A. Bradycardia is not typically an early sign of circulatory overload; tachycardia is more common. B. Flushing is nonspecific and not a reliable early indicator of fluid overload. C. Vomiting may occur for various reasons postoperatively but is not an early sign of circulatory overload. D. Dyspnea (shortness of breath) is an early and key sign of circulatory overload, reflecting pulmonary congestion.