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Abstract & Commentary
In a randomized trial, 169 patients admitted to a cardiovascular-surgical or medical-surgical ICU were assigned to 4 groups: 1) fast flush as needed and waste blood sampling; 2) fast flush as needed and nonwaste blood sampling; 3) fast flush every 4 hours and waste blood sampling; and 4) fast flush every 4 hours and nonwaste blood sampling. Patients were followed for 72 hours or until their radial artery catheters became nonpatent. All received nonheparinized, isotonic sodium chloride as the flush solution. Arterial catheter patency was evaluated by 2 criteria: acceptable results on a square waveform test and free back-flow of blood within 1 second. When waste sampling was used, 1 mL of blood was withdrawn to waste before obtaining the needed blood sample. When nonwaste sampling was used, 5 mL of isotonic normal saline was withdrawn and reinfused after the sample was obtained. To ensure uniform test conditions, inflation pressure was maintained at 300 mg Hg and corrected if insufficient or too high before testing catheter patency. The patients were 62.0 ± 13.3 years of age and most (64.5%) subjects were men.
In total, 23 (13.6%) catheters became nonpatent. Of these, most (62%) became nonpatent within 32 hours of placement. Duration of patency did not differ between catheters maintained with a fast-flush q 4 hours or flushed as needed or between catheters according to the method of blood sampling. However, patients with catheter insertion sites ³ 3 cm above the radiocarpal joint were 4.23 times (P = 0.01) more likely to have nonpatent catheters within 72 hours of insertion. In addition, women were 3.05 times more likely than men to have nonpatent catheters (P = 0.02). With insertion sites ³ 3 cm above the bend of the wrist, nonpatency was 7.3 times more likely in women than in men (P < 0.001). Most patients (84%) received anticoagulants or thrombolytics at least once during the 72 hours of monitoring. Those who did not receive these medications were 2.8 times more likely (P = 0.05) than patients who received these drugs to have nonpatent catheters (Kaye J, et al. Patency of radial arterial catheters. Am J Crit Care. 2001;10:104-111).
Comment by Leslie A. Hoffman, PhD, RN
Radial artery catheters are routinely used in critically ill patients to monitor blood pressure and to obtain arterial blood gas samples. Maintaining catheter patency is important because readings from these devices are used to titrate vasoactive drugs and to regulate blood pressure and heart rate. In prior studies, problems linked with loss of patency have included the size, length, and duration of use of the catheter and gender of the patient.
The major finding of this study was that placement of the catheter relative to the radiocarpal joint had a significant influence on the duration of patency in the first 72 hours after insertion. Site location was measured as the distance in centimeters from the radiocarpal joint at the base of the thumb to the insertion site of the catheter. Kaye and colleagues speculated that movement of the wrist may have caused a pumping action that aided blood flow and, therefore, contributed to keeping the catheter patent. This finding is particularly noteworthy because the catheters were used for a relatively short time. Mean duration of use was 30.7 hours, with a range of 3.7-72 hours. In contrast, neither the flush method (q 4 hours, as needed) or blood-sampling method (waste, nonwaste) had a significant effect on catheter patency. As previously reported, women were more likely than men to have nonpatent catheters, presumably due to smaller vessel size.
Findings of this study suggest that a simple strategy—placing radial artery catheters as close to the bend of the wrist as possible—may minimize the risk of losing patency. The study deserves replication to verify this finding in other sites and a larger sample of patients with varying underlying conditions.