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PubMed1995

Relations between Doppler tracings of pulmonary regurgitation and invasive hemodynamics in acute right ventricular infarction complicating inferior wall left ventricular infarction.

To test the hypothesis that flow characteristics from pulmonary regurgitation (PR) can predict right ventricular (RV) involvement in patients with inferior wall acute myocardial infarction, we prospectively recorded continuous-wave Doppler tracings and right-sided cardiac hemodynamics in 48 consecutive patients with inferior wall acute myocardial infarction and PR. Right heart hemodynamics enabled the identification of 29 patients with (group 1) and 19 without (group 2) RV involvement. In patients with RV involvement, the pulmonary regurgitant flow pattern was characterized by a rapid rise in flow velocity to a peak level followed by an abrupt deceleration in mid-diastole, whereas in patients without RV involvement, the deceleration in mid-diastole was gradual. The pressure half-time of PR (PHTPR) and the lowest mid-diastolic to peak early diastolic velocity ratio were significantly lower in group 1 than in group 2 (91 +/- 31 vs 214 +/- 57 ms [p < 0.001], 0.35 +/- 0.08 vs 0.59 +/- 0.13 [p < 0.001], respectively). The best diagnostic accuracy (95%) was obtained with cut-off values of PHTPR < or = 150 ms and the lowest mid-diastolic to peak early diastolic velocity ratio < or = 0.5: sensitivity 100%, specificity 89%, positive predictive value 94%, and negative predictive value 100%. Using multiple logistic regression analysis, we found that PHTPR was the strongest predictor of RV involvement. Thus, these parameters, derived from pulmonary regurgitant tracings, are useful in the noninvasive bedside diagnosis of RV infarction.

Aged↗
PubMed1992

Inferior vena cava flow velocity waveforms in appropriate- and small-for-gestational-age fetuses.

Reference ranges of inferior vena cava flow velocities were constructed from a cross-sectional study of 118 appropriate-for-gestational-age fetuses of 18 to 40 weeks of gestation. Blood flow velocity waveforms were recorded with color and pulsed Doppler equipment. Peak velocities and time velocity integrals were measured from inferior vena cava during systole, early diastole, and atrial contraction. The systolic-to-diastolic ratios between the peak velocities and time velocity integrals were calculated, and the reverse flow with atrial contraction was quantified as the percentage of forward flow (percentage of reverse flow). Recordings were also obtained from 79 small-for-gestational-age fetuses free of structural and chromosomal abnormalities, divided into three groups according to umbilical artery velocity waveforms: normal pulsatility index values (group 1, n = 26), pulsatility index greater than 95th percentile of our reference limits but presence of end-diastolic velocities (group 2, n = 33), and absence of end-diastolic velocities (group 3, n = 20). Fourteen fetuses of groups 2 and 3 were also studied at weekly intervals until the onset of antepartum late heart rate decelerations. In appropriate-for-gestational-age fetuses no changes were evident in peak velocities and time velocity integrals ratios, whereas the percentage of reverse flow significantly decreased with gestation. No significant differences were found between these values and those obtained in small-for-gestational-age fetuses of group 1. A significant increase of peak velocities and time velocity integrals ratios and of percentage of reverse flow was evidenced in fetuses of both group 2 and 3. The fetuses of groups 2 and 3 with a percentage of reverse flow above the 95% confidence interval showed a poorer perinatal outcome when compared with the fetuses of the same groups but with values inside the normal range. In the 14 fetuses longitudinally followed up until the onset of late heart rate decelerations a significant and progressive increase of peak velocities and time velocity integrals ratios and percentage of reverse flow was evidenced in spite of minimal changes in the pulsatility index from both umbilical artery and different peripheral fetal vessels. This study presents evidence that in small-for-gestational-age fetuses with abnormal Doppler-measured placental resistance the modified flow velocity patterns in the inferior vena cava seem to deteriorate progressively with advancing gestation.

Blood Flow Velocity↗
PubMed1993

Intrapartum auscultation of the fetal heart rate.

A fetal heart rate recording containing a variable deceleration was played for 120 physicians and nurses. Although mean estimates for baseline and nadir of the fetal heart rate and duration of the deceleration were not significantly different from the actual values, individual estimates of the three parameters were widely distributed. Adjunctive techniques for intrapartum fetal heart rate auscultation are recommended.

Auscultation↗
PubMed1993

The development of abnormal heart rate patterns after absent end-diastolic velocity in umbilical artery: analysis of risk factors.

OBJECTIVES: Our objectives were to evaluate the time interval elapsing between the occurrence of absent end-diastolic velocity in the umbilical artery and either the development abnormal fetal heart rate patterns or delivery and to establish the maternal and fetal factors that may affect this interval. STUDY DESIGN: Thirty-seven fetuses free of structural and chromosomal abnormalities in which the development of absent end-diastolic velocity in umbilical artery was evidenced by serial Doppler recordings were studied. At the first occurrence the following factors were considered: gestational age, presence of hypertension or preeclampsia, amniotic fluid index, severity of growth retardation, and 10 different Doppler indices calculated from extracardiac and intracardiac vascular districts. Actuarial statistical methods were applied, with the occurrence of antepartum late heart rate deceleration as the censoring variable. RESULTS: The interval between the first occurrence of absent end-diastolic velocity in umbilical artery and delivery ranged from 1 to 26 days. Indications for delivery were the development of antepartum late heart rate decelerations in 23 fetuses (62.1%) and different maternal or fetal complications in the remaining 14 fetuses. Multivariate analysis revealed that gestational age and the presence of hypertension and pulsations in umbilical vein were the dominant factors in determining the length of this time interval. CONCLUSION: The duration of the time interval between the occurrence of absent end-diastolic velocity in umbilical artery and abnormal heart rate pattern differs considerably among fetuses, and it is mainly determined by gestational age and presence of maternal hypertension and pulsations in umbilical vein.

Blood Flow Velocity↗
PubMed1975

Computer diagnosis of labor progression.

Abnormal labor has been suspected of being inherently delectorious to the fetus. In order to explore this problem, clinical factors, labor progress, and fetal monitoring parameters were compared in matched groups of high-risk patients whose fetuses were in theoccipitoposterior (0P) and occipitoanterior postions. The OP group showed significant excesses of dysfunctional labor aptterns, uterine contraction pattern abnormalities, and late and variabl fetal heart rate decelerations not accounted for by theuse of oxytocin or the presence of cord problems. In OP labor, lower Apgar scores were associated withasignificant excess of preceding fetal heart rate decelerations independant of operative delivery. This study suggests that neonatal depression in OP laboris related to intrapartum factors preceding delivery and provides direct support for theconcept that abnormal labor may adversely affect the fetus. The OP position is an indication for close fetomaternal supervision during labor.

Adolescent↗
PubMed1987

Antepartum fetal surveillance in the patient with decreased fetal movement.

Whenever a patient has the subjective perception of decreased fetal movement, prompt evaluation in the form of antepartum fetal surveillance has been undertaken. The purpose of this report is to describe our experience with 489 pregnant women who came between Jan. 1 and Dec. 31, 1985 to our Antepartum Fetal Surveillance Clinic with this complaint alone or in association with another indication for fetal surveillance. Overall, 838 nonstress tests were performed, and the results were reactive, 93.2%; nonreactive, 6.8%; and fetal heart rate decelerations, 6.1%. Comparison of the first nonstress test results between those with decreased fetal movement alone or in combination with another diagnosis demonstrated a similar incidence of nonreactivity and fetal heart rate decelerations. In those patients whose indication was decreased fetal movement alone, there was a 3.7 times greater likelihood of diminished amniotic fluid volume. When the last test within 7 days of delivery was analyzed, the decreased fetal movement alone group had a lower incidence of cesarean delivery, cesarean delivery for fetal distress, and Apgar scores less than 7 than patients with an additional indication for testing. In summary, decreased fetal movement continues to be an acceptable indication for fetal surveillance. Based on our retrospective experience, the most reasonable approach appears to be a combination of nonstress test and amniotic fluid volume assessment. Unless the patient has additional indications for fetal surveillance, the patient with decreased fetal movement with a reactive nonstress test and a normal amniotic fluid volume does not appear to warrant additional testing.

Amniotic Fluid↗
PubMed1987

Fetal monitoring during emergency obstetric transport.

The practicality of fetal heart rate monitoring during fixed-wing transport of obstetric emergencies was evaluated. Fifty-seven transports were performed and 40 (70%) were monitored successfully with the electronic fetal heart rate monitor. External fetal heart rate monitoring was technically accomplished in 83% of monitored transports. Of the 40 patients monitored, 33 (83%) of the fetal heart rate tracings were considered useful for adequate evaluation of the fetal heart rate and contraction frequency. No patients had late decelerations during transport. At cabin pressures from 1100 feet to 7000 feet, fetal hypoxia as measured by late decelerations was not present in any patient.

Aircraft↗
PubMed1988

Fetal heart rate patterns during labor: neurologic and cognitive development at six to nine years of age.

The development of 50 children relative to the fetal heart rate patterns they demonstrated during labor and delivery was prospectively studied. Normal deceleration patterns were recorded for 12 of the children, while 16 were recorded as moderately severe and 22 as severe variable or late deceleration patterns. The parity and socioeconomic status of the mothers and the sexes of the infants were similar among the groups. A statistically significant developmental difference in favor of children with normal fetal heart rate patterns was seen in the first year of life. However, at 6 to 9 years of age the difference in neurologic and cognitive development was no longer evident. These data do not support the hypothesis that brief abnormal fetal heart rate patterns recorded during labor are indicative of irreversible central nervous system injury.

Achievement↗
PubMed1994

Cardiac and extracardiac flows in discordant twins.

OBJECTIVE: Our purpose was to evaluate Doppler-detectable differences in the fetal circulation of discordant twins with a growth defect resulting from either placental insufficiency or twin-to-twin transfusion syndrome. STUDY DESIGN: Serial weekly Doppler recordings were performed for at least 3 weeks preceding delivery in 15 pairs of dichorionic twins (group A) in which the smaller twin had fetal distress (i.e., antepartum fetal heart rate late decelerations) and in 10 pairs of diamniotic and monochorionic twins (group B) in which the diagnosis of twin-to-twin transfusion syndrome was confirmed postnatally. Doppler recordings were obtained from umbilical artery, descending aorta, and middle cerebral artery, and the pulsatility index values were calculated. Furthermore, peak velocity from cardiac outflow tract and the percent of reverse flow in the inferior vena cava were calculated. For all these index values the intertwin differences (delta value) were calculated by subtracting the values obtained in the larger twin with those of the smaller twin. RESULTS: In group A significant changes of delta values were evidenced for all the parameters tested. In particular, delta values of pulsatility index from the umbilical artery and descending aorta progressively increased approaching the occurrence of late decelerations, whereas the delta value for the middle cerebral artery reached a nadir 2 weeks before delivery. Similarly, delta values of peak velocity from outflow tracts significantly decreased, whereas those of the percent reverse flow in the inferior vena cava increased during the time considered. In group B fetuses no significant intertwin differences in pulsatility index values were evidenced in the vessels investigated, resulting in absence of modifications in delta values during the time interval considered. Moreover, significant changes were found in delta values of both the peak velocity from the outflow tract and the percent of reverse flow in the inferior vena cava. However, these changes were limited to the last recording, where the former delta value increased and the latter decreased. CONCLUSIONS: Serial Doppler recordings may show hemodynamic changes in the fetal circulation of discordant twins. Different trends occur according to the underlying pathophysiologic mechanisms of the growth defect. The knowledge of these temporal changes may be useful in the management of such fetuses.

Aorta, Thoracic↗
PubMed1996

Nucleated red blood cells: an update on the marker for fetal asphyxia.

OBJECTIVE: Our goal was to update our experience with nucleated red blood cells as a marker for fetal asphyxia and to determine whether a relationship exists between the presence of nucleated red blood cells and long-term neurologic impairment. STUDY DESIGN: Nucleated red blood cell data from 153 singleton term neurologically impaired neonates were compared with cord blood nucleated red blood cells of 83 term nonasphyxiated newborns. Newborns with anemia, intrauterine growth restriction, and maternal diabetes were excluded. The group of neurologically impaired neonates was separated into the following subgroups: group I, persistent nonreactive fetal heart rate pattern from admission to delivery (n = 69); group II, reactive fetal heart rate on admission followed by tachycardia with decelerations and absent variability (n = 47); group III, reactive fetal heart rate on admission followed by an acute prolonged deceleration (n = 37). The first and highest nucleated red blood cell value and the time of nucleated red blood cell disappearance were assessed. RESULTS: The mean number of initial nucleated red blood cells was significantly higher in the group of neurologically impaired neonates (30.3 +/- 77.5, range 0 to 732 per 100 white blood cells) than in the control group (3.4 +/- 3.0, range 0 to 12 per 100 white blood cells) (p < 0.000001). When the group of neurologically impaired neonates was separated on the basis of timing of the neurologic impairment, distinct nucleated red blood cell patterns were observed. Significant differences were obtained between each of the three groups of neurologically impaired neonates and the normal group, with respect to initial nucleated red blood cells (group I, 48.6 +/- 106.9; group II, 11.4 +/- 9.8; group III, 12.6 +/- 13.4; p < or = 0.000002). Maximum nucleated red blood cell values were higher in group I (mean 51.5 +/- 108.9) than in groups II and III combined (mean 12.7 +/- 11.9) (p = 0.0005). Group I also had a longer clearance time (119 +/- 123 hours) than groups II and III combined (mean 59 +/- 64 hours) (p < 0.001). CONCLUSION: Our ongoing study indicates that nucleated red blood cells identify the presence of fetal asphyxia. When fetal asphyxia is present, distinct nucleated red blood cell patterns are observed that relate to the timing of fetal injury. In general, intrapartum injuries are associated with lower nucleated red blood cell values. Thus our data continue to support the concept that nucleated red blood cell levels may assist in determining the timing of fetal neurologic injury.

Biomarkers↗
PubMed1997

Trauma in pregnancy: normal Revised Trauma Score in relation to other markers of maternofetal status--a preliminary study.

OBJECTIVE: Our goal was to examine whether a correlation exists between the Revised Trauma Score assigned on admission and pregnancy outcome, as well as whether the Revised Trauma Score has any predictive value for optimal duration of cardiotocographic monitoring necessary to detect immediate adverse pregnancy outcome. STUDY DESIGN: A retrospective chart review was performed of 30 pregnant trauma patients admitted during a 1-year period. Evaluation of cardiotocographic data for either contractions or decelerations or both was performed without knowledge of Revised Trauma Score or maternofetal outcome at discharge. RESULTS: Review of uterine activity and fetal decelerations did not detect useful predictive patterns unless the tracing was immediately ominous, although uterine activity did initially decrease over time. CONCLUSIONS: The Revised Trauma Score lacks predictive value for both risk of adverse pregnancy outcome and need for prolonged cardiotocographic monitoring. A larger patient population needs to be studied for an accurate determination of whether the Revised Trauma Score has potential as a predictive tool.

Cardiotocography↗
PubMed1999

The effect of magnesium sulfate on fetal heart rate parameters: A randomized, placebo-controlled trial.

OBJECTIVE: We sought to determine the effect of magnesium sulfate on fetal heart rate baseline value, variability, and acceleration-deceleration pattern. STUDY DESIGN: Normal, nonlaboring pregnant patients at >30 weeks' gestation were recruited. Baseline fetal heart rate monitoring for 1 hour was performed. After an 800-kcal meal, patients were randomized to receive either an intravenous loading dose of 6 g of magnesium sulfate in 100 mL of isotonic sodium chloride solution or 100 mL of isotonic sodium chloride solution alone. Subsequently, patients in the magnesium sulfate group received a 2-g/h intravenous infusion for 3 hours at a rate of 125 mL/h. Patients randomized to the sodium chloride solution group received a sodium chloride solution infusion at a similar rate (unlabeled intravenous bags). Maternal blood was drawn at 0, 1, and 3 hours for determination of total and ionized magnesium and calcium, electrolyte, and glucose levels. One hour of fetal heart rate monitoring was repeated at 1 and 3 hours of infusion. Tracings were interpreted without identifiers (of time or group) by using the National Institute of Child Health and Human Development fetal heart rate monitoring guidelines. RESULTS: Magnesium sulfate administration resulted in decreased fetal heart rate baseline values and variability in the third hour. The fetal heart rate baseline value was 134.4 +/- 6.3 versus 136.6 +/- 6.4 beats/min before infusion (P >.05), 134.4 +/- 7.1 versus 135.1 +/- 6. 6 beats/min in the first hour (P >.05), and 134.6 +/- 7.1 versus 132. 3 +/- 7.6 beats/min in the third hour (P <.05) in the sodium chloride solution group versus the magnesium sulfate group, respectively. Fetal heart rate variability (grades 1-5) was 2.75 +/- 0.33 versus 2.82 +/- 0.29 before infusion (P >.05), 2.81 +/- 0.30 versus 2.84 +/- 0.28 in the first hour (P >.05), and 2.71 +/- 0.52 versus 2.67 +/- 0.36 in the third hour in the sodium chloride solution group versus the magnesium sulfate group, respectively (P <. 05). Magnesium sulfate blocked the positive correlation between gestational age and number of accelerations found in control subjects. No significant decelerations were identified. CONCLUSIONS: Prolonged administration of magnesium sulfate was associated with decreased fetal heart rate baseline values and variability. Given the small magnitude of these changes, the clinical significance of these findings is questionable. Magnesium sulfate inhibition of the increasing number of accelerations with gestational age needs to be considered when fetal well-being is assessed.

Calcium↗
PubMed1999

A randomized clinical trial of daily nonstress testing versus biophysical profile in the management of preterm premature rupture of membranes.

OBJECTIVE: Our purpose was to evaluate the ability of 2 different antepartum testing modalities to predict infectious morbidity in patients with preterm premature rupture of membranes. STUDY DESIGN: During a 36-month period, patients with preterm premature rupture of membranes (at 23 to 34 weeks of gestation) were randomly assigned to either a daily nonstress test or a biophysical profile, after a 24-hour observational period. We used the original scoring system of Manning et al for the biophysical profile, with a score of </=6 considered abnormal. Nonstress test results were considered abnormal if the test was nonreactive or if the patient had late decelerations or significant variable decelerations; abnormal results led to further evaluation with a biophysical profile. Results of the last test before delivery were evaluated to determine whether infectious complications had been predicted. RESULTS: One hundred thirty-five patients were enrolled in the study. Demographics, pregnancy characteristics, and neonatal outcomes were similar. Neither the daily nonstress test nor the daily biophysical profile had good sensitivity for predicting infectious complications (39.1% and 25.0%, respectively). However, both had good specificity (84.6% and 92.6%, respectively). Positive and negative predictive values were 52.9% and 75.9%, respectively, for the daily nonstress test and 66.7% and 68.4%, respectively, for the daily biophysical profile. Cost was significantly higher in the daily biophysical profile group. Nonstress testing of patients at <28 weeks' gestation generally required a backup biophysical profile. CONCLUSION: Neither the daily nonstress test nor the daily biophysical profile had good sensitivity for predicting infectious complications after preterm premature rupture of membranes.

Adult↗
PubMed1999

Ventricular filling patterns of the right and left ventricles in normally grown fetuses: a longitudinal follow-up study from early intrauterine life to age 1 year.

OBJECTIVE: Our goal was to determine the effects of advancing age on the Doppler diastolic filling indexes from early gestation to 1 year of life. STUDY DESIGN: Seventy-nine fetuses were studied. Initial Doppler studies were started at about the 16th week of gestation and repeated every 4-6 weeks until term, on postnatal day 1 and 2, and at ages 6 weeks, 6 months, and 12 months. A minimum of 5 returning Doppler waveforms were traced and analyzed for (1) peak early flow velocity, (2) late peak atrial flow velocity, (3) total area area under the curve, and (4) the acceleration and deceleration phases. The stiffness of the ventricles was estimated. Slopes of the curves for each of the parameters were analyzed for differences across time periods and between right and left ventricles. RESULTS: (1) Heart rate significantly decreased with advancing age. (2) Left ventricular and right ventricular peak early flow velocity and late peak atrial flow velocity significantly increased during fetal life but not during the 1st year. (3) Atrial predominance was found during fetal life but not during the first year. (4) The deceleration phase of filling significantly increased during the fetal period. (5) Ventricular stiffness progressively decreased during the fetal period. (6) Increased ventricular filling shifted from a right-sided dominance in utero to a left-sided dominance after birth. CONCLUSIONS: (1) Fetuses have stiffer fetal ventricles than neonates. (2) The diastolic filling patterns in normally grown fetuses mimic those of the diseased adult heart. We speculate that this maturation process may be affected in fetuses born prematurely or small for gestational age.

Echocardiography, Doppler↗
PubMed1979

Cardia lymph in electrical ventricular fibrillation: an experimental study.

The flow velocity of cardiac lymph during electrical ventricular fibrillation under normothermic cardiopulmonary bypass was studied experimentally in dogs. The time needed for the cardiac lymph node to become stained after injection of dye into the apex myocardium of the left ventricle was measured as an indicator in determining flow velocity of cardiac lymph. The flow velocity was markedly decelerated immediately after the commencement of electrical ventricular fibrillation. It was accelerated, however, after 2 hours of continuous electrical ventricular fibrillation. The difference between the two values was significant (p less than 0.01). Absent contractility of the heart influenced the deceleration of flow velocity of cardiac lymph immediately after the commencement of electrical ventricular fibrillation. Acceleration after 2 hours involved stasis of cardiac lymph as a result of absent contractility and increment of lymph production due to the nonphysiological condition of the myocardium.

Animals↗
PubMed2003

Probing the cell peripheral movements by optical trapping technique.

Swiss 3T3 fibroblasts cultured on a poly-L-lysine-coated coverslip was stimulated with 0.5 micro M phorbol myristate acetate, and the movements of the peripheral membranes were probed with a 1- micro m polystyrene bead held in an optical trap. The bead brought into contact with the cell edge occasionally moved away from and returned to the original position. The movement ranged over 100 nm and occurred mainly in one direction, suggesting that the protruding cell membrane pushed the bead. The maximum velocities derived from individual pairs of protrusive and withdrawal movements exhibited a correlation, which is consistent with the previous reports. Acceleration and deceleration occurred both in the protrusive and withdrawal phases, indicating that the movements were regulated. Movement of the membrane occurred frequently with an ensemble-averaged maximum speed of 23 nm/s at the trap stiffness of 0.024 pN/nm, but it was strongly suppressed when the trap stiffness was increased to 0.090 pN/nm. Correlation of the protrusive and withdrawal velocities and the acceleration and deceleration both in the protrusive and withdrawal phases can be explained by the involvement of myosin motor at least in the withdrawal process. However, the fact that the movements were suppressed at higher trap stiffness implies a stochastic nature in the creation of the gap between the peripheral cell membrane and the actin network underlying it.

3T3 Cells↗
PubMed1994

Temperature-dependent effects of high pressure on the bioluminescence of firefly luciferase.

This study measured the effect of high pressure on the enzyme kinetics of firefly luciferase. When firefly luciferase is mixed with luciferin and ATP, a transient flash of light is produced, followed by a weak light, lasting hours. The first stage reaction produces an enzyme-luciferin-AMP complex and pyrophosphate. Addition of pyrophosphate to the reaction mixture decelerated the reaction rate, and the initial flash was prolonged to a plateau, showing a quasi-equilibrium state. The effects of temperature and pressure were analyzed at the plateau. The temperature scan showed that the maximum light intensity was observed at about 22.5 degrees C. When pressurized below the temperature optimum, pressure decreased the light intensity, while increasing it above the temperature optimum. According to the theory of absolute reaction rate, the following values were obtained for the bioluminescent reaction: delta V++ = 823.7 - 2.8 T cm3/mol and delta V = -280.47 + 0.94T cm3/mol, where T is the absolute temperature, delta V++ and delta V are, respectively, activation volume and the volume change due to thermal unfolding. The optimal temperature for the maximum light output occurs because the reaction rate increases with the temperature elevation at low temperature range, but the thermal unfolding of the enzyme decelerates the reaction velocity when the temperature exceeds a critical value. The intensity of luminescence is modified by the influence of pressure on both delta V++ and delta V. So long as the volume of the activated complex (V++) exceeds the average volume of the nonactivated complex (VN), pressure will slow down the reaction. At the point where the volumes become equal, there is no change in the rate under pressure. When the volume of the activated complex is less than that of the reactants, pressure will speed up the rate. This study showed that firefly luciferase is not exceptional to other enzymes in responding to high pressure.

Adenosine Triphosphate↗
PubMed2001

Brainstem activates paroxysmal discharge in human generalized epilepsy.

In nine patients with generalized epilepsy of convulsive seizures, the excitability change of the brainstem was evaluated over the course of the interictal paroxysmal discharge (poly spike-and-wave complex, poly SWC). The evaluation was carried out by a sequential analysis of brainstem auditory evoked potentials (BAEPs) before and during one sequence of poly SWC. The characteristics of BAEPs, i.e. far-field evoked potentials, allowed the evaluation of the excitability change in the brainstem, which was not influenced by the cortical activity. The excitability in the ventral brainstem, measured with the parameters of wave-III, showed a biphasic fluctuation (deceleration--acceleration) before the onset of poly SWC (minima at -0.7+/-0.4 s). On the other hand, the excitability in the dorsal brainstem, measured with the parameters of wave-V, showed no significant difference over the course of poly SWC. The results suggest that the biphasic excitability change in the ventral brainstem is conveyed to the cortex through the ascending activating system. The excitability acceleration preceded by deceleration in the ventral brainstem probably synchronizes the cortical activity profoundly enough to produce poly SWC through the activation of intralaminar thalamic neurons.

Adolescent↗