Search PubMed⌕ Search

Biomedical subjects

R K Narayan

Publications and source records attributed to R K Narayan.

At least 55 records · Page 3Linked to original sources
PubMed1991

The effect of glucose administration on carbohydrate metabolism after head injury.

The role of intravenous infusion of glucose in limiting ketogenesis and the effect of glucose on cerebral metabolism following severe head injury were studied in 21 comatose patients. The patients were randomly assigned to alimentation with or without glucose. Systemic protein wasting, arterial concentrations of energy substrates, and cerebral metabolism of these energy substrates were monitored for 5 days postinjury. Both groups were in negative nitrogen balance, and had wasting of systemic proteins despite substantial protein intake. Blood and cerebrospinal fluid (CSF) glucose concentrations were highest on Day 1, but remained higher than normal fasting levels on all days of study, even in the patients who received no exogenous glucose. Although there were no differences in blood or CSF glucose concentrations in the two groups of patients, the glucose group had higher plasma insulin levels, with a mean +/- standard deviation of 14.8 +/- 7.3 microU/ml compared to 10.3 +/- 4.2 microU/ml in the saline group. The blood concentrations of beta-hydroxybutyrate, acetoacetate, pyruvate, glycerol, and the free fatty acids were higher in the saline group than in the glucose group. Cerebral oxygen consumption was similar in the two groups, while the cerebral metabolism of glucose and of the ketone bodies was dependent on whether glucose was administered. In the glucose group, glucose was the only energy substrate utilized by the brain. In the saline group, the ketone bodies beta-hydroxybutyrate and acetoacetate replaced glucose to the extent of 16% of the brain's total energy production. Cerebral lactate production and CSF lactate concentration were lower in the saline group. These studies suggest that administration of glucose during the early recovery period of severe head injury is a major cause of suppressed ketogenesis, and may increase production of lactic acid by the traumatized brain by limiting the availability of nonglycolytic energy substrates.

3-Hydroxybutyric Acid↗
PubMed1991

The influence of diabetes mellitus on outcome from subarachnoid hemorrhage.

Diabetes mellitus (DM) has been shown to be a risk factor for subarachnoid hemorrhage (SAH). However, the influence of this disease on outcome from SAH has not been adequately studied. We retrospectively reviewed 150 patients with SAH, including 22 with and 128 without DM. Our results indicate that pre-existing DM does not significantly influence outcome from SAH when examined in conjunction with other chronic diseases and epidemiological factors.

Adult↗
PubMed1991

Management of head injury. Intracranial pressure monitoring.

The role of intracranial pressure monitoring as an adjunct to the clinical examination, CT scanning, and other diagnostic modalities has become increasingly recognized. This article presents a brief overview of the present status of this technique and touches on prospects for further developments.

Brain Injuries↗
PubMed1990

Elevation of tumor necrosis factor in head injury.

Tumor necrosis factor (TNF) is a cytokine which mediates protein wasting in pathological states by promoting the catabolism of visceral tissues and skeletal muscle. The role that TNF plays in nitrogen wasting following head injury was studied by measuring TNF in the serum of 21 patients with severe head injury. Parallel measurements of TNF and urinary nitrogen excretion were performed on days 1, 3, and 5 after head injury. TNF values after head injury ranged from 65 pg/ml to 7500 pg/ml, with a mean of 1147 pg/ml, compared to control values of serum TNF of less than 38 pg/ml. The mean daily urinary nitrogen loss was 13 g/day with a range of 2.8 to 27.6 g/day, and the mean nitrogen balance was -5.8 g with a range of +4.6 to -19.1 g. While both serum TNF levels and nitrogen loss were increased after head injury, the elevation of TNF did not correlate strongly with nitrogen wasting.

Adult↗
PubMed1990

Intravenous cocaine abuse and subarachnoid haemorrhage: effect on outcome.

A retrospective study of subarachnoid hemorrhage associated with intravenous cocaine injection was undertaken in a large urban hospital. Patients who used intravenous cocaine had significantly poorer outcomes when compared with subarachnoid haemorrhage patients with no known exposure to the drug.

Adult↗
PubMed1990

Evaluation of a fiberoptic intracranial pressure monitor.

The fiberoptic device is a relatively new type of intracranial pressure (ICP) monitor which appears to offer certain advantages over conventional monitoring systems, particularly its ability to measure brain parenchymal pressures. This study was undertaken to analyze the accuracy and drift characteristics of the fiberoptic device and to compare pressures in the subdural, intraparenchymal, and intraventricular compartments. The device was accurate to +/- 3 mm Hg over a 0- to 30-mm Hg range in vitro. The maximum daily drift was +/- 2.5 mm Hg, with an average daily drift of +/- 0.6 mm Hg and an average drift over a 5-day period of +/- 2.1 mm Hg. In vivo, the pressures and waveform characteristics obtained with the fiberoptic device and with a strain-gauge transducer connected to a ventriculostomy were very similar. Alterations in ICP were induced by various therapeutic and pathological manipulations, and the pressures in the three intracranial compartments were compared. Changes in ICP appeared to be reflected simultaneously and equally in all three compartments. Furthermore, changes in ICP secondary to a unilateral mass lesion were identical in both supratentorial parenchymal compartments when measured simultaneously. It is concluded that the fiberoptic device is an accurate and reliable system for ICP monitoring; the pressures recorded in the subdural, intraparenchymal, and intraventricular compartments paralleled each other in all of the physiological and pathological states tested. Although the drift associated with this device is less than that reported for previously available systems, its maximal cumulative drift over a 5-day period of +/- 6 mm Hg is significant. Since the fiberoptic device cannot be recalibrated in situ, it is suggested that the device be replaced if monitoring is to be continued for periods longer than 5 days.

Animals↗
PubMed1989

Cerebral arteriovenous oxygen difference as an estimate of cerebral blood flow in comatose patients.

The hypothesis that cerebral arteriovenous difference of oxygen content (AVDO2) can be used to predict cerebral blood flow (CBF) was tested in patients who were comatose due to head injury, subarachnoid hemorrhage, or cerebrovascular disease. In 51 patients CBF was measured daily for 3 to 5 days, and in 49 patients CBF was measured every 8 hours for 5 to 10 days after injury. In the latter group of patients, when a low CBF (less than or equal to 0.2 ml/gm/min) or an increased level of cerebral lactate production (CMRL) (less than or equal to -0.06 mumol/gm/min) was encountered, therapy was instituted to increase CBF, and measurements of CBF, AVDO2, and arteriovenous difference of lactate content (AVDL) were repeated. When data from all patients were analyzed, including those with cerebral ischemia and those without, AVDO2 had only a modest correlation with CBF (r = -0.24 in 578 measurements, p less than 0.01). When patients with ischemia, indicated by an increased CMRL, were excluded from the analysis, CBF and AVDO2 had a much improved correlation (r = -0.74 in 313 measurements, p less than 0.01). Most patients with a very low CBF would have been misclassified as having a normal or increased CBF based on the AVDO2 alone. However, when measurements of AVDO2 were supplemented with AVDL, four distinct CBF patterns could be distinguished. Patients with an ischemia/infarction pattern typically had a lactate-oxygen index (LOI = -AVDL/AVDO2) of 0.08 or greater and a variable AVDO2. The three nonischemic CBF patterns had an LOI of less than 0.08, and could be classified according to the AVDO2. Patients with a normal CBF (mean 0.42 +/- 0.12 ml/gm/min) had an AVDO2 between 1.3 and 3.0 mumol/ml. A CBF pattern of hyperemia (mean 0.53 +/- 0.18 ml/gm/min) was characterized by an AVDO2 of less than 1.3 mumol/ml. A compensated hypoperfusion CBF pattern (mean 0.23 +/- 0.07 ml/gm/min) was identified by an AVDO2 of more than 3.0 mumol/min. These studies suggest that reliable estimates of CBF may be made from AVDO2 and AVDL measurements, which can be easily obtained in the intensive care unit.

Arteries↗
PubMed1989

Neurosurgical intervention in penetrating spinal trauma with associated visceral injury.

Associated injuries to the neck, chest, or abdomen are found in approximately one-quarter of all civilians with penetrating spinal cord or cauda equina injuries. While the value of and indications for general surgical exploration and repair of these injuries are fairly self-evident, the value of neurosurgical intervention in terms of neurological outcome and infection prophylaxis remains the subject of debate. To study this issue, 160 civilian patients with penetrating spinal injuries and neurological deficits were retrospectively reviewed. Associated injuries of the esophagus, trachea, bronchi, or bowel were seen in 107 individuals (67%); 33 (31%) of these patients had abdominal injuries, 25 (23%) had neck injuries, 23 (21%) had thoracic injuries, and 26 (24%) had injuries occurring at multiple sites. Of these 107 patients, 67 (63%) had complete neurological injuries and the remaining 40 (37%) demonstrated incomplete deficits. All 107 patients underwent surgical exploration and repair of their visceral injuries; in 19 of them a neurosurgical procedure was also performed for decompression of the neural elements and/or debridement of the wound. Regardless of the presence of associated visceral injuries, the mechanism of injury, and the extent of the neurological deficit, no statistically significant difference in neurological outcome was found in patients with or without neurosurgical intervention. Complications associated with neurological injury were reported in 17 (11%) of the total group of 160 patients. Four (21%) of the 19 patients who had neurosurgical intervention suffered a related complication, compared to only six (7%) of the 88 patients who were managed conservatively (p less than 0.05). Within the limitations of a retrospective review, the results of this study do not clearly support the value of routine neurosurgical intervention as an adjunct to general surgical repair in cases of spinal injury associated with penetrating visceral trauma.

Adolescent↗
PubMed1989

Clinical experience with a continuous monitor of intracranial compliance.

Intracranial compliance, as estimated from a computerized frequency analysis of the intracranial pressure (ICP) waveform, was continuously monitored during the acute postinjury phase in 55 head-injured patients. In previous studies, the high-frequency centroid (HFC), which was defined as the power-weighted average frequency within the 4- to 15-Hz band of the ICP power density spectrum, was found to inversely correlate with the pressure-volume index (PVI). An HFC of 6.5 to 7.0 Hz was normal, while an increase in the HFC to 9.0 Hz coincided with a reduction in the PVI to 13 ml and indicated exhaustion of intracranial volume-buffering capacity. The mean HFC for individual patients in the present study ranged from 6.8 to 9.0 Hz, and the length of time that the HFC was greater than 9.0 Hz ranged from 0 to 104.8 hours. The mortality rate increased concomitantly with the mean HFC, from 7% when the mean HFC was less than 7.5 Hz to 46% when the mean HFC was 8.5 Hz or greater. The length of time that the HFC was 9.0 Hz or greater was also associated with an increased mortality rate, which ranged from 16% if the HFC was never above 9.0 Hz to 60% if the HFC was 9.0 Hz or greater for more than 12 hours. In 12 patients who developed uncontrollable intracranial hypertension or clinical signs of tentorial herniation during the monitoring period, 75% were observed to have had an increase in the HFC to 9.0 Hz or more 1 to 36 hours prior to the clinical decompensation. The more rapid the increase in the HFC, the more likely the deterioration was to be caused by an intracranial hematoma. Continuous monitoring of intracranial compliance by computerized analysis of the ICP waveform may provide an earlier warning of neurological decompensation than ICP per se and, unlike PVI, does not require volumetric manipulation of intracranial volume.

Adaptation, Physiological↗
PubMed1989

Treatment of acute penetrating injuries of the spine: a retrospective analysis.

A retrospective review of 160 cases of penetrating spinal injury (PSI) was undertaken to assess the benefits and risks of operative treatment. Criteria for operation included incomplete deficits, worsening neurological status, and associated visceral perforation. Of the 160 cases, 142 had gunshot wounds (GSW) and 18 had stab wounds (SW). Laminectomy, with or without intradural exploration, was undertaken in 23% of cases. No significant differences in outcome were found between the surgical and nonsurgical groups. Meningitis, CSF leakage, and wound infections were complications that occurred more often in the surgically treated group (22%) than the conservatively managed group (7%). It has not been possible to demonstrate a benefit of surgery in PSI in this retrospective study. A prospective study is proposed that would allow better control of the variables affecting outcome.

Acute Disease↗
PubMed1988

Shotgun injuries of the spine: neurosurgical management of five cases.

The role of neurosurgical intervention in penetrating spinal injury has not been clearly established. Functional outcome has not been shown to be influenced by operation. In fact, neurosurgical intervention has been shown to potentially increase the risk of serious complications. This paper examines a unique subset of patients with penetrating spinal injury-those secondary to shotguns. An analysis of five such cases and a review of the limited literature on the subject suggests that neurosurgical intervention is of limited value in such injuries and that initial management should focus primarily upon non-neurological injuries.

Adult↗
PubMed1988

Immunological and biochemical strategies for the identification of brain tumor-associated antigens.

Various strategies have been used to identify and characterize the antigens associated with human brain tumors. These approaches have included the raising of polyclonal and monoclonal antibodies against tumor antigens and, more recently, efforts toward the direct biochemical identification of such proteins. This review summarizes the progress made in this area, suggests reasons for the broad antigenic cross-reactivity and heterogeneity revealed by these studies, and proposes additional methods for deciphering the complex antigenic composition of human brain tumors.

Antibodies, Monoclonal↗
PubMed1988

Enhanced specificity of prognosis in severe head injury.

Data from 523 patients admitted to the Medical College of Virginia with severe head injury and known 6-month outcomes were analyzed in order to determine the optimal combination of early-available prognostic factors. Twenty-one prognostic indicators noted in the emergency room at admission were used to predict outcomes into four categories: good, moderately disabled, severely disabled, or vegetative/dead. A combination of the patient's age (in years), the best motor response (graded in the usual six-point scale), and pupillary response (in both eyes) was found to be the most accurate indicator. The model correctly predicted outcome into one of the four outcome categories in 78% of cases ("specifically accurate predictions"). If predictions into an outcome category adjacent to the actual outcome were accepted, this model was accurate in 90% of cases ("grossly accurate predictions"). A set of three simple graphs based on this model can be used for rapid early estimation of probable outcome in a severely head-injured patient at admission.

Adult↗
PubMed1987

The predictive value of cerebral anaerobic metabolism with cerebral infarction after head injury.

Cerebral ischemia is a common mechanism of secondary brain injury following severe head injury. The cerebral metabolic rate of oxygen (CMRO2) and of lactate (CMRL), as well as cerebral blood flow (CBF) were measured daily for 5 days after head injury in 44 comatose head-injured patients to determine if metabolic changes could identify the patients who would develop cerebral infarction. Of 41 patients whose CBF remained at levels regarded as adequate to prevent infarction (CBF greater than or equal to 0.2 ml/gm/min), the six who showed a cerebral infarction on computerized tomography (CT) scans exhibited characteristic cerebral metabolic patterns: a CMRO2 of less than 0.6 mumol/gm/min on one or more of the days monitored, and markedly elevated cerebral lactate production (CMRL less than -0.06 mumol/gm/min) on Days 1 and/or 2 after injury. Patients who had no areas of infarction on serial CT scans typically had a CMRO2 and CMRL can be obtained at the bedside and can indicate the presence of an evolving ischemic infarct after head injury.

Adult↗
PubMed1986

Protein patterns in various malignant human brain tumors by two-dimensional gel electrophoresis.

Two-dimensional gel electrophoresis with silver staining was used to study protein patterns in various malignant human brain tumors obtained at surgery. These samples included 20 high-grade astrocytomas (anaplastic astrocytomas and glioblastomas), one low-grade astrocytoma, six juvenile astrocytomas, four ependymomas, and five medulloblastomas. Histological correlates of the sampled tissue were carefully established prior to micropunch sampling. The molecular weight range of these gels was 14,000 to 100,000, and the isoelectric points ranged from 4.7 to 7.0. Proteins that have been identified include albumin, actin, tubulin, glial fibrillary acidic protein, vimentin, glutamic oxaloacetic transaminase, neuron-specific enolase, and the beta-subunit of the guanine nucleotide regulatory proteins. Each type of tumor was found to have a characteristic protein profile that set it apart from the other tumors studied. By providing a convenient tool for the display of a wide spectrum of tumor markers in a single study, two-dimensional gel electrophoresis protein profiles may be useful as diagnostic and prognostic adjuncts. Furthermore, several protein spots that were not noted in normal human cortex were identified in the various tumor gels. Antibodies can be raised against some of these tumor-associated proteins, and their further characterization could provide valuable insights into the biology of these tumors.

Astrocytoma↗
PubMed1985

Intracranial and otological presentation of acute lymphocytic leukemia.

The authors report a patient with acute lymphocytic leukemia in hematological remission who presented with both intracranial and otological manifestations of the disease. The patient presented with clinical symptoms and computed tomographic findings consistent with otomastoiditis and a contiguous brain abscess. However, both lesions were identified at operation as leukemic infiltrates. Intracranial mass lesions and otological complications associated with leukemia are reviewed.

Adolescent↗