Sufentanil

Approximately one third of patients undergoing coronary artery bypass graft surgery will develop atrial fibrillation (AF). (1) AF is more common in elderly patients and in patients with COPD or hypertension. Its occurrence, and particularly its recurrence, were associated with encephalopathy, strokes, renal dysfunction, infection, in-hospital deaths, more use of CT scans and noncardiac ultrasonography, and longer ICU and hospital stays. (1,2) However, patients with AF were less likely to have myocardial infarctions or congestive heart failure, and they underwent fewer echocardiograms and EEGs. (1,2) Additionally, AF is a risk factor for late mortality. (2)

While a variety of medicines, including amiodatone, have been shown to decrease the occurrence of AF, (3,4) disagreement persists about the cost benefits of prophylaxis with amiodarone. Daoud et al, (5) using the sum of direct variable, fixed direct costs, and indirect costs, found that amiodarone prophylaxis decreased hospital costs by $8,161 per patient. In a mathematical modeling exercise using departmental cost/charge ratios and physician work relative value units, Mahoney et al (6) claimed that the use of IV amiodarone for universal prophylaxis in patients undergoing coronary artery bypass graft surgery would increase in-hospital costs by $24,934 for each episode of AF prevented. Other studies, using a variety of analyses, have found no difference in costs between groups receiving amiodarone and control groups. (7-10) Into this controversy step Kerstein et al (see page 716) with a novel and convenient method for administering amiodarone that decreased the incidence of AF from 26 to 6%. Given the assoeiation between AF and morbidity and mortality, the authors should be encouraged to perform a randomized, double-blinded, placebo-controlled study of amiodarone and AF. The authors also report that universal prophylaxis is very cost-effective, saving $1,242 per treated patient. However, the authors do not determine the cost. They multiplied the average length of hospital stay by a constant charge per day to arrive at a total "cost." There are three main problems with this, as follows: (1) length of stay correlates poorly with direct variable cost after cardiac surgery (11); (2) most of a hospital charge consists of fixed or indirect costs that are not saved by preventing AF; and (3) their calculation does not capture any costs related to the adverse effects of amiodarone. Only if the use of amiodarone increases length of stay is it recognized as a cost. Amiodarone can cause pulmonary infiltrates, thyroid dysfunction, heart block, and ventricular dysrhythmias. In this length of stay-based accounting system, all extra tests and procedures related to the adverse effects of amiodarone have no cost. They are free, which is obviously not correct.

Then how shall we determine the costs or savings of using amiodarone to prevent AF? Cost studies are usually divided into the following four types: cost-minimization; cost-benefit; cost-utility; and cost-effectiveness. Cost-minimization studies compare two or more equally efficacious therapies to determine which is the least expensive. Cost-benefit studies necessitate converting all outcomes (eg, pain, emesis, renal failure, myocardial infarction, and death) to a monetary value. Cost-utility studies determine the cost of a utility metric, such as $10,000, for each quality-adjusted year of survival. Cost-effectiveness studies determine the monetary cost of preventing unwanted outcomes (eg, death, ventilated associated pneumonia, and AF). Recommendations on conducting cost-effectiveness studies have been promulgated by the US Public Health Service (12) and the European Society of Intensive Care Medicine. (13) We would use a cost-effectiveness study to determine the monetary cost for each case of AF prevented. The results can range from negative cost (ie, amiodarone use saves more money than it costs, as found by Kerstein et al), to positive cost (ie, amiodarone use increases costs but at least prevents AF), (6) to infinite cost (ie, amiodarone use costs more and does not prevent AF). Next, we would determine whose perspective is determining cost. The view can be that of the hospital, the insurance company, the patient, or the society. They are not interchangeable. An action that reduces hospital cost, such as early hospital discharge, may increase the cost to the patient or insurance company by, for example, the need to pay for home health care or a stay at an extended-care facility.

But what is a cost? Problems arise when costs and charges are used synonymously. At my hospital, I frequently see sales representatives who compare the purchase price of their item to the hospital charges in computing savings that allegedly would occur by buying their item. Charges are established unilaterally by the hospital, and have a complex and sometimes arbitrary relationship to hospital costs. Some studies use a conversion factor (ie, hospital wide or department cost/charge ratio) to convert charges to costs. However, the ratio varies front hospital to hospital, and within hospitals From department to department, and may not adequately reflect costs. (14)

Costs are usually divided into fixed vs variable costs and direct vs indirect costs. Average, total, marginal, semi-fixed, and opportunity costs also may be used. Physicians, accountants, and economists may have different definitions for the same term. (15) Fixed costs do not vary with physician care decisions or treatment. These may include administrative salaries, bond payments, and facility upkeep. Fixed costs are not apportioned evenly. Traditionally, the operating rooms and the ICU have been assigned a disproportionately large share, thus making their charges higher than the same service performed elsewhere with an identical labor and material direct variable cost. This is why using charges or cost/ charge ratios will produce a savings when a patient is transferred from an ICU bed to a stepdown bed. But, if no changes are made in the patient's care, and therapy and the nurse/patient ratio do not change, the hospital does not save any money by this transfer. Variable costs occur based on what is or is not done for a particular patient (eg, administering amiodarone or obtaining a radiograph). Certain items in which the per patient variable cost is very small and no one tracks its individual use, such as laundry, are frequently included as a fixed cost. Some costs, such as labor, may be fixed or variable depending on circumstances. For example, if a patient is discharged from the hospital early and the nurse is sent home without pay for the remainder of the shift, the nurse's pay is a variable cost. It changes with patient activity. However, if work rules prevent sending the nurse home without pay, no money is saved by the early hospital discharge and the nurse's pay is a fixed cost. Direct, variable costs may be only a small component of total hospital costs (16% in one study (16)). In one study, (11) the median direct variable hospital cost of patients undergoing cardiac surgery, from preoperative evaluation to hospital discharge, using a sufentanil-isoflurane-based anesthetic was $5,943, which is much less than the charge or average reimbursement, which must cover the overhead. Marginal cost is the cost (or savings) of having one more (or one fewer) ease of an activity. Or how much more (or less) money is left in the hospital's checkbook if I prevent one case AF? The marginal cost, which may not be constant but may vary with activity, of doing one more operation (or preventing one more ease of AF) is less than the average cost of that operation and is much less than the charge for that operation. Airlines understand this concept and set their prices accordingly. Airlines are similar to hospitals in that most of their expenses (ie, the planes, airport facilities, and the reservation system) are fixed. Direct variable expenses are comparatively small. The price of a standby ticket may be only a small fraction of a full fare, yet the amine makes a marginal profit on the standby ticket because the price of the ticket exceeds the marginal cost of flying one more customer.

The benefit of using a detailed accounting system to measure marginal or direct variable costs, while more difficult and challenging than using a charge-based or length of stay-based system, is that it provides a much more accurate determination of what is in the checkbook and what is actually spent or saved by using amiodarone prophylaxis for AF. There are two main limitations to using or conducting a cost study. (1) Costs may vary from one hospital to another. They have different purchasing contracts for goods and services. Different staffing levels affect marginal costs and the labor component of direct variable costs. These may affect the generalizability of the results and may need confirmation at your hospital before you implement changes. (2) The hospital may have old costs listed by the accounting system that have not been updated to reflect current market conditions, which would produce inaccurate results.

In conclusion, Kerstein et al describe a novel way to prevent AF. However, I urge them to conduct a proper randomized, double-blinded, placebo-controlled study that is adequately powered to find an economically meaningful difference in cost, and that defines the perspective and cost for their upcoming GAP II study.

REFERENCES

(1) Mathew JP, Fontes ML, Tudor IC, et al. A multicenter risk index for atrial fibrillation after cardiac surgery. JAMA 2004; 291: 1720-1729

(2) Villareal RP, Hariharan R, Liu BC, et al. Postoperative atrial fibrillation and mortality after coronary artery bypass surgery. J Am Coll Cardiol 2004; 43:742-748

(3) Auer J, Weber T, Berent R, et al. A comparsion between oral antiarrhythmic drugs in the prevention of atrial fibrillation after cardiac surgery: the pilot study of prevention of postoperative atrial fibrillation (SPPAF), a randomized, placebo controlled trial. Am Heart J 2004; 147:636-643

(4) Kuralay E, Cingoz F, Kilic S, et al. Supraventricular tachyarrythmia prophylaxis after coronary artery surgery in chronic obstructive pulmonary disease patients (early amiodarone prophylaxis trial). Eur J Cardiothorac Surg 2004; 25:224-230

(5) Daoud E, Strickberger S, Man K, et al. Preoperative amiodarone as prophylaxis against atrial fibrillation after heart surgery. N Engl J Med 1997; 337:1785-1791

(6) Mahoney EM, Thompson TD, Veledar E, et al. Cost-effectiveness of targeting patients undergoing cardiac surgery for therapy with intravenous amiodarone to prevent atrial fibrillation. J Am Coll Cardiol 2002; 40:737-745

(7) Guarnieri T, Nolan S, Gottlieb S, et al. Intravenous amiodarone for the prevention of atrial fibrillation after open heart surgery: the Amiodarone Reduction in Coronary Heart (ARCH) trial. J Am Coll Cardiol 1999; 34:334-339

(8) Redle J, Khurana S, Marzan R, et al. Prophylactic oral amiodarone compared with placebo for prevention of atrial fibrillation after coronary artery bypass surgery. Am Heart J 1999; 138:144-150

(9) Lee S-H, Chang C-M, Lu M-J, et al. Intravenous amiodarone for prevention of atrial fibrillation after coronary artery bypass grafting. Ann Thorac Surg 2000; 70:157-161

(10) Giri S, White CM, Dunn AB, et al. Oral amiodarone for prevention of atrial fibrillation after open heart surgery: the Atrial Fibrillation Suppression Trail (AFIST); a randomized placebo-controlled trial. Lancet 2001; 357:830-836

(11) Engoren M, Luther G, Fenn-Buderer N. A comparison of fentanyl, sufentanil, and remifentanil for fast-track cardiac anesthesia. Anesth Analg 2001; 93:859-864

(12) Siegel JE, Weinstein MC, Russell LB, et al. Recommendations for reporting cost-effectiveness analyses: Panel on Cost-effectiveness in Health and Medicine. JAMA 1996; 276: 1339-1341

(13) Jegers M, Edbrooke DL, Hibbert CL, et al. Definitions and methods of cost assessment: an intensivist's guide; ESICM section on health research and outcome working group on cost effectiveness. Intensive Care Med 2002; 28:680-685

(14) 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; 83:1138-1144

(15) Watcha MF, White PF. Economies of anesthetic practice. Anesthesiology 1997; 86:1170-1196

(16) Roberts RR, Frutos PW, Ciavarella GG, et al. Distribution of variable vs fixed costs of hospital care. JAMA 1999; 281:644-649

Dr. Engoren is in the Departments of Anesthesiology and Internal Medicine at St. Vincent Mercy Medical Center and is a Clinical Assistant Professor at the Ohio University College of Osteopathic Medicine.

Reproduction of this article is prohibited without written permission from the American College of Chest Physicians (e-mail: permissions@chestnet.org).

Correspondence to: Milo Engoren, MD, FCCP, Departments of Anesthesiology and Internal Medicine, St. Vincent Mercy Medical Center, 2213 Cherry St, Toledo, OH 43608; e-mail: engoren@ pol.net

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