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Accuracy of noninvasive haemoglobin measurement by pulse oximetry depends on the type of infusion fluid . CONTEXT Measurement of blood haemoglobin concentration by pulse oximetry could be of value in determining when erythrocytes should be transfused during surgery , but the effect of infusion fluids on the results is unclear . OBJECTIVE To study the effect of crystalloid and colloid fluid on the accuracy ( bias ) and precision of pulse oximetry haemoglobin estimation to indicate the venous haemoglobin concentration in volunteers . DESIGN Open interventional crossover study . SETTING Single university hospital . PARTICIPANTS Ten male volunteers aged 18-28 ( mean 22 ) years . INTERVENTIONS Each volunteer underwent three infusion experiments on separate days and in random order . The infusions were Ringer 's acetate ( 20 ml kg ) , hydroxyethyl starch 130/0.4 ( 10 ml kg ) and a combination of both . RESULTS At the end of the infusions of Ringer 's acetate , pulse oximetry haemoglobin concentration had decreased more than the true haemoglobin concentration ( 15 vs. 8 % ; P < 0.005 ; n = 10 ) whereas starch solution decreased pulse oximetry haemoglobin concentration less than true haemoglobin concentration ( 7 vs. 11 % ; P < 0.02 ; n = 20 ) . The same differences were seen when the fluids were infused separately and when they were combined . The overall difference between all 956 pairs of pulse oximetry haemoglobin concentration and true haemoglobin concentrations ( the bias ) averaged only -0.7 g l whereas the 95 % prediction interval was wide , ranging from -24.9 to 23.7 g l. In addition to the choice of infusion fluid , the bias was strongly dependent on the volunteer ( each factor , P < 0.001 ) . CONCLUSION The bias of measuring haemoglobin concentration by pulse oximetry is dependent on whether a crystalloid or a colloid fluid is infused . TRIAL REGISTRATION ClinicalTrials identifier : NCT01195025 .
57865
Intervention_Physical
pulse oximetry
57866
Intervention_Physical
pulse oximetry
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Intervention_Physical
infusion experiments
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Outcome_Other
noninvasive haemoglobin measurement
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Outcome_Physical
haemoglobin
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Outcome_Physical
haemoglobin
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Outcome_Physical
oximetry haemoglobin