It was believed, for many years, that a haemoglobin level of minimum 10 Gm per 100 ml MUST be reached before a patient is taken up for surgery. In 1988 The journal of American Medical Association carried a report of a "Consensus Conference" held in The U.S.A. to answer this question. It was agreed that under certain circumstances it was permissible to undertake surgery with the patient's haemoglobin level as low as 7 Gm per 100 ml. However, the consensus was that although low haemoglobin levels do not constitute any hazard of delayed healing, each case should be determined on its own merit.

Now, the question that arises is "What are the parameters for this determination?"
An answer to this question will emerge after we quickly revise the physio- pathology of The most important function of blood namely oxygen carrying, and how it is affected by anemia.

The red blood cells have an enzyme called 2,3-diphospho glycerate (or 2,3-DPG). The level of this enzyme in the red cells determines the affinity of haemoglobin towards oxygen. When the level of 2,3-DPG increases, the haemoglobin affinity for oxygen decreases. This decrease means that haemoglobin will give up oxygen even if the partial pressure difference is low. In other words, with the increase of red cell 2,3-DPG the oxygen dissociation curve will undergo a shift to the right. In more simple words, it means that when 2,3-DPG levels are at its peak, blood with 8 Gm per 100 ml haemoglobin will release as much oxygen to the tissues as 14 Gm haemoglobin would, at normal 2,3-DPG levels.

This is the reason why 2,3-DPG level starts increasing as anaemia advances. This compensatory phenomenon works only upto the level of 8 Gm haemoglobin. When haemoglobin levels go below this, the body has to bring in other mechanism to fulfill the oxygen requirement of the tissues. This mechanism is an increase in the cardiac output. Clinically we see this as tachycardia in the anaemic patient.

In my opinion an anaemic patient with tachycardia is the only one who need to boost up the haemoglobin level prior to surgery.

There are two important things to remember: ONE, the heart of the anaemic patient with tachycardia is already under stress. Such patient should receive RBC Concentrates (or Packed Cells) only, to avoid volume overload; and TWO, it is necessary to investigate and treat the cause of anaemia.