It is a common misconception that spinal anesthesia is safer and better tolerated than general anesthesia. Both confer equal risks of postoperative fatal and nonfatal myocardial infarctions. Regional or local anesthesia may be less risky than the same procedure done under general or spinal anesthesia. The type of anesthesia is best determined by the anesthesiologist.
How does a history of a myocardial infarction affect a patient’s perioperative risk?
Most investigators and clinicians believe that within the first 3-6 months after a myocardial infarction, perioperative cardiac morbidity and mortality are significantly increased. Therefore, nonemergent surgery should be delayed, if possible, until after this time. After 6 months, perioperative risk remains relatively stable, assuming there are no sequelae (e.g., congestive heart failure, rhythm disturbances). Some believe the level of risk returns to what it was before the infarct (1% in the general population), whereas others believe the risk remains somewhat elevated (2-8%).
What is meant by a patient’s preoperative cardiac risk index?
This refers to a quantitative assessment of a patient’s risk of an adverse cardiac outcome based on various preoperative clinical, historical, and laboratory variables. The first and probably most widely used of these indices was published by Goldman et al. in 1977.
How accurate are these indices?
In general, these indices appear to have a fairly high positive predictive value in assessing preoperative cardiac risk, but their low negative predictive value may make them less helpful, especially when dealing with patients who are undergoing vascular surgery. Patients who appear to be at high risk for perioperative complications, based on their risk scores, have a higher percentage of adverse outcomes than those with low risk scores. However, some patients who have low risk assessment scores may still be at substantial risk and may benefit from further study.
Which types of surgery carry higher risks of cardiac complications?
Vascular surgery appears to carry the greatest risk. Intrathoracic, intraperitoneal, and emergency procedures also carry higher risk.
Why is the risk of cardiac complications higher in vascular surgery than in other types of surgery?
The incidence of significant coronary artery disease (CAD) in patients undergoing vascular surgery is about 30%. Many vascular surgery patients have asymptomatic myocardial ischemia; because they are made sedentary by claudication, they are not active enough to induce angina and thus their CAD is undiagnosed. Some vascular procedures require significant manipulation of tissue and clamping and unclamping of vessels, which can cause marked increases in afterload and myocardial oxygen demand. Vascular surgery patients are often relatively old (mean age, 59-71 years), and older patients are at higher risk for perioperative complications.