A marathon runner comes into the clinic and states "I have not urinated very much in the last few days." The nurse notes a heart rate of 110 beats/min and a blood pressure of 86/58 mm Hg. Which action by the nurse is most appropriate?

Rationale: A. While the client is likely dehydrated, giving a bottle of water orally may be too slow or insufficient to restore circulating volume, especially if the client is hypotensive and tachycardic. B. An electrocardiogram (ECG) may be useful later to assess for cardiac effects of dehydration or electrolyte imbalance, but it does not address the immediate hypovolemia. C. Teaching about daily fluid intake is preventive education and not appropriate for the acute, potentially life-threatening situation. D. The client shows signs of hypovolemic shock: tachycardia, hypotension, and oliguria. The priority is to rapidly restore intravascular volume with an intravenous (IV) fluid bolus to improve perfusion and prevent kidney injury or other organ damage.