại tư vấn the presentation of hypovolemic shoông xã.List the treatment và management options available for hypovolemic shoông xã.Discuss interprofessional team strategies for improving care coordination và communication lớn advance the treatment of hypovolemic shock và improve sầu outcomes.
Patients with hypovolemic shoông chồng have severe hypovolemia with decreased peripheral perfusion. If left untreated, these patients can develop ischemic injury of vital organs, leading khổng lồ multi-system organ failure. The first factor to be considered is whether the hypovolemic shoông xã has resulted from hemorrhage or fluid losses, as this will dictate treatment. When etiology of hypovolemic shochồng has been determined, replacement of blood or fluid loss should be carried out as soon as possible to minimize tissue ischemia. Factors to lớn consider when replacing fluid loss include the rate of fluid replacement & type of fluid khổng lồ be used.
The annual incidence of shock of any etiology is 0.3 khổng lồ 0.7 per 1000, with hemorrhagic shoông xã being most common in the intensive sầu care unit. Hypovolemic shock is the most common type of shock in children, most commonly due lớn diarrheal illness in the developing world. Hypovolemic shock occurs as a result of either blood loss or extracellular fluid loss. Hemorrhagic shoông chồng is hypovolemic shoông chồng from blood loss. Traumatic injury is by far the most common cause of hemorrhagic shoông xã. Other causes of hemorrhagic shoông xã include gastrointestinal (GI) bleed, bleed from an ectopic pregnancy, bleeding from surgical intervention, or vaginal bleeding.
Hypovolemic shochồng as a result of extracellular fluid loss can be of the following etiologies:
GI losses can occur via many different etiologies. The gastrointestinal tract usually secretes between 3 khổng lồ 6 liters of fluid per day. However, most of this fluid is reabsorbed as only 100 to 200 mL are lost in the stool. Volume depletion occurs when the fluid ordinarily secreted by the GI tract cannot be reabsorbed. This occurs when there is retractable vomiting, diarrhea, or external drainage via stoma or fistulas.
Renal losses of salternative text and fluid can lead to hypovolemic shock. The kidneys usually excrete sodium & water in a manner that matches intake. Diuretic therapy & osmotic diuresis from hyperglycemia can lead to excessive renal sodium và volume loss. In addition, there are several tubular & interstitial diseases beyond the scope of this article that cause severe salt-wasting nephropathy.
Fluid loss also can occur from the skin. In a hot và dry climate, skin fluid losses can be as high as 1 to lớn 2 liters/hour. Patients with a skin barrier interrupted by burns or other skin lesions also can experience large fluid losses that lead khổng lồ hypovolemic shochồng.
Sequestration of fluid into lớn a third-space also can lead to volume loss & hypovolemic shoông xã. Third-spacing of fluid can occur in intestinal obstruction, pancreatitis, obstruction of a major venous system, or any other pathological condition that results in a massive sầu inflammatory response.
While the incidence of hypovolemic shock from extracellular fluid loss is difficult to quantify, it is known that hemorrhagic shoông xã is most commonly due khổng lồ trauma. In one study, 62.2% of massive sầu transfusions at a level 1 trauma center were due to traumatic injury. In this study, 75% of blood products used were related to traumatic injury. Elderly patients are more likely khổng lồ experience hypovolemic shochồng due lớn fluid losses as they have sầu a less physiosúc tích reserve.
Hypovolemic shoông xã results from depletion of intravascular volume, whether by extracellular fluid loss or blood loss. The body compensates with increased sympathetic tone resulting in increased heart rate, increased cardiac contractility, and peripheral vasoconstriction. The first changes in vital signs seen in hypovolemic shoông chồng include an increase in diastolic blood pressure with narrowed pulse pressure. As volume status continues to decrease, systolic blood pressure drops. As a result, oxyren delivery to vital organs is unable to lớn meet oxyren dem&. Cells switch from aerobic metabolism to lớn anaerobic metabolism, resulting in lactic acidosis. As sympathetic drive increases, blood flow is diverted from other organs to lớn preserve sầu blood flow to lớn the heart and brain. This propagates tissue ischemia and worsens lactic acidosis. If not corrected, there will be worsening hemodynamic compromise and, eventually, death.
History and Physical
History và physical can often make the diagnosis of hypovolemic shochồng. For patients with hemorrhagic shock, a history of trauma or recent surgery is present. For hypovolemic shoông chồng due to fluid losses, history & physical should attempt lớn identify possible GI, renal, skin, or third-spacing as a cause of extracellular fluid loss. Symptoms of hypovolemic shoông chồng can be related khổng lồ volume depletion, electrolyte imbalances, or acid-base disorders that accompany hypovolemic shoông chồng.
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Patients with volume depletion may complain of thirst, muscle cramps, and/or orthostatic hypotension. Severe hypovolemic shoông xã can result in mesenteric và coronary ischemia that can cause abdominal or chest pain. Agitation, lethargy, or confusion may result from brain malperfusion.
Although relatively nonsensitive sầu & nonspecific, physical exam can be helpful in determining the presence of hypovolemic shock. Physical findings suggestive sầu of volume depletion include dry mucous membranes, decreased skin turgor, & low jugular venous distention. Tachycardia & hypotension can be seen along with decreased urinary output. Patients in shoông chồng can appear cold, clammy, and cyanotic.
Various laboratory values can be abnormal in hypovolemic shoông chồng. Patients can have sầu increased BUN and serum creatinine as a result of prerenal kidney failure. Hypernatremia or hyponatremia can result, as can hyperkalemia or hypokalemia. Lactic acidosis can result from increased anaerobic metabolism. However, the effect of acid-base balance can be variable as patients with large GI losses can become alkalotic. In cases of hemorrhagic shochồng, hematocrit và hemoglobin can be severely decreased. However, with a reduction in plasma volume, hematocrit and hemoglobin can be increased due to lớn hemoconcentration.
Low urinary sodium is commonly found in hypovolemic patients as the kidneys attempt lớn conserve sodium và water khổng lồ exp& the extracellular volume. However, sodium urine can be low in a euvolemic patient with heart failure, cirrhosis, or nephrotic syndrome. A fractional excretion of sodium under 1% is also suggestive of volume depletion. Elevated urine osmolality can also suggest hypovolemia. However, this number also can be elevated in the setting of impaired concentrating ability by the kidneys.
Central venous pressure (CVP) is often used to lớn assess volume status. However, its usefulness in determining volume responsiveness has recently come into question. Ventilator settings, chest wall compliance, and right-sided heart failure can compromise CVPs accuracy as a measure of volume status. Measurements of pulse pressure variation via various commercial devices has also been postulated as a measure of volume responsiveness. However, pulse pressure variation as a measure of fluid responsiveness is only valid in patients without spontaneous breaths or arrhythmias. The accuracy of pulse pressure variation also can be compromised in right heart failure, decreased lung or chest wall compliance, & high respiratory rates.
Similar lớn examining pulse pressure variation, measuring respiratory variation in inferior vena cava diameter as a measure of volume responsiveness has only been validated in patients without spontaneous breaths or arrhythmias. Measuring the effect of passive sầu leg raises on cardiac contractility by emang lại appears khổng lồ be the most accurate measurement of volume responsiveness, although it is also subject khổng lồ limitations.
Treatment / Management
For patients in hemorrhagic shock, early use of blood products over crystalloid resuscitation results in better outcomes. Balanced transfusion using 1:1:1 or 1:1:2 of plasma to platelets to packed red blood cells results in better hemostasis. Anti-fibrinolytic administration to lớn patients with severe bleed within 3 hours of traumatic injury appears khổng lồ decrease death from major bleed as shown in the CRASH-2 trial. Retìm kiếm on oxygen-carrying substitutes as an alternative sầu to lớn packed red blood cells is ongoing, although no blood substitutes have been approved for use in the United States.
For patients in hypovolemic shoông chồng due to lớn fluid losses, the exact fluid deficit cannot be determined. Therefore, it is prudent khổng lồ start with 2 liters of isotonic crystalloid solution infused rapidly as an attempt to lớn quickly restore tissue perfusion. Fluid repletion can be monitored by measuring blood pressure, urine output, mental status, và peripheral edema. Multiple modalities exist for measuring fluid responsiveness such as ultrasound, central venous pressure monitoring, and pulse pressure fluctuation as described above sầu. In general, for hypovolemic shochồng, vasopressors should not be used because they can worsen tissue perfusion.
Crystalloid fluid resuscitation is preferred over colloid solutions for severe volume depletion not due to lớn bleeding. The type of crystalloid used to lớn resuscitate the patient can be individualized based on the patients’ chemistries, estimated volume of resuscitation, acid/base status, & physician or institutional preferences. Isotonic saline is hyperchloremic relative lớn blood plasma, & resuscitation with large amounts can lead khổng lồ a hyperchloremic metabolic acidosis. Several other isotonic fluids with lower chloride concentrations exist, such as lactated Ringer”s solution or PlasmaLyte. These solutions are often referred to lớn as buffered or balanced crystalloids. Some evidence suggests that patients who need large volume resuscitation may have a less renal injury with restrictive chloride strategies & use of balanced crystalloids. Crystalloid solutions are equally as effective và much less expensive sầu than colloid. Commonly used colloid solutions include those containing albumin or hyperoncotic starch. Studies examining albumin solutions for resuscitation have sầu not shown improved outcomes, while other studies have shown resuscitation with hyperoncotic starch leads to lớn increased mortality và renal failure.