ABG Part-4 | Acid-Base Disorders Explained: Metabolic & Respiratory Disorders

In this ABG interpretation and acid-base disorders lecture, we take a systematic approach to understanding the four major acid-base disorders: metabolic acidosis, metabolic alkalosis, respiratory acidosis, and respiratory alkalosis. The focus is not simply on memoizing ABG patterns, but on understanding why pH, PaCO₂, and HCO₃⁻ change, how the body compensates, and how these findings help us identify the underlying clinical problem. In this lecture, you will learn: 🔹 Metabolic acidosis — why HCO₃⁻ falls, how excess acid accumulates or bicarbonate is lost, and how the lungs compensate through hyperventilation and reduced PaCO₂. 🔹 Base excess and base deficit — what a negative base excess actually means and how increasing base deficit reflects a more significant metabolic acidotic process. 🔹 High anion gap metabolic acidosis (HAGMA) — how accumulation of unmeasured anions produces an increased anion gap. 🔹 Normal anion gap metabolic acidosis (NAGMA) — why bicarbonate loss can produce hyperchloremic metabolic acidosis, including conditions such as diarrhoea and renal tubular acidosis. 🔹 Anion gap explained — how the anion gap is calculated, why unmeasured anions matter, and how changes in bicarbonate and chloride help us understand different types of metabolic acidosis. 🔹 Lactic acidosis — how inadequate tissue oxygen delivery can increase lactate production and contribute to high-anion-gap metabolic acidosis, particularly in conditions such as shock and sepsis. 🔹 Diabetic ketoacidosis (DKA) — how insulin deficiency causes fat breakdown, ketone production, falling bicarbonate, and high-anion-gap metabolic acidosis. We also discuss the important features used to recognise DKA and severe DKA. 🔹 Metabolic alkalosis — how loss of H⁺, chloride depletion, potassium depletion, vomiting, diuretics, hyperaldosteronism, and bicarbonate administration can contribute to alkalosis. 🔹 Chloride-responsive metabolic alkalosis — why vomiting and volume depletion can maintain metabolic alkalosis and how normal saline helps correct the underlying chloride and volume depletion. 🔹 Respiratory acidosis — how hypoventilation causes CO₂ retention and how the kidneys compensate by increasing HCO₃⁻. 🔹 Acute vs chronic respiratory acidosis — how renal compensation changes the ABG pattern over time and how acute-on-chronic respiratory acidosis can produce severe acidaemia. 🔹 Respiratory alkalosis — how hyperventilation lowers PaCO₂ and raises blood pH, including common causes such as pain, anxiety, fever, and hypoxaemia. 🔹 How to distinguish similar ABG patterns — for example, how to differentiate metabolic acidosis from respiratory alkalosis when both PaCO₂ and HCO₃⁻ are decreased, and how pH helps identify the primary disorder. 🔹 Mixed acid-base disorders — including the particularly dangerous combination of respiratory acidosis + metabolic acidosis, as well as situations where two primary disorders can occur together, such as salicylate poisoning. Timestamp: 00:00 - Intro 00:47 - Metabolic Acidosis 07:58 - What is Anion Gap? 13:15 - Lactic Acidosis 15:34 - Diabetic Ketoacidosis 19:38 - Metabolic Alkalosis 30:43 - Respiratory Acidosis 34:44 - Respiratory Alkalosis 37:48 - Mixed Disorders Key topics covered • Acid-base balance • ABG interpretation • ABG analysis • metabolic acidosis • metabolic alkalosis • respiratory acidosis • respiratory alkalosis • anion gap • high anion gap metabolic acidosis • normal anion gap metabolic acidosis • hyperchloremic metabolic acidosis • lactic acidosis • diabetic ketoacidosis • DKA • bicarbonate • HCO₃⁻ • PaCO₂ • base excess • base deficit • respiratory compensation • renal compensation • mixed acid-base disorders This lecture is designed to help MBBS students, medical students, nursing students, and learners preparing for USMLE, NEET-PG, FMGE and other medical examinations build a clear conceptual understanding of acid-base disorders and ABG interpretation. If you found this lecture helpful, LIKE the video, COMMENT with your questions or difficult ABG concepts, SHARE it with your classmates, and SUBSCRIBE to the channel for more concept-based medical lectures. 🔔 Turn on notifications so you don't miss the next lecture in the ABG / Acid-Base Disorders series. #AcidBaseDisorders #ABGInterpretation #MetabolicAcidosis #AnionGap #DKA #LacticAcidosis #MetabolicAlkalosis #RespiratoryAcidosis #RespiratoryAlkalosis #ABGAnalysis #MedicalEducation #MBBS #USMLE #NEETPG