Fazeela's Idiots Guide to Arterial Blood Gases PDF

**[Fazeela's idiots guide to Arterial Blood Gas Analysis]** ***What is an arterial Blood Gas and why do we measure this?*** Well as in the words.. we are looking at the gases in the arterial blood (since gases are cannot be weighed in mls, we measure how much there is through partial pressure (Pa)...

**[Fazeela's idiots guide to Arterial Blood Gas Analysis]** ***What is an arterial Blood Gas and why do we measure this?*** Well as in the words.. we are looking at the gases in the arterial blood (since gases are cannot be weighed in mls, we measure how much there is through partial pressure (Pa). We need to know about the concentration of gases, as gases are involved in maintaining the exact PH of the blood. We need an accurate PH to keep the body in balance and keep the organs ticking along in harmony. The organs rely on an accurate PH to operate efficiently. ***Which organs are involved in keeping this PH at balance?*** Lungs: Through respiration (Remember when we ventilate the patient, we can adjust the rate and depth of breaths, increase O2, hyperventilate to remove CO2 from blood) Kidneys: Generate Bicarbonate (HCO3) and also excrete it. Bicarbonate (alkaline) mops up/buffers excess Hydrogen ions (acidic), producing CO2+ water, which we can always remove through controlled ventilation. p.s. the problem arises when the kidneys can no longer produce enough bicarbonate to buffer the acid (hydrogen) making the patient extremely acidotic. ***Let's try and remember (or right at the back of my badge on a sticker) to eventually stick it the normal parameters in my brain.*** **Normal PH Range: acidotic ≤ 7.35-7.45 ≥ alkalotic** **PaO2: 10-13Kpa (10 Kpa less than inspired air) So if you were giving 50% O2, you should get 40Kpa PaO2 (but remember you are giving O2 cos there is summat wrong with the breathing, so you might get a lower reading)** **PaCO2: alkiolotic ≤ 4.7-6.0Kpa ≥ acidic Remember this is the figure that matters more to decide whether this is respiratory acidosis (so long as the Bicarbonate shows normal range, or it could be that the bicarbonate was the preceding issue)** **HCO3 (Bicarbonate/alkaline (Like Gaviscon, which puts a cover on the acid heartburn): acidosis ≤ 22-26 mmol ≥ alkalosis. Remember if it is low, then the kidney aint producing enough and we can give bicarbonate, but it takes time cos this is to do with kidneys and absorption. But if it is too high then we cant take bicarbonate out of the system (I guess we can try to compensate by reducing ventilation rate so CO2 stays in the blood and balances things out to balance the overall PH??)** **BE (Base Excess): -2mmol-metabolic acidosis** **+2mmol- metabolic alkalosis** **This is how much acid or alkaline we need to correct the PH to 7.4** **Where should we take arterial blood from?** Preferably radial artery or peripheral. If we take it from central arteries, there is risk of infections and thrombus. **What information should you take with you with the sample?** Firstly, take the sample promptly so it doesn't metabolise and clot up. 1. You need to know the % of O2 they are receiving and ventilation details 2. You need to know patient's temperature **So in Fazeela's words to make sense of this,** 1. **Look at the PH (Is it acidic or alkalotic)** 2. **Now decide, is it respiratory or metabolic. If its change in CO2 but not HCO3 then it is respiratory/ if it is HCO3 and slight CO2 then primarily metabolic.** 3. **How much do we need to correct it? Look at BE** **Now to complicate stuff even more, we get other additions, like glucose, potassium, and calcium. They can be the ones causing all this. But I guess if we have the normal parameters, we can decide if these are the issues and correct them through drugs. But this is something we learn through experiences. Remember 1, linked to cardiac arrest and a 'H' Hyperkalaemia (too much potassium), or could be hypo/hyper calcaemia!**