Makindo Medical Notes

Acute hypotension is often diagnosed when systemic blood pressure drops below acceptable values. Traditionally, investigations involved invasive techniques, but non-invasive methods are preferred where possible.

About Hypotension

• Hypotension refers to a decrease in systemic blood pressure below the normal range.
• There is no absolute hypotensive threshold, but values below 90/60 mmHg are commonly considered hypotensive.

Physiology

• Blood Pressure = Cardiac Output x Total Peripheral Vascular Resistance
• The mean arterial pressure (MAP) is the average blood pressure during a single cardiac cycle.
• Mean Arterial Pressure = 2/3 Diastolic Pressure + 1/3 Systolic Pressure
• Cardiac Output = Stroke Volume x Heart Rate

Causes of Hypotension

Clinical Features

• Light-headedness, dizziness, or presyncope
• Fainting (syncope), darkening vision, and tinnitus

Possible Investigations

• FBC, U&E, clotting screen
• Group and cross-match 4-6 units of blood if bleeding is suspected
• Amylase, liver function tests (LFTs)
• ECG, chest X-ray (CXR), arterial blood gases (ABG), and lactate
• Blood and urine cultures
• Echocardiogram, troponin
• D-Dimer, CT Pulmonary Angiogram
• Cortisol levels and a short SynACTHen test

Management

• Asymptomatic hypotension does not require aggressive intervention.
• IV fluids are indicated if hypovolemia is present.
• Vasopressor support is recommended if the mean arterial pressure (MAP) is less than 65 mmHg.
• If bleeding is the cause, blood transfusions may be required.
• Sepsis requires early antibiotics and blood cultures.
• In anaphylaxis, IM adrenaline/epinephrine should be administered immediately.
• Steroids can be used in distributive shock (e.g., septic shock).

References

• Hypotension Review