From the Research
Morphine should typically be held if a patient's systolic blood pressure falls below 90 mmHg or if there is a significant drop from their baseline blood pressure (generally a decrease of 30% or more). This is because morphine can cause vasodilation and suppress the respiratory drive, leading to hypotension, especially in patients who are already volume depleted or hemodynamically unstable 1.
Key Considerations
- Morphine causes vasodilation and can suppress the respiratory drive, which may lead to hypotension, especially in patients who are already volume depleted or hemodynamically unstable.
- If morphine must be administered to a patient with borderline blood pressure, consider using a reduced dose (25-50% of the standard dose), providing intravenous fluids to maintain blood pressure, and closely monitoring vital signs every 15-30 minutes after administration.
- For patients with chronic pain who require opioid therapy but have hypotension, alternative pain management strategies should be considered, such as non-opioid analgesics, regional anesthesia techniques, or opioids with less hemodynamic effects.
- Always reassess the patient's pain and blood pressure after each dose to determine if further adjustments are needed.
Recent Evidence
A recent study published in 2020 found that a low-dose naloxone infusion can decrease the incidence of respiratory depression following intrathecal morphine administration in patients having major hepatopancreaticobiliary surgery, but at the expense of a small increase in postoperative pain 2. Another study published in 2021 discussed the toxicities of opioid analgesics, including respiratory depression, histamine release, hemodynamic changes, hypersensitivity, and serotonin toxicity 3.
Clinical Implications
In clinical practice, it is essential to carefully monitor patients receiving morphine, especially those with borderline blood pressure or other risk factors for hypotension. The optimal definition of hypotension may vary depending on the patient's age, with a systolic blood pressure of 100 mmHg considered hypotensive for patients 20-49 years, 120 mmHg for patients 50-69 years, and 140 mmHg for patients 70 years and older 1.