Medical clearance prior to non-cardiac surgery

A recent international study found that a structured questionnaire, Duke Activity Status Index (DASI) outperformed other measures in predicting pre-operative risk for high risk patients undergoing major noncardiac surgery (see medical clearance for surgery lancet2018 in dropbox, or Wijeysundera DM. Lancet 2018; 391: 2631–40​).

Details:

-- 25 hospitals (5 in Canada, 7 in the UK, to Australia, 3 in New Zealand) with 1401 patients were included in this prospective cohort study, from 2013 to 2016

-- patients all had one or more risk factors for cardiac complications in surgery: history of heart failure, stroke, diabetes, or coronary artery disease

-- median age 65 years, 39% female, 91% reclassified as American Society of Anesthesiologists Physical Status (ASA-PS) 2 or 3 (mild or severe systemic illness, but not one that is a constant threat to life)

-- comorbidities: CAD 12%, diabetes 19%, hypertension 56%, current or recent smoker 15%, COPD 13%, significant arthritis 21%, significant malignancy 43%, eGFR<60 11%.

-- preoperative medications: b-blocker 17%, ACE inhibitor or ARB 38%, aspirin 24%, calcium blocker 20%

-- anesthesia: 54% general, 15% regional, 31% general plus regional

-- most patients underwent major abdominal, pelvic or orthopedic procedures

-- presurgical risk was assessed by:

    -- subjective assessment of functional capacity by anesthesiologists, in units of metabolic equivalents (METs) of tasks, graded as poor (<4), moderate (4-10), or good (>10)

    -- DASI questionnaire (see http://www.phsoregon.org/newsletters/ecardiovascular-beat/assets/downloads/Duke-Activity-Status-Index.pdf ), scores 0-58.2.  the results can be converted to METs, as in this URL

    -- symptom-limited cardiopulmonary exercise testing (CPET)

    -- NT pro-BNP concentrations (as a marker of cardiac dysfunction, including MI and ischemia)​

-- after surgery, patients had daily EKGs and measurements of serum troponin and creatinine, for 3 days or until hospital discharge

-- primary outcome: myocardial infarction or death within 30 days after surgery

-- secondary outcome: death within one year of surgery

Results:

-- 28 patients (2%) died or had an MI within 30 days of surgery

-- the added value of the following 4 tests, over and above the "baseline model" of the Revised Cardiac Risk INdex (RCRI) score (a composite of history of CAD, HF, cerebrovasc disease, treatment with insulin, CKD, high-risk surgery):

    -- subjective assessment by anesthiologists:

        --sensitivity of 19.2% (14.2-25%) and 94.7% specificity (93.2-95.9%) for identifying inability to attain 4 METs during CPET

        ​--there was no significant correlation between subjectively assessed preop functional capacity and any of the study outcomes

    -- DASI score: 

        --predicted the primary outcome (30-day death or MI), adjusted odds ratio 0.96 (0.83-0.99), p=0.03 (the only assessment to do so!!)

        --DASI also predicted 30-day death or myocardial injury (sustained by 176 patients, 13%), p=0.05

        ​--peak oxygen consumption was positively correlated with DASI score and negatively correlated with NT pro-BNP

        --DASI had negative correlation with  NT pro-BNP (p<0.001)

    ​    --the only correlation between the subjective assessment and DASI scores was between those who had a poor subjective score (<4 METs) and a good one (>10 METs) did have a statistically significant difference in their DASI scores

    -- NT pro-BNP: 

        --did improve prediction of 30-day myocardial injury or death (p=0.003), and 1-year death (p=0.001)

    -- lower peak oxygen: 

        --only predicted in-hospital moderate or severe complications, experienced by 194 (14%) of the patients (p=0.007)

Commentary:

-- the Am College of Cardiol and Am Heart Assn recommend that patients can have intermediate or major non-cardiac surgery is they are capable of at least 4 METs of activity (see http://www.onlinejacc.org/content/64/22/e77 )

-- this study found that preoperative subjectively-assessed functional capacity was not useful for predicting postoperative risk; subjective assessment "correctly identified only 16% of patients who achieved a peak less than 14 mL/kg per min, which is consistent with less than 4 METs"

-- also, the more extensive CPET did not add much to DASI

-- further studies are needed to define optimal DASI risk score, as well as the best cutpoint for NT pro-BNP levels

-- the DASI score does require answering some questions which may not apply to many patients (though perhaps the patient could guess?? not sure how accurate that would be)

-- it is unclear exactly how to interpret come of these findings: are we looking at the wrong CPET variables (maybe  low peak oxygen consumption is not the best predictive variable, though it has been shown to be important) and does this explain why DASI was a better predictor than CPET?? 

-- there were relatively few primary outcomes, though their results are pretty similar to more recent studies in high-income countries.

-- the authors' conclusion was that though there was a correlation between low DASI scores and high NT pro-BNP levels, this corelation was in the "slight-to-fair" range, suggesting that enhanced preoperative assessment might include a combination of the 2.

so, this article raises a few points for primary care (since we are the ones frequently called upon to do pre-op assessments):

-- the standard functional assessment, involving asking patients for example if they can walk up a flight of stairs (equivalent to 4 METs), seems to be woefully inadequate

-- the DASI questionnaire seems to add the most to the preop evaluation (see http://www.phsoregon.org/newsletters/ecardiovascular-beat/assets/downloads/Duke-Activity-Status-Index.pdf ), though cutpoints need to be clarified prospectively (we can probably use the calculated cut point of 4 METs???)​

-- it seems that NT pro-BNP may be a useful addition, mostly finding increased myocardial injury post-op. though this did not seem to translate into increased MI or death, it might be a useful indicator that the patient is at higher cardiovascular risk and more attention should be paid to risk factor modification. and it might be useful anyway to check this prior to surgery in those with known heart failure, or even all with known coronary artery disease

geoff​

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