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Biomedical subjects

R M Schell

Publications and source records attributed to R M Schell.

7 recordsLinked to original sources
PubMed1992

Focal cerebral ischemia in rats: effect of hemodilution with alpha-alpha cross-linked hemoglobin on CBF.

Hemodilution has had limited success as a treatment of cerebral ischemia. When using a nonoxygen binding fluid, the therapeutic efficacy of hemodilution-induced increases in CBF are offset by concomitant decreases in oxygen content. The effect of hemodilution, with diaspirin alpha-alpha cross-linked hemoglobin (DCLHb), on CBF during middle cerebral artery occlusion was assessed. Rats were hemodiluted to one of the following hematocrits (Hct): (a) 44/Hct, (b) 37/Hct, (c) 30/Hct, (d) 23/Hct, (e) 16/Hct, or (f) 9/Hct. After 10 min of ischemia, CBF was determined with 14C-iodoantipyrine. Coronal brain sections were evaluated for areas with a CBF of 0-10 and 11-20 ml 100 g-1 min-1. In addition, oxygen delivery was calculated. In the center of the ischemic zone, both areas of low CBF were less in the 30/Hct, 23/Hct, and 16/Hct groups compared with the 44/Hct and 37/Hct groups; and both areas were less in the 9/Hct group compared with the other five groups (p < 0.05). For the hemisphere contralateral to occlusion, there was a direct correlation between hematocrit and oxygen delivery. However, for the hemisphere ipsilateral to occlusion, oxygen delivery increased as hematocrit decreased (44/Hct, 8.6 +/- 0.3 vs. 9/Hct, 13.6 +/- 0.4 [mean +/- SD, ml 100 g-1 min-1]). The results of this study support a hypothesis that hemodilution with DCLHb decreases the extent of focal cerebral ischemia.

Animals↗
PubMed1992

Focal cerebral ischemia in rats: effects of induced hypertension, during reperfusion, on CBF.

The effect of phenylephrine-induced hypertension on CBF was investigated after 120 min of middle cerebral artery occlusion in rats. Blood pressure was manipulated by one of the following schedules during a 90-min period of reperfusion: 90/NORM, 90 min of normotensive reperfusion; 90/HTN, 90 min of hypertensive reperfusion (MABP increased by 30 mm Hg); or 15/HTN, the 90-min period of reperfusion was divided into 30 min of normotension, followed by 15 min of hypertension and 45 min of normotension. At the end of reperfusion, 100 microCi kg-1 of [14C]iodoantipyrine was given and an autoradiographic analysis of CBF performed. In the coronal brain section at the center of middle cerebral artery distribution, the area (percentage of hemisphere, mean +/- SD) with a CBF of 0-20 or 21-40 ml 100 g-1 min-1 was less (p less than 0.05) in the 15/HTN group (1 +/- 2 and 5 +/- 3%, respectively) versus the 90/HTN group (12 +/- 4 and 10 +/- 4%), which was in turn less than in the 90/NORM group (18 +/- 5 and 22 +/- 6%). These data are consistent with the hypothesis that during reperfusion a short interval of hypertension effectively augments CBF via an abrupt opening of collapsed vessels and that a more sustained interval of hypertension conveys no added benefit.

Animals↗
PubMed1992

Temporary cerebral ischemia. Effects of pentastarch or albumin on reperfusion injury.

Recent investigations have proposed that, after temporary ischemia, pentastarch may reduce microvascular permeability and reperfusion injury. However, this hypothesis has not been tested in the brain. Accordingly, after 180 min of temporary middle cerebral artery occlusion, the effect of pentastarch or albumin on blood-brain barrier permeability and cerebral injury was investigated in isoflurane-anesthetized rats. One of the following was maintained for the final 60 min of occlusion and throughout reperfusion: control-hematocrit was not manipulated; pentastarch-hematocrit was decreased to approximately 30% with pentastarch; or albumin-hematocrit was decreased (approximately 30%) with albumin. Part A (n = 21): 30 min of reperfusion was allowed, and blood-brain barrier permeability was determined with the indicator dye Evans Blue. Part B (n = 14): in different animals, 120 min of reperfusion was allowed, and cerebral injury (2,3,5-triphenyltetrazolium chloride stain) and edema (specific gravity) were assessed. Part C (n = 4): in different animals, the blood-brain barrier was evaluated by electron microscopy. Evans Blue (micrograms per gram brain tissue, mean +/- SD) was greater in the control (20.8 +/- 9.0) and albumin (15.5 +/- 7.3) groups versus the pentastarch (4.7 +/- 2.7) group (P less than 0.05). Brain injury (percent of hemisphere ipsilateral to occlusion) was less and specific gravity greater in the pentastarch (33 +/- 8 and 1.040 +/- 0.003 respectively) versus the albumin group (45 +/- 6 and 1.035 +/- 0.003). This study supports the hypothesis that during temporary cerebral ischemia, pentastarch decreases brain injury and edema.(ABSTRACT TRUNCATED AT 250 WORDS)

Albumins↗
PubMed1991

Persistent sacral nerve root deficits after continuous spinal anaesthesia.

Neurological deficits following spinal anaesthesia are rare. We report two cases of persistent sacral nerve root deficits after continuous spinal anaesthesia (CSA) performed with hyperbaric lidocaine through a lumbar microcatheter. In both cases the dose of 5% lidocaine (5.7 and 4.3 ml) was greater than usual. In the immediate postoperative period the constellation of neurological deficits included perianal hypaesthesia, lower extremity paresis, urinary retention, and difficult defaecation. Both patients have residual perianal hypaesthesia and difficult defaecation. In these cases, the high-dose requirements of local anaesthetic via microcatheter CSA with focal sensory block suggests nonuniform distribution of the hyperbaric lidocaine. Microcatheter CSA may convey a unique risk of maldistribution of the local anaesthetic solution and local neurotoxicity.

Aged↗
PubMed1991

L-644,711, a novel anion transport inhibitor, increases isoflurane MAC in rats.

The effect of the anion transport inhibitor L-644,711 on isoflurane MAC was determined in rats (n = 24). After baseline MAC determination, each rat received one of the following drug protocols: (a) control, vehicle only; (b) L-644,711IT, a 3-mg/kg intrathecal bolus of L-644,711 followed by an infusion at 1.5 mg.kg-1.h-1; or (c) L-644,711IV, a 6-mg/kg intravenous bolus of L-644,711 followed by an infusion at 3 mg.kg-1.h-1. MAC was again determined. The baseline isoflurane MAC was not different between groups (control, 1.52% +/- 0.15%; L-644,711IT, 1.51% +/- 0.24%; L-644,711IV, 1.54% +/- 0.13% [mean +/- SD]). After drug or vehicle administration, isoflurane MAC was larger for the L-644,711IT group (2.25% +/- 0.17%) versus the control (1.38% +/- 0.13%) and L-644,711IV (1.39% +/- 0.15%) groups (P less than 0.05). These data are consistent with the hypothesis that isoflurane anesthesia is influenced by anion channels and that blocking these channels may reduce the pharmacodynamic potency of isoflurane.

Anesthesia, Inhalation↗