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- Thu Jun 17, 2010 12:36 pm
If you have a sample of some blood cells, and about two months go by, is it possible to then see levels of CO-2. basically, would you be able to tell if it goes beyond 40 or 45 mm of Hg (mercury)?
| Dr.M.Aroon kamath
- Wed Aug 04, 2010 3:04 am
It is not possible to even contemplate answering about a parameter(PCO2), that is largely dependent on the vitality of the red Blood Cells (RBCs), as many vital details are lacking in your question, such as,
- the RBCs are from which "coelomate animal" ? [animals that have a body cavity - includes mammals and non-mammals. Coelomate animals have blood],
- in what kind of a solution are they stored,
- at what temperature they are stored,
- in what type of container they are stored(glass/plastic - gases may diffuse through. More so, for plastic),
- are they exposed to the atmospheric air or kept in a hermetically sealed container,
- are they from an arterial, venous or capillary blood sample,
- was the subject suffering from respiratory illness, at the time of sample collection,
- was the subject's acid-base balance normal or otherwise?,
- are there Leukocytes along with them?,
- and so on....
From the moment blood exits the circulation(from being in vivo to in vitro), it starts to undergo many changes. The "sum of all bad things" that that happen to RBCs from this point onwards, is called as the "RBC storage lesion". This lesion comprises of all the changes brought upon in the course of blood storage, which limit the survival of the RBCs, when they are returned to the circulation once again.
The RBC storage lesion includes:
- reduction in deformability of the RBCs associated with loss of membrane constituents and haemoglobin,
- depletion of red cell ATP and 2,3-DPG (causing left shift of O2 dissociation curve) and
- accumulation of bioreactive substances primarily released from white blood cells and consumption of oxygen (in non-leucocyte-reduced blood).
CO2 is generated during aerobic metabolism, while lactic acid is produced all through aerobic activity in blood in vitro. The availability of O2 is altered depending on number of leukocytes. Moreover, glycolysis is a predominant way of ATp generation in the mature erythrocytes. The temperature is shown to be key-factor in the regulation of these metabolic changes in blood.
Blood gas analysis should be performed preferably, immediately after collection of an arterial blood sample. However, in practice, small delays do occur due to several factors.Some studies have tried to address the effects of such delays.Effects on the samples by delays of 15 minutes upto 3 hours have been studied. Majority of them seem to indicate that determination of blood gases should be done within in 15-30 min at the room temperature or within 2-3 h if stored at 4°C after withdrawing. Glass containers or syringes are said to be preferable over plastic (newer low diffusibility plastic syringes have become available).Changes in blood gas levels did continue to worsen with time but, the changes between 1and 3 hours was not thought to be significant enough to affect clinical decisions.
In many countries, in blood component preparation, upon donation, the temperature of whole blood units is brought down to room temperature rapidly using special plates and are kept overnight at room temperature (20 ± 2 °C) and further processing done following morning.
With the availability and use of modern anticoagulant/preservative solutions, it is possible to bank whole blood for a period of up to 42 days.
Frozen-stored red blood cells (FS-RBC) are usually preserved upto 3 years and sometimes longer.Cryopreservatives are used to prevent ice formation within the cells.Liquid nitrogen(at -196°C) is used for cooling.
At 1 atmosphere presssure(mean sea level pressure), the CO2 gas turns solid at temperatures below −78 °C (−108.4 °F). There is paucity of information as to the fate of CO2 'gas' under these conditions.
You have to only surmise from the foregoing account what the fate of those RBCs is most likely to be.
Thank you for this very interesting question.