Umbilical artery catheters in the newborn: effects of heparin

Heparin for the prevention of intraventricular haemorrhage in preterm infants

BACKGROUND

Preterm birth remains the major risk factor for the development of intraventricular haemorrhage, an injury that occurs in 25% of very low birth weight infants. Intraventricular haemorrhage is thought to be venous in origin and intrinsic thromboses in the germinal matrix are likely to play a triggering role. Heparin activates antithrombin and promotes the inactivation of thrombin and other target proteinases. The administration of anticoagulants such as heparin may offset the increased risk of developing intraventricular haemorrhage and may also reduce the risk of developing parenchymal venous infarct, a condition known to complicate intraventricular haemorrhage.

OBJECTIVES

To assess whether the prophylactic administration of heparin reduces the incidence of germinal matrix-intraventricular haemorrhage in very preterm neonates when compared to placebo, no treatment, or other anticoagulants.

SEARCH METHODS

We searched the Cochrane Central Register of Controlled Trials (The Cochrane Library 2015), MEDLINE (1996 to 22 November 2015), EMBASE (1980 to 22 November 2015) and CINAHL (1982 to 22 November 2015), applying no language restrictions. We searched the abstracts of the major congresses in the field (Perinatal Society of Australia and New Zealand and Pediatric Academic Societies) from 2000 to 2015.

SELECTION CRITERIA

Randomised controlled trials, quasi-randomised controlled trials and cluster trials comparing the administration of early, i.e. within the first 24 hours of life, heparin in very preterm infants (gestational age < 32 weeks).

DATA COLLECTION AND ANALYSIS

For each of the included trials, two authors independently extracted data (e.g. number of participants, birth weight, gestational age, dose of heparin, mode of administration, and duration of therapy, etc.) and assessed the risk of bias (e.g. adequacy of randomisation, blinding, completeness of follow up). The primary outcomes considered in this review are intraventricular haemorrhage, severe intraventricular haemorrhage and neonatal mortality.

MAIN RESULTS

Two randomised controlled trials enrolling a total of 155 infants met the inclusion criteria of this review. Both trials compared low-dose heparin to the same solution without heparin in very preterm newborns requiring umbilical catheterisation. No trials were identified that specifically studied the use of heparin in infants at risk of germinal matrix-intraventricular haemorrhage.We found no differences in the rates of intraventricular haemorrhage (typical RR 0.93, 95% CI 0.61 to 1.41; typical RD -0.03, 95% CI -0.17 to 0.12; 2 studies, 155 infants; I² = 57% for RR and I² = 65% for RD), severe intraventricular haemorrhage (typical RR 1.01, 95% CI 0.46 to 2.23; typical RD 0.00, 95% CI -0.11 to 0.11; 2 studies, 155 infants; I² = 0% for RR and I² = 0% for RD) and neonatal mortality (typical RR 0.69, 95% CI 0.28 to 1.67; typical RD -0.04, 95% CI -0.14 to 0.06; 2 studies, 155 infants; I² = 28% for RR and I² = 50% for RD). We judged the quality of the evidence supporting these findings as very low (rates of intraventricular haemorrhage) and low (severe intraventricular haemorrhage and neonatal mortality) mainly because of limitations in the study designs and the imprecision of estimates. We found very few data on other relevant outcomes, such as bronchopulmonary dysplasia, pulmonary haemorrhage and patent ductus arteriosus; and no study assessing long-term outcomes (e.g. neurodevelopmental disability).

AUTHORS' CONCLUSIONS

There is very limited data on the effect of prophylactic administration of heparin on the incidence and severity of IVH in very preterm neonates. Both the identified trials used heparin in the context of maintaining umbilical line patency and not specifically as an agent to prevent germinal matrix-intraventricular haemorrhage. Given the imprecision of our estimates, the results of this systematic review are consistent with either a benefit or a detrimental effect of heparin and do not provide a definitive answer to the review question. Limited evidence is available on other clinically relevant outcomes.

Inadvertent relaxation of the ductus arteriosus by pharmacologic agents that are commonly used in the neonatal period

Premature birth and disruption of the normal maturation process leave the immature ductus arteriosus unable to respond to postnatal cues for closure. Strategies that advocate conservative management of the patent ductus arteriosus (PDA) in premature infants are dependent on identification of the symptomatic PDA and understanding the risk factors that predispose to PDA. Exposure of premature infants to unintended vasodilatory stimuli may be one of the risk factors for PDA that is under recognized. In this article, we summarize the clinical factors that are associated with PDA and review commonly used neonatal drugs for their vasodilatory properties. Data demonstrating relaxation of the ductus arteriosus by gentamicin and other aminoglycoside antibiotics, by cimetidine and other H2 receptor antagonists, and by heparin are provided as examples of neonatal therapies that have unanticipated effects that may promote PDA.

The evaluation and management of postnatal thromboses

In the pediatric population, neonates have the highest risk for thromboembolism (TE), most likely due to the frequent use of intravascular catheters. This increased risk is attributed to multiple risk factors. Randomized clinical trials dealing with management of postnatal thromboses do not exist, thus, opinions differ regarding optimal diagnostic and therapeutic interventions. This review begins with an actual case study illustrating the complexity and severity of these types of cases, and then evaluates the neonatal hemostatic system with discussion of the common sites of postnatal thrombosis, perinatal and prothrombotic risk factors, and potential treatment options. A proposed step-wise evaluation of neonates with symptomatic postnatal thromboses will be suggested, as well as future research and registry directions. Owing to the complexity of ischemic perinatal stroke, this topic will not be reviewed.

Thrombosis in the critically ill neonate: incidence, diagnosis, and management

Among children, newborn infants are most vulnerable to development of thrombosis and serious thromboembolic complications. Amongst newborns, those neonates who are critically ill, both term and preterm, are at greatest risk for developing symptomatic thromboembolic disease. The most important risk factors are inflammation, DIC, impaired liver function, fluctuations in cardiac output, and congenital heart disease, as well as exogenous risk factors such as central venous or arterial catheters. In most clinically symptomatic infants, diagnosis is made by ultrasound, venography, or CT or MRI angiograms. However, clinically asymptomatic vessel thrombosis is sometimes picked up by screening investigations or during routine imaging for other indications. Acute management of thrombosis and thromboembolism comprises a variety of approaches, including simple observation, treatment with unfractionated or low molecular weight heparin, as well as more aggressive interventions such as thrombolytic therapy or catheter-directed revascularization. Long-term follow-up is dependent on the underlying diagnosis. In the majority of infants, stabilization of the patients’ general condition and hemodynamics, which allows removal of indwelling catheters, renders long-term anticoagulation superfluous. Nevertheless, in certain types of congenital heart disease or inherited thrombophilia, long-term prophylaxis may be warranted. This review article focuses on pathophysiology, diagnosis, and acute and long-term management of thrombosis in critically ill term and preterm neonates.

Continuous heparin infusion to prevent thrombosis and catheter occlusion in neonates with peripherally placed percutaneous central venous catheters

BACKGROUND

Complications associated with peripherally placed percutaneous central venous catheters (PCVC) in neonates include mechanical complications (catheter thrombosis, occlusion or dislodgement) and infection. Strategies to prevent catheter thrombosis and occlusion include the use of heparin. However, heparin is known to be associated with complications such as bleeding and thrombocytopenia.

PRIMARY OBJECTIVE

To assess the effectiveness of heparin for prevention of catheter related thrombosis.

SECONDARY OBJECTIVES

To assess the effectiveness of heparin on catheter occlusion, duration of catheter patency, catheter related sepsis and complications associated with the use of heparin.

SEARCH STRATEGY

A literature search of MEDLINE, EMBASE, CINAHL from their inception to December 2007, The Cochrane Library (Issue 4, 2007) and abstracts from the annual meetings of the Pediatric Academic Societies was performed without language restrictions.

SELECTION CRITERIA

Randomized or quasi-randomized clinical trials of neonates where heparin infusion was compared to placebo or no treatment for prevention of any of the complications related to peripherally placed PCVC were included.

DATA COLLECTION AND ANALYSIS

The methodological quality of included trials was assessed using criteria for masking of randomization, masking of intervention, completeness of follow-up and masking of outcome measurement. Data on relevant outcomes were extracted and the effect size was estimated by calculating relative risk (RR), risk difference (RD) and associated 95% confidence intervals (CI).

MAIN RESULTS

Three randomized trials were identified. Two trials of adequate methodology met the eligibility criteria. These studies included 267 neonates. There was reduced risk of catheter occlusion (typical RR 0.28, 95% CI 0.15, 0.53, NNT 5, 95% CI 3, 8). There was no statistically significant difference in the duration of catheter patency when analyzed as continuous data; however, in one study survival analyses identified benefit with heparin (adjusted hazard ratio 0.55, 95% CI 0.36, 83); (Shah 2007). This could be due to higher incidence of elective removal of catheters in neonates at the completion of therapy in the heparin group (63% vs. 42%; p = 0.002) (Shah 2007). There was no statistically significant differences in the risk of thrombosis (typical RR 0.93, 95% CI 0.58, 1.51), catheter related sepsis (typical RR 1.96, 95% CI 0.50, 7.60), or extension of intraventricular hemorrhage (typical RR 0.87, 95% CI 0.25, 3.03) between the two groups.

IMPLICATIONS FOR PRACTICE

Prophylactic use of heparin for peripherally placed PCVC allows a greater number of infants to complete their intended use (complete therapy) by reducing occlusion. Evidence from this systematic review support the prophylactic use of heparin for PCVC in neonates at a dose of 0.5 IU/kg/hr.

IMPLICATIONS FOR RESEARCH

None of these studies was powered to evaluate a lower incidence rate of adverse events. If this therapy is adopted in routine practice, monitoring of side effects is indicated.

A randomized, controlled trial of heparin versus placebo infusion to prolong the usability of peripherally placed percutaneous central venous catheters (PCVCs) in neonates: the HIP (Heparin Infusion for PCVC) study

BACKGROUND

Mechanical and infectious complications shorten the effective duration of peripherally inserted central venous catheters. Heparin use to prevent such complications and prolong the usability of peripherally inserted central venous catheters is inconclusive.

OBJECTIVE

Our goal was to evaluate the effectiveness of heparin in prolonging the usability of peripherally inserted central venous catheters in neonates.

DESIGN/METHODS

We performed a multicenter, randomized, controlled trial of heparin infusion (0.5 U/kg per hour) versus placebo for peripherally inserted central venous catheters in neonates. The primary outcome was duration of catheter use. Secondary outcomes were occlusion, catheter-related sepsis, thrombosis, and adverse effects of heparin. To detect a 168-hour (1-week) difference in the duration of catheter use, 192 patients were needed. Kaplan-Meier and Cox regression analyses were performed.

RESULTS

A total of 201 neonates were enrolled (heparin group: n = 100; control group: n = 101). Baseline demographics were similar between the groups. Duration of catheter use was longer in the infants in the heparin versus the placebo group. Study center, gender, birth weight, and type and position of the catheter were not predictors of duration of catheter use. For those in the heparin versus the placebo group, the incidence of elective catheter removal (therapy completed) was 63% vs 42%, of occlusion was 6% vs 31%, of thrombosis was 20% vs 21%, and of catheter-related sepsis was 10% vs 6%, respectively. No adverse events were noted.

CONCLUSIONS

Heparin infusion prolonged the duration of peripherally inserted central venous catheter usability, which permitted a higher percentage of neonates to complete therapy without increasing adverse effects.

Clinical measures to preserve cerebral integrity in preterm infants

Impaired psychomotor development, often anteceded by major intraventricular hemorrhage or periventricular leukomalacia, constitutes the most important long-term morbidity of very preterm infants. We reviewed randomized controlled trials aimed at reducing the incidence of brain damage, as detected by ultrasound, or neurodevelopmental impairment during follow-up of preterm infants. Preliminary reports of reduced rates of intraventricular hemorrhage obtained with administration of fresh frozen plasma, ethamsylate, phenobarbitone, or morphine have not been confirmed in subsequent larger trials. Early administration of indomethacin may reduce intraventricular hemorrhage without affecting long-term outcome. Pancuronium, inositol, and vitamin E decreased intraventricular hemorrhage rates but later psychomotor development was not examined. Thyroxin supplementation failed to improve neurodevelopmental outcome while protein enrichment of formula and individualized developmental care appear to be beneficial. The largest reductions in cerebral palsy and neurodevelopmental impairment were achieved by avoidance of postnatal steroids. This finding emphasizes the need to include these late endpoints in any randomized trial involving preterm infants.

Umbilical artery catheters in the newborn: effects of heparin

BACKGROUND

This section is under preparation and will be included in the next issue.

OBJECTIVES

To determine whether the use of heparin in fluids infused through an umbilical arterial catheter in newborn infants influences the frequency of clinical ischemic events, catheter occlusion, aortic thrombosis, intraventricular hemorrhage, hypertension, death, or the duration of catheter usability.

SEARCH STRATEGY

Randomized and quasi randomized controlled trials of umbilical catheterization use were obtained from the following sources: 1. Effective Care of the Newborn Infant, edited by JC Sinclair and MB Bracken. 2. Medline Search using Melvyl Medline Plus and the keyword headings 'Umbilic#', 'Catheter#' and subject heading 'Infant, Newborn' 3. Search of personal data files

SELECTION CRITERIA

Randomized trials in newborn infants of any birthweight or gestation. Comparison of heparinised to non heparinised infusion fluids, including comparison of heparin in the infusate to heparin just in the flush solution. Clinically important end points such as catheter occlusion or aortic thrombosis.

DATA COLLECTION AND ANALYSIS

There were five randomized controlled trials retrieved. All gave details of the incidence of catheter occlusion. Two also reported the incidence of aortic thrombosis. The intervention was reasonably consistent: heparin in the infusate at a concentration of 1 unit/mL was investigated in all trials except one which used a concentration of 0.25 units/mL. Studies generally included both term and preterm infants.

MAIN RESULTS

Heparinization of the infusate decreases the incidence of catheter occlusion but does not affect the frequency of aortic thrombosis. Heparinization of the flush solution is not an adequate alternative. There does not appear to be an effect on frequency of intraventricular hemorrhage, death or clinical ischemic phenomena.

REVIEWER'S CONCLUSIONS

Heparinization of the fluid infused through an umbilical arterial catheter decreases the likelihood of umbilical arterial catheters occluding. The lowest concentration tested so far (0.25 units/mL) has been shown to be effective. Heparinization of flushes without heparinizing the infusate is ineffective. The frequency of aortic thrombosis has not been shown to be affected; however, the confidence intervals for this effect are very wide. The frequency of intraventricular hemorrhage has not been shown to be affected by heparinization of the infusate, but again the confidence intervals are very wide and even a major increase in the incidence of grade 3 and 4 intraventricular hemorrhage would not have been detected.