Postoperative myocardial infarction: a study of predisposing factors, diagnosis and mortality in a high risk group of surgical patients

Perioperative Interventions to Modify Risk of Morbidity and Mortality

Perioperative myocardial ischemia is the single most important, potentially reversible risk factor for mortality and cardiovascular complications during and after noncardiac surgery. The influence of anesthetic choices and techniques on cardiac risk in noncardiac surgery is difficult to ascertain because of the low incidence of morbid cardiac outcomes in the surgical population as a whole. This article summarizes several areas (eg, perioperative βblockade, glucose management, and perioperative hemodynamics) that have been addressed in well-designed clinical trials.

Review of a Large Clinical Series: Perioperative Myocardial Infarction in Low-Risk Patients Undergoing Noncardiac Surgery Is Associated With Intraoperative Hypotension

This is an investigation of the association of intraoperative hypotension and perioperative myocardial infarction (MI) in low-risk patients undergoing noncardiac surgery. The case-control study compared all patients who experienced perioperative MI during the years 1996 through 1999 to a similar group of patients matched for multiple variables. Perioperative MI occurred in 22 patients. Two patients, who underwent unusual surgical procedures, were excluded from the study. The remaining 20 MI patients were compared with 40 patients who had the same types of surgery and similar mean ages, co-morbidities and preoperative evaluations. Of the patients suffering a perioperative MI, 14 (70%) experienced intraoperative hypotension, as opposed to 11 (28%) of those who did not have an MI ( P = .002). Six (30%) MI patients died as opposed to only one (2.5%) of the non-MI group ( P = .004). When subjected to logistic regression analysis, intraoperative hypotension remained the only significant variable associated with perioperative MI ( P = .0056). Intraoperative hypotension is associated with an increased risk of perioperative myocardial infarction and death.

Risk Assessment and Characterization of 30-Day Perioperative Myocardial Infarction Following Spine Surgery: A Retrospective Analysis of 1346 Consecutive Adult Patients

STUDY DESIGN

A retrospective review.

OBJECTIVE

The aim of the study was to perform a risk assessment of 30-day perioperative myocardial infarction (MI) for spine surgery patients.

SUMMARY OF BACKGROUND DATA

There is an increased emphasis to reduce complications and improve outcomes after spinal surgery. One of the more devastating perioperative complications of spinal surgery is MI.

METHODS

We evaluated all medical records of 1346 consecutive patients who underwent spinal surgery at a single institution from 2008 to 2010 for incidence of MI within 30 days of surgery and documented all demographic, preoperative, and operative variables. Associations between postoperative MI and individual risk factors were determined using logistic regression analysis. Patients were stratified into emergent and elective groups and a similar analysis was performed.

RESULTS

Overall, 22 patients (1.6%) had 30-day perioperative MI, 14 patients (1.2%) undergoing elective surgery, and 8 patients (4.2%) after emergent surgery (P = 0.047). Three (13.6%) patients experienced 30-day mortality and an additional 3 (13.6%) patients experienced mortality within 1 year. Multivariate logistic regression determined that age more than 65 years, atrial fibrillation, hypertension, prior MI, anticoagulant use, low albumin, length of stay more than 7 days, intraoperative transfusion, trauma etiology, baseline creatinine more than 1  mg/dL, and at least 2 levels of spinal fusion were predictive of postoperative MI. For patients undergoing emergent surgery, age more than 65 years was associated with an increased risk of postoperative MI. When stratified by elective surgery, we found that age more than 65, postoperative stay more than 7 days, intraoperative blood transfusion, baseline creatinine more than 1  mg/dL, and fusion of more than 1 level were associated with an increased risk of MI.

CONCLUSION

The present study demonstrates a low incidence of MI after elective surgery with a higher incidence after emergent spine surgery and identifies patient factors predictive of postoperative MI.

LEVEL OF EVIDENCE

3.

A case-cohort study of postoperative myocardial infarction: impact of anemia and cardioprotective medications

OBJECTIVE

Postoperative myocardial infarction (poMI) is a serious and costly complication. Multiple risk factors for poMI are known, but the effect of anemia and cardioprotective medications have not been defined in real-world surgical practice.

METHODS

Patients undergoing inpatient elective surgery were assessed at 17 hospitals from 2008 to 2011 for the occurrence of poMI (American Heart Association definition). Non-MI control patients were chosen randomly on the basis of case type. Descriptive, univariable, and multivariable statistical analysis were performed for primary outcomes of poMI and death at 30 days.

RESULTS

Compared with controls (N = 304), patients with poMI (N = 222) were older (72 ± 11 vs 60 ± 17 years, P < .0001), had a lesser preoperative hematocrit (37 ± 6 vs 39 ± 5, P < .0001), more often were smokers, had a preoperative T-wave abnormality (21% vs 9%, P < .0001), and had a preoperative stress test with a fixed deficit (26% vs 3%; P < .001). Preoperative factors associated with poMI included peripheral vascular disease (odds ratio 2.6; 95% confidence interval 1.3-5.3), tobacco use (1.7; 1.01-2.9), history of percutaneous coronary angioplasty (2.8; 1.6-5.0), and age (1.05; 1.03-1.07), whereas hematocrit >35 (0.51; 0.32-0.82) and preoperative acetylsalicylic acid, ie, aspirin (0.59; 0.4-0.97) were protective. Preoperative β-blockade, statin, and use of angiotensin-converting enzyme inhibitors were not associated with lesser rates of poMI. Non-MI complication rates were 23-fold greater in the poMI group compared with the control group (P < .0001). Mortality with poMI within 30 days was 11% compared with 0.3% in non-MI control patients (P < .0001). In patients with poMI, factors independently associated with death included use of epidurals (3.5; 1.07-11.4) and bleeding (4.2; 1.1-16), whereas preoperative use of aspirin (0.29; 0.1-0.88), and postoperative β-blockade (0.18; 0.05-0.63) were protective. Cardiac catheterization, percutaneous coronary intervention, or coronary artery bypass grafting after poMI was performed in 34% of those alive and 20% of those who died (P = .16).

CONCLUSION

In the current era, poMI patients have a markedly increased risk of death. This risk is decreased with preoperative use of acetylsalicylic acid and post MI β-blockade. Further study is warranted to explore the role of anemia and cardiac interventions after poMI.

A nomogram to predict major complications after hip and knee arthroplasty

We aimed to develop a nomogram for risk stratification of major postoperative complications in hip and knee arthroplasty based on preoperative and intraoperative variables, and assessed whether this tool would have better predictive performance compared to the Surgical Apgar Score (SAS). Logistic regression analysis was performed to develop a nomogram. Discrimination and calibration were assessed. Net reclassification improvement (NRI) was used to compare to the SAS. All variables were found to be statistically significant predictors of post-operative complications except race and lowest heart rate. The concordance index was 0.76 with good calibration. Compared to the SAS, the NRI was 71.5% overall. We developed a clinical prediction tool, the Morbidity and Mortality Acute Predictor for arthroplasty (arthro-MAP) that might be useful for postoperative risk stratification.

Perioperative hypertension: a review of current and emerging therapeutic agents

Perioperative hypertension is a common problem encountered by anesthesiologists, surgeons, internists, and intensivists. Surprisingly, no randomized, placebo-controlled studies exist that show that the treatment of perioperative hypertension reduces morbidity or mortality. Nevertheless, perioperative hypertension requires careful management. While sodium nitroprusside and nitroglycerin are commonly used to treat these conditions, these agents are less than ideal. Intravenous beta blockers and calcium channel blockers have particular appeal in this setting.

Does the Surgical Apgar Score measure intraoperative performance?

OBJECTIVE

To evaluate whether Surgical Apgar Scores measure the relationship between intraoperative care and surgical outcomes.

SUMMARY BACKGROUND DATA

With preoperative risk-adjustment now well-developed, the role of intraoperative performance in surgical outcomes may be considered. We previously derived and validated a 10-point Surgical Apgar Score--based on intraoperative blood loss, heart rate, and blood pressure--that effectively predicts major postoperative complications within 30 days of general and vascular surgery. This study evaluates whether the predictive value of this score comes solely from patients' preoperative risk or also measures care in the operating room.

METHODS

Among a systematic sample of 4119 general and vascular surgery patients at a major academic hospital, we constructed a detailed risk-prediction model including 27 patient-comorbidity and procedure-complexity variables, and computed patients' propensity to suffer a major postoperative complication. We evaluated the prognostic value of patients' Surgical Apgar Scores before and after adjustment for this preoperative risk.

RESULTS

After risk-adjustment, the Surgical Apgar Score remained strongly correlated with postoperative outcomes (P < 0.0001). Odds of major complications among average-scoring patients (scores 7-8) were equivalent to preoperative predictions (likelihood ratio (LR) 1.05, 95% CI 0.78-1.41), significantly decreased for those who achieved the best scores of 9-10 (LR 0.52, 95% CI 0.35-0.78), and were significantly poorer for those with low scores--LRs 1.60 (1.12-2.28) for scores 5-6, and 2.80 (1.50-5.21) for scores 0-4.

CONCLUSIONS

Even after accounting for fixed preoperative risk--due to patients' acute condition, comorbidities and/or operative complexity--the Surgical Apgar Score appears to detect differences in intraoperative management that reduce odds of major complications by half or increase them by nearly 3-fold.

Intraoperative tachycardia and hypertension are independently associated with adverse outcome in noncardiac surgery of long duration

Relatively little is known about the influence of intraoperative hemodynamic variables on surgical outcomes. We drew subjects (n = 797) from a study of patients undergoing major noncardiac surgery. The physiological component of the POSSUM (Physiological and Operative Severity Score for the enUmeration of Mortality) operative risk stratification index was determined, and intraoperative measurements of heart rate (HR), mean arterial blood pressure, and systolic arterial blood pressure (SAP) were retrieved from computerized anesthesia records. For every 5-min epoch during the surgery, HR, mean arterial blood pressure, and SAP were each classified as low, normal, or high. Negative surgical outcome (NSO) was defined as a hospital stay of >10 days with a morbid condition or death during the hospital stay. Statistical analyses included Mantel-Haenszel tests and multiple logistic regression. There was no significant association between hemodynamic variables and NSO with short operations. In 388 patients with operations longer than the median time of 220 min, NSO occurred in 15.6%. Controlling for POSSUM score and operation time beyond 220 min, both high HR (odds ratio, 2.704; P = 0.01) and high SAP (odds ratio, 2.095; P = 0.009) were associated with NSO in longer operations. Thus, intraoperative tachycardia and hypertension were associated independently with adverse outcomes after major noncardiac surgery of long duration, over and above the risk imparted by underlying medical conditions.

IMPLICATIONS

Intraoperative tachycardia and hypertension were associated with negative postoperative outcomes after major noncardiac surgery of long duration. These results imply that intraoperative tachycardia and hypertension may have independent effects on outcome over and above the risk imparted by underlying medical conditions.

Cost Containment in Vascular Surgery

In the last decade, the delivery of health care and the role of the physician have undergone radical change. With the ad vent of managed care and the tightening of restrictions by Medicare and insurance companies, physicians have been required to review, re-engineer, and revitalize their role. Increasing financial pressures at the hospital level have caused administrators to cut costs at all levels. It is imper ative that physicians take an active role in cost containment so that the quality of care is not sacrificed. Cost containment in vascular surgery is an urgent priority in health care. Copyright © 2000 by W.B. Saunders Company.

Acute myocardial infarction occurring in versus out of the hospital: patient characteristics and clinical outcome. Maximal Individual TheRapy in Acute Myocardial Infarction (MITRA) Study Group

OBJECTIVES

We describe the baseline characteristics and clinical course of patients who had an acute myocardial infarction (AMI) during their hospital stay.

BACKGROUND

In comparison with patients who had an AMI outside of the hospital (prehospital AMI), the data on patients who had an AMI in the hospital are poorly described.

METHODS

Patients with an in-hospital AMI were prospectively registered in the Southwest German Maximal Individual TheRapy in Acute myocardial infarction (MITRA) study and compared with patients with prehospital AMI.

RESULTS

Of 5,888 patients with AMI, 403 patients (6.8%) had an in-hospital AMI. These patients were older, more often male and sicker as compared with the patients with a prehospital AMI. They also showed a higher prevalence of concomitant diseases, such as arterial hypertension, diabetes mellitus, renal insufficiency and contraindications for thrombolysis. There was no significant difference regarding the use of reperfusion therapy, either thrombolysis (in-hospital AMI 44.2% vs. prehospital AMI 49.1%; odds ratio [OR] 0.86, 95% confidence interval [CI] 0.70 to 1.05) or primary angioplasty (9.9% vs. 8.2%; OR 1.23, 95% CI 0.88 to 1.73), or a combination of both, between the two groups. The interval from symptom onset to the start of treatment in patients receiving reperfusion therapy was 55 min for patients with an in-hospital AMI versus 180 min for patients with a prehospital AMI (p = 0.001). In-hospital death occurred in 110 (27.3%) of 403 patients with an in-hospital versus 762 (13.9%) of 5,485 patients with a prehospital AMI (OR 2.33, 95% CI 1.85 to 2.94). This was confirmed by logistic regression analysis after adjusting for other confounding variables (OR 1.67, 95% CI 1.23 to 2.24).

CONCLUSIONS

In-hospital AMI occurred in 6.8% of patients. Time to intervention was shorter; however, the use of reperfusion therapy for in-hospital AMI was not different from that for prehospital AMI. In particular, primary angioplasty seems to be underused in these patients. This, as well as the selection of patients, may result in the high hospital mortality rate of 27.3%.

Intraoperative hemodynamic predictors of mortality, stroke, and myocardial infarction after coronary artery bypass surgery

Evidence that intraoperative hemodynamic abnormalities influence outcome is limited. The purpose of this study was to determine whether intraoperative hemodynamic abnormalities were associated with mortality, stroke, or perioperative myocardial infarction (PMI) in a large cohort of patients undergoing coronary artery bypass grafting. Risk factors and outcomes were queried from a state-mandated cardiac surgery reporting system at two hospitals in New York, NY. Intraoperative hemodynamic abnormalities were derived from computerized anesthesia records by assessing the duration of exposure to moderate or severe extremes of hemodynamic variables. Multivariate logistic regression identified independent predictors of perioperative mortality, stroke, and PMI. Among 2149 patients, there were 50 mortalities, 51 strokes, and 85 PMIs. In the precardiopulmonary bypass (pre-CPB) period, pulmonary hypertension was a predictor of mortality (odds ratio [OR] 2.1, P = 0.029), and bradycardia and tachycardia were predictors of PMI (OR 2.9, P = 0.007 and OR 2.0, P = 0.028, respectively). During CPB, hypotension was a predictor of mortality (OR 1.3, P = 0.025). Post-CPB, tachycardia was a predictor of mortality (OR 3.1, P = 0.001), diastolic arterial hypertension was a predictor of stroke (OR 5.4, P = 0.012), and pulmonary hypertension was a predictor of PMI (OR 7.0, P < 0.001). Increased pulmonary arterial diastolic pressure post-CPB was a predictor of mortality (OR 1.2, P = 0.004), stroke (OR 3.9, P = 0.002), and PMI (OR 2.2, P = 0.001). Rapid intraoperative variations in blood pressure and heart rate were not independent predictors of these outcomes. These findings demonstrate the prognostic significance of intraoperative hemodynamic abnormalities, including data from pulmonary artery catheterization, to adverse postoperative outcomes. It is not known whether interventions to control these variables would improve outcome.

IMPLICATIONS

Intraoperative hemodynamic abnormalities, including pulmonary hypertension, hypotension during cardiopulmonary bypass, and postcardiopulmonary bypass pulmonary diastolic hypertension, were independently associated with mortality, stroke, and perioperative myocardial infarction over and above the effects of other preoperative risk factors.

The role of myocardial revascularization preceding noncardiac surgery

Of about 6.7 million Americans who have coronary artery disease, approximately 700,000 undergo various noncardiac operations annually in the United States. Perioperative cardiac complications remain the leading cause of morbidity and mortality not related to the primary operative procedure; the mechanisms of perioperative ischemia and infarction are unclear. Currently, clinicians, using a combination of clinical and laboratory findings, can estimate the risk of noncardiac surgical procedures with a high degree of precision, but much less is known about the preferred approach to patient management after noninvasive risk stratification. Coronary angiography and revascularization are frequently recommended for those determined by functional tests to be at moderate and high risk, but the risks of revascularization are often substantially higher among these patients. No randomized, controlled trials exist to guide patient management. Quantitative decision analysis based on published nonrandomized data suggests that coronary angiography with selective myocardial revascularization should be performed to reduce the risk of noncardiac surgery only if the risk of noncardiac surgery is greater than 5% and the risk of coronary angiography with selective revascularization is less than 3%. On the other hand, if independent indications exist for myocardial revascularization, it should generally be performed before the noncardiac operation.

Surgery-specific considerations in the cardiac patient undergoing noncardiac surgery

Myocardial infarction after noncardiac surgery in patients with coronary artery disease results from the interplay of patient-specific, anesthetic-specific, and surgery-specific factors. Surgery-specific factors include the stress response to injury, both neurohormonal and hemostatic alterations, and clinically-significant operative parameters such as urgency, duration, blood loss, body core temperature, fluid shifts, and location of surgery. The impact of these factors bears out during the entire perioperative period and influences preoperative risk assessment, cardiac evaluation and intervention, intraoperative strategy, and postoperative management. Overall, the morbidity and mortality of surgery is minimal even in high-risk patients, and the contribution of surgery-specific factors to operative risk is subtle compared with that of patient specific-factors such as severity of coronary disease and other comorbid conditions. Nonetheless, the optimal surgical management of patients with coronary disease requires the collaborative effort of the anesthesiologist, cardiologist, and surgeon.

Control of blood pressure and heart rate in patients randomized to epidural or general anesthesia for lower extremity vascular surgery. Perioperative Ischemia Randomized Anesthesia Trial (PIRAT) Study Group

STUDY OBJECTIVE

To examine the degree of success at maintaining patients randomized to epidural or general anesthesia for peripheral vascular surgery within predetermined blood pressure (BP) and heart rate (HR) limits. To investigate associations between such hemodynamic control and intraoperative myocardial ischemia and postoperative major cardiac morbidity.

DESIGN

Prospective randomized clinical trial.

SETTING

University-affiliated hospital.

PATIENTS

100 patients undergoing elective lower extremity revascularization for atherosclerotic peripheral vascular disease.

INTERVENTIONS

Patients were randomized to receive either epidural anesthesia or general anesthesia. Blood pressure and HR limits were determined prior to randomization. Hemodynamic monitoring and management of anesthesia was standardized. Myocardial ischemia and major cardiac morbidity were diagnosed by a blinded cardiologist, based on continuous ambulatory ECG monitoring, cardiac enzymes, and 12 lead ECGs. Intraoperative BP and HR date were analyzed by investigators masked to the type of anesthesia given.

MEASUREMENTS AND MAIN RESULTS

A greater percentage of patients randomized to general anesthesia had intraoperative BPs more above their limit (95% vs 72%, p = 0.002) and/or more rapid changes in HR (75% vs 48%, p = 0.008) or BP (100% vs 93%, p = 0.04) than those randomized to epidural anesthesia. Intraoperative ischemia and major cardiac morbidity were similar in the two anesthesia groups. Patients experiencing intraoperative ischemia, regardless of anesthetic type, more frequently had BPs greater than 10% above their upper limit (90% vs 60% p = 0.04) and/or more rapid HR changes (90% vs 58%, p = 0.03) compared with patients without ischemia. These vital sign abnormalities, however, were not necessarily temporally related to the ischemic episodes. Patients experiencing subsequent major cardiac morbidity were not different from other patients with respect to excursions out of BP on HR limits.

CONCLUSIONS

Prevention of elevated intraoperative BP and/on rapid changes in BP or HR may be more successful with epidural than with general anesthesia. Such vital sign abnormalities may occur more frequently in patients who have had intraoperative ischemia or are at risk for having it later in the procedure.

Long-term prognosis after peri-operative cardiac complications

The objective was to document the 5 year prognosis of patients who had cardiac complications after non-cardiac surgery.

DESIGN

5-year follow-up of 218 patients originally enrolled in a prospective study to identify risks factors for peri-operative complications.

SETTING

an academic medical center. Participants were hypertensives and diabetics who underwent elective surgery between 1982 and 1985. In the original study, patients were evaluated pre-operatively, monitored intra-operatively by an independent observer, and followed daily for 7 days post-operatively according to a standard surveillance protocol. Outcomes were judged by assessors blinded to the pre-operative status and intra-operative course. Patients were interviewed at 3 and 5 years post-operatively. Patients with post-operative cardiac complications had significantly higher rates of overall mortality, mortality attributable to cardiac causes (MI, CHF, arrest), and mortality attributable to other cardiovascular causes (stroke, renal failure) than patients without cardiac complications. For example, at 5 years 11% of those patients without post-operative cardiac complications had cardiac deaths, in contrast to 45% of those patients with post-operative cardiac complications. Proportional hazards analysis demonstrated that post-operative cardiac complications remained a significant predictor of cardiac (p < 0.001) and cardiovascular (p < 0.0001) mortality controlling for pre-operative cardiac disease, other non-cardiovascular comorbid diseases, age, sex, diabetes, and pre-operative renal insufficiency or stroke. Similarly, patients with post-operative non-fatal cardiac complications had higher rates of cardiac or cardiovascular events during the 5 year follow-up period. We conclude that post-operative cardiac complications have a significant adverse long-term prognostic impact comparable to the prognostic impact of myocardial infarction, ischemia or congestive failure in the non-operative setting. Understanding these events could be an important factor in identifying patients at high risk for subsequent peri-operative complications.

Perioperative myocardial infarction with noncardiac surgery

The incidence of perioperative myocardial infarction with noncardiac surgery varies by the type of procedure and the prevalence of coronary atherosclerosis in the study population. Incidence is < or = 1% with minor procedures and may exceed 10% with vascular operations. The case fatality rate continues to be 30% to 50%. Pathogenesis is not understood completely. Diagnosis is sometimes problematic, because less than 50% of patients complain of chest pain. In addition, a high frequency of notable but apparently innocent postoperative electrocardiograph changes limits the diagnostic use of the electrocardiogram. Fortunately, the creatine kinase MB isoenzyme retains its sensitivity and specificity for acute infarction in perioperative patients. Different approaches to preoperative risk assessment have been developed, including a summative cardiac risk index and a stratification system based on the likelihood that the most powerful risk factor (coronary artery disease) is present. Although many interventions have been recommended to lower perceived risk, none has been tested in a randomized controlled trial, and their comparative efficacy and safety is unknown.

Is blood pressure control necessary before surgery?

The need for blood pressure control before elective surgery depends on the degree and type of hypertension and the presence of other cardiovascular risk factors. Although blood pressure should be normalized in most patients for several months before surgery, mild to moderate diastolic or systolic hypertension do not place the patient at increased operative risk. Mild to moderate elevations should not be acutely controlled in the few days before surgery. Higher blood pressure elevations confer an increased operative risk and must be carefully controlled before surgery. Blood pressure control with certain antihypertensive medications confers a protective effect on the risk of intraoperative instability. The impact of preoperative control of hypertension in relationship to these variables is incorporated into useful recommendations for clinical practice.

Cardiac arrhythmias and myocardial ischemia after thoracotomy for lung cancer

The records of 598 patients undergoing a thoracic surgical procedure for lung cancer from 1975 through 1989 were reviewed for occurrence of cardiac arrhythmias and myocardial ischemic events. Atrial tachycardias occurred in 16% (94/598); atrial fibrillation was preponderant (87%), followed by supraventricular tachycardia and atrial flutter. Patients with recurrent episodes of dysrhythmias had a significantly higher mortality rate than those without episodes or with a single episode only (17% versus 2.4%; p less than 0.01). Transient ischemic electrocardiographic changes were documented in 23 patients (3.8%) and myocardial infarction in 7 (1.2%). An abnormal preoperative exercise test result and intraoperative hypotension were strongly associated with both dysrhythmia and ischemia (p less than 0.01). Pneumonectomy, ischemic changes on the electrocardiogram, and cardiac enlargement were also associated with arrhythmias (p less than 0.01). A weaker association (p less than 0.05) was found between postoperative arrhythmias and old myocardial infarction (greater than 6 months), arterial hypertension, and heart failure. Pulmonary function had no predictive value in this respect. A history of angina or old myocardial infarction was predictive of transient postoperative myocardial ischemia but not myocardial infarction. Despite improved anesthetic and monitoring techniques and more frequent use of the intensive care unit postoperatively in the last decade, the incidence of arrhythmias after thoracotomy has not decreased. More effective prevention is needed, particularly for patients with defined preoperative and perioperative risk factors.

Comparison of the findings on preoperative dipyridamole perfusion scintigraphy and intraoperative transesophageal echocardiography: implications regarding the identification of myocardium at ischemic risk

The evidence of myocardium at potential ischemic risk on preoperative dipyridamole perfusion scintigraphy was compared with that of manifest ischemia on intraoperative transesophageal echocardiography in 26 patients at high risk of a coronary event undergoing noncardiac surgery. The clinical outcome was also assessed. Induced intraoperative wall motion abnormalities were more common in patients and myocardial segments with, than in those without, a preoperative reversible perfusion defect (both p less than 0.05). Conversely, a preoperative reversible perfusion defect was more common in patients and segments with, than in those without, a new intraoperative wall motion abnormality (both p less than 0.05). Six patients, five with a reversible scintigraphic defect but only three with a new wall motion abnormality, had a hard perioperative ischemic event. Events occurred more often among patients with, than in those without, a reversible perioperative scintigraphic defect (5 [33%] of 15 vs. 1 [9%] of 11) but this difference did not reach significance (p = 0.14), probably owing to the sample size. Intraoperative wall motion abnormalities were all reversible and did not differentiate between risk groups; these findings were possibly influenced by treatment. These preliminary data support the known relation between reversible scintigraphic defects and perioperative events and identify another manifestation of ischemic risk in the relation between reversible scintigraphic defects and induced intraoperative wall motion abnormalities. The value of intraoperative echocardiography in identifying ischemia and guiding therapy in patients with a reversible scintigraphic abnormality should be further assessed.

Impact of aging on preoperative evaluation

Approximately 40% of physician office time and 33% of hospital time are devoted to patients 65 years of age or older. Over half of the older population requires some surgical intervention. Because of decreased physiologic reserve and increased number of underlying medical disorders, the older patient is at increased risk for intraoperative and postsurgical complications. Since cardiovascular, pulmonary, and renal complications are frequent in the elderly patient, the preoperative evaluation should emphasize these organ systems. Risk factors should be assessed initially by a focused history and physical examination and by simple tests. Additional diagnostic testing should be reserved for the patient who is not clearly at low or high risk. For optimal preoperative evaluation of the elderly patient, the physician should identify systemic disease, determine if the patient is receiving appropriate therapy, delineate the operative risks, and make recommendations that can potentially reduce the operative risks and postoperative complications.

Intraoperative blood pressure. What patterns identify patients at risk for postoperative complications?

While monitoring blood pressure is a routine part of intraoperative management, several methods have been proposed to characterize intraoperative hemodynamic patterns as predictors of postoperative complications. In this prospective study of a high-risk population of hypertensive and diabetic patients undergoing elective noncardiac surgery, one objective was to compare different approaches to the assessment of intraoperative hemodynamic patterns to identify those patterns most likely to be associated with postoperative complications. Twenty-one per cent of the 254 patients sustained cardiac or renal complications after operation. Patients with more than 1 hour of greater than or equal to 20-mmHg decreases in mean arterial pressure (MAP) or patients with less than 1 hour of greater than or equal to 20-mmHg decreases and more than 15 minutes of greater than or equal to 20-mmHg increases were at highest risk for postoperative complications. Together these two patterns had a 46% sensitivity rate and a 70% specificity rate in predicting postoperative complications. Using 20% change in intraoperative MAP produced results nearly identical to 20-mmHg changes. When the duration of 20-mmHg changes was accounted for, changes of a greater magnitude (e.g., 40 mmHg) were not significant independent predictors of complications. The use of the mean difference from preoperative MAP was misleading because patients who experienced both high and low MAPs tended to have nearly normal mean MAPs, but high complication rates. The absolute magnitude of intraoperative MAPs, regardless of the preoperative levels, also was evaluated. The overall mean intraoperative MAP was not a significant predictor of complications. Specific intraoperative MAPs (e.g., less than 70 mmHg and more than 120 mmHg) also were evaluated. While neither was a significant predictor, there was a trend for increased complications among patients whose MAPs decreased to less than 70 mmHg. Intraoperative blood pressure should be analyzed in relation to the patient's preoperative blood pressure. Prolonged changes of more than 20 mmHg or 20% in relation to preoperative levels were significantly related to complications.

Dynamic predictors of perioperative risk. Study of Perioperative Ischemia (SPI) Research Group

Reduction in perioperative cardiac morbidity requires new approaches to the management of cardiac surgery patients or high-risk noncardiac surgery patients. Studies that have addressed the perioperative dynamic predictors of risk suggest a number of conclusions. Intraoperative hypotension and tachycardia appear to be risk factors for perioperative cardiac morbidity, whereas the role of hypertension remains controversial. It has recently been shown that ischemia occurring prior to bypass doubles or triples the risk of subsequent myocardial infarction. Electrocardiographic determination of ST segment depression is used as an indicator of ischemia, as are changes in ventricular filling pressure. Although increases in left ventricular end-diastolic pressure have proved to be reliable indicators of ischemia, changes in pulmonary capillary wedge pressure or pulmonary artery diastolic pressure have not. Perioperative segmental wall-motion or wall-thickening abnormalities appear to provide the most sensitive clinical measure of ischemia. Preliminary data also suggest that transesophageal echocardiographic wall-motion abnormalities may predict adverse outcome following cardiac surgery. Recent information regarding dynamic predictors of perioperative cardiac morbidity stresses the importance of the postoperative period.

Preoperative characteristics predicting intraoperative hypotension and hypertension among hypertensives and diabetics undergoing noncardiac surgery

We prospectively studied patients with hypertension and diabetes undergoing elective noncardiac surgery with general anesthesia to test the hypothesis that patients at high risk for prognostically significant intraoperative hemodynamic instability could be identified by their preoperative characteristics. Specifically we hypothesized that patients with a low functional capacity, decreased plasma volume, or significant cardiac comorbidity would be at high risk for intraoperative hypotension and those with a history of severe hypertension would be at risk for intraoperative hypertension. Patients who had a preoperative mean arterial pressure (MAP) greater than or equal to 110, a walking distance of less than 400 m, or a plasma volume less than 3000 cc were at increased risk of intraoperative hypotension (i.e., more than 1 hour of greater than or equal to 20 mmHg decreases in the MAP). Hypotension was also more common among patients having intra-abdominal or vascular surgery, and among those who had operations longer than 2 hours. Patients older than 70 years or with a decreased plasma volume were at increased risk of having more than 15 minutes of intraoperative elevations of greater than or equal to 20 mmHg over the preoperative MAP in combination with intraoperative hypotension; this was also more common when surgery lasted more than 2 hours. Patients who had intraoperative hypotension tended to have an immediate decrease in MAP at the onset of anesthesia and were often purposefully maintained at MAPs less than their usual level during surgery with fentanyl and neuromuscular blocking agents. Patients who had intraoperative hyper/hypotension tended to have repeated elevations in MAP above their preoperative levels during the course of surgery, and such elevations precipitated interventions with neuromuscular blocking agents and/or fentanyl. Neither pattern was more common among patients who developed net intraoperative negative fluid balances. Both hypotension and hyper/hypotension were associated with increased renal and cardiac complications after operation. Patients with cardiac disease, especially diabetics, and those with negative fluid balances also had increased complications. Preoperative characteristics influence the susceptibility to intraoperative hypotension and hypertension, which are related to postoperative complications.

Intravenous nicardipine for treatment of intraoperative hypertension during abdominal surgery

Twenty patients, American Society of Anesthesiologists class I or II, who developed intraoperative hypertension (mean arterial pressure greater than 110 mm Hg) during abdominal surgery under balanced general anesthesia were randomly assigned to two groups. The nicardipine group (n = 10) received 5 mg of nicardipine hydrochloride, and the placebo group (n = 10) received 5 mL of nicardipine solvent injected intravenously over a 5-minute period in a blind manner. Arterial pressure was recorded for 15 minutes after the injection was started. If the mean arterial pressure did not decrease at least 10% at 15 minutes, the trial was opened and patients received 5 mg of nicardipine. None of the patients in the nicardipine group received nicardipine in an open manner, in contrast with 7 of the 10 patients in the placebo group (P less than 0.03, Fisher exact test). During both the blind period and the open trial, nicardipine induced a 34% decrease in systolic, diastolic, and mean arterial pressure. Minimal values of pressure were noted at 6 minutes; however, arterial pressure remained below the pre-nicardipine injection values and near preoperative values for 45 minutes. No severe hypotension was observed, but the nicardipine injection was stopped at 3 mg in two cases during the blind period because of the rate of pressure reduction. Heart rate remained unchanged during the decrease in arterial pressure in both groups. This study indicates that nicardipine is an effective, long lasting, and safe therapy for intraoperative hypertension during abdominal surgery.

Frequency and significance of early postoperative silent myocardial ischemia in patients having peripheral vascular surgery

Coronary disease causes the majority of perioperative complications after peripheral vascular surgery. Twenty-four patients with stable coronary disease undergoing peripheral revascularization were studied using continuous electrocardiographic monitoring to determine the incidence of perioperative asymptomatic myocardial ischemia and its relation to postoperative clinical ischemic events. Patients were monitored preoperatively (17 +/- 1 hours), intraoperatively and postoperatively (29 +/- 2 hours) using 4-channel calibrated amplitude-modulated units. Fifteen patients (63%) had early postoperative silent ischemia; 3 also had preoperative silent ischemia and 5 intraoperative transient ischemia. Patients with and without silent ischemia had similar clinical characteristics, perioperative antianginal medications and postoperative episodes of hemodynamic instability. However, 8 of 15 patients (53%) with silent ischemia had postoperative clinical ischemic events (2 had myocardial infarction, 2 had new congestive heart failure and 4 had new rest angina), versus only 1 of 9 patients (11%) without silent ischemia who had angina (p less than 0.05). Early postoperative silent myocardial ischemia occurs frequently after vascular surgery and is associated with postoperative clinical ischemic events.

The preoperative and intraoperative hemodynamic predictors of postoperative myocardial infarction or ischemia in patients undergoing noncardiac surgery

Among hypertensive and diabetic patients undergoing elective noncardiac surgery, preoperative status and intraoperative changes in mean arterial pressure (MAP) were evaluated as predictors of postoperative ischemic complications. Of 254 patients evaluated before operation and monitored during operation, 30 (12%) had postoperative cardiac death, ischemia, or infarction. Twenty-four per cent of patients with a previous myocardial infarction or cardiomegaly had an ischemic postoperative cardiac complication. Only 7% of those without either of these conditions sustained an ischemic complication. No other preoperative characteristics, including the presence of angina, predicted ischemic cardiac risk. Nineteen per cent of patients who had 20 mm Hg or more intraoperative decreases in MAP lasting 60 minutes or more had ischemic cardiac complications. Patients who had more than 20 mm Hg decreases in MAP lasting 5 to 59 minutes and more than 20 mm Hg increases lasting 15 minutes or more also had increased complications (p less than 0.03). Changes in pulse were not independent predictors of complications and the use of the rate-pressure product did not improve prediction based on MAP alone. In conclusion patients with a previous infarction or radiographic cardiomegaly are at high risk for postoperative ischemic complications. Prolonged intraoperative increases or decreases of 20 mm or more in MAP also resulted in a significant increase in these potentially life-threatening surgical complications.

The post-operative electrocardiogram and creatine kinase: implications for diagnosis of myocardial infarction after non-cardiac surgery

The objective of this study was to evaluate different approaches to the diagnosis of post-operative myocardial infarction. A total of 232 patients, mostly hypertensive and/or diabetic patients, who were undergoing elective non-cardiac surgery were evaluated pre-operatively. They were followed serially from the day of operation to discharge or the sixth post-operative day with daily clinical evaluations, electrocardiograms, creatine kinase and creatine kinase isoenzymes. In total 22% (51/232) of the patients had post-operative ECG changes in two or more leads. Only 1% developed new Q waves; most of the changes involved changes in the T or ST segments. Seventy percent of patients who had changes in their electrocardiogram were completely asymptomatic. The highest risk of ECG changes or symptoms occurred on the day of operation and the first post-operative day; evidence of post-operative infarction was infrequent after the second post-operative day. Creatine kinase levels rose an average of 250-300 IU on the first and second post-operative day (also the peak time for post-operative ECG changes), reducing its utility as an adjunct to the diagnosis of post-operative infarctions. Importantly, 52% (12/23) of the patients who had greater than or equal to 5% MB isoenzyme had neither ECG changes nor symptoms; the diagnosis of a myocardial infarction should not be made in these patients. In summary, most patients who experience ischemia or infarction post-operatively are asymptomatic. Symptoms should not be required for the diagnosis of post-operative infarction. Seemingly minor differences in criteria can produce major discrepancies in post-operative myocardial infarction rates (from 1 to 9%). The development of a final set of criteria will require further study but the diagnosis of post-operative infarction should probably be based on ECG changes, their duration and consistency, and the association of a positive MB fraction.

Perioperative hypertension. The primary care physician's role

Questions concerning the proper management of hypertension in surgical patients often arise in primary care practice. Currently available literature and our own clinical experience lead us to make the following recommendations. 1. Continue antihypertensive therapy up to and including the morning of surgery, when the dose should be given with a small sip of water. 2. If possible, adjust antihypertensive therapy so blood pressure is less than 160/90 mm Hg for at least two weeks prior to surgery. 3. Discontinue all monoamine oxidase inhibitors at least one week prior to surgery and substitute alternative antihypertensive or antidepressant medication as necessary. 4. Be attentive to the patient's preoperative volume status and any evidence of cardiovascular disease. 5. In patients with postoperative hypertension, search for specific aggravating factors and treat them primarily. 6. Discuss with the anesthesiologist any difficulties in blood pressure control.

Evaluation of the usefulness of enzymatic diagnosis of myocardial infarction in patients with acute arterial occlusion of the lower extremities

The serum activities of aspartate aminotransferase, lactate dehydrogenase, creatine kinase and estimated creatine kinase isoenzyme MB (CK-B) were investigated in 12 patients before and after revascularization of ischaemic lower extremities. All patients suffered from sudden lower limb arterial occlusion and underwent embolectomy through a small arteriotomy in the groin. The median serum activity of all four enzymes was elevated before surgery and further increased during the first 24-48 h after revascularization. Median serum activity of aspartate aminotransferase, creatine kinase and lactate dehydrogenase were continuously elevated 7 days after the operation. A high relative CK-B activity coincided in one patient with the development of electrocardiographic evidence of acute myocardial infarction. It is concluded that any of these four enzymes should be used with caution in the diagnosis of acute myocardial infarction before, during or after operation in patients who have sustained prolonged ischaemia of the lower extremities.

Anaesthetic considerations in percutaneous radiofrequency coagulation of the Gasserian ganglion

This study determined the cardiovascular effects of percutaneous radiofrequency coagulation of the Gasserian ganglion, performed under neuroleptanalgesia and intermittent ultrashort-acting barbiturate anaesthesia. Twelve ASA physical status class II patients were studied. Highly significant increases in mean heart rate and arterial blood pressure followed the insertion of the cannula electrode into the Gasserian ganglion (p less than 0.001). In six randomly assigned patients severe tachycardia and hypertension also accompanied the progress of the thermal lesion (p less than 0.0001). Three patients developed premature ventricular contractions, and two developed significant ST segment depression. Intravenous nitroglycerin, used during current generation, successfully controlled the hypertensive response in the other six patients. In percutaneous thermocoagulation of the Gasserian ganglion the patient's co-operation is essential. In addition to providing suitable operating conditions for both surgeons and patient, we should also be able to maintain normal and stable cardiovascular haemodynamics. Intravenous nitroglycerin used as an adjunct to light general anaesthesia safely maintained intraoperative normotension. It is also suggested that patients with coronary artery disease be adequately monitored and protected during the procedure.

Myocardial infarction following regional anaesthesia for carotid endarterectomy

From 1969 through 1982, 185 carotid endarterectomies were performed under regional anaesthesia on 153 patients. Of these patients, 38 (25 per cent) had suffered a previous myocardial infarction, 63 (41 per cent) had documented coronary artery disease, and 115 (75 per cent) had hypertension. Anaesthesia was provided by a superficial cervical plexus block. Monitoring consisted of measurement of direct arterial pressure and continuous display of the electrocardiogram. Oxygen was administered by nasal cannula throughout the procedure. Mean arterial pressure was elevated when necessary by infusion of phenylephrine. No patient in this study suffered an acute myocardial infarction. The only cardiac complications consisted of eight episodes of non-life-threatening dysrhythmias. We conclude that regional anaesthesia for carotid endarterectomy is associated with a low risk of perioperative myocardial infarction.

The role of the routine pre-operative chest X-ray in the elderly general surgical patient

In an unselected group of 233 patients aged 65 years and over undergoing non-cardiopulmonary surgery, 57·5% had some abnormality on routine pre-operative chest X-ray and 40·3% had an abnormality which was regarded as clinically significant. Of all patients, 32·2% subsequently required a postoperative chest film for diagnostic purposes, and in these cases the pre-operative X-ray was invaluable as a baseline. During the study period there were ten occasions where the discovery of an abnormality on a routine pre-operative chest film directly affected the treatment plan. Pre-operative chest radiology proved ineffective as a method of predicting postoperative respiratory complications and was of only limited effectiveness in predicting postoperative cardiac morbidity.

It is concluded that a routine pre-operative chest X-ray should be available in all elderly surgical patients (a) as a baseline measurement and (b) to exclude unsuspected disease. The prediction of postoperative cardiac and respiratory morbidity, however, is best achieved by non-radiological means.

Vectorcardiography in the diagnosis of postoperative myocardial infarction

Fifty-three consecutive patients, mean age 63 years, undergoing either peripheral vascular reconstructive surgery (n = 40) or lobectomy for bronchial carcinoma (n = 13) were examined pre- and postoperatively with conventional electrocardiogram (ECG), vectorcardiogram (VCG) and estimation of serum levels of aspartate aminotransferase, alanine aminotransferase, total lactic dehydrogenase and the heat-stable fraction of lactic dehydrogenase for the diagnosis of per/postoperative myocardial infarction (MI). Six patients (11%) developed signs of acute MI. In 2 patients whose ECG showed only unspecific changes, the VCG was decisive for the diagnosis. The serum enzyme values alone were of limited value in the diagnosis of per/postoperative MI.