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A discard volume of twice the deadspace ensures clinically accurate arterial blood gases and electrolytes and prevents unnecessary blood loss.

Abstract：

OBJECTIVE:To determine the blood discard volume, as a multiple of deadspace, that is required for accurate arterial blood gas and electrolyte testing from arterial catheters. DESIGN:Prospective, controlled, crossover trial. SETTING:Eighteen-bed intensive care unit of a metropolitan teaching hospital. PATIENTS:A total of 84 critically ill patients with a 20-gauge, radial arterial cannulae, pressure monitoring transducer set, and stable oxygenation. INTERVENTIONS:System deadspace (priming volume from sampling port to catheter tip) was established. Patients had six 0.5-mL arterial blood samples taken sequentially in random order using discard volumes of 1, 1.5, 2, 2.3, and 3.6 times the deadspace (experimental values) and 5.5 times the deadspace (control). MEASUREMENTS AND MAIN RESULTS:Samples were analyzed for Pao(2), Sao(2), pH, Paco(2), HCO(3)-, Na+, and K+. We performed repeated-measures analysis of variance with post hoc linear contrasts and compared mean experimental and control values. The smallest discard volumes that provided measurements that were statistically equal to control were twice the deadspace (Pao(2), p =.563; Sao(2), p =.371) and 3.6 times the deadspace (pH, p =.107; Paco(2), p=.519; HCO(3)-, p =.10). All discard volumes tested provided results that were statistically different from control for Na+ (p <.003) and K+ (p <.001). CONCLUSIONS:Many results were statistically different from control, although the actual discrepancies were very small. At clinically relevant levels of measurement, there was minimal variation between values obtained after a discard volume of twice the deadspace and control values. The level of error was clinically acceptable and within or close to the precision limits of the blood gas analyzer. Slight fluctuation in patient variables during sampling could also have contributed to the error. A blood discard volume of twice the deadspace is recommended for all variables. This will provide clinically accurate results and avoid the deleterious effects of unnecessary blood loss.

journal_name

Crit Care Med

journal_title

Critical care medicine

authors

Rickard CM,Couchman BA,Schmidt SJ,Dank A,Purdie DM

doi

10.1097/01.CCM.0000063448.98777.EF

subject

Has Abstract

pub_date

2003-06-01 00:00:00

pages

1654-8

issue

eissn

0090-3493

issn

1530-0293

journal_volume

pub_type

临床试验,杂志文章

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A discard volume of twice the deadspace ensures clinically accurate arterial blood gases and electrolytes and prevents unnecessary blood loss.