ACE inhibitors and angiotensin receptor blockers (ARBs) are the blood pressure medications most commonly recommended to be withheld before surgery. The 2024 American College of Cardiology perioperative guidelines advise that patients undergoing elevated-risk surgery should stop these drugs about 24 hours beforehand, primarily because they increase the chance of dangerously low blood pressure while you are under anesthesia. The picture for other classes of blood pressure medications is quite different, and in some cases stopping them is itself the dangerous choice.
Why ACE Inhibitors and ARBs Are Withheld
ACE inhibitors (names ending in “-pril,” like lisinopril and enalapril) and ARBs (names ending in “-sartan,” like losartan and valsartan) lower blood pressure by blocking the renin-angiotensin system, which is one of the body’s main tools for keeping blood vessels constricted and maintaining pressure. General anesthesia already tends to drop your blood pressure. When the renin-angiotensin system is also blocked, the anesthesia team loses one of its biggest levers for keeping pressure stable during the operation.
A large observational study of nearly 4,800 patients found that those who withheld their ACE inhibitor or ARB in the 24 hours before noncardiac surgery had a lower rate of the combined outcome of death, stroke, or heart muscle injury (about 12% versus roughly 13% in those who continued), and significantly less intraoperative hypotension.1Anesthesiology. Withholding versus Continuing Angiotensin-converting Enzyme Inhibitors or Angiotensin II Receptor Blockers before Noncardiac Surgery An updated meta-analysis pooling only randomized controlled trials confirmed the intraoperative-hypotension finding: withholding these drugs reduced it by about 18%.2PubMed Central. Stopping versus continuing renin-angiotensin system inhibitors before surgery: An updated systematic review and meta-analysis of randomised controlled trials
That same meta-analysis, however, found no statistically significant difference between stopping and continuing when it came to the outcomes patients worry about most: heart attacks, strokes, acute kidney injury, heart failure, or death. The benefits of withholding were concentrated in avoiding low blood pressure during the operation itself. Meanwhile, patients who stopped their ACE inhibitor or ARB were somewhat more likely to experience high blood pressure after the procedure.2PubMed Central. Stopping versus continuing renin-angiotensin system inhibitors before surgery: An updated systematic review and meta-analysis of randomised controlled trials So the trade-off is real: less hypotension on the table, potentially more hypertension in the recovery ward.
The Heart Failure Exception
Not everyone on an ACE inhibitor or ARB should stop before surgery. The ACC 2024 perioperative guidelines carve out a specific exception: patients who have heart failure with a reduced pumping function should continue their medication regimen through surgery.3Cardiology in Review. Continuation Versus Discontinuation of Angiotensin-Converting Enzyme Inhibitors and Angiotensin Receptor Blockers in Patients Undergoing Noncardiac Surgery In these patients, the drugs are doing more than controlling blood pressure. They are supporting a weakened heart, and yanking that support away before the stress of surgery can be worse than the risk of low blood pressure during anesthesia.
This distinction matters because a surprising number of people take ACE inhibitors or ARBs for reasons beyond hypertension. If you take one for kidney protection in diabetes, for example, the calculus may be different from someone taking it purely for blood pressure. The decision to hold or continue should involve your surgeon, anesthesiologist, and the physician who prescribed the medication, rather than a blanket rule applied to everyone.
Acute Kidney Injury and the Conflicting Evidence
One concern that has driven interest in withholding ACE inhibitors and ARBs is acute kidney injury after surgery. An analysis of cardiovascular surgery patients found that preoperative use of these drugs was independently associated with a roughly 28% higher risk of developing kidney problems after the operation.4PubMed Central. Preoperative use of angiotensin-converting enzyme inhibitors/angiotensin receptor blockers is associated with increased risk for acute kidney injury after cardiovascular surgery That finding was specific to cardiac and vascular surgery, where the kidneys face particular stress from bypass circuits and fluctuating blood flow.
For major noncardiac surgery, the link is less clear. A prospective study of nearly 950 patients undergoing elective noncardiac procedures found no difference in kidney injury rates between those who continued their ACE inhibitor or ARB and those who stopped it: about 18% in both groups.5PubMed. Association between peri-operative angiotensin-converting enzyme inhibitors and angiotensin-2 receptor blockers and acute kidney injury in major elective non-cardiac surgery: a multicentre, prospective cohort study This inconsistency explains why guidelines recommend withholding before “elevated-risk” procedures rather than before every minor operation. The type of surgery, your kidney function going in, and how long you are under anesthesia all shape the real-world risk.
Beta-Blockers Should Not Be Stopped
If ACE inhibitors and ARBs are the medications your surgical team is most likely to pause, beta-blockers are the ones they most want you to keep taking. The danger of abruptly stopping a beta-blocker has been recognized since the 1970s, and the perioperative setting makes the risk especially acute.6PubMed Central. Beta-blocker withdrawal among patients presenting for surgery from home When you have been on a beta-blocker regularly, your body compensates by becoming more sensitive to adrenaline. Remove the drug suddenly and that heightened sensitivity is left unchecked, resulting in a rebound surge of heart rate and blood pressure at exactly the moment your cardiovascular system is already under surgical stress.
In one study of vascular surgery patients, those who had their beta-blocker discontinued before surgery had dramatically higher cardiovascular mortality and a greatly increased rate of heart attacks.7PubMed. Perioperative beta-blocker withdrawal and mortality in vascular surgical patients The message is unambiguous: if you are already taking a beta-blocker such as metoprolol, atenolol, or carvedilol, continue it through surgery, including on the morning of the procedure with a small sip of water.
A separate but related question is whether patients who are not already on a beta-blocker should be started on one right before surgery to protect the heart. A systematic review for the ACC/AHA guidelines found that starting a beta-blocker within a day of noncardiac surgery did reduce nonfatal heart attacks, but it also increased the risk of stroke, dangerously low blood pressure, and slow heart rate. In trials other than one disputed set of studies, it was even associated with higher overall death rates.8PubMed. Perioperative beta blockade in noncardiac surgery: a systematic review for the 2014 ACC/AHA guideline The takeaway is that continuing an existing beta-blocker is protective, but starting one at the last minute can do more harm than good.
Calcium Channel Blockers Are Generally Continued
Calcium channel blockers like amlodipine, nifedipine, and diltiazem occupy a middle ground. A consensus statement from perioperative-medicine specialists recommends continuing them on the morning of surgery.9Mayo Clinic Proceedings. Preoperative Management of Cardiovascular Medications: Society for Perioperative Assessment and Quality Improvement (SPAQI) Consensus Statement One reason is that calcium channel blockers do not typically cause a withdrawal syndrome when stopped abruptly, so there is less urgency around continuity than with beta-blockers. But continuing them provides stable blood pressure control and may reduce heart rhythm disturbances during noncardiac surgery.
There is a theoretical concern that some calcium channel blockers can mildly inhibit platelet function, which could contribute to increased bleeding. One review noted that this effect exists but concluded the benefits of blood pressure control outweigh the risk.10Cardiovascular Prevention and Pharmacotherapy. Perioperative Management of Hypertensive Patients In patients undergoing coronary revascularization, abrupt discontinuation of calcium channel blockers has been linked to severe vasospasm, which is another reason to keep them on board.9Mayo Clinic Proceedings. Preoperative Management of Cardiovascular Medications: Society for Perioperative Assessment and Quality Improvement (SPAQI) Consensus Statement An anesthesia review similarly advises that both beta-blockers and calcium channel blockers should be taken on the day of surgery.11PubMed. Beta-blockers, calcium channel blockers, angiotensin converting enzyme inhibitors and angiotensin receptor blockers: should they be stopped or not before ambulatory anaesthesia?
Diuretics on the Day of Surgery
Diuretics (“water pills”) like hydrochlorothiazide, furosemide, and spironolactone are commonly held on the morning of surgery, though the rationale is less about cardiovascular catastrophe and more about practical anesthesia management. Diuretics push fluid and electrolytes out of the body through the kidneys. Taking one right before a procedure in which you are already fasting and potentially losing fluid creates a setup for dehydration and electrolyte imbalances, both of which make anesthesia trickier. A consensus statement from perioperative assessment specialists identified loop diuretics, thiazide diuretics, and potassium-sparing diuretics as distinct medication classes requiring specific preoperative management.9Mayo Clinic Proceedings. Preoperative Management of Cardiovascular Medications: Society for Perioperative Assessment and Quality Improvement (SPAQI) Consensus Statement In most routine surgical settings, diuretics are skipped the morning of surgery and resumed once you are eating, drinking, and hemodynamically stable.
An important exception applies to patients who take diuretics for heart failure rather than plain hypertension. If furosemide is the main thing keeping fluid from building up in your lungs, skipping it on the morning of surgery needs to be a joint decision with the anesthesia team rather than an automatic hold. The lines between “blood pressure pill” and “heart failure pill” often blur, since the same drug can serve both purposes depending on the patient.
A Quick Reference by Drug Class
Because many people take more than one blood pressure medication, a summary by class helps keep the different rules straight:
- ACE inhibitors and ARBs: Typically withheld 24 hours before elevated-risk surgery to reduce intraoperative hypotension. Exception for heart failure with reduced ejection fraction.
- Beta-blockers: Continue through surgery, including on the morning of the procedure. Abrupt withdrawal is dangerous.
- Calcium channel blockers: Continue on the morning of surgery. Stable hemodynamic benefits outweigh the small theoretical bleeding concern.
- Diuretics: Usually skipped the morning of surgery to avoid dehydration and electrolyte shifts. Discuss exceptions with your care team if you take them for heart failure.
When to Restart Medications After Surgery
Knowing when to stop a medication is only half the conversation. Restarting too early or too late both carry risks. The SPACE trial, a major randomized study of ACE inhibitor and ARB discontinuation before noncardiac surgery, restarted the drugs on the morning of postoperative day two, unless blood pressure was below 90 systolic in the preceding 12 hours, the patient needed blood-pressure-supporting drugs, or acute kidney injury had developed.12European Heart Journal. Discontinuation vs. continuation of renin–angiotensin system inhibition before non-cardiac surgery: the SPACE trial That two-day window has become a common practical benchmark.
A feasibility trial tested a “tight blood pressure control” strategy that delayed restarting all chronic blood pressure medications until the third postoperative day. Interestingly, despite the delay, postoperative blood pressure readings were similar to those in patients who resumed their medications right after surgery.13PubMed. Tight perioperative blood pressure management to reduce complications: a randomised feasibility trial The researchers concluded that aggressively manipulating postoperative blood pressure medications had less impact than expected on pressure control, largely because other factors in the recovery ward, such as pain, fluid status, and stress hormones, dominate blood pressure behavior in the first few days.
For beta-blockers, restarting quickly is essential. Given the withdrawal risks, most teams aim to resume oral beta-blockers as soon as you can take pills by mouth. If you cannot swallow, intravenous alternatives are available.
Patient Instructions Are Not Always Followed
Even when the plan is clear, execution can be spotty. A quality-improvement study analyzed over 600 preoperative medication instructions for ACE inhibitors and ARBs and found that about 72% of instructions were followed overall. The most common instruction was to skip the medication on the morning of surgery, and compliance with that specific direction was around 90%. But when patients were told to skip the evening dose before surgery or stop a week or more in advance, compliance dropped to roughly 79% and lower.14British Journal of Anaesthesia. Improving quality of medication management by investigating compliance to preoperative ACE inhibitor and ARB medication instructions
This gap highlights something practical: the simpler the instruction, the more likely it gets followed. “Skip your lisinopril the morning of surgery” is easier to remember than “Stop your losartan three days beforehand.” If you receive complex or confusing instructions, call the preoperative clinic and confirm. Showing up with the wrong medication on board is a common reason for surgical delays and preventable complications.
Vasoplegic Syndrome and Severe Intraoperative Hypotension
In rare cases, blood pressure drops during surgery in a way that does not respond to standard drugs. This condition, called vasoplegic syndrome, involves the blood vessels essentially losing their ability to constrict, leaving the anesthesia team unable to maintain adequate pressure even with high doses of vasopressors. While vasoplegic syndrome has multiple causes, preoperative ACE inhibitor and ARB use has been identified as a risk factor, particularly in cardiac surgery.15Journal of Clinical Anesthesia. Vasoplegic syndrome: An update on perioperative considerations
When standard treatments fail, methylene blue has emerged as a rescue therapy. In a cohort of cardiac surgery patients who developed vasoplegic syndrome after bypass, methylene blue administration raised mean arterial pressure by about 8 mmHg, with peak response at two hours.16PubMed Central. Methylene Blue for Postcardiopulmonary Bypass Vasoplegic Syndrome: A Cohort Study This is a niche complication that most surgical patients will never encounter, but it is one of the more dramatic reasons that anesthesiologists care so much about which blood pressure drugs you took before arriving at the hospital. Knowing the exact medication list allows the team to anticipate and prepare for these rare but life-threatening scenarios.
Newer Combination Drugs
Sacubitril/valsartan, sold under the brand name Entresto, combines an ARB with a neprilysin inhibitor and is prescribed mainly for heart failure. Because it contains an ARB component, perioperative management follows similar logic to standalone ARBs, but the heart failure indication complicates the decision. A small study of cardiac surgery patients with heart failure found that sacubitril/valsartan improved heart pumping function during the perioperative period without causing kidney problems.17PubMed Central. Application and evaluation of sacubitril/valsartan in patients with cardiac insufficiency during perioperative period of cardiac surgery The SPAQI consensus statement recognized angiotensin receptor-neprilysin inhibitors as a separate drug class requiring its own preoperative management recommendations.9Mayo Clinic Proceedings. Preoperative Management of Cardiovascular Medications: Society for Perioperative Assessment and Quality Improvement (SPAQI) Consensus Statement If you take Entresto, make sure your surgical team knows; default ARB instructions may not account for the heart failure component.
SGLT2 inhibitors like empagliflozin and dapagliflozin are increasingly used for both diabetes and heart failure, and they can also lower blood pressure. These drugs carry their own perioperative considerations, including a risk of a specific type of metabolic crisis. They are generally stopped a few days before surgery, but the reason has more to do with metabolic safety than blood pressure control. The perioperative medication landscape keeps expanding, and newer combination therapies make the “just skip your blood pressure pill” instruction increasingly inadequate as a blanket approach.