Estimation of glomerular filtration rate and assessment of Risk of stroke in an emergency setting^?

To the Editor,

In 2010, in the United States, about 795 000 people had a stroke, and about 80% of them are new cases; in Italy, the cases of stroke are about 195 000, with an incidence of 2.15 to 2.54 new cases-1000 inhabitants per year [1]. Stroke is the third cause of death, after myocardial infarction and cancer, with an associated high incidence of disability and average cost of EUR40 000 to EUR50 000 per patient per year [2]. The social impact of this disease in general population suggests the need to adequately inform the patient about the risk of developing the disease, because this could favor appropriate changes in lifestyle habits, reduction of Blood pressure , smoking, and the incidence of diabetes mellitus and other cardiovascular diseases. The assessment of the risk of first stroke is recommended by the American Stroke Association in the latest Stroke guidelines recently published in 2011 [3], and tables for evaluation of the 10-year risk of stroke in general population have been proposed. The guidelines suggest that emergency medical services (EMS) could be an important setting where patients could be screened, and renal function should be evaluated as well. Nishijima et al [4] suggested that evaluation of creatinine should be performed in African American population with asymptomatic elevated BP levels presenting in EMS. Moreover, Lin et al [5] reported an independent relationship between blood urea nitrogen/creatinine ratio and stroke-in-evolution.

We conducted a study aimed to investigate the relationship between the percentage of 10-year risk of stroke in a cohort of consecutive patients who presented in EMS for symptoms not related to cerebrovascular disease and renal function. Our study included 203 patients (140 were males; 69%) in whom all the information necessary to assess the risk of first stroke could be collected according to the American Heart Association guidelines. Mean age was 73 +- 10 years; systolic BP was 134.6 +- 18.9 mm Hg in those on Antihypertensive therapy and 132.9 +- 16.3 mm Hg in subjects not taking Antihypertensive drugs; and smoking history was detected in 27% of cases, diabetes mellitus in 18.7%, cardiovascular diseases history in 38.9%, atrial fibrillation in 13.3%, and left ventricular hypertrophy in 38.9%. In addition, we also collected the data of serum creatinine, whose mean value was 1.12 +- 0:51 mg/dL, to calculate glomerular filtration rate (GFR) by the Chronic Kidney Disease Epidemiology Collaboration formula [6]. Mean GFR value was 73.2 +- 24 mL/min per 1.73 m². Subsequently, the subjects were classified into 5 stages of chronic kidney disease (CKD) [7]: 25.2% were in stage 1; 51.5%, in stage 2; 16.8% in stage 3; and 6.4%, in stage 4. In our population, the mean 10-years risk of

^? Funding support: This work was supported, in part, by a scientific grant “FAR- Fondo di Ateneo per la Ricerca scientifica” from the University of Ferrara, Italy.

Fig. 1 Distribution of 10-year risk of stroke in the studied population.

stroke was 26.5% +- 19.8%, with a distribution of risk shown in Fig. 1. The risk of stroke, as suggested by the weight of the scoring system, tended to increase with age and was higher in patients older than 70 years and in male subjects, especially for risk percentage closer to the average population (Fig. 2). In our study, we found a relationship between the 10-year risk of stroke and the stage of CKD, as shown in Fig. 3 (Kruskal- Wallis test, P = .022). The degree of renal function could be a risk factor increasing the risk of stroke, as shown in stages 1 to 3 (the lack of effect in CKD stage 4 may depend on the small sample size).

It has been reported that in subjects who had experienced a cerebrovascular event, reduced GFR is independently related to mortality [8]. In a meta-analysis of 284 672 patients (7863

Fig. 2 Ten-year risk of stroke according to age and sex of the 203 patients.

Fig. 3 Ten-year risk of stroke in the different stages of CKD (Kruskal-Wallis test; P = .022).

with stroke) [9], the incidence of stroke was increased in the group of patients with GFR lower than 60 mL/min per 1.73 m², with a relative risk of 1.43 (95% confidence interval, 1.31- 1.57). Moreover, the relative risk was even higher if GFR was lower than 40 mL/min per 1.73 m² (1.77; 95% confidence interval, 1.32-2.38). The correlation between renal function and risk of stroke was also reported by Wannamethee et al

[10] in 7690 men. In the group of patients with major ischemic event (n = 287), higher Creatinine levels were associated with an increased risk of Cerebrovascular events, independently of BP, and the risk of developing a cerebrovascular event was higher than any other cardiovascular diseases. Cerebrovascu- lar disease is a frequent finding in uremic subjects, with an estimated prevalence in Europe as high as 16.5% of the dialysis population, as stated by the Dialysis Outcomes and Practice Patterns Study II [11]. However, most of these patients have Multiple comorbidities in association with cerebrovascular disease. All these data suggest that Frequency of stroke increases with worsening renal failure, and calculation of risk of stroke and GFR could identify subjects at higher risk. Emergency medical service physicians could play an important role because the routinely use of these easy calculations might implement preventive appropriate thera- peutic measures, such as prescription of antihypertensive drugs, statins, or Antiplatelet agents.

Alfredo De Giorgi MD Fabio Fabbian MD Marco Pala MD Ruana Tiseo MD

Francesco Portaluppi MD Roberto Manfredini MD

Clinica Medica, University of Ferrara

44100 Ferrara, Italy E-mail address: [email protected]

doi:10.1016/j.ajem.2011.04.012

References

1. Lenti G, Agosti M, Massucci M, et al. Developing a minimum data set for stroke patients assessment: the Protocollo di Minima per l’Ictus (PMIC) as a starting point towards an Italian Stroke registry. Eur J Phys Rehabil Med 2008;44:263-9.
2. Candelise L, Micieli G, Sterzi R, Morabito A. stroke units and general wards in seven Italian regions: the PROSIT study. Neurol Sci 2005;26: 81-8.
3. Goldstein LB, Bushnell CD, Adams RJ, et al. Guidelines for the primary prevention of stroke: a guideline for healthcare professionals from the American Heart Association/American Stroke Association. Stroke 2011;42:517-84.
4. Nishijima DK, Paladino L, Sinert R. Routine testing in patients with asymptomatic Elevated blood pressure in the ED. Am J Emerg Med 2010;28:235-42.
5. Lin LC, Yang JT, Weng HH, Hsiao CT, et al. Predictors of early clinical deterioration after acute ischemic stroke. Am J Emerg Med doi:10.1016/j.ajem.2009.12.019.
6. Levey AS, Stevens LA, Schmid CH. A new equation to estimate glomerular filtration rate. Ann Intern Med 2009;150:604-12.
7. Kidney National Foundation. K/DOQI clinical practice guidelines for chronic kidney disease: evaluation, classification, and stratification. Am J Kidney Dis 2002;36(Suppl 1):S1-S266.
8. Ani C, Ovbiagele B. Relation of baseline presence and severity of renal disease to long-term mortality in persons with known stroke. J Neurol Sci 2010;288:123-8.
9. Lee M, Saver JL, Chang KH, et al. Low glomerular filtration rate and risk of stroke: meta-analysis. BMJ 2010;341:c4249. doi:10.1136/bmj. c4249.
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11. Goodkin DA, Bragg-Gresham JL, Koenig KG, et al. Association of comorbid conditions and mortality in hemodialysis patients in Europe, Japan, and the United States: the Dialysis Outcomes and Practice Patterns Study (DOPPS). J Am Soc Nephrol 2003;14:3270-7.

    The double Lung point

    To the Editor,

    We appreciate the interest of the authors regarding our recent article on the “double lung point.” We will try to answer several questions raised by the letter, giving more technical details.

    “Only 1 lung point can be present”: The definition of lung point given by Lichtenstein et al [1] includes the words “…on a particular location,” referring to the probe position on the chest wall and not to the sign. Of course, the lung point is detected at any particular point in time; but by definition, it is moving and changing projection on the chest wall with respiratory movements. When the air layer of a pneumotho- rax is floating free in the pleural space, we find nonsliding in the dependent region of the thorax and sliding at the border of the layer. In the Supine patient, we detect nonsliding from the parasternal to a chest area that is located further laterally and inferiorly when the pneumothorax is larger. The lung point will be visualized as the classic alternate for the sliding and nonsliding pattern, the sliding being detectable only on 1 extremity of the probe. Now, in some conditions, the air