Ionized magnesium and calcium levels in umbilical cord serum of pregnant women with transient hypertension during labor.

Using a new ion selective electrode (ISE) to measure ionized magnesium (IMg2+), we compared levels of IMg2+ with total magnesium (TMg) and serum ionized calcium levels (ICa2+) in umbilical arterial and venous serum of 13 parturients who developed transient hypertension in labor with levels in 38 who remained normotensive. Ionized, but not total magnesium levels were significantly lower in the umbilical veins of the hypertensive compared to the normotensive subjects (0.46 +/- 0.01 v 0.51 +/- 0.01 mmol/L), and these were at least 15% lower than maternal levels found in nonpregnant women (0.60 +/- 0.005 mmol/L, P < .001). If umbilical vein samples reflect maternal levels as well, then these results suggest that lower IMg2+ levels may play a role in the development of transient hypertension in labor, and the potential utility of an ion selective electrode for ionized magnesium in the diagnosis of subtle magnesium deficient states.

Correlation of maternal serum C-reactive protein with outcome of tocolysis.

Subclinical intrauterine infection is an important cause of preterm labor, specifically where tocolysis has failed. Fifty patients in preterm labor with singleton pregnancies were studied prospectively to determine whether the presence or absence of C-reactive protein, a nonspecific marker for infection, would correlate with success or failure of tocolysis. Of the 50 patients, tocolysis failed in 11 of 15 women with a positive C-reactive protein determination. Tocolysis succeeded in 33 of 35 cases where C-reactive protein was negative (P less than .0005). Urinary tract infection occurred in 40% of the study patients, but was not a confounding factor in the interpretation of C-reactive protein.

Pregnancy in patients with cerebrospinal fluid shunts: report of a series and review of the literature.

Hydrocephalic women with cerebrospinal fluid shunts are now surviving to reproductive age. Twenty-one pregnancies in 18 patients with shunts, including 11 from the present series and 10 from previous series, were analyzed for neurological, obstetrical, and perinatal outcome. Fourteen women had preexisting shunts, and 4 had the onset of symptomatic hydrocephalus and the placement of shunts during pregnancy. Neurological complications occurred in 13 of 17 (76%) pregnancies in patients with preexisting shunts, including symptoms of increased intracranial pressure (ICP) in 10 of 17 (59%) pregnancies, exacerbation of seizure disorder in 2 of 17 (12%) pregnancies, and severe headaches without increased ICD in 1 patient. In 7 of 11 (66%) of the symptomatic patients, symptoms spontaneously resolved postpartum. Four of 17 (23%) of these pregnancies were associated with shunt obstruction requiring antepartum or postpartum surgery. Four patients had a primary shunt placement, and one had a shunt revision during pregnancy without complications. There were no unusual obstetrical or perinatal complications in the series. The clinical management of pregnant patients with hydrocephalus should include preconception counseling and magnetic resonance imaging, as well as the use of serial antenatal magnetic resonance images, ICP monitoring, or the judicious use of radioisotope studies of shunt patency if signs of increased ICP appear. A cesarean section is recommended for the delivery of the neurologically unstable patient. For asymptomatic mothers, a vaginal delivery with a shortened second stage and prophylactic antibiotics are advised.

Nonfatal venous air embolism during cesarean section: a case report and review of the literature.

Venous air embolism occurs in more than half of all cesarean sections. Predisposing factors in pregnancy include uterine surgery and manipulation, hypovolemia, and maternal positioning. The presence of an intracardiac septal defect and use of certain anesthetic agents place the patient at greater risk of fatal air embolus. The sudden development of hypotension, hypoxia, and a drop in end-tidal CO2 are typical signs of this condition. Supportive therapy includes flooding the surgical field with normal saline, placing the patient in reverse Trendelenburg with a left-lateral tilt, and discontinuation of nitrous oxide anesthesia. We report a case that was diagnosed and successfully managed during a cesarean section and review the literature on prophylaxis, diagnosis, and therapy of this condition. A high index of suspicion and use of precordial Doppler studies in the future will permit earlier diagnosis and therapy and decreased mortality from this common condition. The phenomenon of venous air embolism in the intrapartum period has been well described in the anesthesia literature but there have been few case reports of patients having this complication in the recent obstetrical literature. We wish to describe the clinical course and successful management of a patient with this complication during cesarean section and provide a review of the literature on the phenomenon of venous air embolism in the obstetrical patient with particular emphasis on pathophysiology, detection, and treatment.

Placental abruption after insertion of catheter tip intrauterine pressure transducers: a report of four cases.

BACKGROUND: Although intrauterine pressure transducers have proven efficacious in the management of certain laboring women, their use has been associated with small but definite risks to both mother and fetus. The introduction of catheter tip pressure transducers has facilitated the evaluation of intrauterine pressure, but there has been a paucity of data regarding complication rates with these newer devices. CASES: We report four cases of placental abruption following insertion of catheter tip intrauterine pressure transducers. Two were associated with placental lacerations. None of these patients had definite risk factors for abruption, but they developed signs and symptoms typical of it after insertion of the catheters. Perinatal outcomes were good except in one neonate, who developed shock secondary to anemia. Three of the four cases occurred when 599 patients at our institution were monitored with catheter tip pressure transducers. CONCLUSION: Although the risk of injury is small, neonatal morbidity can be severe, and an evaluation of risk versus benefit should be made prior to insertion of these devices.

Ionized serum magnesium and potassium levels in pregnant women with preeclampsia and eclampsia.

A prospective, cross-sectional study was performed to determine whether patients with preeclampsia or eclampsia had difficult serum levels or fractions of the active, ionized form of magnesium (IMg2+) as compared to normal, pregnant women. Using a novel ion selective electrode, we determined the IMg2+ levels and fractions as well as ionized calcium, sodium and potassium (K) in venous serum drawn on admission from 33 normal, pregnant women; 12 women with preeclampsia; and 2 women with postpartum eclampsia. Levels in 42 nonpregnant, age-matched, healthy women were also measured. We found that in normal pregnancy, levels and fractions of IMg2+ were significantly decreased as compared to levels and fractions in nonpregnant women (0.48 +/- 0.01 [SE] versus 0.60 +/- 0.005 mmol/L, and 63.2 +/- 1.0% versus 71.6 +/- 0.6%; P < .001 for both), but the levels and fractions in preeclamptics (0.48 +/- 0.01 mmol/L and 64.2 +/- 1.7%) were not significantly different (P > .05) from those in normal, pregnant women. Similarly, the levels and fractions of IMg2+ in the two eclamptic patients were within the ranges of normal and preeclamptic pregnancies. When the other cations were analyzed, a highly significant elevation (P < .001) in the mean K+ level and the K+/IMg2+ ratio in the preeclamptic patients was noted. Thus, it appears that serum IMg2+ levels are maintained in preeclampsia and eclampsia, but disturbances in K homeostasis and in the interrelationships between K and IMg2+ may occur.

A new method for the rapid determination of ionized Mg2+ in whole blood, serum and plasma.

A novel ion selective electrode (ISE) for ionized magnesium (IMg2+) in whole blood (WB), plasma (PL) and serum (S) has now been designed and characterized in normal human subjects, diseased and pregnant subjects. Using this ISE on various levels of aqueous Mg2+ solutions (0.1-3.0mM), mean Mg2+ values are within 94.6 and 99.2% of their targets. The linearity of the ISE (0.1-3.0mM) in aqueous solution and human PL and S ranges between 92.0 and 99.3%. The ISE is highly selective for IMg2+, yielding measurements in less than 2 min, and exhibiting no or negligible effects from physiologic concentrations of Ca2+,Na+,K+ or H+. Ligand binding studies indicate that pathophysiologic concentrations of most smaller molecular weight anions fail to interfere with IMg2+ measurements in aqueous solution, PL or S. Likewise, pathophysiologic concentrations of heavy metals or lipids do not interfere with measurements for IMg2+. Comparison of healthy, normal WB, PL and S IMg2+, using the ISE, with measurements of ultrafilterable Mg by atomic absorption spectroscopy (AAS) are excellent. The mean value for IMg2+ in normal WB, PL and S is 0.58-0.60mM (range = 0.53-0.67mM). Compared to total Mg (TMg) (0.75-0.96mM) and ICa2+ (1.10-1.30mM), IMg2+ is held in a narrow, tight range, representing 71% of TMg. Preliminary studies on plasma and serum IMg2+ during open heart surgery and term pregnancy demonstrate significant abnormalities in IMg2+ and % IMg2+. The new ISE for IMg2+ should prove invaluable and revolutionary in studies of Mg metabolism in both healthy and diseased states.

Clinical studies with the NOVA ISE for IMg2+.

The Nova ISE for IMg2+ was utilized to examine IMg2+ in plasma and serum of patients with a variety of pathophysiologic and disease syndromes (e.g., long-term renal transplants [LTRT], during and before cardiac surgery, migraine headaches, head trauma, pregnancy, chronic fatigue syndrome [CFS], non-insulin dependent diabetes mellitus [NIDDM], asthma and after excessive dietary intake of Mg). The results indicate that LTRT treated with cyclosporin A, migraine, head trauma, pregnancy, NIDDM, diseased pregnant, and asthmatic patients all on the average, exhibit significant depression in IMg2+ but not total Mg (TMg). Patients with CFS failed to exhibit changes in serum IMg2+ or TMg levels. Increased dietary load of Mg, for only 6 days, resulted in significant elevations of serum IMg2+ but not TMg. Correlations between the clinical course of several of these syndromes and the fall in IMg2+ were found. The Ca2+/Mg2+ ratio appears to be an important guide for signs of peripheral vasoconstriction and or spasm and possibly enhanced atherogenesis. Overall, the data point to important uses for ISE's for IMg2+ in the diagnosis and treatment of disease states.

Serum ionized magnesium and other electrolytes in the antenatal period of human pregnancy.

OBJECTIVE: To determine: 1) the concentrations and fractions of serum ionized magnesium (IMg2+) in normal antenatal patients and 2) whether they are altered by concentrations of other cations and serum proteins. DESIGN: A cross sectional study design. SETTING: An urban community hospital obstetrics clinic. SUBJECTS: 144 normal antenatal patients divided into four gestational age groups: (1) 25 at 6 to 12 weeks, (2) 55 at 13 to 20 weeks, (3) 37 at 21 to 27 weeks, and (4) 27 at 28 to 38 weeks. INTERVENTIONS: Utilizing ion selective electrodes, we determined concentrations and fractions of ionized magnesium, concentrations of ionized calcium, sodium, and potassium, and the pH level in the venous serum of the patients. Total magnesium (TMg), total calcium, total protein, albumin, and inorganic phosphorus were measured. MEASURES OF OUTCOME: The mean concentrations and fractions were compared between the groups. Correlations between concentrations or fractions of Mg and concentrations of the other cations or proteins were determined. RESULTS: All values are means+/-SD. IMg2+ concentrations are 0.53+/-0.03 mmol/L in the first trimester and are lowest (0.49+/-0.05 mmol/L, p<0.001) by the third trimester. The percent of ionized magnesium remains at approximately 66% in each antenatal group. Although mean Mg concentrations fall with advancing gestational age, the main determinant of the IMg2+ concentration in an individual patient is her TMg concentration. CONCLUSIONS: IMg2+ concentrations and fractions remain within a very narrow range during pregnancy and are minimally affected by physiologic hemodilution. We hypothesize that mobilization of intracellular or bone stores of magnesium helps maintain serum concentrations, thus placing a stress on magnesium balance.

Effects of vasoactive agents on isolated human umbilical arteries in preeclamptic women treated with magnesium sulfate: a preliminary report.

Increased vascular reactivity has been noted in preeclampsia. It is uncertain whether this increased reactivity extends to the umbilical circulation. Helical strips of human umbilical arteries from 12 preeclamptic and 17 control patients were set up isometrically in physiological solution. Four preeclamptics who had not received magnesium were included. The resting tensions of the strips, amplitudes, frequencies, and times of onset of spontaneous contractions during the incubation period were noted and did not differ between the groups. When logarithmic dose contractile-response curves were made for serotonin, bradykinin, and KCl for each group, differences were noted only for KCl. The threshold dose for KCl was higher in tissues from the preeclamptic group (8.52 +/- 0.96 mM) compared to the controls (4.09 +/- 0.59 mM) regardless of magnesium therapy. Also, the ED50 for KCl was higher for preeclamptics given magnesium (12.45 +/- 1.21 mM) compared to controls (9.17 +/- 1.05 mM). There were no significant differences between maximal tensions obtained, but a trend was noted for preeclamptics who did not receive magnesium to develop less tension than either controls or preeclamptics who did receive magnesium, regardless of the agonist tested. Relaxation times differed only for KCl, where there was a shortening of the time for the preeclamptics (8.76 +/- 0.64 min) compared to controls (14.53 +/- 2.46 min). These results do not support other studies in which an increased peripheral vascular reactivity in preeclamptics was noted. An explanation for the decreased reactivity to KCl awaits further investigation.

Effects of vasoactive agents on isolated human umbilical veins in preeclamptic women.

Increased peripheral vascular reactivity has been noted in preeclampsia. However, in a recent study we found decreased reactivity to vasoactive agents in umbilical arteries of preeclamptic patients. A similar preliminary study, therefore, was carried out on umbilical veins to determine whether preeclampsia affected umbilical venous reactivity. Helical strips of human umbilical veins from 7 preeclamptic and 8 control patients were set up isometrically in physiological salt solution. The resting tensions did not differ between the groups, but spontaneous rhythmic contractions began much earlier in the preeclamptic group than in the controls (8.29 +/- 4.14 vs. 49.22 +/- 9.71 min). There were no differences in the mean amplitudes of the contractions at their time of onset, but in 5 patients of each group the mean amplitudes progressively rose to a maximum at approximately 90 min after incubation, and this maximum was significantly lower in the preeclamptic group (234.43 +/- 72.95 vs. 751.64 +/- 186.13 mg). The frequencies of the contractions did not vary with time or between groups. Log-dose response curves were made for serotonin and KCl, and there were no differences in threshold doses, ED50, maximal tensions or relaxation times between groups. These results are similar to those reported in human umbilical arteries from preeclamptic patients in that no increase in reactivity to vasoactive agents was noted. In conclusion, the differences in the spontaneous rhythmic contractions between preeclamptic patients and controls may be new evidence of pathological changes in the umbilical venous system in preeclampsia.

Safety of intravenous glyceryl trinitrate in management of retained placenta.

A retrospective chart review of all anaesthesia consultations for retained placenta at 28 weeks' gestational age or more was performed to determine the safety and efficacy of intravenous glyceryl trinitrate therapy in the management of retained placenta. Of the 33 patients who received glyceryl trinitrate, 1 received a total dose of 50 micrograms and the remainder received 100 to 200 micrograms. All placentas were extracted within 4 minutes of the first bolus. The systolic and diastolic blood pressures and the haematocrit fell by a mean of 8.1 +/- 5.3 mmHg, 6.0 +/- 3.5 mmHg, and 2.6 +/- 1.7%, respectively (mean difference +/- SD, p < 0.05 for each). The pulse rose by a mean of 7.7 +/- 4.5 bpm (p < 0.001). Only 1 patient required ergometrine for continued atony. None of the patients required transfusions or operative therapy other than dilatation and curettage. The use of glyceryl trinitrate in doses of 200 micrograms or less for retained placenta appears efficacious and safe, and may obviate the need for general anaesthesia for uterine relaxation.

Ionized serum magnesium levels in umbilical cord blood of normal pregnant women at delivery: relationship to calcium, demographics, and birthweight.

Using a novel ion-selective electrode for ionized Mg (IMg2+), we sought to: (1) determine levels and fractions of IMg2+ in umbilical vessels of normal pregnant women: (2) determine their relationships with ionized calcium (ICa2+) levels: (3) determine whether any demographic or clinical parameters affect these levels of divalent cations: and (4) compare levels of IMg2+, total Mg, percent IMg2+, and ICa2+ with sera of normal pregnant and nonpregnant women. We obtained umbilical arterial and venous serum from 38 normal subjects and venous samples from 26 normal pregnant women and 42 nonpregnant women. The mean umbilical venous IMg2+ level (0.51 +/- 0.01 mmol/liter) was significantly greater than the umbilical arterial level (0.48 +/- 0.01 mmol/liter, p < 0.05), and the latter was similar to maternal venous levels (0.48 +/- 0.01 mmol/liter). The maternal venous mean value is 20% less than that found (0.60 +/- 0.005 mmol/liter) in peripheral serum of nonpregnant women. The ionized fractions were significantly (p < 0.01) higher in the umbilical veins than umbilical arteries, and the percent IMg2+ fractions were similar in umbilical arteries and maternal venous blood. IMg2+ levels were lower in multiparous patients and those who received epidural analgesia and higher in patients who had operative vaginal delivery and in Asians. Ionized fractions of Mg in umbilical veins were higher in large for gestational age infants. Our findings provide evidence of a Mg deficiency in pregnancy and suggest that measurement of IMg2+ may have clinical value for diagnosis and therapy of such deficiency.(ABSTRACT TRUNCATED AT 250 WORDS)

Serum ionized magnesium levels during intravenous MGSO4 therapy of preeclamptic women.

Using a novel ion-selective electrode, we have shown that there is over a 100% increase in venous serum levels of ionized Mg during intravenous MgSO4 therapy of preeclamptic patients. By 6 hours of therapy, the range is 0.92-1.65 mmol/l (95% C.I.). There are strong correlations between levels of ionized and total Mg throughout therapy (r = 0.92-0.95, p < 0.01).

Maternal-fetal transfer of ionized serum magnesium during the stress of labor and delivery: a human study.

OBJECTIVE: The purpose of this study was to compare levels and fractions of ionized magnesium in maternal venous serum with those in umbilical venous and arterial serum and to determine whether the maternal levels and fractions change during the stress of labor. METHODS: Utilizing an ion-selective electrode, we determined levels and fractions of ionized magnesium (IMg2+) and levels of ionized calcium (ICa2+) in the maternal venous serum (MVS) of 12 parturients on admission and at the end of labor, as well as in the umbilical venous (UVS) and umbilical arterial serum (UAS) at delivery. A paired-sample study design was used. RESULTS: Whereas mean levels of ICa2+ did not change significantly (p > 0.05) during labor, the mean (+/- SE) MVS levels of IMg2+ and total magnesium (TMg) fell from 0.50 +/- 0.01 and 0.80 +/- 0.02 mmol/L, respectively, on admission to 0.46 +/- 0.01 and 0.68 +/- 0.01 mmol/L (p < 0.01 and p < 0.001, respectively) at delivery. The ionized fraction, expressed as a percent (IMg2+/TMg x 100), increased from 62.8 +/- 2.1% to 67.8 +/- 1.2% (p < 0.05). In the UVS, the mean IMg2+ level (0.52 +/- 0.02 mmol/L) and the mean ionized fraction (73.6 +/- 1.7%) were higher than in MVS on admission or at delivery (p < 0.05 for all comparisons). The mean IMg2+ level in UAS (0.50 +/- 0.02 mmol/L) was lower than in UVS (p < 0.05), but higher than in MVS at delivery (p < 0.01). Finally, there were significant positive correlations between levels of magnesium (Mg) in MVS and in the UAS or UVS. CONCLUSIONS: The observation that UAS levels of IMg2+ and TMg were similar to the MVS levels on admission despite the fall in maternal levels during labor points to the presence of homeostatic mechanisms in the fetus and placenta. It is possible that the presence of a higher fraction of unbound, free magnesium in UVS enhances magnesium transport to the fetus and thus homeostasis. Finally, we hypothesize that the fall in the levels of the biologically active form of Mg during labor may be yet another manifestation of the known stress responses to labor.

Cerebral function monitor in the neonate. I: Normal patterns.

The cerebral function monitor (CFM) is a monitoring device which records integrated encephalograms (EEGs on slow-running paper, allowing continuous observations of cerebral activity for prolonged periods. The CFM was assessed in 49 normal neonates of different gestational ages and was found to reflect EEG activity accurately. Gestational age and sleep-wake states could be differentiated and normal patterns were defined. The establishment of normal patterns will allow further assessment of the CFM as a screening tool for the neonate at risk for cerebral hypoxic ischemic injury.

Cerebral function monitor in the neonate. II: Birth asphyxia.

The cerebral function monitor (CFM) records an integrated electroencephalogram on slow-running paper, and therefore is suited to long-term, continuous monitoring. This study describes CFM patterns of 31 neonates with birth asphyxia. Three distinct types emerged: (1) a normal pattern compatible with gestational age was uniformly associated with favorable clinical outcome; (2) a completely disorganized pattern was associated with sever injury and fatal outcome; and (3) a more subtle pattern showed reversal to a more immature gestational age. The three infants with the third pattern all survived, but with varying degrees of neurological deficit. It is concluded that the CFM can be of advantage in predicting outcome for asphyxiated neonates.