We recommend drawing blood up to four hours before surgery. However, there is nothing in the design or process of the Vivostat System that prevents you from drawing blood earlier. You can fill the Preparation Unit up to 24 hours before you place it in the Processor Unit. If the blood is drawn more than three hours before use in the Processor Unit, the Preparation Unit should be kept in the refrigerator at 5 degrees C (do not freeze). In addition, labelling and storage procedures will have to be established.