In the converging fields of neuroendocrinology and behavioural neuroscience, the interaction between peripheral secretion and central release of oxytocin in humans has not yet been comprehensively assessed. As the human brain is not directly accessible and as the collection of human cerebrospinal fluid (CSF) usually requires invasive procedures, easier accessible compartments such as blood or saliva attract increasing attention. In this study, we prospectively determined oxytocin concentrations in the three compartments plasma, CSF and saliva of fifty critically ill patients with neurological and neurosurgical diseases. All samples per patient were collected concomitantly. Oxytocin was measured by a highly sensitive and specific radioimmunoassay. Strength of correlation was assessed by the Spearman rank correlation coefficient. Correlation analyses revealed modest to strong correlations for oxytocin between the saliva and CSF compartments while predominantly weak correlations were found between the CSF and plasma as well as between the plasma and saliva compartments. In conclusion, we demonstrated modest to strong correlations between the saliva and CSF compartment suggesting that saliva oxytocin may help to assess CSF oxytocin levels. In contrast, plasma oxytocin failed to correspond well with CSF oxytocin levels as predominantly weak correlations were found between the CSF and plasma as well as between the plasma and saliva compartments which are unlikely to have a biological relevance. Further research is needed to clarify to what extent saliva oxytocin may serve as a biomarker reflecting brain oxytocin activity. This article is protected by copyright. All rights reserved.

In anesthetized dogs ventilated with room air and hemodiluted to a Hb of 7 g per dL, simple oxygen therapy by HV (FIO2 1.0) rapidly improves tissue oxygenation and permits extended hemodilution to Hb of 5.8 g per dL until the HV-induced effects are lost.

Bolus intravenous administration of 60-percent (wt/vol) perflubron emulsion and further hemodilution from a Hb of 7 g per dL to one of 3 g per dL were as effective as autologous RBC transfusion in maintaining tissue oxygenation during volume-compensated blood loss designed to mimic surgical bleeding.

Acute normovolemic hemodilution (ANH) is efficient in reducing allogenic blood transfusion needs during elective surgery. Tissue oxygenation is maintained by increased cardiac output and oxygen extraction and, presumably, a more homogeneous tissue perfusion. The aim of this study was to investigate blood flow distribution and oxygenation of skeletal muscle. ANH from hematocrit of 36 +/- 3 to 20 +/- 1% was performed in 22 splenectomized, anesthetized beagles (17 analyzed) ventilated with room air. Normovolemia was confirmed by measurement of blood volume. Distribution of perfusion within skeletal muscle was determined by using radioactive microspheres. Tissue oxygen partial pressure was assessed with a polarographic platinum surface electrode. Cardiac index (3.69 +/- 0.79 vs. 4.79 +/- 0.73 l. min-1. m-2) and muscle perfusion (4.07 +/- 0.44 vs. 5.18 +/- 0.36 ml. 100 g-1. min-1) were increased at hematocrit of 20%. Oxygen delivery to skeletal muscle was reduced to 74% of baseline values (0.64 +/- 0.06 vs. 0.48 +/- 0.03 ml O2. 100 g-1. min-1). Nevertheless, tissue PO2 was preserved (27.4 +/- 1.3 vs. 29.9 +/- 1. 4 Torr). Heterogeneity of muscle perfusion (relative dispersion) was reduced after ANH (20.0 +/- 2.2 vs. 13.9 +/- 1.5%). We conclude that a more homogeneous distribution of perfusion is one mechanism for the preservation of tissue oxygenation after moderate ANH, despite reduced oxygen delivery.