In vitro, halogenated agents reduce the pulmonary vasoconstrictor response to alveolar hypoxia in isolated perfused lungs. However, studies in intact animals have been less convincing. The aim of the present study was to assess the effect of sevoflurane on hypoxic pulmonary vasoconstriction (HPV) in anaesthetized piglets using the pressure/cardiac index relationship (P/Q). Ten large white piglets were anaesthetized and mechanically ventilated, alternately in hyperoxia (FIO2 = 0.4) and hypoxia (FIO2 = 0.12). Multipoint plots of pulmonary arterial pressure (PAP) or differences between PAP and left atrial pressure (LAP) against Q were generated by gradual inflation of a balloon introduced into the inferior vena cava. P/Q relationships were established in hyperoxia and hypoxia at baseline, and then with sevoflurane. In hypoxia, pressure gradients (PAP-LAP) increased at every level of Q, thus demonstrating active pulmonary vasoconstriction. Sevoflurane at 1 MAC did not affect these P/Q relationships in hyperoxia or hypoxia as compared with baseline. Sevoflurane at a clinically relevant concentration (1 MAC) has no significant effect on HPV in anaesthetized piglets.

The effect of hypertonic saline dextran solutions on hypoxic pulmonary vasoconstriction in anaesthetised piglets. M. Bellezza, F. Kerbaul, L. Roussel, M. Imbert, C. Guidon. #ERS Journals Ltd 2002. ABSTRACT: Hypoxic pulmonary vasoconstriction (HPV) is a regulatory mechanism by which blood is diverted from poorly ventilated to better ventilated areas of the lung. The aim of the present study was to assess the extent to which hypertonic saline dextran and dextran solutions modify the magnitude of HPV during isovolumic haemodilution in intact acutely instrumented piglets.Eighteen large white piglets were anesthetised and assigned to two groups. Mean pulmonary arterial pressure (PAP) and cardiac output (Q), systemic arterial pressure and left arterial pressure (LAP) were measured. A decrease in Q was obtained by reducing venous return. This enabled measurement of transpulmonary pressures (mean PAP minus LAP) at four levels of Q in hyperoxia (inspiratory oxygen fraction (Fi,O 2 )=0.4), then in hypoxia (Fi,O 2= 0.1) in the two groups before blood soustraction (10 mL?kg -1 ) and after loading with sodium chloride (NaCl) 7.5% and dextran 6% or with dextran 6% alone. Dextran alone led to a decrease in mean PAP-LAP/Q values, and NaCl with dextran was associated with a significant shift of mean PAP-LAP/Q plots to higher pressures in hypoxia.Hypertonic saline dextran solution, as replacement fluid in isovolaemic haemodilution increased the magnitude of hypoxic pulmonary vasoconstriction, whereas dextran solution reduced it. Fluid expanders are usually used for the resuscitation of intraoperative hypovolaemia or haemorragia. They act on different parts of the cardiovascular system, mainly the heart and vascular resistances. Therefore, the vascular resistance response differs with the solution used and the vascular bed of the organ studied [1,2].Hypertonic saline solution (sodium chloride (NaCl) 7.5%) with dextran 6% has been shown to increase volaemia ten-times more than dextran 6% by an osmotic effect (transfer of water from the interstitial to vascular space), this, in turn, increases cardiac output (Q) and decreases systemic vascular resistance [3,4]. However, the effect of this hypertonic saline and dextran solution on pulmonary circulation remains unknown. Dextran used alone can also reduce pulmonary vascular resistance (PVR) resulting in a reduction of blood viscosity.Therefore, the effect of these two different plasma expanders on pulmonary vascular circulation was studied, focusing on the hypoxic pulmonary vascular response using pressure (P)/Q relationships in intact anaesthetised piglets submitted to normovolaemic haemodilution. It was hypothesised that these two different plasma expanders would have different effects on hypoxic pulmonary vasoconstriction (HPV), and thereby modify gas exchange. Piglets were chosen because they exhibit the greatest pulmonary vasoconstriction response to hypoxia [5]. In this study, pulmonary haemodynamics were evaluated by multipoint P/Q (mean pulmonary arterial pressure (PAP)-LAP/Q) ...

A simple dietary question may identify older patients with hypovitaminosis D who should receive vitamin D supplements.

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