K Haselsberger — Page 2

PubMed1987

Effect of intravenous mannitol on cat pial arteries and veins during normal and elevated intracranial pressure.

In two series of cats, totaling 12 animals, the effect of 1 g of intravenous mannitol per kg over 15 minutes on pial vessels (cranial window technique, multichannel videoangiometry) and intracranial pressure (ICP) was investigated under circumstances of normal ICP and ICP elevated to 20 mm Hg by the cisternal infusion of mock cerebrospinal fluid. Under conditions of normal ICP, mannitol induced an 18% reduction of ICP at the end of the infusion and a further decrease to 38% below the initial level 10 minutes later. Pial veins and arteries remained more or less unreactive over 35 minutes, with changes never exceeding 2 to 3%. Administration of mannitol during elevated ICP (20 mm Hg) reduced ICP by 15% during the administration period; during the subsequent 15 minutes, ICP returned to pretreatment levels. Pial arteries remained unreactive during mannitol infusion; however, they started to dilate during the subsequent 15 minutes to +8%. Venous calibers showed no noticeable changes. It is concluded that mannitol in clinically relevant doses does not exert a significant constrictive effect on cerebral arteries and veins and that mannitol acts on ICP probably via an osmotic effect rather than by a direct effect on cerebral blood volume.

Animals↗

PubMed1986

Effect of the barbiturate methohexital on cerebral vessels and intracranial pressure.

Reactions of pial arteries and veins as well as intracranial pressure (ICP) and mean arterial pressure during intravenous administration of methohexital were observed in two groups of cats totaling 24 animals in order to investigate hypothesized direct barbiturate effects on cerebral vascular volume. Group 1 had bolus injection of 1 mg/kg followed by infusion of 0.1 mg/kg/min over 60 minutes. This induced a 6 to 7% arterial dilatation at 50 to 60 minutes (not significant); a 20% reduction of pial vein calibers was observed (P less than 0.01). In Group 2, the same treatment protocol administered under conditions of ICP elevation to 20 mm Hg by the cisternal infusion of mock cerebrospinal fluid resulted again in consistent, although less extensive, venous caliber reduction (5 to 7%, P less than 0.01). In Group 2 controls, pial arteries dilated by 15 to 20%; this reaction was suppressed in the methohexital-treated animals. After stopping methohexital, however, arteries in the methohexital group dilated to almost the same extent as in controls. Mean arterial pressure remained stable in both groups. ICP was not reduced by methohexital. EEG-activity was slightly increased during treatment. We conclude that methohexital has a direct effect on vessel caliber and thus cerebral blood volume via absolute diminution of venous vessels and suppression of ICP-induced autoregulative arterial dilatation. This direct vascular effect, however, seems to be counterbalanced by unknown intracranial mass effects that prevent a reduction in ICP.

Animals↗