Detection of histamine-induced capillary protein leakage and hypovolaemia by determination of indocyanine green and glucose dilution method in dogs

\Objective:The plasma volume of histamine-induced protein capillary leakage may be overestimated when this is determined using the indocyanine green ( ICG) dilution method (Vd-ICG), since this dye binds to plasma proteins. The initial distribution volume of glucose (IDVG) has been shown to indicate t he central extracellular fluid volume including plasma. Accordingly, the ov erestimation would be detected by a higher Vd-ICG/IDVG ratio. Our study was intended to examine, whether the simultaneous measurement of these two var iables can evaluate histamine-induced protein leakage and associated hypovo laemia. Design: Prospective animal study. Setting: Institutional animal research laboratory. Subjects: Twenty-four anaesthetized and ventilated mongrel dogs. Interventions: Anaesthetized animals were mechanically ventilated and recei ved infusions of normal saline (n = 8), histamine 50 mu g/kg per h (n = 8), or histamine 100 mu g/kg per h. The Vd-ICG and IDVG were calculated using a one-compartment model by simultaneous administration of ICG 0.5 mg/kg, an d glucose 100 mg/kg followed by serial arterial blood sampling. Measurements and results: In both histamine groups, a significant elevation of haematocrit and a decrease of plasma albumin concentration were found ( p < 0.05). Although the IDVG decreased following histamine administration ( p < 0.05), the Vd-ICG remained unchanged. The Vd-ICG/IDVG ratio increased i n a dose-dependent manner after histamine administration (p < 0.05), but re mained unchanged following normal saline administration. Conclusion: The results suggest that the Vd-ICG/IDVG ratio and the IDVG are useful in evaluating the magnitude of the leakage and hypovolaemia.