Hepatitis B Postexposure Prophylaxis in Preterm and Low-Birth-Weight Infants.

Objective Recommendations for immunoprophylaxis in low-birth-weight (LBW) infants born to hepatitis B surface antigen (HBsAg)-positive mothers vary. We successfully immunized an HBsAg-exposed infant (birth weight: 400 g) and performed a literature review on the outcome of postexposure immunoprophylaxis in HBsAg-exposed preterm and LBW infants. Methods By use of PubMed we identified articles relevant to the topic. Studies were included if the intended vaccine schedule was completed and follow-up data were reported. Results Antibody response was reported in 31 LBW infants (birth weight < 2,500 g) and 49 infants with gestational age of < 38 weeks. Low anti-HBs antibody levels (< 100 IU/L) were found in 9 (29%) of the 31 LBW infants. Overall, 2 of 20 (10%) preterm infants and 2 of 17 (12%) LBW were HBsAg-positive on follow-up. In one study, none of the 26 exposed very LBW infants became infected. Conclusion Due to heterogeneity in immunization schedules, lack of information on transmission rates, and the small number of included subjects, no firm conclusions can be drawn regarding the optimal postexposure prophylaxis in LBW infants. We propose that active and passive immunization at birth should be completed by three further active doses (0-1-2-12 month schedule) until further prospective studies are available.

Cerebral oxygenation during intermittent hypoxemia and bradycardia in preterm infants.

BACKGROUND: Episodes of hypoxemia and bradycardia frequently occur with apnea of prematurity in preterm infants. Little is known about the impact of different event types on the brain. OBJECTIVES: To describe the influence of hypoxemia and bradycardia, either isolated or in combination, on cerebral oxygenation. METHODS: In 16 preterm infants with intermittent hypoxemia and/or bradycardia, cerebral tissue oxygen saturation (StO2, as measured by near-infrared spectroscopy), heart rate and pulse oximetric saturation (SpO2) were recorded simultaneously for 16 h. Events were classified as isolated bradycardia (type 1), isolated hypoxemia (type 2) or combined (simultaneous, type 3; bradycardia first, type 4; hypoxemia first, type 5). Primary outcome was a score representing the area below baseline for cerebral StO2 desaturation during an event. Secondary outcomes were duration and depth of cerebral desaturation. RESULTS: Patients had a median (range) gestational age of 25.9 (22.6-30.4) weeks and a postnatal age of 32.5 (7-58) days. The median (quartiles) number of events was 49 (34-58). Isolated hypoxemias were the most frequent events (24; 9-36) and isolated bradycardias the least common (0; 0-1). Cerebral StO2 baseline was not different between event types. Cerebral desaturation score, duration of event and depth of cerebral desaturation were smallest for isolated bradycardias and largest for combined events, especially for those starting with hypoxemia followed by bradycardia. Regardless of event type, 12/16 infants maintained cerebral StO2 >60% despite severe SpO2 desaturations. CONCLUSIONS: Isolated bradycardias had the lowest impact on cerebral desaturation, and combined events had the highest. Most infants preserved cerebral oxygenation >60% during events.

Prospective risk factor monitoring reduces intracranial hemorrhage rates in preterm infants.

BACKGROUND: Intracranial hemorrhage occurs in 20% to 25% of neonates born before the 30th week of gestation or weighing less than 1500 grams at birth. These hemorrhages carry a risk of long-term neurocognitive damage. Measures for lowering the incidence of intracranial hemorrhage were evaluated. METHODS: A working group at the University of Ulm, Germany, developed a prospective monitoring program for risk factors and a bundle of measures including altered clinical approaches to delivery, initial care of the neonate in the delivery room immediately after birth, and intensive care in the first few days thereafter. Adherence to these measures was checked once per week. The evaluation was performed prospectively for a period of 23 months (August 2010 to July 2012) with a 31-month period of historical controls (January 2008 to July 2010). RESULTS: In the reference period before the intervention was introduced, 263 neonates weighing less than 1500 grams and with a median (quartile) gestational age at birth of 27.4 (25.4-29.9) weeks were treated. The incidence of intracranial hemorrhage was 22.1%, and that of high-grade hemorrhage was 9.1%. The mortality was 6.1%, and the rate of survival without brain hemorrhage was 74.5%. After the bundle of preventive measures was introduced, 191 neonates weighing less than 1500 grams and with a median (quartile) gestational age at birth of 28.0 (26.0, 30.3) weeks were treated. The incidence of intracranial hemorrhage dropped to 10.5% (odds ratio [OR] 0.43, 95% confidence interval [CI] 0.25-0.73); the incidence of high-grade hemorrhage dropped to 3.7% (OR 0.36; 95% CI 0.14-0.89). The mortality was no different at 6.3%, and 85.3% of the children survived without a hemorrhage (OR 1.95, 95% CI 1.20-3.15). After statistical adjustment for higher gestational age, the OR for intracranial hemorrhage (IVH) was 0.49 (0.28-0.86) and the probability of survival without IVH improved (OR 1.68, 95% CI 1.01-2.81). CONCLUSION: The rate of brain hemorrhage in premature neonates can be considerably lowered by prospective monitoring of risk factors.

Cerebral desaturations in preterm infants: a crossover trial on influence of oxygen saturation target range.

OBJECTIVE: To test the hypothesis that a higher pulsoximetric arterial oxygen saturation (SpO2) target range is associated with reduced cerebral tissue oxygen desaturations from baseline during events of hypoxaemia or bradycardia. DESIGN: Randomised crossover trial. SETTING: Single tertiary care neonatal intensive care unit. PATIENTS: Sixteen preterm infants with severe intermittent hypoxaemia or bradycardia. INTERVENTIONS: SpO2 target was set to 80-92% and 85-96% for 4 h each in random sequence. On a subsequent day, the target sequence was reversed and the study was repeated. MAIN OUTCOME MEASURES: We simultaneously recorded cerebral tissue oxygen saturation (cerebral StO2), SpO2 and heart rate. Cerebral StO2 was measured by near infrared spectroscopy. The primary outcome was the cumulative cerebral StO2 desaturation score representing the area below a cerebral StO2 baseline value before onset of each hypoxaemic or bradycardic event. RESULTS: During low SpO2 target range the median (IQR) cumulative cerebral StO2 desaturation score was higher (27384 (15825-37396) vs 18103 (6964-32946), p=0.011) and the mean (±SD) number of events was higher (29.1 (±15.3) vs 21.1 (±11.4), p=0.001). More time was spent with SpO2 below 80% (57.2 (±24.8) min vs 34.0 (±29.6) min, p=0.006). Total time of hyperoxaemia (defined as SpO2 ≥97% and ≥99%, respectively) and total time with cerebral StO2 <60% and <55% were similar. CONCLUSIONS: A lower SpO2 target range was associated with a greater cumulative cerebral StO2 desaturation score, caused by more frequent SpO2 desaturations. However, time at very low cerebral StO2 was not affected. Episodes of hyperoxaemia were not reduced.

Nonsurgical care of intestinal and multivisceral transplant recipients: a review for the intensivist.

Intestinal and multivisceral transplantation has evolved from an experimental procedure to the treatment of choice for patients with irreversible intestinal failure and serious complications related to long-term parenteral nutrition. Increased numbers of transplant recipients and improved survival rates have led to an increased prevalence of this patient population in intensive care units. Management of intestinal and multivisceral transplant recipients is uniquely challenging because of complications arising from the high incidence of transplant rejection and its treatment. Long-term comorbidities, such as diabetes, hypertension, chronic kidney failure, and neurological sequelae, also develop in this patient population as survival improves. This article is intended for intensivists who provide care to critically ill recipients of intestinal and multivisceral transplants. As perioperative care of intestinal/multivisceral transplant recipients has been described elsewhere, this review focuses on common nonsurgical complications with which one should be familiar in order to provide optimal care. The article is both a review of the current literature on multivisceral and isolated intestinal transplantation as well as a reflection of our own experience at the University of Miami.

On a set of data for the membrane potential in a neuron.

We consider a set of data where the membrane potential in a pyramidal neuron is measured almost continuously in time, under varying experimental conditions. We use nonparametric estimates for the diffusion coefficient and the drift in view to contribute to the discussion which type of diffusion process is suitable to model the membrane potential in a neuron (more exactly: in a particular type of neuron under particular experimental conditions).

A stochastic model and a functional central limit theorem for information processing in large systems of neurons.

The paper deals with information transmission in large systems of neurons. We model the membrane potential in a single neuron belonging to a cell tissue by a non time-homogeneous Cox-Ingersoll-Ross type diffusion; in terms of its time-varying expectation, this stochastic process can convey deterministic signals. We model the spike train emitted by this neuron as a Poisson point process compensated by the occupation time of the membrane potential process beyond the excitation threshold. In a large system of neurons 1 < or = i < or = N processing independently the same deterministic signal, we prove a functional central limit theorem for the pooled spike train collected from the N neurons. This pooled spike train allows to recover the deterministic signal, up to some shape transformation which is explicit.