Preoperative2 - DM Seminar Preoperative Evaluation of...

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Unformatted text preview: DM Seminar Preoperative Evaluation of Non-Thoracic Surgery Dr. Ajmal Khan Introduction • Postoperative pulmonary complications – Significant cause of morbidity & mortality • Incidence varies from 2% to 19% Am Am J Med. 2002:112:219-225 • Management requires – Understanding of the predictable pulmonary physiological changes with surgery & anesthesia – Knowledge of factors associated with development of postsurgical respiratory compromise Pulmonary changes with surgery • Lung volume • Diaphragmatic function • Gas exchange • Control of breathing • Lung defense mechanism Lung Volume • Restrictive abnormalities • Moderate to severe reduction in Vital Capacity • Reduction in functional residual capacity • ↓ FEV1 • No change in FEV1/FVC → No airway obstruction • Key factor in postoperative changes in lung function is relationship between FRC & CC Lung Volume FRC > CC CC >FRC + VT FRC < CC < FRC +VT • FRC is the lung volume at the end of Conditions Altering FRC & CC normal tidal expirationRelationship CC Decrease FRC Increase Supine Position Advanced Age • Closing capacity is the lung volume at Obesity Smoking VT VT Pregnancy COPD VT bases which small airways in the lung Edema General Anesthesia Pulmonary Abdominal Pain begin to close during expiration because of a reduction in airway radial traction FRC CC Normal Lung FRC Atelectatic Lung CC FRC CC Region of Low V/Q Diaphragm Function • Important factor contributing to postoperative reduction in lung volume • Decreased CNS output to phrenic nerve due to inhibitory reflexes arising from – Sympathetic – Vagal – Splanchnic receptors Gas Exchange • Arterial hypoxemia – Common • Initial Phase – Occurs in the first several hours – Residual effect of the anesthesia • Ventilation-perfusion mismatch • Anesthesia induced inhibition of hypoxic pulm vasoconstriction • Right to left shunting • Increased oxygen consumption in peripheral muscle • Depressed cardiac output Gas Exchange • Late phase – Persists for several days to weeks – Common in thoracic and upper abd surgery – Correlates with reduction in FRC and changes in FRC-CC relationship – Other process involved are: • Alveolar hypoventilation • Increased dead space ventilation due to rapid shallow breathing • Decreased mixed venous oxygen due to increased consumption Control of Breathing • Post operative respiratory depression • Two factors are responsible – Residual effect of preanesthetic & anesthetic agents • Inhibits respiratory drive • Reduce ventilatory response to hypercapnia, hypoxia & acidemia – Postoperative Narcotics • Depress hypercapnic & hypoxic ventilatory drive resulting in – Decreased tidal volume – Reduced minute ventilation Lung Defense Mechanism • Impaired cough – Postoperative pain & narcotics inhibits cough – Altered lung mechanics reduces explosive nature of cough • Impaired mucociliary clearance – – – – – Ineffective cough reflex Ciliary damage due to intubation, inhalational agents Inhibition of mucociliary transport due to anesthesia Reduced mucus velocity due to ET tube Atelectasis Pulmonary Complications • Five major categories of complications – Atelectasis – Infection – Tracheobronchitis & Pneumonia – Exacerbation of underlying chronic disease – Prolonged mechanical ventilation & respiratory failure – Thromboembolic disease Risk Factors Preoperative •Age is a significant risk for post operative Age •Smoking independently increases risk for complications Smoking complications •General health condition increasesASA correlates with complications Reduction comorbidities Associatedin risk asSmoking discontinued for > 8 wks Health condition if categorized by risk •Chronic lung disease ASA II or higher is powerful predictor of complications postoperatively Chronic lungleads •Nutritional status to is associated with increased complications Malnutrition disease Relative riskdiaphragmatic function •Respiratory tract infection2.7 – 4.7 •Decreased ranges from Requires adequate disease control prior to surgery •Impaired cell Intraoperative mediated & humoral immunity •Alteration in the elastic properties of the lung •Type of anesthesia National of Surgical •Duration VAsurgery Risk Study group reported low albumin levels as strong predictor of 30 day mortality (Arch Surg.1999:134:22-7) •Surgical site Complication rates according to site are •Type of surgical incision < 1% nonthoracoabdominal surgery Postoperative <5% lower abdominal surgery •Immobilization > 5% upper abdominal •Inadequate pain controlsurgery Age Age related changes in respiratory function & postoperative complications Age Related Changes Clinical Consequences Clinical ↓ Chest wall compliance ↑ Lung Compliance ↑Respiratory system resistance ↑ Work of Breathing ↓ Ventilatory response to exercise ↑ Residual volume ↑ Small airway closure Impaired gas exchange ↑ Ventilation perfusion mismatch ↓ Respiratory muscle strength ↑ Protective cough & swallow reflex ↓ Secretion clearance ↑Risk of aspiration Altered Control of Breathing Altered ↓Responsiveness to imposed respiratory loads ↓Responsiveness to hypoxemia and Hypoventilation Hypoxemia and hypercarbia hypercarbia to anesthetic agents and opiods Respiratory failure in early ↑Sensitivity postoperative period Effects of General Anesthesia • Decreases number & activity of alveolar macrophages • Increases alveolar capillary permeability • Inhibits surfactant release • ↑ activity of pulmonary nitric oxide synthetase • Enhances sensitivity of the pulmonary vasculature to α-adrenergic agonists Effects of General Anesthesia • Produces significant effects on diaphragmatic movement with near uniform motion of the diaphragm along the ventral-dorsal axis • Results in more ventilation of the superior portion of the lung (less perfusion) and less ventilation of the lung in the dependent portions (more perfusion) • V/Q inequality leads to shunt & dead space ventilation • ↑ alveolar-arterial oxygen gradient Components of Preoperative Evaluation • • • • • Clinical history, physical examination Medical summary Evidence based risk assessment Risk reduction strategy Communication of risk and strategy to patients, surgeons and anesthesiologist CARE Study • Specific history & physical examination useful in identifying patients at risk for PPC • Prospectively enrolled 272 consecutive patients • 22 (8%) pulmonary complications CARE Study (History) Variable P value Smoked > 40 pack years Odds Ratio (95% CI) 5.7 (2.3-14.2) Age > 65 4.7 (1.6-14.4) 0.006 History of COPD 4.2 (1.6-11.3) 0.007 Exercise < 1 flight stairs/2 blocks 3.0 (1.1-7.8) 0.05 Ever smoked 2.2 (0.8-5.8) 0.16 History of asthma 2 (0.6-6.4) 0.41 Daily productive cough 1.9 (0.6-6.1) 0.45 Male 1.03 (0.6-1.8) 0.91 Current smoker (within 2 wks) 0.7(0.2-2.3) 0.69 Recent URTI 0.7(0.2-3.3) 0.95 0.0002 CARE Study (Examination) Variable Odds Ratio (95% CI) 6.9 (2.7-17.4) 6.9 (2.7-17.4) P value 5.7 (2.3-14.2) 0.0002 5.7 (2.3-14.2) 4.3 (1.5-12.3) 0.01 0.004 Positive cough test Positive wheeze test BMI > 30 2.5 hours Operation > Positive wheeze test Wheezing 4.1 (1.6-10.4) 4.3 (1.5-12.3) 3.4 (1.2-9.4) 4.1 (1.6-10.4) 2.9 (1.2-7.0) 3.4 (1.2-9.4) 3.1 (0.9-10) General anaesthesia Operation > 2.5 hours 2.4 (0.5-10.5) 2.9 (1.2-7.0) 0.38 Upper abdominal incision 1.0 (0.2-4.7) 0.73 Maximum laryngeal ht < 4 cm Maximum laryngeal ht < 4 Forced exp time > 9 sec cm Positive cough test Forced exp time > 9 sec BMI > 30 0.0001 0.0001 0.04 0.03 0.13 0.0002 0.01 0.004 0.04 0.03 CARE Study (Laboratory) Variable Odds Ratio (95% CI) P value PCO2 > 45 mm Hg 61 (3.8-986.4) 0.001 PO2 < 75 mm Hg 13.4 (1.3-14.1) 0.008 FVC < 1.5 L/min 11.1 (2.2-56.4) 0.005 FEV1 < 1 L/min 7.9 (1.7-37) 0.002 Abnormal CXR 1.7 (0.6-4.9) 0.40 CARE Study (Laboratory) Variable Odds Ratio (95% CI) P value PCO2 > 45 mm Hg 61 (3.8-986.4) 0.001 PO2 < 75 mm Hg 13.4 (1.3-14.1) 0.008 FVC < 1.5 L/min 11.1 (2.2-56.4) 0.005 FEV1 < 1 L/min 7.9 (1.7-37) 0.002 Smoking • Those who quit smoking for more than six months had complications rates similar to those who had never smoked (11% vs. Anaestheseology 1984;60:38011.9%) 3 • Smoking history of 40 pack years or more was strongly associated with increased Am J Respir Crit Care risk of pulmonary complications Med 2003;167:741-4 COPD • Severe COPD patients are six times more likely to have major postoperative Anaestheseology 1984;60:380complication 3 • Careful preoperative evaluation of patients with COPD should include • identification of high-risk patients • optimizing their treatment before surgery Pulmonary Function Test • ACP consensus statement recommends preoperative PFT in two Am J Respir Crit Care Med groups 2003;167:211-77 – Patients undergoing coronary bypass or upper abdominal surgery with a history of smoking or dyspnea – Patients undergoing head and neck, orthopedic, or lower abdominal surgery with unexplained dyspnea or pulmonary symptoms • Preoperative PFT does not identify patients in whom the risk is so high that surgery should be cancelled Spirometry • No single value on spirometry can absolutely contraindicate non-thoracic surgery • There is higher risk of postoperative pulmonary complications in patients with Chest 1986;89:127– FEV1 or FVC < 70% predicted – FEV1/FVC ratio of < 65% 35 • An ambigous clinical picture regarding – – – – Severity of bronchospasm Presence of COPD Response to bronchodilators Unexplained shortness of breath Preoperative Risk Factor Point Value Type of Surgery •Abdominal aortic aneurysm repair •Thoracic •Upper abdominal •Neck •Neurosurgery •Vascular 15 The PPRI classifies patients into five levels of risk for 15 14 postoperative pneumonia with good discrimination 10 Age •> 80 years •70-79 years •60 - 69 years •50 – 59 years 8 8 3 Index Score Functional Status •Totally dependent •Partially dependent Weight loss > 10% in past 6 months 0-15 17 17 13 9 4 16-25 1.2 26-40 4.0 10 10 6 41-55 9.4 7 15.3 5 History of chronic obstructive pulmonary disease General anesthesia Probability (%) 0.2 >55 4 Impaired sensorium 4 History of cerebrovascular accident 4 Blood urea nitrogen level •8 mg/dl •22 - 30 mg/dl •> 30 mg/dl 4 2 3 Transfusion > 4 units 3 Emergency surgery 3 Steroid use for chronic condition 3 Current smoker within 1 year 3 Alcohol intake > 2 drinks/day in past 2 weeks 2 Recommendation 2 Recommendation 56 Recommendation 4 1 procedures are at Recommendation 3 Patients undergoing following higher risk for postoperative Preoperative spirometry and chest evaluation solely otherofbe at higherrisk forfor radiography should not be used routinelyrisk The following procedures & (35 g/L) the presence markertoconcomitant risk factors All low serum albuminpreoperative be evaluated for for reducing postoperative A patients should be level should increased risk All patients complications shouldfor is a powerful of the following significantfor pulmonary who after evaluated not be used are found predicting risk pulmonary pulmonary complications in order to receivepostoperative pulmonary postoperative complications andcomplications. following all patients postoperative for& postoperative interventions to reduce pulmonary complications: postoperative pulmonaryrisk: factors for complication complications should receive measured in pre- and and receive pre- postoperative pulmonary should be the 1)Right-heart catheterization ofreduce pulmonary risk: complications: should be procedures in interventions to postoperative pulmonary measurement who •Prolonged surgery (3 hours) are clinically suspected postoperative order to reduce having hypoalbuminemia; 2)Total breathing nutrition oror more risk factors for perioperative pulmonary 1)Deep parenteral exercises1or incentive spirometry(for patients who are considered in obstructive pulmonary disease •Chronic patients with total enteral nutrition Abdominal surgery malnourished orof a nasogastric tube (as needed for postoperative nausea or 2)Selective use than 60 years complications. surgery low serum albumin levels). •Age older have Thoracic vomiting, inability to tolerate oral intake, or symptomatic abdominal distention). •American Society of Anesthesiologists (ASA) class of II or greater Neurosurgery •Functionally dependent Head and neck surgery •Congestive heart failure Vascular surgery •Aortic aneurysm repair Ann Intern Med 2006,144:575•Emergency surgery 580 •General anesthesia. Risk Reduction Strategies Preoperative •Smoking cessation - 8 wks •Treat airflow obstruction •Antibiotics & delay surgery if infection •Patient education for lung exapansion maneuvers Intraoperative •Limit surgery < 3 hrs •Spinal or epidural anesthesia •Laproscopic procedure if possible Postoperative •Deep breathing exercises and incentive spirometry Supplemental oxygen therapy •Epidural analgesia •Decreases heart rate therapy • Supplemental oxygen •Increases arterial oxygen saturation Anesthesiology 1999:90:380-4 •Decreases postoperative nausea & vomiting •Decreases surgical wound infection by 50% N Engl J Med 2000:342:1617 ...
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