I have been 'bombarded' by students over this topic over the past few days. Let me clarify a few things:
1. We use sodium citrate and NOT potassium citrate.
2. The amount used is 30mL of 0.3M
3. It prevents Mendelson's Syndrome
4. It is normally used with ranitidine
5. It does increase the volume of gastric content
6. It 'elevates' the pH of stomach contents. The keyword here is 'elevate'. Bear in mind, pH2 to pH5 also means 'elevate'! Not necessarily the stomach contents turn ALKALINE!
7. The wikipedia says sodium citrate is the sodium salt of citric acid, a weak acid (based on information available when accessed on 7/12/2007)
8. I don't know the actual pH of 0.3M sodium citrate. But, it is definitely higher than 5.6
9. The pH of gastric acid is 1 to 2
From my residual knowledge of chemistry, when you neutralize acid with alkali, you will get a SALT. Perhaps we don't want that to happen and choose to 'dilute' the stomach pH but keep it acidic.
For the uninitiated, sodium citrate is a common oral medication given to pregnant women before Caesarean Section.
I hope students do not forget the basic concept of preventing aspiration pneumonia that is:
1. Adequate fasting prior to a surgery
2. Avoidance of general anaesthesia unless really necessary
3. Rapid sequence induction anaesthesia (in case of GA)
4. Cricoid pressure
The administration of sodium citrate is just a minor component of the overall picture. You will learn more during your anaesth attachment in Sem9.