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(Stroke. 1995;26:2040-2043.)
© 1995 American Heart Association, Inc.
Articles |
From the Units of Neurology (G.A., F.N., L.F., L.V., R.D.), Clinical Pharmacology and Therapy (L.B.), and Emergency Medicine (G.R.), S. Orsola-Malpighi Hospital, Bologna, Italy.
Correspondence to Dr Giuseppe Azzimondi, Servizio di Neurologia, Ospedale S. Orsola-Malpighi, Via Albertoni 15, 40138 Bologna, Italy.
| Abstract |
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Methods We analyzed the data of 183 patients included in a prospective observational prognostic study. Vital status at 30 days was considered the main outcome and was obtained for all patients. Age, level of consciousness, and glycemia at the time of hospitalization were considered covariates for an exact logistic regression analysis. The maximum temperature recorded during the first 7 days dichotomized as "no or low fever" versus "high fever" was added to the model. Death within 10 days, taken as a secondary outcome suggestive of death from neurological causes, was analyzed with exact permutation tests.
Results Of the 183 patients analyzed in this study,
43% had fever during the first 7 days after hospitalization. The mean
value of the maximum temperature recorded during the first 7 days
in the 78 febrile patients was 38.3°C, and the median was 37.9°C.
Onset of fever occurred in only 15% of febrile patients during the
first day and in 49% on the second. The prognostic roles of age, level
of consciousness, and glycemia were confirmed by exact logistic
regression. Degree of consciousness impairment was the strongest
prognostic variable, with an odds ratio (OR) of 11.4 (95%
confidence interval [CI], 4.4 to 31.6). High fever (maximum
temperature recorded during the first 7 days
37.9°C) was an
independent factor for a worse prognosis, with an OR of 3.4 (95% CI,
1.2 to 9.5). The OR of dying within 10 days versus dying between 11 and
30 days was 4.9 (95% CI, 1.2 to 25.2) in patients with high fever with
respect to all other patients.
Conclusions Fever in the first 7 days was an independent predictor of poor outcome during the first month after a stroke. No data were available on the underlying causes of fever, but the higher risk of death in the first 10 days, most frequently attributed to neurological mechanisms, suggested that high temperature was an independent component of poor prognosis and not only an epiphenomenon of other complications in the course after a stroke. In agreement with animal studies, we found that patients with higher temperature had a worse stroke outcome.
Key Words: prognosis stroke outcome temperature
| Introduction |
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On the basis of these studies, fever is empirically considered prognostic of poor outcome in patients with acute stroke, and there is general agreement that fever of any cause should be treated with antipyretic agents to avoid its possible deleterious consequences.
In this report, data from a prospective observational prognostic study of patients admitted for acute stroke to the S. Orsola-Malpighi Community Teaching Hospital in Bologna, Italy, were analyzed to evaluate the role of fever on outcome.
| Subjects and Methods |
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Study Sample
Each day one half of the patients admitted to the emergency
department of the hospital with a suspected diagnosis of acute stroke,
excluding those with subarachnoid hemorrhage, were
randomized into the study by extracting the patients' names from a
box. This randomization was necessary because we did not have the
resources to apply the intensive follow-up schedule in real time to
all consecutive patients. The study period went from February 1, 1992,
to February 28, 1993, the day the sample size planned for the overall
study was reached. Each randomized patient was examined within 48 hours
by one of three neurologists (G.A., L.F., F.N.), who diagnosed the
patients according to the criteria for stroke proposed by the World
Health Organization.7 Two hundred nineteen patients not
meeting these criteria were excluded. All the 204 patients diagnosed as
having an acute stroke and included in the first stage of the study
represented the initial sample for this
analysis.
Data Collection
Variables recorded in the general database included date
of birth, sex, time of onset of symptoms and of arrival in the
hospital, risk factors for cerebrovascular diseases, laboratory tests,
electrocardiography, CT scan, medical therapy,
rehabilitation, and nursing. Level of consciousness was classified
according to Plum and Posner.8 The Canadian Neurological
Scale for fully alert or drowsy patients and the Glasgow Coma Scale for
patients with a consciousness impairment greater than drowsiness were
applied at days 1, 3, 10, 17, and 30 after hospitalization. The Barthel
Index score was determined before admission and after 1, 3, and 6
months. Axillary temperature on the unaffected side of the body was
recorded at least twice daily during the first 7 days of
hospitalization according to the schedules of the various wards. MTEMP
was defined as the maximum temperature observed during the first 7
days. Day of onset of fever (up to day 7) was also recorded.
Statistical Methods
Three variables associated with outcome were considered
candidates for covariates.9 10 11 Patients were classified
according to age (
75 versus >75 years), level of consciousness at
first examination (fully alert versus drowsy or comatose), and glycemia
(
6.7 versus >6.7 mmol/L) at the time of hospitalization. Vital
status at 30 days was considered the main outcome. Absence of fever was
defined as MTEMP of 37.2°C or lower. The median value of MTEMP in
patients with fever was taken as the threshold between low and high
fever; the latter included the threshold value.
After descriptive documentation of the relationship among the variables, exact logistic regression was performed and the exact odds ratios (ORs) estimated by means of the program LOGXACT.12 Student's unpaired t test was used to compare means, and the Mann-Whitney nonparametric test was used to compare medians.
To estimate the importance of covariates, hierarchical backward stepwise regression was performed, with all interactions in the first model (saturated model). Nonsignificant interactions and factors were removed to arrive at a simple model, to which fever could then be added. Logistic regression with trichotomized fever described by two dichotomized variables was used to decide how many dichotomized variables, if any, to keep in the final model.
Death within 10 days was taken as a secondary outcome, suggestive of death from neurological causes. MTEMP was dichotomized on the basis of the results obtained from LOGXACT. Odds of dying within 10 days compared with dying between 11 and 30 days were analyzed in the group of patients who died within 30 days. Only the most important covariate from the first analysis was put into the model, to keep cell size adequate.
The aforementioned odds of dying within 10 days compared with dying between 11 and 30 days obtained from this fit were estimated with the use of permutation tests performed "exactly" by STATXACT.13 The effect of the stratification factor was evaluated. Exact confidence intervals (CIs) were provided.
| Results |
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Prognostic Roles of Age, Consciousness Impairment, and
Glycemia
Lethality of stroke ranged from 3% in younger fully conscious
patients with normal glycemia to 91% in older patients with impaired
consciousness and high glycemia. The effects of the three factors were
confirmed by exact multivariate logistic regression.
None of the interactions among the factors in the hierarchical models
were significant. Their effect was to add "noise" and enlarge the
CIs, and they were all removed from the final model (Table 2
). Degree of consciousness impairment
was the strongest prognostic variable, with an OR of 11.4 (95% CI,
4.4 to 31.6).
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Prognostic Role of Body Temperature
Lethality increased overall and in almost all strata as a function
of temperature. Patients were divided into three subgroups, with no
fever (
37.2°C), lower fever (37.3°C to 37.8°C), and higher
fever (
37.9°C) than the median value. Both trichotomized MTEMP as a
factor and "high fever" versus "low or no fever" were
statistically significant. Ockham's razor suggested the use of the
simplest model, which is shown in Table 3
. Observed and
predicted mortality are compared in the Figure
. With
respect to the model without MTEMP (Table 2
), the
prognostic values of age, degree of consciousness impairment, and
glycemia were very similar in order of magnitude, and the OR of the
dichotomized factor high fever versus low or no fever was 3.4 (95% CI,
1.2 to 9.5) (Table 3
).
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Body Temperature and Early Death
A concentration of deaths within 10 days compared with those
occurring between 11 and 30 days is evident among the patients with
high fever, both in alert patients and in those with consciousness
impairment (Table 4
). On the basis of the
logistic regression model shown in Table 3
, MTEMP was dichotomized as
no or low fever versus high fever.
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The exact permutation test with stratification on level of consciousness gave the common OR as 4.6 (95% CI, 1.1 to 23.1). Without stratification, the OR was 4.9 (95% CI, 1.2 to 25.2), very similar to that found with the stratified analysis.
| Discussion |
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37.2°C versus >37.2°C) did not enter the model. It was not
possible to estimate a threshold above which fever seemed detrimental.
Probably a range of cutoffs would have given significant results. A
dose effect, if present, should be detectable in a larger
sample. In our analysis we did not separate ischemic from hemorrhagic stroke because CT scan was performed in only 60% of our patients and therefore we could not estimate the different consequences of fever in the two types of stroke. This fact depended on the main design of the study, for which we needed to avoid whatever bias could have modified the diagnostic and therapeutic approaches to the patients before introducing the guidelines.
Our data did not provide information on underlying causes of fever in our patients. Thus, we could not exclude a priori that temperature of at least 37.9°C in the first 7 days after a stroke as a marker of poor prognosis might to some extent or entirely be an epiphenomenon of some common causes of fever (eg, pulmonary or urinary tract infections, sepsis, or pulmonary embolism from deep venous thrombosis). We could also not distinguish cases in which the stroke was elicited by infectious disease. However, if fever were the etiologic mechanism of the stroke, this could not have occurred except in some of the 12 patients who had fever during the first day of hospitalization.
We observed a concentration of early as opposed to later deaths among patients with fever of at least 37.9°C. Patients still alive at 30 days were irrelevant to the comparison. The good agreement between the stratified and unstratified analyses suggested an underlying relationship between high fever and early death.
High fever thus seemed to be associated with a higher probability of early death. This was evidence that fever of at least 37.9°C indicated poor early prognosis even without a consideration of its causes. Since the majority of the experimental studies documented the direct effects of temperature on neurological damage,1 2 our data suggest that fever could worsen prognosis through direct neurological damage.
Only two studies have investigated the prognostic significance of fever in stroke. Hindfelt5 found that a mean body temperature above 37.5°C from any cause in the first 7 days was associated with poor prognosis at 2 months after the stroke. However, his study was retrospective, the sample excluded patients who died within 2 months, and the measurement of outcome was not validated, so that his conclusions are not easily generalized to the whole population of stroke patients.
In a prospective study of 281 patients with stroke, Terent and Andersson6 found that in patients with mean body temperature of 38°C or more during the first week, chest x-ray films revealed bronchopneumonia in half. Fever as defined above indicated a significantly worse prognosis, but their data did not distinguish between the consequences of complete paresis and body temperature. We could not consider complete paresis because of its strong association with level of consciousness impairment, reported as having a superior prognostic value for early mortality.9
Przelomski et al14 prospectively investigated the frequency and causes of fever in a sample of 104 consecutive stroke patients. In particular, these authors studied the possible association between fever, almost always secondary to infections, and the size of the lesion. Comparison with our study is difficult because the authors excluded brain stem infarcts and intraventricular hemorrhage, conditions in which "neurogenic fever" is most likely, and they did not evaluate the prognostic value of fever.
In conclusion, this is the first prospective study specifically investigating the prognostic role of fever in patients with acute stroke. Although we did not distinguish between hemorrhagic and ischemic strokes and no data were available on the underlying causes of fever, our results indicated that patients with higher temperature have a worse prognosis. Further studies distinguishing between the two types of stroke would be useful to investigate the relationship between intracranial hemorrhage and rise in temperature and to evaluate the role of infections. Our results support a lowering of fever, as previously recommended in almost all guidelines for medical therapy of stroke. Controlled trials to evaluate the effects of lowering body temperature are also necessary.
| Acknowledgments |
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Received March 6, 1995; revision received August 8, 1995; accepted August 16, 1995.
| References |
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