Preoperative Laboratory Testing in Patients Undergoing Elective, Low-Risk Ambulatory Surgery Jaime Benarroch-Gampel, Kristin M. Sheffield, Casey B. Duncan, Kimberly M. Brown, Yimei Han, Courtney M. Townsend, Jr., and Taylor S. Riall Department of Surgery Center for Comparative Effectiveness and Cancer Outcomes The University of Texas Medical Branch Galveston, TX
Which of the following preoperative laboratory test is routinely indicated in an 80 years old male undergoing low-risk ambulatory surgery A.Complete blood count B.Chemistry panel C.Coagulation tests D.All of the test E.None of the test
Preoperative Testing in Ambulatory Surgery INTRODUCTION • Ambulatory surgery – <1-2 hours in duration – Low expected blood loss – Low complication rates – Minimal expected postoperative care – Performed in patients with no medical problems or stable chronic medical conditions • 60-70% of procedures in the U.S. performed in the ambulatory setting
Preoperative Testing in Ambulatory Surgery INTRODUCTION • Potential benefits of preoperative testing – Predicting patient risk for postoperative complications – Screening for unsuspected abnormalities – Establishing baseline values for tests that may change after surgery – Providing medical-legal protection
Preoperative Testing in Ambulatory Surgery INTRODUCTION • Potential risks of preoperative testing – Cost: estimated between 3-18 billion – Increased pain and inconvenience – Anxiety for patients – Abnormal results in some cases are of questionable clinical significance – Harm to patients due to overtreatment of false-positive results – Medical-legal risk
Preoperative Testing in Ambulatory Surgery INTRODUCTION • Current recommendations based on 2002 Practice Advisory from American Society of Anesthesiologists (ASA) – Based on expert opinion and underpowered studies – Inconsistencies between societies – Imprecise language • Many advocate against routine testing • Fail to outline clear and consistent guidelines for specific tests
Preoperative Testing in Ambulatory Surgery INTRODUCTION INDICATION Hg/CBC Creatinine Electrolytes LFTs Albumin Coagulation Parameters Advanced age ASA OPTG OPTG OPTG Bleeding ASA ASA disorders CAS OPTG CAS Cardiovascular disease OPTG Renal disease CAS CAS ASA ASA OPTG OPTG CAS OPTG Liver disease CAS OPTG ASA OPTG CAS OPTG Hypertension OPTG CAS CAS OPTG OPTG Diabetes OPTG CAS OPTG Smoking OPTG Alcohol abuse OPTG OPTG OPTG ASA: American Society of Anesthesiologists, CAS: Canadian Anesthesiologists ’ Society, OPTG: Ontario Preoperative Testing Grid, LFT: Liver Function Tests
Preoperative Testing in Ambulatory Surgery OBJECTIVES • Use population-based data (NSQIP) to: – Describe the current use of preoperative testing in elective, low-risk ambulatory surgery • All patients • Subgroup with no comorbidities – Identify patient factors associated with preoperative testing – Evaluate the association between preoperative testing and 30-day outcomes
Preoperative Testing in Ambulatory Surgery METHODS Data Source • National Surgical Quality Improvement Program Participant Use Data File (PUF) • Study period: 2005-2010 • Contains 240 variables: – Patient characteristics – Procedure characteristics • Anatomic site • Open vs. laparoscopic • Initial vs. recurrent
Preoperative Testing in Ambulatory Surgery METHODS Cohort Selection • Inclusion criteria: – >18 years old – Elective hernia repair (CPT codes) • Inguinal hernia (49505, 49520, 49525, 49650, 49651) • Umbilical hernia (49585) • Epigastric hernia (49570) • Femoral hernia (49550, 49555) – Same day admission – No surgery in previous 30 days – No additional surgical procedures at time of hernia repair
Cohort Selection (continued)
Preoperative Testing in Ambulatory Surgery METHODS Laboratory Testing • Preoperative testing defined as testing in the 30 days up to and including surgery • Normal values were defined using our institutional laboratory ranges LFTs LFTs Hematology Hematology Chemistry Chemistry Coagulation Coagulation Albumin Albumin Hematocrit Hematocrit Sodium Sodium PT PT Total bilirubin Total bilirubin WBC WBC BUN BUN PTT PTT AST AST Platelets Platelets creatinine creatinine INR INR Alkaline Alkaline phosphatase phosphatase 92% 90% 77% 89%
Preoperative Testing in Ambulatory Surgery METHODS • Additional outcome variables: – Major complications: unplanned intubation, PE, stroke, coma >24h, acute renal failure, MI, cardiac arrest, sepsis/septic shock, blood transfusions, or death – Wound-related complications: superficial and deep surgical site infections, organ space infections, and wound dehiscence
Preoperative Testing in Ambulatory Surgery METHODS Statistical Analysis • Use of preoperative testing described • Chi-square to compare categorical variables and T-test to compare continuous variables • Multivariate logistic regression models used to determine: – Factors associated with preoperative testing – Association between • Preoperative testing and 30-day outcomes • Abnormal results and 30-day outcomes
RESULTS Demographics and Procedures NO LABS LABS P-value (N=26,619) (N=46,977) 36% 64% PATIENT CHARACTERISTICS 48.6 ± 16.0 yrs 57.7 ± 15.9 yrs Age <0.0001 Male gender 84.3% 84.4% 0.66 White 82.7% 79.5% <0.0001 ASA Class 3 11.4% 26.0% <0.0001 At least 1 comorbidity 56.6% 71.1% <0.0001 PROCEDURE DETAILS General anesthesia 76.1% 78.1% <0.0001 72.6% 74.5% Inguinal hernia <0.0001 Laparoscopic repair 17.3% 18.4% 0.0002 Recurrent hernia 6.7% 7.3% 0.001
Preoperative Testing in Ambulatory Surgery RESULTS Preoperative Testing Use
Preoperative Testing in Ambulatory Surgery RESULTS Preoperative Testing Use OVERALL COHORT (N=73,596) % Use % Abnormal Any Test 63.8% 61.6% Hematology 58.6% 39.3% Chemistry 53.5% 40.2% Coagulation 18.7% 11.3% LFT 23.7% 22.8%
Preoperative Testing in Ambulatory Surgery RESULTS Preoperative Testing Use SUBGROUP WITHOUT COMORBIDITIES N=25,146 (34% of overall cohort) % Use % Abnormal Any test 54.0% 54.1% Hematology 51.8% 36.2% Chemistry 41.8% 33.0% Coagulation 14.8% 5.9% LFT 19.6% 18.4%
Preoperative Testing in Ambulatory Surgery RESULTS Preoperative Testing Use SAME-DAY TESTING N=7,209 (9.7% of overall cohort) % Use % Abnormal Any Test 100.0% 61.6% Hematology 86.0% 41.9% Chemistry 76.5% 40.9% Coagulation 35.4% 22.9% LFT 25.8% 33.2%
Preoperative Testing in Ambulatory Surgery RESULTS Preoperative Testing Use Without Age group All patients comorbidities Younger than 20y 34.9% 33.5% 21y – 30y 42.1% 40.0% 31y – 40y 47.9% 43.7% 41y – 50y 56.5% 49.9% 51y – 60y 66.2% 58.5% 61y – 70y 73.8% 66.3% 71y – 80y 79.5% 71.8% Older than 81y 83.2% 75.0%
RESULTS Multivariate Analysis: Factors Predicting Testing • Factors associated with receipt of testing across all test types: – Increased age – Black or Hispanic race – ASA class 2 and 3 – Receipt of general anesthesia – Laparoscopic procedures – Hypertension – Diabetes – Ascites – Bleeding disorders – Steroid use
RESULTS Adverse Outcomes and Testing • Major complications: 0.3% (N=239) • Wound complications: 0.8% (N=567) Major Complications Wound-Related OR 95% CI OR 95% CI OVERALL COHORT Hematology 1.17 (0.88 – 1.56) 0.99 (0.83 – 1.18) Chemistry 1.30 (0.97 – 1.75) 1.03 (0.87 – 1.24) Coagulation 1.25 (0.93 – 1.67) 1.05 (0.84 – 1.30) LFT 1.02 (0.77 – 1.36) 1.07 (0.88 – 1.30)
Preoperative Testing in Ambulatory Surgery RESULTS Adjusted Outcomes: Tested vs. Not Tested Major Complications Wound-Related OR 95% CI OR 95% CI SUBGROUP WITHOUT COMORBIDITIES Hematology 0.77 (0.40 – 1.49) 1.36 (0.91 – 2.03) Chemistry 1.00 (0.52 – 1.96) 1.35 (0.91 – 2.02) Coagulation 1.38 (0.63 – 3.05) 1.04 (0.60 – 1.78) LFT 0.94 (0.42 – 2.08) 1.07 (0.66 – 1.75)
Preoperative Testing in Ambulatory Surgery RESULTS Adjusted Outcomes: Abnormal vs. Normal Tests Major Wound-related OR 95% CI OR 95% CI ABNORMAL vs. NORMAL (Tested patients only) Hematology 1.29 (0.95 – 1.75) 0.96 (0.76 – 1.20) Chemistry 1.28 (0.93 – 1.75) 1.15 (0.90 – 1.46) Coagulation 1.52 (0.81 – 2.53) 1.16 (0.66 – 2.08) LFT 1.50 (0.90 – 2.49) 1.14 (0.79 – 1.65)
Preoperative Testing in Ambulatory Surgery LIMITATIONS • Selection bias • Unable to identify patients who had changes in planned surgery or repeat testing due to abnormal results • NSQIP does not report all tests types • Unable to identify ordering physician nor can we evaluate variation among providers
Preoperative Testing in Ambulatory Surgery MEDICARE TESTING RATES HERNIA REPAIR All patients No comorbidities Test (N=13,029) (N=3,187) Any test 84.5% 78.9% CXR 43.5% 38.1% EKG 62.0% 59.5% Hg/Hematocrit 53.1% 49.6% Platelets 51.8% 48.3% Creatinine 27.0% 23.2% Electrolytes 53.6% 48.2% LFTs 35.2% 30.9% Coagulation 16.2% 9.2%
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