Regional cerebral blood flow, cerebral metabolic rate of oxygen, and cerebrospinal fluid acid-base variables in patients with acute meningitis and with acute encephalitis

Parainfectious cerebral vasculopathy complicating bacterial meningitis: Acute-short lived vasospasm followed by delayed-long lasting vasculitis

Bacterial meningitis is a serious, life-threatening infection of the meninges. Several radiological studies highlight prominent structural alterations occurring in the cerebral vasculature, leading to significant cerebrovascular consequences during bacterial meningitis. Beginning with reflexive arterial vasospasm , cerebrovascular disease during bacterial meningitis proceeds through a orderly sequence of arterial vasculitis with inflammatory cell infiltration, medial smooth muscle migration and proliferation, medial necrosis, adventitial fibrosis and eventual intimal stenosis. As such, this review focuses on changes occurring within cerebral arteries during disease progression, highlighting the various structural modifications occurring in the arterial vessels that contribute to disturbances in cerebral hemodynamics and, ultimately, cerebrovascular consequences during bacterial meningitis.

Metabolic Shifts as the Hallmark of Most Common Diseases: The Quest for the Underlying Unity

A hyper-specialization characterizes modern medicine with the consequence of classifying the various diseases of the body into unrelated categories. Such a broad diversification of medicine goes in the opposite direction of physics, which eagerly looks for unification. We argue that unification should also apply to medicine. In accordance with the second principle of thermodynamics, the cell must release its entropy either in the form of heat (catabolism) or biomass (anabolism). There is a decreased flow of entropy outside the body due to an age-related reduction in mitochondrial entropy yield resulting in increased release of entropy in the form of biomass. This shift toward anabolism has been known in oncology as Warburg-effect. The shift toward anabolism has been reported in most diseases. This quest for a single framework is reinforced by the fact that inflammation (also called the immune response) is involved in nearly every disease. This strongly suggests that despite their apparent disparity, there is an underlying unity in the diseases. This also offers guidelines for the repurposing of old drugs.

Myogenic and metabolic feedback in cerebral autoregulation: Putative involvement of arachidonic acid-dependent pathways

The present paper presents a mechanistic model of cerebral autoregulation, in which the dual effects of the arachidonic acid metabolites 20-hydroxyeicosatetraenoic acid (20-HETE) and epoxyeicosatrienoic acids (EETs) on vascular smooth muscle mediate the cerebrovascular adjustments to a change in cerebral perfusion pressure (CPP). 20-HETE signalling in vascular smooth muscle mediates myogenic feedback to changes in vessel wall stretch, which may be modulated by metabolic feedback through EETs released from astrocytes and endothelial cells in response to changes in brain tissue oxygen tension. The metabolic feedback pathway is much faster than 20-HETE-dependent myogenic feedback, and the former thus initiates the cerebral autoregulatory response, while myogenic feedback comprises a relatively slower mechanism that functions to set the basal cerebrovascular tone. Therefore, assessments of dynamic cerebral autoregulation, which may provide information on the response time of the cerebrovasculature, may specifically be used to yield information on metabolic feedback mechanisms, while data based on assessments of static cerebral autoregulation represent the integrated functionality of myogenic and metabolic feedback.

Meningococcal meningitis

OPINION STATEMENT

Meningococcal meningitis (MM) is the most common presentation of meningococcal disease and an important cause of morbidity and mortality worldwide. When MM is associated with shock, early recognition and treatment of shock is essential. No investigation should delay starting antibiotics once the diagnosis is suspected. Corticosteroids can be started at the same time as the antibiotics or just before, but this is not a specific recommendation for MM. Low-dose steroids should be used in meningococcal disease with refractory shock. Altered blood flow, cerebral edema, and raised intracranial pressure are problems that should be considered in all patients with MM and decreased consciousness level. When mechanical ventilation is required, the target carbon dioxide level is 4.0 to 4.5 kPa, with avoidance of hypocapnia. Seizures, although not frequent, can occur in MM and require prompt treatment. Other treatments, such as mannitol and activated protein C, should be avoided. Potential new treatments requiring further investigation include neuroprotection with hypothermia or glycerol.

Cerebral blood flow autoregulation in early experimental S. pneumoniae meningitis

We studied cerebral blood flow (CBF) autoregulation and intracranial pressure (ICP) during normo- and hyperventilation in a rat model of Streptococcus pneumoniae meningitis. Meningitis was induced by intracisternal injection of S. pneumoniae. Mean arterial blood pressure (MAP), ICP, cerebral perfusion pressure (CPP, defined as MAP − ICP), and laser-Doppler CBF were measured in anesthetized infected rats ( n = 30) and saline-inoculated controls ( n = 30). CPP was either incrementally reduced by controlled hemorrhage or increased by intravenous norepinephrine infusion. Twelve hours postinoculation, rats were studied solely during normocapnia, whereas rats studied after 24 h were exposed to either normocapnia or to acute hypocapnia. In infected rats compared with control rats, ICP was unchanged at 12 h but increased at 24 h postinoculation (not significant and P < 0.01, respectively); hypocapnia did not lower ICP compared with normocapnia. Twelve hours postinoculation, CBF autoregulation was lost in all infected rats but preserved in all control rats ( P < 0.01). Twenty-four hours after inoculation, 10% of infected rats had preserved CBF autoregulation during normocapnia compared with 80% of control rats ( P < 0.01). In contrast, 60% of the infected rats and 100% of the control rats showed an intact CBF autoregulation during hypocapnia ( P < 0.05 for the comparison of infected rats at normocapnia vs. hypocapnia). In conclusion, CBF autoregulation is lost both at 12 and at 24 h after intracisternal inoculation of S. pneumoniae in rats. Impairment of CBF autoregulation precedes the increase in ICP, and acute hypocapnia may restore autoregulation without changing the ICP.

Intensive care needs of children with acute bacterial meningitis: a developing country perspective

In view of very limited availability of paediatric intensive care (PIC) facilities in developing countries, it is important to define priorities and recognise children who might benefit most from PIC. The objective of this retrospective, descriptive analysis was to identify the clinical indicators for intensive care in children with acute bacterial meningitis (ABM). The study included 220 children aged between 1 month and 12 years with ABM admitted to the paediatric services of an urban, tertiary-care, teaching hospital in northern India from July 1993 to December 1996. Of these, 88 were transferred to the PICU by the primary physician, 59% were comatose (Glasgow coma score <8), 44% had raised intracranial pressure (ICP), 24% were in shock and 42% had respiratory distress/failure. Seizures occurred during their illness in 64 children, 34 of whom had refractory status epilepticus. Endotracheal intubation was needed in 29 and ventilatory support in 19 children. Most of the life support measures were required during the initial 48 hours. Nineteen (22%) children died, 16 of whom were comatose on admission. Multiple system involvement was associated with higher mortality. There were no deaths among the children who were not transferred to the PICU. Children with ABM who have a Glasgow coma score <8, clinical signs of raised ICP, refractory status epilepticus, shock and/or respiratory compromise should be prioritised to receive PIC.

Cerebral blood flow and metabolism during infusion of norepinephrine and propofol in patients with bacterial meningitis

BACKGROUND AND PURPOSE

In patients with severe bacterial meningitis, norepinephrine is often infused to increase mean arterial pressure (MAP). This increases cerebral blood flow (CBF), but it is unknown if this increase is caused by impaired cerebral autoregulation or by a cerebral effect of norepinephrine through increased cerebral metabolism. The latter possibility implies a CBF-metabolism coupling. This has not been studied during meningitis. We studied the effect of norepinephrine and propofol on CBF and oxidative metabolism in patients with severe bacterial meningitis.

METHODS

In seven patients with pneumococcal meningitis and 7 healthy subjects, norepinephrine was infused intravenously; patients also underwent intravenous propofol infusion. Global CBF was measured by the Kety-Schmidt technique; cerebral oxidative metabolism and net flux of norepinephrine and epinephrine were calculated from measured arterial-to-jugular venous concentration differences (a-vD).

RESULTS

During norepinephrine infusion, MAP increased from a median value of 79 (range, 70 to 89) to 99 (98 to 129) mm Hg in patients, and from 87 (72 to 103) to 123 (112 to 132) mm Hg in controls. CBF increased in patients (51 [48 to 60] to 59 [54 to 77] mL/100 g per minute) but remained unchanged in controls. The cerebral metabolic rate of oxygen (CMRO2) decreased in patients and remained unchanged in controls. No cerebral net flux of norepinephrine or epinephrine was found at any time in the 2 groups. During propofol infusion, CMRO2, and the a-vDO2 decreased whereas CBF was unchanged.

CONCLUSIONS

In patients with severe bacterial meningitis, norepinephrine increases both MAP and CBF but not CMRO2, indicating impaired autoregulation. Propofol reduces CBF relatively less than cerebral metabolism, suggesting a resetting of the CBF-CMRO(2) relationship.

Reducing intracranial pressure may increase survival among patients with bacterial meningitis

We reported findings concerning continuous intracranial pressure (ICP) and cerebral perfusion pressure (CPP) measurements and mortality in patients with severe bacterial meningitis treated on the basis of an ICP-targeted approach. Eighteen patients with severe bacterial meningitis were admitted for neurointensive care at Umeå University Hospital (Umeå, Sweden). In 15 patients, ICP was measured continuously through an ICP measuring device. During care, all patients but one developed intracranial hypertension with an ICP of >or=15 mm Hg (14 [93%] of 15 patients). Ten (67%) of 15 patients survived and were discharged, and 5 patients (33%) died. Mean ICP was significantly higher and CPP was markedly decreased in nonsurvivors, compared with survivors. Among the survivors, ICP was gradually reduced. Treatment of patients with severe bacterial meningitis should include neurointensive care and continuous ICP measurement. Increased ICP may be reduced by using the ICP-targeted therapy that closely resembles the "Lund concept."

Cranial Doppler ultrasonography as a predictor of neurologic sequelae in infants with bacterial meningitis

OBJECTIVE

To perform transcranial Doppler sonography in newborns and infants with bacterial meningitis to evaluate predictive value of neurologic sequelae.

MATERIALS AND METHODS

Thirty-three patients (15 newborn, 18 infant patients) with bacterial meningitis underwent cranial Doppler ultrasonography during acute phase and 3rd and 6th months after disease. Patients were examined regularly for neurologic outcome with electroencephalography and magnetic resonance imaging. The age-matched control group consisted of 20 healthy children underwent cranial Doppler sonography only.

RESULTS

To compare with the healthy controls, the mean blood flow velocity was significantly increased (P < 0.001), and pulsatility index was higher than those control group (P < 0.05) during acute bacterial meningitis. None of the patients were diagnosed with stenosis of cerebral artery. According to neurologic outcome, 14 of 33 patients had neurologic sequelae. The mean cerebral blood flow was significantly higher (P < 0.01) in patients without neurologic sequelae; pulsatility index was significantly higher (P < 0.05) in patients with neurologic sequelae when compared with the healthy controls. There was no significant difference between mean cerebral blood flow velocities and mean pulsatility index values of newborn and infant patients, regarding to neurologic outcome (P < 0.05).

CONCLUSION

Cranial Doppler ultrasonography is useful for prediction of neurologic sequelae in infants with bacterial meningitis.

Bacterial meningitis in children: critical care needs

Acute bacterial meningitis (ABM) in children is associated with a high rate of acute complications and mortality, particularly in the developing countries. Most of the deaths occur during first 48 hours of hospitalization. Coma, raised intracranial pressure (ICP), seizures, shock have been identified as significant predictors of death and morbidity. This article reviews issues in critical care with reference to our experience of managing 88 children with ABM in PICU. Attention should first be directed toward basic ABCs of life-support. Children with Glasgow Coma Scale (GSC) score < 8 need intubation and supplemental oxygen. Antibiotics should be started, even without LP (contraindicated if focal neuro-deficit, papilledema, or signs of raised ICP). Raised ICP is present in most of patients; GCS < 8 and high blood pressure are good guides. Mannitol (0.25 gm/Kg) should be used in such patients. If there are signs of (impending) herniation short-term hyperventilation is recommended; prolonged hyperventilation (> 1 hour) must be avoided. Any evidence of poor perfusion, hypovolemia and/or hypotension needs aggressive treatment with normal saline boluses and inotropes, if necessary, to maintain normal blood pressure. Empiric fluid restriction is not justified. Seizures may be controlled with intravenous diazepam or lorazepam. Refractory status epilepticus may be treated with continuous diazepam (0.01-0.06) mg/kg/min) or midazolam infusion. Ventilatory support may be needed early for associated pneumonia, poor respiratory effort and/or coma, and occasionally to reduce work of breathing in shock. Provision of critical care to children with ABM may reduce the mortality significantly as experienced by us.

Neonatal bacterial meningitis

Despite major improvements in infant intensive care, neonatal meningitis remains a devastating disease. Survivors of bacterial meningitis are at high-risk for life-long neurological handicaps, and despite a reduction in mortality, the morbidity of neonatal meningitis has not changed substantially over the last thirty years. A substantial improvement in outcome is unlikely to result from further refinements in ICU technology or new antibiotics. However, recent advancements in our understanding of the pathogenesis of meningitis and the pathophysiology of brain injury in meningitis may provide the opportunity to interrupt the mechanisms that allow bacteria to enter the central nervous system and initiate the inflammatory response. Strategies aimed at modulating the inflammatory response must be chosen carefully, so as not to disrupt normal host responses needed for the infant to recover from the infectious episode.

Regional cerebral blood flow during hyperventilation in patients with acute bacterial meningitis

Mechanical hyperventilation is often instituted in patients with acute bacterial meningitis when increased intracranial pressure is suspected. However, the effect on regional cerebral blood flow (CBF) is unknown. In this study, we measured regional CBF (rCBF) in patients with acute bacterial meningitis before and during short-term hyperventilation. In 17 patients with acute bacterial meningitis, absolute rCBF (in ml/100 g min-1) was measured during baseline ventilation and hyperventilation by single-photon emission computed tomography (SPECT) using intravenous 133Xe bolus injection. Intravenous 99mTc-HMPAO (hexamethylpropyleneamine oxime) was subsequently given during hyperventilation. In 12 healthy volunteers, rCBF was measured by SPECT and 99mTc-HMPAO during spontaneous ventilation. Using standard templates to identify regions of interest (ROIs), we calculated rCBF in percentage of cerebellar (99mTc-HMPAO images) or mean hemispheric (133Xe images) flow for each ROI, the degree of side-to-side asymmetry for each ROI, and the anterior-to-posterior flow ratio. On 133Xe images, absolute rCBF decreased significantly during hyperventilation compared to baseline ventilation in all regions, but the relative rCBF did not change significantly from baseline ventilation (n=14) to hyperventilation (n=12), indicating that the perfusion distribution was unchanged. On 99mTc-HMPAO images (n=12), relative rCBF and the anterior-to-posterior flow ratio were significantly lower in patients than in controls in the frontal and parietal cortex as well as in the basal ganglia. Focal perfusion abnormalities were present in 10 of 12 patients. Regional cerebral blood flow abnormalities are frequent in patients with acute bacterial meningitis. Short-term hyperventilation does not enhance these abnormalities.

Effect of short-term hyperventilation on cerebral blood flow autoregulation in patients with acute bacterial meningitis

BACKGROUND AND PURPOSE

Cerebral blood flow (CBF) autoregulation is impaired in patients with acute bacterial meningitis: this may be caused by cerebral arteriolar dilatation. We tested the hypothesis that CBF autoregulation is recovered by acute mechanical hyperventilation in 9 adult patients with acute bacterial meningitis.

METHODS

Norepinephrine was infused to increase mean arterial pressure (MAP) 30 mm Hg from baseline. Relative changes in CBF were concomitantly recorded by transcranial Doppler ultrasonography of the middle cerebral artery, measuring mean flow velocity (V(mean)), and by measurement of arterial to jugular oxygen content difference (a-v DO(2)). The slope of the regression line between MAP and V(mean) was calculated. Measurements were performed during normoventilation and repeated after 30 minutes of mechanical hyperventilation.

RESULTS

At normoventilation (median PaCO(2) 4.4 kPa, range 3.5 to 4.9), MAP was increased from 68 mm Hg (60 to 101) to 109 mm Hg (95 to 126). V(mean) increased with MAP from 48 cm/s (30 to 61) to 65 cm/s(33 to 86) (P<0.01), and a-v DO(2) decreased from 2.2 mmol/L (1.0 to 2.7) to 1.4 mmol/L (0.8 to 1.8) (P<0.05). During hyperventilation (PaCO(2) 3.5 kPa, range 3.3 to 4.1), MAP was increased from 76 mm Hg (58 to 92) to 109 mm Hg (95 to 121). V(mean) increased from 45 cm/s (29 to 55) to 53 cm/s (33 to 78) (P<0.01), and a-v DO(2) decreased from 2.5 mmol/L (1.8 to 3.0) to 1.8 mmol/L (1.2 to 2.4) (P<0.05). Four patients recovered autoregulation completely during hyperventilation. The slope of the autoregulation curve decreased during hyperventilation compared with normoventilation (P<0.05).

CONCLUSIONS

CBF autoregulation is partially recovered during short-term mechanical hyperventilation in patients with acute bacterial meningitis, indicating that cerebral arteriolar dilation in part accounts for the regulatory impairment of CBF in these patients.

Dependency of cerebral blood flow on mean arterial pressure in patients with acute bacterial meningitis

OBJECTIVE

Patients with acute bacterial meningitis are often treated with sympathomimetics to maintain an adequate mean arterial pressure (MAP). We studied the influence of such therapy on cerebral blood flow (CBF).

DESIGN

Prospective physiologic trial.

SETTING

The Department of Infectious Diseases, Copenhagen University Hospital, Denmark.

PATIENTS

Sixteen adult patients with acute bacterial meningitis.

INTERVENTION

Infusion of norepinephrine to increase MAP.

MEASUREMENTS

During a rise in MAP induced by norepinephrine infusion, we measured relative changes in CBF by transcranial Doppler ultrasonography of the middle cerebral artery, recording mean flow velocity (Vmean), and by the arterial to jugular oxygen saturation difference. In 10 out of 16 patients, serial measurements were performed until recovery or death. Individual autoregulation curves were analyzed by a computer program. Autoregulation was classified as impaired if Vmean increased by >10% per 30 mm Hg increase in MAP and if no lower limit of autoregulation was identified by the computer program; otherwise, autoregulation was classified as preserved.

MAIN RESULTS

Initially, Vmean increased from a median value of 46 cm/sec (range, 30-87 cm/sec) to 63 cm/sec (33-105 cm/sec) (p < .0001), and arterial to jugular oxygen saturation difference decreased from 0.28 (0.16-0.51) to 0.21 (0.08-0.39) (p < .001) when MAP was raised from 69 mm Hg (55-102 mm Hg) to 110 mm Hg (93-129 mm Hg). CBF autoregulation was restored in eight of ten patients undergoing serial examination after 7 (range, 2-10) days. Six of these patients had an uncomplicated course, one had a protracted recovery, and one died. Autoregulation was not restored in two patients; one died and one had a protracted recovery.

CONCLUSION

In patients in the early phase of acute bacterial meningitis, CBF autoregulation is impaired. With recovery from meningitis, the cerebral vasculature regains the ability to maintain cerebral perfusion at a constant level despite variations in MAP.

Nitric oxide, prostaglandins, and impaired cerebral blood flow autoregulation in group B streptococcal neonatal meningitis

Impaired autoregulation of cerebral blood flow (CBF) contributes to CNS damage during neonatal meningitis. We tested (i) the hypothesis that cerebrovascular autoregulation is impaired during early onset group B streptococcal (GBS) meningitis, (ii) whether this impairment is regulated by vasoactive mediators such as prostaglandins and (or) nitric oxide (NO), and (iii) whether this impairment is preventable by specific and (or) nonspecific inhibitors: dexamethasone, ibuprofen, and Nω-nitro-L-arginine, a NO inhibitor. Sterile saline or 109colony-forming units (cfu) of heat-killed GBS was injected into the cerebral ventricle of newborn piglets. CBF autoregulation was determined by altering cerebral perfusion pressure (CPP) with balloon-tipped catheters placed in the aorta. GBS produced a narrow range of CBF autoregulation due to an impairment at the upper limit of CPP. We report that in vivo in the early stages (first 2 h) of induced GBS inflammation (i) GBS impairs the upper limit of cerebrovascular autoregulation; (ii) ibuprofen, dexamethasone, and Nω-nitro-L-arginine not only prevent this GBS-induced autoregulatory impairment but improve the range of cerebrovascular autoregulation; (iii) these autoregulatory changes do not involve circulating cerebral prostanoids; and (iv) the observed changes correlate with the induction of NO synthase gene expression. Thus, acute early onset GBS-induced impairment of the upper limit of CBF autoregulation can be correlated with increases of NO synthase production, suggesting that NO is a vasoactive mediator of CBF.Key words: cerebrovascular autoregulation, group B Streptococcus, neonatal meningitis, anti-inflammatory agents, prostanoids, nitric oxide synthase, gene expression, nitric oxide.

Protective effect of the antioxidant N-acetyl-L-cysteine in pneumococcal meningitis in the rat

We investigated whether the antioxidant N-acetyl-L-cysteine or S-methylisothiourea, an inhibitor of the inducible nitric oxide (NO) synthase, can modulate pathophysiological alterations in an advanced phase of experimental pneumococcal meningitis in the rat. N-acetyl-L-cysteine significantly attenuated the increase in brain water content, intracranial pressure and cerebrospinal fluid white blood cell count 24 h after infection as compared to untreated, infected rats. However, it had no effect on meningitis-associated disturbances in cerebrovascular autoregulation and CO2 reactivity of cerebral vessels. Treatment with S-methylisothiourea had no effect on the pathophysiological parameters measured in this model. These data suggest that reactive oxygen species, but not NO generated by the inducible NO synthase pathway, are key mediators of changes in brain water content, intracranial pressure and meningeal inflammation in an advanced stage of pneumococcal meningitis in the rat.

Transcranial Doppler sonography at the early stage of acute central nervous system infections in adults

Transcranial Doppler sonography (TCD) of the middle, anterior and posterior cerebral arteries and of the basilar artery was used to evaluate the mean blood velocity (V mean) and the pulsatility index [PI = (V systolic-V diastolic)/V mean] as a vascular resistance index in 63 patients (male 40, female 23, mean age 43 +/- 19 y) with bacterial meningitis (n = 33, including 2 patients with fungal meningitis) and viral meningitis (n = 30) within 12 h after admission of the patients. The findings were similar for all intracranial arteries. Compared with reference values of 69 healthy volunteers [V mean of middle cerebral artery [MCA] 57 +/- 13 cm/s, MCA-PI 0.83 +/- 0.15], MCA-V mean was increased in patients with Glasgow coma scale (GCS) scores of 14 and 15 (71 +/- 18 cm/s; t-test: p < 0.001), not significantly different in the patients with GCS scores of 10-13 (55 +/- 21 cm/s) and decreased in those with GCS scores of 3-9 (42 +/- 21 cm/s, p < 0.01). The MCA-PI increased from 0.93 +/- 0.22 in the patients with GCS scores of 14-15 to 2.81 +/- 2.06 in those with GCS scores of 3-9 (p < 0.001 vs. controls). By regression analysis, MCA-V mean decreased and MCA-PI increased with decreasing GCS scores (p < 0.001). Only in patients with bacterial meningitis was the Glasgow outcome scale (GOS) score lower the more the MCA-PI was increased (regression analysis p < 0.001). We conclude that in patients with bacterial and viral meningitis, and in a good clinical state, the cerebral blood flow seems increased by hyperemia; with clinical deterioration the cerebral haemodynamics worsen. However, the early assessment of the cerebral blood flow by TCD seems useful for predicting outcome in bacterial meningitis only.

Clinical relevance and frequency of transient stenoses of the middle and anterior cerebral arteries in bacterial meningitis

BACKGROUND AND PURPOSE

We sought to examine the frequency and clinical relevance of intracranial artery stenoses in patients with bacterial meningitis in whom the occurrence of stroke has angiographically been reported to be associated with stenoses or occlusions of the large basal cerebral arteries.

METHODS

Thirty-five unselected patients (24 men, 11 women; mean age, 51 +/- 18 years) with bacterial (n = 33) or fungal (n = 2) meningitis prospectively underwent serial transcranial Doppler sonography recordings of mean blood velocity (MBV) and pulsatility index in the middle (MCA) and anterior (ACA) cerebral arteries, as well as recordings of the ratio of the MBV of the MCA and internal carotid artery (MCA/ICA ratio) on days 1, 3, 5, 8, 14, and 21 after admission. The results were correlated with the Glasgow Coma Scale (days 1 to 14), the occurrence of focal cerebral signs, and the Glasgow Outcome Scale (short-term outcome, day 21). An MCA stenosis was diagnosed by an MBV of 120 cm/s or more or an MCA/ICA ratio of more than 3. An ACA stenosis was diagnosed by an MBV of 100 cm/s or more.

RESULTS

Transient stenoses occurred most frequently between days 3 and 5 and were detected in 18 patients (51%). Seventeen patients remained without a stenosis. Patients with stenoses showed a significantly poorer mean Glasgow Coma Scale score from day 3 (9 +/- 4) to day 14 (11 +/- 4) than patients without a stenosis (day 3: 13 +/- 4, P < .01 by t test; day 14: 14 +/- 1, P < .05). The mean Glasgow Outcome Scale score was not significantly different between both groups. The occurrence of mainly transient focal cerebral signs was significantly related to the number of narrowed vessels per patient (P < .05, chi 2 test).

CONCLUSIONS

Stenoses of the intracranial arteries occur frequently in bacterial meningitis and are associated with a complicated course of the disease.

Effect of recombinant human tumor necrosis factor-alpha on cerebral oxygen uptake, cerebrospinal fluid lactate, and cerebral blood flow in the rabbit: role of nitric oxide

Among the important pathophysiologic alterations in the brain in bacterial meningitis are abnormalities of cerebral circulation and metabolism; however, the precise mechanisms by which these disturbances occur are not completely delineated. It has been recently recognized that cytokines are produced by tissues in the central nervous system in meningitis and play a critical role in the host inflammatory response. Because these mediators are involved in circulatory and metabolic disturbances in other tissues in sepsis, we investigated the role of tumor necrosis factor-alpha in the central nervous system in a rabbit model. We found that injection of recombinant human TNF into the cisterna magna in the rabbit led to an acute reduction in cerebral oxygen uptake and a more prolonged reduction in cerebral blood flow. This was accompanied by an increase in intracranial pressure and an increase in cerebrospinal fluid lactate. Reduction in oxygen uptake and increases in intracranial pressure and CSF lactate were blocked by pretreatment with L-NAME, an inhibitor of nitric oxide synthase. Reduction in cerebral blood flow was not affected by L-NAME treatment and was due to increased cerebrovascular resistance and reduced oxygen demand. These results suggest that TNF may be a critical mediator of changes in cerebral circulation and metabolism and that some of these changes occur via the nitric oxide pathway.

Effects of head elevation on intracranial hemodynamics in patients with ventriculoperitoneal shunts

The present study was performed to investigate the effects of head elevation on intracranial hemodynamics in patients with ventriculoperitoneal (VP) shunts. The series included 35 hydrocephalic patients and five individuals without hydrocephalus who were used as controls. The hydrocephalic patients were divided into three groups: 15 patients who received VP shunts with a differential-pressure valve (DP group); 11 who received VP shunts with a variable-resistance valve (VR group), and 13 hydrocephalic patients (Hyd group) who had not received shunts (four underwent VP shunts later). The cerebral blood flow (CBF) of patients in the supine and upright positions was measured by technetium-99m hexamethylpropylenamine oxide (HMPAO) single-photon emission computerized tomography in each patient, using the subtraction technique. Cerebral perfusion pressure (CPP) was taken as the difference between the mean arterial blood pressure and ventricular fluid pressure, both referenced to the level of the foramen of Mono. The patients' heads were elevated stepwise from supine to upright. Percent changes of the mean CBF in the upright position (% delta mCBFupr) were 24.9% +/- 4.3% (mean +/- standard error of the mean) in the DP group, 6.2% +/- 2.7% in the VR group, 3.5% +/- 2.6% in the Hyd group, and 4.5% +/- 2.2% in the control group. Patients in the DP group showed a pathological increase in CPP with head elevation, whereas those in the Hyd and VR groups showed a physiological decrease in CPP. Three patients with differential-pressure valves, whose % delta mCBFupr was markedly high, developed low-intracranial pressure syndrome. In conclusion, shunted patients with a DP valve showed pathological intracranial hemodynamics in the upright position. This pathological hemodynamic stress in patients with long-standing differential-pressure valve implantation may induce pathological changes in the brain such as subependymal gliosis.

Methylprednisolone attenuates inflammation, increase of brain water content and intracranial pressure, but does not influence cerebral blood flow changes in experimental pneumococcal meningitis

We investigated the effect of methylprednisolone on pathophysiological alterations in experimental pneumococcal meningitis. Untreated rats injected with pneumococcal cell wall components after hydrolization with M1 muramidase (PCW-M) developed an increase of regional cerebral blood flow (rCBF; 165.0 +/- 12.8%, baseline 100%, mean +/- S.E.M.), brain water content (79.23 +/- 0.10%), intracranial pressure (ICP; 11.9 +/- 1.0 mmHg) and white blood cell (WBC) count in the cerebrospinal fluid (CSF) (2,709 +/- 482 cells/microliters) within 8 h after intracisternal (i.c.) challenge. Pretreatment with methylprednisolone or administration of methylprednisolone 4 h after i.c. challenge significantly attenuated the increase of brain water content (78.88 +/- 0.08% and 78.82 +/- 0.05%, resp.), ICP (7.7 +/- 1.1 mmHg and 4.9 +/- 0.8 mmHg, resp.) and CSF WBC count (1,257 +/- 168 cells/microliters and 976 +/- 105 cells/microliters, resp.). However, methylprednisolone did not inhibit the increase of rCBF (163.5 +/- 13.7% and 160.9 +/- 6.8%, resp.), whereas dexamethasone significantly attenuated microvascular changes. Hypercapnia-induced reactivity of cerebral vessels tested 8 h after i.c. injection was preserved in all groups. In conclusion, we found that methylprednisolone significantly attenuated the increase of brain water content, ICP and CSF WBC count, but had no effect on microvascular changes during the early phase of experimental pneumococcal meningitis.

Brain levels of neuropeptide Y in experimental pneumococcal meningitis

Neuropeptide Y (NPY), which is found in high concentrations in several regions of the brain including nuclei of the brain stem and in nerve fibers surrounding cerebral vessels, has been proposed to play a role in regulating cerebral blood flow (CBF) and systemic vegetative functions. Since CBF is altered during meningitis, we examined whether NPY concentrations changed in various regions of the rabbit brain in response to experimental pneumococcal meningitis. Changes were most pronounced in the medulla, where NPY concentration increased threefold after 48 h of infection. Concomitantly, there was an increase in NPY immunoreactive fibers surrounding small vessels in the dorsolateral medulla, especially in the nucleus tractus solitarius. These results suggest that NPY may play a role in inducing some of the hemodynamic changes seen during pneumococcal meningitis.

Infections of the central nervous system

Infections of the central nervous system are common, serious medical conditions. One hundred consecutive adult cases with purulent meningitis of known etiology encountered by the Medical Service at Parkland Memorial Hospital were reviewed. Streptococcus pneumoniae was the most common pathogen (56 cases), followed by Neisseria meningitidis (16 cases) and Listeria monocytogenes (seven cases). Hemophilus influenzae, Staphylococcus aureus, and streptococci each accounted for five cases. An additional 15 patients had purulent meningitis with a pathogen being isolated. Twenty five purulent meningitis cases of known etiology after trauma or neurosurgery were reviewed. Staphylococcus aureus (five cases), Staphylococcus epidermidis (four cases), and gram negative bacilli (14 cases) were the most common pathogens. Review of intracranial suppurative infections demonstrated advances in microbiology, antibiotic therapy, and imaging, leading to improvements in therapy. Subdural empyema continues to be a difficult diagnosis to make and apparently is related to the anatomic pathology of the infectious process. To illustrate salient features about granulomatous meningitis and encephalitis, cases of tuberculous meningitis, herpes simplex encephalitis, St. Louis encephalitis, and encephalitis of undetermined etiology are presented and discussed.

Intracranial pressure and cerebral perfusion pressure in experimental streptococcus pneumoniae meningitis

Clinical studies have demonstrated the prognostic importance of increased intracranial pressure in central nervous system infections. To delineate development of intracranial pressure in meningitis experiments were carried out in rabbits. Meningitis was induced by injecting streptococcus pneumoniae bacteria into the cisterna magna and blood, and intracranial pressures were continuously recorded. In the experimental model, three stages were seen: incubation period (0-8 h)--in which CSF becomes positive for the infecting organism and biochemical changes occur, but there are no hemodynamic or intracranial pressure changes; stage of slowly increasing intracranial pressure - because blood pressure remains normal, cerebral perfusion pressure is maintained adequate for cerebral metabolic need (9-24 h); terminal stage (greater than 25 h)--with hemodynamic collapse, critical reduction of cerebral perfusion pressure, cerebral ischemia, and death of the experimental animals. It is suggested that a similar sequence occurs in human disease. The clinical implication stresses the need for early recognition and treatment of intracranial hypertension as an important adjunct to antibiotic treatment of the infecting organism.

Antioxidants attenuate microvascular changes in the early phase of experimental pneumococcal meningitis in rats

BACKGROUND AND PURPOSE

We tested in a rat meningitis model 1) whether pneumococcal cell wall components are capable of producing changes in regional cerebral blood flow, brain water content, and intracranial pressure similar to those we have already observed after intracisternal inoculation of live pneumococci and 2) whether antioxidants would modulate these alterations in the early phase of meningitis.

METHODS

Regional cerebral blood flow as measured by laser Doppler flowmetry and intracranial pressure were monitored continuously for 4 hours after intracisternal challenge. Brain edema formation was assessed by brain water content determinations. We investigated the following groups: rats challenged intracisternally with the whole intact pneumococcal cell wall (n = 7) or the pneumococcal cell wall hydrolyzed by the M1-muramidase (n = 7); rats injected intracisternally with phosphate-buffered saline (n = 6); rats pretreated intravenously with superoxide dismutase conjugated with polyethylene glycol (10,000 units/kg) and injected intracisternally with cell wall components (n = 5) or phosphate-buffered saline (n = 6); rats injected intracisternally with phosphate-buffered saline and pretreated intravenously with polyethylene glycol (10% solution, 1.2 ml/kg, n = 5) or continuously treated with intravenous free superoxide dismutase (22,000 units/kg per hour, n = 6); and rats continuously treated intravenously with deferoxamine mesylate (10 mg/kg per hour) and injected intracisternally with cell wall components (n = 6) or phosphate-buffered saline (n = 7).

RESULTS

Both pneumococcal cell wall preparations produced a significant increase in regional cerebral blood flow, intracranial pressure, and brain water content. Conjugated superoxide dismutase as well as deferoxamine prevented the increase in intracranial pressure and brain water content. In addition, the increase in regional cerebral blood flow as observed in untreated, cell wall-challenged rats (baseline, 100%; 183.1 +/- 12.3% after 4 hours, mean +/- SEM) was significantly attenuated by administration of both conjugated superoxide dismutase (136.6 +/- 14.1%) and deferoxamine (149.8 +/- 8.2%) (p < 0.05). Polyethylene glycol-conjugated superoxide dismutase alone produced an increase in regional cerebral blood flow (125.6 +/- 8.7% after 4 hours). We found that polyethylene glycol per se accounts for this action.

CONCLUSIONS

These data show that pneumococcal cell wall components containing teichoic acid produce changes in regional cerebral blood flow, intracranial pressure, and brain water content and that oxygen radicals contribute to these pathophysiological alterations in the early phase of experimental pneumococcal meningitis.

Abnormalities of cerebral blood flow in the acute phase of bacterial meningitis in adults

The frequency, course and clinical significance of changes in regional cerebral blood flow (rCBF) during bacterial meningitis were investigated in 14 adult patients. The results of 99mTc-hexamethylpropylene amine oxime (HMPAO) single photon emission computed tomography (SPECT) were compared with the clinical signs and findings using cerebral angiography and conventional CT. HMPAO SPECT was performed 2-15 days (median 4.5 days) after the onset of neurological disease. Decreased HMPAO accumulation was detected in 13 patients. SPECT studies revealed focal hypoperfusion corresponding to the clinical symptoms in 6 patients suffering from hemiparesis or hemiataxia. Conventional cranial CT disclosed brain infarction in only 1 patient. Focal hypoperfusion was also found in 7 of 8 patients without clinical evidence of focal neurological deficits. In 6 patients, HMPAO SPECT findings were abnormal although cerebral angiography was normal. At follow-up examinations 3-45 weeks after the acute disease, abnormalities revealed by HMPAO SPECT had improved or had even disappeared in all patients studied. Our results indicate that reduced rCBF is a frequent finding in bacterial meningitis in the adult. In most patients it probably represents a functional and reversible disorder without structural lesion detectable on CT.

Effect of hydration status on cerebral blood flow and cerebrospinal fluid lactic acidosis in rabbits with experimental meningitis

The effects of hydration status on cerebral blood flow (CBF) and development of cerebrospinal fluid (CSF) lactic acidosis were evaluated in rabbits with experimental pneumococcal meningitis. As loss of cerebrovascular autoregulation has been previously demonstrated in this model, we reasoned that compromise of intravascular volume might severely affect cerebral perfusion. Furthermore, as acute exacerbation of the inflammatory response in the subarachnoid space has been observed after antibiotic therapy, animals were studied not only while meningitis evolved, but also 4-6 h after treatment with antibiotics to determine whether there would also be an effect on CBF. To produce different levels of hydration, animals were given either 50 ml/kg per 24 h of normal saline ("low fluid") or 150 ml/kg 24 h ("high fluid"). After 16 h of infection, rabbits that were given the lower fluid regimen had lower mean arterial blood pressure (MABP), lower CBF, and higher CSF lactate compared with animals that received the higher fluid regimen. In the first 4-6 h after antibiotic administration, low fluid rabbits had a significant decrease in MABP and CBF compared with, and a significantly greater increase in CSF lactate concentration than, high fluid rabbits. This study suggests that intravascular volume status may be a critical variable in determining CBF and therefore the degree of cerebral ischemia in meningitis.

Microvascular changes during the early phase of experimental bacterial meningitis

We investigated the temporal profile of the changes in regional CBF (rCBF) and intracranial pressure (ICP) during the early phase of pneumococcal meningitis in the rat. rCBF, as measured by laser-Doppler flowmetry, and ICP were continuously monitored during 6 h post infection (p.i.). Brain edema formation was assessed by brain water content determinations. Meningitis was induced by intracisternal injection of 75 microliters of 10(7) colony-forming units/ml pneumococci (n = 7). In control animals (n = 6), saline was injected. There was no change in the rCBF or ICP of controls throughout the experiment. However, there was a dramatic increase in rCBF and ICP associated with brain edema formation in untreated meningitis animals. rCBF increased to 135.3 +/- 33.8% (mean +/- SD) in the untreated animals at 1 h p.i. and reached 211.1 +/- 40.5% at 6 h p.i. (p less than 0.05 compared with controls). ICP increased from 2.9 +/- 1.4 to 10.4 +/- 4.7 mm Hg at 6 h p.i. (p less than 0.05 compared with controls). Brain water content was significantly elevated (79.69 +/- 0.24 compared with 78.94 +/- 0.16% in the control group, p less than 0.05). We investigated the effect of dexamethasone (3 mg/kg i.p.), which was given prior to the induction of meningitis (n = 3) or at 2 h after pneumococcal injection (n = 5), indomethacin (10 mg/kg i.v., n = 5), and superoxide dismutase (SOD; 132,000 U/kg i.v. per 6 h, n = 6).(ABSTRACT TRUNCATED AT 250 WORDS)

Cerebral blood flow and carbon dioxide reactivity in children with bacterial meningitis

We examined total and regional cerebral blood flow (CBF) by stable xenon computed tomography in 20 seriously ill children with acute bacterial meningitis to determine whether CBF was reduced and to examine the changes in CBF during hyperventilation. In 13 children, total CBF was normal (62 +/- 20 ml/min/100 gm) but marked local variability of flow was seen. In five other children, total CBF was significantly reduced (26 +/- 10 ml/min/100 gm; p less than 0.05), with flow reduced more in white matter (8 +/- 5 ml/min/100 gm) than in gray matter (30 +/- 15 ml/min/100 gm). Autoregulation of CBF appeared to be present in these 18 children within a range of mean arterial blood pressure from 56 to 102 mm Hg. In the remaining two infants, brain dead within the first 24 hours, total flow was uniformly absent, averaging 3 +/- 3 ml/min/100 gm. In seven children, CBF was determined at two carbon dioxide tension (PCO2) levels: 40 (+/- 3) mm Hg and 29 (+/- 3) mm Hg. In six children, total CBF decreased 33%, from 52 (+/- 25) to 35 (+/- 15) ml/min/100 gm; the mean percentage of change in CBF per millimeter of mercury of PCO2 was 3.0%. Regional variability of perfusion to changes in PCO2 was marked in all six children. The percentage of change in CBF per millimeter of mercury of PCO2 was similar in frontal gray matter (3.1%) but higher in white matter (4.5%). In the seventh patient a paradoxical response was observed; total and regional CBF increased 25% after hyperventilation. Our findings demonstrate that (1) CBF in children with bacterial meningitis may be substantially decreased globally, with even more variability noted regionally, (2) autoregulation of CBF is preserved, (3) CBF/CO2 responsitivity varies among patients and in different regions of the brain in the same patient, and (4) hyperventilation can reduce CBF below ischemic thresholds.

[Bacterial meningitis in infants: neurological aspects]

Clinical, neurologic and laboratory aspects of bacterial meningitis in the newborn infant are critically reviewed taking into account author's experience. Pathophysiologic data on acute phase phenomena in the CNS are analysed for this purpose.

Loss of cerebrovascular autoregulation in experimental meningitis in rabbits

The present study was designed to determine whether cerebrovascular autoregulation is intact in experimental meningitis and to examine the relationship between fluctuations in cerebral blood flow (CBF) and increased intracranial pressure (ICP). Measurements of CBF were determined by the radionuclide microsphere technique in rabbits with experimental Streptococcus pneumoniae meningitis with simultaneous ICP monitoring via an implanted epidural catheter. CBF and ICP measurements were determined at baseline and when mean arterial blood pressure (MABP) was artificially manipulated by either pharmacologic or mechanical means. CBF was pressure passive with MABP through a range of 30-120 torr, and ICP directly correlated with CBF. These findings indicate that autoregulation of the cerebral circulation is lost during bacterial meningitis, resulting in a critical dependency of cerebral perfusion on systemic blood pressure, and that the parallel changes in ICP and in CBF suggest that fluctuations in CBF may influence intracranial hypertension in this disease.

Brain edema and increased intracranial pressure in the pathophysiology of bacterial meningitis

A number of advances in our understanding of the pathophysiology of bacterial meningitis have been made in recent years. In vivo studies have shown that bacterial cell wall fragments and endotoxins are highly active components, independent of the presence of viable bacteria in the subarachnoid space. Their presence in the cerebrospinal fluid is associated with the induction of inflammation and with the development of brain edema and increased intracranial pressure. Antimicrobial therapy may cause an additional increase of harmful bacterial products in the cerebrospinal fluid and thereby potentiate these pathophysiological alterations. These changes may contribute to the development of brain damage during meningitis. Some promising experimental work has been directed toward counteracting the above phenomena with non-steroidal or steroidal anti-inflammatory agents as well as with monoclonal antibodies. Although considerable advances have been made, further research needs to be done in these areas to improve the prognosis of bacterial meningitis.

Cerebral anaerobic glycolysis and reduced cerebral oxygen transport in human cerebral malaria

In 12 patients comatose with cerebral malaria, cerebral blood flow was 52.2 (SE 4.0) ml/100 g per min, within the reported range for healthy controls, but cerebral vascular resistance was raised at 1.66 (0.19) mm Hg/ml per 100 g per min. Cerebral oxygen consumption (1.90 [0.23] ml/100 g per min), and cerebral arteriovenous oxygen content difference (3.5 [0.43] ml/dl) were subnormal, while cerebral venous pO2 (5.7 [0.2] kpA) was raised. After recovery of consciousness there were significant decreases in arterial lactate concentration (2.44 [0.45] to 1.19 [0.45] mumol/l) and cerebral lactate production (17.4 [7.9] to 5.6 [1.1] mmol/100 g per minute). These results provide evidence of cerebral anaerobic glycolysis associated with inadequate oxygen delivery to the brain consistent with either inhibition of cerebral oxidative metabolism or the microcirculatory obstruction envisaged in the "mechanical" hypothesis for cerebral malaria.

Intracranial pressure in childhood central nervous system infections

To determinate the importance of intracranial hypertension in central nervous system (CNS) acute infections, we studied intracranial pressure (ICP) in 27 patients, age 45 days to 13 years. Fourteen had meningitis and 13 had encephalitis; all were in deep coma with Glasgow Coma Scale 7 or less. Intracranial hypertension defined by a mean ICP above 15 mmHg, was observed in 12 patients with meningitis (86%) and in 9 with encephalitis (69%). Patients with meningitis exhibited a sudden and severe intracranial hypertension. A striking difference was noted between survivors and non survivors who had a very high maximal ICP with a severe reduction of cerebral perfusion pressure (CPP). Intracranial hypertension occurred in all patients with acute primary encephalitis but in only 3/7 patients with post-infectious encephalitis. ICP monitoring seems to be important in the comatose forms of: (1) bacterial meningitis in the early period (2) herpes encephalitis (3) post-infectious encephalitis with severe status epilepticus.

Update on bacterial meningitis

Recently, advances in identifying the etiologic agent, improving antibiotic therapy, and understanding the pathogenesis of complications of bacterial meningitis have been made. The acute and long-term sequelae and their courses have been documented. Acridine orange staining of the cerebrospinal fluid may identify bacteria in children with partially treated meningitis when gram-staining is not helpful. Monoclonal antibodies for meningococcus group B antigen have been developed and may prove useful for testing cerebrospinal fluid. Several newer cephalosporins have been shown to have excellent in vitro activity against the bacteria commonly associated with meningitis. They are indicated in the treatment of infants between 4 and 8 weeks of age, children in septic shock, children with liver disease, and children with infection with gram-negative enteric agents or bacteria resistant to ampicillin and chloramphenicol. Vasculitis and cerebral infarction may result in some of the complications, such as seizures and hemiparesis, noted in children, and their consequences can be documented by various neuroimaging procedures. The prognosis for ataxia is good, while that for sensorineural deafness is poor. The majority of children will have neither intellectual deficits nor difficulty with academic achievement. An effective vaccine against Haemophilus influenzae type b has been developed and is recommended for children between 18 and 60 months of age.

Experimental meningitis in the rabbit. II. Cerebral energy metabolism in relation to increased cerebrospinal fluid concentrations of lactate

We have analyzed cerebral energy metabolism in rabbits with Streptococcus pneumoniae or Escherichia coli meningitis aiming at an increased understanding of the cerebrospinal fluid (CSF) lactacidosis observed in this disease. After intracisternal inoculation of bacteria the lactate concentration in the CSF increased to 9.7 +/- 0.7 (mean +/- SE) mmol/l compared to control values of 3.2 +/- 0.2 mmol/l. Simultaneously sampled brain tissue from parietal cortex, caudate nucleus, and thalamus showed no increase in lactate concentrations. The high-energy phosphate content decreased only marginally, phosphocreatine levels by 11-17% in the cortex and in the caudate nucleus, and adenosine triphosphate concentrations by 15%, but only in the caudate nucleus. Our results indicate that the CSF lactate increase in bacterial meningitis is not primarily linked to cerebral lactacidosis. The decreased concentrations of high-energy phosphates in diseased animals need further study but may be due to increased intracranial pressure and reduced capillary blood flow.

Pneumococcal meningitis: an evaluation of prognostic factors in 164 cases based on mortality and on a study of lasting sequelae

During the period 1966-76, 164 patients with pneumococcal meningitis were admitted to the University Hospital, Copenhagen. Of 111 survivors 94 underwent a series of clinical examinations. The findings in each patient were assessed for their aetiological relationship to meningitis. Of these patients 54% had neurological sequelae, 42% had neuropsychological sequelae, 25% had otological sequelae and 16% had sequelae as judged by computer-assisted tomography of the brain. On the basis of the general clinical condition, each patient was evaluated for the presence of sequelae of meningitis by means of a rating of nil, mild, moderate or severe. These ratings and mortality rates were used to evaluate the prognostic significance of various features present during the acute illness. A fatal outcome was significantly associated with increasing age, concomitant pneumonia, altered consciousness on admission, transfer from another hospital and development of complications while in hospital. There was a statistically significant association between lasting sequelae and the female sex, the age group of 16-50 years, patients who had not received any pre-admission antibiotic therapy and those with positive bacterial cultures of specimens from sites other than blood or cerebrospinal fluid.

Clinical utility of lactic acid measurement in body fluids other than plasma

The diagnosis of septic infections of closed body cavities requires a careful search. Traditional laboratory tests such as Gram's stain, white cell count, and protein and glucose levels are often inconclusive. Measurement of lactic acid in cerebrospinal, synovial, pleural, ascitic, and bursal fluids has been utilized to distinguish bacterial from nonbacterial infections. The present review summarizes the current status of lactic acid measurement in the differential diagnosis of meningitis, arthritis, empyema, bacterial peritonitis, and bursitis.

Cerebrospinal fluid lactic acidosis in bacterial meningitis

A rapid, microenzymatic method was used to measure cerebrospinal fluid lactate levels in 205 children with suspected bacterial meningitis. Fifty children with normal CSF containing fewer than 0.005 X 10(9)/l WBC, no segmented neutrophils, glucose 3.4 +/- 0.8 mmol/l (61.2 +/- 14.4 mg/100 ml), and a protein of less than 0.30 g/l had CSF lactate levels below 2.0 mmol/l (18 mg/100 ml) (mean and standard deviation 1.3 +/- 0.3 mmol/l (11.8 +/- 2.7 mg/100 ml)). In 31 cases of proved viral meningitis as with 58 cases of clinically diagnosed viral meningitis, levels were below 3.8 mmol/l (34.5 mg/100 ml), being 2.3 +/- 0.6 mmol/l (20.9 +/- 5.4 mg/100 ml), and 2.1 +/- 0.7 mmol/l (19.1 +/- 6.4 mg/100 ml) respectively. Sixty-six cases of bacterial meningitis had CSF lactate levels ranging from 3.9 mmol/l (35.4 mg/100 ml) to greater than 10.0 mmol/l (90.0 mg/100 ml). Longitudinal studies in 7 children with bacterial meningitis showed that cerebrospinal fluid lactate levels differentiated bacterial from viral meningitis up to 4 days after starting treatment with antibiotics. Use of CSF lactate measurement for monitoring the efficacy of treatment is illustrated in a case of bacterial meningitis due to Pseudomonas aeruginosa. The origin of the cerebrospinal fluid lactate acidosis and the role of lactate in the pathophysiological cycle leading to intensification of brain tissue hypoxia and cellular damage is discussed with respect to the short-term prognosis and the long-term neurological sequelae.

Pathophysiological correlates in bacterial meningitis

This review summarises briefly several areas of importance in the pathogenesis of bacterial meningitis. These subjects include: (1) factors that predispose to the development of disease and relevant host defense mechanisms; (2) microbial virulence factors; (3) the route(s) of entry for bacteria into the cerebrospinal fluid (CSF); (4) the role of pathological changes in the central nervous system; (5) particulate clearance mechanisms operative in the CSF system; and (6) the physiological alteration in normal intracranial homeostatic processes.