Preoperative Clinics

Preoperative Clinics

P re o p e r a t i v e C l i n i c s Joyce Akwe, a,b, * MD, MPH KEYWORDS  Preoperative clinic  Evaluation  Standardization  Efficiency HOSPITAL...

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P re o p e r a t i v e C l i n i c s Joyce Akwe,

a,b, * MD, MPH

KEYWORDS  Preoperative clinic  Evaluation  Standardization  Efficiency

HOSPITAL MEDICINE CLINICS CHECKLIST

1. Preoperative clinics are centralized and standardized centers for evaluating patients, clinically optimizing their medical conditions, and confirming informed consent. 2. Preoperative clinics are generally attended by patients scheduled to undergo surgical outpatient procedures, such as colonoscopy and biopsies; scheduled inpatient surgeries; and for medical evaluation before undergoing electroconvulsive therapy. 3. Preoperative clinics should have the following key components: a standardized preoperative assessment process that meets the regulatory and accreditation standards, payer requirements for Medicare and Medicaid services, or the National Surgical Improvement programs; incorporation of current evidencebased practice guidelines, appropriate triage, and time allocation for preoperative evaluation based on a patient’s risk level; and easy accessibility of the clinic to outpatient surgical clinics or operating rooms. 4. To be successful, preoperative clinics need adequate financial and support resources, clear goals, a multidisciplinary team, and the buy-in of hospital administration. 5. Hospitals or clinic systems should develop a preoperative assessment, consultation, and treatment clinic for a complete patient evaluation and management. 6. The general goals of a preoperative clinic are to optimize the patient’s clinical status before surgery to improve outcome, improve patient and procedure scheduling, increase efficiency and cost-effectiveness, and reduce the number of inpatients. 7. Preoperative clinics can be structured to meet the specific goals of patients, anesthesiologists, surgeons, and hospital administrators simultaneously. CONTINUED

a

Emory University School of Medicine, 1365 Clifton Road, Atlanta, GA 30322, USA; Morehouse School of Medicine, 720 Westview Drive SW Atlanta, GA 30310-1495, USA * Atlanta VA Medical Center, 1670 Clairmont Road, Decatur, GA 30033. E-mail address: [email protected] b

Hosp Med Clin 1 (2012) e548–e557 doi:10.1016/j.ehmc.2012.05.001 2211-5943/12/$ – see front matter Ó 2012 Elsevier Inc. All rights reserved.

Preoperative Clinics

CONTINUED

8. Preoperative clinics have the following proved outcomes: a reduction in mortality and morbidity, a reduction in cost, a reduction in length of hospital stay, a decrease in cancellations or delays in surgery on the day of surgery, an increase in surgical case procedures, an increase in patient satisfaction, a reduction in excessive preoperative testing, and the identification and management of new medical conditions. 9. Most preoperative clinics are managed by anesthesiologists and trained nurse practitioners. Some other models are completely managed by the medicine service, and a few models are run by surgeons.

INTRODUCTION

What are preoperative clinics? Preoperative clinics are centralized and standardized centers for evaluating patients, clinically optimizing their medical conditions, and confirming informed consent. These centers are also known as preanesthesia assessment clinics (PAC)1; preadmission clinics2; preassessment clinics3; preoperative assessment, consultation, and treatment (PACT) clinics4; anesthesia preoperative medicine clinics (APMC)5; or perioperative medicine service.6 Preoperative clinics first emerged in the 1940s7 because of work pressure in outpatient clinics. These clinics aimed to optimize the patient’s condition before surgery.8 Additionally, these clinics provided patients and their loved ones with education about perioperative events and the nature of the surgery and anesthesia they would undergo. In the past, patients who had to undergo surgery were referred to the primary care physician for “clearance.” Today, this is evolving more toward multidisciplinary centralized clinics, specialized in perioperative care and managed by anesthetists, surgeons, or internists working with other specialists, such as cardiology, hematology, and pulmonary consultants. A successful preoperative clinic seeks to9       

Decrease surgical morbidity Minimize expensive delays in the start of surgery Decrease cancellations on the day of surgery Evaluate and optimize patient health status Facilitate the planning of anesthesia and perioperative care Reduce patient anxiety through education Obtain informed consent

Who attends the preoperative clinic? Preoperative clinics are generally attended by patients scheduled to undergo surgical procedures, which may be outpatient procedures, such as colonoscopy and biopsies, or scheduled inpatient surgeries. Patients are also referred to preoperative clinics for medical evaluation before undergoing electroconvulsive therapy.10 Preoperative clinics are a good resource to provide education to patients and their loved ones regarding perioperative events, anesthesia, and the nature of the planned surgery. These clinics are also an excellent forum to stimulate behavior change that can reduce

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preoperative anxiety; answer patient’s questions; and clarify doubts with regards to surgery, anesthesia, and perioperative events. STRUCTURE

What are the key components of a preoperative clinic? A standardized preoperative assessment process should meet the regulatory and accreditation standards; payer requirements, such as the Centers for Medicare and Medicaid Services or the National Surgical Improvement programs; and current evidence-based practice. The regulatory and accreditation standards, such as those of the Joint Commission, require for example a complete history and physical within 30 days before surgery. The Joint Commission among other standards requires an anesthesiology and a nursing assessment with mandatory elements including documentation of pertinent negative events and ordering appropriate laboratory testing and imaging, such as an electrocardiogram.11 Current evidence-based practice guidelines, such as the American College of Cardiology/American Heart Association (ACC/AHA) task force 2007 guidelines on perioperative cardiovascular evaluation and care for noncardiac surgery,12 should be incorporated in the operation of the preoperative clinic. Another very important component of the preoperative clinic is an appropriate triage and time allocation for preoperative evaluation based on a patient’s risk level.4 Anesthesia risk stratifies patients from 1 (low medical risk) to 5 (high medical risk) based on patient comorbidities, whereas surgeons rate surgical procedures by physiologic stress of the procedure and blood loss from 1 (low surgical risk) to 5 (high surgical risk). In some centers,4 patients are placed in three risk categories (high, intermediate, and low risk) based on the surgical and anesthesia risk stratifications to determine the timing and intensity of preoperative evaluation. These risk categories may be used to determine the consultants who should be involved in the preoperative evaluation and care of the patient.4 The ACC/AHA guidelines also classify the clinical predictors of increased perioperative cardiovascular risks for myocardial infarction, heart failure, and death into major, intermediate, and minor risk factors. During patient evaluation, emphasis is placed on detecting the predictors of increased cardiovascular risks and ascertaining functional capacity, as outlined in the ACC/AHA guidelines.12 Electronic medical records allow for standardization of preoperative evaluation and patient information and serve as a database for research.12,13 Boedeker and colleagues14 used software that incorporated a cardiac algorithm into the preoperative evaluation. Ryan and colleagues4 implemented stations on wheels to facilitate the incorporation and consistent documentation of patient education and performance measures. Modern outpatient preoperative clinics see patients in a centralized location close to outpatient surgical clinics to promote easy accessibility, or the clinic meets next to the operating room (OR) as part of the preoperative service unit.15 The preoperative clinic serves as a one-stop center where patients have their surgical, anesthesia, and medical care coordinated and managed appropriately during the perioperative period.15 Some models of the preoperative clinic describe a process that starts at referral from the surgical clinic to the preoperative clinic. At the clinic, the patient is evaluated for risk stratification using guidelines, after which the patient is referred to other specialists or the patient’s clinical condition is optimized and recommendations

Preoperative Clinics

made for postoperative care. After the medical conditions are optimized by the multidisciplinary team, the patient is then approved for surgery.15 In one university setting, there has been involvement of essential employees combined with mathematical techniques to support the decision-making process, resulting in a successful intervention.1 What are the critical success factors of a preoperative clinic? The following factors are needed to establish a successful preoperative clinic4,16: 1. 2. 3. 4. 5.

Financial and time commitment Adequate support resources Clear identification and definition of goals Multidisciplinary team work Cooperation of administration for operational changes

How should the preoperative center be structured? Preoperative centers should be structured based on the best practice recommendations by Ryan and colleagues,4 which are summarized next.  Hospitals or clinic systems should develop a PACT clinic for a complete patient evaluation and management.  PACT assessment should include a complete preoperative history and physical examination by experienced clinicians.  Patients should have same-day access to testing centers and medical consultants.  Preoperative patient evaluations should be standardized, and protocols created for the most common surgeries in relation to the patient’s medical conditions and comorbidities or risk level.  Preoperative data entry should be streamlined, ideally integrating ambulatory and inpatient medical records during the preoperative evaluation.  Before the patient’s appointment, the patient’s pertinent medical records should be obtained and integrated into the electronic medical record to improve efficiency and effectiveness of the preoperative evaluation process.  The timing of a patient’s preoperative evaluation must take into consideration several factors including the type and urgency of the surgery and the surgical and anesthesia risks.  It is important to complete the preoperative medical and surgical evaluation before the day of surgery. Allocating time based on the severity of a patient’s condition facilitates more efficient workflow. There have been several other structures for preoperative clinics but the common aspects shared by these testing centers include centralization of the preoperative evaluation process and electronic medical records. Most clinics have common goals, as noted next. GOALS OF THE PREOPERATIVE CLINIC

What are the general goals of a preoperative clinic?13,16  To optimize the patient’s clinical status before surgery to improve outcome  To decrease cancellations and delays on the day of surgery  To improve the “on-time” start of surgery

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 To improve turnover time  To ensure cost-effective ordering of tests and use of consultation services  To guarantee availability of patient medical information including complete History and Physical tests and consultant recommendations at the time of surgery  To eliminate duplicate testing caused by lack of communication or availability of the tests in the patient’s electronic medical record  To provide patient-centered care and documentation  To facilitate billing and documentation  To improve the quality of documentation for informed consent  To provide comprehensive and organized documentation for research and quality improvement  To improve overall patient care satisfaction  To improve education provided to the patient and their family members  To provide an education or training experience to residents, medical students, and perioperative staff  To improve faculty development  To perform quality assurance and maximize efficiency  To improve preoperative assessment and management  To improve operating room efficacy  To reduce the number of inpatients What are the specific goals of the various clients of the preoperative clinic?13,16 Patients would like to:  Spend less time waiting to have surgery  Have the least possible amount of complications  Get answers to questions and have concerns addressed Anesthesiologists would like to:  Receive prior notice about patients with difficult airways or conditions, such as panic disorder  Have the opportunity to educate patients regarding anesthesia  Have easy access to the preoperative assessment Surgeons would like to:  Have easy access to consultations and test results  Have a vested interest in starting surgeries on time Physicians in training would like to:  Have more focused training on preoperative medicine evaluation Hospitals would like to:      

Achieve a decrease in the length of stay Run an efficient OR suite Limit unnecessary staff expenditures Attract profitable surgeons and patients Avoid lawsuits related to poor care Increase profit

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OUTCOMES OF PREOPERATIVE CLINICS

What are the outcomes of preoperative clinics?

Reduction in Mortality and Morbidity

An Australian 1994 to 1996 triennial report on anesthesia-related perioperative deaths implicated inadequate preoperative assessment and management in 53 of the 135 deaths attributable to anesthesia.17,18 Another earlier report showed a sixfold increase in mortality in patients who did not have an adequate preoperative assessment compared with those who had been thoroughly assessed.19 In the same report, there was a reduction in perioperative complications requiring intensive care admission among patients who had been assessed in the preoperative clinics.19 To specifically look at the impact of a vascular PAC on the outcome of vascular surgery patients, Cantley and colleagues20 studied the impact of this clinic in the 2year period after the opening of the clinic compared with the 2-year period before the clinic. In the 2 years before PAC, 234 patients were evaluated, and the mortality for open infrarenal aneurysm repair was 14.5%. In the subsequent 2 years after the opening of PAC, the mortality rate was 4.8%. Kamal and colleagues3 conducted a study to audit the effects of a specialized preoperative anesthesia clinic after hip and knee arthroplasty and revision arthroplasty. In the first part of the study, which was before the opening of the preoperative clinic, 298 patients who were admitted to the various intensive care units were evaluated. After the opening of the preoperative clinic, 1147 patients were evaluated. There was a statistically significant reduction in the admissions to postanesthesia care units from 22% to 10%, and a reduction in mortality from 6.1% to 1.2%, which was also statistically significant.3 Reduction in Cost

Preoperative clinic evaluation can decrease OR cancellations on the day of surgery.16,21 Every minute of preoperative time is worth $8 to $15, so delays or last minute cancellations lead to an enormous cost.11,21 There is an average of 97 minutes turnover time, which needs to be added to the cancellation of OR time leading to potentially avoidable cancellation costs of $776 in OR time alone.21 In a 3-month study by Correll and colleagues,22 647 patients who needed additional testing before surgery were identified in the preoperative clinic during the preoperative evaluation. If these patients had presented to the preoperative clinic on the day of surgery, it is likely that their surgeries would have been canceled or delayed, especially among the 191 (30%) of them who required new consultations. In a study to determine whether the ordering of tests by anesthesiologists in the preoperative clinic was cost effective, Fischer16 retrospectively evaluated 7889 patients. They found a 55.1% decrease in tests ordered leading to a hospital cost reduction of 59.3% or $112.09 per patient. At Stanford, this had a potential cost reduction of $1.01 million to the hospital.16 In a retrospective analysis of the annual cost and charges related to perioperative cost of surgical patients in a university setting in the United States, perioperative ward expenditures accounted for more than 30% of total incurred hospital costs.23 Therefore, a reduced hospital stay during the perioperative period could result in cost savings.

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Reduction in Length of Hospital Stay

O’Connor and colleagues24 conducted a study to investigate whether a newly established PAC reduces the preoperative inpatient stay. They found a significant reduction in the length of stay in the study period from 4.20 to 1.85 days after a major vascular surgery. Patients scheduled to undergo total hip replacement and who were given additional information preoperatively required less postoperative analgesia, had earlier mobilization, and a shorter length of stay compared with patients who received only routine advice before surgery.23 Kamal and colleagues3 found a reduction in the length of stay in a high-dependency unit from 2.1 to 1.6 days before and after the opening of a preoperative clinic. In the same study, intensive care unit unplanned admissions and intensive care unit length of stay also reduced significantly from 1.3% to 0.4%, and from 2.3 to 1.9 days, respectively. These decreases in length of stay also translate into cost savings.2 Decrease in Cancellation or Delays in Surgery on the Day of Surgery

An evaluation in the preoperative clinic can significantly impact case cancellations and delays on the day of surgery.12 Cancellations on the day of surgery may cause distress to the patient, waste OR time, disrupt bed management, and reduce OR efficiency.15 In a study to determine whether anesthesia preoperative clinics enhanced evaluation and had any effect on the cancellation of surgery, Fischer16 studied 14,207 patients. They found that 90% of the cancellations occurred just before surgery, resulting in OR downtime. In the year after the preoperative clinic was opened, there was a 87.9% decrease in day-of-surgery cancellations.16 Ferschl and colleagues5 in determining whether a visit to an APMC would reduce day-of-surgery case cancellations or case delays evaluated 6524 eligible cases. In the same-day surgery suite, 98 (8.4%) of 1164 APMC-evaluated patients were canceled, compared with 366 (16.2%) of 2252 in the non-APMC group (P<.001). In the general ORs, 87 (5.3%) of 1631 APMC-evaluated patients were canceled, compared with 192 (13%) of 1477 patients without a clinic visit (P<.001). For both operating areas, APMC patients had a significantly earlier room entry time than patients not evaluated in the APMC.11 One study reported 1 of 208 last minute cancellations of surgery by patients seen in the PAC clinic and listed for surgery compared with a 10% late cancellation in the 2 years before a functioning PAC for medical reasons.20 These results are consistent with the results reported by Magallanes6 in a study aimed at illustrating innovative practices implemented as a function of a newly formed perioperative medicine service at the Kaiser Permanente Bellflower medical center. In this study, out of 11,426 patients seen after the formation of the perioperative medicine service, only 3% of surgical procedures were documented as canceled compared with more than double the number 2 years before the perioperative medicine service. Increase in Surgical Case Procedures

An efficient and successfully run preoperative clinic would lead to an increase in surgical case procedures. In a study aimed at examining the perioperative process redesign in a 909-bed magnet university hospital, Ryan and colleagues4 found a 10% annual increase in surgical case procedures after the opening of a new diagnostic and surgical facility with the expansion of perioperative services to cover an additional floor.

Preoperative Clinics

Increase in Satisfaction

One of the main things reported in the study by Canty and colleagues25 was a high level of patient satisfaction with the preoperative clinic evaluation. In a survey of 80 patients seen in the preoperative clinic, 98% of patients in this study stated that they were highly satisfied with the service they had received. Identification and Management of New Medical Conditions

Correll and colleagues22 evaluated 5083 patients in a study to evaluate the value of preoperative clinic visits in identifying issues that can potentially impact OR efficiency. They found that preoperative evaluation can identify and resolve the most common types of medical issues that could account for most of the problems in the perioperative period.22 Preoperative clinics provide an opportunity to make changes in perioperative medical management, such as initiating b-blockers, change in anesthesia plan, or even alterations in anticoagulation regimens.22 Reduction in Excessive Preoperative Testing

Evidence supports the idea that preoperative assessment is best done by a focused history and physical, and only minimal, selective, further laboratory investigations.26 An estimated 60% to 70% of preoperative tests ordered are not necessary.27 In a study to examine the adverse effects of preoperative chest radiographs on 606 patents, 386 chest radiographs ordered did not have an appropriate indication. One patient had an abnormality that could have resulted in better care, but three patients had lung shadows that resulted in further invasive testing including thoracotomy with no discovery of disease, at the expense also of causing morbidity to the three patients including a pneumothorax.27 OPERATION AND MANAGEMENT OF PREOPERATIVE CLINICS

Who manages preoperative clinics? Most preoperative clinics are run by anesthesiologists and trained nurse practitioners. Some of the models are purely anesthesia preoperative evaluation clinics. These clinics are managed by the anesthesiologist, but usually it is a multidisciplinary team effort involving consultants from other medicine subspecialties, such as cardiology, hematology, and pulmonary medicine.11,16,24 Some models are completely managed by the medicine service,6,11 and a few models are run by surgeons. Clinics run by surgeons have been shown to be more costly, more tests are ordered, and the patients are less well prepared for anesthesia.20 In the surgeon-run clinics 63% more tests are ordered.20 The clinics run by internists are more likely to identify and intervene in medical conditions related to surgical outcomes.28 There is also evidence for decreased length of stay after thoracic and hip surgery.29 Clinics run by anesthesiologists had less perioperative mortality and morbidity.2 Various studies demonstrated a 73% decrease in preoperative consultations after the start of an anesthesia-run preoperative clinic,25 a 49% reduction in delays,30 and an 87.9% decrease in cancellations on the day of surgery.21 It has been proposed by some that anesthesiologists may be the ideal perioperative medicine specialist.21 It would be interesting to directly compare specific outcomes of clinics run by these different services. With the development of protocols for preoperative assessment

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and the integration of these protocols in the electronic medical record, the focus should be on the best evidence-based preoperative evaluation guidelines and implementation, rather than the specialty of the providers who run the clinic. Preoperative clinics provide a good resource to centralize medical information and coordinate perioperative care. Many institutions struggle with justification of resources for a preoperative clinic, but patients still need to be appropriately evaluated before surgery and it is more efficient to do so in a coordinated setting. Preoperative clinics are more a resource shift than new expenditure, although the evidence actually indicates preoperative clinics are more cost effective.12 Preoperative clinics provide a unique chance to intervene before the day of surgery and also facilitate the implementation of preoperative management guidelines. These clinics are associated with favorable outcomes, dramatic decreases in preoperative testing, infrequent subspecialty consultation, and shorter lengths of stay.

REFERENCES

1. Zonderland ME, Boer F, Boucherie RJ, et al. Redesign of a university hospital preanesthesia evaluation clinic using a queuing theory approach. Anesth Analg 2009;109(5):1612–21. 2. Starsnic MA, Guarnieri DM, Norris MC. Efficacy and financial benefit of an anesthesiologist-directed university preadmission evaluation center. J Clin Anesth 1997;9(4):299–305. 3. Kamal T, Conway RM, Littlejohn I, et al. The role of a multidisciplinary preassessment clinic in reducing mortality after complex orthopaedic surgery. Ann R Coll Surg Engl 2011;93(2):149–51. 4. Ryan J, Lewis C, Doster B, et al. Evaluating and improving the perioperative process: benchmarking and redesign of preoperative patient evaluations. Presented at the 45th Hawaii International Conference on System Sciences. Maui (HI), January 4–7, 2012. p. 2991–3000. 5. Ferschl MB, Tung A, Sweitzer B, et al. Preoperative clinic visits reduce operating room cancellations and delays. Anesthesiology 2005;103:855–9. 6. Magallanes MD. Kaiser Permanente Bellflower, Medical Center. Perioperative medicine. Medical release for dental procedure [form]. Bellflower (CA): Kaiser Permanente Bellflower Medical Center; 2001. 7. Holt NF, Silverman DG, Prasad R, et al. Preanesthesia clinics, information management, and operating room delays: results of a survey of practicing anesthesiologists. Anesth Analg 2007;104(3):615–8. 8. Lee JA. The anaesthetic out-patient clinic. Anaesthesia 1949;4:169–74. 9. Deutschman CS, Traber KB. Evolution of anesthesiology. Anesthesiology 1996; 85:1–3. 10. Tess AV, Smetana GW. Medical evaluation of patients undergoing electroconvulsive therapy. N Engl J Med 2009;360:1437–44. 11. Bader AM, Sweitzer B, Kumar A. Nuts and bolts of preoperative clinics: the view from three institutions. Cleve Clin J Med 2009;76(4):S104–11. 12. Fleisher LA, Beckman JA, Brown KA, et al. ACC/AHA 2007 guidelines on perioperative cardiovascular evaluation and care for noncardiac surgery: a report of the American College of Cardiology/American Heart Association Task Force on Practice Guidelines. J Am Coll Cardiol 2007;50:1707–32. 13. Archer T, Schmiesing C, Macario A. What is quality improvement in the preoperative period? Int Anesthesiol Clin 2002;40(2):1–16.

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14. Boedeker BH, Barak-Bernhagen MA, Miljkovic N, et al. Use of a cardiac algorithm in a preoperative evaluation clinic: a pilot study. Stud Health Technol Inform 2012; 173:75–7. 15. Lew E, Pavlin DJ, Amundsen L. Outpatient preanaesthesia evaluation clinics. Singapore Med J 2004;45:509–16. 16. Fischer SP. Development and effectiveness of an anesthesia preoperative evaluation clinic in a teaching hospital. Anesthesiology 1996;85(1):196–206. 17. Davis NJ, editor. Anaesthesia related mortality in Australia 1994–1996. Melbourne: Capitol Press; 1999. 18. Kluger MT, Tham EJ, Coleman NA, et al. Inadequate pre-operative evaluation and preparation: a review of 197 reports from the Australian Incident Monitoring Study. Anaesthesia 2000;55:1173–8. 19. Runciman WB, Webb RK. Australian Society of Anaesthetists Newsletter 1994;94: 15–7. 20. Cantley KL, Baker S, Perry A, et al. The impact of a consultant anaesthetist led pre-operative assessment clinic on patients undergoing major vascular surgery. Anaesthesia 2006;61:234–9. 21. Pollard JB, Olson L. Early outpatient preoperative anesthesia assessment: does it help to reduce operating room cancellations? Anesth Analg 1999;89(2):502–5. 22. Correll DJ, Bader AM, Hull MW, et al. Value of preoperative clinic visits in identifying issues with potential impact on operating room efficiency. Anesthesiology 2006;105(6):1254–9 [discussion: 6A]. 23. Macario A, Vitez TS, Dunn B, et al. Where are the costs in perioperative care? Analysis of hospital costs and charges for inpatient surgical care. Anesthesiology 1995;83:1138–44. 24. O’Connor DB, Cotter M, Treacy O, et al. An anaesthetic pre-operative assessment clinic reduces pre-operative inpatient stay in patients requiring major vascular surgery. Ir J Med Sci 2011;180(3):649–53. 25. Canty DJ, Royse CF, Kilpatrick D, et al. The impact of focused transthoracic echocardiography in the pre-operative clinic. Anaesthesia 2012;67(6):618–25. 26. Richman DC. Ambulatory surgery: how much testing do we need? Anesthesiol Clin 2010;28(2):185–97. 27. Kaplan EB, Sheiner LB, Boeckmann AJ, et al. The usefulness of preoperative laboratory screening. JAMA 1985;253:3576–81. 28. Devereaux PJ, Ghali WA, Gibson NE, et al. Physicians’ recommendations for patients undergoing noncardiac surgery. Clin Invest Med 2000;23:116–23. 29. Phy MP, Vanness DJ, Melton LJ III, et al. Effects of a hospital model on elderly patients with hip fracture. Arch Intern Med 2005;165:796–801. 30. Parker BM, Tetzlaff JE, Litaker DL, et al. Redefining the preoperative evaluation process and the role of the anesthesiologist. J Clin Anesth 2000;12(5):350–6.

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