Page 1538 - Hall et al (2015) Principles of Critical Care-McGraw-Hill

CHAPTER 111: Preoperative Assessment of the High-Risk Surgical Patient 1057

■ RECOMMENDATIONS The inability to improve pulmonary function despite adequate

Evaluation and treatment of patients presenting for noncardiac surgery therapy may be a more sensitive predictor of postoperative respiratory
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require careful attention to history, functional status, and assessment of failure. In a prospective study, those at risk of developing postoperative
clinical evidence of reversible cardiac failure or dysrhythmias, in addi- respiratory failure (defined as ventilator dependent >2 postoperative
tion to consideration of the timing and indications for the proposed days) were best identified by the failure of 48 to 72 hours of intensive
surgery. There is no doubt that clinical risk factors such as known preoperative preparation to improve FVC, forced expiratory flow over
ischemic heart disease, cardiac failure, diabetes, and renal insufficiency 25% to 75% of the expiratory cycle (FEF25-75), and maximal voluntary
are all independently documented to be associated with an increase in ventilation measured over 1 minute (MVV). Five percent of the study
perioperative cardiac morbidity. group developed postoperative respiratory failure, and all of these
Following published guidelines and analysis of the literature, it can be patients had an FEF25-75 and MVV less than 50% of predicted values,
recommended that noninvasive cardiac testing will not add to the clini- which had not improved with preoperative therapy. The perioperative
cians’ knowledge or improve risk stratification in patients with none of mortality in this subgroup was 60%.
clinical risk may have independent cardiac reasons for revascularization ■ EVALUATION OF RISK PRIOR TO PULMONARY RESECTION SURGERY
the above clinical criteria. Similarly, patients who present a significant
prior to proposed noncardiac surgery. This high-risk group should be Approximately 80% of patients presenting for lung cancer surgery have
intensively monitored in the perioperative period, including a stay in the concomitant chronic obstructive pulmonary disease (COPD) and 20%
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ICU for approximately 48 hours postoperatively. It is the intermediate- to 30% have severe pulmonary dysfunction. Pulmonary resection for
risk group of patients, presenting with one to two clinical risk factors, lung cancer has been associated with morbidity of 12% to 50% and
who will benefit most from noninvasive testing. Current treatment mortality of 2% to 12%. 49,50 A more recent retrospective analysis confirms
protocols suggest a significant clinical benefit from the appropriate that these figures have not been markedly improved (morbidity 20%,
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administration of β-blockers to select patients who are high risk. Some mortality 3%). In addition to the general preoperative preparation of
caution may need to be exercised regarding the duration of dose and the surgical patient, those patients who will require pulmonary resection
discontinuation of the drug. Due to recent negative reports regarding must have a preoperative estimation of postoperative pulmonary reserve.
the use of the pulmonary artery catheter, we cannot continue to sup- A multifactorial risk index was proposed for patients undergoing
port its routine use for high-risk patients following noncardiac surgery. thoracic surgery consisting of the cardiac risk index (CRI) and a pulmo-
Finally, there may be a role for TEE in noncardiac surgery. Resources, nary risk index (PRI), known as the cardiopulmonary risk-factor index
both financial and manpower, will dictate its integration. (CPRI). These pulmonary risk factors had previously been validated
as independent risk factors in univariate analysis. The CPRI assesses
obesity, cigarette smoking within 8 weeks of surgery, productive cough
ASSESSMENT OF RISK OF POSTOPERATIVE >45 mm Hg.
1
PULMONARY COMPLICATIONS within 5 days of surgery, FEV /FVC <70%, and Pa CO 2
Each of these factors was assigned one point. By combining the CRI
■ CLINICAL ASSESSMENT OF PULMONARY RISK (0-4) and the PRI (0-6), patients classified as having a CPRI of 4 or
greater were 17 times more likely to develop a postoperative pulmonary
Postoperative alterations in pulmonary physiology predispose to the complication than patients with a CPRI less than 4. 52
development of atelectasis (see Chap. 110). Marked decreases in forced Guidelines for prediction of outcome following lung resection are
53
expiratory volume in 1 second (FEV ) and forced vital capacity (FVC) generally based on preoperative whole lung function tests. MVV (% of
1
have been documented with serial postoperative pulmonary function predicted), FEV (liters), and FEV (% of predicted) have been most
1
1
tests. A reduction in functional residual capacity (FRC) of approxi- commonly used. Guideline values for proceeding with pneumonectomy,
42
mately 70% of basal values may occur by about 18 hours after surgery, lobectomy, or wedge/segmental resection are:
resulting in closure of small airways as FRC approximates closing • For pneumonectomy, MVV >55%, FEV >2 L, FEV1% >55%
volume. Progressive loss of functional lung tissue and intrapulmonary 1
43
shunting lead to worsening hypoxemia. • For lobectomy, MVV >40%, FEV >1L, FEV1% 40% to 50%
1
Many risk factors for the development of postoperative atelectasis • For wedge/segmental resection, MVV >35%, FEV >0.6 L, FEV1%
have been highlighted. Each of the following has been shown to predict >40% 1
postoperative atelectasis: preoperative severe bronchitis, FEV of more
1
than two standard deviations less than predicted, obesity, malnutri- Predicted postoperative FEV has been suggested as a sensitive predic-
1
tion, abdominal surgery, and age. Analysis of risk factors in a group of tor of postoperative pulmonary complications. For this measurement,
272 patients referred for preoperative assessment concluded that statisti- FEV and CT calculation of the number of preoperative functioning
1
cally significant predictors of postoperative pulmonary complications lung segments are required. Predicted postoperative FEV (ppoFEV )
1
1
) ≥45 mm Hg may then be calculated using the formula:
were partial pressure of arterial carbon dioxide (Pa CO 2
(OR = 61.0), FVC ≤1.5 L/min (OR = 11.1), maximum laryngeal height ppoFEV = Preoperative FEV × (Postop Functioning Segments /
1
≤4 cm (OR = 6.9), forced expiratory time ≥9 seconds (OR = 5.7), 1 Preop Functioning Segments)
smoking ≥40 pack-years (OR = 5.7), and body mass index (BMI)
≥30 kg/m (OR = 4.1). 44 Studies have suggested that if ppoFEV is <40% of predicted, this
2
1
Bedside pulmonary function tests (PFTs) such as spirometry have been may be a sensitive predictor of prohibitive operative risk and that resec-
used to identify patients at risk of developing postoperative pulmonary tion should not be considered. More recent work suggests that a low
complications, but lack of randomization, selection bias, and retrospective ppoFEV may indeed be a sensitive predictor of postoperative pulmo-
1
or unblended analysis of outcome invalidate conclusions. Spirometry as nary complications in lung cancer resection patients, but only in the
45
a screening procedure for high-risk patients remains unproven and its group without preexisting COPD. PpoFEV was not a significant predic-
1
routine use has been discouraged. The American College of Physicians tor of postoperative pulmonary complications in patients with a preop-
46
recommends preoperative pulmonary function testing in the following erative diagnosis of COPD. This may be due to the fact that while these
groups: patients with unexplained dyspnea, patients undergoing high-risk patients may have been losing lung tissue, a proportionally greater part
surgery (cardiac, thoracic, and upper abdominal), cigarette smokers, those of it was emphysematous and therefore less involved in gas exchange. 54
with symptoms of dyspnea on exertion, and patients undergoing head and In addition to these standard bedside tests, diffusion capacity of the
neck or orthopedic surgery with uncharacterized lung disease. All patients lung for carbon monoxide (DLCO) may be helpful. If there is evidence
undergoing lung resection should have PFTs. 47 of interstitial lung disease on chest x-ray or undue dyspnea on exertion,
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