essay 13 - acid-base balance disorders - basic characteristics, parameters, compensations, characteristics of the main acid-base disorders

What does acid base mean

• the Maintenance of a stable blood PH (7.35-7.45)

• this is of great importance as even small changes in PH alters enzyme activity, electrolyte disturbance and cardiac/ neurologic function

regulatory systems of acid base

1. buffer system

• bicarbonate buffer system = the most important extracellular buffer system

• protein buffer = haemoglobin and plasma proteins (albumin)

• phosphate buffer = active in kidney (renal tubules)

2. respiratory regulations

• fast, takes minutes to hours

• lungs regulat PaCO2 (partial pressure of CO2 in arterial blood) through Alveolar ventilation

• increase ventilation→ decrease PaCO2 → increase PH

• decrease ventilation → increase PaCO2 → decrease PH

3. renal regulations

• slower, takes hours to days

• kidneys excrete hydrogen ions and resorb filtered bicarbonate ions

important parameters to remember

• PH = 7.35-7.45

• PaCO2 = 35-45 mmHg → respiratory component

• [HCO3^-] = 22-26 mmol/L → metabolic component

• H⁺ = 35-45 nmol/L

what are the body's mechanisms to compensate with imbalance of acid base

1. respiratory compensation via lungs

• acidosis → hyperventilation → decreased pCO2

• alkalosis → hypoventilation → increased pCO2

2. metabolic compensation via kidneys

• acidosis→ retention of HCO3- and removal of H+

• alkalosis→ retention of H+ and removal of HCO3-

describe the etiology, process and compensation, symptoms of respiratory acidosis - increased PCO2

• etiology

— carbonic acid excess = hypercapnia

— chronic conditions = drugs or head trauma which depresses the centre in the brain which controls breathing, paralytis of chest or respiratory muscles, emphysema

— acute conditions = pulmonary edoema or pneumothorax

• process and compensation:

1. hypoventilation, causes poor CO2 removal from lungs and the pCO2 levels in blood rises

2. there is increased carbonic acid formation, increasing the H+ concentration and decreasing blood PH

3. Kidney increases H+ Excretion in urine increases HCO3- reabsorption to buffer the acid

• Symptoms-

— breathlessness and restlessness, respiratory rate rapid then gradually depressed

— skin warm and flushed due to Vasodilation caused by excess CO2

describe the etiology, process and compensation, symptoms of respiratory akalosis - decreased PCO2

• etiology=

— hyperventilation = anxiety, aspirin overdose

— carbonic acid deficit = hypocapnia

— oxygen deficiency at high altitudes

• process and compensation=

1. hyperventilation, causing too much CO2 to be blown off, the pCO2 in the blood decreases

2. there is a decreased carbonic acid formation, reducing the H+ concentration and increases blood pH making it more alkaline

3. the kidneys conserve H+ ions and eliminate HCO3- in urine

• Symptoms:

— excitability of CNS and PNS = nervousness, muscle spasms, convulsions, numbness, light-headedness

describe the etiology, process and compensation, symptoms of metabolic acidosis - decreased serum bicarbonate ion

• etiology:

— the loss of bicarbonate ions through diarrhoea or renal dysfunction

— kidney failure

— accumulation of Acids (lactic acid or ketones), diabetic ketoacidosis

• process and compensation:

1. bicarbonate ions decrease due to excess presence of ketones, chloride or oraganic acid ions

2. hyperactive breathing to blwo off CO2, and kidney conserve HCO3- and eliminate H+ in urine

• symptoms:

— headache, sleepiness, confusion

— seizures, weakness

— diarrhea, vomitting and nausea

— shortness of breath

— increased HR

types of metabolic acidosis

• diabetic ketoacidosis

• lactic acidosis

• renal failure (severe)

describe the etiology, process and compensation, symptoms of metabolic alkylosis - increased serum bicarbonate ions

• etiology

— vomiting

— excessive use of alkaline drugs e.g antacids

— severe dehydration

• process and compensation

1. bicarbonate ions increase due to loss of chloride ions or excessive ingestion of sodium bicarbonate

2. breathing suppressed to hold CO2 and kidneys conserve H+ ions and excrete HCO3- via urine

• symptoms

— slow and shallow respiration

— hyperactive reflexes

— atrial tachycardia, dysrhytmias