Measurement of Venous Flow by Continuous Thermodilution and its Application to Measurement of Mammary Blood Flow in the Goat

Abstract

Fegler showed in 1957 that the thermodilution method of measuring cardiac output 1 could be used also to measure the blood flow in the central veins of dogs. 2 Small quantities (0.4 to 1.0 ml) of saline at room temperature were rapidly injected through a three-holed needle into the vein, and the brief fall in temperature was recorded photographically from a thermocouple located 7 to 15 cm downstream. The blood flow was calculated from the concentration-time curve of the injected indicator ("cold"), the blood temperature and the temperature and volume of saline injected.The method was readily adapted to measure the venous flow from the udder of conscious goats, and with it were made the first direct measurements of mammary blood flow in conscious animals. These results agreed well with indirect estimates of blood flow calculated on the Fick principle from the transfer of plasma precursors into milk. 3 " 5 To ease the placement of the thermocouple and injection needles, and to reduce the chances of loss of indicator by heat exchange with the tissues, one mammary vein was exteriorized permanently as a skin covered loop, and was thus surrounded by air. Advantages of the method were chiefly that the injection and recording needles could be inserted and removed repeatedly for many months without disturbing the animal and without seriously damaging the exteriorized From the Agricultural Research Council, Institute of Animal Physiology, Babraham, Cambridge, England.Accepted for publication December 13, 1963. vessel, and since there was no recirculation of indicator and each response lasted about 5 sec, measurements could be made frequently. However, calculation of the flow from the area under each response was tedious and time consuming, and, although mean flow was fairly constant at a given stage of lactation (coefficient of variation 10% n ), single estimates could vary by as much as 50%, which may have been caused by extraneous factors influencing central venous pressure in the conscious animal.Modifications have been adopted to overcome these difficulties. Blood temperature is now recorded continuously on paper with a needle thermistor whilst saline is injected at a constant rate for 20 to 60 sec. The immediate measurement of the fall in blood temperature allows the flow to be calculated at once and the continuous record makes assessment of mean flow much easier. The validity of a constant rate infusion thermodilution method has been established in models in two laboratories, 0 -7 but not checked in vivo although Pavek, Boska and Selecky 7 showed that cardiac output can be measured by injecting cold saline for 6 to 10 sec into the right atrium and recording the fall of temperature in the pulmonary artery.The purpose of the present paper is to report that the technique has been further checked in vivo by three methods: 1) comparison with the single rapid injection technique, 2) comparison with mammary flow estimated on the Fick principle and 3) cannulation of the vessel and collection of blood in a measuring cylind...

Effect of Estradiol-17, β on the Magnitude and Distribution of Uterine Blood Flow in Nonpregnant, Oophorectomized Ewes

“…A recent report by Abrams et al [1] employing temperature changes in the vaginal mucosa as in index of changes in vaginal blood flow, suggests that the vasculature of this tissue responds to estrogens by vasodilation. Blood flow to the mammary gland has been determined previously in goats by the diffusion equilibrium method and by thermodilution [8,13]. It would appear that the effect of estrogens on mammary blood flow is severely blunted by stress.…”

The effect of very frequent milking and of oxytocin on the yield and composition of milk in fed and fasted goats

“…They were conducted on twelve Saanen and two Welsh goats in the animal house under conditions that caused the minimum of disturbance, generally with the animal in its own pen or on the milking stand (Linzell, 1966b). Some of the animals were surgically prepared for arterial and mammary venous blood sampling and for mammary blood flow measurement (Linzell,334 HOURLY MILKING IN FED AND FASTED GOATS 335 1960a, 1963, 1966a. Plastic catheters were inserted into arterial loops and/or into the right heart by Seldinger's (1953) technique under local anaesthesia and attached to a leather harness worn by the animal so that blood sampling and injections could be carried out with the minimum of restraint.…”

“…Volatile fatty acids were measured by the method of Annison (1954); free fatty acids by the method of Dole (1956), and amino acids by the method of Hamilton & Van Slyke (1943). Mammary blood flow was measured by the continuous thermodilution method of Linzell (1966a).…”

Local production of prostaglandins in relation to mammary function at the onset of lactation in the goat.

“…Measurements were usually made between 10.00 and 12.00 hr at 2-3 day intervals except near parturition when determinations were made more frequently and at various times of day. On each occasion mammary blood flow was determined by Linzell's (1960Linzell's ( , 1966 thermodilution technique. Arterial (7 ml.)…”