Heart rate variability and electrocardiogram changes in the fetal lamb during hypoxia and beta-adrenoceptor stimulation

Hypoxic changes in the ST waveform of the fetal electrocardiogram (FECG), with elevated T waves as the main response, have earlier been described in the fetal lamb as mediated via the beta-adrenoceptor cells, initiated by catecholamine release. A similar background to the increase in fetal heart rate variability (FHRV) during hypoxemia has been suggested. The aim of the present study was to elucidate this question and also to compare FHRV and changes in the ST waveform of the FECG as indicators of fetal distress. Twenty-six acutely exteriorized mature lamb fetuses were submitted to periods of graded hypoxemia. Fetal blood gases were measured and oxygen content was calculated. The FHRV was analyzed by a computer program and calculated as the differential index (DI) and the interval index (II). Eighty seconds of the recorded ECG coinciding in time with each fetal blood sample were analyzed using a PDP 11/40 minicomputer. The ECG signal was sampled at a rate of 1250 samples per second giving a resolution in time of 0.8 msec. Each QRS complex was detected with a semi-automatic program using a cross-correlation algorithm. QRS complexes that by the program were signalled to be doubtful were visually examined and either rejected or approved. Hence, the resulting list of R-R intervals was practically free from artefacts. From this list of R-R intervals the DI and II were computed according to YEH et al. [30]. Hypoxemia resulted in initially strongly increased DI from 3.1 +/- 2.5 to 17.7 +/- 13.8 (p less than 0.001) and in II from 1.88 +/- 0.65 to 3.77 +/- 2.06 (p less than 0.001) (Fig. 1). Obviously the change in oxygen content per se was strongly associated with the variability indices, as we found a strong correlation between delta oxygen content/min and delta DI/min (r = 0.81). In five fetuses the effect of prolonged hypoxemia on DI was studied (Fig. 2). After the initial rise from 1.6 +/- 1.1 to 31.2 /+- 9.0 (p less than 0.02) DI decreased to 19.4 +/- 20.7. A regression analysis showed a strong connection between DI and PaO2, (n = 93, T = - 5.34), whether there was no relation between DI and pH (T = - 1.85). There is strong evidence that hypoxemia and asphyxia induce an increase in the concentration of catecholamines in fetal blood [2, 23].(ABSTRACT TRUNCATED AT 400 WORDS)

Treatment of intrauterine supraventricular tachycardia with digoxin and verapamil

Intrauterine fetal supraventricular tachycardia (ISVT) is a rare condition which is connected with organic heart disease in only 4-10 per cent. However, neonatally these children develop heart failure in a high frequency (62 per cent). Intrauterine digitalization has been suggested as treatment, especially if the fetus is preterm. Fetal therapeutic concentrations might demand doses inconvenient to the mother. We hereby report one case of intrauterine SVT in the 26th gestational week treated with a standard dose of digoxin resulting in subtherapeutic umbilical digoxin levels. When no consistent influence on fetal heart rate could be seen, verapamil (80 mg x 3) was added to the treatment. A reversion of the tachycardia and the fetal ECG changes was achieved within two days. The verapamil treatment could be withdrawn after ten days, while the digoxin treatment was continued. An initial discrete heart enlargement also was reversed by the treatment. The delivery in gestational week 38 was uneventful and the child did well. A neonatal ECG showed a sinus rythm interfoliated with supraventricular extrasystoles. No signs of organic heart disease have appeared. When last seen at nine months of age, the ECG was normal and digoxin had been discontinued without recurrence of tachycardia.

Acute haemodynamic effects of pindolol during pregnancy in experimental renal hypertension

Clinical as well as experimental studies have demonstrated a 70% reduction in utero-placental blood flow in pregnancies affected by severe hypertension (13, 19). In pregnant renal hypertensive rats, propranolol administration causes a further 50% reduction in utero-placental blood flow (16). The present study on renal hypertensive rats was performed in order to explore the acute effects on central haemodynamics and utero-placental blood flow of the non-selective beta-blocker pindolol, which also has an intrinsic beta-stimulatory effect. Renal hypertension was induced by partial clamping of both renal arteries in female Wistar rats 4 weeks before pregnancy. Some 2-4 days before expected parturition, cardiac output was determined with the dye-dilution technique and blood flow to the reproductive organs with the microsphere technique, both before and after acute pindolol administration. Mean arterial pressure and heart rate were recorded continuously during the experiment. After pindolol injection, mean arterial pressure fell by 22% due to a 38% reduction in total peripheral resistance. No significant changes in cardiac output, stroke volume or heart rate were found. Placental blood flow was significantly reduced, by 30%, whereas myometrial and ovarian blood flows were reduced by only 18 and 9%, respectively. Thus, the reduction in blood supply to the reproductive organs in renal hypertensive rats after acute pindolol administration was most pronounced in the placenta. This reduction in placental flow was, however, only about half as pronounced as after propranolol, which lacks intrinsic beta-stimulatory effects. This may suggest that vasodilating beta-receptors may play an important role in the maternal placental vascular bed.

Fibrinopeptide A and intravascular coagulation in normotensive and hypertensive pregnancy and parturition

Fibrinopeptide A (FpA), fibrin monomers, fibrinogen, fibrin degradation products (FDP) aand platelets have been studied during pregnancy, parturition and during toxemia and compared with normal non-pregnant controls in order to evaluate thrombin activity under these conditions. We found a significant rise in fibrinopeptide A levels in late pregnancy and even more so during parturition with a maximum immediately after placental expulsion. We also found elevated FpA levels in toxemic patients, but no significant differences from normal pregnancies. Fibrin monomers were more often elevated during delivery and toxemia during normal pregnancy. One case report concerning a patient with deficient thrombin activation and heavy postpartum bleeding is added. Our studies indicate an increased thrombin activity and fibrinogen turnover in both normal and toxemic pregnancies. During normal childbirth, coagulation activity seemed to reach a maximum immediately after placental separation.

The acute effects of a non-selective beta-adrenergic blocking agent in hypertensive pregnant rats

It is generally accepted that hypertensive cardiovascular complications can be prevented by treatment. However, during pregnancy, antihypertensive drugs might be hazardous in view of their influence on the fetus. Nevertheless, in spite of the diverging published results, even beta-blockers have been used in the pregnant patient. As our basic knowledge concerning the circulatory and fetal effects is minimal, we decided to elucidate the influence of the non-selective beta-blocker, propranolol, on the haemodynamic circumstances in hypertensive pregnant rats. Renal hypertension was induced by clamping both renal arteries 4 weeks before pregnancy. Shortly before term, cardiac output was determined with the dye-dilution technique and utero-placental blood flow was determined with the microsphere technique, both before and after propranolol injection. Mean arterial pressure and heart rate were registered continuously. The acute propranolol injection reduced mean arterial pressure by 26%. This was due mainly to a 32% decrease in cardiac output, which in turn was due to a 24% decrease in stroke volume and a 6% decrease in heart rate. Both myometrial and placental blood flow decreased significantly, by 45 and 50%, respectively. It was furthermore of interest to observe the significant increase in blood flow resistance in both myometrium and placenta. In conclusion, it can be stated that the non-selective beta-blocker propranolol, which lacks intrinsic stimulating activity, reduces mean arterial pressure mainly by a cardiac output decrease. The present results further indicate that the influence on peripheral blood flow might be caused by cardiac output changes as well as by direct effects on the uteroplacental vascular bed.

Maternal beta-adrenoceptor blockade reduces fetal tolerance to asphyxia. A study in pregnant sheep

Maternal and fetal beta 1-adrenoceptor blockade was induced in sheep by infusing i.v. 11 pregnant ewes with metoprolol in doses producing maternal plasma concentrations of metoprolol comparable to those obtained in clinical use. Ten other ewes and their fetuses served as controls. Under acute anaesthesia the fetus was exteriorized and subjected to two levels of controlled asphyxia by intermittent, complete obstruction of the maternal placental blood flow. Fetal haemodynamic reactions were assessed by measuring fetal heart rate, cardiac contractility, cardiac output and cerebral blood flow. The metabolic reactions were evaluated from blood gases, pH, lactate and hypoxanthine concentrations, while the electrophysiological status of the brain was evaluated from the somatosensory evoked EEG potentials (SEP). Already during the period of moderate asphyxia the beta-blocked fetuses demonstrated a blunted haemodynamic response, in comparison with the control fetuses, resulting in an accelerating lactic acidosis, signs of a breakdown of intra-cellular energy-rich phosphates and an impaired cerebral function. During the period of severe asphyxia, both groups of fetuses exhibited signs of extensive cerebral deterioration. During the ensuing recovery phase, 80% of the control fetuses regained their brain function, as assessed by SEP, whereas this was true for only 30% of the beta 1-blocked fetuses. It is concluded that the ovine fetus relies heavily on greatly increased sympatho-adrenal activity to adapt itself to asphyxia and that blockade of the fetal beta 1-adrenoreceptors by maternal medication is a hazard to the potentially asphyctic fetus.

A clinical comparison between a laboratory and a commercial impedance audiometer

Impedance audiometry is a useful tool in the diagnosis of retrocochlear lesions, provided that adequate normal values regarding the stapedius reflex thresholds and decay are used. The normal values in Sweden (and elsewhere) have been obtained with a laboratory impedance audiometer that is not in common use. We have compared a commercial impedance audiometer, the Grason-Stadler 1723, with this laboratory model to determine whether the normal values are valid. We found that the Grason-Stadler 1723 audiometer gives reliable stapedius reflex thresholds, but at 2-4 dB higher levels. The reflex decay curves, however, are unsatisfactory. Possible explanations for the results are discussed. We have also proposed a modification of the recorder of the commercial audiometer. The study demonstrates that normal values cannot be transferred freely between different equipments.

Contribution of heart muscle, liver, skeletal muscle and placenta to the asphyxial hypoxanthine elevation in the acutely exteriorised fetal lamb

The metabolic response to different degrees of hypoxia was studied in 14 lamb fetuses. We have previously found a substantial rise in the fetal arterial plasma hypoxanthine (HX) level, in parallel with alterations of other hypoxia indices during induced asphyxia. Measurements of the arterio-venous (A-V) difference in the HX level across the CNS demonstrated a late efflux of this substance from the fetal brain, with a high resistance to asphyxia. In this study, the effluxes of HX, lactate, and in some cases glucose, from the myocardium, liver, hindleg (skeletal muscle) and placenta were investigated in acutely exteriorised sheep fetuses with graded asphyxia. The main findings were as follows: (a) myocardium: a release of HX early during asphyxia, the magnitude of which paralelled the amount of mechanical work performed by the heart; a significant lactate influx into the heart during normoxia and recovery period; (b) liver: hepatic HX release even during normoxia, increasing to substantial amounts in connection with increasing asphyxia; (c) hindleg: release of HX only during the recovery period; lactate efflux during all periods apart from severe asphyxia, when an influx was seen for both substances; (d) placenta: production of lactate during normoxia, and an efficient clearance of both lactate and HX from the fetal plasma in combination with their concentration increasing during asphyxia. It is concluded that the myocardium and liver are the main contributors to the elevated HX level during fetal asphyxia among the fetal organs investigated, while skeletal muscle releases HX mostly during the period of reoxygenation.

Hemodynamic changes after chronic pindolol administration in pregnant renal hypertensive rats

The aim of the present study on pregnant renal hypertensive rats was to investigate the effects on central hemodynamics and uteroplacental blood flow after chronic administration of pindolol, a nonspecific beta-adrenergic receptor blocking agent with intrinsic beta-stimulatory effect. Renal hypertension was induced by partial clamping of both renal arteries four weeks before pregnancy. Pindolol was administered with the food during the entire pregnancy period. Two to four days before expected delivery mean arterial pressure, heart rate, cardiac output, (dye-dilution technique) and utero-placental blood supply (microsphere technique) were determined. The chronic pindolol treatment reduced heart rate by 25 per cent while both mean arterial pressure and cardiac output remained unchanged. However, blood flow to uterus and placentae was reduced by 43 and 64 per cent, respectively, after pindolol treatment. Clinical as well as experimental studies (15, 16) demonstrate a reduced utero-placental blood supply when pregnancies are complicated by hypertension. As pregnancies with severe hypertension are associated with an increased frequency of intrauterine growth retardation and intrauterine asphyxia the present results indicate that the combination of hypertension and long-term treatment with beta-blockers might reduce utero-placental blood flow enough as to seriously interfere with fetal oxygen supply thereby increasing the risk of intra- and extra-uterine asphyxia.

The effect of pregnancy on heart size and blood pressure in renal hypertensive rats

The main purpose of this study on rats was to examine the effect of pregnancy on experimental renal hypertension and cardiac size. Renal hypertension in the rats (RHR) was induced by standardized clamping of the left renal artery early in pregnancy (SRHR) or 4 weeks before mating (ERHR). As controls served non-pregnant RHR with the duration of hypertension matched to each above mentioned group, as well as non-pregnant and pregnant normotensive rats. Only 16% of the rats with renal artery clamping early in pregnancy (SRHR) developed hypertension in contrast to 41% of similarly operated non-pregnant rats and 56% of ERHR decreased their blood pressure to normal levels during pregnancy. Concerning left ventricular heart weight there was a slight increase in left ventricular weight during normal pregnancy in spite of a significantly reduced blood pressure. In both SRHR and ERHR an increased left ventricular heart weight was noticed during pregnancy even when arterial pressure was not increased. The present results suggest an antihypertensive effect of pregnancy and the existence of "trophic" influences and/or a volume induced adaptation of the heart causing an increased myocardial mass which is associated with pregnancy and partly independent of blood pressure influences.

Sound levels recorded within the symphony orchestra and risk criteria for hearing loss

Investigations into noise-induced hearing loss should consist of two parts: a mapping of the sound environment and a charting of hearing loss. This paper is the first part of such an investigation: a mapping of sound levels and sound spectra within the symphony orchestra. It was found that 'heavy' symphonic music exceeds the permitted dose for industrial noise equivalent to 85 dB(A) for a full working week. The permitted noise dose is reached for 'heavy' music after a working time of 10 hours per week in 'exposed' positions, such as in front of trumpets, and after 25 hours in 'normal' positions. A simple method to estimate the 'noise' exposure in equivalent sound level for combination of different sorts of music has been developed.

The hearing of symphony orchestra musicians

The question has recently been raised as to whether the performance of symphony orchestra music involves a risk of sustaining hearing impairment. The following investigation presents a population study of 417 musicians, of whom 123 were investigated twice, at an interval of 6 years. Median values of screened tone thresholds were compared with a reference material, according to Spoor & Passchier-Vermeer (1969). The tone thresholds measured did not differ from the reference values although the actual sound exposure in some situations exceeded the permitted sound levels applied to industrial noise. We suggest that the sound exposure criteria for industrial noise are not valid when discussing such sounds as are produced by acoustic instruments in a symphonic environment.

Cardiac output in normal pregnancy measured by impedance cardiography

Impedance cardiography was used to study cardiodynamic changes throughout normal pregnancy. Stroke volume, heart rate and cardiac output were determined in fourteen normal primigravidae from early pregnancy until 6-25 weeks after delivery. To elucidate the influence of the patient's position on cardiac output, measurements were made in the supine as well as in the left and right lateral positions. Stroke volume and cardiac output increased up to the 28th week of pregnancy and then decreased during late pregnancy. These changes seemed to be independent of the patient's position. After delivery a further reduction in cardiac output due to a significant decrease in heart rate was found. No significant differences in cardiac output were found between right and left lateral position. However, during pregnancy as well as after delivery, cardiac output measured by impedance cardiography was significantly higher in the supine position than in the lateral positions. Thus, the impedance method does not seem to be reliable in measuring absolute values of stroke volume and cardiac output but may be used for relative measurements during pregnancy.

Metabolic studies in women with previous gestational diabetes during contraceptive treatment: effects on serum lipids and high density lipoproteins

Triglycerides, cholesterol and phospholipids in serum and high density lipoproteins (HDL) were assessed in 11 women with previous gestational diabetes before and repeatedly during 6 months of low dose progestogen (lynoestrenol = LYN) contraceptive administration. Eight of these women also were followed in an identical manner during non-hormonal contraception (IUD) and 6 of them during combined oral contraceptive administration (EE + LYN). During the use of IUD or LYN administration neither serum nor HDL lipids changed. The combined OC, EE + LYN, increased serum triglycerides progressively: 73% (P less than 0.01) after 6 months concomitant with a 100%-increment of HDL triglycerides (P less than 0.01) HDL-cholesterol and -phospholipids were not consistently changed. The EE + LYN induced alterations differed from the effects of LYN alone (P less than 0.01). During the use of IUD or LYN administration neither serum nor HDL lipids changed. The combined OC, EE + LYN, increased serum triglycerides progressively: 73% (P less than 0.01) after 6 months concomitant with a 100%-increment of HDL triglycerides (P less than 0.01). HDL-cholesterol and -phospholipids were not consistently changed. The EE + LYN induced alterations differed from the effects of LYN alone (P less than 0.01). These results suggest that low dose progestogens, such as LYN, could be considered as contraceptive alternatives in women with gestational diabetes. However, combined OC should be avoided in these patients. The present findings differ from those obtained in insulin-dependent diabetics and suggest that a diabetic prediposition enhances the effects of synthetic oestrogens and/or diminishes some of the effects of progestogens on lipid metabolism.

A scoring system for antenatal identification of fetal growth retardation

A scoring system for selection of pregnancies at risk of intrauterine growth retardation (IUGR) is presented. It is based on eight weighted items which include information from previous pregnancies and from the current one including the increment of fundal height and of maternal weight. With a risk population of 7% all IUGR infants were included. The IUGR infants constituted 34% of the risk group.

Cerebral arterio-venous difference for hypoxanthine and lactate during graded asphyxia in the fetal lamb

Hypoxanthine (HX) and lactate are degradation products from energy-rich intracellular substrates (ATP and glycogen), and their concentration will increase during anaerobic conditions, such as fetal asphyxia. In this study the accumulation of the two metabolites in blood during asphyxia was studied in 7 acutely exteriorized fetal lambs. The arterio-venous difference of HX and lactate over the brain was related to the function of the fetal brain as reflected by the somato-sensory evoked electroencephalogram potentials (SEP). Increased concentrations of HX in plasma and lactate in blood occurred simultaneously with deterioration of the SEP and the 3 variables correlate highly significantly. During normoxia, a net cerebral influx was found for HX, which in combination with severe asphyxia gradually changed to a net efflux. A linear correlation was found between the cerebral arterio-venous differences of HX and the impairment of the SEP. No such correlation existed for lactate. The results suggest, that the fetal brain has a high threshold for degrading its energy-rich intracellular purines.

Immuno-histochemical localization of myoglobin in human muscle tissue and embryonal and alveolar rhabdomyosarcoma

An immuno-histochemical investigation of the presence and localization of myoglobin was performed on cardiac and skeletal muscle tissue and on 9 embryonal and 9 alveolar rhabdomyosarcomas, utilizing an immunoperoxidase technique. Cardiac muscle fibres were evenly stained whereas staining of skeletal muscle fibres varied, giving a mosaic-like pattern. Of the fixatives used (4 percent formaldehyde, 4 percent paraformaldehyde, formaldehyde-glutaraldehyde, and Bouin's fixative), 4 percent formaldehyde gave the most prominent staining; short fixation-time slightly increased the staining intensity. All the 9 embryonal and 9 alveolar rhabdomyosarcomas contained positively-stained tumour cells. The number of cells positively-stained and the intensity of the staining varied with differentiation: the most differentiated rhabdomyoblasts stained most intensely. However, also many poorly-differentiated tumour cells in highly cellular areas were positive. Myoglobin is considered a suitable marker of rhabdomyoblastic differentiation, thus the method used in this study may be valuable in the diagnosis.

Blood flow of the reproductive system in renal hypertensive rats during pregnancy

An experimental study on pregnant rats was undertaken to explore whether renal hypertension interferes with uteroplacental blood supply and fetal weight. Renal hypertension was induced by standardized clamping of the left renal artery. Two days before expected delivery, blood flow to the reproductive organs was determined by microsphere technique in normal control rats, rats with short-standing renal hypertension induced early in pregnancy, and rats with established renal hypertension induced 4 weeks before pregnancy. Myometrial and placental blood supply was considerably reduced in renal hypertensive rats compared to that in normotensive pregnant rats, with the reduction in placental blood flow being as much as 68% in rats with established renal hypertension. Nevertheless, there was no reduction in fetal weights, placental weights, or number of fetuses in the litters. These findings suggest that the nutritional blood supply of the placenta normally has a considerable overcapacity, perhaps a necessary safety margin so that the fetus can manage the circulatory demands associated with delivery. If hypertension causes intrauterine growth retardation only by means of reduced placental blood flow, this reduction in flow obviously must be considerable.

Oral contraception in diabetic women. A cross-over study on serum and high density lipoprotein (HDL) lipids and diabetes control during progestogen and combined estrogen/progestogen contraception

Twenty-three young women with insulin-dependent diabetes were randomly allocated to contraceptive treatment with either a progestogen only (Lynestrenol 0.5 mg) (LYN) or a combined oral contraceptive (OC) (ethinyl estradiol 50 micrograms + lynestrenol 2.5 micrograms) (EE + LYN). After six months treatment the medication was withdrawn for at least two months, after which the patients were placed on the other preparation. Diabetes control and serum and high density lipoprotein (HDL) lipids were assessed before and after 1, 3 and 6 months of treatment. Low-dose LYN administration did not alter the insulin requirement, blood glucose or body weight while the combined EE + LYN treatment increased the insulin requirement (p less than 0.01) without altering blood glucose or body weight. Low-dose LYN reduced serum triglycerides (p less than 0.001), serum cholesterol (p less than 0.001) and serum phospholipids (p less than 0.01) without affecting HDL lipids, while EE + LYN gave an inconsistent increase in serum triglycerides (p less than 0.01) but no change in HDL lipids. These findings confirm our earlier results and we conclude that EE + LYN influences diabetes control slightly more (although still not seriously) than the low-dose LYN. It is suggested that insulin-dependent diabetics (in contrast to non-diabetics) are more sensitive to the influence of 19-norprogestogens than to alkylated estrogens, with respect to lipid metabolism.