Cardiac risk reduction in non-cardiac surgery: the role of anaesthesia and monitoring techniques

Etomidate vs propofol in coronary heart disease patients undergoing major noncardiac surgery: A randomized clinical trial

BACKGROUND

The ideal depth of general anesthesia should achieve the required levels of hypnosis, analgesia, and muscle relaxation while minimizing physiologic responses to awareness. The choice of anesthetic strategy in patients with coronary heart disease (CHD) undergoing major noncardiac surgery is becoming an increasingly important issue as the population ages. This is because general anesthesia is associated with a risk of perioperative cardiac complications and death, and this risk is much higher in people with CHD.

AIM

To compare hemodynamic function and cardiovascular event rate between etomidate- and propofol-based anesthesia in patients with CHD.

METHODS

This prospective study enrolled consecutive patients (American Society of Anesthesiologists grade II/III) with stable CHD (New York Heart Association class I/II) undergoing major noncardiac surgery. The patients were randomly allocated to receive either etomidate/remifentanil-based or propofol/remifentanil-based general anesthesia. Randomization was performed using a computer-generated random number table and sequentially numbered, opaque, sealed envelopes. Concealment was maintained until the patient had arrived in the operating theater, at which point the consulting anesthetist opened the envelope. All patients, data collectors, and data analyzers were blinded to the type of anesthesia used. The primary endpoints were the occurrence of cardiovascular events (bradycardia, tachycardia, hypotension, ST-T segment changes, and ventricular premature beats) during anesthesia and cardiac troponin I level at 24 h. The secondary endpoints were hemodynamic parameters, bispectral index, and use of vasopressors during anesthesia.

RESULTS

The final analysis included 40 patients in each of the propofol and etomidate groups. The incidences of bradycardia, hypotension, ST-T segment changes, and ventricular premature beats during anesthesia were significantly higher in the propofol group than in the etomidate group (P < 0.05 for all). The incidence of tachycardia was similar between the two groups. Cardiac troponin I levels were comparable between the two groups both before the induction of anesthesia and at 24 h after surgery. When compared with the etomidate group, the propofol group had significantly lower heart rates at 3 min after the anesthetic was injected (T₁) and immediately after tracheal intubation (T₂), lower systolic blood pressure at T₁, and lower diastolic blood pressure and mean arterial pressure at T₁, T₂, 3 min after tracheal intubation, and 5 min after tracheal intubation (P < 0.05 for all). Vasopressor use was significantly more in the propofol group than in the etomidate group during the induction and maintenance periods (P < 0.001).

CONCLUSION

In patients with CHD undergoing noncardiac major surgery, etomidate-based anesthesia is associated with fewer cardiovascular events and smaller hemodynamic changes than propofol-based anesthesia.

The incremental risk of noncardiac surgery on adverse cardiac events following coronary stenting

BACKGROUND

Recent coronary stent placement and noncardiac surgery contribute to the risk of adverse cardiac events, but the relative contributions of these two factors have not been quantified.

OBJECTIVES

This research was designed to determine the incremental risk of noncardiac surgery on myocardial infarction (MI) and coronary revascularization following coronary stenting.

METHODS

A U.S. retrospective cohort study of patients receiving coronary stents at Veterans Affairs medical centers between 2000 and 2010 was used to match patients undergoing noncardiac surgery within 24 months of stent placement to two patients with stents not undergoing surgery. Patients were matched on stent type and cardiac risk factors present at the time of stent placement. A composite endpoint of MI and/or cardiac revascularization for the 30-day interval post-surgery was calculated. Adjusted risk differences (RD) were compared across time periods following stent implantation, using generalized estimating equations.

RESULTS

We matched 20,590 surgical patients to 41,180 nonsurgical patients. During the 30-day interval following noncardiac surgery, the surgical cohort had higher rates of the composite cardiac endpoint (3.1% vs. 1.9%; RD: 1.3%; 95% confidence interval: 1.0% to 1.5%). The incremental risk of noncardiac surgery adjusted for surgical characteristics ranged from 3.5% immediately following stent implantation to 1% at 6 months, after which it remained stable out to 24 months. Factors associated with a significant reduction in risk following surgery more than 6 months post-stent included elective inpatient procedures (ΔRD: 1.8%; p = 0.01), high-risk surgery (ΔRD: 3.7%; p = 0.01), and drug-eluting stent (DES) (ΔRD: 1.3%; p = 0.01).

CONCLUSIONS

The incremental risk of noncardiac surgery on adverse cardiac events among post-stent patients is highest in the initial 6 months following stent implantation and stabilizes at 1.0% after 6 months. Elective, high-risk, inpatient surgery, and patients with DES may benefit most from delay from a 6-month delay after stent placement.

Multivariable Predictors of Postoperative Cardiac Adverse Events after General and Vascular Surgery: Results from the Patient Safety in Surgery Study

BACKGROUND

Cardiac adverse events (CAEs) are relatively infrequent, but highly lethal, after noncardiac operations. The value of available risk scoring systems is uncertain and these systems can be outdated. We used the Patient Safety in Surgery Study database to develop and test a model to predict patient risk for CAEs after general and vascular surgical operations.

STUDY DESIGN

As part of the Patient Safety in Surgery Study, following the National Surgical Quality Improvement Program's protocol, multiple demographic, preoperative, perioperative, and outcomes variables were measured during a 3-year period. Data from 128 Veterans Affairs medical center hospitals and from 14 academic medical centers on 183,069 patients were used in a logistic regression analysis to model multivariable predictors of serious CAEs (cardiac arrest or acute myocardial infarction within 30 days of operation).

RESULTS

CAEs occurred in 2,362 patients (1.29%) and of these, 59.44% expired. Multivariable stepwise logistic regression identified 20 independent predictors of CAEs, which excluded most cardiac-specific risk factors. The most important multivariable predictors of CAE were American Society of Anesthesiologists physical status classification, work relative value units of the most complex procedure, age, and type of operation. A risk prediction scoring system using the logistic regression odds ratios proved to be a useful prediction tool when tested using a random sample from the database.

CONCLUSIONS

CAEs after noncardiac operations are relatively infrequent but highly lethal. Operation type and urgency and American Society of Anesthesiologists physical status assessment are important independent predictors of cardiac morbidity, but angina, recent MI, and earlier cardiac operation are not. A prediction scoring system based on the Patient Safety in Surgery Study multivariable odds ratios is likely to be predictive of future events in a similar population requiring noncardiac procedures. This risk model can also serve as a tool to measure quality and effectiveness of care by providers who perform noncardiac operations.

Surgical risk in patients with metabolic syndrome: focus on lipids and hypertension

The metabolic syndrome describes a clustering of risk factors that predispose individuals to cardiovascular disease and type 2 diabetes mellitus. Abdominal obesity is a key component of the metabolic syndrome, increasing the incidence of insulin resistance, vascular inflammation, dyslipidemia, and hypertension. Adipose tissue (now recognized as an endocrine organ) and its hormonal products appear to play a significant role in signaling organs throughout the body in the regulation of fat and glucose metabolism. These mechanisms are clearly involved in the development of cardiovascular and metabolic disease and may also lead to increased surgical risks. The components of the syndrome that are most likely to affect surgical patients are obesity, hypertension, and disorders of glucose metabolism. This article focuses on each of these risk factors, the effects on surgical patients, and strategies to improve outcomes in the perioperative period.