CASE HISTORY • Part 1
A 27-year-old man is brought to the emergency room by the rescue service after suffering significant blood loss from a chain saw laceration of the right thigh. The EMTs have applied a pressure dressing to the wound and initiated an intravenous saline drip at a rapid rate. Vital signs in the field were BP - 110/60 mm Hg, P - 120 bpm, R - 22 bpm.
On examination, the patient is pale, anxious, and breathing rapidly but is alert and able to answer questions. He denies other illness or injuries besides the thigh wound. Supine vital signs are BP - 100/55 mm Hg, P - 130 bpm, R - 24 bpm. On sitting his blood pressure falls to 60/40 mm Hg and he feels faint.
A second intravenous line is placed and blood is drawn for a complete blood count (CBC), coagulation profile, and STAT type and crossmatch for 4 U of red blood cells. Ringer lactate is infused at a maximum rate and vital signs are continuously monitored. Surgical consultation is requested. Questions
Based on the patient's appearance and vital signs, how much blood would you estimate he has lost?
In order to correct for this loss, what volume of Ringer lactate/electrolyte solution should be infused and how rapidly?
Is he a candidate for an immediate type O-negative blood transfusion?
Acute blood loss has a direct impact on the integrity of the blood volume and oxygen supply to tissues. Sudden, severe hemorrhage can induce hypovolemic shock, cardiovascular failure, and death. When blood loss is more gradual, the hemoglobin level can fall to a point where oxygen delivery to vital organs is compromised. Chronic blood loss will deplete iron stores and produce an iron-deficiency anemia. Therefore, diagnosis and management of a blood loss anemia must take into account the reason behind the loss, the rate and amount of blood loss, and the capacity of the patient to compensate for both volume losses and anemia.
NORMAL RESPONSE TO BLOOD LOSS
Compensation for acute hemorrhage involves both a well-defined cardiovascular response to hypovolemia and the erythropoietic response to a reduction in red blood cell mass.
A normal individual readily tolerates blood volume losses of up to 20% of the total blood volume (Table 10-1). This is accomplished by redistribution of blood flow, principally a contraction of the venous blood pool by reflex venospasm. Pain, fever, or a vasovagal response can interfere with this normal compensatory mechanism. An obvious example of this is the vasovagal syncope reaction to a painful injury or the anxiety initiated by acute blood loss.
TABLE 10-1Symptoms and signs of blood volume losses in the adult