Incidence and predictors of indwelling arterial catheter-related thrombosis in children.

BACKGROUND: Indwelling arterial catheters (IACs) are used for monitoring and blood sampling purposes in intensive care units. Very limited information is available on the incidence and risk factors of IAC-related thrombosis in children. OBJECTIVE: To investigate the incidence and predictors of IAC-related thrombosis in a tertiary care pediatric hospital. METHODS: For a period of 12 months, detailed information was prospectively recorded for all consecutive children requiring IACs. RESULTS: Six hundred and fifteen IACs were placed in a total of 473 children at a median age of 0.56 years for a total of 47440.84 catheter hours. Of the 615 IACs, 418 (68%) were placed in the radial artery, 137 (22%) in the femoral artery, 26 (4%) in the umbilical artery, 11 (2%) in the brachial artery, and 23 (3.7%) in another artery. Thrombosis occurred in 20 cases, reflecting an overall incidence of 3.25%. Eighteen of the 20 IAC-related thrombi were located in the femoral arteries, reflecting a relative incidence of 13% (18/137). Newborn age, lower body weight, low cardiac output and increased hematocrit were significantly related with an increased risk of femoral artery thrombosis. In logistic regression analysis, younger age (P<0.001, odds ratio 6.51) was independently associated with an increased thrombotic risk. CONCLUSIONS: This study demonstrates that arterial thrombosis occurs with an increased incidence in children requiring IACs in the femoral location. Younger age is independently associated with an increased risk of thrombosis. The radial location is safe, and should be preferred to the femoral location.

Advantages and disadvantages of different nasal CPAP systems in newborns.

OBJECTIVE: To compare three different systems of continuous positive airway pressure (CPAP): the naso-pharyngeal tube and two-prong systems in newborns, focusing on duration of CPAP, side effects and cost. DESIGN: Randomized clinical study. PATIENTS: Between July 2000 and September 2001 newborns were randomized to three different CPAP systems. Forty infants in two weight groups (>2500 g and 1250-2500 g; 20 patients in each group) were included. RESULTS: In the group >2500 g the median duration of CPAP was 1.1 days (range 0.25-14.3 days). The median time on a naso-pharyngeal CPAP was 1 day (range 0.25-14.3 days), on Hudson prongs 1.6 days (range 0.5-3.3 days) and on the Infant Flow system 0.7 days (range 0.3-13.6 days; p>0.05 for comparison between groups, Fisher's exact test). With naso-pharyngeal CPAP, 2 patients developed moderate nasal injuries. On Hudson, 2 patients developed moderate and three mild nasal injuries. One patient on the Infant Flow showed mild and one moderate nasal injuries. In the weight group 1250-2500 g the median duration of CPAP was 1.1 days (range 0.1-7.0 days). The median time on the naso-pharyngeal tube was 0.9 days (range 0.1-7 days), on Hudson prongs 1.1 days (range 0.7-6.6 days) and on the Infant Flow system 1.3 days (range 0.25-5.9 days; p>0.05 for comparison between groups, Fisher's exact test). With a naso-pharyngeal tube, one infant developed mild and one moderate nasal injuries. On Hudson prongs, two had moderate nasal injuries. On Infant Flow, one newborn showed a severe nasal injury and two mild injuries. None of the patients developed a pneumothorax. CONCLUSION: The naso-pharyngeal tube is an easy, safe and economical CPAP system usable with every common ventilator. For very low birth weight newborns, a prong system may have advantages.

Measurement of activated clotting time in children--comparison of the Celite i-STAT ACT with the Medtronic ACT II.

BACKGROUND: To evaluate a recently introduced blood-saving method for the measurement of activated clotting time (ACT), the Celite i-STAT ACT, by comparing the values obtained with those from the widely used Medtronic ACT II device. METHODS: In a prospective clinical study, we compared ACT values from the i-STAT device with the Medtronic ACT II device in 60 paediatric, interventional, cardiac catheterization procedures necessitating prophylactic heparinization. Blood samples were pair-analyzed using two i-STAT analyzers and one Medtronic ACT II device with double-tube-cartridges before and after heparinization. Data were compared using Bland-Altman bias analysis, Student's t-test and simple regression analysis. RESULTS: Bias and precision between the Medtronic ACT II and the i-STAT ACT values was -5.4 +/- 26.3. The i-STAT and Medtronic ACT II values were similar before heparinization (P = 0.22), but i-STAT ACT values became significantly longer than Medtronic ACT II values after heparinization (P = 0.021). The increase of ACT after heparinization was greater (median 86.3; range 40-187 s) in the i-STAT analyzer than in the Medtronic ACT II analyzer (median 73.0; range 19-235.5 s). Increase in ACT values was inversely affected by intraoperative haemoglobin concentration in the Medtronic ACT II analyzer (P = 0.001) but not in the i-STAT analyzer. CONCLUSION: Activated clotting times obtained from the Celite i-STAT ACT and the Medtronic ACT II demonstrated poor agreement. The technical principles are quite different and the two methods showed diverse susceptibility to intraoperative haemoglobin concentration. Users have to be aware of technique-specific ACT target ranges and their confounders, which need to be provided by the manufacturers.

Variability in infusion pressure and continuous flow rate delivered from pressurized bag pump flush systems.

Using 10 different infusion bag pressure pumps, indicated manometer pressures were compared with measured infusion pressures proximal to the flow-regulating device in an in vitro experiment. Flow rates delivered through the flow-regulating device were gravimetrically measured at different monitored pressure levels. Significant differences were found between manometer and measured infusion pressures among the tested pressure bagpumps (e.g. 500 ml bag volumepressurized to 300 mmHg manometerpressure: 219.6 +/- 7.8 to 407.2 +/- 2.7 mmHg). The infusion pressures were additionally affected by the vertical level of the infusion bag pump and by the volume of the infusion bag. Flow rates delivered through the flow-regulating device were directly correlated to the measured infusion pressure (r2= 0.9926). Differences inflow rates can have a considerable impact on maintaining catheter patency and avoidance of fluid overload and retrograde flushing into the central arterial circulation in neonates and small children. A simple manoeuvre using the invasive pressure transducer allows monitoring and adjustment of the infusion pressure in the clinical setting.

Somatostatin: a new therapeutic option for the treatment of chylothorax.

BACKGROUND: The standard treatment of chylothorax in pediatric intensive care today includes conservative therapy with fat-free nutrition, total parenteral nutrition and, if this is not successful, operative treatment (pleurodesis, ligation of the duct, pleuroperitoneal shunt). PATIENTS: We describe four patients who were not in a suitable condition for operative treatment and who were treated with continuous infusion of somatostatin. RESULTS: In three patients, chylothorax ceased with the continuous somatostatin infusion without side effects. One patient was treated without success. CONCLUSIONS: Somatostatin is a therapeutic option for treatment of chylothorax and could reduce surgical intervention and hospitalization time, as well as allow earlier enteral feeding.

Always flush the sampling port before flushing the arterial cannula in pediatric patients.

BACKGROUND: Blood sampling from arterial lines is a frequent event in anesthesia and critical care. To avoid clot formation, both the stopcock outlet and the cannula must be flushed after sampling. We investigated in a bench experiment whether fluid flow through the cannula is affected by the sequence of flushing procedures. METHODS: Continuity of fluid delivery from a vascular cannula was gravimetrically determined using two different flushing techniques with either a syringe pump flush system or a bag flush system. The procedures comprised first flushing the stopcock towards the cannula and then towards the stopcock sampling outlet or the reverse order. Experiments were repeated in triplicate and two sets for each flushing system at hydrostatic pressures of 37 mm Hg and 74 mm Hg. RESULTS: The main finding of the study was that flushing the stopcock towards the outlet after flushing the cannula resulted in considerable retrograde aspiration volumes and zero flow times, in particular in combination with syringe pump flush systems. At a hydrostatic pressure of 74 mm Hg, the observed zero flow time at the cannula tip amounted to (mean+/-SD) 0.1+/-0.01 min with the bag flush system and 7.7+/-0.5 min with the syringe pump flush system. The related retrograde aspiration volumes were 2.2+/-0.7 microl with the bag system and 30.0+/-2.0 microl with the syringe pump system. No backflow was recorded when the stopcock was first flushed to ambient pressure and then afterwards towards the cannula. CONCLUSION: Opening a flush system to ambient pressure affects the continuity of fluid delivery, particularly when using syringe pump flush systems. After blood sampling, the stopcock outlet should be flushed first followed by cannula flushing.

Syringe size and flow rate affect drug delivery from syringe pumps.

PURPOSE: To evaluate the effect of syringe size and infusion rate on drug delivery after vertical displacement of syringe pumps. METHODS: Four syringes (10 ml, 20 ml, 30 ml, 50 ml) were studied at three infusion speeds (2 ml x hr(-1), 1 ml x hr(-1) and 0.5 ml x hr(-1)). Fluid delivery was measured gravimetrically using an electronic balance. Aspiration volume (amount of fluid retracted into the syringe-infusion line assembly) and zero-drug delivery time (time between the lowering of the syringe pump and reattainment of the initial weight) were determined after lowering the syringe pump 130 cm or 50 cm. Then, infusion bolus was measured after elevating the pump to its initial position. Syringe compliance was calculated from the occlusion release bolus at an occlusion pressure of 300 mmHg. RESULTS: Zero-drug delivery time, aspiration volume and infusion bolus increased with syringe size (P < 0.0001). At 0.5 ml x hr(-1), a zero-drug delivery time of 29.7 +/- 0.6 min was recorded for the 50 ml syringe and 5.5 +/- 0.15 min for the 10 ml syringe. As infusion rates increased, zero-drug delivery times decreased following a 1/x ratio. Zero-drug delivery time highly correlated with calculated syringe compliance (Pearson's r = 0.97, P < 0.001), which was closely related to syringe plunger area (R2 = 0.93, P < 0.001). CONCLUSIONS: Vertical displacement of syringe pumps causes flow irregularities which correlate directly with syringe size and indirectly with infusion rate. Extreme vertical maneuvering of syringe pumps should be avoided. Infusion rates > or = 1 ml x hr(-1) and low-compliant, small syringes are recommended when highly concentrated drugs are administered.

Isolation and nucleotide sequence determination of a gene encoding a heat-stable enterotoxin of Escherichia coli.

A gene encoding a heat-stable enterotoxin (ST) from an Escherichia coli strain isolated from a human with diarrhea was cloned and characterized by nucleotide sequence analysis. The gene was found to be partially homologous to a previously characterized ST gene from an E. coli strain of bovine origin. Hybridization studies showed that most ST-producing strains of E. coli isolated from humans with diarrhea possess genes highly homologous to either the ST gene from the bovine strain or the ST gene characterized in the present study.