Brain Trauma Stroke
Table 1: Centers for Disease Control and Prevention Criteria for Clinically Defined Pneumonia
Signs/Symptoms/Laboratory For any patient, at least one of
the following: • fever (>38ºC)
• leukopenia (
Two or more serial chest radiographs with a least one of the following: • new or progressive and persistent infiltrate
leukocytosis (>12,000 WBC/mm3) • consolidation • for adults ≥70 years of age, altered mental status with no other recognised cause
• cavitation • in patients without underlying
pulmonary or cardiac diseases (e.g. respiratory distress syndrome, bronchopulmonary dysplasia, pulmonary oedema or chronic obstructive pulmonary diseases), one definitive chest radiograph is acceptable
WBC = white blood cells. Adapted from Centers for Disease Control and Prevention, 2009.
Table 2: Centers for Disease Control and Prevention Criteria for Asymptomatic Bacteriuria
Signs/Symptoms
Patient has not had an indwelling urinary catheter within seven
Laboratory
Patient has had at least two positive cultures, that is ≥105
days before the first positive culture micro-organisms/ml of urine with and patient has: • no fever (>38ºC) • no urgency
• no frequency • no dysuria • no suprapubic tenderness
Urinary Tract Infection
It is important to differentiate between UTI and asymptomatic bacteriuria. Asymptomatic bacteriuria (see Table 2) is a common phenomenon in populations with structural or functional abnormalities of the genito-urinary tract, but even healthy individuals frequently have positive urine cultures. Asymptomatic bacteriuria is seldom associated with adverse outcomes.
Symptomatic UTI has been defined by the CDC, as depicted in Table 3. One should note that in stroke patients clinical signs of UTI (e.g. dysuria or urgency) are of only minor diagnostic value, as stroke patients are often unconscious or dysphasic. Thus, laboratory and microbiological testing are of enhanced relevance. Interestingly, diagnosis of UTI can also be a decision of the treating physicians.
Prediction of Post-stroke Infections Early identification of patients at high risk of post-stroke infection may promote and justify intensive monitoring and tailored anti-infective treatment.
Pneumonia
Post-stroke pneumonia is usually explained as a result of aspiration due to neurological deficits, such as impaired level of consciousness, disturbed protective reflexes20
or dysphagia.21
Additional risk factors for the SAP have been identified: stroke severity, stroke subtype, lesion size, mechanical ventilation, age, gender and history of diabetes.21–24
A study by Walter et al. 40
repeated isolation of the same micro-organisms and no more than two species of micro-organism
Table 3: Centers for Disease Control and Prevention Criteria for Symptomatic Urinary Tract Infection
Signs/Symptoms
Patient has at least one of the following signs: • fever (>38°C) • urgency
• frequency Laboratory
Patient has had a positive culture, that is ≥105 micro-organisms/ml of urine with repeated isolation of the same micro-organisms and no more than two species of micro-
• dysuria organisms or at least one of • suprapubic tenderness
the following: • positive dipstick for leukocyte esterase and/or nitrate
• pyuria (urine specimen with ≥10 WBC/ml or ≥3 WBC/high-power field of unspun urine)
• organisms seen on Gram stain of unspun urine
• at least two urine cultures with repeated isolation of the same uropathogen (Gram-negative bacteria or Staphylococcus saprophyticus) with ≥102 micro-organisms/ml in non-voided specimens
• ≤105 micro-organisms/ml of a single uropathogen (Gram-negative bacteria or S. saprophyticus) in a patient being treated with an effective antimicrobial agent for a urinary infection
• physician diagnosis of a urinary tract infection
• physician institutes appropriate therapy for a urinary tract infection
WBC = white blood cells. Adapted from Centers for Disease Control and Prevention, 2009.
underlined the pivotal role of post-stroke dysphagia with a 10-fold relative risk of post-stroke pneumonia.23
The first published scoring
system to predict post-stroke pneumonia was developed including National Institutes of Health Stroke Scale (NIHSS), age, sex, mechanical ventilation and dysphagia.25
Sellars et al. established a
scoring system by identifying age ≥65 years, dysarthria, modified Rankin Scale (mRS) ≥4, Abbreviated Mental Test (AMT)
However, both
scores need further refinement and prospective validation in large multicentre trials.
The impact of aspiration on the risk of post-stroke pneumonia is indisputable. However, aspiration alone is not sufficient to explain the high incidence of pneumonia in acute stroke, as about 50% of healthy subjects also aspirate pharyngeal secrets every night to a similar extent to stroke patients without developing pneumonia.27,28 Clinical and experimental evidence suggests that acute ischaemic central nervous system (CNS) injury is associated with temporary immunodeficiency and that an impaired antibacterial host defence is an important factor for the increased susceptibility to infection after CNS injury.6,10–12,29
In experimental stroke models, cerebral ischaemia induces a rapid suppression of cellular immune responses in lymphatic organs – in
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