From the Guidelines
Hypovolemic shock should be diagnosed based on the presence of systolic blood pressure <90 mm Hg for >30 min, or mean BP <60 mm Hg for >30 min, or requirement of vasopressors to maintain systolic BP ≥90 mm Hg or mean BP ≥60 mm Hg, along with signs of hypoperfusion such as decreased mentation, cold extremities, urine output <30 mL/h, and lactate >2 mmol/L, as suggested by the 2022 AHA/ACC/HFSA guideline 1. The diagnosis of hypovolemic shock is crucial in clinical practice, as it requires prompt recognition and management to prevent morbidity and mortality. The criteria for diagnosing hypovolemic shock include both clinical and laboratory findings.
- Clinical findings:
- Hypotension (systolic blood pressure <90 mm Hg for >30 min or mean BP <60 mm Hg for >30 min)
- Requirement of vasopressors to maintain systolic BP ≥90 mm Hg or mean BP ≥60 mm Hg
- Signs of hypoperfusion such as decreased mentation and cold extremities
- Laboratory findings:
- Urine output <30 mL/h
- Lactate >2 mmol/L These criteria are supported by the 2022 AHA/ACC/HFSA guideline, which emphasizes the importance of early recognition and management of hypovolemic shock 1. The European guideline on management of major bleeding and coagulopathy following trauma also highlights the importance of lactate levels in diagnosing and managing hypovolemic shock, as it is an indirect marker of cellular hypoxia 1. However, the management of intra-abdominal infections guidelines suggests that initial resuscitation should be titrated to clinical response and not solely guided by a predetermined protocol, emphasizing the importance of individualized patient care 1. Overall, the diagnosis of hypovolemic shock requires a comprehensive approach, taking into account both clinical and laboratory findings, as well as individualized patient care.
From the Research
Criteria for Diagnosing Hypovolemic Shock
The diagnosis of hypovolemic shock is based on several clinical and physiological criteria, including:
- Decrease in pulse pressure, urine output, urine sodium concentration, alertness, or any increase in urine osmolarity, tachypnea, or tachycardia 2
- Systolic hypotension, oliguria, metabolic acidosis, and a cold clammy skin are late signs of shock 2
- Hyperventilation, vasoconstriction, cardiac stimulation, fluid shifts into the vascular system, and platelet aggregation are early signs of hypovolemic shock 2
- Lysosomal breakdown, subsequent release of kinins (especially bradykinin), impaired cell metabolism, and organ function, fluid shifts out of the vascular system due to capillary endothelial damage, and intravascular coagulation are late signs of shock 2
Clinical Aspects of Hypovolemic Shock
The clinical aspects of hypovolemic shock include:
- Definition: a pathophysiologic condition produced by rapid and significant loss of intravascular volume, leading sequentially to hemodynamic instability, decreases in oxygen delivery, decreased tissue perfusion, cellular hypoxia, cellular and organ damage, multiple organ dysfunction syndrome (MODS), and may end in death 3
- Pathophysiology: decreased intravascular volume leading to decreased venous return to the heart and decreased stroke volume, resulting in inadequate perfusion and impairment of delivery of nutrients and oxygen to vital end organs 4
- Monitoring: vital signs, hemodynamic and respiratory variables, as well as arterial lactate and colloid osmotic pressure (COP) should be monitored 5
- Diagnosis: early recognition of hypovolemic shock and prompt systematic intervention will help avoid poor outcomes 3
Classification of Hypovolemic Shock
The ATLS(®) classification of hypovolaemic shock is based on vital signs and an estimated blood loss in percent, but there is no clear prospective evidence to fully support this classification, and it may be associated with substantial deficits 6