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* From the Department of Anesthesia, Dalhousie University, Halifax, Nova Scotia;
the Department of Anesthesia, and
Medicine, University of Alberta, Edmonton, Alberta, Canada.
Address correspondence to: Dr. Marcello Tonelli, University of Alberta, 7-129 Clinical Science Building, 8440 - 112 Street, Edmonton, Alberta T6B 2B7, Canada. Phone: 780-407-8716; Fax: 780-407-7878; E-mail: mtonelli{at}ualberta.ca
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Abstract |
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Methods: We conducted a prospective analysis of consecutive patients seen by anesthesiologists before major non-cardiac surgery in a single month. Because not all patients undergoing major surgery were seen preoperatively by anesthesiologists, we also performed a retrospective analysis of patients who recently underwent such surgery. Data were collected on demographic information, cardiovascular risk factors, beta-blocker use, and perceived contraindications/barriers to beta-blocker use, using a validated instrument.
Results: The prospective phase studied 222 patients preoperatively, of whom 96 were suitable candidates for perioperative beta-blockade by the American College of Physician guidelines. The retrospective phase studied 200 patients, of whom 63 were suitable candidates, and assessed pre- and postoperative use of beta-blockade. 40.6% and 38.1% of suitable patients received preoperative beta-blockade in the two phases, respectively. Findings were similar in those undergoing vascular surgery, suggesting that perception of perioperative risk did not influence the decision to use beta-blockade. Beta-blockers were not prescribed preoperatively because of lack of knowledge about contraindications to beta-blockade, and anesthesiologist reluctance to prescribe oral medication to outpatients.
Discussion: Use of preoperative beta-blockade among suitable candidates appears to be approximately 40%. Anesthesiologists started preoperative beta-blockers infrequently even in patients without contraindications. These findings suggest that educating anesthesiologists about the perioperative use of beta-blockade may increase the use of this potentially beneficial strategy.
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Introduction |
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Perioperative beta-adrenergic receptor blockade has been shown to improve several important patient outcomes including myocardial infarction and mortality.6–11 Accordingly, clinical practice guidelines recommend the use of perioperative beta-blockade in high-risk patients undergoing major non-cardiac surgery, especially vascular surgery.12,13
There are few published data describing the frequency with which beta-blockers are administered to patients undergoing major non-cardiac surgery. However, clinical experience suggests these agents may be underutilized, and barriers to increasing perioperative use of beta-blockade have not been described. We designed this study to determine the frequency of perioperative beta-blockade in patients undergoing major non-cardiac surgery, and to identify factors that might be limiting its use.
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Methods |
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Eligible patients for the prospective phase included consecutive patients seen in the preanesthetic care unit during the four-week study period. Patients undergoing major non-cardiac surgery (ip, non-cystoscopic urological, intrathoracic, major vascular, or major orthopedic surgery) were eligible for inclusion.
The study questionnaire was validated using standard techniques.14 Questionnaire items were developed by an anesthesiologist (S.R.) and an internist (M.T.), and reviewed with colleagues to establish face and construct validity. The instrument was evaluated for accuracy (criterion validity) and test-retest reliability in a group of three simulated patients by six anesthesiologists who did not participate in the study. Each anesthesiologist completed the instrument twice for each simulated patient (eight weeks apart). Accuracy on the study items was 99.3% overall, and was 100% for beta-blocker use/non-use. Test-retest reliability was assessed using the kappa statistic, which was 0.87 for the three binary variables considered (beta-blocker use/non-use, decision to start beta-blockers preoperatively, presence/absence of coronary disease), indicating excellent reproducibility.
Retrospective phase
It was anticipated that not all candidates for perioperative beta-blockade would be seen in the preanesthetic care unit, and also that changes to perioperative medications might be made after the pre-admission visit (in hospital or at an appointment with another consultant). Therefore, an additional sample of 200 patients who had recently undergone major surgery was evaluated retrospectively, with emphasis on the high-risk population undergoing vascular procedures. Data from the computerized anesthesia recording system at the study institution were used to identify the names of consecutive patients who had recently undergone major surgery in the following distribution: 125 who underwent major vascular procedures; and 75 individuals who had undergone a major urologic, ip or thoracic procedure (25 of each). Because of the deliberate over-representation of patients undergoing vascular surgery in the retrospective phase, no statistical comparison has been made with the prospectively collected data.
Patient charts were reviewed and data were extracted by a single investigator (I.R.) using a standardized form. Information on patient demographics, cardiovascular risk factors, beta-blocker use (preoperative, intraoperative, postoperative), and contraindications to beta-blocker use (history of reversible airways disease, wheeze on physical examination, second or third degree heart block, decompensated congestive heart failure, heart rate < 60 beats·min–1) was collected. To maintain patient confidentiality, no information which could be used to identify individual subjects was included in the working copy of the study database.
In both phases of the study, American College of Physician (ACP) guidelines13 were used to determine which patients were candidates for perioperative beta-blockade. These guidelines specify that patients with known coronary disease (previous myocardial infarction, angina, or previous positive stress test) and those with two or more of the following risk factors (age 
65 yr, known hypertension, current smoking, history of hypercholesterolemia, or diabetes mellitus) should be considered for perioperative beta-blockade. In the current study, we also considered those with previous coronary revascularization to have coronary disease.
Statistical analysis
Variables were described using mean ± SD or proportions. Proportions were compared using Chi-square tests where appropriate. Analyses were performed using SAS 8.2 software (SAS Corporation, Cary, NC, USA).
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Results |
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In 34/96 (35.4%) of suitable candidates, beta-blockers were being taken at the time of the clinic visit, and beta-blockers were started preoperatively in an additional five such individuals, leaving 57 (59.4%) suitable candidates who apparently did not receive preoperative beta-blockade (Table II). Among these 57 patients, 12 had a blood pressure greater than 160/100, and 34 had a blood pressure greater than 140/80, suggesting that beta-blockade might have improved control of hypertension in addition to reducing perioperative risk. A list of the explanations provided by anesthesiologists for the non-prescription of beta-blockade to suitable candidates appears in Table III. The most common reason given for non-prescription was the absence of documented coronary disease. Other reasons cited included the concomitant use of other medications such as angiotensin-converting enzyme inhibitors or calcium channel blockers, reluctance to prescribe medications to outpatients, and concern that beta-blockade might precipitate hypoglycemia in diabetic patients.
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Retrospective phase
To ensure that data collected in the preanesthetic care unit reflected medications actually received in the perioperative period, we retrospectively collected information from 200 randomly selected patients who underwent major surgery at our institution. Demographic and clinical characteristics of these individuals appear in Table I
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Among the 200 patients, 63 were suitable candidates for perioperative beta-blockade. In this latter group, 24/63 (38.1%) received beta-blockers preoperatively, and an additional 16/63 patients (25.4%) were started on beta-blockers postoperatively. Thus, 40/63 (63.5%) of suitable candidates received beta-blockade at some time during the perioperative period.
Postoperative beta-blockade was started in 16/39 (41.0%) of patients who appeared to be suitable for this strategy. However, beta-blockers were also started postoperatively in 30 patients in whom their use was not specifically recommended by the ACP guidelines (n = 6), who had a contraindication to their use (n = 28) or both (n = 4).
Most of the patients in whom beta-blockade was started postoperatively (42/46, 91.3%) had undergone vascular surgery. Thus, 34% (42/125) of patients undergoing vascular surgery were started postoperatively on beta-blockers, and a total of 64% (80/125) received beta-blockade at some time during their hospital stay. Postoperative beta-blockade was started relatively infrequently among patients undergoing other types of surgery (4/75, 5.3%).
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Discussion |
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TOPAbstractIntroductionMethodsResultsDiscussionReferences |
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Anesthesiologists started preoperative beta-blockade infrequently in the preanesthetic care clinic, even in patients who appeared suitable candidates for this strategy and had known coronary disease. Interestingly, use of preoperative beta-blockade was similar in patients undergoing vascular surgery (who are known to be at high risk of cardiovascular events), compared with those undergoing other types of surgery. This suggests that anesthesiologists’ perceptions of perioperative risk may not influence the decision to prescribe beta-blockers.
Data on the perioperative use of beta-blockade are limited. A retrospective American study of 158 patients undergoing non-cardiac surgery found that the prevalence of beta-blocker use among apparently suitable patients was 37%, similar to our results.15 Likewise, a recent retrospective Canadian study of 143 patients undergoing general surgery found that 39% of those with coronary disease received perioperative beta-blockade.16 However, these articles did not explore barriers to the use of perioperative beta-blockade, and the former did not differentiate between pre-and postoperative use of beta-blockers. A third study found that the frequency of perioperative beta-blockade in patients seen in consultation by internists before non-cardiac surgery was only 11% but most participants were at low cardiovascular risk.17 Finally, Schmidt et al.15 concluded that the observed non-use of beta-blockade would be expected to result in at least 60 preventable deaths annually at their institution. In our opinion, this emphasizes the potential value of devising strategies to increase the use of this potentially effective therapy.
Why is the use of preoperative beta-blockade so low? In the current study, reasons given by anesthesiologists for non-prescription varied, but included concerns about the likely risk and/or benefit associated with therapy. Anesthesiologists also cited concern about prescribing oral medications to patients without scheduled follow-up. Although we did not attempt to determine whether anesthesiologists were unaware of the clinical practice guidelines recommending perioperative beta-blockade, this may have been a factor in some cases. Finally, even if aware of the practice guidelines, anesthesiologists’ perceptions about the value of treatment may have been influenced by knowledge of an on-going trial (the Perioperative Ischemic Evaluation - POISE - study) which is randomizing patients undergoing non-cardiac surgery to perioperative beta-blockade or placebo.
While prescription of preoperative beta-blockade was infrequent, the retrospective phase of our study suggests that a substantial proportion of patients are started on beta-blockers postoperatively, especially those undergoing vascular surgery. Although postoperative beta-blockade might prevent cardiovascular events compared with not starting beta-blockers at all, it is important to note that this is unproven. Therefore, it seems reasonable that perioperative beta-blockade should include both pre- and postoperative use of beta-blockers.
Previous work suggests that specific interventions may increase the proportion of patients who receive perioperative beta-blockade. For instance, a recent uncontrolled Canadian study found that an intervention aimed at anesthesiologists, internists, family physicians and postanesthesia care unit staff was associated with perioperative beta-blockade rates of 69%.18
Armanious et al.18 chose to have prescriptions for oral beta-blockers written by internists - which may have been important given the apparent reluctance of anesthesiologists to prescribe them in the current study. Some of the reasons given by anesthesiologists in our study for non-prescription of beta-blockers (concomitant use of other medications, potential for hypoglycemia, history of "chronic obstructive pulmonary disease", etc.) do not constitute true contraindications. These observations suggest that use of perioperative beta-blockade might be increased by a multidisciplinary approach and education directed at anesthesiologists, as well as family physicians, internists and surgeons.
However, interventions that rely simply on passive knowledge transfer may be insufficient, since many anesthesiologists consider themselves to be aware of recent literature on perioperative beta-blockade.19 In addition to targeted educational programs, Armanious et al. provided information sheets to patients and their family physicians, which may have improved long-term compliance with therapy. Based on lessons learned from other strategies aimed at changing physician behaviour, real-time reminders to prescribe beta-blockade and practice audits involving comparison with peers may also be beneficial.20 Finally, pre-printed protocols appear to increase utilization rates of beta-blockers after acute myocardial infarction,21 and should therefore be considered for perioperative beta-blockade as well.
The current study has a number of limitations which should be considered. First, it may have been preferable to follow those patients seen in the preoperative clinic into the postoperative period rather than obtaining two separate samples of patients. However, all data were contemporaneous and from a single institution, suggesting that this is unlikely to have affected our results. Second, the retrospective phase of the study was conducted by chart review, the limitations of which are well described. However, we attempted to minimize bias by randomly selecting cases from the operating room log, and with data extracted from the chart in standardized fashion by a single investigator. Although participating in the survey may have influenced the practice of anesthesiologists, this would have been expected to increase the use of beta-blockade, suggesting that our conclusions are unlikely to have been affected by this potential bias. Third, although other therapies such as alpha-2 adrenergic agonists might also improve perioperative outcomes,22 we did not collect information on their use in the current study. Fourth, we did not measure the number of doses of beta-blocker that patients received, and thus cannot determine the number of patients that received on-going beta-blockade as recommended by Mangano et al.8 Fifth, this was a single centre study, and collecting data from multiple tertiary centres would have improved the external validity of our findings. Sixth, asking anesthesiologists to specify patient characteristics that would have made them more likely to prescribe beta-blockers would have been potentially informative. Unfortunately we did not collect this information in the current work.
Despite these potential limitations, we developed and validated our instrument in accordance with accepted techniques, studied consecutive patients in the prospective phase, and randomly selected participants for the retrospective phase. In addition, all charts in the retrospective phase were reviewed by a single physician, which in our opinion is likely to have improved the quality of the data. We therefore believe that bias related to study design is unlikely to have significantly influenced our findings.
In summary, perioperative beta-blockade was used in approximately 40% of suitable patients undergoing non-cardiac surgery in a Canadian tertiary centre. Our data suggest that use of perioperative beta-blockade might be increased by educating physicians about the potential benefits of this strategy, as well as contraindications to its use.
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Footnotes |
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Acknowledgement of salary support: Dr. Tonelli was supported by the Alberta Heritage Foundation for Medical Research.
Accepted for publication January 12, 2004. Revision accepted May 14, 2004.
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2 Kazmers A, Striplin D, Jacobs LA, Welsh DE, Perkins AJ. Outcomes after abdominal aortic aneurysm repair: comparison of mortality defined by centralized VA patient treatment file data versus hospital-based chart review. J Surg Res 2000; 88: 42–6.[Medline]
3 Lawrence VA, Hilsenbeck SG, Mulrow CD, Dhanda R, Sapp J, Page CP. Incidence and hospital stay for cardiac and pulmonary complications after abdominal surgery. J Gen Intern Med 1995; 10: 671–8.[Medline]
4 Gilbert K, Larocque BJ, Patrick LT. Prospective evaluation of cardiac risk indices for patients undergoing non-cardiac surgery. Ann Intern Med 2000; 133: 356–9.
5 Mangano DT, Goldman L. Preoperative assessment of patients with known or suspected coronary disease. N Engl J Med 1995; 333: 1750–6.
6 Poldermans D, Boersma E, Bax JJ, et al. Bisoprolol reduces cardiac death and myocardial infarction in high-risk patients as long as 2 years after successful major vascular surgery. Eur Heart J 2001; 22: 1353–8.
7 Poldermans D, Boersma E, Bax JJ, et al. The effect of bisoprolol on perioperative mortality and myocardial infarction in high-risk patients undergoing vascular surgery. Dutch Echocardiographic Cardiac Risk Evaluation Applying Stress Echocardiography Study Group. N Engl J Med 1999; 341: 1789–94.
8 Mangano DT, Layug EL, Wallace A, Tateo I. Effect of atenolol on mortality and cardiovascular morbidity after noncardiac surgery. Multicenter Study of Perioperative Ischemia Research Group. N Engl J Med 1996; 335: 1713–20.
9 Zaugg M, Tagliente T, Lucchinetti E, et al. Beneficial effects from beta-adrenergic blockade in elderly patients undergoing noncardiac surgery. Anesthesiology 1999; 91: 1674–86.[Medline]
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12 Eagle KA, Berger PB, Calkins H, et al. ACC/AHA Guideline Update for Perioperative Cardiovascular Evaluation for Noncardiac Surgery – Executive Summary. A report of the American College of Cardiology/American Heart Association Task Force on Practice Guidelines (Committee to Update the 1996 Guidelines on Perioperative Cardiovascular Evaluation for Noncardiac Surgery). Anesth Analg 2002; 94: 1052–64.
13 Guidelines for assessing and managing the perioperative risk from coronary artery disease associated with major noncardiac surgery. American College of Physicians. Ann Intern Med 1997; 127: 309–12.
14 Streiner DL, Norman GR. Health Measurement Scales: A Practical Guide to their Development and Use, 2nd ed. Oxford: Oxford University Press; 1995.
15 Schmidt M, Lindenauer PK, Fitzgerald JL, Benjamin EM. Forecasting the impact of a clinical practice guideline for perioperative ß-blockers to reduce cardiovascular morbidity and mortality. Arch Intern Med 2002; 162: 63–9.
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18 Armanious S, Wong DT, Etchells E, Higgins P, Chung F. Successful implementation of perioperative beta-blockade utilizing a multidisciplinary approach. Can J Anesth 2003; 50: 131–6.
19 VanDenKerkhof EG, Milne B, Parlow JL. Knowledge and practice regarding prophylactic perioperative beta blockade in patients undergoing noncardiac surgery: a survey of Canadian anesthesiologists. Anesth Analg 2003; 96: 1558–65.
20 Majumdar SR, Soumerai SB. Why most interventions to improve physician prescribing do not seem to work. CMAJ 2003; 169: 30–1.
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22 Wijeysundera DN, Naik JS, Beattie WS. Alpha-2 adrenergic agonists to prevent perioperative cardiovascular complications: a meta-analysis. Am J Med 2003; 114: 742–52.[Medline]
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