In a critical situation, which of the following should always be checked first for a patient in shock?

In a critical situation, the airway is the most vital aspect to assess first for a patient in shock. Maintaining a patent airway is essential because if the airway is compromised, the patient will be unable to breathe effectively. Inadequate oxygenation can lead to rapid deterioration, particularly in shock, where the body's circulation may already be compromised.

The assessment of the airway allows for immediate intervention if needed, such as positioning the patient, using manuevers to clear the airway, or preparing for advanced airway management. Other parameters like blood pressure, pulse rate, and skin temperature are indeed important indicators of shock and can provide valuable information about the severity of the condition. However, they are secondary to ensuring that the patient can breathe and receive adequate oxygenation, which is why checking the airway should always be the first priority.