Abstract
Introduction: During the postoperative follow up of patients who underwent primary total hip replacement, it was observed that the haemoglobin concentration had dropped more than expected when compared to the intra and postoperative (drain) loss. This study was carried out to ascertain whether this drop in haemoglobin reflects a real blood loss or is due to hemodilution secondary to intravenous fluids, or both. Also to establish the average amount of blood loss responsible for the drop of one gm of haemoglobin concentration, in order to confirm or alter the old belief that every 500ml of blood loss is responsible for 1 gm drop in Hb concentration.
Method: A prospective study was carried out to include 20 patients undergoing primary total hip replacement due to osteoarthritis in the period, March to November 2006. 2 drains were used, one was deep and the other was superficial. 7 samples of haemoglobin were taken in every case. The first sample preoperatively, the second postoperatively in the recovery room, the third and forth samples taken 6 hours postoperatively from the patient and the deep drain. The fifth and sixth samples from the patient and the deep drain 24 hours postoperatively. And the last sample from the patient 5 days postoperatively. Also the IV Fluids given were recorded in the first 24 hours.
Results:
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The Hb concentration in the deep drain was gradually decreasing over the first 24 hours after the operation when compared to the patient’s Hb which means that the total volume of the drain loss doesn’t mean an equal volume of blood loss.
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The second drain which was inserted superficial to the iliotibial tract showed blood loss with an average of 11.2% of the total blood loss and this amount is usually missed in calculating the blood loss when using one deep drain only.
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The average blood loss responsible for the drop of one gram Hb was variable. It was 258 ml when comparing intraoperative blood loss with the immediate postoperative patient’s Hb. This increased to 341 ml when comparing the drain blood with the patient’s Hb 24 hours after the operation due to the above mentioned changes in RBCs concentration in the drain over the first 24 hours postoperatively.
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IVF has no effect in giving false readings of the Hb
Correspondence should be addressed to Mr Richard Wallace at Musgrave Park Hospital, 20 Stockman’s Lane, Belfast BT9 7JB, Northern Ireland.
