Noninvasive color Doppler sonography of uterine blood flow throughout pregnancy in sheep and goats.

In contrast to cattle or horses, uterine blood flow in small ruminants has been investigated predominantly after surgical intervention and chronic instrumentation. The objective of the present study was to investigate the clinical applicability of noninvasive color Doppler sonography to characterize blood flow in the maternal uterine artery of sheep, n = 11 (18 pregnancies) and goats, n = 11 (20 pregnancies). The following parameters were measured transrectally or transabdominally: blood flow volume, time-averaged maximum velocity (TAMV), resistance index (RI), pulsatility index (PI), Time-averaged mean velocity, impedance of blood flow (AB or systolic/diastolic [S/D] velocity ratio), peak velocity of blood flow and blood flow acceleration. Examinations started 2 weeks after breeding and continued at 2-week intervals until parturition. Outcomes for sheep and goats were similar and will be discussed together. Based on noninvasive color Doppler sonography, blood flow volume increased (approximately 60-fold, P < 0.0001) until the end of pregnancy, with a rapid increase early in gestation, and a slow increase after week 18. Time-averaged maximum velocity in the uterine artery increased (approximately 4-fold; P < 0.0001) throughout pregnancy in sheep and goats. Furthermore, for uterine artery blood flow, there was an effect of stage of pregnancy on PI and RI (P < 0.001 and P < 0.0001, respectively), both indices decreased until the end of gestation. Time-averaged mean velocity decreased from week 18 to 20 in both species. The blood flow acceleration increased (P < 0.0001) until week 16 and week 14 in sheep and goats, respectively, and then decreased until parturition. Similar to PI and RI, vascular impedance of the uterine decreased (P < 0.0001) throughout pregnancy. This is apparently the first study using noninvasive color Doppler sonography of uterine blood flow throughout physiological pregnancy in small ruminants. Clearly, this technology facilitates repeated, noninvasive assessments, with great potential for future studies.

Determination of plasma volume in anaesthetized piglets using the carbon monoxide (CO) method.

Based on measurements of the circulating red blood cell volume (V(RBC)) in seven anaesthetized piglets using carbon monoxide (CO) as a label, plasma volume (PV) was calculated for each animal. The increase in carboxyhaemoglobin (COHb) concentration following administration of a known amount of CO into a closed circuit re-breathing system was determined by diode-array spectrophotometry. Simultaneously measured haematocrit (HCT) and haemoglobin (Hb) values were used for PV calculation. The PV values were compared with simultaneously measured PVs determined using the Evans blue technique. Mean values (SD) for PV were 1708.6 (287.3)ml and 1738.7 (412.4)ml with the CO method and the Evans blue technique, respectively. Comparison of PVs determined with the two techniques demonstrated good correlation (r = 0.995). The mean difference between PV measurements was -29.9 ml and the limits of agreement (mean difference +/-2SD) were -289.1 ml and 229.3 ml. In conclusion, the CO method can be applied easily under general anaesthesia and controlled ventilation with a simple administration system. The agreement between the compared methods was satisfactory. Plasma volume determined with the CO method is safe, accurate and has no signs of major side effects.

A new method for measuring the blood volume of the rat using 113mIndium as a tracer.

A new method is described for the estimation of blood volume in the rat using 113mIndium chloride. No in vitro labelling step is necessary as the isotope binds specifically to transferrin in vivo. Under anaesthesia, an external jugular vein was cannulated for blood sampling and indium chloride injected directly into a lateral tail vein. Three blood samples of 0.2 ml were taken at short intervals and radioactivity measured under standard conditions. Blood volume was found to be 7.46 +/- 0.14 (mean +/- SEM) ml/100 g body weight. Repeating the study of 5 animals gave similar values for blood volume on the 2 occasions (7.23 +/- 0.26 and 6.95 +/- 0.23 ml/100 g, P > 0.05). The new technique was compared with established methods using 51Cr labelled red blood cells and 125Iodinated albumin. In each animal, the 113mIndium technique produced values approximately 10% higher than those obtained using the sum of plasma and red cell mass, in keeping with the known difference between whole body and large vein haematocrit (Indium, 7.20 +/- 0.19 and Iodine with Chromium, 6.40 +/- 0.34 ml/100 g). Data on blood volume determined using 125Iodine as the tracer on these same animals were identical (Indium, 7.20 +/- 0.19 and iodine, 7.16 +/- 0.34 ml/100 g). The method is simple to perform and appears to be at least as accurate and reproducible as established methods for measuring blood volume.

Plasma and extracellular volume in calves: comparison between isotopic and 'cold' techniques.

While isotopic techniques have largely superseded traditional markers for the determination of the volume of fluid compartments in vivo, they are not always convenient, especially with diarrhoeic animals. A direct comparison was therefore made in week-old calves between Evans blue and radio-iodinated serum albumin as measures of plasma volume and thiocyanate or 24sodium as measures of extracellular fluid space. The correlation coefficients were excellent (1.00, 0.96; P < 0.001) and the calves had plasma and extracellular fluid volumes of 72 +/- 2 and 438 +/- 2 ml kg-1, respectively. The latter value is, though high, typical of young animals and comparable with other data in calves.

Blood volume measurement in baboons: simultaneous estimation of red cell volume and plasma volume.

A method is described for frequent sequential blood volume estimation in baboons using 32P for red cell volume measurements and 125I-albumin for simultaneous plasma volume measurements. Values for red cell, plasma, and total blood volumes are reported. Close correlations of the volumes to bodyweight were demonstrated. Circulatory half-lives of the isotopes, determined from disappearance curves, confirmed their suitability for serial measurements in these baboons.

The ratio of cardiopulmonary blood volume to stroke volume as an index of cardiac function in horses.

A method was developed for determining the ratio of cardiopulmonary blood volume to stroke volume, in horses. The radioisotope 99 Tc (technetium 99m pertechnetate) was injected into the jugular vein as a bolus, which was then detected in the right and left ventricles consecutively by a scanning device consisting of a Na I crystal, a collimator, an amplifier and a discriminator. The radiocardiogram (RCG) and the ECG were recorded simultaneously by a two-channel writing device. The ratio of cardiopulmonary blood volume to stroke volume (cardiopulmonary flow index = CPFI) was then determined from the RCG and ECG tracings. Five categories of horses were examined, viz. Thoroughbreds in training, showjumpers in training, horses not in training, horses with cardiovascular disease and horses with chronic lung disease. The mean CPFI of the above categories were respectively 7.0 +/- 0.39, 7.3 +/- 0.45, 6.7 +/- 0.61, 9.8 +/- 1.30 and 6.2 +/- 0.47. The mean CPFI of the subjects with heart disease was significantly greater than the mean values of the other four categories (P less than 0.001). It was concluded that the CPFI was a reproducible physiological parameter in horses and that the value was significantly increased in our series of subjects with heart disease.

Survival of carrier erythrocytes in splenectomized calves.

Carrier erythrocyte survival was investigated in intact and splenectomized calves. Survival curves for both were biphasic, with a characteristic early loss of 10% to 15% of the carrier cells in intact calves followed by a half-life of 22 to 24 days. In splenectomized calves, 50% to 75% of the carrier cells disappeared from circulation in the first 24 hours. The 2nd phase of survival showed a 44-day half-life for the remaining carrier cells. Erythrocytes from splenectomized calves appeared to be permeable to [14C]sucrose and were more susceptible to irreversible hemolysis from the dialysis encapsulation procedure. Blood volume determination showed a 22% decrease after splenectomy.

Effects of the spleen, epinephrine, and splenectomy on determination of blood volume in cats.

Blood volume (BV), RBC mass, plasma protein (PP), and PCV were determined in (i) awake, nonsplenectomized (NSPX) cats before and after splenic contraction was induced by IV administration of epinephrine, (ii) in pentobarbital-anesthetized, NSPX cats before and after splenic contraction was induced by epinephrine and splenectomy, and (iii) in awake, splenectomized (SPX) cats before and after epinephrine was administered. Blood volume, absolute RBC mass in the spleen could not be determined accurately in awake or anesthetized, NSPX cats. Accurate BV and RBC mass determinations could only be obtained in cats without the spleen; mean BV and RBC mass of awake or anesthetized, SPX cats were 4.1% and 1.4% or body weight, respectively. The spleen was a dynamic sequestering organ for feline erythrocytes (RBC). Epinephrine (0.1 ml of 1:1,000) given IV resulted in the observed contraction of the spleen within 2 minutes. Relaxation of the spleen with RBC uptake began 3 minutes after epinephrine was given and it proceeded at a rate of approximately 0.93% of circulating PCV/min. At 20 minutes after epinephrine was given, a steady state of PCV occurred, and 20% of the maximum circulating PCV observed after the administration of epinephrine was stored within the spleen. At 60 minutes after epinephrine was given to awake, SPX cats, intravascular fluid influx of 4 ml/kg resulted in a decrease of PCV and PP. At 3 hours after splenectomy was done, intravascular fluid efflux resulted in hemoconcentration--a calculated fluid deficit of 2.5 ml/kg/hr occurring during the 3 hours after surgical removal of the spleen.

Blood volume of nonsplenectomized and splenectomized cats before and after acute hemorrhage.

Blood volume (BV) was determined in awake, nonsplenectomized (NSPX) and splenectomized (SPX) cats before and after hemorrhage (6 ml/kg). Each NSPX cat had a determined BV at least 10 ml/kg greater than the same cat after splenectomy. The mean BV of SPX cats was 43.4 +/- 8.94. ml kg (4.3% of body weight). The calculated RBC masses of NSPX and SPX cats were 17.0 +/- 4.07 and 12.2 +/- 1.12 ml/kg, respectively. Each NSPX cat had apparent RBC masses of 5 ml/kg greater than that of the same cat after splenectomy was done. At 1 hour after a hemorrhage, the BV and RBC masses determined in SPX cats were 46.7 +/- 12.1 and 9.7 +/- 1.90 ml/kg, respectively. Extravascular-to-intravascular fluid flux (calculated from RBC masses and plasma protein dilution) was approximately 0.80% of body weight. The indirect method with 51Cr-labeled RBC for BV determination was accurate and precise in awake, SPX cats; in awake, NSPX cats, the 51Cr-labeled RBC dilution method was precise, but not accurate. The spleen in the cat resulted in marked overestimations of BV and RBC masses.

Increases in circulating volumes and cardiac size with growth of White-tailed deer (Odocoileus virginianus).

Plasma and blood volumes determined by the T-1824 plasma-hematocrit method increase curvilinearly as captive female and male white-tailed deer (Odocoileus virginianus) grow in body mass from 6 to 61 kg (N = 40) and 9 to 93 kg (N = 34), respectively. Although comparable to other species of Cervidae, the weight-specific blood volume averages 33% larger than the interspecific mammalian value of 66 ml/kg body mass. The heart of white-tailed deer is also large, averaging 0.90% of the body mass (N = 53), about twice the ratio reported for domesticated ungulates. The cardiovascular demands attendant with a tenfold increase of body mass are apparently met by rapid increases in cardiac size (both mass and left intraventricular volume increasing curvilinearly with growth) and minute volume of the cardiac pump (cardiac rate and volume ejected per beat, inversely related to the other), which maintain fewer circulations of blood volume per minute with growth to heavier body size occurring from June to November.

Direct and reflex effects of nitroglycerin on the blood volume distribution, evaluated by regional weighing in the cat.

The effects of nitroglycerin on the blood volume distribution were studied with a method of regional weighing in the anaesthetized cat. An i.v. bolus injection of nitroglycerin produced a dose-dependent decrease in arterial pressure accompanying a decrease in the thoracic blood volume. The latter change was associated with blood volume increases principally in the abdomen, and slightly in the hindquarters. Elimination of the cardiovascular reflex effects by carotid sinus denervation and cervical vagotomy signficantly enhanced and prolonged the following changes: the hypotension, the decrease in thoracic blood volume and the volume pooling in the abdomen. The magnitude of increase in hindquarters blood volume was not significantly affected by the denervation procedures, but the duration was much prolonged. The results indicate that the major site of nitroglycerin-induced venous pooling is in the splanchnic circulation. The peripheral venous pooling is produced at the expense of a decrease in the central or pulmonary blood volume. The secondary reflex adjustments tend to minimize the direct effects of nitroglycerin on the blood pressure and blood volume distribution.