Why ACE Inhibitors Are Sometimes Held Before Anaesthesia

Angiotensin-converting enzyme (ACE) inhibitors are a common class of medications prescribed for high blood pressure, heart failure and certain kidney conditions. Examples include lisinopril, enalapril and ramipril. If you’re scheduled for surgery, your care team may ask you to skip your ACE inhibitor before anesthesia. This recommendation isn’t arbitrary—it’s based on how these drugs interact with anesthesia and blood pressure regulation.

How ACE Inhibitors Work

ACE inhibitors block the enzyme that converts angiotensin I into angiotensin II, a potent hormone that narrows blood vessels. By reducing angiotensin II levels, ACE inhibitors:

• Lower systemic vascular resistance (afterload)
• Promote sodium and water excretion (through reduced aldosterone)
• Help protect the heart and kidneys from chronic stress

While these effects are beneficial in everyday life, they can pose challenges in the controlled environment of the operating room.

The Risk of Intraoperative Hypotension

Anesthesia agents (such as propofol, sevoflurane or spinal anesthetics) also dilate blood vessels and blunt sympathetic nervous system responses. When combined with an active ACE inhibitor:

• Blood vessels relax more than expected
• Cardiac output may drop
• Blood pressure can fall sharply (intraoperative hypotension)

Significant drops in blood pressure during surgery can reduce blood flow to vital organs (brain, heart, kidneys) and increase the risk of complications.

Why Holding ACE Inhibitors Helps

To minimize the risk of severe hypotension under anesthesia, many anesthesiologists recommend holding ACE inhibitors before surgery. The main goals are:

• Allowing angiotensin II levels to partially rebound
• Restoring some capacity for blood vessels to constrict
• Helping maintain stable blood pressure during anesthesia induction

By skipping your usual ACE inhibitor dose (often on the morning of surgery), you give your body a better chance to respond to anesthesia and fluid shifts without a dangerously low blood pressure.

When and How to Stop Your ACE Inhibitor

Guidelines vary slightly depending on the agent’s half-life and your medical history. Common recommendations include:

• Short-acting ACE inhibitors (e.g., captopril):
– Skip the dose on the morning of surgery
• Longer-acting ACE inhibitors (e.g., ramipril, lisinopril):
– Hold the medication for 24 hours before anesthesia
• Renal impairment or heart failure patients:
– Discuss individualized timing with your anesthesiologist or surgeon

Always follow the specific instructions provided by your surgical or anesthesia team.

Balancing Blood Pressure Control and Surgical Safety

While holding an ACE inhibitor reduces intraoperative hypotension risk, it also means temporarily losing its blood pressure–lowering effect. To maintain safe blood pressure control before surgery:

• Monitor blood pressure at home or at your clinic visit
• Discuss possible alternative antihypertensive adjustments (e.g., short-acting calcium channel blockers)
• Ensure adequate hydration (unless you have fluid-restriction orders)

Your care team will weigh the benefits and risks, aiming to optimize both surgical safety and chronic disease management.

Intraoperative Management by the Anesthesia Team

If you arrive on the day of surgery having taken your ACE inhibitor or remain on it despite best efforts, anesthesiologists have strategies to reduce hypotension:

• Intravenous fluid boluses to expand blood volume
• Vasopressors (phenylephrine, ephedrine or norepinephrine) to support blood pressure
• Closer hemodynamic monitoring (arterial lines) in high-risk cases

These measures work, but prevention remains preferable—hence the practice of holding the ACE inhibitor ahead of anesthesia.

Postoperative Considerations

After surgery, once your blood pressure stabilizes and you resume oral intake:

• Your team will decide when to restart your ACE inhibitor
• They’ll ensure you’re hemodynamically stable and not volume-depleted
• Restarting often occurs within 24 to 48 hours postoperatively

Close monitoring after resumption helps detect any swings in blood pressure or kidney function.

What You Can Do Before Your Surgery

1. Review your medication list with your surgeon and anesthesiologist.
2. Confirm exactly when to stop your ACE inhibitor (date and time).
3. Ask about blood pressure checks or alternative medications if you’re concerned.
4. Stay hydrated (unless otherwise instructed).
5. Report any unusual symptoms (dizziness, lightheadedness) in the days before surgery.

Being proactive helps your care team keep you safe and comfortable.

When to Seek Immediate Medical Attention

While skipping a dose of your ACE inhibitor is generally safe for most elective procedures, you should contact a healthcare professional if you experience:

• Severe dizziness or fainting spells
• Chest pain or worsening shortness of breath
• Signs of fluid overload (swelling, rapid weight gain)
• Markedly uncontrolled blood pressure readings

For non-urgent concerns, consider a free, online symptom check, using the doctor approved Ubie Symptom Checker (https://ubiehealth.com/) to help you decide if you need urgent care.

Summary

Holding an ACE inhibitor before anesthesia is a standard precaution to reduce the risk of intraoperative hypotension. By temporarily stopping the drug, you allow your body to better regulate blood pressure under the effects of anesthesia. Your surgical and anesthesia teams will guide you on timing, monitor you closely, and adjust your treatment plan as needed.

Always follow the personalized instructions given by your healthcare providers. If you notice anything concerning before or after surgery, don’t hesitate to seek medical advice. For non-urgent questions or to double-check your symptoms, try the free, online symptom check, using the doctor approved Ubie Symptom Checker (https://ubiehealth.com/). And remember—speak to a doctor about any issues that could be life threatening or serious.