Perioperative Management of Losartan
It is reasonable to continue losartan perioperatively up to and including the morning of surgery, though withholding it 24 hours before surgery is also acceptable based on individual hemodynamic considerations. 1
Guideline-Based Recommendations
The 2014 ACC/AHA perioperative guidelines provide a Class IIa recommendation (Level of Evidence B) stating that continuation of ACE inhibitors or ARBs (including losartan) is reasonable perioperatively 1. This represents moderate-strength evidence supporting either continuation or brief discontinuation based on clinical judgment.
Key Considerations for Continuation vs. Discontinuation
Arguments for Continuation:
- Prevents rebound hypertension and loss of blood pressure control 2
- Reduces risk of cardiovascular events from abrupt withdrawal 2
- Maintains hemodynamic stability in patients with chronic hypertension 1
- No rebound effect documented after losartan withdrawal in pharmacologic studies 3
Arguments for Withholding:
- A 2001 randomized trial demonstrated that patients who continued angiotensin II antagonists (including losartan) on the morning of surgery experienced significantly more hypotensive episodes during anesthetic induction (19/19 patients vs 12/18 patients, p<0.01), longer duration of hypotension (8±7 min vs 3±4 min, p<0.01), and increased vasopressor requirements compared to those who discontinued the drug 24 hours preoperatively 4
- Patients with activated renin-angiotensin systems (volume depletion, high-dose diuretics) are at particular risk for symptomatic hypotension 3
Practical Algorithm
For most patients:
- Continue losartan through the morning of surgery 1
- Ensure adequate preoperative volume status 3
- Have vasopressors readily available during induction 4
Consider withholding 24 hours preoperatively if:
- Patient is volume or salt-depleted 3
- Patient is on high-dose diuretics 3
- Major vascular surgery planned 4
- History of significant intraoperative hypotension 4
Postoperative management:
- Restart losartan as soon as clinically feasible postoperatively once hemodynamically stable 1, 2
- Monitor blood pressure and volume status carefully 2
Pharmacokinetic Rationale
Losartan has a terminal half-life of approximately 2 hours, with its active metabolite E3174 having a half-life of 6-9 hours 3, 5. Peak concentrations occur at 1 hour for losartan and 3-4 hours for the active metabolite 3. If discontinued 24 hours preoperatively, approximately 4-5 half-lives will have elapsed, minimizing residual effect at the time of surgery 4.
Common Pitfalls to Avoid
- Failing to assess volume status: Symptomatic hypotension is most likely in volume-depleted patients; correct volume depletion before surgery if losartan is continued 3
- Inadequate anesthesia preparation: Anesthesiologists must be prepared with vasopressors (ephedrine, phenylephrine, or terlipressin) if losartan is continued 4
- Ignoring renal function: Monitor renal function in patients with renal artery stenosis, chronic kidney disease, or severe heart failure, as these patients may be at particular risk 3
- Not restarting postoperatively: If held preoperatively, restart as soon as hemodynamically appropriate to prevent rebound hypertension 1, 2
Special Populations
Patients with renal impairment: Losartan pharmacokinetics are not substantially altered by renal insufficiency, and no dosage adjustment is necessary 5. However, monitor renal function closely perioperatively as ARBs can cause acute renal failure in at-risk patients 3.
Elderly patients: No dosage adjustment needed based on age alone 5, but elderly patients may be more susceptible to hypotension during anesthetic induction 4.