Management: Throughout the resuscitation period regular reassessment of the patient's condition is required and the treatment should be monitored frequently, preferably by a pulse oximeter or a continuous reading electrocardiograph. Two large (14 gauge) cannulae should be inserted. The antecubital fossae is often the easiest site, but a venous cutdown may be required.

Alternatively, the external jugular vein or the femoral vein can often be cannulated. In patients with suspected thoracic or abdominal trauma, intravenous access both above and below the diaphragm is often recommended. Central venous access is rarely indicated for initial fluid replacement, but may be useful to guide fluid therapy by measuring the right atrial pressure. Blood should be taken at the time of cannulation for crossmatch and in major trauma with shock eight units should be ordered as a priority. In Class III hypovolaemia blood is often needed before a full cross match is possible and in these circumstances blood banks should be able to provide uncrossmatched ABO compatible blood quickly. In patients not responding to volume replacement and those with Class IV hypovolaemia, uncrossmatched O Rhesus negative blood must be used and it is recommended that all Accident & Emergency Departments should have at least 2 units available at all times for immediate use.

Table 2:

Type of blood	Time required for preparation
Full crossmatch	30-40 minutes
ABO Compatible	10 minutes
Uncrossmatched O Rhesus Negative	Available Immediately

In a previously fit patient it may be necessary to accept a haemoglobin concentration of 8g/dl (as long as they are not hypovolaemic) due to the shortage of blood in many developing countries and the risks associated with transfusion (including transfusion reactions and HIV and other infections). Oxygen carrying capacity should be adequate at this level. Prompt surgery to prevent blood loss, autotransfusion and transfusion from compatible relatives must be considered. If facilities are available blood should also be taken for full blood count, electrolyte and glucose estimation, and an arterial sample should be taken for analysis of blood gas tensions and acid/base balance.

The type of intravenous fluid administered to a hypovolaemic patient prior to blood transfusion continues to be controversial, and will often depend on local policy and availability. Either crystalloid or colloid can be used as long as the following points are kept in mind:

1. Crystalloid solutions that expand primarily the extracellular fluid should be selected i.e. normal saline or Ringer's lactate. Glucose (dextrose) only fluids should not be used unless there is no alternative.

2. As crystalloids rapidly leave the circulation, 3 times as much crystalloid compared with the volume of blood loss will be required.

3. Colloids remain within the blood vessels for longer and should be administered in volumes equal to the blood loss. However, they are excreted by the body and further infusions should be administered as required.

4. Blood is the best colloid in severe haemorrhagic shock. It should always be warmed if large volumes are administered rapidly.

A sustained improvement in the signs of shock will hopefully be seen, and this suggests blood loss is less than 25% of the blood volume. If the improvement is short lived, this indicates continuing haemorrhage that requires control. Surgical intervention may be required and further blood transfusion necessary. If no improvement in the condition of the patient is seen, then the blood loss is greater than 40% and almost certainly from thoraco-abdominal or pelvic injury. It is in these patients that O negative blood should be considered.

Case History: A 36 year old fisherman was attacked by a hippopotamus whilst fishing on the isolated Lake Iteshi -teshi in Zambia. The hippo held him by the abdomen and in throwing him from the water lacerated the anterior abdominal wall exposing abdominal contents. The wound was 2 feet long and associated with some bleeding. The fisherman's friend placed a suture in the wound using a fishing hook and line and applied pressure to the wound to stop further blood loss.

He was taken to University Teaching Hospital, Lusaka in the back of a pickup truck. The journey took 15 hours. On arrival the fisherman showed all the signs of Class IV hypovolaemia. He was promptly resuscitated with oxygen and 4 litres of warmed saline over ten minutes. Blood was taken for ABO compatible cross match and a urinary catheter inserted. There was no residual urine.Within 30 minutes of arrival in hospital he had already received 3 units of warm ABO compatible blood. His condition was much improved; he had regained consciousness and was able to talk about his ordeal, his pulse rate had fallen to 90 bpm, he had a blood pressure of 120/90 mmHg and he had passed 50ml of urine. Following this prompt resuscitation, anaesthesia and surgery were uneventful, renal failure was avoided and the patient made a complete recovery. He is still fishing on Lake Iteshi-teshi.

Occasionally haemorrhage is not the cause of the hypotension. For example, septicaemia and spinal cord injury can cause hypotension, but in both there is a relative hypovolaemia and the treatment outlined above is unlikely to be harmful.

Hypotension may also result from cardiac failure which is, however, rare in trauma patients and is likely to be due to cardiac injury, either myocardial contusion (which should be suspected in blunt thoracic trauma), or cardiac tamponade (which should be suspected in penetrating chest injury when shocked patients do not respond to intravenous fluid and the hypotension is out of proportion to the apparent blood loss). Cardiac tamponade must be relieved immediately and is confirmed by Beck's triad; raised jugular venous pressure, muffled heart sounds and hypotension. Tachycardia and pulsus paradoxicus (a 15% drop in systolic blood pressure during inspiration) will be present. Cardiac tamponade is treated by needle pericardiocentesis. If caused by a penetrating implement, this must be left in place while awaiting surgery. All cases of traumatic cardiac tamponade require urgent surgical exploration.

Key points:

1. All trauma victims who are shocked have bled and are hypovolaemic until proven otherwise.

2. Commence rapid intravenous infusion immediately.

3. Warm intravenous infusions whenever possible.

4. Give warmed blood early in severe shock.

(Continued...)

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