Brazilian Journal of Anesthesiology
https://bjan-sba.org/article/doi/10.1590/S0034-70942001000400005
Brazilian Journal of Anesthesiology
Scientific Article

Gradiente SpO2 - SaO2 durante ventilação mecânica em anestesia e terapia intensiva

SpO2 - SaO2 gap during mechanical ventilation in anesthesia and intensive care

Pablo Escovedo Helayel; Getúlio R de Oliveira Filho; Lúcia Marcon; Flávio Hülse Pederneiras; Marcos Antônio Nicolodi; Sérgio Galluf Pederneiras

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Resumo

JUSTIFICATIVAS E OBJETIVOS: A saturação periférica da oxihemoglobina (SpO2) é freqüentemente utilizada para guiar alterações do regime ventilatório. Valores de SpO2 iguais ou superiores a 96% são necessários para garantir saturação arterial da oxihemoglobina (SaO2) superiores a 90%, em pacientes de terapia intensiva. Este estudo teve por objetivo determinar concordância entre valores de SpO2 e SaO2 e delimitar a menor SpO2 associada a valores de SaO2 iguais ou superiores a 90%. MÉTODO: Foram incluídos prospectivamente 120 pacientes adultos, de ambos os sexos, submetidos à anestesia geral com ventilação mecânica ou em tratamento intensivo. Amostras de sangue arterial foram coletadas por punção arterial ou por aspiração de linha arterial, utilizando técnica anaeróbia, em seringas heparinizadas. As amostras foram analisadas imediatamente após a coleta. A SpO2 foi medida por oxímetro de pulso durante a coleta, no indicador da mão contra-lateral, utilizando a onda dicrótica de pulso arterial como parâmetro de adequação. RESULTADOS: Foram analisadas 228 amostras. A diferença entre os valores de SpO2 e SaO2 variou entre -7,10% e 15,20%, sendo a diferença média igual a -0,20% ± 2,02%. SpO2-SaO2 maiores que 4,04% (dois desvios padrão da diferença) ocorreram em 4,72% das amostras. A determinação gráfica da SpO2, mínima para garantir a SaO2 acima de 90%, mostrou que somente valores de SpO2 iguais ou superiores a 99% não se associaram à ocorrência de nenhum valor de SaO2 inferior a 90%. CONCLUSÕES: Embora a diferença entre os valores de SpO2 e SaO2 tenham se localizado entre mais e menos 5% em 97% dos pares analisados, somente valores acima de 99% excluíram pacientes com SaO2 menor que 90%.

Palavras-chave

MONITORIZAÇÃO, VENTILAÇÃO

Abstract

BACKGROUND AND OBJECTIVES: Peripheral oxy-hemoglobin saturation (SpO2) is commonly used to guide ventilator settings. SpO2 values equal to, or higher than 96% are necessary to assure arterial oxy-hemoglobin saturation (SaO2) higher than 90% in intensive care patients. This study aimed to determine SpO2 - SaO2 gap and to establish the lowest SpO2 associated to SaO2 values equal to, or higher than 90%. METHODS: Participated in this prospective study 120 adult patients of both genders submitted to general anesthesia and mechanical ventilation or under intensive care. Arterial blood samples were obtained by arterial puncture or central line aspiration using the anaerobic technique and heparin-containing syringes. Samples were analyzed immediately after collection. SpO2 was measured during collection with the pulse oximeter placed on the opposite second finger and using arterial pulse dichroic wave as the adequacy parameter. RESULTS: Two hundred and twenty-eight samples were analyzed. The difference between SpO2 and SaO2 ranged between -7.10% and 15.2%, being -0.20% ± 2.02% the mean difference (bias). SpO2-SaO2 higher than 4.04% (two standard deviations of the difference) was observed in 4.72% of samples. Graphical analysis of the lowest SpO2 to assure an SaO2 higher than 90% has shown that only SpO2 values equal to, or higher than 99% were not associated to SaO2 values below 90%. CONCLUSIONS: Although SpO2-SaO2 gap remaining between plus or minus 5% for 97% of the samples, only SpO2 values higher than 99% excluded patients with SaO2 values below 90%.

Keywords

MONITORING, VENTILATION

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