Objective methods for preoperative assessment of functional capacity
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Tags: Perioperative Medicine,
Abstract
Notes
Annotations
(8/23/2022, 10:02:38 PM)
“Stress echocardiography, using either exercise stress echocardiography (ESE) or dobutamine stress echocardiography (DSE), may identify inducible ischaemia and thus the presence of significant coronary artery disease. These tests have very good ability to exclude coronary artery disease and identify individuals at low risk of postoperative cardiac complications (negative predictive value >0.95).” Go to annotation (Silvapulle and Darvall, 2022, p. 313)
“However, DSE is not a direct measure of functional capacity, and both ESE and DSE have modest sensitivity for identifying individuals at increased risk of 30-day postoperative cardiovascular complications (sensitivity of 0.68 and 0.79, respectively)” Go to annotation (Silvapulle and Darvall, 2022, p. 313)
“(i) _ VO2 peak (ii) Anaerobic threshold (iii) Ventilatory efficiency at the AT These variables are derived directly from CPET.” Go to annotation (Silvapulle and Darvall, 2022, p. 313)
“Oxygen uptake, or the rate of oxygen consumption ( _ V O2 per unit weight per unit time), is one of the most important variables in CPET. _ VO2 peak is the peak rate of oxygen uptake when the individual exercises up to symptom limitation or fatigue. _ VO2 peak reflects an individual’s ‘best effort’ and is distinct from _ VO2 max. _ VO2 max, a physiological endpoint, refers to maximum cardiac output and oxygen extraction and is identified by a plateau in oxygen uptake, despite an increase in workload.9 Most individuals do not reach their _ VO2 max during CPET, which limits the utility of _ VO2 max in clinical practice.” Go to annotation (Silvapulle and Darvall, 2022, p. 313)
“The thresholds associated with perioperative complications were originally derived from individuals undergoing lung tumour resection: _ VO2 peak > 20 ml kg1 min1 was associated with low risk of postoperative complications and” Go to annotation (Silvapulle and Darvall, 2022, p. 313)
“1 min1 was associated with significantly increased risk of postoperative pulmonary complications and mortality (8- and 13-fold increased risk, respectively, compared with _ V O2 peak > 20 ml kg” Go to annotation (Silvapulle and Darvall, 2022, p. 314)
“for individuals undergoing non-cardiac surgery, _ V O2 peak < 15 ml kg1 min1 is considered the threshold associated with increased risk of perioperative complications” Go to annotation (Silvapulle and Darvall, 2022, p. 314)
“6 As noted in Part 1 of this series, a _ V O2 peak of 15 ml kg1 min1 corresponds to 4.28 metabolic equivalents, which is considered to approximate the metabolic cost of major surgery.” Go to annotation (Silvapulle and Darvall, 2022, p. 314)
“During strenuous exercise, muscle oxygen requirements eventually exceed the capacity of the cardiopulmonary system to deliver oxygen, beyond which anaerobic metabolism takes place. The AT is the oxygen uptake ( _ VO2) at which anaerobic metabolism occurs. An AT < 11 ml kg1 min1 has been accepted as the threshold associated with increased perioperative risk in individuals undergoing non-cardiac surgery” Go to annotation (Silvapulle and Darvall, 2022, p. 314)
“slight variation of this threshold across surgical cohorts.7,11 Identification of AT is a complex process and, therefore, inter-rater variability is greater for AT than for _ VO2 peak.” Go to annotation (Silvapulle and Darvall, 2022, p. 314)
“E/ _ V CO2 at AT) Ventilatory efficiency is described by the _ VE/ _ VCO2 relationship, the ratio of minute ventilation to carbon dioxide production. This ratio refers to the volume of air that needs to be ventilated to exhale 1 L of carbon dioxide, per unit time. Therefore, _ VE/ _ V CO2 is a measure of the efficiency of gas exchange during exercise. In the assessment of dyspnoea, _ VE/ _ V CO2 at AT is often measured, as this identifies the point when ventilatory drive increases relative to workload. In general, a _ V E/ _ VCO2 at AT ratio > 34 defines ventilatory inefficiency.4Whereas _ V O2 peak is influenced by subject motivation, both AT and _ V E/ _ VCO2 at AT are effort-independent, and therefore are more reproducible measures of exercise capacity.” Go to annotation (Silvapulle and Darvall, 2022, p. 315)
“The 6MWT measures how far a patient can walk up and down a flat, 30 m corridor in 6 min. The measurements obtained include the 6-min walk distance (6MWD), oxygen saturation, heart rate, modified Borg dyspnoea scale and leg fatigue” Go to annotation (Silvapulle and Darvall, 2022, p. 315)
“The median 6MWD for healthy individuals is between 500 and 600 m.15 Studies evaluating the ability of the 6MWT to estimate functional capacity have used CPET-derived _ VO2 peak and AT as the reference standard for comparison.” Go to annotation (Silvapulle and Darvall, 2022, p. 315)
“The ISWT requires a subject to walk back and forth between two cones 10 m apart, at speeds that increase every minute by 0.17 m s1 in time to audio signals. The test is terminated when the subject fails to reach the next cone before the signal. Measurements obtained include the incremental shuttle walk distance (ISWD), heart rate, oxygen saturation, non-invasive systolic and diastolic blood pressures and modified Borg dyspnoea scale. Normal values for the ISWD vary with age, but are usually between 560 and 820 m in healthy individuals.” Go to annotation (Silvapulle and Darvall, 2022, p. 315)
“During CPET, the patient is required to perform incremental exercise on an upright cycle ergometer, whilst breathing through a mouthpiece. The patient follows a standardised protocol up to limitation by symptoms. The test provides assessment of the integrative exercise responses involving the cardiovascular, pulmonary and musculoskeletal systems. Data obtained during CPET include heart rate, non-invasive blood pressure, 12-lead ECG, oxygen uptake ( _ VO2 ), carbon dioxide production ( _ VCO2 ), oxygen saturation, gas flow rates and work rate.” Go to annotation (Silvapulle and Darvall, 2022, p. 317)
“The role of CPET includes measurement of exercise capacity in individuals with unknown or suspected poor exercise tolerance, differentiation of the cause for exercise limitation and risk stratification to assist with perioperative planning and appropriate allocation of resources” Go to annotation (Silvapulle and Darvall, 2022, p. 317)
“_ VO2 peak, AT and _ VE/ _ VCO2 at AT are the most commonly used variables for perioperative risk stratification. However, these are global measures of physical fitness and, therefore, are not useful in differentiating cardiovascular, respiratory, musculoskeletal or metabolic causes of exercise limitation.” Go to annotation (Silvapulle and Darvall, 2022, p. 317)
“for non-cardiopulmonary surgery, CPET may not accurately predict postoperative complications in individuals with poor functional capacity.” Go to annotation (Silvapulle and Darvall, 2022, p. 318)
“Overall, the following thresholds have been established for CPET-derived variables for prediction of in-hospital surgical morbidity, duration of stay in hospital, in-hospital mortality, 30-day mortality and 1-yr mortality (see Table 2): (i) _ VO2 peak 16.7e18.2 ml kg1 min1 provides poor-to-fair prediction of complications (AUROC ¼ 0.63e0.77) after major colorectal surgery.13,33 (ii) Anaerobic threshold 10.0e11.1 ml kg1 min1 provides poor-to-good prediction of complications (AUROC ¼ 0.63e0.85) after major abdominal surgery, colorectal resection, major urology surgery and hepatobiliary surgery.13,32,33 (iii) _ VE/ _ VCO2 at AT > 30.9 provides poor prediction of complications (AUROC ¼ 0.64e0.69) after major colorectal or urologic surgery” Go to annotation (Silvapulle and Darvall, 2022, p. 318)
“A 6MWD > 510 m was identified as the threshold that is associated with significantly increased chance of DFS, and it is likely that these individuals can proceed to surgery without further testing. However, there is no clear guidance on how individuals achieving 6MWD < 370 m should be investigated and managed in the perioperative period.” Go to annotation (Silvapulle and Darvall, 2022, p. 318)
“CPET is thought to be particularly useful in individuals expected to have a postoperative forced expiratory volume in 1 s (FEV1) < 40% of predicted; a _ V O2 peak < 10 ml kg1 min1 (or < 35% predicted) has been suggested as a prohibitive threshold for major lung resection.” Go to annotation (Silvapulle and Darvall, 2022, p. 318)