Continuous Blood Sampling Research Articles

Assessment of Growth Hormone Secretion: What Are We Looking for Practically?

GH is a dominant factor in determining growth during childhood. Hence, the assessment of GH secretion is of major importance in the diagnosis of growth disorders. Since GH is secreted in a pulsatile fashion, a truly accurate production rate can only be calculated by using very frequent or continuous blood sampling over a 24-hour period. Several standard provocative tests have been established to evaluate GH secretory status. They remain the cornerstone in the assessment. Recent data have shown the existence of a wide spectrum of GH secretory disturbances ranging from severe GH deficiency to partial insufficiency and neurosecretory dysfunction. There is no well-defined cut-off point at which a particular child can be regarded as GH insufficient or sufficient for optimal growth. In clinical practice, the assessment of GH secretion starts with the careful analysis of the growth chart and height velocity. Careful clinical examination of the patient is essential for the proper diagnosis, and to exclude diseases influencing GH secretion. Additional biochemical tests may be required for the differential diagnosis. Thus, assessment of GH secretion in children requires auxological, clinical and biochemical data. GH insufficiency is documented by additional testing of pituitary secretory capacity either by standard provocative tests, by studying 24-hour GH profile or by measuring 24-hour production rate. The main goal is to detect those children who will benefit from treatment with hGH. The final assessment might consist in the response of growth velocity to exogenous hGH.

Scintigraphic method to quantify the passage from brain parenchyma to the deep cervical lymph nodes in rats

In order to investigate the kinetics of the passage from the brain parenchyma to the lymphatic system in vivo a high resolution scintillation camera technique was developed. Albumin, albumin colloids and dextran labelled with 99mTc were injected into the right side of the thalamus of anesthetized rats. Continuous measurement of the activity distribution in head and neck were performed for 70 min. Rate constants were calculated by means of a computer program for compartment analysis. The animals were killed 10 h postinjection, to measure the activity in tissue samples. For some animals, images were registered up to 24 h after injection. This work presents an in vivo technique to clarify the particle flow paths in the brain and make quantification possible. The method is simple and does not require continuous blood or lymph sampling. Our work shows that there is a substantial flow of injected material from the brain via lamina cribriformis to the lymphatic system. This route is of great interest for the drainage of the interstitial fluid of the brain. We have also shown a difference in flow for dextran particles with different charge.

Fetal Distress and the Condition of the Newborn Using Cardiotocography and Fetal Blood Analysis During Labour

The efficacy of electronic fetal monitoring combined with fetal blood analysis during labour in identifying fetal distress was investigated in a retrospective study. Operative delivery for fetal distress diagnosed during labour was performed in 9% of 2659 deliveries. All had continuous fetal heart rate monitoring and 22% had a fetal scalp blood analysis. Operative delivery had been performed in 53% of the infants who were acidotic at birth (umbilical artery pH less than 7.20) and in 46% of those with a low modified Apgar score (less than 7). These results show that the use of continuous fetal heart rate monitoring and fetal scalp blood sampling detects fetal distress without resulting in a high rate of operative delivery.

Fetal Distress and the Condition of the Newborn Using Cardiotocography and Fetal Blood Analysis during Labour

The efficacy of electronic fetal monitoring combined with fetal blood analysis during labour in identifying fetal distress was investigated in a retrospective study. Operative delivery for fetal distress diagnosed during labour was performed in 9% of 2659 deliveries. All had continuous fetal heart rate monitoring and 22% had a fetal scalp blood analysis. Operative delivery had been performed in 53% of the infants who were acidotic at birth (umbilical artery pH less than 7.20) and in 46% of those with a low modified Apgar score (less than 7). These results show that the use of continuous fetal heart rate monitoring and fetal scalp blood sampling detects fetal distress without resulting in a high rate of operative delivery.

Nocturnal plasma prolactin and cortisol levels in epileptics with complex partial seizures and primary generalized seizures.

The nocturnal pattern of plasma prolactin (PRL) and cortisol in male epileptics with complex partial seizures and primary generalized seizures was studied by all-night polygraphic recordings with continuous video monitoring and sequential blood sampling at 30-minute intervals. Mean nocturnal plasma PRL concentrations in both groups of epileptics were significantly elevated when compared with nonepileptic control subjects studied in a similar fashion. Eight subclinical and three clinical partial seizures were recorded during sleep. Although a tenfold increase of plasma PRL level occurred following a short brief clinical complex partial seizure, there was no direct correlation between single subclinical partial seizures and nocturnal fluctuations of plasma PRL concentrations. We did not observe recognizable plasma cortisol changes following partial seizures during sleep, nor significant differences of mean nocturnal plasma cortisol levels between epileptics and controls. The data obtained in this environmentally controlled study indicate that postictal elevation of plasma PRL is a specific phenomenon related to seizure discharges; however, failure of such a rise does not exclude partial seizures.

Continuous fiberoptic arterial oxygen tension measurements in dogs.

An experimental study using a new fiberoptic sensor for the continuous intraarterial measurement of oxygen tension is described. This "optode" sensor uses the phenomenon of fluorescence quenching to determine the oxygen tension of the surrounding medium. To assess the accuracy of this device, we anesthetized 4 dogs and monitored them continuously with arterial catheters and an intraarterial optode probe, and intermittently with arterial blood gas analysis. The inspired oxygen fraction was varied from 1.0 to 0.1, and arterial blood gases were measured for comparison with the optode reading. Two hundred ninety data sets yielded a correlation coefficient of 0.96, with a linear regression slope of 0.98 and intercept of 5.1 mm Hg. In the 72 data sets from the last dog, the bias and precision of the optode arterial oxygen tension values were -10.3 mm Hg and 20.0 mm Hg, respectively. The optode probe was easily inserted through a 20-gauge catheter and did not interfere with continuous arterial pressure measurement or blood sampling. This study suggests that the optode has great potential as a continuous, real-time monitor of arterial oxygen tension.

Fetal distress and the condition of the newborn using cardiotocography and fetal blood analysis during labour.

The efficacy of electronic fetal monitoring combined with fetal blood analysis during labour in identifying fetal distress was investigated in a retrospective study. Operative delivery for fetal distress diagnosed during labour was performed in 9% of 2659 deliveries. All had continuous fetal heart rate monitoring and 22% had a fetal scalp blood analysis. Operative delivery had been performed in 53% of the infants who were acidotic at birth (umbilical artery pH less than 7.20) and in 46% of those with a low modified Apgar score (less than 7). These results show that the use of continuous fetal heart rate monitoring and fetal scalp blood sampling detects fetal distress without resulting in a high rate of operative delivery.

Plasma concentrations of luteinizing hormone and progesterone during superovulation of dairy cows using follicle stimulating hormone or pregnant mare serum gonadotrophin

Eighteen lactating Holstein cows were randomly divided into three groups of equal size. Six cows were not superovulated; the remaining cows were superovulated using either FSH-P or PMSG beginning on Day 12 of the estrous cycle (day of ovulation = Day 0). Animals treated with FSH-P were injected intramuscularly (i.m.) with 4 mg FSH-P every 12 h for 5 d. PMSG was administered i.m. as a single injection of 2350 IU. Cloprostenol (PG, 500 ug) was injected i.m. 56 and 72 h after commencement of treatment and at the same time in the cycle of controls. All cows were inseminated 56, 68 and 80 h after the first PG injection. Blood samples (5 ml) were collected daily and every 15 min for a period of 9 h on Days −1, 0, 2, 8 and 10, with continuous blood sampling at 15-min intervals during Days 3 to 6. Ovulation rate was 27.7 ± 8.22 in animals treated with PMSG, and 8.0 ± 3.2 embryos per donor were recovered. In the FSH group, ovulation rate was 8.3 ± 1.48 and 3.0 ± 1.1 embryos per donor were recovered. Progesterone concentrations were similar in all three groups until the onset of the LH surge, when progesterone concentrations were greater (P<0.05) in animals of the PMSG group. After the preovulatory LH surge, concentrations of progesterone started increasing earlier (44 h) in cows treated with PMSG, followed by FSH-treated cows (76 h) and controls (99 h). The LH surge occurred earlier (P<0.05) in PMSG-treated cows (37 h after first PG treatment), than in animals treated with FSH-P (52 h) or controls (82 h). In animals treated with FSH-P, the magnitude of the preovulatory LH surge (24.2 ± 1.02 ng/ml) was higher (P<0.05) than in the other two groups (PMSG = 17.1 ± 2.04 ng/ml; control, 16.7 ± 1.24 ng/ml). Superovulation with FSH-P or PMSG did not affect either mean basal LH concentration, frequency or amplitude of LH pulses during Days −1, 0, 2, 3, presurge periods, or Days 8 and 10 post-treatment. At ovariectomy, 8 d post-estrus, more follicles > 10 mm diam. were observed in the ovaries after treatment with PMSG (8.5 ± 5.66) than after treatment with FSH-P (0.7 ± 0.42) (P<0.05). Maximum concentrations of PMSG were measured 24 h after administration. Following this peak, PMSG levels declined with two slopes, with half-lives of 36 h and 370 h.

Nocturnal plasma prolactin rise in patients with complex partial seizures.

We measured plasma prolactin and cortisol concentrations in 12 epileptic men with complex partial seizures during all-night polygraphic recording, with continuous video monitoring and sequential blood sampling at 30-minute intervals. There was a significant but moderate elevation of all-night mean plasma prolactin concentration (p less than 0.001), but not of cortisol, in epileptics when compared with normal subjects studied in a similar fashion. The data obtained in this environmentally controlled study of males with complex partial seizure disorder indicate a disruption of prolactin regulatory mechanisms resulting in a modest elevation of plasma concentrations independent of ictal electrographic discharges.

Intrapartum fetal surveillance: The role of fetal scalp blood sampling

Continuous electronic fetal heart rate monitoring and fetal scalp blood sampling have traditionally played a complementary role in intrapartum fetal surveillance. Nevertheless, biochemical assessment of fetal blood pH, with the use of scalp or umbilical cord blood, is often viewed as the “gold standard” against which biophysical indicators of fetal distress must be judged. In actual clinical practice, however, fetal scalp blood sampling is only rerely used. In addition, there is a growing body of evidence to suggest that, when properly interpreted, fetal heart rate assessment may be equal or superior to measurement of fetal blood pH in the prediction of both good and bad fetal outcomes. Under certain circumstances, fetal scalp blood sampling remains a valuable clinical tool; however, we recommend a deemphasis of fetal scalp blood sampling in general clinical practice. Both theoretical and practical considerations suggest that the properly trained clinician may pursue an approach for the detection of fetal distress that does not include scalp blood sampling without either compromising his ability to detect fetal distress or significantly increasing the cesarean section rate.

Method for Automatic, Continuous Blood Sampling with Remote Alarm for Clogged Catheters

An inexpensive blood sampling system is described that includes a remote alarm triggered by a decrease in rate of blood withdrawal. Additional modifications include design of a reliable sampling catheter and of a method for quickly and atraumatically replacing clogged catheters. This system has been used to collect continuous, integrated blood samples every 15min for up to 72h from cows. The alarm system is also useful for monitoring any flow in which minimum rate is critical, e.g., for column chromatography.

EFFECTS OF WATER AVAILABILITY ON PLASMA PROTEIN AND SODIUM CONCENTRATION, HAEMATOCRIT AND PLASMA OSMOLALITY IN THE PIG

Eighteen young growing pigs of the Large White breed were housed in individual pens or metabolism stands and habituated to drinking their water from a bowl. Those housed in the metabolism stands were surgically fitted with a catheter placed in he jugular vein to allow collection of blood samples. The voluntary intake of water after periods of progressively increasing water deprivation was measured. The measurements were made by allowing the pigs to drink to satiety after either a 2, 4, 8, 12 or 18 h period of water deprivation. Voluntary water intake was a function of the duration of water withdrawal and the rate of intake increased with progressive deprivation. Changes in plasma concentration of sodium and protein, haematocrit and osmolality could be detected after 12 and 18 h of dehydration. The progressive changes in plasma sodium concentration ([Na+]), osmolality, protein concentration and haematocrit during adaptation to dehydration when water was withheld for 72 h were examined in six pigs. Using a technique of continuous blood sampling, the rapid changes in the same blood parameters during rehydration, when water was made freely available at the end of the 72 h period, were also monitored. The [Na+] and osmolality dropped precipitously following the onset of drinking. From the 15 min stage to the 4 h stage with water available ad libitum, the values of both parameters remained below their control levels. However, the plasma protein concentration and the haematocrit values remained significantly above their pre-dehydration control levels up to the 4 h stage, even with water freely available, thus showing that drinking stopped even though the extracellular fluid phase remained dehydrated. Only with food available did the blood measures return to normal. It is concluded that the cellular fluid phase forms an integral part of the mechanisms involved in the termination of drinking in the pig.

Clinical application of serum insulin-like growth factor I (IGF-I)(26-46) radioimmunoassay--with special reference to the relationship between IGF(26-46) and growth hormone secretion

Serum insulin-like growth factor I(IGF-I)(26-46) levels were determined in normal children aged 0-16y(n = 111), adults(n = 11), and various diseased conditions. In order to elucidate a mutual relationship between IGF-I(26-46) and growth hormone (GH) secretion, the following correlations were evaluated: 1) a correlation between IGF-I(26-46) and basal GH level (n = 57), 2) a correlation between IGF-I(26-46) and GH level responding to the insulin tolerance test (ITT) (n = 30), 3) a correlation between IGF-I(26-46) and an integrated concentration of GH(ICGH) in the early sleep stage (n = 24). In addition, the following correlations between GH level with ITT and ICGH in the early sleep stage(n = 20) and between IGF-I(26-46) and an integrated concentration of prolactin (ICPRL) in the early sleep (n = 20) and overnight sleep (n = 7) stages were also examined. IGF-I(26-46) was measured according to the method of Yanaihara with minor modifications. Samples for ICGH were collected every 30 min until 4 hours after sleep by a portable continuous flow blood withdrawal pump(CORMED, MODEL ML6) at a rate of 6 ml/h. Samples for ICPRL from 13 subjects were collected by the same procedure and period as ICGH. On the other hand, samples for ICPRL from 7 subjects were collected during an overnight period. Sleep and wake cycles were almost identical in the subjects tested. Among the subjects tested with ITT and continuous blood sampling for ICGH and ICPRL, patients with pituitary dwarfism were excluded. Serum IGF-I(26-46) levels appeared to be age-dependent, and the highest value was demonstrated in puberty. Some children under 8 years of age showed serum IGF-I(26-46) levels as low as that of pituitary dwarfism. No sexual difference was noticed in IGF-I(26-46) levels. Serum IGF-I(26-46) levels in pituitary dwarfism were apparently low and significantly increased after hGH injection. Serum IGF-I(26-46) levels in patients under 11 years of age with constitutional dwarfism and Turner's syndrome revealed an almost normal result. However, many patients over 11 years of age showed lower levels of serum IGF-I(26-46) than normal subjects, and some cases showed remarkably low levels of serum IGF-I(26-46). Serum IGF-I(26-46) levels in precocious puberty without treatment were slightly high in comparison with age-matched controls.(ABSTRACT TRUNCATED AT 400 WORDS)

Dissociated patterns of nocturnal prolactin, cortisol, and growth hormone secretion after stroke.

The secretory activity of the hypothalamic-pituitary axis is influenced by suprahypothalamic regulatory mechanisms. To evaluate the effect of brain lesions on hormonal patterns, we investigated eight patients convalescing from hemispheric stroke and five sex- and age-matched healthy volunteers. Studies were conducted during two consecutive nights with continuous polygraphic recording and sequential blood sampling. Nocturnal plasma hormone measurements showed a normal rhythm of cortisol (a marker of ACTH), elevated prolactin concentrations (p less than 0.05) and low growth hormone values (p less than 0.05). The study suggests that major suprahypothalamic lesions influence hypothalamic function so as to facilitate prolactin secretion and inhibit growth hormone release. They have no effect on the more basic pattern of ACTH-cortisol secretion, however.

Superovulatory responses in FSH- or pergonal-treated heifers

Eighteen lactating Holstein cows were randomly divided into three groups of equal size. Six cows were not superovulated; the remaining cows were superovulated using either FSH-P or PMSG beginning on Day 12 of the estrous cycle (day of ovulation = Day 0). Animals treated with FSH-P were injected intramuscularly (i.m.) with 4 mg FSH-P every 12 h for 5 d. PMSG was administered i.m. as a single injection of 2350 IU. Cloprostenol (PG, 500 ug) was injected i.m. 56 and 72 h after commencement of treatment and at the same time in the cycle of controls. All cows were inseminated 56, 68 and 80 h after the first PG injection. Blood samples (5 ml) were collected daily and every 15 min for a period of 9 h on Days −1, 0, 2, 8 and 10, with continuous blood sampling at 15-min intervals during Days 3 to 6. Ovulation rate was 27.7 ± 8.22 in animals treated with PMSG, and 8.0 ± 3.2 embryos per donor were recovered. In the FSH group, ovulation rate was 8.3 ± 1.48 and 3.0 ± 1.1 embryos per donor were recovered. Progesterone concentrations were similar in all three groups until the onset of the LH surge, when progesterone concentrations were greater (P<0.05) in animals of the PMSG group. After the preovulatory LH surge, concentrations of progesterone started increasing earlier (44 h) in cows treated with PMSG, followed by FSH-treated cows (76 h) and controls (99 h). The LH surge occurred earlier (P<0.05) in PMSG-treated cows (37 h after first PG treatment), than in animals treated with FSH-P (52 h) or controls (82 h). In animals treated with FSH-P, the magnitude of the preovulatory LH surge (24.2 ± 1.02 ng/ml) was higher (P<0.05) than in the other two groups (PMSG = 17.1 ± 2.04 ng/ml; control, 16.7 ± 1.24 ng/ml). Superovulation with FSH-P or PMSG did not affect either mean basal LH concentration, frequency or amplitude of LH pulses during Days −1, 0, 2, 3, presurge periods, or Days 8 and 10 post-treatment. At ovariectomy, 8 d post-estrus, more follicles > 10 mm diam. were observed in the ovaries after treatment with PMSG (8.5 ± 5.66) than after treatment with FSH-P (0.7 ± 0.42) (P<0.05). Maximum concentrations of PMSG were measured 24 h after administration. Following this peak, PMSG levels declined with two slopes, with half-lives of 36 h and 370 h.

Characterization of cephalic arteriovenous LH differences by continuous sampling in ovariectomized sheep.

Blood from the external carotid artery and from the external jugular vein were collected simultaneously, and luteinizing hormone (LH) concentrations were measured in order to determine the temporal pattern of the large episodic pulses of LH secretion which are characteristic of ovariectomized sheep. Collection of paired arterial and venous samples at 5-min intervals did not provide adequate resolution of arteriovenous LH changes which accompany these pulses. Therefore, a continuous blood sampling system was developed which permitted collection of paired and venous samples over 20-second intervals throughout a sampling period of approximately 45 min. One large pulse of LH secretion was detected in 6 of 9 trials, and each pulse was characterized by a brief period (2-6 min) when venous concentrations of LH were much higher than corresponding arterial concentrations. Periods of considerable release of LH from the head were usually followed by a period when arterial LH levels were greater than the venous levels, indicating that LH was being removed from the circulation by the tissues of the head. Administration of synthetic GnRH pulses (17.5-35 ng) through the arterial cannulae of halothane-anesthetized ewes produced in different trials arteriovenous LH concentration differences ranging from no discharge of LH to discharges much larger and more prolonged than those occurring spontaneously in conscious ewes. These results suggest that individual episodes of spontaneous pulsatile discharge of LH in ovariectomized sheep last 2-6 min and probably result from episodic secretion of LH-releasing hormone by the hypothalamus. Profiles of circulating LH also appear to be modified by extravascular sequestration of LH.

The role of a trial of labor with a positive contraction stress test

During a 28 month period 812 patients underwent antepartum FHR testing. Twenty-eight patients had a positive CST. There were two antepartum fetal deaths and 11 patients had a cesarean section without a trial of labor. Fifteen patients had a trial of closely monitored labor (continuous FHR and fetal scalp blood sampling when indicated) and 11 of these (73%) were delivered vaginally. The CST records were examined for: per cent late deceleration, baseline FHR, presence of FHR accelerations, duration of the latency period (time from onset of contraction to onset of deceleration), and amplitude of deceleration. The absence of accelerations (nonreactive CST) and a latency period of less than 45 seconds both predicted persistent late deceleration during labor or fetal death in utero but statistical significance was found only for the latter parameter.

Monitoring of the dilution rate during continuous in vivo blood sampling with a double lumen catheter

A simple and non-destructive method for monitoring the dilution rate during continuous blood sampling is described. When the dilution rate is not constant, the proposed method based on electrical resistivity measurement provides a correction factor for further analysis.

Collection of blood from the pituitary stalk and portal veins in monkeys, and from the pituitary sinusoidal system of monkey and man.

A transorbital, transsphenoidal microsurgical approach to the pituitary stalk and gland was used to collect blood from the hypothalamo-hypophyseal portal system in monkeys. Specimens may be obtained from the entire pituitary stalk, individual long portal veins, or the pituitary sinusoidal bed, with little risk of mortality. Continuous stalk blood sampling was carried out for periods of up to 10 hours. Pituitary sinusoidal-system blood was also collected during transsphenoidal surgery in man. The uses of data concerning hypothalamic-hypophyseal regulation obtained by these methods are illustrated.

High density lipoprotein catabolism before and after partial hepatectomy

The serum decay and tissue distribution of iodine-labeled high density lipoprotein HDL)-apoproteins were measured in rats 2 2 h after partial hepatectomy or sham-operation. A method was developed allowing continuous bloodsampling without using anticoagulantia or anaesthetics. The serum decay of HDL-apoproteins was biexponential. Neither the initial rapid phase ( t sol1 2 0.3 ± 0.1 h), nor the slow phase ( t 1 2 6.2 ± 0.3 h) were influenced by the removal of sol2 3 of the liver and consequently there was no effect on the fractional catabolic rate (F.C.R.: 2.9 ± 0.2/day). The level of circulating HDL was decreased by partial hepatectomy but the chemical composition of HDL was unchanged. Total tissue HDL radioactivity in the control rats was 5.7, 2.8, 2.7, 1.0, 0.7, 0.2, 0.4 and 0.1% of the injected dose for skeletal muscle, adipose tissue, liver, jejunum, kidneys, spleen, lungs and heart, respectively. Only the value for liver was affected significantly by partial hepatectomy (0.6%). It is concluded that the in vivo degradation rate of HDL-apoproteins is not influenced by the removal of sol2 3 of the liver and that the decrease in serum HDL concentration is due to an impaired rate of hepatic synthesis. These results indicate the possibility of extrahepatic HDL-apoprotein catabolism or a stimulation of HDL-apoprotein degradation, induced by partial hepatectomy, in the remaining liver lobes.