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Getting the body ready: anemia, blood sugar, exercise and the heart check

What research shows about the things that can be improved before a planned operation, and where trials found less benefit than hoped.

2 minute read8 sources, each checked word for wordLibrary checked October 18, 2026

In short

  • Even mild anemia before major surgery is linked with more complications and deaths within 30 days.E2Good1
  • High blood sugar around surgery is linked with longer stays, complications and deaths.E2Good2
  • Exercise programs before surgery helped high-risk patients in one trial but did not help frail patients in another.E1Strong3,4

How sure each claim is:E1StrongE2GoodOfficial textReviewWhat the grades mean

Anemia

In a large study of noncardiac surgery, anemia before the operation, even if mild, was independently linked with higher 30-day illness and death.E2Good1

An international consensus covers how to diagnose anemia and iron deficiency in surgical patients, who to treat, and how to follow up.E2Good5

Blood sugar

High blood sugar around surgery is associated with longer hospital stays, complications and deaths after noncardiac general surgery.E2Good2

In one surgical quality program, high blood sugar was linked with worse outcomes in people with and without diabetes. But patients with high sugar who received insulin did no worse than those with normal sugar.E2Good6

Exercise before surgery (prehabilitation)

In a randomized trial, an exercise program tailored to each patient improved outcomes for high-risk patients having major abdominal surgery. The benefit was explained by better aerobic fitness.E1Strong3

In another trial, a multimodal prehabilitation program did not change outcomes for frail patients having colorectal cancer surgery within an enhanced recovery pathway.E1Strong4

Smoking

Stopping smoking before surgery reduced postoperative complications by 41% in pooled trials, and longer periods off cigarettes reduced complications more.E1Strong7

The heart check

A 2024 guideline comes from the American Heart Association, the American College of Cardiology and seven other societies. It guides clinicians in evaluating and managing the heart in adults having noncardiac surgery.E2Good8

Which heart tests, if any, are needed depends on the person and the operation, and is decided by the team.

What is not known yet

Prehabilitation trials disagree. Benefit was shown in high-risk abdominal surgery but not in frail colorectal cancer patients. So it is not yet clear who gains most.E1Strong3,4

Questions you might bring to your anesthesia team

  1. Should my blood count or iron be checked before surgery, and treated if low?
  2. How will my blood sugar be managed before, during and after surgery?
  3. Is there an exercise or breathing program worth starting before my operation?
  4. Do I need any heart tests before this surgery?

Every claim in this guide was written from its sources and checked against them word for word. Its clinical review by Dr. Recio, a practicing nurse anesthesiologist (CRNA), is pending. This line changes when the review is done.

Sources

Each source opens on PubMed, DailyMed or the publisher's page. Under each one are the exact words from it that this page relies on, copied word for word and checked against the original.

  1. Preoperative anaemia and postoperative outcomes in non-cardiac surgery: a retrospective cohort study. Musallam KM, Lancet, 2011. E2Good Observational study
    The words this page rests on
    Preoperative anaemia, even to a mild degree, is independently associated with an increased risk of 30-day morbidity and mortality in patients undergoing major non-cardiac surgery.
  2. Prevalence and clinical outcome of hyperglycemia in the perioperative period in noncardiac surgery. Frisch A, Diabetes Care, 2010. E2Good Observational study
    The words this page rests on
    Perioperative hyperglycemia is associated with increased LOS, hospital complications, and mortality after noncardiac general surgery.
  3. Personalised Prehabilitation in High-risk Patients Undergoing Elective Major Abdominal Surgery: A Randomized Blinded Controlled Trial. Barberan-Garcia A, Ann Surg, 2018. E1Strong Randomized trial
    The words this page rests on
    Prehabilitation enhanced postoperative clinical outcomes in high-risk candidates for elective major abdominal surgery, which can be explained by the increased aerobic capacity.
  4. Effect of Multimodal Prehabilitation vs Postoperative Rehabilitation on 30-Day Postoperative Complications for Frail Patients Undergoing Resection of Colorectal Cancer: A Randomized Clinical Trial. Carli F, JAMA Surg, 2020. E1Strong Randomized trial
    The words this page rests on
    In frail patients undergoing colorectal cancer resection (predominantly minimally invasive) within an enhanced recovery pathway, a multimodal prehabilitation program did not affect postoperative outcomes.
  5. International consensus statement on the peri-operative management of anaemia and iron deficiency. Muñoz M, Anaesthesia, 2017. E2Good Consensus statement
    The words this page rests on
    These statements include: a diagnostic approach for anaemia and iron deficiency in surgical patients; identification of patients appropriate for treatment; and advice on practical management and follow-up.
  6. Importance of perioperative glycemic control in general surgery: a report from the Surgical Care and Outcomes Assessment Program. Kwon S, Ann Surg, 2013. E2Good Observational study
    The words this page rests on
    Perioperative hyperglycemia was associated with adverse outcomes in general surgery patients with and without diabetes. However, patients with hyperglycemia who received insulin were at no greater risk than those with normal blood glucoses.
  7. Smoking cessation reduces postoperative complications: a systematic review and meta-analysis. Mills E, Am J Med, 2011. E1Strong Meta-analysis
    The words this page rests on
    We pooled the 6 randomized trials and demonstrated a relative risk reduction of 41% (95% confidence interval [CI], 15-59, P = .01) for prevention of postoperative complications. We found that each week of cessation increases the magnitude of effect by 19%. Trials of at least 4 weeks' smoking cessation had a significantly larger treatment effect than shorter trials (P = .04).
    Longer periods of smoking cessation decrease the incidence of postoperative complications.
  8. 2024 AHA/ACC/ACS/ASNC/HRS/SCA/SCCT/SCMR/SVM Guideline for Perioperative Cardiovascular Management for Noncardiac Surgery: A Report of the American College of Cardiology/American Heart Association Joint Committee on Clinical Practice Guidelines. Thompson A, Circulation, 2024. E2Good Guideline
    The words this page rests on
    The "2024 AHA/ACC/ACS/ASNC/HRS/SCA/SCCT/SCMR/SVM Guideline for Perioperative Cardiovascular Management for Noncardiac Surgery" provides recommendations to guide clinicians in the perioperative cardiovascular evaluation and management of adult patients undergoing noncardiac surgery.