When assessing a 3-month-old infant with respiratory distress, what should the nurse do first?

In the context of assessing a 3-month-old infant with respiratory distress, checking the infant's oxygen saturation is critical and should be the first action taken. This measurement provides vital information about the infant's oxygen levels and can indicate the severity of the respiratory distress. Early identification of hypoxia is crucial, as it can lead to prompt interventions that might be necessary to ensure the infant’s safety and well-being.

When assessing respiratory distress, it is essential to prioritize actions based on the immediate risk to the patient's life. Measuring oxygen saturation through pulse oximetry is a non-invasive and quick method to determine if the infant is receiving adequate oxygenation. If the oxygen saturation is low, it can guide further interventions such as supplemental oxygen or more aggressive respiratory support.

Other considerations, such as checking the heart rate or obtaining more information, are important but are not as immediately critical as determining oxygen saturation in a situation where the infant is showing signs of respiratory distress. While weighing the infant provides useful information regarding growth and development, it is not relevant to managing acute respiratory concerns. Thus, assessing oxygen saturation first is the most appropriate action in this scenario.