Questions and answers in periop medicine

Michael J. Maniaci, MD, ACP Member, reviewed data on cardiac and pulmonary perioperative exams and insulin and aspirin management at the Mayo Clinic Hospital Medicine 2017 conference.

As an expert in perioperative care, ACP Member Michael J. Maniaci, MD, fields a lot of questions about preoperative screening and medication management, from whether to check troponin and B-type natriuretic peptide (BNP) levels to what to do with a patient's insulin or aspirin regimen.

He offered some of his best answers during the Mayo Clinic Hospital Medicine 2017 conference. Dr. Maniaci, an assistant professor of medicine and chair of the division of hospital medicine at Mayo Clinic in Jacksonville, Fla., reviewed the latest data about cardiac and pulmonary perioperative exams as well as insulin and aspirin management.

Cardiac tests

There's good reason for hospitalists to worry about cardiac complications, with studies like the POISE trial showing that myocardial infarction (MI) occurs in up to 5% of surgery patients, Dr. Maniaci reported. “If you think of the amount of surgeries done in a day, one out of 20 is a huge number of patients possibly having an MI,” he said.

Dr Maniaci
Dr. Maniaci

Another challenge is that up to two-thirds of perioperative MIs are asymptomatic. “That's because people are on heavy doses of pain medications and heavy doses of antinausea medication. They don't have the typical symptoms, so unless you're doing an EKG at the time or they have an atypical symptom, you don't catch these,” he said.

It's natural then that there is widespread interest in using biomarkers to predict and identify cardiac surgical complications, but it's still uncertain how best to do that, according to Dr. Maniaci. “Every year I say, ‘Although the evidence on perioperative biomarker use is growing, the evidence is not so good as to which markers and what to do with them. Nobody has a plan on how to actually do this in an organized way,’” he said. “But this year, the Canadian Cardiovascular Society came out with some guidelines.”

The guidelines, published in the Canadian Journal of Cardiology in January 2017, recommend N-terminal proBNP (NT-proBNP) as a preoperative screening test for patients who are at least 65 years or have a Revised Cardiac Risk Index (RCRI) score of 1 or more.

“This is relatively new and confused some people when it first came out,” said Dr. Maniaci. “What they're saying is if your BNP is low, you're not at risk . . . But if your BNP is high—a NT-proBNP greater than 300 [pg/ml] or regular BNP (if you don't have proBNP) greater than 92 [pg/ml]—these are the people we have to monitor.”

Monitoring consists of checking troponin levels daily for 48 to 72 hours after surgery, a practice that the guideline also recommends after emergent or urgent surgery for all patients who are at least age 45 years or have a history of significant cardiovascular disease.

“So are we going to do this now? . . . There are a few problems,” said Dr. Maniaci. “First off, the screening pool is huge—everybody over the age of 65 getting a NT-proBNP. Looking at population health, what does that do when we consider specificity and false positives?”

Another concern is that the recommendations don't offer any steps to prevent perioperative MIs in high-risk patients. “If preoperative BNP is related to bad outcomes . . . shouldn't we be working that up before the surgery? There's no recommendations on that, at least from them right now, so we're basically saying, ‘Oops, it's high. Good luck and we'll check you afterward,’” he said.

Then there are the shortcomings of a troponin test for identifying postoperative MIs. “Other things can make troponins go up [aortic dissection, pulmonary embolism, stroke], so just because postoperative troponin goes up does not mean it's an MI,” said Dr. Maniaci. On the other hand, some patients may have a normal troponin test after surgery and then an MI later, since risk is elevated for 48 hours after surgery. “The Canadian Cardiovascular Society recommends one EKG in the [post-anesthesia care unit], but no serial EKGs,” he noted.

It's also uncertain at what troponin level physicians should take action. “One study had a troponin of 0.03 [ng/ml] as the cutoff, which is very, very low. My troponin right now is probably higher than 0.03 [ng/ml] giving this talk,” he said. “There are no established guidelines for what's the cutoff in this situation.”

A randomized trial applying these guidelines and related interventions is needed in order to answer these questions, Dr. Maniaci said. But in the interim, hospitalists need to be aware of the guidelines and their associated uncertainties. “You're going to start seeing this. Patients are going to start asking before surgery, ‘Should we do this?’” he said. “My personal recommendation to my staff is OK, this exists, it's important, but we need better guidelines.”

The American College of Chest Physicians last issued relevant guidelines in 2014, and Dr. Maniaci expressed hope that an update would arrive within the next year.

Pulmonary problems

There may be uncertainty surrounding the heart, but lungs get even less perioperative attention, according to Dr. Maniaci. “We focus on cardiac complications so much that we overlook bad lungs often,” he said. “I personally see a lot more respiratory distress postoperatively than MIs.”

A study, published in Surgery in November 2016, identified some ways to reduce the risk of postoperative respiratory complications. “If you prep the lungs a little bit, they do much, much better in the perioperative period,” he said. “This was a very important study to say there are very simple inspiratory muscle training exercises, aerobic exercises, resistance training, they can do at home before [surgery] and the risk reduction was significant for bad outcomes.”

Patients in the study began the program at least 10 days before surgery, but shorter-term efforts can also be helpful. “I am a hospitalist. Sometimes you don't have a lot of time, but even a couple days, I give them that incentive spirometer and have them up walking around,” Dr. Maniaci said.

Recent research has also shown how to identify patients at risk for respiratory complications: Check the expiratory flow of intubated patients during surgery. “Basically, the anesthesiologist inflates the patient's lungs, then they drop the positive end expiratory pressure [3 cm H2O] quickly and they see what the recoil is coming out of the lungs. If they recoil very quickly and the air comes out quickly, you don't have obstructive disease. If it comes out very slowly, that's an expiratory flow limitation,” he said.

Patients with expiratory flow limitation were found to have significantly higher rates of postoperative pneumonia and acute respiratory failure in a study published in Anesthesia & Analgesia in February 2017.

Another recent study to discuss with anesthesiologists was published in the British Journal of Anesthesiology in January 2017. It found that patients who received regional anesthesia rather than general anesthesia had a 24% lower risk of respiratory complications. “We can start pushing our anesthesiologists—’Hey, if a block can happen in our bad-lung patients, we should probably do it,’” said Dr. Maniaci.

After abdominal surgery, all patients may benefit from continuous positive airway pressure (CPAP), according to a study of abdominal surgery patients published in Lung in April 2016. “They found that a couple of hours of CPAP greatly reduced both pneumonia and atelectasis in the patients, mostly in pulmonary patients, but in general patients as well,” he said, noting that higher pressures and longer duration did not increase the benefits.

Finally, if patients develop hypoxemic respiratory failure after abdominal surgery, a study in the April 5, 2016, JAMA found that you should put them on noninvasive ventilation (NIV).

“Often what we do is they're on 2 L of oxygen, somebody turns them up to 4 L, then they go up to 6, then they go up to 8, and then somebody gets worried and they go up to 10,” said Dr. Maniaci. “If they're starting to go downhill, we run a little [bi-level positive airway pressure] on them; it seems to do much better than cranking up the oxygen.”

The patients on NIV in the study had a 12.4% reduction in reintubation and a 17.8% reduction in health care-associated pneumonia, he reported.

Managing meds

Too much cranking down is usually the mistake in inpatient basal insulin dosing, Dr. Maniaci explained in his review of diabetes medication management.

Oral diabetes medications should be held in the hospital, according to the latest guidelines from the American Diabetes Association, released in 2017. “Noninsulin injectables—go ahead and hold those as well, those things that you don't know what the heck they are anyway,” joked Dr. Maniaci.

However, inpatients still need their basal insulin. “If you think of the purpose of basal insulin, it's not to treat high mealtime levels, it's for your background metabolic rate,” he said. “You always get the call from the nurse, ‘Oh, it's 9 p.m. Their sugar is 100 [mg/dL]. Do you want me to give them this Levemir or Lantus? They're going to surgery in the morning. They're NPO after midnight.’ Well, aren't most of your patients NPO after midnight anyway when they go to bed? If basal insulin made you hypoglycemic, then all insulin-dependent diabetics would seize or go into a coma each night!”

Patients who are having bowel surgery and won't be eating for a long period of time should have their basal insulin dose lowered, but only to 75% to 85% of normal. But other surgical patients should receive their normal dose, Dr. Maniaci advised. Once they're eating, they should also receive mealtime doses.

“You can't just give a correction scale. Chasing your tail with a correction scale or sliding scale is not the way to go,” he said.

Medicine has been moving in circles regarding perioperative aspirin use as well, Dr. Maniaci said. “When I first became a hospitalist, it was ‘We know people on aspirin bleed, we know we have to transfuse them, but it's probably causing more good than harm.’” Then the POISE-2 trial, published in the New England Journal of Medicine in 2014, found higher rates of major bleeding in surgical patients who received aspirin.

“Everybody kind of backed off aspirin in 2014. Since then, we've looked back at the data and there are a few problems with this,” said Dr. Maniaci. Concerns included that many patients in the trial may have been at lower cardiac risk than previously thought, that some were taking another NSAID while taking aspirin, and that many in the aspirin cohort had their aspirin initially held only to have it restarted two to four hours before surgery.

“In the past couple of years, most of the national societies have basically said, ‘Well, if you're on it for no reason or primary prevention, you probably don't want to continue the aspirin. If you have a good reason—endarterectomy, people with bad carotids, or people that have had a stent placed—stay on it for sure. Secondary prevention and cardiovascular patients probably should stay on it,’” he said.

Most recently, an article published in the Annals of Surgery on May 1, 2017, found that the perioperative bleeding risk of surgical patients continued on aspirin may not have been as bad as first indicated in POISE-2. But the same study also found that the positive effects of aspirin—reductions of MI, stroke, or overall mortality—may not be significant overall, Dr. Maniaci reported.

For help with this decision making before surgery, he recommended an article published in the June 2017 Journal of Cardiothoracic and Vascular Anesthesia. “There's a neat little chart that goes through closed spaces and nonclosed spaces,” Dr. Maniaci said. Perioperative aspirin use is another issue that could use a large, randomized trial to look at outcomes in high-risk patients, he noted. “That clear data [on higher-risk patients alone] isn't out there, put together nicely.”