Product Details

The colloid osmotic pressure (COP) is a special case of osmosis. COP appears at semipermeable membranes which are well permeable for water and substances with molecular weights up to several thousands, but are impermeable for colloids, e.g. plasma proteins. Wilhelm PFEFFER first described osmotic phenomena in plant cells (1877). He measured them with the first osmometer. Jacobus Hendricus VAN'T HOFF described them theoretically (1887). Ernest H. STARLING, the great physiologist, discovered the phenomenon of colloid osmotic pressure and its important role in balancing the capillary transmural fluid exchange (1896). lt was Starling who built the first colloid osmometer with a peritoneal membrane, and he used it for the first direct measurement of colloid osmotic pressure in canine serum. Measurement then took three to four days. COP is indeed the “antagonist” of the intra-capillary hydrostatic pressure, both being equally important for the interstitial fluid balance. But until recently, COP could not be measured in clinical diagnosis because there were no colloid osmometers available, simple and sturdy enough for the routine. The new ONKOMETER BMT 923 is unsurpassed in simplicity of both measurement and maintenance. Measurement takes less than two minutes, and the device automatically holds the right steady state value of the displayed COP. The ONKOMETER BMT 923 is sturdy and simple for use in the clinical practice.

COP of capillary blood has to be judged in reference to the hydrostatic blood pressure in these capillaries and in the neighbouring venoles, to the hydrostatic pressure in the surrounding interstitial spaces, and to the COP of the interstitial fluid. Both of the latter can hardly be measured. Nevertheless the knowledge of blood COP, and its trend, gives indications of high clinical significance, e.g. • how to get aware of pulmonary edema in statu nascendi • when to start IV infusion of plasma protein solutions • when to stop it • when protein infusion is contraindicated • what happens with high molecular IV solutions after infusion • how to avoid superfluous infusion of protein solutions • how to monitor COP in extracorporeal circulation with the heart lung machine • how to manage colloid balance in peritoneal dialysis • how to anticipate EPH gestoses and pre-eclampsia in gynecology • how to anticipate cerebral edema in neuro-surgery COP is correlated statistically with plasma protein concentration, physiologically and even in intensive care patients. But this correlation needs not necessarily be valid for the individual patient. Correlation may fail totally for the critically ill, e.g. for burn victims. When COP is normal, IV infusion of protein solutions may be the wrong therapy, even if the patient’s plasma protein concentration is low. This is true especially when COP cannot be improved by infusion of protein solutions. In intensive care medicine, albumen therapy should always be accompanied by COP measurement of the patient’s blood. Avoiding superfluous IV infusion of expensive plasma protein solutions, however, can redeem purchase of a colloid osmometer within a short time. Since routine measurement of COP has become available only recently, it is a true paradox that a basic physiologic parameter can still be investigated by pioneers. The ONKOMETER BMT 923 is the right tool for them.