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THE ANESTHESIA CONSULTANT

Physician anesthesiologist at Stanford at Associated Anesthesiologists Medical Group

Richard Novak, MD is a Stanford physician board certified in anesthesiology and internal medicine.Dr. Novak is an Adjunct Clinical Professor in the Department of Anesthesiology, Perioperative and Pain Medicine at Stanford University, the Medical Director at Waverley Surgery Center in Palo Alto, California, and a member of the Associated Anesthesiologists Medical Group in Palo Alto, California.
emailrjnov@yahoo.com

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You’re a 55-year-old man with hypertension, scheduled for surgery for a right colon removal for colon cancer. How likely is your death within 30 days after surgery?

Higher than you would think.

Your 30-day morality following this inpatient surgery is 1.2%. What can we do to improve myocardial injury after noncardiac surgery? Read on…

Dr. Daniel Sessler, Chairman of the Department of Outcomes Research at the Anesthesia Institute of the Cleveland Clinic, spoke at the Stanford Anesthesia Grand Rounds last week. His lecture, titled “Perioperative Myocardial Injury,” answered the questions above. Let me share what Dr. Sessler had to say:

1. Myocardial injury after noncardiac surgery, abbreviated as MINS, is a common, silent, and deadly problem. Dr. Sessler described mortality related to surgery as the third leading cause of death in America, behind cardiovascular disease and cancer, and he cited myocardial injury as the leading cause of death after surgery.
2. Devereaux, Sessler, and colleagues measured postoperative hsTnT (high sensitive troponin T) in 21,842 patients over the age of 45 who had inpatient noncardiac surgery at 23 medical centers in 13 countries.¹ (For my nonmedical readers: hsTnT or cardiac troponin is a biomarker for acute myocardial infarction, i.e. heart attack.) Two hundred sixty-six patients died within 30 days after surgery, for an overall mortality rate of 1.2%. A total of 3904 patients had elevated hsTnT, diagnostic for MINS, for an overall incidence of tropinin elevation = 18% of the patients. Ninety-three percent of these patients had no ischemia-related symptoms, and would not have been detected without the hsTnT measurements.
3. Puelacher published similar data in an older population (all patients over the age of 65).² He studied postoperative hsTnT levels in 2018 consecutive inpatients and found perioperative myocardial injury (PMI) occurred in 397 (16% of the patients). Only 24 (6% of the patients) had typical chest pain, and only 72 (18% of the patients) had ischemic symptoms. The 30-day mortality was 8.9% for patients with PMI, compared to 1.5% for patients without PMI.
4. hsTnT isn’t commonly measured in current practice, which means the majority of MINS patients go undiagnosed. Sessler recommended that all patients diagnosed with MINS be seen by a cardiologist, to consider further diagnostic or therapeutic intervention. He specifically mentioned the possibilities of statin and/or aspirin therapy, as well as smoking cessation and weight loss.
5. Sessler suggested that a future approach to MINS detection would be to measure postoperative hsTNT for three days in every inpatient noncardiac surgery patient over 65 years old, and in those over 45 with one or more cardiovascular risk factor.
6. What about preoperative clearance for noncardiac surgery? Sessler described exercise tolerance and the echocardiogram cardiac stress test as two inaccurate screening tools. He rated the two most effective screening tools as the Revised Cardiac Risk Index (see below), and the preoperative measurement of BNP (Brain Natriuretic Peptide).
7. The Revised Cardiac Risk Index (RCRI) evaluates these 6 patient factors:

■ High-Risk Surgery – the following surgeries are deemed high risk for perioperative cardiac complications:

-­ Intraperitoneal

– Intrathoracic

– Suprainguinal vascular

■ History of ischemic heart disease – characterized by either a history                                     of a positive test, a diagnosed MI, current chest pain suspicion of                                                 myocardial ischemia, nitrate therapy, or evidence of                                                             pathological Q waves on electrocardiogram.

■ History of congestive heart failure – described as the presence of                                     either:

– Pulmonary edema, bilateral rales or S3 gallop;

– Paroxysmal nocturnal dyspnea;

– A CXR showing pulmonary vascular redistribution.

■ History of cerebrovascular disease – e.g. a prior TIA or stroke.

■ Pre-operative insulin treatment.

■ Pre-operative creatinine more than 2 mg/dL.

Positive findings of these factors define 4 classes of postoperative                                     cardiac complication percentage rates:

■ 0 factors – Class I – risk 0.4%;

■ 1 factor – Class II – risk 0.9%;

■ 2 factors – Class III – risk 6.6%;

■ 3 to 6 factors – Class IV – risk 11%. 

8. Preoperative BNP concentration is a powerful independent predictor of perioperative cardiovascular complications.³ At best, clinicians can utilize both a low score in the preoperativeRevised Cardiac Risk Index plus a low value of the BNP or the N-terminal proB-type natriuretic peptide (NT-proBNP) plasma level.⁴ Sessler stated that a BNP test costs 1/20^th as much as an echo stress test, and is more accurate in predicting postoperative cardiac mortality. He stated that a NT-proBNP level of < 300 ng/mL correlated well with a safe perioperative cardiovascular course.
9. Elevated preoperative troponin or hsTnT concentrations were also significantly associated with postoperative MI and long-term mortality after noncardiac surgery.⁵
10. Metoprolol, aspirin, and clonidine all failed as preoperative interventions to decrease cardiac risk. Metoprolol decreased postoperative myocardial infarction, but there were more deaths and an increased rate of stroke in the metoprolol group than in the placebo group.⁶ Aspirin before surgery and throughout the early postsurgical period had no significant effect on the rate of death or nonfatal myocardial infarction, and increased the risk of major bleeding.⁷ Low-dose clonidine did not reduce the rate death or nonfatal myocardial infarction, and increased the risk of clinically important hypotension and nonfatal cardiac arrest.⁸
11. Eliminating nitrous oxide from the anesthetic regimen had no effect in decreasing myocardial injury.⁹
12. Intraoperative hypotension correlated with postoperative myocardial injury. Mascha studied the time-weighted average intraoperative mean arterial pressure (TWA-MAP), and found that lower mean arterial pressure strongly correlated with mortality.¹⁰ Sessler stated that a mean blood pressure of 50 torr for even one minute was a risk factor for postoperative myocardial injury. Targeting a specific systolic blood pressure reduced the risk of postoperative organ dysfunction.¹¹
13. Sessler stated that 1/3 of intraoperative hypotension occurred during the time between induction of anesthesia and time of the surgical incision. By analyzing large databases from electronic anesthesia recording systems, hypotension was documented during this time period when general anesthesia lacked any surgical stimulus to keep blood pressure elevated. Sessler’s recommendation was to maintain the MAP > 65 torr throughout noncardiac surgery.
14. The use of vasopressors to treat hypotension was safe.
15. Tachycardia was not a risk factor. “It hardly matters,” Sessler said.
16. Preoperative angiotensin-converting-enzyme inhibitors (ACE inhibitors), e.g. lisinopril, Lotensin, or Altace, and Angiotensin II receptor blockers (ARBs), e.g. Diovan or Cozaar, were risk factors for intraoperative hypotension and cardiovascular morbidity. Roshanov studied data from 14,687 patients aged 45 years or older for inpatient noncardiac surgery.¹² Four thousand eight hundred and two of these patients were taking ACE inhibitors or ARBs preoperatively. The patients who withheld their ACE inhibitors/ARB drugs in the 24 hours before surgery were less likely to suffer the outcomes of death, stroke, or myocardial injury. The authors recommended that patients withhold these drugs for 24 hours before surgery.

Dr. Sessler closed his lecture with the following recommendations:

• In the future, clinicians should measure high-sensitivity troponin (hsTnT) for three days postoperatively on inpatient surgery patients of age > 65, or patients age >45 with one cardiovascular risk factor. Elevated shTnT will identify patients who with MINS, and these MINS patients should be referred for cardiology/internal medicine follow up.
• In the future, clinicians should screen for preoperative cardiovascular risk by a combination of the BNP and hsTnT assays prior to surgery.
• There is no known preoperative medical prophylaxis against MINS.
• Maintain intraoperative mean arterial pressure > 65.
• Hold ACE inhibitors/ARBs for 24 hours prior to surgery.

One of our professors asked Dr. Sessler if the current practice at the Cleveland Clinic included measuring preoperative BNP and three-day postoperative hsTnT. Sessler’s answer was, “not yet, but we’re working on it.”

What about your practice and mine?

This is a new topic and a cutting edge issue to most anesthesiologists, with the key studies only published in the last year. I’m impressed by the MINS data, and I don’t want any patient of mine joining the MINS mortality list. I already withhold ACE inhibitors/ARBs for 24 hours preoperatively. I will continue to be vigilant to maintain MAP > 65, using vasopressors as necessary. I currently use the Revised Cardiac Risk Index as well as cardiology consultations as indicated to screen patients preoperatively. At the present time both the cardiologists and I depend on exercise tolerance history and echo treadmill tests for preoperative cardiac clearance. I expect in the near future our healthcare systems will adopt the standards of checking BNP preoperatively and hsTnT for three days postoperatively for inpatient surgery patients of age > 65, or patients age >45 who have one cardiovascular risk factor. Stay tuned for future recommendations.

References:

1. Devereaux PJ et al. Association of Postoperative High-Sensitivity Troponin Levels With Myocardial Injury and 30-Day Mortality Among Patients Undergoing Noncardiac Surgery. 2017Apr 25;317(16):1642-1651.
2. Puelacher C et al. Perioperative Myocardial Injury After Noncardiac Surgery. Circulation. 2018;137, 1-12.
3. Rodseth RN et al. The prognostic value of pre-operative and post-operative B-type natriuretic peptides in patients undergoing noncardiac surgery: B-type natriuretic peptide and N-terminal fragment of pro-B-type natriuretic peptide: a systematic review and individual patient data meta-analysis. J Am Coll Cardiol.2014 Jan 21;63(2):170-80.
4. Vetrugno L et al. The Possible Use of PreoperativeNatriuretic Peptides for Discriminating Low Versus Moderate-High Surgical Risk Patient. Semin Cardiothorac Vasc Anesth. 2018 Jan 1.
5. Nagele P et al. High-sensitivity cardiac troponin T in prediction and diagnosis of myocardial infarction and long-term mortality after noncardiac surgery. Am Heart J.2013 Aug;166(2):325-332.
6. Devereaux PJ et al. Effects of extended-release metoprolol succinate in patients undergoing non-cardiac surgery (POISE trial): a randomised controlled trial. 2008 May 31;371(9627):1839-47.
7. Devereaux PJ et al. Aspirin in patients undergoing noncardiac surgery. N Engl J Med.2014 Apr 17;370(16):1494-503.
8. Devereaux PJ et al. Clonidine in patients undergoing noncardiac surgery. N Engl J Med.2014 Apr 17;370(16):1504-13.
9. Myles PS et al. The safety of addition of nitrous oxide to general anaesthesia in at-risk patients having major non-cardiac surgery (ENIGMA-II): a randomised, single-blind trial. Lancet. Volume 384, No. 9952, October 2014, 1446-1454.
10. Mascha EJ. Intraoperative Mean Arterial Pressure Variability and 30-day Mortality in Patients Having Noncardiac Surgery. 2015 Jul;123(1):79-91.
11. Futlier E et al. Effect of Individualized vs Standard Blood Pressure Management Strategies on Postoperative Organ Dysfunction Among High-Risk Patients Undergoing Major Surgery: A Randomized Clinical Trial. 2017Oct 10;318(14):1346-1357.
12. Roshanov PS et al. Withholding versus Continuing Angiotensin-converting Enzyme Inhibitors or Angiotensin II Receptor Blockers before Noncardiac Surgery: An Analysis of the Vascular events In noncardiac Surgery patIents cOhort evaluatioN Prospective Cohort. 2017Jan;126(1):16-27.