What is the threshold and treatment for hypotension?

From the Guidelines

Hypotension is generally defined as a systolic blood pressure below 90 mmHg or a mean arterial pressure less than 65 mmHg, though the threshold may vary based on a patient's baseline.

Definition and Threshold

The definition of hypotension can vary depending on the patient's baseline blood pressure and underlying medical conditions. However, a commonly accepted threshold for hypotension is a systolic blood pressure below 90 mmHg or a mean arterial pressure less than 65 mmHg 1.

Treatment Approach

Treatment of hypotension depends on the underlying cause and severity. The initial management includes intravenous fluid resuscitation with crystalloids, such as normal saline or lactated Ringer's solution, typically starting with a 500-1000 mL bolus 1. If fluids are insufficient, vasopressors may be added.

Vasopressor Selection

Norepinephrine is recommended as the first-line vasopressor for most cases of hypotension, starting at 0.1-0.5 mcg/kg/min. Vasopressin or epinephrine may be added for refractory hypotension 1. The choice of vasopressor should be based on the patient's underlying condition and the potential side effects of the medication.

Additional Management Strategies

Positioning the patient with legs elevated can temporarily improve venous return. Underlying causes such as bleeding, infection, cardiac dysfunction, or medication effects must be addressed simultaneously. Continuous monitoring of blood pressure, heart rate, urine output, and mental status is essential during treatment.

Importance of Prompt Intervention

Hypotension requires prompt intervention because prolonged low blood pressure reduces tissue perfusion, potentially causing organ damage through inadequate oxygen delivery to vital tissues. A passive leg raise (PLR) test can be useful in detecting whether inadequate preload is contributing to hypotension, and guiding further management 1.

From the FDA Drug Label

Midodrine hydrochloride tablets are indicated for the treatment of symptomatic orthostatic hypotension (OH) Because midodrine hydrochloride tablets can cause marked elevation of supine blood pressure (BP>200 mmHg systolic), it should be used in patients whose lives are considerably impaired despite standard clinical care, including non-pharmacologic treatment (such as support stockings), fluid expansion, and lifestyle alterations

The lowest blood pressure before concern, or the threshold for hypotension treatment, is not explicitly stated in the provided drug labels. However, symptomatic orthostatic hypotension is the indication for midodrine treatment, which implies that the concern is when symptoms such as dizziness, lightheadedness, or unsteadiness occur due to a drop in blood pressure upon standing.

• The exact blood pressure threshold for concern is not provided.
• Treatment with midodrine is considered for patients with symptomatic orthostatic hypotension whose lives are considerably impaired despite standard clinical care 2.

From the Research

Threshold for Hypotension

• The threshold for hypotension is defined as a drop in blood pressure of at least 20mmHg for systolic blood pressure and at least 10mmHg for diastolic blood pressure within 3minutes of standing up 3
• This condition is also known as orthostatic hypotension and is characterized by symptoms such as lightheadedness, dizziness, visual "white-out", weakness, lack of energy, near syncope or even syncope 4

Treatment for Hypotension

• Midodrine, a peripheral alpha-adrenergic agonist, is an effective treatment for orthostatic hypotension and has been shown to increase standing blood pressure and improve symptoms of orthostatism 4, 5, 6
• The goal of therapy is the relief of symptoms and fall prevention, and there is no predefined blood pressure target 3
• Midodrine is well tolerated, with the most commonly reported adverse events being piloerection, pruritus, paraesthesias, urinary retention and chills 5, 6, 7
• Other treatments for hypotension include volume expansion by fludrocortisone and/or a vasopressor agents such as midodrine 3

Blood Pressure Concern

• A blood pressure drop of at least 20mmHg for systolic blood pressure and at least 10mmHg for diastolic blood pressure within 3minutes of standing up is a concern and may require treatment 3
• The lowest blood pressure before concern is not strictly defined, but a drop in blood pressure of this magnitude is generally considered to be a sign of orthostatic hypotension and may require medical attention 3