PRE-OPERATIVE ASSESSMENT OF THE RESPIRATORY SYSTEM REGISTRAR: Dr Aucamp CONSULTANT: Dr Prins INTRODUCTION Goal: Determine the risk to the patient Why: • Contribute significantly to perioperative morbidity and mortality • Costly • Longest length of stay Estimation of risk should be a standard element of all preoperative medical evaluations. DEFINITION Differing definitions account for the variability in frequency Proposed definition by O'Donohue: A pulmonary abnormality that produces identifiable disease or dysfunction that is clinically significant and adversely affects the clinical course • • • • • Atelectasis Infection, including bronchitis and pneumonia Prolonged mechanical ventilation and respiratory failure Exacerbation of underlying chronic lung disease Bronchospasm4 O'Donohue, WJ. Postoperative pulmonary complications: When are preventive and therapeutic measures necessary? Postgrad Med 1992; 91:167. EFFECT OF MEDICAL CONSULTATION ON SURGICAL OUTCOMES No study has shown a decrease in perioperative morbidity associated with medical consultation9 The practice of medical consultation is widespread Assuming consultants make evidence-based recommendations, it is reasonable to infer that consultation will improve the care of the surgical patient..... if consultative recommendations are implemented Phy, MP, Vanness, DJ, Melton LJ, 3rd, et al. Effects of a hospitalist model on elderly patients with hip fracture. Arch Intern Med 2005; 165:796. GENERAL PRINCIPLES OF CONSULTATION • Determine the question and respond to it • Establish the urgency of the consultation and provide a timely response. • “Look for yourself”; confirm the history and physical examination and check test results. • Be as brief as appropriate; be definitive and limit the number of recommendations. • Be specific, including medication details. • Provide contingency plans; anticipate potential problems and questions. • “Honour thy turf”; don't steal other physician's patients. • Teach with tact; consult, don't insult. • Talk is cheap and effective; direct verbal communication is crucial. • Follow-up to ensure that recommendations are followed PERIOPERATIVE PULMONARY PHYSIOLOGY Complications follow logically as an extension of normal perioperative pulmonary physiology Thoracic and upper abdominal surgery is associated with a reduction in lung volumes: • VC is reduced by 50 to 60 % and may remain decreased for up to one week. • FRC is reduced by about 30% Important factors: • Diaphragmatic dysfunction • Postoperative pain and splinting Reduction of the FRC below closing volumes contributes to atelectasis, pneumonia, and V/Q mismatching Microatelectasis PERIOPERATIVE PULMONARY PHYSIOLOGY Decreased TV, loss of sighing breaths, and increase in RR occur after abdominal and thoracic surgery Residual effects of anesthesia itself and postoperative opioids Inhibition of cough and impairment of mucociliary clearance Lower abdominal surgery to a lesser degree. Reductions in lung volumes are not seen with surgery on the extremities RISK FACTORS PATIENT RELATED • Age • Chronic lung disease • Asthma • Smoking • Obesity • Obstructive sleep apnoea • Pulmonary hypertension • Heart failure • General health status SURGERY RELATED • Surgical site • Duration of surgery • Type of anesthesia • Type of neuromuscular blockade PATIENT RELATED FACTORS AGE • • • ? influence of age as an independent predictor of postoperative pulmonary complications Early studies were not adjusted for overall health status or known pulmonary disease ACP review made the novel observation that age >50 years was an important independent predictor of risk CHRONIC LUNG DISEASE • • • • • Early reports estimated complications at relative risks between 2.7 and 6.0 A more recent systematic review, found the impact less than previously estimated Among studies that used multivariable analysis to adjust for patient-related confounders, the odds ratio 2.3614 There appears to be no prohibitive level of pulmonary function below which surgery is absolutely contraindicated Benefit of surgery must be weighed against the known risks PATIENT RELATED FACTORS ASTHMA • Well controlled patients with peak flow of >80% of predicted or personal best can proceed to surgery at average risk16 SMOKING • • • • • Risk factor and has been demonstrated since 1944 Increased risk even among those without chronic lung disease Relative risk 1.4 to 4.3 Risk declines only after eight weeks of preoperative cessation Paradoxically, those who had stopped smoking less than eight weeks earlier had a higher risk than current smokers17 OBESITY • Obesity should not affect patient selection for otherwise high-risk procedures PATIENT RELATED FACTORS OBSTRUCTIVE SLEEP APNOEA • • • While the literature is still emerging, we should consider OSA to be a probable risk factor OSA increases the risk of critical respiratory events immediately after surgery, including early hypoxemia and unplanned reintubation17 Patients with an ODI4% of >5 were more likely to have postoperative respiratory (8 versus 1%) complications PULMONARY HYPERTENSION • • • • • Increases pulmonary complication rates after surgery, regardless of the underlying etiology History of pulmonary embolus NYHA functional class ≥ 2 Intermediate or high risk surgery Duration of anesthesia > 3 hours. PATIENT RELATED FACTORS HEART FAILURE • • • Higher risk in HF than in COPD Suggested by data from the ACP review, with odds ratio of 2.93 for HF patients and 2.36 for patients with COPD14 The original Goldman cardiac risk index has been shown to predict postoperative pulmonary as well as cardiac complications21 GENERAL HEALTH STATUS • • • • • Functional dependence and impaired sensorium each increase risk ASA classification correlates well with pulmonary risk and is one of the most important predictors Patients with significant preexisting lung disease would be classified in a higher ASA class ASA class >2 confers a 4.87 fold increase in risk14. The inability to exercise predicts 79% of pulmonary complications15. PROCEDURE RELATED RISK FACTORS SURGICAL SITE • • • • Single most important factor in predicting the overall risk of postoperative pulmonary complications Significantly higher for thoracic and upper abdominal surgery than for lower abdominal and all other procedures The impact of laparoscopic surgery on pulmonary complication rates is not well established Lower pulmonary complication rates expected but not evaluated as an endpoint DURATION OF SURGERY • • Surgical procedures lasting more than 3-4h are associated with a higher risk A less ambitious, briefer procedure should be considered in a very high risk patient PROCEDURE RELATED RISK FACTORS TYPE OF ANESTHESIA • • • • Conflicting data with regard to spinal or epidural anesthesia vs general anesthesia A comprehensive review was done and it appears likely that GA leads to a higher risk than do epidural or spinal anesthesia Further studies are required to confirm this observation Regional nerve block is associated with lower risk and should be considered when possible for high risk patients TYPE OF NEUROMUSCULAR BLOCKADE • • Pancuronium, a long-acting neuromuscular blocker, leads to a higher incidence of postoperative residual neuromuscular blockade Higher incidence of postoperative pulmonary complications in those patients with residual neuromuscular blockade PREOPERATIVE CLINICAL EVALUATION A careful history and physical examination are NB! History of: • Exercise intolerance • Chronic cough • Unexplained dyspnoea The physical examination may identify findings suggestive of unrecognized pulmonary disease: • Decreased breath sound • Dullness to percussion • Wheezes • Rhonchi • Prolonged expiratory phase Which may predict an increase in the risk of pulmonary complications PREOPERATIVE PULMONARY FUNCTION TESTING • The value of routine preoperative pulmonary function testing remains controversial • There is consensus that all candidates for lung resection should undergo preoperative pulmonary function testing. • Such testing should be performed selectively in patients undergoing other surgical procedures LUNG RESECTION INITIAL EVALUATION • Detailed medical history, incl. coexisting disease to ensure the optimal treatment of that disease • History should include functional capacity and the degree of limitation of activity. • A history of smoking or COPD may lead to preoperative therapeutic interventions such as bronchodilators and/or steroids • The physical examination should include an evaluation for signs of metastatic spread and the presence of HF and PHT • All of these might change the treatment mode and determine that the patient may not be a suitable surgical candidate. PULMONARY SPECIFIC EVALUATION STAGE I ASSESSMENT Spirometry • Spirometry is a simple, inexpensive, standardized and readily available test • FEV1, FVC, FEF mid expiratory phase (FEF25-75%) and MVV have been extensively studied • FVC reflects lung volume, while FEV1 and FEF25-75% reflects airflow • MVV reflects muscle strength and correlates with postoperative morbidity • FEV1 is regarded as being the best for predicting complications of lung resection in the initial assessment Diffusion Capacity • DLCO reflects alveolar membrane integrity and pulmonary capillary blood flow in the patient’s lungs • Retrospective studies have reported that actual DLCO (as % of the predicted value) and predicted postoperative DLCO are important predictors of mortality and postoperative complications Arterial Blood Gas Levels • Arterial blood gas levels have not been extensively studied as predictor of postoperative complications • Hypercapnia (PCO2 >45 mmHg) in arterial blood has been a relative contraindication to lung resection • A few studies however did not find that a PCO2 > 45mmHg was predictive of postoperative complications PULMONARY SPECIFIC EVALUATION INCREASED POSTOPERATIVE COMPLICATIONS AND MORTALITY For pneumonectomy: FEV1 MVV DLCO FEF25-75% < 2L or < 60% of predicted < 55% of predicted < 50% of predicted < 1.6L/s For lobectomy: FEV MVV DLCO FEF25-75% < 1L < 40% of predicted < 50% of predicted < 0.6L/s For wedge resection : FEV1 DLCO < 0.6L < 50% of predicted If values more than required for pneumonectomy above are achieved, no further testing is indicated and that the patient is at low risk Datta, D, Lahiri, B. Preoperative evaluation of patients undergoing lung resection surgery. Chest 2003; 123:2096. PULMONARY SPECIFIC EVALUATION STAGE II ASSESSMENT Quantitative ventilation-perfusion scan or Differential lung scan • The percentage of radioactivity contributed by each lung correlates with the contribution to the function • Normally the right lung contributes 55% and the left lung 45% of lung function. • The predicted FEV1 of residual lung following surgery can be calculated Patients, who undergo a differential lung scan may be allowed to undergo surgery if: • Predicted postoperative FEV1 > 40% of predicted • Predicted postoperative DLCO > 40% of predicted Patients whom do not meet these criteria should undergo further evaluation before surgery can be undertaken • Patients with a predicted postoperative FEV1 <30 percent predicted are particularly singled out Other tests assessing differential lung function include • Bronchospirometry, • lateral position testing and • total unilateral pulmonary artery occlusion (invasive, special equipment, technical expertise PULMONARY SPECIFIC EVALUATION STAGE III ASSESSMENT Exercise testing stresses the entire cardiopulmonary and oxygen delivery system • Good estimate of cardiopulmonary reserve • HR, BP, ECG and O2 saturation are measured, as well as the measurement of exhaled gasses. • The VO2; VO2max; carbon dioxide output and minute ventilation can be measured • VO2max or peak VO2 indicates whether the patient has the reserve to counter the multiple physiologic stresses that accompany surgery Two major types of exercise tests have been used • Fixed exercise challenge, in which a sustained level of work is performed • Incremental exercise testing in which the work is sequentially increased to a desired end point Stair climbing: For many years, surgeons have utilized stair climbing as a preoperative screening tool. Though poorly standardized, this form of testing has been shown to identify patients at increased risk for lung resection. • • • Attainment of a lower altitude (less than 12m) on a symptom-limited stair climbing test was associated with increased cardiopulmonary complications, mortality, and cost, compared with climbing to a higher altitude (22m) Those who were able to climb > 8 flights of stairs, at their own pace, were less likely to experience complications than those who could climb < 7 flights of stairs Patients who climbed between 7-8 flights of stairs had an intermediate risk of complications (30%) PULMONARY SPECIFIC EVALUATION Integrated cardiopulmonary exercise testing: • The most important measurement during cardiopulmonary exercise testing that correlates with postoperative complications is the level of work achieved • Measured by VO2max • An early report demonstrated no mortality in patients able to achieve a VO2max in excess of 1 L/min, compared with 75 percent mortality in those with a VO2max below 1 L/min31. • Expressing VO2max in terms of mL/kg per min, which takes into account the patient's body mass, may increase the predictive power of the test Current guidelines from the ACCP considers patients with: • VO2max <10 mL/kg per min • VO2max <15 mL/kg per min predicted postoperative FEV1 and DLCO <40% predicted, to be at high risk for perioperative death and cardiopulmonary complications 6 min walk test OTHER SURGERY PULMONARY FUNCTION TESTING There is considerable debate regarding the role of preoperative pulmonary function testing for risk stratification Two reasonable goals that could potentially justify the use of preoperative PFTs: • ID of a group of patients for whom the risk of the proposed surgery is not justified by the benefit • ID of a subset of patients at higher risk for whom aggressive perioperative management is warranted Bedside spirometry is widely available, and measures of the forced expiratory volume in one second (FEV1) and forced vital capacity (FVC) have been frequently reported. Increased risk: • FEV1 <70 % predicted • FVC <70 % predicted • FEV1/FVC ratio <65 % There is little support from the literature that any of these goals is routinely met other than for lung resection surgery Other factors conferred higher odds ratios for pulmonary complications than did abnormal spirometry • ASA class >3 and chronic mucous hypersecretion. OTHER SURGERY RECOMMENDATION: Based on a systematic review, a 2006 American College of Physicians guideline recommends that clinicians not use preoperative spirometry routinely for predicting the risk of postoperative pulmonary complications A reasonable approach to patient selection for preoperative pulmonary function testing follows: • Obtain PFTs for patients with COPD or asthma if clinical evaluation cannot determine if the patient is at their best baseline and that airflow obstruction is optimally reduced • Obtain PFTs for patients with dyspnea or exercise intolerance that remains unexplained after clinical evaluation • PFTs should not be used as the primary factor to deny surgery • PFTs should not be ordered routinely prior to abdominal surgery or other high risk surgeries OTHER SURGERY ARTERIAL BLOOD GAS ANALYSIS • No data suggest that the finding of PCO2 >45mmHg identifies high-risk patients who would not have otherwise been identified based upon established clinical risk factors • The risk associated with this degree of PaCO2 elevation is not necessarily prohibitive, although it should lead to a reassessment of the indication • Hypoxemia has generally not been identified as a significant independent predictor of complications after adjustment for potential confounders. • Current data do not support the use of preoperative arterial blood gas analyses to stratify risk for postoperative pulmonary complications EXERCISE TESTING • There are no data to support its routine use in the evaluation of patients prior to general surgery. OTHER SURGERY CHEST RADIOGRAPHS • Abnormal CXR are seen with increasing frequency with age • CXR add little to the clinical evaluation in identifying healthy patients at risk As an example, one study screened 905 surgical admissions for the presence of clinical factors that were thought to be risk factors for an abnormal preoperative CXR • No risk factors in 368 patients; of these, only one (0.3%) had an abnormal CXR, which did not affect the surgery • 504 patients had identifiable risk factors; of these, 114 (22%) had significant abnormalities on preoperative CXR A meta-analysis of studies of routine preoperative CXR • Of 14,390 preoperative x-rays, there were only 140 unexpected abnormalities and only 14 cases where the chest x-ray was abnormal and influenced management. The available literature does not allow an evidence-based determination of which patient will benefit from a preoperative CXR however, it is reasonable to obtain preoperative CXR: • in patients with known cardiopulmonary disease and in • those over age 50 years undergoing high risk surgical procedures, including upper abdominal, aortic, esophageal, and thoracic surgery. PULMONARY RISK INDICES CARDIOPULMONARY RISK INDEX A combined CPRI was proposed based upon the Goldman criteria for cardiac risk, adding: • • • • • • Obesity (BMI >27 kg/m2) Cigarette smoking within eight weeks of surgery Productive cough within five days of surgery Diffuse wheezing or rhonchi within five days of surgery FEV1/FVC <70% PaCO2 >45 mmHg Results of this scoring system have been mixed Limitation of this index is the requirement for PFT and ABG PULMONARY RISK INDICES BROOKS-BRUNN RISK INDEX A different set of proposed criteria for a risk index Six factors were independently associated with increased pulmonary risk after abdominal surgery: • • • • • • Age >60 Obesity (BMI >27 kg/m2) Impaired cognitive function History of cancer Smoking history in past eight weeks Upper abdominal incision In a subsequent validation cohort by the same author, the original model validated relatively well, but other factors emerged as significant PULMONARY RISK INDICES MULTIFACTORIAL RISK INDEX FOR POSTOPERATIVE RESPIRATORY FAILURE • • • Investigators have more recently published the most ambitious multifactorial risk index to predict postoperative respiratory failure This index is modelled after the widely used cardiac risk indices Procedure-related risk factors dominate the index with type of surgery and emergency surgery being the most important predictors New observations in this study included the importance of: • Abdominal aortic aneurysm repair • Emergency surgery • Metabolic factors as risk factors • Investigators have also reported a similar index to predict postoperative pneumonia. • • • These indices significantly advance the field of preoperative pulmonary risk assessment They rely upon readily available clinical information A limitation is that most of the factors are not modifiable. 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