Health Questions and Answers

MANAGEMENT OF CHRONIC MEDICAL AND OTHER DISEASES IN THE PERIOPERATIVE PERIOD

What are the important issues in the preoperative care of patients with a permanent cardiac pacemaker?
Pacemakers and implantable cardioverter/defibrillators (ICDs) should be evaluated before any operation in which electrocautery is used. Two issues must be addressed: the cardiac status of the patient, including assessment of adequacy of pacemaker function, and safety in the operating room. In general, the adequately functioning pacemaker (1) senses the patient’s own intracardiac signals and (2) delivers an electric stimulus to depolarize the myocardium at a time when it is excitable and at an appropriate rate. Pacemaker function should be assessed during the month before elective surgery at the usual source of pacemaker care.

How do you manage the problem of electromagnetic interference in the operating room?
In the operating room, electromagnetic interference (usually from electrocautery) may cause failure of the demand pacemaker. This problem can be solved by converting the pacemaker from a demand mode to a fixed-rate mode by placing a high-powered magnet over the generator. The possibility of electromagnetic interference can be minimized by placing the ground plate as far from the generator as possible and by using electrocautery in short bursts. In patients with a temporary pacemaker, the pacemaker leads provide a direct pathway by which extraneous external electrical impulses can go directly to the heart. The contact points between the leads and the generator should be covered with a surgical glove, and gloves should be worn when the unit is handled. The pacemaker/ICD should be evaluated again after the procedure. Similar precautions should be taken for patients with these devices who receive radiotherapy or lithotripsy.

Which patients undergoing noncardiac surgery are candidates for perioperative beta blockade to prevent adverse postoperative cardiac outcomes?
Two studies have demonstrated that perioperative beta blockade reduces adverse cardiac outcomes, including cardiac death, in high-risk patients undergoing noncardiac surgery. Thus, indications for such treatment include the following:

  • Established CAD
  • Peripheral vascular disease
  • Multiple cardiac disease risk factors: tobacco use, hypertension, diabetes mellitus, hyperlipidemia, age > 65 years

For best results, patients should start beta-blocker therapy before their surgery, and the dose should be titrated to produce a heart rate of 50-60.

In which patients on chronic or life-long warfarin therapy may warfarin be withheld before surgery without use of preoperative IV heparin?
Ambulatory patients taking warfarin for prevention of stroke due to chronic atrial fibrillation may stop the drug 4-5 days before surgery (to achieve an international normalized ratio [INR] ≥ 1.5). This practice has been inspired in large part by an analysis published by Kearon and Hirsh, who noted that most patients have partial protection against thromboembolism for several more days after the cessation of warfarin because of the slow decline in the anticoagulation effect. The argument against preoperative heparin also includes the fact that patients receiving heparin have a risk of hemorrhage that more than offsets the decrement in thromboembolism risk. Warfarin also may be withheld without preoperative heparin treatment in patients who suffered an acute arterial or VTE longer than 1 month before.

Should warfarin be withheld in patients with more recent thromboembolic events?
For patients with more recent thromboembolic events, Kearon and Hirsh recommend avoiding elective surgery if possible; if avoidance is not possible, patients should receive IV heparin and/or a vena caval filter.

Is it advisable to withhold warfarin from patients with mechanical heart valves?
Kearon and Hirsh suggest that patients with mechanical heart valves do not warrant either preoperative or postoperative IV heparin while off warfarin for surgery. However, the physicians providing longitudinal or primary care for such patients often are averse to leaving them unprotected against thromboembolic events. In patients with mechanical valves and patients on lifelong warfarin therapy with multiple prior arterial or VTEs, the author defers the decision about perioperative heparin to the patients and their primary care physicians.
KEY POINTS: PATIENTS IN WHOM CHRONIC WARFARIN THERAPY MAY BE WITHHELD WITHOUT PERIOPERATIVE IV HEPARIN

  • Patients taking warfarin for stroke prophylaxis related to atrial fibrillation
  • Patients at least 3 months from an episode of venous thromboembolism
  • Patients at least 1 month out from an episode of arterial thromboembolism

Which patients who have stopped warfarin before surgery should have postoperative IV heparin while awaiting therapeutic oral anticoagulation?
The risk of thromboembolism in the postoperative period is the combination of the patient’s baseline risk plus risks associated with the surgery. An additional consideration is the risk of bleeding due to heparin therapy. Kearon and Hirsh recommend that patients within 3 months of an acute venous or 1 month of an acute arterial thromboembolic event receive postoperative heparin to prevent another such event while they are awaiting full oral anticoagulation. The risk of venous or arterial thromboembolism in untreated patients outweighs the risk of bleeding associated with postoperative IV heparin. Other patients should receive the appropriate therapy to prevent postoperative venous thromboembolism while resuming warfarin.

What are the adverse consequences of postoperative hyperglycemia in diabetics?
A number of uncontrolled studies in cardiac bypass surgery patients indicate that diabetics with poorly controlled blood sugar in the perioperative period have worse outcomes. The mechanism is not well defined, but most physicians believe that wound healing is impaired in patients with poorly controlled diabetes. A second adverse effect may be a predisposition to infection. Although the clinical ramifications are not yet known, several defects in host defense mechanisms have been shown in poorly controlled diabetes, including impaired leukocyte chemotaxis, decreased intracellular bactericidal activity, and impaired cell-mediated immune response.

What management principle applies to all diabetics undergoing surgery?
All diabetics should have preoperative and postoperative glucose checks, and hyperglycemia can be treated with sliding-scale insulin.

Why is proper management of the blood sugar of type 1 diabetics so crucial in the perioperative period?
Type 1 diabetics, who account for 10% of all diabetics, have an absolute deficiency of insulin and therefore require regular administration for survival. The physiologic stress induced by induction of anesthesia and surgery leads to increased blood glucose concentrations. Surgery induces release of catecholamines, adrenocorticotropic hormone, glucagon, and growth hormone, all of which cause gluconeogenesis. Without insulin to counteract this process, diabetic ketoacidosis may result.

Describe an appropriate protocol for blood sugar management.
One approach is to give the patient one half to two thirds of the usual morning dose of intermediate-acting (NPH) insulin, monitor blood sugar levels throughout the early postoperative period, administer sliding-scale regular insulin as needed, and then resume the patient’s usual regimen when he or she is able to eat. Alternatively, a patient may be treated with a continuous insulin infusion with concomitant IV dextrose.

How should the insulin regimens of type 2 diabetics be managed perioperatively?
Type 2 diabetics who are treated with insulin may be managed as described in question 98, particularly if time in the operating room is expected to be long. For surgical procedures of minor or intermediate complexity, and especially for day surgery, patients may withhold the morning dose of insulin, have periodic checks of blood glucose during recovery, and resume their usual regimen the same evening when they are able to eat.

Describe the management of type 2 diabetics taking medications other than insulin.
Type 2 diabetics are currently treated with a variety of oral medications that remedy one or more of the specific defects associated with type 2 diabetes: target-tissue resistance to insulin, low insulin secretion by islet cells, and increased hepatic gluconeogenesis. These agents should be withheld before surgery.

What is the specific recommendation for metformin?
The manufacturer of metformin recommends that it be held 48 hours before a contrast-dye procedure is performed because of concerns that lactic acidosis may occur in a patient who develops ARF.

Summarize the recommendations for sulfonylureas.
The longer-acting, older sulfonylureas (chlorpropamide and tolbutamide) should be discontinued at least 3 days before surgery because of their long half-lives. The second-generation sulfonylureas, as well as the newer agents, including alpha glucosidase inhibitors, biguanides and thazolidinediones, may be stopped on the day of surgery. Patients with chronic liver or renal disease should stop sulfonylureas at an earlier point because of their prolonged activity in such disease states.

When may oral antidiabetic drugs be resumed?
Oral antidiabetic drugs can be resumed with resumption of oral intake.

What are the two reasons for strict continuation of medications for comorbid diseases during the perioperative period?

  • Continued administration of medications minimizes the chance that patients will develop an acute exacerbation of chronic disease in the perioperative period. Patients with serious chronic disease should receive medications on the day of surgery and throughout the perioperative period. Such conditions include but are not limited to CAD, CHF, hypertension, seizure disorders (particularly if the seizure is generalized tonic-clonic), Parkinson’s disease, and COPD.
  • Continued administration of medications avoids the development of a withdrawal syndrome with abrupt cessation

How should patients on chronic corticosteroid therapy be managed in the perioperative period?
Although it is possible to assess the reserve of the hypothalamic-pituitary-adrenal (HPA) axis in response to stress, this assessment is rarely done in clinical practice. Instead, it is assumed that most patients on chronic corticosteroid therapy are at risk for developing secondary adrenal insufficiency due to the stress of surgery and therefore should receive stress doses of steroids. Included are patients taking daily prednisone for more than 3 weeks and patients with Cushing’s syndrome. In patients taking < 10 mg each morning, the HPA axis is unlikely to be suppressed, but many experts nevertheless recommend that they receive stress doses of steroids for surgery.

Suggest steroid regimens for moderate and severe illness.

  • For moderate illness: hydrocortisone, 50 mg twice daily orally or intravenously; taper rapidly to maintenance dose.
  • For severe illness: hydrocortisone, 100 mg IV every 8 hours; decrease dose by half each day, keeping in mind the course of the illness.

Suggest steroid regimens for minor, moderately stressful, and major procedures.

  1. For minor procedures under local anesthesia and most radiologic studies: no corticosteroid supplementation is needed.
  2. For moderately stressful procedures (e.g., barium enema, endoscopy, arteriography): single 100-mg dose of hydrocortisone IV just before the procedure.
  3. For major surgery: hydrocortisone, 100 mg IV just before induction of anesthesia and every 8 hours for the first 24 hours; then taper rapidly by decreasing the dose by half each day to maintenance level.

Note: If IV access cannot be obtained, hydrocortisone can be administered rectally.

References

BIBLIOGRAPHY

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