486 Correspondence

diagnosis of pulmonary embolism. Am J Respir Crit Care Med 2002; 165:345 - 8.

[6] Sijens PE, Oudkerk M, Berghout A, et al. Comparison of a quantitative latex and a quantitative ELISA plasma d-dimer assay in the exclusion of segmental and subsegmental pulmonary embolism. Thromb Hae- most 2001;86:1580 - 2.

Emergency short-stay unit as an effective alternative to in-hospital admission for acute chronic obstructive pulmonary disease exacerbation

To the Editor,

Observation and short-stay units are becoming common in hospitals and are an increasingly important component of the modern emergency department (ED) because they are an alternative to admission or discharge [1]. Acute exacerba- tion of chronic obstructive pulmonary disease (COPD) causes frequent hospitalizations in winter when there is often a coexisting in-hospital bed crisis and ED over- crowding [2]. However, there are few data to establish the duration of hospitalization in individual patients to achieve maximal benefit and to identify those patients with COPD suitable for early discharge from the hospital [3].

The objectives of the study were to determine whether a new emergency department short-stay unit (EDSSU) was an effective alternative to conventional hospital units (HUs) for patients with exacerbation of COPD and to identify the clinical factors predictive of short stay at the time of presentation to the ED in those patients.

A comparative analysis (v² or t test) was used to identify differences between patients admitted to the HU (n = 1961) and those admitted to the EDSSU (n = 545) during the winter months (November 1, 1997, to March 31, 1998, and

November 1, 1998, to March 31, 1999). The study was performed at Bellvitge Hospital, a 1000-bed teaching tertiary care referral center in Barcelona, Spain. The ED attends to approximately 110000 emergency visits per year, excluding pediatrics and obstetrics. We retrospectively studied the characteristics of patients hospitalized with an acute exacerbation of COPD between November 1, 1996, and March 31, 1999 (n = 2506). We chose charts of patients from the hospital discharge database and selected according to the ninth revision of the International Classification of Diseases codes [4]. We used the computerized database to obtain outcome data on all patients. Clinical and demo- graphic factors were available through chart review. Patients were excluded from the study if they had pulmonary diagnoses at the time of hospital admission other than or in addition to COPD or if they were intubated and ventilated on the day of admission. Discharge medications for both groups included prednisone and adrenergic and steroid metered-dose inhalers with a spacer device.

Statistically significant differences were found for mean age (HU: 69.5 years vs EDSSU: 63.7 years; P b.05), Pao₂ of

This study has been presented at the American College of Emergency Physicians 2001 Research Forum, October 15 to 16, 2001, Chicago, Ill.

60 mm Hg or less (HU: 59.6% vs EDSSU: 48.3%; P b.001),

long-term oxygen therapy (HU: 13.4% vs EDSSU: 8.8%; P =

.004), mean length of stay (HU: 12.0 days vs EDSSU: 3.4 days; P b .001), mortality (HU: 8.1% vs EDSSU: 1.7%; P b.001), and readmission rate of 10 days or less (HU: 7.0% vs EDSSU: 9.9%; P = .02). There were no statistically significant differences regarding sex, chronic cor pulmonale, and number of associated conditions. The mean hospital stay in HU was not significantly modified over the period of the study (1996 = 11.9 days; 1997 = 12.1 days; 1998 = 11.0 days). The strengths of our study include a large sample size and follow-up data on repeat ED visits after discharge. We demonstrated that the introduction of an EDSSU at a Tertiary university hospital was associated with a decrease in the length of stay of patients with COPD exacerbation, along with a corresponding increase in the rate of repeat visits to the ED within 10 days of discharge. It is likely that part of the increased length of stay for the HU group is a feature of the nature and function of inpatient services. The mean hospital length of stay in the HU was not significantly modified over the period of the study, which rules out a possible bias effect of less seriously ill patients with COPD admitted to the new EDSSU. The increasing occurrence of relapse during the 10- day period is remarkable and suggests the need for intensified ambulatory care or home care in the weeks after a short

admission in an EDSSU.

However, several important limitations must be addressed. First, pulmonary function and the presence of hypercarbia (Paco₂ of 50 mm Hg or more) were not recorded to compare disease severity between the 2 groups. Other authors have described poor outcomes after hospitalization for exacerba- tion of COPD associated with hypercarbia [5]. Second, we cannot exclude the possibility that some patients had repeat visits to their physicians’ offices or other institutions in the 10 days after hospital discharge. Last, as we did not conduct a formal economic analysis, further work is needed to quantify the economic impact of the introduction of an EDSSU in the management of COPD.

We conclude that selected emergency patients with acute exacerbation of COPD can be effectively and safely treated in the EDSSU. The identification of clinical factors predictive of short stay at the time of presentation to the ED in patients with acute exacerbation of COPD, such as age of less than 65 years, Pao₂ of greater than 60, and absence of long-term oxygen therapy proved to be an effective and safe measure in emergency care and a helpful intervention that alleviated winter in-hospital bed crises.

Albert Salazar MD Antoni Juan MD

Department of Emergency Medicine

Hospital de Bellvitge University of Barcelona

Feixa Llarga s/n 08907 L’Hospitalel Barcelona, Spain

E-mail address: [email protected]

Correspondence 487

Ricard Ballbe MD

Department of Clinical Documentation

Hospital de Bellvitge University of Barcelona

Feixa Llarga s/n 08907 L’Hospitalel Barcelona, Spain

Xavier Corbella MD Medical Direction Hospital de Bellvitge University of Barcelona

Feixa Llarga s/n 08907 L’Hospitalel Barcelona, Spain

doi:10.1016/j.ajem.2007.03.010

References

1. Graff L. Overcrowding in the emergency department: an international symptom of health care system failure. Am J Emerg Med 1999;17:208 - 9.
2. Hanratty B, Robinson M. Coping with winter bed crises. New surveillance systems might help. Br Med J 1999;319:1511 - 2.
3. Kong GK, Belman MJ, Weingarten S. Reducing length of stay for patients hospitalized with exacerbation of COPD by using a practice guideline. Chest 1997;111:89 - 94.
4. International Classification of Diseases, 9th Revision, Clinical Mod- ifications. 4th ed. Salt Lake City7 Med-Index Publications, Utah; 1993.
5. Connors Jr AF, Dawson NW, Thomas C, et al. Outcomes following acute exacerbation of severe chronic obstructive lung disease. The SUPPORT investigators (Study to Understand Prognoses and Prefer- ences for Outcomes and Risks of Treatments). Am J Respir Crit Care Med 1996;154:959 - 67.

Differences between various glomerular filtration rate calculation methods in predicting patients at risk for Contrast-induced nephropathy

To the Editor,

Band et al [1] make an important point when they alert readers to the hazards of predicting renal function by a single creatinine measurement, which can be affected by multiple factors. We write to emphasize several other points that are also worthy of note in measuring glomerular filtration rate (GFR) in patients undergoing contrast-related Diagnostic procedures in the emergency setting.

Band et al used the Cockcroft-Gault equation to calculate the GFR levels of the study patients. The Cockcroft-Gault equation uses age, weight, and serum-measured Creatinine levels. But it may overestimate GFR because of the free secretion of creatinine from the proximal tubules. The Cockcroft-Gault equation has not been adjusted according

to the body surface area [2]. A more current GFR calculation formula is the Modification of Diet in Renal Disease (MDRD) equation [3]. For serum creatinine in milligram per deciliter, the estimating equation is GFR = 175 x standardized Scr^-1.154 x age^-0.203 x 1.212 (if the subject is black) x 0.742 (if the subject is female) [3]. Body surface area and also ethnicity were taken into account in the MDRD equation because black people on average have higher creatinine levels than white people because of having increased muscles mass. The correlation between estimated GFR and measured GFR is closer with the MDRD (R² = 0.88) than with the Cockcroft-Gault equation (R² = 0.83). Fifty- nine percent of the population studied by Brand et al was African American, so different GFR results may be calculated by using these 2 equations. We can also see these differences by citing an example from the present study. For instance, a 43-year-old (the mean age of the study population) 70-kg male patient with a creatinine level of 1.5 mg/dL (the critical creatinine level), as Dr Band pointed out, has a GFR level of

62.87 mL/min if it is calculated by the Cockcroft-Gault equation. However, the same patient will have a GFR level of

65.68 mL/min if he is an African American and 54.28 mL/min (which means impaired renal function if he is not an African American) if it is calculated by the MDRD equation.

Finally, some patients with impaired renal function may be overlooked by using only the Cockcroft-Gault equation. The MDRD equation should also be used with the Cockcroft-Gault equation to prevent missing patients with impaired renal function and critical creatinine levels.

Cenker Eken MD Department of Emergency Medicine Akdeniz University Medical Faculty

07059 Antalya, Turkey E-mail address: [email protected]

?Isa Kilicaslan MD

Department of Emergency Medicine

Guven Hospital Ankara, Turkey

E-mail address: [email protected] doi:10.1016/j.ajem.2007.03.023

References

1. Band RA, Gaieski DF, Mills AM, et al. Discordance between serum creatinine and creatinine clearance for identification of ED patients with abdominal pain at risk for contrast-induced nephropathy. Am J Emerg Med 2007;25:268 - 72.
2. Stevens LA, Coresh J, Greene T, et al. Assessing kidney function- measured and estimated glomerular filtration rate. N Engl J Med 2006;354:2473 - 83.
3. Levey AS, Coresh J, Greene T, et al. Expressing the modification of diet in renal disease study equation for estimating glomerular filtration rate with standardized serum creatinine levels. Clin Chem 2007 [Epub ahead of print].