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NURS601 Week 1
Concept 3: Acid-base balance (too much/too little acid)
Blood pH levelsDependent on H+ concentration | Normal pH: 7.35-7.45 | Alkalosis: 7.45-7.8 | Acidosis: 7-7.35 | Anything >7.8 or <7 is deadly |
BuffersBuffering is the primary regulator of acid-base balance. | Buffers act chemically to change strong acids into weaker ones, or bind them to neutralise them | Different buffer systems assume dominant roles in different parts of the body: | Extracellular Fluid (ECF) | Major buffer: Bicarbonate buffer system | | | Minor buffers: Intracellular problems, Phosphate buffer system | Blood | Major buffers: Bicarb buffer system, Hemoglobin | | | Minor buffers: Plasma proteins, Phosphate buffer system | Intracellular fluid (ICF) | Major buffers: Proteins, Phosphate | | | Minor buffers: None | Urine | Major buffers: Ammonia, Phosphate | | | Minor buffers: None |
RenalSecretes free hydrogen ions into renal tubules | Excretes weak acid | Excretes HCO3 (if there is metabolic acidosis) |
Reading arterial blood gases (ABG)Respiratory Acidosis | Decreased pH, increased PaCO2, normal HCO3 | Respiratory Alkalosis | Increased pH, decreased PaCO2, normal HCO3 | Metabolic Acidosis | Decreased pH, normal PaCO3, decreased HCO3 | Metabolic Alkalosis | Increased pH, normal PaCO2, increased HCO3 | Normal ABG figures | pH | 7.35-7.45 | PO2 | 80-100 | PCO2 | 35-45 | HCO3 | 22-28 |
| | Acid-base homeostasisHow is it maintained? | Buffers | Bicarbonate (HCO3) - reacts rapidly, less than an second. Chemically change strong aicds to weaker acids or bind to neutralise effect | Resipratory system | Reacts rapidly - seconds to minutes | Renal system | Reacts slowly - hours |
RespirationCO2 formed and excreted in lungs | Lungs excrete CO2 + H2O as by-products of cellular metabolism | CO2 is regarded as an acid | Homeostasis cycle of CO2 in the body: | During exercise or other activity, cell metabolism increases and produces more CO2, then: | More CO2 dissolves in blood, forming carbonic acid which lowers blood pH slightly, then: | Receptors in the brain sense the drop in pH and send nerve signals to increase breathing rate, then: | Increased breathing rate quickly removes more CO2 from blood. Blood pH rises slightly, returning to normal - cycle starts again |
Continuous mixing of body fluids/gases
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