Change in plasma volume from a state of hyper-, normo- or hypovolemia with or without noradrenalin infusion in the rat.

Fluid substitution is important in critically ill patients to maintain normovolemia, but there is always a risk that the treatment is too aggressive resulting in fluid overload, or is insufficient with maintenance of hypovolemia. The present study on the rat aims at evaluating the change in plasma volume after 2.5 h from a state of hyper- and hypovolemia.

Mechanisms behind postspinal headache and brain stem compression following lumbar dural puncture--a physiological approach.

Background: The cause of postspinal headache and its specific characteristics are unknown, and whether lumbar dural puncture (LP) triggers brain-stem compression in patients with brain oedema is still controversial.

Methods: Hydrostatic effects of distal opening of the dural sac towards the atmosphere are described and applied to the normal brain and the brain with disrupted BBB. Analogue analyses from previous results using an isolated skeletal muscle enclosed in a rigid shell were applied to the brain in an attempt to simulate and verify the haemodynamic effects of distal opening of the spinal canal.

Effects on intracranial pressure of dural puncture in supine and head-elevated positions. A study on the cat.

Background: Lumbar dural puncture may reduce intracranial pressure (ICP) due to a hydrostatic pressure gradient created by distal opening of the spinal fluid column towards the atmosphere. The magnitude of the reduction in hydrostatic force on the brain should depend on the vertical distance between the brain and the dural opening, and thus will increase by head elevation. No studies have analyzed ICP after dural puncture in supine and upright positions.

Volume expansion of albumin, gelatin, hydroxyethyl starch, saline and erythrocytes after haemorrhage in the rat.

Objective: To compare the colloids 5% albumin, 4% gelatin and 6% hydroxyethyl starch (HES) 130/0.4 with each other and with saline, regarding their plasma-expanding effects after haemorrhage; these were also compared with the intravascular volume-expanding effect of re-transfusion with erythrocytes.

Design: Controlled, prospective, randomised laboratory study.

Beneficial effects of low-dose prostacyclin on cat intestinal perfusion during endotoxemia as evaluated with microdialysis and oxygen transport variables.

Objective: To evaluate the effects of low-dose prostacyclin on intestinal perfusion during endotoxemia.

Design: A randomized, blinded experimental study.

Setting: A university laboratory.

Role of prostacyclin and nitric oxide in regulation of basal microvascular hydraulic permeability in cat skeletal muscle.

The effects of prostacyclin, nitric oxide (NO) and beta2-receptor stimulation on capillary filtration coefficient (CFC) and vascular tone were analyzed in an autoperfused cat skeletal muscle in vivo preparation, to evaluate if these substances are involved in regulation of basal microvascular hydraulic permeability. CFC was increased from control (100%) to 124% with the prostacyclin-synthase inhibitor tranylcypromine and restored by simultaneous infusion of prostacyclin at 0.1 ng.

Local vascular responses to elevation of an organ above the heart.

Elevation of an organ above the heart reduces the arterial and venous hydrostatic pressures in proportion to the height of elevation. Intact autoregulation protects organs, such as the brain and skeletal muscle, from significant alterations in blood flow and hydrostatic capillary pressure due to the decrease in arterial inflow pressure during such a manoeuvre. However, the consequences of the decreased hydrostatic pressure on the venous side are far from clarified.

Effects of selective ETB-receptor stimulation on arterial, venous and capillary functions in cat skeletal muscle.

1. This paper describes, in quantitative terms, the in vivo effects of two selective ETB-receptor agonists (IRL 1620 and BQ 3020) on vascular resistance (tone) in the following consecutive sections of the vascular bed of sympathectomized cat skeletal muscle: large-bore arterial resistance vessels (> 25 microns), small arterioles (< 25 microns) and the veins. The effects on capillary pressure transcapillary fluid exchange were also recorded.

Myogenic vascular regulation in skeletal muscle in vivo is not dependent of endothelium-derived nitric oxide.

The hypothesis, based on in vitro experiments on large conduit arteries, that endothelium-derived nitric oxide is a mediator of vascular myogenic reactivity was tested in cat gastrocnemius muscle in vivo. This was done by comparing, in the absence and presence of effective endothelium-derived nitric oxide blockade by the specific inhibitors NG-monomethyl-L-arginine or NG-nitro-L-arginine methyl ester, myogenic responses in defined consecutive vascular sections to dynamic vascular transmural pressure stimuli, to arterial occlusion (reactive hyperaemia), and to arterial pressure changes (autoregulation of blood flow and capillary pressure). The results demonstrated that the myogenic vascular reactivity to quick ramp transmural pressure stimuli was not attenuated by endothelium-derived nitric oxide blockade, but rather reinforced.

Effects of thiopental on resistance vessels in cat skeletal muscle.

Barbiturates are used clinically as anaesthetics and to reduce raised intracranial pressure. One side effect is hypotension, usually ascribed to a depression of cardiac contractility, while their effects on the resistance vessels are more controversial: both vasodilation and vasoconstriction have been described. This study analyzes the effects of thiopental on basal vascular tone in the cat skeletal muscle.