Heart rate, oxygen saturation, and skin conductance: a comparison study of acute pain in Brazilian newborns.

Heart rate variability (HRV), oxygen saturation variability (OSV) and skin conductance activity (SCA) are recognized physiological markers of acute pain. In order to verify which of them has the best correlation with psychophysical parameters of pain (intensity, reactivity, direction, regulation and slope), an observational prospective study was performed, including 41 healthy full term newborns. The measurements studied were the HRV, the OSV, and the following SCA variables: number of waves per second (NWps) and relative area under the curve of waves (AUC). The measurements were performed in periods labeled before, during, and after a heel prick. The variation measured for intensity between periods was significant for the NWps (p=0.001), AUC (p=0.03), HRV (p=0.001) and OSV (p=0.004). Also, the reactivity and direction were significant for all variables, except AUC. The regulation parameter was significant for the variables NWps (p<0.01), AUC (p<0.05), HRV (p<0.01) and OSV (p<0.01). The slope was statistically significant only for the OSV variable (p=0.000). We concluded that the responses of the SCA, HRV and OSV to painful events fit the psychophysical parameters of a physiological marker and serve as valuable measures for pain diagnostic working the use in accordance with the needs of the context.