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Biomedical subjects

N M Fisk

Publications and source records attributed to N M Fisk.

At least 235 records · Page 13Linked to original sources
PubMed1987

Is C-reactive protein really useful in preterm premature rupture of the membranes?

In a prospective blind study 380 daily serum samples from 55 women with preterm premature rupture of the membranes were analysed for C-reactive protein (CRP). Although the last CRP before delivery was higher in patients with histological chorioamnionitis (P = 0.007), considerable overlap between infected and non-infected pregnancies occurred, precluding the use of CRP as a diagnostic test if published normal levels were used. When upper limits were set at 30, 35, or 40 mg/l, the last CRP before delivery proved 90, 95 and 100% specific and 88, 92 and 100% positively predictive of infection in singleton pregnancies. Such high specificities are needed to prevent inappropriate intervention based on false positive results. We therefore propose upper limits for single estimations of 30, 35, or 40 mg/l depending on the relative risks of preterm delivery versus infection at various gestational ages. In addition, consecutive values greater than 20 mg/l appeared highly predictive of infection.

C-Reactive Protein↗
PubMed1987

A dipstick test for infection in preterm premature rupture of the membranes.

Microbiological analysis of amniotic fluid obtained by amniocentesis is increasingly employed in preterm premature rupture of the membranes (PPROM) to predict those patients at increased risk of chorioamnionitis. Although liquor culture appears the most accurate predictor, a role exists for rapid but slightly less accurate testing. In this study, a dipstick (Cytur-test) which predicts the presence of leukocytes was evaluated in amniotic fluid. Twenty-one samples were obtained by amniocentesis from 25 women with PPROM at gestation 26-34 weeks. The dipstick predicted 5 out of 6 specimens with a positive culture and 12 of 14 with a negative culture (figure 1). Its accuracy as a predictor of a positive culture was similar to microscopy for polymorphs, with sensitivities of 83.3% and 80% respectively and specificities of 85.7% and 92.3%. Neither test proved as predictive of histological chorioamnionitis due to 6 patients delivering greater than 48 hours after amniocentesis who may have developed infection subsequent to the demonstration of sterile liquor.

Amniocentesis↗
PubMed1987

Avoidance of maternal morbidity in acute intrauterine infection following chorionic villus sampling.

Serious maternal morbidity has been a feature of the few documented cases of acute intrauterine infection after chorionic villus sampling. A case is described in which infection manifested 14 days after transcervical chorion biopsy. Broad-spectrum antibiotics were begun, and ultrasound demonstrated a live fetus. After vacuum curettage was performed, repeat scan showed an empty uterus. Anaerobes isolated from the cervix both before chorionic villus sampling and during the infection were also implicated in published reports of patients developing life-threatening complications, but were not treated specifically until after morbid sequelae had occurred. Serious morbidity was avoided in this patient by aggressive management with early anaerobic cover, uterine evacuation despite the presence of a live fetus, and confirmation of complete evacuation by ultrasound.

Abortion, Therapeutic↗
PubMedDate not supplied

Vibroacoustic stimulation is not associated with sudden fetal catecholamine release.

The safety of vibroacoustic stimulation (VAS), which produces marked changes in fetal heart rate, movements and behavioural state, remains unclear. In order to determine whether VAS is associated with catecholamine release, we measured plasma noradrenaline and adrenaline in 13 appropriately grown normoxaemic fetuses between 28 and 40 weeks gestation immediately before and 60 and 75 s after VAS. Over this time interval, VAS is known to increase fetal heart rate. There was no significant change in either noradrenaline (median change = +0.06 ng/ml, P = 0.26) or adrenaline levels (median change = +0.03 ng/ml, P = 0.4). This study suggests that sympathoadrenal activation is not part of the fetal response to VAS. These findings do not support the recent suggestion that VAS may be deleterious to the fetus by provoking sudden release of catecholamines.

Acoustic Stimulation↗
PubMedDate not supplied

Occlusion of arterio-arterial anastomosis manifesting as acute twin-twin transfusion syndrome.

In vivo, ex vivo and modelling studies suggest that arterio-arterial anastomoses (AAAs) protect against haemodynamic imbalance in monochorionic twins and thus the development of TTTS. We report the acute onset of severe TTTS at 34 weeks' gestation in a patient with an antenatally visualized AAA which was shown at injection studies to have been obliterated, presumably by thrombosis. Computer modelling with the relevant clinical data confirmed that occlusion of the AAA alone was sufficient to reproduce the clinical manifestations. A study of the vascular configuration of AAA in the fixed placenta suggested that its small diameter and turbulent flow may have contributed to its occlusion. This case report shows that the unmasking of unbalanced AVA configurations by occlusion of a protective AAA can manifest as TTTS.

Arterio-Arterial Fistula↗
PubMedDate not supplied

Pseudo-arterio-arterial anastomoses in twin-twin transfusion syndrome.

OBJECTIVE: It has recently been claimed that fetoscopic recognition of a haemodynamic equator within an arterio-arterial anastomosis (AAA) suggests minimal net intertwin flow. This was based on blood from one fetus being dark and from the other bright red, the boundary between them reciprocating with the fetal heart beats. However, bright red indicates that the blood had passed through a cotyledon and been freshly oxygenated, which should be impossible in an AAA. We applied a computer model of chorionic vessels to determine a configuration that reproduced this phenomenon. METHODS: A previously published TTTS model was extended to provide placental detail in a segment containing four cotyledons of each placenta supplied by three generations of placental arteries and veins. RESULTS: Reciprocating flow is not unique to AAAs. It also occurs in the chorionic arteries of any cotyledon deprived of its venous outflow, in a similar manner to that in which reverse end-diastolic flow occurs in umbilical arteries when whole placental resistance is high. If venous return from the common chorionic vein in the recipient (draining the venous end of an AVA) is blocked as might happen after laser, there can be bidirectional flow from one umbilical artery insertion, through two cotyledons to the other insertion. We define this phenomenon as a pseudo-AAA (PAAA). The inclusion of two cotyledons in this path means that its resistance cannot match the low flow resistance of a true AAA, and transmission of the contralateral pulsatile pattern is absorbed in the cotyledons. Thus, PAAA Doppler patterns differ from true AAA patterns in that two sets of systolic peaks, one forward and one reverse, can be discerned in true AAAs but only one in PAAAs. CONCLUSIONS: We demonstrate how venous occlusion of an arterio-venous anastomosis may produce a pseudo-AAA colour equator at endoscopy. However, visual observation of reciprocating flow is not sufficient to define a vessel as a true AAA which instead requires ultrasonical identification of two systolic patterns.

Adult↗
PubMedDate not supplied

Effects of antenatal thyrotropin-releasing hormone on fetal heart rate and breathing movements.

OBJECTIVE: To determine the effect of maternally administered thyrotropin-releasing hormone (TRH) on fetal heart rate (FHR) pattern and fetal breathing movements (FBM). METHODS: Prospective observational study of 75 pregnant women between 26 and 34 weeks' gestation in whom pharmacological fetal lung maturation was clinically indicated. Forty-minute recordings were made of FBM or FHR patterns before and after drug administration. Twenty-five received TRH 400 microg as an intravenous bolus, 25 TRH 400 microg in 50 ml 0.9% saline as an intravenous infusion, and 25 acted as controls. Recordings were processed digitally to calculate the change in FHR (n = 45) and FBM parameters (n = 30). The main outcome measures for FHR were number of accelerations and decelerations, baseline rate, overall and short-term variation and duration of high and low variability, while for FBM they were rate, breath-to-breath interval and incidence. Results between groups were compared by analysis of variance. RESULTS: There was no significant change in FHR, accelerations or variation in any of the groups. Similarly, there was no change in the incidence of FBM. TRH administered as a bolus produced a small statistically but not clinically significant increase in breathing rate (mean delta = 35 breaths/h, p = 0.004), which was not seen in the TRH infusion and control groups. CONCLUSIONS: Maternally administered TRH as used to enhance fetal lung maturation has no clinically significant direct effect on FHR or FBM patterns.

Female↗
PubMedDate not supplied

High sensitivity of fetal DNA in plasma compared to serum and nucleated cells using unnested PCR in maternal blood.

DNA analysis of blood is conventionally performed on cells - plasma and serum are discarded. Free DNA has been demonstrated in serum in cancer and autoimmune disorders and in pregnancy. We investigated possible noninvasive prenatal diagnosis using fetal DNA from maternal plasma and serum in pregnancy. Fetal gender was determined by PCR on DNA from maternal venous blood, serum and plasma of 65 women by boiling with or without phenol/chloroform extraction. When sensitivities were compared for plasma, additional phenol/chloroform extraction proved more sensitive than boiling alone (89 vs. 50%), the observed difference was 50% (CI 19 to 81%). Extracted plasma amplified better than extracted serum (89 vs. 46%), the observed difference being 44% (CI 22 to 66%). In contrast, fetal gender could not reliably be determined from DNA extracted from maternal nucleated blood cells. The size of plasma and serum DNA at 15-17 weeks of gestation was >1,500 bp. This work confirms the presence of fetal DNA in maternal plasma and serum which may be applicable to noninvasive prenatal diagnosis of paternally derived DNA sequences. We conclude that optimal sensitivity requires two methods of DNA extraction and that the use of plasma is preferred to that of serum.

Chloroform↗
PubMedDate not supplied

Maternal contamination at fetal muscle biopsy.

Duchenne muscular dystrophy (DMD) can be diagnosed by fetal muscle biopsy and immunohistochemical staining showing the absence of dystrophin. We report a case of fetal muscle biopsy in which the needle gun was successfully fired within the fetal gluteal muscle but the sample was contaminated by maternal tissue. This was attributed to the design of the biopsy needle, allowing transient opening of the biopsy core as the needle penetrated the maternal rectus sheath, muscle, and myometrium. Histology showed tissue suggestive of maternal origin, confirmed by DNA analysis. Repeat sampling revealed fetal muscle with normal dystrophin expression. We recommend that care be taken during needle insertion to avoid maternal contamination, and tests be used to confirm the fetal source of the sample.

Adult↗
PubMedDate not supplied

Test amnioinfusion to determine suitability for serial therapeutic amnioinfusion in midtrimester premature rupture of membranes.

OBJECTIVE: To evaluate whether a test amnioinfusion procedure is useful in selecting cases of midtrimester preterm premature rupture of membranes (PPROM) which may benefit from serial amnioinfusions if the initial fluid is retained. STUDY DESIGN: The Centre for Fetal Care database between 1992 and 2000 was reviewed for women with PPROM <26 weeks who had undergone amnioinfusion. Amniotic fluid index (AFI) was assessed before and after a test amnioinfusion procedure. Those who retained fluid > or =48 h underwent serial AFI assessment with a view to serial amnioinfusion when oligohydramnios recurred. RESULTS: Eighty-five amnioinfusion procedures were performed in 60 women with oligohydramnios. Nineteen of these women presented with confirmed PPROM at a median gestation of 19 (range 15-22) weeks and severe olighohydramnios (median AFI 1, range 0-3 cm), in whom 20 test amnioinfusions were carried out. Two amnioinfusions were abandoned during the procedure because of fetal bradycardia and both mothers opted for termination of pregnancy. Only 4 women retained fluid during the test amnioinfusion, 1 of whom miscarried at 19 weeks before serial amnioinfusion could be started. The remaining 3 underwent a median of 4 (range 1-6) serial amnioinfusion procedures; none had evidence of pulmonary hypoplasia. Thirteen (68%) leaked fluid within 48 h; within this group there was 1 subsequent miscarriage and 9 pregnancy terminations. The remaining 3 pregnancies resulted in livebirths 2 of which had pulmonary hypoplasia with 1 early neonatal death. Overall survival was poor (4/19), largely attributed to the high incidence of terminations in the presence of persistent severe oligohydramnios. In continuing pregnancies reaching viability survival was 67% (4 of 6). CONCLUSION: Three quarters of women with mid-trimester PPROM lose fluid at test amnioinfusion and therefore would not be suitable candidates for serial amnioinfusion. However, if infused fluid is retained, this allows subsequent serial amnioinfusion and prolongation of pregnancy in about 75%, with an attendant decrease in the risk of pulmonary hypoplasia. However, even successful serial amnioinfusion remains associated with procedure-related complications (i.e. chorioamnionitis, placental abruption) which themselves may predispose to preterm delivery.

Adult↗
PubMedDate not supplied

Fetal ovarian cysts: diagnostic and therapeutic role for intrauterine aspiration.

Antenatal diagnoses of fetal ovarian cysts have not usually been confirmed until postnatal surgery. We describe 2 cases of hemorrhage into fetal ovarian cysts in which cyst aspiration in utero allowed both confirmation of the diagnosis prenatally and obviated the need for neonatal surgery. In both cases, cytology of the cyst aspirate demonstrated luteinized granulosa cells and biochemistry showed estradiol levels of > 10,000 pmol/l, indicating ovarian etiology. Hemorrhage, which had been suspected on ultrasound, was confirmed by cytology, showing hemosiderin-laden macrophages. There was no evidence of recurrence in either case following aspiration. The described association of fetal hypothyroidism was excluded by testing thyroid function in cord blood and/or cyst aspirate. We suggest that intrauterine aspiration contributes to the management of fetal ovarian cysts by confirming their ovarian origin, demonstrating the presence or absence of hemorrhage and facilitating preservation of ovarian function both by reducing the risk of torsion and the need for neonatal surgery.

Adult↗
PubMedDate not supplied

Carbohydrate metabolism in fetuses with Rh alloimmunization.

Glucose, insulin, glucagon and fructosamine were measured in the plasma of control (n = 34) and of Rh fetuses (n = 22) before the first and subsequent transfusion. Prior to treatment, Rh fetuses, compared to controls, had raised concentrations of glucose (p = 0.01), glucagon (p = 0.04) and fructosamine (p = 0.004). Fetal insulin levels were not significantly different. Before subsequent transfusion, despite correction of anemia, Rh fetuses were clearly hyperinsulinemic even after correction for gestation (p = 0.002) and had low glucagon concentrations (p = 0.01) when compared with values at the first transfusion. This metabolic milieu appears similar to that of fetuses of diabetic mothers which have increased plasma glucose and insulin during most of the last third of gestation.

Blood Glucose↗
PubMedDate not supplied

Impaired fetal blood gas status in polyhydramnios and its relation to raised amniotic pressure.

A substantial proportion of perinatal losses in polyhydramnios occur as unexplained normally formed stillbirths. In order to investigate the relationship between fetal condition and raised amniotic pressure (AP), fetal blood gas and acid-base status were determined together with AP in 22 pregnancies with polyhydramnios. At fetal blood sampling, 8 (36%) had a venous pH value and 16 (73%) a pO2 value below the reference range. Both fetal pH and pO2 were significantly negatively correlated with the degree of elevation in AP (y = 7.43 - 0.036x, r = 0.56, p = 0.006, where y = pH and x = AP z score, and y = -1.6 - 0.48x, r = 0.54, p = 0.01, where y = pO2 z score, respectively). Although some of these fetuses were hydropic, had congenital anomalies, or were from multiple pregnancies, univariate and multiple logistic regression analyses indicated that the above associations could not be accounted for by these potentially confounding variables. This work suggests that abnormal fetal blood gas status in human pregnancies with poly-hydramnios is associated with elevated AP.

Acid-Base Equilibrium↗