Association between early echocardiography screening of low systemic blood flow and intraventricular hemorrhage in preterm infants: a multicenter cohort study.

OBJECTIVE: To determine whether early echocardiography screening of low systemic blood flow reduces intraventricular hemorrhage in preterm infants. STUDY DESIGN: Prospective multicenter study in preterm infants below 33 weeks of gestational age at nine neonatal units. Five units performed early echocardiography screening for low systemic blood flow and guided clinical management (exposure group) and 4 units did not (control group). Our main outcome was ≥grade II intraventricular hemorrhage or death within the first 7 days of life. The main analysis used the inverse probability of treatment weighting. RESULTS: Three hundred and thirty-two preterm infants (131 in the exposure group and 201 in the control group) were included. Exposure to early echocardiography screening was associated with a significant reduction in ≥grade II intraventricular hemorrhage or early death [odds ratio 0.285 (95% CI: 0.133-0.611); p = 0.001]. CONCLUSIONS: Early echocardiography screening for low systemic blood flow may reduce the incidence of intraventricular hemorrhage in preterm infants.

Recovery of the first and second phases of the M wave after prolonged maximal voluntary contractions.

INTRODUCTION: We compared the recovery of muscle electrical properties after maximal voluntary contractions (MVCs) of 1 and 3 min duration by examining separately the first and second phases of the muscle compound action potential (M wave). METHODS: M waves were evoked by supramaximal single shocks to the femoral nerve throughout the 30-min recovery following 1-min and 3-min MVCs. The amplitude, duration, and area of the M-wave first and second phases, along with peak-to-peak amplitude and total area, were measured from the knee extensors. RESULTS: (1) The amplitude of the M-wave first phase increased to the same extent (and had the same time course of recovery) after the 1 and 3-min MVCs, whereas the amplitude of the second phase increased more markedly after the 1-min than after the 3-min MVC (P < 0.05). (2) The first phase remained enlarged for 2 min after exercise, whereas the augmentation of the second phase only lasted for 30 s. (3) After 30 min of recovery, the amplitude, area, and duration of both the first and second phases were decreased compared to control values (P < 0.05). CONCLUSIONS: The similar enlargement of the M-wave first phase after the 1 and 3-min MVCs suggests that the extracellular K+ concentration attained after these contractions was similar. The mechanisms responsible for the long-term decreases in M-wave amplitude and duration are unknown at present, but are likely due to a decrease in the amplitude of individual transmembrane potentials and an increase in conduction velocity.

Intravesical Oxybutynin for Urgent Bladder Rescue in a Newborn with Posterior Urethral Valves.

Posterior urethral valves are the most common cause of bladder outlet obstruction in male newborns. Initial catheter drainage alleviates the urethral obstruction before definitive management by valve ablation. Newborns with posterior urethral valves often present with hypercontractile bladders that may inhibit upper tract drainage despite bladder catheterization. Anticholinergic agents are commonly used to treat detrusor hyperactivity, with oxybutynin being the most commonly used. We report the first case of a newborn with posterior urethral valves and ureterovesical junction obstruction caused by detrusor hypertrophy who underwent urgent intravesical instillation of oxybutynin at high doses in an attempt to avoid a diversion procedure.

Influence of timing variability between motor unit potentials on M-wave characteristics.

The transient enlargement of the compound muscle action potential (M wave) after a conditioning contraction is referred to as potentiation. It has been recently shown that the potentiation of the first and second phases of a monopolar M wave differed drastically; namely, the first phase remained largely unchanged, whereas the second phase underwent a marked enlargement and shortening. This dissimilar potentiation of the first and second phases has been suggested to be attributed to a transient increase in conduction velocity after the contraction. Here, we present a series of simulations to test if changes in the timing variability between motor unit potentials (MUPs) can be responsible for the unequal potentiation (and shortening) of the first and the second M-wave phases. We found that an increase in the mean motor unit conduction velocity resulted in a marked enlargement and narrowing of both the first and second M-wave phases. The enlargement of the first phase caused by a global increase in motor unit conduction velocities was apparent even for the electrode located over the innervation zone and became more pronounced with increasing distance to the innervation zone, whereas the potentiation of the second phase was largely independent of electrode position. Our simulations indicate that it is unlikely that an increase in motor unit conduction velocities (accompanied or not by changes in their distribution) could account for the experimental observation that only the second phase of a monopolar M wave, but not the first, is enlarged after a brief contraction. However, the combination of an increase in the motor unit conduction velocities and a spreading of the motor unit activation times could potentially explain the asymmetric potentiation of the M-wave phases.

Limitations of Spectral Electromyogramic Analysis to Determine the Onset of Neuromuscular Fatigue Threshold during Incremental Ergometer Cycling.

Recently, a new method has been proposed to detect the onset of neuromuscular fatigue during an incremental cycling test by assessing the changes in spectral electromyographic (sEMG) frequencies within individual exercise periods of the test. The method consists on determining the highest power output that can be sustained without a significant decrease in spectral frequencies. This study evaluated the validity of the new approach by assessing the changes in spectral indicators both throughout the whole test and within individual exercise periods of the test. Fourteen cyclists performed incremental cycle ergometer rides to exhaustion with bipolar surface EMG signals recorded from the vastus lateralis. The mean and median frequencies (Fmean and Fmedian, respectively) of the sEMG power spectrum were calculated. The main findings were: (1) Examination of spectral indicators within individual exercise periods of the test showed that neither Fmean nor Fmedian decreased significantly during the last (most fatiguing) exercise periods. (2) Examination of the whole incremental test showed that the behaviour of Fmean and Fmedian with increasing power output was highly inconsistent and varied greatly among subjects. (3) Over the whole incremental test, half of the participants exhibited a positive relation between spectral indicators and workload, whereas the other half demonstrated the opposite behavior. Collectively, these findings indicate that spectral sEMG indexes do not provide a reliable measure of the fatigue state of the muscle during an incremental cycling test. Moreover, it is concluded that it is not possible to determine the onset of neuromuscular fatigue during an incremental cycling test by examining spectral indicators within individual exercise periods of the test. Key pointsThe behaviour of spectral EMG indicators during the incremental test exhibited a high heterogeneity among individuals, with approximately half of the participants showing a positive relation between spectral indicators and workload and the other half showing the opposite behaviour.None of the spectral EMG indicators examined (Fmean nor Fmedian) decreased significantly between the ventilatory threshold and the highest power output.Examination of spectral indicators within individual exercise periods of the test showed that neither Fmean nor Fmedian decreased significantly during the last (most fatiguing) exercise periods.

Neuroretinitis Caused by Bartonella henselae (Cat-Scratch Disease) in a 13-Year-Old Girl.

Cat-scratch disease-related neuroretinitis is a relatively unusual pathology, with suspicious clinical epidemiological and serological diagnosis. We present a case of an adolescent suffering from unilateral neuroretinitis associated with Bartonella henselae infection characterized by abrupt loss of vision, optic disc swelling, and macular star exudates with optimal response to antibiotic treatment.