What is the first action for a nurse assessing a client with drooling and hoarseness after a burn?

When a nurse encounters a client presenting with drooling and hoarseness following a burn, the primary concern is the potential for airway compromise. These symptoms may indicate swelling of the airway or possible inhalation injury, which can rapidly lead to obstruction. Administering 100% humidified oxygen is crucial in this scenario because it helps to ensure that the client's airway remains patent and that they are receiving adequate oxygenation. The humidified oxygen serves to soothe the irritated tissues and to prevent further airway swelling.

The other options, while important in managing a client's overall care, do not address the immediate risk to the airway. Monitoring vital signs is essential for ongoing assessment, intravenous fluids may be necessary for volume resuscitation, and applying a burn dressing is a critical step in managing the burn itself. However, none of these actions provide the immediate intervention needed to secure the airway and support effective oxygenation in a situation where there could be significant respiratory distress. Therefore, the most appropriate initial action is administering humidified oxygen to address the urgent potential for airway compromise.