Nosocomial pneumonia after acute stroke: implications for neurological intensive care medicine

Serum albumin level and nosocomial pneumonia in stroke patients

Hypoalbuminemia is associated with increased risk of infections. The aim of this study was to determine if serum albumin level is an independent predictor of nosocomial pneumonia in stroke patients. Data of 705 consecutive ischemic stroke patients admitted within 24 h after stroke onset were analyzed retrospectively. Serum albumin level was measured within 36 h after stroke onset. Nosocomial pneumonia was found in 10.5% of stroke patients. Patients with pneumonia had significantly lower serum albumin level than those without pneumonia (31.9 +/- 7.5 g/l vs. 35.5 +/- 6.9 g/l) and serum albumin level was associated with risk of pneumonia on multivariate analysis (OR: 0.95, 95% CI: 0.91-0.98). Our results show that serum albumin level is an independent predictor of nosocomial pneumonia in stroke patients.

Clinical Consequences of Infection in Patients With Acute Stroke

Background and Purpose— It is unsettled whether stroke-associated infection (SAI) is an independent prognostic factor, and a recent clinical trial failed to show that antibiotic prophylaxis prevented SAI. Contrarily, this trial suggested that antibiotic prophylaxis impaired clinical recovery. We sought to evaluate the predisposing factors and clinical consequences of SAI to gather additional insight on the need of exploring other antibiotics in acute stroke.

Methods— Between March 2001 and April 2002, 229 consecutive patients were admitted into the neurological wards within 24 hours of stroke onset. Demographics, risk factors, National Institutes of Health Stroke Scale (NIHSS) score, vital data, imaging, and laboratory findings were prospectively evaluated. SAI was treated as early as possible. Multivariate regression analyses assessed predisposing factors of SAI and the independent association between SAI and poor stroke outcome at day 7 (Rankin >2).

Results— Sixty (26%) patients developed SAI, most frequently chest infections, and within 3 days of stroke onset. Tube feeding (odds ratio [OR], 3.2; 95% CI, 1.3, 7.8) was the strongest predisposing factor of SAI. Poor outcome at hospital discharge was associated to baseline NIHSS score (OR, 10.0; 95% CI, 1.5, 100) and tube feeding (OR, 16.6; 95% CI, 2.9, 100.0), adjusted for confounders including antibiotic use. SAI was not independently associated to poor outcome (OR, 0.9; 95% CI, 0.9, 1.0).

Conclusions— SAI is a marker of the severity of stroke without an independent outcome effect when it is promptly treated. These results support current stroke guidelines that advise prompt treatment of infection and warn against antibiotic prophylaxis. Yet, these recommendations should not prevent the performance of acute stroke trials assessing the value of antibiotics with acknowledged neuroprotective properties.

Mouse strains differ in their susceptibility to poststroke infections

OBJECTIVE

Severe infections, in particular pneumonia, have a major impact on the clinical management and outcome of stroke patients. In a mouse model we have recently demonstrated that stroke induces immunodepression which can result in life-threatening infections. Here, we investigated whether the susceptibility to infections after stroke is strain dependent.

METHODS AND RESULTS

Mice from 129SV, C57/B6, and Balb/C strains were subjected to experimental stroke by filament occlusion of the middle cerebral artery (MCAO) for 60 min. Infarct volumes were measured 3 days after MCAO. Microbiological assessment was based on cultures of bronchoalveolar lavage (BAL), lung tissue and blood of animals obtained 3 days after stroke. Three days after stroke 129SV mice did not only develop bacterial chest infection, but also had a strongly increased susceptibility to bacteremia. In contrast, C57BL/6 and Balb/C mice acquired bacterial lung infections only. In addition, bacterial load in BAL was significantly higher in 129SV mice than in the other mice strains. These differences in susceptibility to infection did not correlate with infarct volumes.

CONCLUSIONS

Stroke-associated pneumonia developed in three commonly used mouse strains while severity of infections differed between strains. Since infections affect outcome, monitoring of infections is highly relevant for the interpretation of results in experimental stroke research.

New treatments in acute ischemic stroke

Since the advent of intravenous thrombolytic therapy with recombinant tissue plasminogen activator (tPA) for acute ischemic stroke, there has been a marked change in our management approach to patients with acute ischemic stroke. Although the major part of our focus in treating patients with stroke remains prevention of complications post-stroke and reduction of stroke recurrence, there is a paradigm shift to immediate "clot" lysis. This concept is being actively promoted through certification of institutions as stroke centers in order to increase the number of patients with stroke treated in an ultra-rapid fashion. However, options for acute treatment remain limited. Other than aspirin, the only US Food and Drug Administration-approved agent for acute ischemic stroke is intravenous tPA. Some physicians treating patients with acute ischemic stroke still frequently use heparin and low-molecular-weight heparinoids, but there are no firm data to support routine use of this drug class. However, a number of new lytic agents and strategies are being pursued. Some of these treatments, such as intra-arterial chemical thrombolysis or mechanical intra-arterial thrombolysis, are available only at specialized stroke centers. In addition, new antithrombotic agents are being studied. Drugs that can rescue neurons from impending hypoxia-ischemia cell death represent the "holy grail" of acute stroke therapy. To date, these "neuroprotectant" strategies have been unsuccessful, although this concept remains under active investigation in animal and human trials.

Sensitization to brain antigens after stroke is augmented by lipopolysaccharide

After stroke, the blood-brain barrier is transiently disrupted, allowing leukocytes to enter the brain and brain antigens to enter the peripheral circulation. This encounter of normally sequestered brain antigens by the systemic immune system could therefore present an opportunity for an autoimmune response to brain to occur after stroke. In this study, we assessed the immune response to myelin basic protein (MBP) in animals subjected to middle cerebral artery occlusion (MCAO). Some animals received an intraperitoneal injection of lipopolysaccharide (LPS; 1 mg/kg) at reperfusion to stimulate a systemic inflammatory response. At 1 month after MCAO, animals exposed to LPS were more likely to be sensitized to MBP (66.7% versus 22.2%; P=0.007) and had more profound and persistent neurologic deficits than non-LPS-treated animals. Exposure to LPS was associated with increased expression of the costimulatory molecule B7.1 early after stroke onset (P=0.009) and increased brain atrophy 1 month after MCAO (P=0.03). These data suggest that animals subjected to a systemic inflammatory insult at the time of stroke are predisposed to develop an autoimmune response to brain, and that this response is associated with worse outcome. These data may partially explain why patients who become infected after stroke experience increased morbidity.

Central nervous system injury-induced immune deficiency syndrome

Infections are a leading cause of morbidity and mortality in patients with acute CNS injury. It has recently become clear that CNS injury significantly increases susceptibility to infection by brain-specific mechanisms: CNS injury induces a disturbance of the normally well balanced interplay between the immune system and the CNS. As a result, CNS injury leads to secondary immunodeficiency - CNS injury-induced immunodepression (CIDS) - and infection. CIDS might serve as a model for the study of the mechanisms and mediators of brain control over immunity. More importantly, understanding CIDS will allow us to work on developing effective therapeutic strategies, with which the outcome after CNS damage by a host of diseases could be improved by eliminating a major determinant of poor recovery.

Surveillance of nosocomial infections in a neurologic intensive care unit

OBJECTIVE

To assess data on the epidemiology of nosocomial infection (NI) among neurologic intensive care patients.

DESIGN

Prospective periodic surveillance study.

SETTING

An 8-bed neurologic intensive care unit (ICU).

PATIENTS

All those admitted for more than 24 hours during five 3-month periods between January 1999 and March 2003.

METHODS

Standardized surveillance within the German infection surveillance system.

RESULTS

Three hundred thirty-eight patients with a total of 2,867 patient-days and a mean length of stay of 8.5 days were enrolled during the 15-month study period. A total of 71 NIs were identified among 52 patients. Urinary tract infections (UTIs) were the most frequent NI (36.6%), followed by pneumonia (29.6%) and bloodstream infections (BSIs) (15.5%). The overall incidence and incidence density of NIs were 21.0 per 100 patients and 24.8 per 1,000 patient-days, respectively. Incidence densities were 9.8 UTIs per 1,000 urinary catheter-days (CI95, 6.4-14.4), 5.6 BSIs per 1,000 central venous catheter-days (CI9s, 2.8-10.0), and 12.8 cases of pneumonia per 1,000 ventilation-days (Cl95, 8.0-19.7). Device-associated UTI and pneumonia rates were in the upper range of national and international reference data for medical ICUs, despite the intensive infection control and prevention program in operation in the hospital.

CONCLUSION

Neurologic intensive care patients have relatively high rates of device-associated nosocomial pneumonia and UTI. For a valid comparison of surveillance data and implementation of targeted prevention strategies, we would strongly recommend provision of national benchmarks for the neurologic ICU setting.

Update on respiratory management of critically ill neurologic patients

Respiratory failure complicates a number of acute neurologic conditions, most notably neuromuscular diseases (eg, Guillain-Barré syndrome and myasthenia gravis) and stroke. In addition, pulmonary complications, particularly pneumonia and atelectasis, are fairly common in patients with these diagnoses; their prevention and early recognition are crucial to avoid detrimental consequences. This review discusses recent studies related to predictors of respiratory failure and pneumonia, strategies of respiratory care and ventilatory support, functional prognosis, and withdrawal of mechanical ventilation in patients with acute neuromuscular respiratory failure and stroke.

Intensive care of the acute stroke patient

Advances in the diagnosis, monitoring, and treatment of stroke have led to the development of specialized units capable of employing new technologies for acute stroke care. This new approach to treatment of the stroke patient has resulted in improved clinical outcomes and a better understanding of the factors that contribute to neurological recovery. Intensive monitoring after treatment, management of medical comorbidities, anticipation of known complications, and prompt treatment of a worsening condition each contribute toward this higher standard of care. While improved outcomes are associated with care in a dedicated stroke unit, many of the therapies employed have not been rigidly tested in randomized controlled trials. The stroke unit creates a unique environment for research and holds an academic responsibility to continue to validate its treatment and explore innovative therapies for treatment of acute stroke. The goal of this article is to discuss the current care of the acute stroke patient and to introduce novel therapies currently being investigated.

Relationship between nosocomial infection and mortality in a neurology intensive care unit in Turkey

Few previous studies have evaluated the relationship between nosocomial infection and mortality in a neurology intensive care unit (ICU). In this study, patients treated for more than 24h in the neurology ICU of the Ankara Training and Research Hospital, Turkey were followed until death or two days after discharge by prospective daily surveillance. The study period was 14 months. One hundred and sixty-nine ICU-acquired infections occurred in 74 (38.9%) of 190 patients during 2006 patient-days. The overall rate of ICU-acquired nosocomial infection was 88.9/100 patients and 84.2/1000 patient-days. While the overall mortality rate was 60%, mortality in patients with nosocomial infections was 69%. In univariate analysis, infection (nosocomial and community-acquired) (P=0.002), nosocomial infection (P<0.05), mechanical ventilation (P<0.0001), presence of two or more underlying diseases (P=0.01), parenteral nutrition (P<0.0001), steroid treatment (P=0.003) and a low Glasgow Coma Scale (GCS) score (P=0.0001) were identified as risk factors for mortality. Stepwise logistic regression analysis showed nosocomial infection (P<0.05), mechanical ventilation (P=0.009), the presence of two or more underlying diseases (P<0.05) and a low GCS score (P=0.0001) to be risk factors for ICU mortality. It was concluded that nosocomial infection increases the risk of mortality by a factor of 1.69. The impact of nosocomial infection on mortality in our ICU was higher in patients with high GCS scores and patients aged between 66 and 75 years. In particular, nosocomial infection increased mortality among patients with less severe illnesses.

Vertebral Artery-Posteroinferior Cerebellar Artery Aneurysms: Clinical and Lower Cranial Nerve Outcomes in 52 Patients

OBJECTIVE:

To identify factors predictive of postoperative lower cranial nerve palsy (LCNP) among patients undergoing surgery for vertebral artery (VA)- posteroinferior cerebellar artery (PICA) aneurysms. The natural history of this LCNP is defined, and its effect on postoperative patient course is analyzed. No similar study has been described in the literature.

METHODS:

Fifty-two patients with VA-PICA aneurysms, who were treated surgically between 1996 and 2002, were retrospectively studied to identify factors contributing to postoperative LCNP. The effect of LCNP on intensive care unit stay and development of nosocomial pneumonia also was analyzed. All analyses were performed with Fisher's exact test.

RESULTS:

Postoperative LCNP occurred in 25 patients (48.1%) with VA-PICA aneurysms. Of the factors investigated, the use of temporary or total occlusion was associated with increased incidence of postoperative LCNP (P &lt; 0.001). The average length of stay in the intensive care unit was 13.8 days for patients with LCNP defined as moderate to severe, compared with 7.92 days for patients with LCNP defined as none or mild (P = 0.0014). Nosocomial pneumonia occurred only in patients with moderate to severe LCNP (P = 0.022). Postoperative LCNP resolved completely within 3 months in 12 patients (48%) and within 6 months in 19 patients (76%).

CONCLUSION:

The results of this study can help to identify the effect and natural history of LCNP after surgical clipping of VA-PICA aneurysms. This information may assist neurosurgeons in expediting treatment, decrease the cost and length of hospital stays, and result in improved outcomes.

Pathophysiology of stroke: lessons from animal models

The current pathophysiological understanding of stroke is substantially based on experimental studies. Brain injury after cerebral ischemia develops from a complex signaling cascade that evolves in an at least partially unraveled spatiotemporal pattern. Early excitotoxicity can lead to fast necrotic cell death, which produces the core of the infarction. The ischemic penumbra that surrounds the infarct core suffers milder insults. In this area, both mild excitotoxic and inflammatory mechanisms lead to delayed cell death, which shows biochemical characteristics of apoptosis. While brain cells are challenged by these deleterious mechanisms, they activate innate protective programs of the brain, which can be studied by means of experimentally inducing ischemic tolerance (i.e., ischemic preconditioning). Importantly, cerebral ischemia not only affects the brain parenchyma, but also impacts extracranial systems. For example, stroke induces a dramatic immunosuppression via an overactivation of the sympathetic nervous system. As a result, severe bacterial infections such as pneumonia occur. Complex signaling cascades not only decide about cell survival, but also about the neurological deficit and the mortality after stroke. These mechanisms of damage and endogenous protection present distinct molecular targets that are the rational basis for the development of neuroprotective drugs.

Nosocomial infections and immunity: lesson from brain-injured patients

Of brain-injured patients admitted to intensive care units, a significant number acquires nosocomial infections. Increased susceptibility to infectious agents could, at least partly, be due to transient immunodepression triggered by brain damage. Immune deficiency in patients with severe brain injury primarily involves T cell dysfunction. However, humoral and phagocytic deficiencies are also detectable. Activation of the hypothalamo-pituitary-adrenal axis and the sympathetic nervous system plays a crucial role in brain-mediated immunodepression. In this review we discuss the role of immunodepression in the development of nosocomial infections and clinical trials on immunomodulation in brain-injured patients with hospital-acquired infections.

Pneumonia in acute stroke patients fed by nasogastric tube

BACKGROUND

Aspiration pneumonia is the most important acute complication of stroke related dysphagia. Tube feeding is usually recommended as an effective and safe way to supply nutrition in dysphagic stroke patients.

OBJECTIVE

To estimate the frequency of pneumonia in acute stroke patients fed by nasogastric tube, to determine risk factors for this complication, and to examine whether the occurrence of pneumonia is related to outcome.

METHODS

Over an 18 month period a prospective study was done on 100 consecutive patients with acute stroke who were given tube feeding because of dysphagia. Intermediate outcomes were pneumonia and artificial ventilation. Functional outcome was assessed at three months. Logistic regression and multivariate regression analyses were used, respectively, to identify variables significantly associated with the occurrence of pneumonia and those related to a poor outcome.

RESULTS

Pneumonia was diagnosed in 44% of the tube fed patients. Most patients acquired pneumonia on the second or third day after stroke onset. Patients with pneumonia more often required endotracheal intubation and mechanical ventilation than those without pneumonia. Independent predictors for the occurrence of pneumonia were a decreased level of consciousness and severe facial palsy. The NIH stroke scale score on admission was the only independent predictor of a poor outcome.

CONCLUSIONS

Nasogastric tubes offer only limited protection against aspiration pneumonia in patients with dysphagia from acute stroke. Pneumonia occurs mainly in the first days of the illness and patients with decreased consciousness and a severe facial palsy are especially endangered.

Hospital-acquired pneumonia

PURPOSE OF REVIEW

The aim of this review is to summarize recent developments regarding risks factors, clinical features, management and antimicrobial resistance, and prevention of hospital-acquired pneumonia.

RECENT FINDINGS

Risk factors for hospital-acquired pneumonia developing in specific ICUs (neurologic and cardiovascular surgery) were reported. Characteristics of pneumonia acquired in general wards but requiring ICU admission were studied. Analysis of the impact of reintubation on pneumonia occurrence demonstrated that only reintubation after accidental extubation increases the risk. Early administration of adequate antibiotic(s), associated with a deescalating strategy, remains the only measure directly amenable to modification by clinicians that decreases the infection-related mortality. Numerous data emphasized the recommendation that guidelines for hospital-acquired pneumonia therapy should be updated and customized to local patterns to improve the level of adequacy of antimicrobial treatment. A 8-day treatment regimen could be proposed when pneumonia is not caused by a nonfermenting, gram-negative bacilli. In cases of pneumonia caused by methicillin-resistant Staphylococcus aureus, linezolid, compared with vancomycin, significantly increases the rates of cure and survival. Semirecumbent positioning in all eligible patients, sucralfate rather than H2 antagonists in patients at low to moderate risk of gastrointestinal bleeding, and, in selected patients, aspiration of subglottic secretions and oscillating beds are the measures proposed to prevent the development of ventilator-associated pneumonia. Conversely, the routine or indiscriminate use of selective digestive decontamination is not recommended.

SUMMARY

In our opinion, the optimization of the length of treatment and the reduction of mortality with linezolid in staphylococcal pneumonia are two major recent developments.

Critical care management of acute ischemic stroke

PURPOSE OF REVIEW

To review and examine the efficacy of recently described medical and surgical interventions after acute ischaemic stroke using data from well conducted, clinical trials and systematic reviews. This review will consider recently published or updated articles.

RECENT FINDINGS

As therapeutic options evolve, including thrombolysis and anti-platelet therapy, prevention of secondary insults, becomes increasingly important during periods of acute cerebral ischaemia in order to prevent worsening of the neurological injury. As in other acute medical conditions, urgent management of patients with acute ischaemic stroke should begin with the assessment and treatment of the airway, breathing, circulation, temperature, and blood glucose control.

SUMMARY

It is estimated that there will be 8.5 million patients with acute ischaemic stroke in the European Union and the USA over the next decade, and of these, about one and a half million will die within six months of stroke onset. Of those who survive, about one third will depend on other people for help with their activities of daily living. Future treatment strategies are likely to involve agents that re-canalise vessels and minimise further neuronal damage.

Treatment or prevention of complications of acute ischemic stroke

Both neurologic and medical complications influence outcome after stroke. Space-occupying supratentorial infarcts can cause transtentorial or uncal herniation, which leads to death. Treatments aimed at reducing intracranial pressure in patients with such infarcts are of unproven value. Mass-producing cerebellar infarction may lead to brainstem compression and obstructive hydrocephalus. These lesions often are treated surgically. Although anticonvulsants are not indicated for prophylaxis, the occurrence of epileptic seizures mandates treatment to prevent recurrences. Depression is common in the acute stage of stroke, but is probably not more prevalent after stroke than after myocardial infarction. Although dysphagia is common, it usually is a transient problem. Patients with a decrease of consciousness or brainstem dysfunction usually need tube feeding for a certain period of time. Medical complications, such as fever, infections, hyperglycemia, cardiac disorders, pressure sores, and deep venous thrombosis, are associated with a poor prognosis and should be treated as early as possible. Measures to prevent these complications are part of general care. Hypertension is very common during the week after stroke and should be treated only in case of extremely high values or malignant hypertension. A multidisciplinary approach in the stroke unit is necessary to prevent and manage complications in the acute phase of stroke.

Preventive antibacterial treatment improves the general medical and neurological outcome in a mouse model of stroke

BACKGROUND AND PURPOSE

Epidemiological studies have demonstrated a high incidence of infections after severe stroke and their prominent role in morbidity and mortality in stroke patients. In a mouse model, it has been shown recently that stroke is coupled with severe and long-lasting immunosuppression, which is responsible for the development of spontaneous systemic infections. Here, we investigated in the same model the effects of preventive antibiotic treatment on survival and functional outcome of experimental stroke.

METHODS

Mice were subjected to experimental stroke by occlusion of the middle cerebral artery (MCAO) for 60 minutes. A group of mice received moxifloxacin (6x100 mg/kg body weight every 2 hours over 12 hours) either immediately or 12 hours after MCAO. Control animals received the vector only. Behavior, neurological deficit, fever, survival, and body weight were monitored over 14 days. In a subgroup, infarct volume was measured 4 days after MCAO. Microbiological assessment was based on cultures of lung tissue, blood, and feces of animals 3 days after stroke. For a dose-response study, moxifloxacin was given immediately after MCAO in different doses and at different time points.

RESULTS

Microbiological analyses of blood and lung tissue demonstrated high bacterial burden, mainly Escherichia coli, 3 days after stroke. Accordingly, we observed clinical and histological signs of septicemia and pneumonia. Moxifloxacin prevented the development of infections and fever, significantly reduced mortality, and improved neurological outcome.

CONCLUSIONS

Preventive antibiotic treatment may be an important new therapeutical approach to improve outcome in patients with severe stroke.

Stroke-induced immunodeficiency promotes spontaneous bacterial infections and is mediated by sympathetic activation reversal by poststroke T helper cell type 1-like immunostimulation

Infections are a leading cause of death in stroke patients. In a mouse model of focal cerebral ischemia, we tested the hypothesis that a stroke-induced immunodeficiency increases the susceptibility to bacterial infections. 3 d after ischemia, all animals developed spontaneous septicemia and pneumonia. Stroke induced an extensive apoptotic loss of lymphocytes and a shift from T helper cell (Th)1 to Th2 cytokine production. Adoptive transfer of T and natural killer cells from wild-type mice, but not from interferon (IFN)-gamma-deficient mice, or administration of IFN-gamma at day 1 after stroke greatly decreased the bacterial burden. Importantly, the defective IFN-gamma response and the occurrence of bacterial infections were prevented by blocking the sympathetic nervous system but not the hypothalamo-pituitary-adrenal axis. Furthermore, administration of the beta-adrenoreceptor blocker propranolol drastically reduced mortality after stroke. These data suggest that a catecholamine-mediated defect in early lymphocyte activation is the key factor in the impaired antibacterial immune response after stroke.