From the Guidelines
Hemodynamic instability is considered a condition where the patient's admission systolic blood pressure is < 90 mmHg with evidence of skin vasoconstriction, altered level of consciousness, and/or shortness of breath, or > 90 mmHg but requiring bolus infusions/transfusions and/or vasopressor drugs, as defined by recent guidelines 1.
Definition and Causes
Hemodynamic instability refers to an abnormal or unstable blood pressure and inadequate blood flow throughout the body, which can lead to organ dysfunction and failure if not promptly addressed. It occurs when the cardiovascular system cannot maintain adequate tissue perfusion, resulting in insufficient oxygen and nutrient delivery to vital organs. Common signs include hypotension (typically systolic blood pressure below 90 mmHg), tachycardia, decreased urine output, altered mental status, cool extremities, and poor capillary refill. Hemodynamic instability can result from various conditions including severe blood loss, sepsis, heart failure, cardiac arrhythmias, anaphylaxis, or neurogenic shock.
Management
Initial management focuses on identifying and treating the underlying cause while simultaneously stabilizing the patient with:
- Intravenous fluids (typically crystalloids like normal saline or lactated Ringer's at 20-30 mL/kg)
- Vasopressors if fluid resuscitation is insufficient (norepinephrine 0.1-1 mcg/kg/min is often first-line)
- Oxygen supplementation Continuous monitoring of vital signs, including blood pressure, heart rate, oxygen saturation, and urine output, is essential during treatment.
Key Considerations
The body normally maintains hemodynamic stability through complex mechanisms involving cardiac output, vascular resistance, and blood volume regulation, so disruption to any of these components can lead to instability. In pediatric patients, hemodynamic stability is considered a systolic blood pressure of 90 mmHg plus twice the child’s age in years, and an acceptable hemodynamic status is considered a positive response to fluid resuscitation 1.
Recent Guidelines
Recent guidelines emphasize the importance of early recognition and management of hemodynamic instability, and provide specific definitions and criteria for diagnosis and treatment 1. These guidelines highlight the need for a multidisciplinary approach to managing hemodynamic instability, and emphasize the importance of continuous monitoring and adjustment of treatment as needed.
From the Research
Definition of Hemodynamic Instability
Hemodynamic instability refers to a state of inadequate blood flow and oxygen delivery to vital organs, which can lead to organ dysfunction and failure. This condition is often characterized by hypotension, decreased cardiac output, and impaired tissue perfusion.
Causes of Hemodynamic Instability
- Hypovolemia, which is a decrease in blood volume, is a principal defect contributing to cardiovascular instability and circulatory failure during septic shock 2.
- Septic shock, which is a life-threatening condition that occurs when the body's response to an infection becomes uncontrolled and causes widespread inflammation 3, 4.
- Vasopressor withdrawal, which can lead to hypotension and hemodynamic instability in patients with septic shock 5.
Characteristics of Hemodynamic Instability
- Hypotension, which is defined as a mean arterial pressure (MAP) less than 60 mmHg 5.
- Decreased cardiac output, which can lead to impaired tissue perfusion and organ dysfunction 4.
- Fluid bolus administration, which is often required to maintain adequate blood pressure and perfusion 5.
- Increased requirements for vasopressors, such as norepinephrine, to maintain adequate blood pressure 5.
Management of Hemodynamic Instability
- Fluid resuscitation, which is the mainstay of initial resuscitation in patients with septic shock 2.
- Vasopressors, such as norepinephrine, which are used to support mean arterial pressure in patients with septic shock 3, 4.
- Inotropes, which are used to increase cardiac contractility and improve tissue perfusion 4.
- Early enteral nutrition, which can be safely initiated in patients with shock receiving vasopressors, but requires careful consideration of the risks and benefits 6.