Effect of ampicillin on bleeding time in very low birth-weight neonates during the first week after birth

Ampicillin dosing in premature infants for early-onset sepsis: exposure-driven efficacy, safety, and stewardship

OBJECTIVE

Define optimal ampicillin dosing for empiric early-onset sepsis (EOS) therapy in preterm neonates.

STUDY DESIGN

We simulated ampicillin concentrations in newborns (birthweight < 1500 g; gestational age 22-27 weeks), summarizing three 48 h regimens: high 100 mg/kg Q8hr, medium 100 mg/kg Q12hr, and standard 50 mg/kg Q12hr. Concentration data were analyzed for concentration above minimum inhibitory concentration (MIC), below neurotoxicity threshold (Cmax ≤ 140 mcg/mL), and duration limited to 48 h.

RESULTS

Among 34,689 newborns, all dosing regimens provided concentrations above MIC through 48 h, but Cmax exceeded the neurotoxicity threshold. With the 4-dose standard regimen, >90% maintained concentrations >MIC beyond 48 h. With the 2-dose regimen, newborns maintained the mean concentration >MIC within the 48 h culture window and below neurotoxicity level. Infants 22-24 weeks' gestation had higher drug concentrations and more prolonged exposure duration than 25-27 weeks' gestation.

CONCLUSIONS

For EOS in preterm infants, two ampicillin doses (50 mg/kg) provided optimal bactericidal exposures, while minimizing potential toxicity.

Ampicillin Dose for Early and Late-Onset Group B Streptococcal Disease in Neonates

Ampicillin is frequently used in neonates for early- and late-onset group B streptococcal (GBS) disease. In 2019, the American Academy of Pediatrics (AAP) published guidelines for GBS which included updated dosing recommendations for ampicillin for bacteremia and provided specific dosing recommendations for meningitis. The dosing recommendations in the guidelines were based off the 2018 Report of the Committee on Infectious Diseases (i.e., Red Book), which differed from the 2015 Red Book. For bacteremia, no dosing changes were recommended for ampicillin dosing in neonates ≤ 7 days of postnatal age (PNA), but less frequent dosing intervals were recommended for neonates > 7 days PNA. For meningitis, increased dosing recommendations were provided in the update. However, the rationale and supporting evidence for these changes were not provided. A literature search was performed to review articles pertaining to the pharmacokinetics (PK), pharmacodynamics (PD) and safety of ampicillin in neonates. The ampicillin dosing recommendations in the AAP guidelines were mainly supported by a 2014 publication that evaluated the PK and PD of ampicillin in neonates with gestational age (GA) of 24 to 41 weeks and PNA of 0 to 25 days. The proposed dosing from this study for bacteremia is included in the 2018 Red Book and 2019 guidelines. For meningitis, no supporting evidence was identified for the dosing recommendations in the 2018 Red Book and 2019 guidelines. Only one study has evaluated ampicillin concentrations in cerebrospinal fluid, but proposed dosing from this study was much lower than that included in the guidelines. The high ampicillin doses for GBS meningitis should be used with caution, as high ampicillin concentrations have been associated with seizures and no studies have evaluated efficacy of this dosing strategy. The purpose of this review is to identify key pieces of literature regarding dosing recommendations and safety of ampicillin in neonates. KEY POINTS: · Recent guidelines provide dosing recommendations for ampicillin, but the supporting evidence is not included.. · Literature supporting evidence for ampicillin dosing for bacteremia is available, but not for dosing for meningitis.. · Recommended meningitis dose may result in supratherapeutic concentrations and increase seizure risk..

Primary hemostasis in fetal growth restricted neonates studied via PFA-100 in cord blood samples

BACKGROUND

Platelet function of fetal growth restricted (FGR) neonates remains a field of debate. Platelet function analyzer (PFA-100) offers a quantitative in vitro assessment of primary, platelet-related hemostasis. Our aim was to examine platelet function using PFA-100 in FGR neonates and associate our results with perinatal parameters.

METHODS

PFA-100 was applied on 74 FGR neonates, 48 full-term (>37 weeks' gestation) and 26 preterm neonates (<37 weeks). The control group consisted of 118 healthy neonates. Two closure times (CTs) with COL/EPI and COL/ADP cartridges were determined on cord blood samples for each subject. Statistical analysis was performed by SAS 9.4. The statistical significance level was set at 0.05 and all tests were two-tailed.

RESULTS

COL/EPI CTs were prolonged in FGR (median 132 s, IQR 95-181 s) compared with control neonates (median 112.5 s, IQR 93-145 s), p = 0.04. Median COL/EPI CT for term and preterm FGR neonates was 126 s (IQR 90-157 s) and 137 s (IQR 104-203), respectively (p = 0.001), and COL/ADP CT was 70 s (IQR 62-80 s) for term and 75 s (IQR 68-82 s) for preterm FGR neonates (p = 0.08). Among FGR neonates, COL/EPI CT was related with delivery time (with preterm neonates exhibiting prolonged COL/EPI CTs), p = 0.05. No correlation was proved between both CTs and hematological parameters in FGR neonates.

CONCLUSION

FGR neonates showed impaired platelet function via PFA-100, with preterm FGR neonates confronting the greatest risk. Prolonged COL/EPI CTs in FGR neonates seemed to be independent of hematological parameters and could warn for closer evaluation during the first days of their lives.

Ampicillin Pharmacokinetics During First Week of Life in Preterm and Term Neonates

BACKGROUND AND AIMS

Ampicillin is 1 of the most commonly used antibiotics for treatment of early onset sepsis, but its pharmacokinetics (PK) is poorly characterized. We aimed to define the dose of ampicillin for late preterm and term neonates by evaluating its PK in serum, cerebrospinal (CSF), and epithelial lining fluid.

METHODS

A prospective study included neonates receiving ampicillin for suspected or proven early onset sepsis and pneumonia. PK samples were collected at steady state, at predose and 5 minutes, 1 hour, 3 hours, 8 hours, and 12 hours after ampicillin 3-minute infusion. Ampicillin concentrations were measured by ultra-high-performance liquid chromatography. Noncompartmental anaysis (NCA) and population pharmacokinetic (pop-PK) modeling were performed and probability of therapeutic target attainment was simulated.

RESULTS

In 14 neonates (GA of 32-42 wks; mean BW 2873 g), PK parameters (mean ± SD) in NCA were the following: half-life 7.21 ± 7.97 hours; volume of distribution (Vd) 1.07 ± 0.51 L; clearance (CL) 0.20 ± 0.13 L/h; 24-hour area under the concentration-time curve 348.92 ± 114.86 mg*h/L. In pop-PK analysis, a 2-compartmental model described the data most adequately with the final parameter estimates of CL 15.15 (CV 40.47%) L/h/70kg; central Vd 24.87 (CV 37.91%) L/70kg; intercompartmental CL 0.39 (CV 868.56) L/h and peripheral Vd 1.039 (CV 69.32%) L. Peutic target attainment simulations demonstrated that a dosage of 50 mg/kg q 12 hours attained 100% fT > MIC 0.25 mg/L, group B streptococcal breakpoint.

CONCLUSIONS

We recommend ampicillin dosage 50 mg/kg q 12 hours for neonates with gestational age ≥32 weeks during the first week of life.

Paradoxical Antibiotic Effect of Ampicillin: Use of a Population Pharmacokinetic Model to Evaluate a Clinical Correlate of the Eagle Effect in Infants With Bacteremia

BACKGROUND

High doses of ampicillin are often used to achieve therapeutic drug concentrations in infants. A paradoxical antibiotic effect, often called the Eagle effect, occurs when increasing concentrations of antibiotic above a threshold results in decreased efficacy. It is unknown if infants treated with ampicillin are at risk for this paradoxical effect.

METHODS

We identified infants <28 days of age with Escherichia coli, Enterococcus or Streptococcus agalactiae (group B streptococcus) bloodstream infections from 1997 to 2012 and previously included in an ampicillin pharmacokinetic (PK) modeling study. We compared the odds of death for ampicillin dose, estimated time above the minimum inhibitory concentration (T > MIC) and PK parameters using separate logistic regression models. Adjusted logistic regression and Poisson models were used to calculate the odds of prolonged bacteremia ≥3 days and the duration of bacteremia, respectively, for dose, T > MIC and multiple PK parameters.

RESULTS

Among 1272 infants meeting inclusion criteria, odds of death 7 or 30 days after the positive blood culture were not consistent with a paradoxical effect across any of the dosing regimens or PK parameters evaluated. The odds of prolonged bacteremia was lowest at the lowest dose category and the lowest daily dose category but not associated with the area-under-the-concentration time curve from 0 to 24 hours, or the maximum or minimum concentrations at steady state. T > MIC of ≥50% of the dosing interval was associated with decreased duration of bacteremia and odds of prolonged bacteremia.

CONCLUSIONS

It is unlikely that a paradoxical antibiotic effect will have a clinical correlate when ampicillin is used for neonatal bacteremia. A T > MIC ≥50% decreased both duration of bacteremia and odds of prolonged bacteremia.

Platelets in neonates: central mediators in haemostasis, antimicrobial defence and inflammation

Platelets are not only centrally involved in haemostasis, but also in antimicrobial defence and inflammation. Since evaluation of platelet physiology in the particular patient group of preterm and term neonatal infants is highly restricted for ethical reasons, there are hardly any data available in healthy and much less in extremely immature or ill neonates. By summarising current knowledge and addressing both platelet researchers and neonatologists, we describe neonatal platelet count and morphology, report on previous analyses of neonatal platelet function in primary haemostasis and provide insights into recent advances in platelet immunology that considerably impacts our clinical view on the critically ill neonatal infant. We conclude that neonatal platelets, originating from liver megakaryocytes, substantially differ from adult platelets and may play a pivotal role in the pathophysiology of neonatal sepsis or intraventricular haemorrhage, both complications which seriously augment perinatal morbidity and mortality.

Evaluation and management of thrombocytopenic neonates in the intensive care unit

Thrombocytopenia is a very frequent problem among sick neonates, affecting up to 35% of all infants admitted to the neonatal intensive care unit (NICU), and serves as an important indicator of multiple clinical conditions. The cause of the thrombocytopenia is unclear in up to 60% of affected neonates. A clinical classification of thrombocytopenia is based on the time of presentation, early (≤72 hours of life) vs. late (>72 hours of life). Early thrombocytopenia is commonly associated with feto-maternal conditions, is most commonly caused by disorders associated with placental insufficiency, and is generally mild to moderate and resolves spontaneously within 7-10 days without any intervention. In contrast, neonates who develop late-onset thrombocytopenia frequently have bacterial sepsis or necrotizing enterocolitis. It is often severe (platelets <50,000/μL), prolonged and frequently requires multiple platelet transfusions. Platelet transfusions represent the only specific therapy currently available for most thrombocytopenic neonates, even though much evidence suggests that platelet transfusions are not benign. Many of the prophylactic platelet transfusions currently given to NICU patients are unnecessary, convey no benefits, and carry known and unknown risks. For this reason, pharmacological alternatives have been investigated as potential therapies for thrombocytopenia, but they still have limited use treating the common varieties of neonatal thrombocytopenia.

Results of a two-center, before and after study of piperacillin-tazobactam versus ampicillin and gentamicin as empiric therapy for suspected sepsis at birth in neonates ≤ 1500 g

OBJECTIVE

We changed from ampicillin and gentamicin (AG) to piperacillin-tazobactam (PT) for routine treatment of suspected early-onset sepsis. The rationale for this change included ototoxic and renal toxic effects of gentamicin, resistance to gentamicin in late-onset infections and emergence of ampicillin resistant Escherichia coli. A before and after study was designed before the start of PT administration to monitor whether PT was associated with altered outcomes within the 501 to 1500 g birth weight (Very Low Birth Weight) population.

METHOD

Both unmatched and matched comparisons of AG (2007 to 2009) and PT (2010 to 2011) exposed infants are reported. Cohorts were evaluated for initial effectiveness for congenital infections, subsequent morbidities and mortality.

RESULTS

Data from 714 patients were collected (499 AG and 215 PT in the unmatched and 301 AG and 183 PT in the matched cohorts). No significant differences in demographics or initial Apgar scores were noted in the unmatched or matched comparisons. There were significant differences in many of the outcomes of interest in both the matched and unmatched comparisons including less necrotizing enterocolitis (NEC) and less diaper rash with PT versus AG. The only adverse finding with PT was a small, but statistically significant elevation in alkaline phosphatase.

CONCLUSIONS

Use of PT as the initial empiric antibiotic for very low birth weight infants was not associated with adverse microbiological outcomes. There was no increase in major morbidities. Although outcomes were superior in ≤ 1500 g infants treated with PT when compared with AG, the study design does not allow us to conclude that others will see a reduction in NEC or diaper rash if they implement this alternative.

Platelets in the neonatal period: developmental differences in platelet production, function, and hemostasis and the potential impact of therapies

Thrombocytopenia is a common problem among sick neonates admitted to the neonatal intensive care unit. Frequently, platelet transfusions are given to thrombocytopenic infants in an attempt to decrease the incidence or severity of hemorrhage, which is often intracranial. Whereas there is very limited evidence to guide platelet transfusion practices in this population, preterm infants in the first week of life (the highest risk period for bleeding) are nearly universally transfused at higher platelet counts than older infants or children. To a large extent, this practice has been influenced by the observation that neonatal platelets are hyporeactive in response to multiple agonists in vitro, although full-term infants exhibit normal to increased primary hemostasis. This apparently paradoxical finding is due to factors in the neonatal blood that enhance the platelet-vessel wall interaction and counteract the platelet hyporeactivity. Relatively few studies have evaluated the platelet function and primary hemostasis of preterm infants, the subset of neonates at highest risk of bleeding and those most frequently transfused. Current understanding of platelet production and function in preterm and full-term neonates, how these factors affect their response to thrombocytopenia and their primary hemostasis, and the implications of these developmental differences to transfusion medicine are reviewed herein.

Thrombocytopenia in the first 24 hours after birth and incidence of patent ductus arteriosus

BACKGROUND

Experimental studies suggest that platelet-triggered ductal sealing is critically involved in definite ductus arteriosus closure. Whether thrombocytopenia contributes to persistently patent ductus arteriosus (PDA) in humans is controversial. This was a retrospective study of 1350 very low birth weight (VLBW; <1500 g) infants, including 592 extremely low birth weight (ELBW; <1000 g) infants.

METHODS

All infants who had a platelet count in the first 24 hours after birth and an echocardiogram performed on day of life 4 to 5 were included. The incidence of thrombocytopenia was analyzed in infants with and without PDA, and in those who did or did not undergo PDA intervention. The impact of thrombocytopenia, gestational age, birth weight, gender, and sepsis on PDA was determined by receiver operating characteristic curve, odds ratio, and regression analyses.

RESULTS

Platelet numbers within the first 24 hours after birth did not differ between VLBW/ELBW infants with and without spontaneous ductal closure. Platelet numbers were not associated with subsequent PDA treatment. Low platelet counts were not related to failure of pharma-cologic PDA treatment and the need for subsequent surgical ligation. Lower gestational age or birth weight, male gender, and sepsis were linked to the presence of PDA in VLBW infants on day of life 4 to 5.

CONCLUSIONS

Thrombocytopenia in the first 24 hours after birth was not associated with PDA in this largest VLBW/ELBW infant cohort studied to date. Impaired platelet function, due to immaturity and critical illness, rather than platelet number, might play a role in ductus arteriosus patency.