Blue Dye Dilution Technique Research Articles

Relationship between body composition, blood volume and maximal oxygen uptake.

It has long been known that body mass and, more specifically, lean body mass are strongly correlated with maximal oxygen uptake (VO2max) in man and animals. However, there are no data to date describing this phenomenon in the horse. The purpose of this paper is to examine the relationship between body composition and VO2max in the horse. Twenty-three healthy and unfit Standardbred mares performed an incremental exercise test (GXT) to measure VO2max. Rump fat thickness (RTH), a measure of fat covering, was measured using B-mode ultrasound. Plasma volume, total blood volume and red cell volume were determined, using the Evan's Blue dye dilution technique and packed cell volume. VO2max was correlated with body mass (r = 0.541; P<0.01) and exercise haematocrit (exHCT; r = 0.407; P<0.05) but not RTH or the other haematological variables. To eliminate the influence of body mass on the individual variables, a regression analysis was performed on the mass-residuals of VO2max, RTH, plasma volume and exHCT. The residuals of VO2max were correlated negatively with the residuals of RTH (r = -0.687; P = 0.0003) and positively with the residuals of exHCT (r = 0.422; P = 0.045) but not plasma volume. VO2max could be predicted from a linear combination of the residuals of RTH and exHCT (r = 0.767; P<0.0001). These data indicate that VO2max in the horse is significantly related to fat-free mass (FFM), independent of body mass. Red blood cells from the splenic reserve constitute an important factor in the horse's ability to achieve a high VO2max. Therefore, lean body mass may be a more appropriate basis for assessing metabolic function in the athletic horse.

Changes in circulating blood and plasma volume after hemoglobin-based oxygen carrier infusion and additional infusion of colloid solutions.

The aim of this study was to investigate the changes in circulating blood volume (CBV) after infusions of Hemoglobin glutamer-200 (bovine; Hb-200) in combination with 6% hetastarch in an animal model of acute posthemorrhagic anemia. Fifteen rabbits with a mean body weight of 2.2 +/- 0.2 kg were studied. After determination of the circulating plasma volume (CPV) and CBV, one third of the CBV was withdrawn via an arterial catheter. An equal volume of Hb-200 was then infused in the 5 animals in study group 1. In the remaining 10 animals, the same volume of 6% hetastarch solution was infused. Fifteen minutes after completion of the infusion, an additional infusion of 6% hetastarch at a dose equal to one third of the baseline CBV was performed in study group 1 and the control group. In study group 2, equal volumes of Hb-200 were infused. CPV measurements were performed at baseline, after hemorrhage, 5 and 15 minutes after volume replacement, and 1 and 15 minutes after hypervolemic hemodilution using the Evans blue dye dilution technique. The mean baseline CPV value was 53.4 +/- 1.1 mL/kg. The mean CBV at baseline was 90.8 +/- 4.9 mL/kg. After one third of the CBV was withdrawn, no differences in CBV or CPV were observed between the three groups. Replacement of one third of the CBV with Hb-200 significantly increased the CPV (73.7 +/- 1.8 mL/kg) when compared with the baseline level (53.5 +/- 1.8 mL/kg; n = 5; P < 0.05). The difference between the groups was first observed 15 minutes after infusion. CPV was significantly higher in study group 1 (87.0 +/- 2.2 mL/kg) compared with the other groups (80.2 +/- 2.6 mL/kg in the control group and 79.5 +/- 3.6 mL/kg in study group 2). After a second transfusion, the differences between the groups became more prominent. Study group 2 demonstrated the highest CPV and CBV. The two study groups demonstrated a statistically significant increase in circulating volumes compared with the control group. The magnitude of this difference was lower than expected based on in vitro colloid osmotic pressure measurements.

Physiological or Functional Fluid Spaces

Physiological or Functional Fluid Spaces

Clinical effects of thigh cuffs during a 7-day 6° head-down bed rest

Thigh cuffs are used by Russian cosmonauts to limit the fluid shift induced by space flight. A ground simulation using the head-down bed rest (HDBR) model was performed to assess the effects of thigh cuffs on clinical tolerance and orthostatic adaptation. 8 male healthy volunteers (32.4±1.9 years) participated twice in a 7-day HDBR — one time with thigh cuffs (worm daily from 9 am to 7 pm) (TC) and one time without (WTC). Orthostatic tolerance was assessed by a 10 minute stand test and by a LBNP test (5 min at −15, −30, −45 mmHg) before (BDC-1) and at the end of the HDBR period (R+1). Plasma volume was measured before and at the end of HDBR by the Evans blue dye dilution technique. Thigh cuffs limits headache due to fluid shift, as well as the loss in plasma volume (TC: −5.85±0.95%; WTC: −9.09±0.82%, p<0.05). The mean duration of the stand test (R+1) did not differ in the two group (TC 7.1±1.3 min; WTC 7.0±1.0 min). The increase in HR and decrease in diastolic blood pressure were slightly but significantly larger without thigh cuffs. Duration of the LBNP tests did not differ with thigh cuffs. Thigh cuffs limit the symptoms due to fluid shift and the loss in plasma volume. They partly reduced the increase in HR during orthostatic stress but had no effect on duration of orthostatic stress tests.

A novel approach to measuring circulating blood volume: the use of a hemoglobin-based oxygen carrier in a rabbit model.

Hemoglobin-based oxygen carriers (HBOC) may be ideal for monitoring circulating plasma volume (CV-P) and circulating blood volume (CV-B). We used an HBOC (Hemoglobin glutamer-200 [bovine], Oxyglobin; Biopure, Cambridge, MA) as an indicator for relative CV-B in the rabbit model. Accuracy of the technique was determined by comparison with the Evans blue dye (EBD) dilution technique in 19 anesthetized female New Zealand rabbits weighing 2.0 to 10.6 kg. The measurements were performed at baseline, after hemorrhage (1/3 of CV-B), normovolemic hemodilution (replacement of 1/3 CV-B by Hextend; Abbot Laboratories, North Chicago, IL), and hypervolemic hemodilution (additional infusion of Hextend(R) in a volume equal to 1/3 of CV-B). Hemoglobin concentration was measured by using a HemoCue photometer (HemoCue AB, Angelholm, Sweden). EBD concentration was analyzed by using linear regression to estimate Time 0 concentration; Time 0 was defined as EBD injection time. The difference between CV-P values determined by EBD and HBOC dilution was independent from the magnitude of the CV-P value. The relative bias was 1.29 mL, and the precision (one SD) was 2.82 mL. The difference did not reach statistical significance. Circulating plasma and blood volumes can be accurately estimated by plasma hemoglobin concentration measurements by using hemoglobin-based oxygen carrier infusion.

High dose angiotensin-converting enzyme inhibition prevents fluid volume expansion in heart transplant recipients

OBJECTIVESWe sought to test the hypothesis that plasma volume (PV) expansion in heart transplant recipients (HTRs) is caused by failure to reflexively suppress the renin-angiotensin-aldosterone (RAA) axis.BACKGROUNDExtracellular fluid volume expansion occurs in clinically stable HTRs who become hypertensive. We have previously demonstrated that the RAA axis is not reflexively suppressed by a hypervolemic stimulus in HTRs.METHODSPlasma volume and fluid regulatory hormones were measured in eight HTRs (57 ± 6 years old) both before and after treatment with captopril (225 mg/day). Antihypertensive and diuretic agents were discontinued 10 days before. The HTRs were admitted to the Clinical Research Center (CRC), and, after three days of a constant diet containing 87 mEq/day of Na+, PV was measured by using the modified Evans blue dye dilution technique. After approximately four months (16 ± 5 weeks), the same HTRs again discontinued all antihypertensive and diuretic agents; they were progressed to a captopril dose of 75 mg three times per day over 14 days, and the CRC protocol was repeated.RESULTSCaptopril pharmacologically suppressed (p < 0.05) supine rest levels of angiotensin II (−65%) and aldosterone (−75%). The reductions in vasopressin and atrial natriuretic peptide levels after captopril did not reach statistical significance. The PV, normalized for body weight (ml/kg), was significantly reduced by 12% when the HTRs received captopril.CONCLUSIONSExtracellular fluid volume is expanded (12%) in clinically stable HTRs who become hypertensive. Pharmacologic suppression of the RAA axis with high-dose captopril (225 mg/day) returned HTRs to a normovolemic state. These findings indicate that fluid retention is partly engendered by a failure to reflexively suppress the RAA axis when HTRs become hypervolemic.

Cardiac Output Responses During Exercise in Volume-Expanded Heart Transplant Recipients

The mechanisms responsible for immediate adjustments in cardiac output at onset of exercise, in the absence of neural drive, are not well defined in heart transplant (HT) recipients. Seven male HT recipients (mean ± SD 57 ± 6 years) and 7 age-matched sedentary normal control subjects (mean age 57 ± 5 years) performed constant load cycle exercise at 40% of peak power output (Watts). Cardiac output and plasma norepinephrine were determined at rest and every 30 seconds during the first 5 minutes of exercise and at minutes 6, 8, and 10. All subjects were admitted to the General Clinical Research Center for determination of plasma volume. After 3 days of equilibration to a controlled and standardized diet, plasma volume was measured using a modified Evans Blue Dye (T-1824) dilution technique. Heart rate at rest was higher in the HT group (105 ± 12 vs 74 ± 6 beats/min), but during submaximum exercise, heart rates in the control group increased more rapidly (p ≤0.05) and to a greater magnitude (54 ± 7% vs 17 ± 4% above rest). Stroke volume at rest was lower in HT recipients (45 ± 4 vs 68 ± 9 ml) but was significantly augmented immediately after onset of exercise (30 seconds) and the relative increase was greater than controls at peak exercise (61% vs 38% greater than baseline). Cardiac output at rest was within the normal range in both groups (4.58 ± 0.27 vs 4.94 ± 0.40 L/min). Relative increases in cardiac output were similar (p ≥0.05) for the HT (106 ± 12%) and control groups (97 ± 10%). Plasma norepinephrine did not become significantly greater than resting values until approximately 4 minutes after onset of exercise in both groups. Blood volume, normalized for body weight, was 12% greater in the HT group. Thus, HT recipients with expanded blood volume (12%) augment stroke volume immediately after the onset of exercise. Plasma norepinephrine levels contribute negligibly to the rapid adjustment in cardiac output. Rather, we speculate that abrupt on-transit increases in stroke volume are due to augmented venous return, secondary to expanded blood volume.

Blood volume and diving ability of the New Zealand sea lion, Phocarctos hookeri.

We test the hypothesis that the New Zealand sea lion is physiologically better equipped for prolonged, continuous diving than other otariids (fur seals and sea lions) by measuring its blood volume, an important component of its oxygen storage. Mass, hematocrit, and plasma volume were measured and blood volume calculations were completed on 14 adult females and five juvenile females. Plasma volume was determined using the Evans blue dye dilution technique. Mean plasma volume for all subjects was 74 mL kg(-1). Mass-specific plasma volume was significantly higher in adult females (15.3%) than in juveniles (14.6%). Blood volume (150 mL kg(-1)) and hematocrit (51%) were not significantly different between adults and juveniles. The aerobic dive limit can be estimated by dividing the animal's oxygen stores by its metabolic rate. The estimated aerobic dive limit for adult animals was between 5.5 and 7.8 min, depending on the assumed metabolic rate. New Zealand sea lions have the highest blood volume yet reported for an otariid, which supports the hypothesis that they have a physiological capability suited to their unique diving behavior.

DECREASED PLASMA AND BLOOD VOLUME IN PATIENTS WITH CHRONIC HEART FAILURE1533

Intravascular fluid volume expansion is an acute compensatory adaptation in patients (pts) with chronic heart failure (CHF). Data are lacking on the long-term influence of diuretics and ACE-inhibitors on fluid volume in CHF pts. The purpose was to determine the effect of standard CHF pharmacotherapy on plasma volume (PV) and blood volume (BV). PV and BV were measured in 12 CHF pts (62.1±7.1 yrs; 175.2±6.8 cm; 96.2±18.2 kg) with ischemic disease (LVEF<50%; NYHA II/III) and 7 healthy controls (CON)(71.7±5.3 yrs; 177.1±10.8 cm; 84.4±11.7 kg) 3-4 hrs post-prandial and 20 min after supine rest using the Evans Blue Dye dilution technique. Venous blood samples were collected pre-Blue dye infusion and analyzed for hematocrit (Hct) (corrected 4% for trapped plasma and venous to whole body Hct ratio) and hemoglobin (Hb). Hct was 36.6±3.5 and 37.4±1.1% (p>0.05) and Hb was 15.4±1.9 and 16.2±1.4 g/dl (p>0.05) for CHF and CON, respectively. Absolute PV was 3489.3±655.0 and 3728.7±813.2 ml (p>0.05) and absolute BV was 5469.8±1025.4 and 5942.4±1182.2 ml (p>0.05), for CHF and CON, respectively. Relative PV was 34.1±12.9 v. 44.5±9.0 ml/kg(p≤0.05) and relative BV was 58.5±12.3 v. 70.8±12.6 ml/kg(p≤0.05), in CHF and CON, respectively. These data suggest that standard pharmacotherapy, including, diuretics and ACE-inhibitors, may contract PV and BV in CHF pts.

Haematocrit, plasma volume and noradrenaline in humans during simulated weightlessness for 42 days.

Previous results from our laboratory demonstrate that changes in haematocrit (Hct) and haemoglobin concentration (Hb) underestimate the relative (%) change in plasma volume (PV) in seated subjects during simulation of weightlessness by water immersion. Therefore, we examined whether changes in Hct and Hb would accurately reflect the changes in PV in seven subjects during simulation of weightlessness by another model, 6 degrees head-down tilted bed rest (HDBR), for 42 days. Since we have previously observed unexpectedly high plasma levels of noradrenaline (NA) in astronauts during space flight, we also took the opportunity to measure this variable. The measurements were compared with those of the supine horizontal position before and after HDBR. During HDBR, PV measured by the Evans blue dye dilution technique decreased by 6.1 +/- 2.8% (P < 0.05) on day 2 and 9.6 +/- 2.2% (P < 0.05) on the 42nd day compared with that of the supine, horizontal position. Based on changes in Hct and Hb, PV decreased similarly by 8.3 +/- 2.8 and 10.2 +/- 3.2% (P < 0.05) respectively. There were no differences comparing the results of the two methods (P > 0.05). Forearm venous plasma NA was unchanged during the whole course of HDBR compared with that of the pre-HDBR supine position. It is concluded that changes in Hct and Hb reliably reflect the changes in PV comparing prolonged HDBR with the pre- and post-HDBR horizontal, supine position. Thus, changes in Hct and Hb might accurately reflect the change in PV during weightlessness in humans provided that the horizontal supine position is used as the ground-based reference. Furthermore, the results of this study, as well as of previous studies from space, confirm that NA release is unchanged or even increased during weightlessness.

Heart rate and blood lactate responses to submaximal treadmill exercise in the normally performing standardbred trotter--age and sex variations and predictability from the total red blood cell volume.

The purposes of this study were to elucidate the influences of age and sex on the heart rate (HR, bpm) and blood lactate (LA, mmol/l) related exercise tolerance parameters V2000 (tread ill velocity at HR 200), VLA4 (velocity at LA 4), W200 (power output at V2000), and WLA4 (power output at VLA4), and to establish reference values for these in normally performing Standardbred trotting race horses. A further aim was to improve the predictability of individual normal values by correlating them with the total red blood cell volume (CV) alone or in combination with the blood lactate response at V200 (LA200). In total 205 horses were included in the study. According to their owners and/or trainers they were all performing satisfactorily (in racing or training) for shortly impending racing. The exercise test was performed on an inclined (3.5 degrees) high speed treadmill and consisted of four sequentially increasing speeds, each of 2 min duration, aiming at a final HR at or exceeding 200 bpm. HR was monitored continuously and recorded in parallel with blood sampling during the last 15 s of each speed. Blood volume determination was done with the Evans blue dye dilution technique immediately after the exercise test to ensure complete emptying of the splenic red cell reservoir. Both age and sex influenced significantly on all parameters. These were also all strongly dependent on the total red cell volume. Consequently, it was concluded that markers for work tolerance based on heart rate and blood lactate responses to submaximal treadmill exercise reliably reflect circulatory and muscle metabolic capacities. Further, individual normal values are predictable from the red cell volume alone with variation coefficients between 5 and 9.1%, or, in combination with LA200, between 4.4 and 62%. Disregarding the regression with CV, predictability of normal values is improved by considering age and sex variations.

Blood volume in the hemoglobinless Antarctic teleost Chionodraco hamatus (Lönnberg)

AbstractBlood volume in the hemoglobinless Antarctic icefish Chionodraco hamatus (Channichthyidae) has been determined by the Evans blue dye dilution technique. A mean blood volume of 127.0 ± 5.0 ml kg−1 body weight was found, a value even higher than that previously found in another icefish, Chaenocephalus aceratus (mean blood volume, 89.7 ml kg−1 body weight; Hemmingsen and Douglas [1970] Comp. Biochem. Physiol., 33:733–744; Twelves [1972] Br. Antarct. Surv. Bull. 37:85–92). This extraordinary hypervolemia appears unique among teleosts and may compensate for the absence of hemoglobin in the icefish. © 1995 Wiley‐Liss, Inc.

Heart and spleen mass related to blood parameter changes after epinephrine injection

SummaryThe purpose of this study was to determine if splenic weight is correlated to changes in blood volume, haematocrit and haemoglobin concentration after epinephrine injection in horses. Ten mares, 5 racing type and 5 draft type, all over age 5 years were studied. Differences in plasma volume (PV), red cell volume (RCV), total blood volume (TBV) and venous haematocrit (PCV) were maximised by xylazine and epinephrine treatments to either sequester or mobilise the splenic RCV. Plasma volume was determined using an Evans Blue Dye (EBD) dilution technique, then used to calculate TBV and RCV. Horses were killed by captive bolt gun and exsanguination, and heart (HW) and spleen weights (SW) were recorded and expressed as a percentage of body weight (BW). Significant differences between breed types were found for changes in RCV and PCV between treatments. Analysis of variance found significant differences between breed types in HW/BW and SW/BW ratios. Regression analysis demonstrated a positive relationship between the change in RCV between treatments and SW/BW with significant differences (P &lt; 0.01) between breed types in this relationship. There was no relationship between changes in RCV or PCV and HW/BW.

The effects of sodium bicarbonate administered nasogastrically on plasma volume, electrolytes and blood gases in resting quarter horses

The purpose of this study was to investigate the effect of a single dose (1000 mg/kg of body weight) of sodium bicarbonate (NaHC03) on plasma volume, pH, HC03 concentration, and serum Na, Cl, K, and Ca levels. Eight Quarter Horse mares, ranging in age from 5 to 15 years, were paired into four groups and used in a four-period crossover experiment. Each pair of horses was randomly assigned each week to one of four treatments: H20 only (A), NaHC03 with H20 (B), no NaHC03 with no H20 (C), and NaHC03 without H20 (D). Plasma volumes were determined by using an Evan's Blue Dye dilution technique. Mean plasma volume was 16.01, and no significant difference (p > 0.05) was found between treatments. Blood gases and pH were determined before and six hours after NaHC03 administration. Analysis of variance found that treatments B and D significantly (p > 0.01) affected levels of pH, pC02, P02, HC03, Na, Cl, Ca and K compared to both treatments A and C.

Repeated plasma volume determination with the Evans Blue dye dilution technique: The method and a computer program

This paper describes a reliable multiple sample Evans Blue dye dilution technique and a Pascal program which computes plasma and blood volume on the basis of this technique. The program performs needed corrections and dye disappearance curve fitting. It provides menudriven facilities for data correction, graphic display of the dye disappearance curve, and print-out of all the involved data. Means±S.E.M. for three plasma volume determinations in each of six resting subjects were: 3239±96 ml, 3189±81 ml, and 3187±102 ml. The differences were not statistically significant.

Altered baroreflex function after tail suspension in the conscious rat

Experiments were performed on conscious chronically instrumented rats to determine the contribution of peripheral V2-vasopressinergic receptors in any alteration of baroreceptor reflex (BRR) sensitivity on release from 1 wk of 30 degrees head-down tilt resulting from tail suspension. Initial experiments determined changes in plasma volume (PV) occurring over this period by use of the Evans Blue dye dilution technique. PV was determined immediately before tail suspension and on day 7 of the stimulus. PV, erythrocyte volume, and total blood volume were all significantly diminished on day 7, whereas hematocrit was unchanged. Other rats were instrumented with pulsed Doppler flow probes on the ascending aorta for determination of cardiac output and with arterial and venous catheters 7-10 days before study. Immediately before tail suspension, control cardiac output, mean arterial blood pressure, and heart rate values were determined. In addition, BRR sensitivity was estimated both before and after intravenous administration of a V2-receptor antagonist by assessing the slope of the pulse interval-mean arterial blood pressure relationship in response to a series of pressor doses of phenylephrine. BRR sensitivity was determined on the last day of head-down tilt, 1 min after release from tail suspension, and 10 min after administration of a specific V2-vasopressinergic antagonist. BRR sensitivity tended to fall on day 7 of tail suspension compared with control and was significantly increased after release. However, BRR sensitivity was not altered by intravenous V2 antagonist administration either before tail suspension or after release.(ABSTRACT TRUNCATED AT 250 WORDS)

Time course of blood volume change with carbon monoxide inhalation and its contribution to the overall cardiovascular response.

Adult male Sprague-Dawley rats inhaled 500 ppm CO continuously for 42 days in order to examine the blood volume response in a time course manner. Plasma volume as measured by Evan's blue dye dilution technique did not change significantly from the control value of 3.96% of body weight (BW). Total blood volume estimated using plasma volume and hematocrit increased steadily from 7.34% of BW to 11.69%, almost entirely as the result of a more than 2-fold increase in erythrocyte mass (3.42% increased to 7.55%). Absolute blood volume increased from 28.51 ml to 58.26 ml; normal growth contributed to this increase, i.e. BW increased from 350.0 g to 499.1 g. "Real hematocrit" determined by dye dilution increased from 46.5% to 64.6%, reaching a near-equilibrium level within 15 days. Hemoglobin concentration increased from 13.68 g/dl to 20.07 g/dl, and erythrocyte count increased from 6,150,000 per cubic mm to 9,140,000 per cubic mm. Minor changes in erythrocyte indices (i.e. mean corpuscular hemoglobin concentration and mean corpuscular volume) occurred during the 42 days. Concurrently, the weight of right ventricle increased more than left ventricle + septum, reflecting somewhat greater right-sided cardiomegaly. Increases in both ventricles were correlated with changes in blood volume and hematocrit. Plasma atrial natriuretic peptide activity increased 2.5 fold after 15 and 30 days of CO exposure, possibly reflecting increasing atrial stretch caused by increased blood volume. Like the polycythemic hypervolemic state of chronic hypoxic hypoxia, blood volume in CO hypoxia increases solely through addition of erythrocytes.

Plasma Volume Determination in Normal and Preeclamptic Pregnancies

To determine the clinical usefulness of plasma volume determinations, we measured plasma volume serially throughout pregnancy with the use of the Evans blue dye-dilution technique in 20 subjects with normal pregnancies. In comparison, four preeclamptic subjects were studied. In preeclamptic subjects compared to normal subjects, plasma volume was reduced (1763 ± 216 versus 2345 ± 198 ml/m2, p < 0.011). Two normotensive subjects who subsequently developed preeclampsia had reduced plasma volumes prior to the onset of hypertension as compared to volumes in those who remained normotensive (1918 ± 86 versus 2345 ± 198 ml/m2, p < 0.01). Those subjects who were delivered of infants who were small for gestational age had significantly reduced plasma volumes compared to volumes of those who were delivered of infants who were appropriate for gestational age (1950 ± 333 versus 2237 ± 259 ml/m2, p < 0.05), but this was true only among gravid women with pregnancies complicated by preeclampsia. We conclude that failure of plasma volume expansion is associated with the development of preeclampsia and also intrauterine fetal growth retardation in preeclamptic subjects.

Plasma volume in normal pregnant Nigerian primigravidae

Plasma volume was measured in 10 non-pregnant, healthy nulliparous Nigerian and 30 normal primigravid Nigerians at various times of gestation by the Evans blue dye dilution technique. The mean plasma volume of 2098 ml for the non-pregnant Nigerians was statistically different (P < 0.001) from values in non-pregnant caucasian primigravidae of comparable status. A mean maximum plasma volume increase of 1387 ml above non-pregnant value was found. Essentially, pregnancy imposed a much higher physiological load on Nigerian primigravidae compared to caucasian primigravidae. There was a significant negative correlation between plasma volume and packed cell volume (PCV) in pregnancy (r = −0.51, P < 0.001), which may be related to excessive hemodilution in the primigravid Nigerian. Differences found may be due to geographical and/or racial factors.

Plasma volume determination in normal and preeclamptic pregnancies

To determine the clinical usefulness of plasma volume determinations, we measured plasma volume serially throughout pregnancy with the use of the Evans blue dye-dilution technique in 20 subjects with normal pregnancies. In comparison, four preeclamptic subjects were studied. In preeclamptic subjects compared to normal subjects, plasma volume was reduced (1763 ± 216 versus 2345 ± 198 ml/m2, p < 0.011). Two normotensive subjects who subsequently developed preeclampsia had reduced plasma volumes prior to the onset of hypertension as compared to volumes in those who remained normotensive (1918 ± 86 versus 2345 ± 198 ml/m2, p < 0.01). Those subjects who were delivered of infants who were small for gestational age had significantly reduced plasma volumes compared to volumes of those who were delivered of infants who were appropriate for gestational age (1950 ± 333 versus 2237 ± 259 ml/m2, p < 0.05), but this was true only among gravid women with pregnancies complicated by preeclampsia. We conclude that failure of plasma volume expansion is associated with the development of preeclampsia and also intrauterine fetal growth retardation in preeclamptic subjects.