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Biomedical subjects

D Hasan

Publications and source records attributed to D Hasan.

At least 19 recordsLinked to original sources
PubMed2003

Effects of cerebral air embolism on brain metabolism in pigs.

OBJECTIVES: Cerebral air embolism was induced in pigs and changes in intracranial pressure (ICP), brain oxygen (PbrO2), brain carbon dioxide (PbrCO2), brain pH (brpH) and glucose, lactate and pyruvate levels were used to characterize this model. METHODS: In seven anesthetized pigs, ICP, PbrO2, PbrCO2 and brpH were measured continuously with multiparameter sensors and brain glucose metabolism by microdialysis. After injection of air into the internal carotid artery, these parameters were recorded for 2 h. RESULTS: ICP increased (433%) from 12 +/- 1 to 52 +/- 8 mmHg (P < 0.05). PbrO2 decreased from 25.7 +/- 6.2 to 11.9 +/- 5.2 mmHg. PbrCO2 increased (109%) from 57.7 +/- 2.7 to 120.4 +/- 21.5 mmHg (P < 0.05). Brain glucose decreased (38%) from 3.05 +/- 0.91 to 1.91 +/- 0.55 mmol, while brain lactate increased (384%) from 1.36 +/- 0.15 to 5.22 +/- 0.53 mmol/l (P < 0.05). CONCLUSIONS: Cerebral air embolism has a deleterious effect on ICP and brain metabolism. Therefore, this model may be suitable for testing therapeutic regimens in cerebral air embolism.

Animals↗
PubMed2001

Cardioprotection in pigs by exogenous norepinephrine but not by cerebral ischemia-induced release of endogenous norepinephrine.

BACKGROUND AND PURPOSE: Endogenous norepinephrine release induced by cerebral ischemia may lead to small areas of necrosis in normal hearts. Conversely, norepinephrine may be one of the mediators that limit myocardial infarct size by ischemic preconditioning. Because brief ischemia in kidneys or skeletal muscle limits infarct size produced by coronary artery occlusion, we investigated whether cardiac norepinephrine release during transient cerebral ischemia also elicits remote myocardial preconditioning. METHODS: Forty-one crossbred pigs of either sex were assigned to 1 of 7 experimental groups, of which in 6 groups myocardial infarct size was determined after a 60-minute coronary occlusion and 120 minutes of reperfusion. One group served as control (no pretreatment), while the other groups were pretreated with either cerebral ischemia or an intracoronary infusion of norepinephrine. RESULTS: In 10 anesthetized control pigs, infarct size was 84+/-3% (mean+/-SEM) of the area at risk after a 60-minute coronary occlusion and 120 minutes of reperfusion. Intracoronary infusion of 0.03 nmol/kg. min(-)(1) norepinephrine for 10 minutes before coronary occlusion did not affect infarct size (80+/-3%; n=6), whereas infusion of 0.12 nmol/kg. min(-)(1) limited infarct size (65+/-2%; n=7; P:<0.05). Neither 10-minute (n=5) nor 30-minute (n=6) cerebral ischemia produced by elevation of intracranial pressure before coronary occlusion affected infarct size (83+/-4% and 82+/-3%, respectively). Myocardial interstitial norepinephrine levels tripled during cerebral ischemia and during low-dose norepinephrine but increased 10-fold during high-dose norepinephrine. Norepinephrine levels increased progressively up to 500-fold in the area at risk during the 60-minute coronary occlusion, independent of the pretreatment, while norepinephrine levels remained unchanged in adjacent nonischemic myocardium and arterial plasma. CONCLUSIONS: Cerebral ischemia preceding a coronary occlusion did not modify infarct size, which is likely related to the modest increase in myocardial norepinephrine levels during cerebral ischemia. The infarct size limitation by high-dose exogenous norepinephrine is not associated with blunting of the ischemia-induced increase in myocardial interstitial norepinephrine levels.

Animals↗
PubMed2000

Interobserver variability of cisternal blood on CT after aneurysmal subarachnoid hemorrhage.

Interobserver variability in the prediction of delayed cerebral ischemia by means of blood on CT was investigated in 159 patients with aneurysmal subarachnoid hemorrhage, admitted within 72 hours after the bleed. The authors found considerable interobserver variability in the assessment of the amount of blood in the individual cisterns. A high sum score was an independent predictor for delayed cerebral ischemia only for rater 1 (rater 1: hazard ratio, 3.26; 95% confidence interval [CI], 1.14 to 7.75; rater 2: hazard ratio, 1.72; 95% CI, 0.72 to 4.09). The authors conclude that interobserver variability limits the predictive power of the amount of blood on CT for the occurrence of cerebral ischemia.

Brain Ischemia↗
PubMed1999

Validity of prediction of the site of ruptured intracranial aneurysms with CT.

OBJECTIVE: We studied the diagnostic power of blood distribution on CT (performed within 72 hours after the bleed) for the site of ruptured aneurysm in 168 consecutive patients with subarachnoid hemorrhage with either a single aneurysm or no aneurysm on the four-vessel angiogram or postmortem examination. METHODS: A neurosurgeon and a neuroradiologist blind to the results of the angiography independently scored the distribution of blood on the CT and predicted the site of the ruptured aneurysm. RESULTS: Overall agreement among raters was 52% and chance-adjusted agreement (kappa) was 0.42 (weighted kappa value 0.47). A parenchymal cerebral hematoma was an excellent predictor for the site of a ruptured aneurysm but was present in only a minority of cases (15%). The next most valid predictor was blood distribution on CT in patients with a ruptured anterior cerebral artery aneurysm or anterior communicating artery aneurysm (sensitivity 0.79, specificity 0.96, and positive predictive value 0.79 for rater 1; sensitivity 0.77, specificity 0.97, and positive predictive value 0.90 for rater 2). The validity of the predictive value of blood distribution on CT in patients with a ruptured aneurysm of the middle cerebral artery, internal carotid artery, or posterior circulation arteries was either inconsistent between raters or low. CONCLUSION: With the exception of the presence of a parenchymal hematoma, the site of the ruptured aneurysm can be predicted by CT only in ruptured anterior cerebral artery or anterior communicating artery aneurysms.

Adult↗
PubMed1999

Compression of the visual pathway by anterior cerebral artery aneurysm.

Visual failure is an uncommon presenting symptom of an intracranial aneurysm. It is even more uncommon in aneurysms arising from the anterior cerebral artery (ACA). We presented 2 patients with an aneurysm of the A1 segment of the anterior cerebral artery causing visual field defects. One patient presented with a complete homonymous hemianopia due to compression of the optic tract by a giant aneurysm of the proximal left A1 segment. The second patient had an almost complete unilateral anopia caused by compression of the optic nerve and chiasm by an aneurysm of the distal part of the A1 segment with a small chiasmatic hemorrhage and ventricular rupture.

Adult↗
PubMed1998

Impact of medical treatment on the outcome of patients after aneurysmal subarachnoid hemorrhage.

BACKGROUND AND PURPOSE: The rationale behind early aneurysm surgery in patients with subarachnoid hemorrhage (SAH) is the prevention of rebleeding as early as possible after SAH. In addition, by clipping the aneurysm as early as possible, one can apply treatment for cerebral ischemia more vigorously (induced hypertension) without the risk of rebleeding. Hypervolemic hemodilution is now a well-accepted treatment for delayed cerebral ischemia. We compared the prospectively collected clinical data and outcome of patients admitted to the intensive care unit in the period 1977 to 1982 with those of patients admitted in the period 1989 to 1992 to measure the effect of the change in medical management procedures on patients admitted in our hospital with SAH. METHODS: We studied 348 patients admitted within 72 hours after aneurysmal SAH. Patients with negative angiography results and those in whom death appeared imminent on admission were excluded. The first group (group A) consisted of 176 consecutive patients admitted from 1977 through 1982. Maximum daily fluid intake was 1.5 to 2 L. Hyponatremia was treated with fluid restriction (<1 L/24 h). Antihypertensive treatment with diuretic agents was given if diastolic blood pressure was >110 mm Hg. Patients in the second group (172 consecutive patients; group B) were admitted from 1989 through 1992. Daily fluid intake was at least 3 L, unless cardiac failure occurred. Diuretic agents and antihypertensive medications were avoided. Cerebral ischemia was treated with vigorous plasma volume expansion under intermittent monitoring of pulmonary wedge pressure, cardiac output, and arterial blood pressure, aiming for a hematocrit of 0.29 to 0.33. Aneurysm surgery was planned for day 12. RESULTS: Patients admitted in group B had less favorable characteristics for the development of cerebral ischemia and for good outcome when compared with patients in group A. Despite this, we found a significant decrease in the frequency of delayed cerebral ischemia in patients of group B treated with tranexamic acid (P=0.00005 by log rank test) and significantly improved outcomes among patients with delayed cerebral ischemia (P=0.006 by chi2 test) and among patients with deterioration from hydrocephalus (P=0.001 by chi2 test). This resulted in a significant improvement of the overall outcome of patients in group B when compared with those in group A (P=0.006 by chi2 test). The major cause of death in group B was rebleeding (P=0.011 by chi2 test). CONCLUSIONS: We conclude that the outcome in our patients with aneurysmal SAH was improved but that rebleeding remains a major cause of death. Patient outcome can be further improved if we can increase the efficacy of preventive measures against rebleeding by performing early aneurysm surgery.

Adult↗
PubMed1996

Vascular risk factors, atherosclerosis, cerebral white matter lesions and cerebral perfusion in a population-based study.

We studied risk factors for cerebral vascular disease (blood pressure and hypertension, factor VIIc, factor VIIIc, fibrinogen), indicators of atherosclerosis (intima-media thickness and plaques in the carotid artery) and cerebral white matter lesions in relation to regional cerebral blood flow (rCBF) in 60 persons (aged 65-85 years) recruited from a population-based study. rCBF was assessed with single-photon emission tomography using technetium-99m d, l-hexamethylpropylene amine oxime (99mTc-HMPAO). Statistical analysis was performed with multiple linear regression with adjustment for age, sex and ventricle-to-brain ratio. A significant positive association was found between systolic and diastolic blood pressure and temporo-parietal rCBF. In analysis with quartiles of the distribution, we found a threshold effect for the relation of low diastolic blood pressure (</=60 mmHg) and low temporo-parietal rCBF. Levels of plasma fibrinogen were inversely related to parietal rCBF, with a threshold effect of high fibrinogen levels (>3.2 g/l) and low rCBF. Increased atherosclerosis was related to low rCBF in all cortical regions, but these associations were not significant. No consistent relation was observed between severity of cerebral white matter lesions and rCBF. Our results may have implications for blood pressure control in the elderly population.

Aged↗
PubMed1995

Detection of subarachnoid haemorrhage on early CT: is lumbar puncture still needed after a negative scan?

Computed tomography may be normal in up to 5% of patients who are investigated within one or two days after subarachnoid haemorrhage. This study investigated the need for further diagnostic evaluation after a normal CT scan was found very early (within 12 hours) in patients suspected of subarachnoid haemorrhage. A consecutive series of 175 patients with sudden headache and a normal neurological examination who had first CT within 12 hours after the onset of headache were investigated. The patients with normal CT underwent lumbar puncture, but not earlier than 12 hours after the event. Computed tomography showed subarachnoid blood in 117 patients, and was normal in 58. Spectrophotometric analysis of CSF gave evidence for a subarachnoid haemorrhage in two of these 58 patients (3%; 95% confidence interval (95% CI) 0.4-12%); a ruptured aneurysm was found in both. Thus CT was normal in two of 119 patients with a definite subarachnoid haemorrhage (2%; 95% CI 0.2-6%). It is concluded that in patients with sudden headache but normal CT a deferred lumbar puncture is necessary to rule out subarachnoid haemorrhage, even if CT is performed within 12 hours after the onset of symptoms.

Acute Disease↗
PubMed1995

Outcome in patients with large intraventricular haemorrhages: a volumetric study.

Patients with large amounts of intraventricular blood have a poor prognosis. The question is whether the quantity of ventricular blood or other factors related to the origin of the intraventricular bleeding cause poor outcome. The association between ventricular blood volume and outcome was analysed in patients with a primary intraventricular haemorrhage (PIVH) and in patients with an aneurysmal subarachnoid haemorrhage (SAH). The medical records of 24 patients with PIVH were reviewed and these patients were compared with 59 patients selected from a prospectively studied series of patients with aneurysmal SAH who had intraventricular blood without an intraparenchymal haematoma. Glasgow coma score on admission and outcome at three months expressed on the Glasgow outcome scale were available for all patients. Volumetric analysis on CT was carried out if there was at least a moderate amount of blood measured with a semi-quantitative scale (SAH n = 30, PIVH n = 22). In patients with SAH more than 20 ml intraventricular blood was lethal, as previously shown for patients with intraparenchymal haemorrhage. Patients with a PIVH can, however, survive such large volumes of intraventricular blood without impaired consciousness immediately after the bleeding, without developing hydrocephalus, and without any disability after three months. It is concluded that the cause of an intraventricular haemorrhage is more important for outcome than the amount of intraventricular blood, and large intraventricular haemorrhages are not always associated with hydrocephalus.

Adolescent↗
PubMed1994

Assessment of cerebral perfusion with single-photon emission tomography in normal subjects and in patients with Alzheimer's disease: effects of region of interest selection.

The shape, size and location of regions of interest (ROIs) show considerable variability between single-photon emission tomography (SPET) studies in aging and Alzheimer's disease, but the possible influence on study results remains unknown. We compared three different ROIs in a SPET study with 60 controls and in 48 patients with probable Alzheimer's disease diagnosed according to the NINCDS-ADRDA criteria. Regional cerebral blood flow (rCBF) was assessed with SPET using technetium-99m d,l-hexamethylpropylene amine oxime (99mTc-HMPAO), normalized to the mean activity in a cerebellar reference slice. The three different ROIs were: a multi-slice and a single-slice ROI with reference to the normal brain anatomy (using an anatomical atlas), and a rectangular (2 x 4 pixels) ROI in the frontal, temporal, temporoparietal and occipital cortices. No differences were observed for the means of rCBF values between the single-slice and multi-slice ROI's with reference to the normal anatomy, but some variability was present for individual comparisons. In contrast, significantly higher mean rCBF values were obtained with the single-slice rectangular ROIs in all four regions for both patients and controls and considerable variability was shown for individual subjects. After analysis with multivariate logistic regression and receiver operator characteristic curves, the ability of SPET to discriminate between controls and Alzheimer patients was similar in the three methods for mild and moderate Alzheimer patients (Global Deterioration Scale = GDS of 3 and 4). However, with increasing dementia severity (GDS > 4) the rectangular ROIs showed lower ability to discriminate between groups compared to the single-slice and multi-slice anatomically defined ROIs.(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗
PubMed1994

Definition of initial grading, specific events, and overall outcome in patients with aneurysmal subarachnoid hemorrhage. A survey.

BACKGROUND AND PURPOSE: Scientific communication in medicine can be effective only if reports are based on unequivocal criteria for clinical conditions or specific diagnoses. METHODS: We reviewed all articles about subarachnoid hemorrhage published in nine neurosurgical or neurological journals from 1985 through 1992 and assessed the presence and the precision of definitions used for reporting the initial grade, the specific complications of rebleeding, delayed cerebral ischemia, and hydrocephalus, and the overall outcome. We identified 184 articles reporting direct observations in at least 10 patients on one or more of these conditions. RESULTS: Of 161 articles reporting the initial condition, only 19% used an unequivocal grading system (World Federation of Neurological Surgeons Scale or Glasgow Coma Scale); this proportion did not increase after 1988, when the World Federation of Neurological Surgeons Scale was introduced. The specific outcome events of rebleeding, ischemia, and hydrocephalus (283 instances) were sufficiently defined in only 31% of instances, incompletely in 22%, and not at all in 47%. The proportions were similar when the results were analyzed according to the type of complication, the year of publication, or per study. The four exclusively neurosurgical journals featured suitable definitions for any of the three outcome events in 20% of 209 instances, whereas the five mainly neurological journals published fewer articles about subarachnoid hemorrhage (74 instances of outcome events) but more often with precise criteria (65%). Overall outcome was adequately reported in 63% of all articles, with an increase over the years (54% in 1985 through 1988, 71% in 1989 through 1992). CONCLUSIONS: Reports about subarachnoid hemorrhage require closer scrutiny before publication to ascertain whether the conclusions about specific outcome events are based on unequivocal criteria.

Bias↗
PubMed1994

Predictive factors for deterioration from hydrocephalus after subarachnoid hemorrhage.

We studied the predictive factors for deterioration from hydrocephalus that developed during the first 28 days after admission in 660 patients following aneurysmal subarachnoid hemorrhage (SAH). Deterioration from hydrocephalus was defined as deterioration of consciousness with no detectable cause other than hydrocephalus confirmed by a repeat CT with a bicaudate index exceeding the 95th percentile for age. Deterioration from hydrocephalus occurred in 143 (22%) of the 660 patients. The variables included in the analysis were sex, age, loss of consciousness at ictus, sum score on the Glasgow Coma Scale on admission, sum score of cisternal blood and presence of ventricular blood on initial CT, hydrocephalus on initial CT, confirmed aneurysm, rebleeding, delayed cerebral ischemia, and treatment with tranexamic acid for 4 (short-term treatment) or 28 (long-term treatment) days. In a multivariate analysis with the Cox proportional hazards model incorporating fixed and time-dependent covariates, sum score of cisternal blood on initial CT (hazard ratio 3.15, p < 0.000001), presence of ventricular blood on initial CT (hazard ratio 1.66, p = 0.004), hydrocephalus on initial CT (hazard ratio 3.37, p < 0.000001), and long-term treatment with tranexamic acid (hazard ratio 2.40, p < 0.000001) were significantly related with the development of hydrocephalus. We conclude that a high amount of blood after SAH and delay of the resorption of cisternal and ventricular blood caused by long-term treatment with tranexamic acid increases the risk of deterioration from hydrocephalus after SAH.

Adult↗
PubMed1994

The diagnostic value of SPECT with Tc 99m HMPAO in Alzheimer's disease: a population-based study.

We studied the diagnostic accuracy of single-photon emission computed tomography (SPECT) with technetium 99m-labeled hexamethylpropylene amine oxime (Tc 99m HMPAO) in 48 patients with probable Alzheimer's disease (AD) according to NINCDS-ADRDA criteria and in 60 controls recruited from a population-based study. With logistic regression, we identified decreased temporal regional cerebral blood flow as the best discriminating variable between patients and controls. Receiver-operator characteristic curves showed that the discriminative ability of SPECT improved with increasing dementia severity. With specificity set at 90%, sensitivity figures were 42% in mild, 56% in moderate, and 79% in severe AD. The diagnostic gain as a function of the prior probability of the disease being present was computed for those with mild AD. When the prior probability varied at around 50%, the diagnostic gain for mild AD patients was substantial (a maximum of 34%) for a positive test result but poor for a negative test result. The results suggest that the practical usefulness of SPECT as a diagnostic adjunct in patients suspected of having mild AD is confined to situations in which, on clinical grounds, there is considerable diagnostic doubt.

Aged↗
PubMed1993

Epileptic seizures after subarachnoid hemorrhage.

We studied predictive factors for the occurrence of epilepsy in 381 consecutive patients admitted within 72 hours after they had a subarachnoid hemorrhage from a ruptured intracranial aneurysm. Fits occurring in the presence of hyponatremia or within 12 hours after the initial bleed, rebleeding, or aneurysm surgery were classified as associated with these acute events and we did not regard these fits subsequent epileptic seizures. Thirty-five patients (9%) had one or more epileptic seizures, 12 hours to 1,761 days after the initial bleed (median value, 18 days). The following variables were included in the analysis: sex, age, history of hypertension, history of cardiovascular disease, loss of consciousness at ictus, sum score on the Glasgow Coma Scale on admission, sum score for the amount of cisternal blood and presence of intraventricular blood based on the initial computed tomography (CT) scan, occurrence of ictal seizures (seizures occurring within 12 hours after the onset), acute hydrocephalus, rebleeding, delayed cerebral ischemia, fluid intake, treatment with tranexamic acid, ventricular drainage, and aneurysm surgery. After multivariate analysis by means of Cox proportional hazards model with stepwise forward selection of the variables, a high cisternal blood score and rebleeding proved to be significantly related to epilepsy (hazard ratio = 2.06, p = 0.040; and hazard ratio = 3.02, p = 0.016), even after the exclusion of 28 patients who received perioperative prophylactic anticonvulsant therapy (hazard ratio = 2.31, p = 0.022; and hazard ratio = 3.65, p = 0.006, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1993

Amount of blood on computed tomography as an independent predictor after aneurysm rupture.

BACKGROUND AND PURPOSE: After admission to the hospital of patients with aneurysmal subarachnoid hemorrhage, we assessed the predictive value of the extent of the hemorrhage on computed tomography in addition to that of clinical grading scales for poor outcome, infarction, and rebleeding. METHODS: We studied 471 consecutive patients with aneurysmal subarachnoid hemorrhage and used logistic regression with step-wise forward selection of variables. RESULTS: On admission, poor outcome was predicted by a low Glasgow Coma Scale score (odds ratio, 0.8; 95% confidence interval, 0.7-0.9); treatment with fluid restriction (2.5; 1.6-4.0); age over 52 (2.6; 1.7-3.9); loss of consciousness at ictus (1.7; 1.1-2.6); or a large amount of subarachnoid blood (2.0; 1.3-3.1). Delayed infarction was predicted by a large amount of subarachnoid blood (1.8; 1.2-2.6) or treatment with tranexamic acid (1.6; 1.1-2.4). Rebleeding was predicted by treatment with tranexamic acid (0.4; 0.3-0.7; protective effect); age over 52 (1.9; 1.2-3.0); loss of consciousness at ictus (1.7; 1.1-2.7); or admission to a neurosurgery service (0.6; 0.3-0.9; protective effect). Comparison of the observed and predicted outcome events showed that inclusion of the amount of subarachnoid blood into a predictive model added little to the prediction of poor outcome in general, but much to the prediction of delayed cerebral ischemia. CONCLUSIONS: The total amount of subarachnoid blood on the initial computed tomogram has independent predictive power for the occurrence of delayed cerebral ischemia.

Age Factors↗
PubMed1992

Distribution of cisternal blood in patients with acute hydrocephalus after subarachnoid hemorrhage.

The distribution of cisternal blood in relation to the development of acute hydrocephalus was studied in 246 consecutive patients with aneurysmal subarachnoid hemorrhage who were admitted within 72 hours. Patients with evidence on the initial computed tomograph (CT) of subarachnoid hemorrhage caused by other than a ruptured aneurysm and patients with a negative angiography were excluded. Acute hydrocephalus (defined as a bicaudate index, measured on the initial CT or on a repeat CT within 1 week after subarachnoid hemorrhage, exceeding the 95th percentile for age) was found on the initial CT in 50 (20%) of the 246 patients and on a repeat CT in 9 other patients. Ventricular blood was found significantly more often in patients with acute hydrocephalus than in those in whom acute hydrocephalus did not develop (28 of 59 [47%] versus 58 of 187 [31%]; chi 2 = 4.634, p = 0.031). When the analysis was restricted to the 86 patients with ventricular blood, no significant differences were found in the total amount of cisternal blood and in the distribution of cisternal blood between patients with and without hydrocephalus. In contrast, among the 160 patients without ventricular blood, hydrocephalus was associated with a slightly higher total amount of cisternal blood (Wilcoxon's rank sum test, p = 0.023), and significantly more patients with acute hydrocephalus had a higher score in both ambient cisterns than patients without acute hydrocephalus (20 of 31 [65%] versus 41 of 129 [32%]; chi 2 = 10.007, p = 0.002).(ABSTRACT TRUNCATED AT 250 WORDS)

Acute Disease↗
PubMed1992

Acute hydrocephalus in nonaneurysmal perimesencephalic hemorrhage: evidence of CSF block at the tentorial hiatus.

The acute hydrocephalus in patients with nonaneurysmal perimesencephalic hemorrhage suggests an extraventricular obstruction of CSF flow. We studied the occurrence of acute hydrocephalus and the site of cisternal blood in 40 consecutive patients with perimesencephalic hemorrhage. In all 11 patients with hydrocephalus, all perimesencephalic cisterns were filled with blood; this occurred in only five of the 29 patients (17%) without hydrocephalus (p less than 0.0001). We conclude that in the absence of intraventricular blood, filling of all perimesencephalic cisterns with blood is a necessary factor for the development of acute hydrocephalus.

Acute Disease↗