I'm afraid you're underestimating the degree of hypovolaemia present. In a normal adult, a tachycardia indicates at least a 15% loss of blood volume (>750 mls). The ATLS classification of shock is given below : Re-assess his circulatory status

Class       Pulse   Blood Pressure  CNS Status      Urine       Blood Loss
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Class I     <100    Normal          Slight anxious  >30ml/hr    <15%
Class II    >100    Normal          Mildly anxious  20-30       15-30%
Class III   >120    Decreased       Confused        5-15        30-40%
Class IV    >140    Decreased       Lethargic       nil         >40%
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