Tutorial 1 Power of Hydrogen (Hydrogen Ions and the pH) скачать в хорошем качестве

Tutorial 1 Power of Hydrogen (Hydrogen Ions and the pH)

This is the first tutorial in a new series on acid base balance. This is not a beginners course - although I will attempt to cover everything the bedside clinician should know, particularly in the ICU. I have been teaching and writing about acid base for more than 25 years and I find it disappointing how many clinicians fail to understand even the basics of physical chemistry that underpin this topic. This course is built on the foundation of physical and electrochemistry (all acid base reactions occur in water, all ionizing processes must be accounted for electrical neutrality must always hold. The first tutorial is titled "The Power of Hydrogen" and it looks at the chemistry of water, the tendency for water to dissociate into moieties that display hydrogen ions and hydroxyl ions, and how temperature impacts that dissociation equilibrium. It is imperative that you understand that there are effectively no free protons (hydrogen ions) in the extracellular fluid. When we measure [H+] or its corollary, pH, we are measuring hydrogen ion ACTIVITY not hydrogen ion concentration. I explain the origin of pH and how pH varies with temperature despite the aqueous solution remaining chemically neutral. I explain the history of acid base, starting with O'Shaughnessy and then moving on to Arrhenius and Bronsted and Lowry. It is easier to understand acid base if one utilizes the Arrhenius theory, but the concepts are fully consistent with the BL approach, because water is amphiprotic (it can act as a "proton donor" or "proton acceptor." I explain how blood gas machines measure pH and why pH (and PCO2) should almost always be measured at 37 degrees Celsius. At the end of the tutorial I explain the terms acidosis and alkalosis, respiratory and metabolic. @ccmtutorials www.ccmtutorials.org Contents 00:08 Introduction 02:00 Why do we do a "Blood Gas" 03:34 Clinical Scenario 04:10 The Physical Chemistry of Water 05:50 Water Dissociation 06:08 Why there are NO PROTONS in the Body 07:40 What a [H+] of 40nmol/L Actually Means 08:50 Hydrogen Ion Concentration vs Hydrogen Ion ACTIVITY 09:25 What are ACIDS and What are BASES? 11:10 Arrhenius Theory of Acid Base 12:30 Bronsted Lowry Theory of Acid Base 13:35 How Arrhenius and BL are Consistent (water is amphiprotic) 15:00 The pH Scale 16:40 Understanding Neutrality 17:05 How Blood Gas Machines Measure Hydrogen Ion Activity and pH 19:45 The Impact of Temperature on pH and Why it is Important 21:37 Why You MUST Measure pH at 37 degrees Celcius 21:50 Impact of Hypothermia and Hypothermia on Blood pH 24:15 Intracellular vs Extracellular pH 24:49 Rule of Thumb [H+] versus pH 25:00 Resolution of the Clinical Scenario 25:54 Acidosis and Alkalosis - what are they? 26:40 ACIDOSIS defined 28:10 ALKALOSIS defined 29:05 Why "COMPENSATION" Changes the pH and Makes the pH on Blood Gas an UNRELIABLE screening tool 30:06 Conventional Terminology (Respiratory Acidosis and Alkalosis - acute and chronic) Metabolic Acidosis and Alkalosis 33:10 Rule of 40: at pH 7.40 the [H+] is 40nEq/L and the PaCO2 is 40mmHg 33:47 Review of Tutorial 34:43 Wrap