Umbilical artery catheters in the newborn: effects of catheter materials

Cover Sheet

Short title: Umbilical artery catheters: catheter materials
Reviewer(s): Barrington KJ

Date of most recent amendment: 23/11/1998
Date of most recent substantive amendment: 18/11/1998
Date next stage expected: / /

Contact
Dr Keith Barrington
Associate Professor
Pediatrics
University of California, San Diego
200 W Arbor Dr
San Diego
CA USA
92103-8774
Telephone 1: 1 619 543 7586
Telephone 2: 1 619 543 3759
Facsimile: 1 619 543 3812
E-mail: kbarrington@ucsd.edu

Sources of support for the review

Acknowledgements

Potential conflict of interest
None

Abstract

Objective

To determine whether the material used for construction of an umbilical arterial catheter influences the frequency of ischemic events, aortic thrombosis, mortality or necrotising enterocolitis in newborn infants.

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 studies in newborn infants of any birthweight or gestation.
Comparison of different catheter materials.
Clinically important end points such as ischemic events, aortic thrombosis, or catheter occlusion.

Data collection & analysis

One non-randomized and one randomized study were retrieved.

Main results

There were no significant effects of substituting a heparin bonded polyurethane catheter for the standard PVC catheter. The non-randomized study suggested that there may possibly be a benefit of using a catheter constructed from Silastic, with a reduction in aortic thrombosis.

Conclusions

There are no demonstrated clinically relevant differences in outcomes between the use of PVC catheters and other materials. Therefore, other considerations such as price and ease of availability may dictate the catheter chosen. An adequately powered randomized comparison of silastic to PVC should be performed.

Background

Umbilical arterial catheters (UACs) are among the most commonly used monitoring methodologies in neonatal intensive care. There seems to be significant variance between neonatal intensive care units in exactly how these catheters are used. This variance involves heparin dosing, catheter materials and catheter design, and positioning of the catheter. Immediately after insertion of a UAC local vascular compromise is frequently evident, usually in the form of blue or white toes, but occasionally with more severe and extensive ischemic manifestations. Aortic thrombi and renal ischemia have also been described. Some epidemiologic and case control studies have also shown that use of umbilical artery catheterization is statistically associated with the later development of necrotising enterocolitis. In order to minimize these morbidities some aspects of the use of UACs have been subjected to a small number of randomized control trials.

This review will analyze the data regarding the rates of complications relating to the material from which the catheter is constructed. Some newer plastics (carbon polymers) are said to be less thrombogenic than standard polyvinylchloride (PVC) and catheters may also be coated with heparin to further reduce "thrombogenicity". Heparin coated catheters may also decrease sepsis rates by inhibiting bacterial adherence to the catheter (Mermel 1993, Appelgren 1996). Thus, the availability of heparin bonded catheters made from newer plastics requires clinical testing to ensure that the safest catheters are used. In adult intensive care it has also been shown that bonding of antimicrobial agents to the surface of the catheter decreases catheter-associated sepsis. Both cefazolin (Kamal 1991) and chlorhexidine/silver sulphadiazine (Maki 1991) have been investigated and appear to be effective.

Other materials such as "Silastic", a silicon based polymer, are used for construction of many different medical devices, with the putative advantage of reduced biologic interactions. Such materials could also potentially decrease complication rates from umbilical arterial catheterization. Some of the early animal studies of silastic catheters showed a reduction in thrombosis rates (Welch 1974); however, others were unable to show any effect (Andrews 1973). There are no clear benefits in adults from the use of silastic catheters (Reed 1995).

This review updates the existing review of Umbilical artery catheters: catheter materials, which was published in The Cochrane Library, Disk Issue 1 1998 (Barrington 1998).

Objectives

To determine whether the material from which the umbilical arterial catheter is constructed influences morbidity with the use of umbilical artery catheters in terms of mortality, necrotising enterocolitis, aortic thrombosis, or clinically recognized ischemic phenomena.

Materials and Methods

Criteria for considering studies for this review

Types of studies
Randomized and quasi randomized clinical studies were selected. Clinically relevant outcomes were collated, with survival and long term disability being given the greatest weight. Both term and preterm infants were included.

Types of participants
Newborn infants, both preterm and term. Entry criterion was simply the "need" for a catheter, as defined by the attending medical staff.

Types of intervention
Random assignment of catheters made from different materials.

Types of outcome measures
Clinical ischemic compromise, aortic thrombosis, catheter occlusion. Duration of catheter usability.

Search strategy for identification of studies

The original search was completed in November 1997, and has been updated in November 1998.

Methods of the review

Reports were first reviewed to determine whether there was a concurrent control group, and discarded if not. The method of assignment to control and intervention groups was then determined and, if not random or quasi random, then the trial was discarded.

Each identified trial was assessed for methodological quality with respect to a) masking of allocation b) masking of intervention c) completeness of follow-up d) masking of outcome assessment.

Statistics: For categorical outcomes, typical estimates for relative risk and risk difference were calculated. For outcomes measured on a continuous scale, typical estimates for weighted mean difference were calculated. 95% confidence intervals were used. A fixed effect model was assumed.

Description of studies

The original search strategy retrieved 849 articles. These were further reduced by restricting the search by use of the terms prospective, random#, control#, comparative or clinical. When studies of animal subjects and of epidural catheterization were also removed, 233 reports remained. The abstract of each was read individually to determine if there was a possibility that the papers were reporting randomized prospective controlled trials. This final examination revealed 2 trials investigating catheter materials. The updated search in November 1998 revealed no new randomized trials of catheter materials.

Only 1 of the 2 trials which were detected was randomised (Jackson 1987). The authors compared standard PVC to heparin bonded polyurethane in 125 term and preterm infants in a single center over 16 months. This study was unblinded and used random assignment using sequentially numbered sealed envelopes. Catheter group assignment was not stratified by weight but well balanced groups were achieved. Catheter size was either 3.5 or 5 Fr at the discretion of the physician. Catheters were placed in a high position. Heparin was not used in the infusate and a small quantity was used in the flushing procedure. The primary outcome variable was "clots or associated complications" with aortic thrombosis being detected by routine ultrasound at about 3 and about 11 days of age. Secondary outcomes were hypertension, persistent blanching of the feet or legs, duration of useful catheter function. There were originally 144 infants randomized, 19 were excluded after randomization (16 of them because catheter insertion was unsuccessful, 3 because the physician changed his mind) to leave 125 in which a catheter was inserted; all data are reported from these 125 infants. There was a decrease in numbers between study entry and ultrasound examination which appears to be because many catheters were removed before the scheduled ultrasound examination dates; thus 114 early ultrasounds were performed and 105 at the later time. Other outcomes, such as hypertension and clinical ischemic compromise were reported on almost all the infants (122/125).

Boros et al (Boros 1975) compared the incidence of aortic thrombosis by aortography in 10 infants with PVC catheters and 10 infants with a silastic catheter. The study was not randomized; therefore, this study was excluded from the analysis. Contrast aortograms were performed at the time of removal of the catheter. During the period of the study there were other infants in the same NICU who had silastic catheters and were not included in the study. It appears that the reason for being included in this report was the performance of an aortogram. The aortograms showed that nine of the infants with PVC catheters had a thrombus compared to one of the infants with a silastic catheter.

Methodological quality of included studies

Jackson 1987
Masking of allocation:
Yes, Opaque sequentially numbered envelopes opened after enrollment.
Masking of intervention:
No, catheters have a different appearance.
Completeness of follow-up:
Yes
Masking of outcomes:
Most of the outcomes were not masked. Abdominal sonograms were read by radiologists masked as to group assignment.
Other comments:
Clear description of determination of required sample size; this was actually achieved. Hypothesized a reduction in incidence of "aortic clots or associated complications" from 45% to 20%.

Results

Jackson 1987 showed no benefit of substituting a heparin bonded polyurethane catheter for the usual PVC catheter in terms of the incidence of aortic thrombosis in this trial involving 125 infants. RR for aortic thrombosis after a mean of 11.1 days was 0.63 (95% CI 0.34, 1.18). There was also no statistically significant effect on other outcomes: RR for persistent hypertension was 5.00 (95% CI 0.24, 102.4) and for clinical vascular compromise was 1.00 (95% CI 0.45, 2.23). The results do not clearly describe how many of the catheters themselves became occluded, although the duration of useful catheter function was said to be not different between groups.
Other important outcomes such as mortality, intraventricular hemorrhage, necrotising enterocolitis and sepsis were not reported.

Discussion

This review provides no basis for choosing any catheter material over standard PVC at the present. As complications of umbilical arterial catheterization are frequent, further research into this issue is warranted. Heparin bonded catheters may be associated with a lower risk of infections in other populations. This is an important outcome which was not reported in Jackson's paper, and should be further investigated.
Silastic catheters could potentially have a much lower incidence of aortic thrombi than PVC; however, the research design of Boros 1975 allows many potential biases which should be resolved by further study.

Conclusions

Implications for practice

Implications for research

Introduction of newer catheter materials should be compared to PVC in prospective randomized controlled trials. Silastic catheters, which are currently readily available, have not been demonstrated by reliable studies to be an improvement over PVC, and warrant adequately powered prospective investigation.

Characteristics of Included Studies

Study: Jackson 1987
Method: Single center randomised study. Masking of allocation; Yes
Masking of intervention; No
Completeness of follow-up; Yes
Masking of outcomes; No
Participants: 144 term and preterm infants
Interventions: Heparin bonded polyurethane catheter compared with standard PVC catheter
Outcomes: Aortic thrombosis, blanching of feet or legs, persistent hypertension.

Characteristics of Excluded Studies

Study Identifier: Boros 1975
Reason for exclusion: Non- randomized study, catheter type determined by availability of catheter and house staff preference.

References to Studies

Section 1. References to studies included in this review

Jackson JC, Truog WE, Watchko JF, Mack LA, Cyr DR, van Belle G. Efficacy of thromboresistant umbilical artery catheters in reducing aortic thrombosis and related complications. J Pediatr 1987;110:102-105.

Section 2. References to studies excluded from this review

Boros SJ, Thompson TR, Reynolds JW, Jarvis CW, Williams HJ. Reduced thrombus formation with silicone elastomere (silastic) umbilical artery catheters. Pediatrics 1975;56:981-986.

Other References

Section 5. Additional references

Andrews E, Hughes H. Thromboembolic sequelae to indwelling silastic cannulas in sheep arteries. J Biomed Mater Res 1973;7:137-144.

Appelgren P, Ransjo I, Bindslev L, et al. Surface heparinization of central venous catheters reduces microbial colonization in vitro and in vivo: Results from a prospective, randomized trial. Crit Care Med 1996; 24:1482-9.

Kamal GD, Pfaller MA, Rempe LE, Jebson PJ. Reduced intravascular catheter infection by antibiotic bonding; a prospective randomized controlled trial. JAMA 1991;265:2364-2368.

Maki DG, Wheeler SJ, Stolz SM, Mermel LA. Prevention of central venous catheter-related bloodstream infection by use of an antiseptic-impregnated catheter. A randomized, controlled trial. Ann Intern Med 1997;127:257-266.

Mermel LA, Stolz SM, Maki DG. Surface antimicrobial activity of heparin-bonded and antiseptic-impregnated vascular catheters. J Infect Dis 1993;167:920-924.

Reed CR, Sessler CN, Glauser FL, Phelan BA. Central venous catheter infections: concepts and controversies. Intensive Care Med 1995;21:177-183.

Welch G, McKeel D, Silverstein P, Walker H. The role of catheter composition in the development of thrombophlebitis. Surg Gynecol Obstet 1974;138:421-424.

Section 6. Previously published versions of this review

Barrington KJ. Umbilical artery catheters: catheter materials (Cochrane Review). In: The Cochrane Library, Issue 1, 1998. Oxford: Update Software.

Table of Comparisons

01.00.00 Heparin bonded polyurethane catheter compared to polyvinylchloride

01.01.00 Persistent hypertension (RR)

01.01.00 Persistent hypertension (RD)

01.02.00 Aortic thrombosis after 3.5 (SD 1.2) days (RR)

01.02.00 Aortic thrombosis after 3.5 (SD 1.2) days (RD)

01.03.00 Aortic thrombosis after 11.1 (SD 2.3) days (RR)

01.03.00 Aortic thrombosis after 11.1 (SD 2.3) days (RD)

01.04.00 Clinical vascular compromise (RR)

01.04.00 Clinical vascular compromise (RD)