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Biomedical subjects

D A Stump

Publications and source records attributed to D A Stump.

At least 55 records · Page 3Linked to original sources
PubMed1989

Cerebral blood flow is reduced in patients with sepsis syndrome.

The relationship between sepsis-induced CNS dysfunction and changes in brain blood flow remains unknown, and animal studies examining the influence of sepsis on cerebral blood flow (CBF) do not satisfactorily address that relationship. We measured CBF and cerebrovascular reactivity to CO2 in nine patients with sepsis syndrome using the 133Xe clearance technique. Mean CBF was 29.6 +/- 15.8 (SD) ml/100 g.min, significantly lower than the normal age-matched value in this laboratory of 44.9 +/- 6.2 ml/100 g.min (p less than .02). This depression did not correlate with changes in mean arterial pressure. Despite the reduction in CBF, the specific reactivity of the cerebral vasculature to changes in CO2 was normal, 1.3 +/- 0.9 ml/100 g.min/mm Hg. Brain blood flow is reduced in septic humans; the contribution of this reduction to the metabolic and functional changes observed in sepsis requires further study.

Adult↗
PubMed1989

Regional cerebral blood flow in childhood headache.

Regional cerebral blood flow (rCBF) was measured in 16 cranial regions in 23 children and adolescents with frequent headaches using the non-invasive Xenon-133 inhalation technique. Blood flow response to 5% carbon dioxide (CO2) was also determined in 21 patients, while response to 50% oxygen was measured in the two patients with hemoglobinopathy. Included were 10 patients with a clinical diagnosis of migraine, 4 with musculoskeletal headaches, and 3 with features of both types. Also studied were 2 patients with primary thrombocythemia, 2 patients with hemoglobinopathy and headaches, 1 patient with polycythemia, and 1 with headaches following trauma. With two exceptions, rCBF determinations were done during an asymptomatic period. Baseline rCBF values tended to be higher in these young patients than in young adults done in our laboratory. Localized reduction in the expected blood flow surge after CO2 inhalation, most often noted posteriorly, was seen in 8 of the 13 vascular headaches, but in none of the musculoskeletal headache group. Both patients with primary thrombocythemia had normal baseline flow values and altered responsiveness to CO2 similar to that seen in migraineurs; thus, the frequently reported headache and transient neurologic signs with primary thrombocythemia are probably not due to microvascular obstruction as previously suggested. These data support the concept of pediatric migraine as a disorder of vasomotor function and also add to our knowledge of normal rCBF values in younger patients. Demonstration of altered vasomotor reactivity to CO2 could prove helpful in children whose headache is atypical.

Adolescent↗
PubMed1989

Pentoxifylline increases cerebral blood flow in patients with cerebrovascular disease.

We determined the immediate effects of pentoxifylline on cerebral blood flow in 10 patients with cerebrovascular disease; four received 400 mg and six received 800 mg pentoxifylline orally. Regional cerebral blood flow was measured before (baseline) and 2, 4, and 6 hours after pentoxifylline administration using the xenon-133 clearance technique with 16 detectors (eight per hemisphere). Global cerebral blood flow as a percentage of the baseline value increased significantly after 800 mg but not 400 mg pentoxifylline (p = 0.017 and p = 0.29, respectively). Regional cerebral blood flow as a percentage of the baseline value at the detector with the lowest baseline value increased significantly 2 hours after both 400 mg and 800 mg pentoxifylline (p = 0.038 and p = 0.010, respectively). Cerebrovascular reactivity to carbon dioxide was preserved despite the increases in cerebral blood flow. Pentoxifylline increases cerebral blood flow and is not associated with "intracerebral steal" in patients with cerebrovascular disease.

Aged↗
PubMed1989

Cerebral blood flow does not change following sodium nitroprusside infusion during hypothermic cardiopulmonary bypass.

Changes in cerebral blood flow (CBF) associated with decreases in mean arterial pressure (MAP) produced by sodium nitroprusside (SNP) infusion were measured by intra-aortic injection of 133Xe in 17 patients during hypothermic cardiopulmonary bypass (CPB). In each patient, CBF was determined at baseline and then again following SNP-induced reduction of MAP. Two groups were studied. In Group I (n = 9), PaCO2 was maintained near 42 mm Hg uncorrected for nasopharyngeal temperature (NPT). In Group II (n = 8), PaCO2 was maintained near 60 mm Hg, uncorrected for NPT. Nasopharyngeal temperature, MAP, pump oxygenator flow, PaO2, and hematocrit were maintained within a narrow range in each patient during both studies. Since the baseline CBF determinations were conducted at the higher MAP in all subjects, we corrected post-SNP CBF data for the spontaneous decline that occurs over time during CPB. In Group I, a reduction in MAP from 76 +/- 9 mm Hg (mean +/- SD) to 50 +/- 6 mm Hg was associated with a reduction in CBF from 17 +/- 5 to 13 +/- 3 ml.100 g.min-1 (P less than 0.01), a decrease that became statistically insignificant once the time correction factor had been applied (16 +/- 4 ml.100 g-1.min-1). In Group II, MAP declined from 75 +/- 5 mm Hg to 54 +/- 5 mm Hg, and CBF declined from 25 +/- 10 to 17 +/- 7 ml.100 g.min-1 (P less than 0.01), but, again, after time correction, the CBF decline was statistically insignificant (22 +/- 8 ml.100 g-1.min-1).(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1989

Cerebral physiologic monitoring.

Cerebral physiologic monitoring techniques can be categorized into those measuring perfusion, metabolism, and function. The physiologic basis for each of these is outlined, with a description of the clinical methods currently available. The clinical application of each monitoring modality is discussed with special reference to its impact on outcome of the brain-injured patient.

Brain↗
PubMed1989

The effect of age on cerebral blood flow during hypothermic cardiopulmonary bypass.

Cerebral blood flow was measured in 20 patients by xenon 133 clearance methodology during nonpulsatile hypothermic cardiopulmonary bypass to determine the effect of age on regional cerebral blood flow during these conditions. Measurements of cerebral blood flow at varying perfusion pressures were made in patients arbitrarily divided into two age groups at nearly identical nasopharyngeal temperature, hematocrit value, and carbon dioxide tension and with equal cardiopulmonary bypass flows of 1.6 L/min/m2. The range of mean arterial pressure was 30 to 110 mm Hg for group I (less than or equal to 50 years of age) and 20 to 90 mm Hg for group II (greater than or equal to 65 years of age). There was no significant difference (p = 0.32) between the mean arterial pressure in group I (54 +/- 28 mm Hg) and that in group II (43 +/- 21 mm Hg). The range of cerebral blood flow was 14.8 to 29.2 ml/100 gm/min for group I and 13.8 to 37.5 ml/100 gm/min for group II. There was no significant difference (p = 0.37) between the mean cerebral blood flow in group I (21.5 +/- 4.6 ml/100 gm/min) and group II (24.3 +/- 8.1 ml/100 gm/min). There was a poor correlation between mean arterial pressure and cerebral blood flow in both groups: group I, r = 0.16 (p = 0.67); group II, r = 0.5 (p = 0.12). In 12 patients, a second cerebral blood flow measurements was taken to determine the effect of mean arterial pressure on cerebral blood flow in the individual patient. Changes in mean arterial pressure did not correlate with changes in cerebral blood flow (p less than 0.90). We conclude that age does not alter cerebral blood flow and that cerebral blood flow autoregulation is preserved in elderly patients during nonpulsatile hypothermic cardiopulmonary bypass.

Aged↗
PubMed1988

Response of cerebral blood flow to phenylephrine infusion during hypothermic cardiopulmonary bypass: influence of PaCO2 management.

Twenty-eight adult patients anesthetized with fentanyl, then subjected to hypothermic cardiopulmonary bypass (CPB), were studied to determine the effect of phenylephrine-induced changes in mean arterial pressure (MAP) on cerebral blood flow (CBF). During CPB patients managed at 28 degrees C with either alpha-stat (temperature-uncorrected PaCO2 = 41 +/- 4 mmHg) or pH-stat (temperature-uncorrected PaCO2 = 54 +/- 8 mmHg) PaCO2 for blood gas maintenance received phenylephrine to increase MAP greater than or equal to 25% (group A, n = 10; group B, n = 6). To correct for a spontaneous, time-related decline in CBF observed during CPB, two additional groups of patients undergoing CPB were either managed with the alpha-stat or pH-stat approach, but neither group received phenylephrine and MAP remained unchanged in both groups (group C, n = 6; group D, n = 6). For all patients controlled variables (nasopharyngeal temperature, PaCO2, pump flow, and hematocrit) remained unchanged between measurements. Phenylephrine data were corrected based on the data from groups C and D for the effect of diminishing CBF over time during CPB. In patients in group A CBF was unchanged as MAP rose from 56 +/- 7 to 84 +/- 8 mmHg. In patients in group B CBF increased 41% as MAP rose from 53 +/- 8 to 77 +/- 9 mmHg (P less than 0.001). During hypothermic CPB normocarbia maintained via the alpha-stat approach at a temperature-uncorrected PaCO2 of approximately equal to 40 mmHg preserves cerebral autoregulation; pH-stat management (PaCO2 approximately equal to 57 mmHg uncorrected for temperature, or 40 mmHg when corrected to 28 degrees C) causes cerebrovascular changes (i.e., impaired autoregulation) similar to those changes produced by hypercarbia in awake, normothermic patients.

Aged↗
PubMed1988

Theophylline effect on the cerebral blood flow response to hypoxemia.

Cerebral oxygen delivery (CO2D) remains nearly constant over a wide range of cerebral perfusion pressure and arterial oxygen content. In response to a decrease in arterial oxygen content secondary to hypoxemia, cerebral blood flow (CBF) increases, a response likely mediated by the release of adenosine. We studied the effect of theophylline, a potent adenosine antagonist, on CBF and cerebral oxygen delivery (CO2D) during hypoxemia in five healthy adult male volunteers. The CBF was measured using 133Xe clearance under conditions of (1) normoxemia (O2 saturation greater than 95 percent); (2) hypoxemia (O2 saturation = 80 percent); (3) normoxemia following aminophylline (the ethylene diamine salt of theophylline) 6 mg/kg intravenously; and (4) hypoxemia following aminophylline. Aminophylline decreased CBF and CO2D during both normoxemia and hypoxemia, but did not prevent the increase in CBF accompanying hypoxemia, suggesting that the increase in CBF in response to hypoxemia may not be mediated by adenosine or that customary doses of aminophylline are insufficient to inhibit adenosine-mediated cerebral vasodilation in response to hypoxemia. The significant decrease in CBF and CO2D observed following aminophylline is potentially clinically important and should be considered in the selection of bronchodilator therapy.

Adult↗
PubMed1987

Effects of resuscitation from hemorrhagic shock on cerebral hemodynamics in the presence of an intracranial mass.

This study compares intracranial pressure, cerebral blood flow, and cerebral oxygen transport during hemorrhagic shock and following fluid resuscitation with crystalloid or colloid solution in a canine model with an epidural mass lesion. After placement of an epidural balloon, intracranial pressure was increased to 30 mm Hg for 5 minutes and then permitted to vary without further manipulation. Hemorrhagic shock was produced by the rapid removal of blood to achieve a mean arterial pressure of 55 mm Hg for 30 minutes. Resuscitation then was performed with intravenous lactated Ringer's solution, 60 ml/kg, or with 6.0% hetastarch, 20 ml/kg. Following both solutions mean arterial pressure and cardiac output were increased and hemoglobin concentration was reduced. Intracranial pressure was significantly lower immediately after resuscitation in the hetastarch group; it then gradually increased so that the difference was much less 1 hour later. Cerebral blood flow decreased during shock and was not restored by either fluid; cerebral oxygen transport fell further with resuscitation in both groups due to hemodilutional reductions in hemoglobin. Although colloid resuscitation improved systemic hemodynamics and maintained lower intracranial pressure, it failed, as did crystalloid resuscitation, to restore cerebral oxygen transport to prehemorrhagic shock levels.

Animals↗
PubMed1987

The effect of aminophylline on cerebral blood flow in patients with chronic obstructive pulmonary disease.

Aminophylline has been shown to produce a reduction in cerebral blood flow (CBF) in animal models and patients with neurologic symptoms or signs. The effect of aminophylline on regional CBF (rCBF) in patients with chronic obstructive pulmonary disease (COPD) has not previously been reported to our knowledge. We studied the effect of loading and maintenance infusions of aminophylline on CBF in five subjects with moderate to severe COPD. rCBF was determined in eight homologous regions of each cerebral hemisphere at three intervals: (1) baseline; (2) following the IV loading dose of aminophylline (6.0 mg/kg body weight); and (3) early and late in the maintenance infusion (0.5 mg/kg/hr) period. Aminophylline loading caused a 26 percent reduction (p = 0.005) in mean rCBF from 40.6 +/- 5.2 (SD) ml/100 g/min to 30.1 +/- 6.0 ml/100 g/min. A 23 percent reduction (31.5 +/- 6.9 ml/100 g/min) persisted throughout the maintenance phase. Thus, aminophylline, as customarily used in subjects with COPD, is associated with a significant reduction in rCBF.

Adult↗
PubMed1986

Response of cerebral blood flow to changes in carbon dioxide tension during hypothermic cardiopulmonary bypass.

Changes in cerebral blood flow (CBF) in response to changes in PaCO2 were measured by intraaortic injection of 133Xe in 12 patients during hypothermic (23-30 degrees C) cardiopulmonary bypass. In each patient, CBF was determined at two randomly ordered levels of PaCO2 obtained by varying the rate of gas inflow into the pump oxygenator (Group I, n = 6) or by varying the percentage of CO2 added to the gas inflow (Group II, n = 6). Nasopharyngeal temperature, mean arterial pressure, pump-oxygenator flow, and hematocrit were maintained within a narrow range. In group I, a PaCO2 (uncorrected for body temperature) of 36 +/- 4 mmHg (mean +/- SD) was associated with a CBF of 13 +/- 5 ml X 100 g-1 X min-1, while a PaCO2 of 42 +/- 4 mmHg was associated with a CBF of 19 +/- 10 ml X 100 g-1 X min-1. In group II, a PaCO2 of 47 +/- 3 mmHg was associated with a CBF of 20 +/- 8 ml X 100 g-1 X min-1, and a PaCO2 of 53 +/- 3 mmHg was associated with a CBF of 26 +/- 9 ml X 100 g-1 X min-1. Within group I, the difference in CBF was significant (P less than 0.05); within group II, the difference in CBF was significant at the P less than 0.002 level. All CBF measurements were lower than those reported for normothermic, unanesthetized subjects of similar age.(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗
PubMed1986

Cerebral hemodynamics after hemorrhagic shock: effects of the type of resuscitation fluid.

Cerebral blood flow (CBF), cerebral oxygen delivery, and intracranial pressure were measured in 12 dogs subjected to hemorrhagic shock and then resuscitated with lactated Ringer's solution or 6% hetastarch. Hemorrhagic shock was produced by the rapid removal of blood to achieve a mean arterial pressure (MAP) of 40 mm Hg with BP maintained at that level for 30 min. Six animals were resuscitated with lactated Ringer's solution, 60 ml/kg iv, and six with 6% hetastarch, 20 ml/kg iv. Both solutions effectively restored systemic hemodynamic stability, increasing cardiac output and MAP. Intracranial pressure was significantly (p less than .05) lower after resuscitation in the hetastarch group, but CBF, which had decreased during shock, was not normalized by either fluid, and cerebral oxygen transport fell further with resuscitation secondary to a hemodilutional reduction of hemoglobin. Although 6% hetastarch may improve systemic hemodynamics and maintain a low intracranial pressure during resuscitation, it fails, as does lactated Ringer's solution, to restore cerebral oxygen transport to prehemorrhagic shock levels.

Animals↗
PubMed1986

Effects of hypertonic saline versus lactated Ringer's solution on cerebral oxygen transport during resuscitation from hemorrhagic shock.

Hypertonic saline successfully restores systemic hemodynamics in dogs and humans with severe hemorrhagic shock and, in contrast to lactated Ringer's solution, does not increase intracranial pressure (ICP). This study compares cerebral oxygen delivery in 12 dogs subjected to hemorrhagic shock by the rapid removal of blood (mean arterial pressure of 40 mm Hg maintained for 30 minutes), and then resuscitated with lactated Ringer's solution (six dogs) or 7.5% saline solution (six dogs) to restore systolic arterial pressure. Both solutions effectively restored systemic hemodynamic stability, increasing cardiac output and systolic blood pressure while decreasing mean and diastolic arterial pressure and systemic vascular resistance. The ICP was significantly lower after resuscitation in the hypertonic saline group (p less than 0.05), but cerebral blood flow, which had decreased during shock, was not restored by either fluid, and cerebral oxygen transport fell further secondary to a hemodilutional reduction of hemoglobin. Although hypertonic saline may improve systemic hemodynamics and maintain a low ICP during resuscitation, it fails, as does Ringer's solution, to restore cerebral oxygen transport to prehemorrhagic shock levels.

Animals↗
PubMed1985

Effects on cerebral hemodynamics of resuscitation from endotoxic shock with hypertonic saline versus lactated Ringer's solution.

This study was carried out to determine whether 7.5% hypertonic saline (HSS) and lactated Ringer's solution restore cerebral hemodynamics comparably when used for resuscitation from endotoxic shock. Endotoxic shock was produced in 13 dogs by the iv administration of 1.5 mg/kg Escherichia coli endotoxin. After 90 min of shock, seven animals were resuscitated with lactated Ringer's solution, 60 ml/kg iv, and six with 7.5% HSS, 6 ml/kg iv. Both solutions increased cardiac output and mean arterial pressure. With HSS, intracranial pressure was lower immediately after resuscitation (p less than .001) and one hour later (p less than .01). However, cerebral blood flow was not increased by either fluid and, due to hemodilution, cerebral oxygen transport decreased during resuscitation in both groups of animals. Thus, HSS restored systemic hemodynamics and maintained a lower intracranial pressure during resuscitation from endotoxic shock, but failed, as did lactated Ringer's solution, to restore cerebral blood flow and oxygen transport.

Animals↗
PubMed1984

The transient global amnesia-migraine connection.

Twelve patients with transient global amnesia (TGA) were studied. Seven (58%) of the 12 had a headache during their attack; five (42%) of the 12 were migraineurs. Measurement of regional cerebral blood flow (rCBF) by the xenon Xe 133 inhalation method showed similar patterns of flow in five of the seven patients tested. The rCBF abnormalities were impaired vasomotor response in the watershed area between the middle cerebral artery and posterior cerebral artery territories, and/or focal ischemia in the inferior part of the temporal lobe. These rCBF abnormalities differed from those seen in patients with carotid transient ischemic attacks (TIAs) and vertebrobasilar TIAs. We speculate that the vasomotor phenomena in migraine may play a major role in the cause of TGA.

Aged↗