Acid Base Disorders Flashcards
Disorders of acid-base balance are common in clinical practice. They can occur as primary disorders but are often secondary to disturbances in organ functions
To understand these disorders, it’s essential to recall the Henderson-Hasselbalch Equation:
pH = pKa + HCO3/ S.PCO 2
What’s the indicative for metabolic disorders and how does rye body try to compensate in short nd long term? .
Metabolic Disorders
HCO3 Component: Changes in bicarbonate (HCO3 ) levels are indicative of metabolic disorders.
Respiratory Compensatory Changes: In the short term, the body tries to compensate for metabolic disorders through respiratory mechanisms, but this compensation is incomplete.
Long-Term Compensation: In the long term, the kidneys adjust the bicarbonate levels, leading to a complete compensation
What’s the indicative for respiratory disorders and how does the body try to compensate in short nd long term? .
PCO2 Component: Respiratory disorders primarily affect the partial pressure of carbon dioxide (PCO2\text{PCO}_2PCO2).
Renal Mechanisms: The body compensates for respiratory disorders through renal mechanisms.
Interim Compensation: This compensation is partial and incomplete in the short term.
Long-Term Compensation: Over time, the kidneys make adjustments that usually result in complete compensation.
Acidosis: A condition characterized by an excess of acid or a loss of base in the body.
Metabolic Acidosis: Caused by a decrease in bicarbonate.
Respiratory Acidosis: Caused by an increase in PCO2\text{PCO}_2PCO2.
Alkalosis: A condition characterized by an excess of base or a loss of acid in the body.
Metabolic Alkalosis: Caused by an increase in bicarbonate.
Respiratory Alkalosis: Caused by a decrease in PCO2\text{PCO}_2PCO2
What’s the most common acid-base disorder
Metabolic Acidosis
What’s metabolic acidosis?
Metabolic acidosis is a disorder of acid-base homeostasis resulting from any process that lowers the plasma bicarbonate concentration. It is the most common acid-base disorder and involves an increase in hydrogen ions (H+) and carbon dioxide (PCO2), which are primary products of metabolism
What’s Anion Gap
:
Definition: The anion gap is the difference between the measured cations and the measured anions in the plasma.
What’s the formula for anaion gap?
Na+K=Cl+HCO3+A
Here, A\text{A}A represents the anion gap.
What’s normal anion gap?
Normal Anion Gap: 15-20 mmol/L
Anaion gap can be raised in conditions such as? Due to?
The anion gap can be raised in certain causes of metabolic acidosis due to the addition of acids such as lactic acid, urate, sulfate (SO4), and phosphate (PO4
What are the Types of Metabolic Acidosis & therlie common causes?
High Anion Gap Metabolic Acidosis (HAGMA):
This type of metabolic acidosis occurs when there is an addition of acids that are not normally present in the blood, leading to an increase in the anion gap.
Common causes include lactic acidosis, ketoacidosis, and ingestion of toxins (e.g., methanol, ethylene glycol).
Normal Anion Gap Metabolic Acidosis (NAGMA):
this type occurs when there is a loss of bicarbonate or an inability to excrete hydrogen ions, without a significant increase in unmeasured anions.
Common causes include gastrointestinal bicarbonate loss (e.g., diarrhea), renal tubular acidosis, and certain drugs.
What’s another name dir NAGMA?
Also known as hyperchloremic acidosis,
What are they causes of HAGMA?
Causes:
Acute Kidney Injury (AKI) and Chronic Kidney Disease (CKD): Impaired kidney function leads to the accumulation of acids.
Diabetic Ketoacidosis (DKA): Results from the breakdown of fats producing ketones, which are acidic.
Ethanol Intoxication: Metabolism of ethanol produces acids such as lactic acid.
Lactic Acidosis: Increased production or decreased clearance of lactic acid.
Salicylate Overdose: Aspirin overdose can lead to an accumulation of salicylates and other acids.
Toxins: Ingestion of substances like methanol, propylene glycol, paraldehyde, and paracetamol (PCM) can produce toxic metabolites.
Muscle Rhabdomyolysis: Breakdown of muscle tissue releases myoglobin and other acids.
Organic Acidurias: Genetic disorders that result in the accumulation of organic acids
What’s the important causes of METABOLIC ACIDOSIS
Important Causes of Metabolic Acidosis
Lactic Acidosis: Can result from conditions that cause increased lactic acid production or decreased clearance (e.g., sepsis, shock, intense exercise).
Renal Tubular Acidosis: A group of disorders where the kidneys fail to properly acidify the urine, leading to acid retention.
What are the Normal Anion Gap Metabolic Acidosis (NAGMA)
Causes:
Ingestion of NH4Cl, Lysine, Sulfuric Acid, or Hydrochloric Acid (HCl): Direct addition of acids to the body.
Renal Tubular Acidosis (RTA): Defects in renal tubules affecting acid excretion.
Diarrhoeal Disease, GI Fistula: Loss of bicarbonate-rich fluids from the gastrointestinal tract.
Ureteric Diversion: Surgical procedures that affect normal urinary drainage.
Excessive Saline Infusion: Large amounts of saline can dilute bicarbonate concentration.
Lactic acidosis causes what type of acidosis?
Metabolic acidosis
Causes if lactic acidosis
Causes:
Hypoxia-Related Causes:
CO Poisoning: Carbon monoxide impairs oxygen delivery.
Severe Anaemia: Reduced oxygen-carrying capacity of blood.
Sepsis: Severe infection leading to tissue hypoxia.
Non-Hypoxia-Related Causes:
Organ Disease:
Liver Cirrhosis: Impaired liver function affects lactate clearance.
Fulminant Hepatic Failure: Acute liver failure leads to lactate accumulation.
Metastatic Disease: Cancer metastases can affect liver and other organ functions.
Inborn Errors of Metabolism:
G-6-PD Deficiency: Leads to hemolysis and lactic acidosis.
Pyr Kinase Deficiency: Affects red blood cell metabolism.
Thiamine Deficiency: Vitamin B1 deficiency affects energy metabolism.
Drugs:
Biguanides (e.g., Metformin): Can cause lactic acidosis, especially in renal failure.
Salicylates: Aspirin overdose.
Methanol: Toxic alcohol.
Ethylene Glycol: Another toxic alcohol.
What’s Renal Tubular Acidosis (RTA)
RTA is a disorder that impairs the kidneys’ ability to acidify urine, leading to metabolic acidosis. It can present as either high anion gap metabolic acidosis (HAGMA) or normal anion gap metabolic acidosis (NAGMA).
What’s Type 1 RTA
Inability of the distal convoluted tubule (DCT) and collecting duct to secrete hydrogen ions (H+), leading to a failure to acidify urine below plasma pH in acidosis.
Causes of type 1 RTA?
Primary/Sporadic: Idiopathic causes.
Wilson’s Disease: Copper accumulation.
Amyloidosis: Protein deposits in kidneys.
Chronic Pyelonephritis (CPN), Post-Transplant: Kidney damage.
Autoimmune Disorders: Sjogren’s syndrome, Churg-Strauss syndrome.
Drugs: Amphotericin, Lithium.
What’s Type 2 RTA?
Type 2 RTA (Proximal RTA):
Pathophysiology: Inability to reabsorb bicarbonate (HCO3-) in the proximal tubule, leading to bicarbonate wasting.
Causes of type 2 RTA?
Primary/Familial: Genetic causes.
Secondary: Conditions like multiple myeloma, amyloidosis, heavy metal poisoning.
How can you test for type 2 RTA?
Normal urinary acidification after ammonium chloride (NH4Cl) loading test
What’s type 4 RTA?
Type 4 RTA:
Pathophysiology: Due to hyporeninemic hypoaldosteronism, causing hyperkalemic metabolic acidosis
What’s the clinical presentation of type 4 RTA?
Pediatric Patients: Recurrent vomiting, diarrhea, failure to thrive.
Adults: Recurrent metabolic acidosis with features of the underlying cause.
How do you investigate for RTA?
Type 2
NH4Cl Loading Test: To evaluate urinary acidification.
- Fractional Excretion of Bicarbonate (FEHCO3):
5%: Suggestive of type 2 RTA.
< 5%: Not typical for type 2 RTA.
Both
Urinary Anion Gap: Helps differentiate types of RTA
- Urinalysis:
Type 1 RTA: High urine pH (above 5.5).
Type 2 RTA: Variable urine pH, often initially low.
Type 4 RTA: Typically low to normal urine pH (below 5.5)
How do you treat RTA?
Treatment:
Address Underlying Cause: Treat the primary disease causing RTA.
Fluid and Electrolyte Therapy: Correct electrolyte imbalances and ensure adequate hydration.
It can present as either high anion gap metabolic acidosis (HAGMA) or normal anion gap metabolic acidosis (NAGMA).
How?
NAGMA in RTA:
Typically seen in Type 1 (distal) and Type 2 (proximal) RTA.
Primary disturbance is loss of bicarbonate or inability to excrete H+ without significant accumulation of unmeasured anions.
HAGMA in RTA:
Can occur in advanced stages of CKD or Type 4 RTA with additional factors leading to accumulation of unmeasured anions.
Accumulation of organic acids, phosphate, and sulfate in CKD can contribute to HAGMA.
Which of the following tests is essential for diagnosing lactic acidosis?
a) Serum lactate
b) Plasma glucose
c) Urea and creatinine
d) Toxicology studies
Answer: a) Serum lactate
Which of the following is a treatment option specifically for Type 4 RTA?
a) Sodium bicarbonate infusion
b) Fludrocortisone
c) Dialysis
d) Ammonium chloride
Answer: b) Fludrocortisone
Saline-responsive metabolic alkalosis can result from:
a) Diuretic use
b) Severe hypokalemia
c) Milk alkali syndrome
d) Primary hyperaldosteronism
Answer: c) Milk alkali syndrome
Which of the following is NOT a typical feature of metabolic alkalosis?
a) Elevated plasma HCO3-
b) Compensatory hypoventilation
c) Increased plasma chloride
d) Increased renal bicarbonate reabsorption
Answer: c) Increased plasma chloride
The anion gap is calculated using which of the following formulas?
a) Na + K - (Cl + HCO3)
b) Na - (Cl + HCO3)
c) K - (Cl + HCO3)
d) Na + Cl - (K + HCO3)
Answer: a) Na + K - (Cl + HCO3)
In Metabolic Acidosis normal findings of these?
HCO3
Plasma Cl in HAGMA & NAGMA
Plasma Glucose: in HAGMA & NAGMA
Serum Lactate
NH4Cl Loading Test:
Used to evaluate renal tubular acidosis (RTA).
HCO3 (Bicarbonate): Always low; hallmark of metabolic acidosis diagnosis.
Normal (N) in High Anion Gap Metabolic Acidosis (HAGMA).
Increased (↑) in Normal Anion Gap Metabolic Acidosis (NAGMA).
Elevated in Diabetic Ketoacidosis (DKA), which is a common cause of metabolic acidosis. HAGMA
Serum Lactate:
Elevated levels indicate lactic acidosis. HAGMA
Treatment for
Type 2 RTA
Type 4 RTA
Sodium Bicarbonate Infusion:
Used in severe cases to correct acidosis.
Oral Bicarbonate Infusion:
Specifically for type 2 RTA to replace bicarbonate
Fludrocortisone:
Used in type 4 RTA to manage hyperkalemia and acidosis
Treat Underlying Cause:
Identify and address the primary cause of metabolic acidosis.
Dialysis:
For drug overdoses, particularly when the substance is dialyzable.
What’s Metabolic Alkalosis
Definition:
A metabolic disorder resulting from processes that increase plasma bicarbonate (HCO3) concentration. It can be primary or compensatory
What’s rye classification of metabolic alkalosis
Classification:
Saline Responsive Metabolic Alkalosis:
Conditions that respond to saline (sodium chloride) administration.
Saline Unresponsive Metabolic Alkalosis:
Conditions that do not respond to saline administration.
What are the causes of the different kind of metabolic alkalosis?
Saline Responsive:
Milk Alkali Syndrome: Excessive intake of calcium and absorbable alkali.
Severe Vomiting: Loss of gastric acid leads to increased bicarbonate.
Chloride Loss from Skin: Seen in conditions like cystic fibrosis
Saline Unresponsive:
Diuretics: Cause loss of chloride and potassium.
Severe Hypokalaemia: Low potassium levels contribute to alkalosis.
Endogenous Mineralocorticoid Excess:
Cushing Syndrome: Excess cortisol.
Primary Hyperaldosteronism: Excess aldosterone leads to increased bicarbonate reabsorption.
Changes in Plasma Protein Binding:
Reduced Free Ionized Calcium: This leads to symptoms of hypocalcaemia even when the total plasma calcium is normal.
What are the Symptoms of Hypocalcaemia:
Facial Twitching: Involuntary muscle contractions in the face.
Headache: Pain in the head, potentially due to altered blood flow or electrolyte imbalances.
Reduced Respiration: Lower respiratory rate, which can be a compensatory mechanism for alkalosis.
Carpopedal Spasm: Involuntary contraction of the muscles in the hands and feet.
Investigations for Metabolic Alkalosis:
Usually Obvious: The cause is often clear from the patient’s history and clinical presentation.
Plasma Electrolytes:
Haemoconcentration: Increased concentration of cells and solids in the blood due to reduced plasma volume.
Urinary Chloride:
> 20 mmol/L: Indicates saline unresponsive metabolic alkalosis.
< 20 mmol/L: Indicates saline responsive metabolic alkalosis.
Metabolic Alkalosis: Basis of Treatment
Treat Underlying Cause:
Address the primary condition causing the alkalosis.
Review Suspected Drug Cause:
Evaluate and discontinue any medications contributing to the condition.
NH4Cl / Arginine Chloride Infusion:
Used to correct the alkalosis by increasing acid levels in the body.
Anti-Emetics:
Medications to control vomiting, which can prevent further loss of gastric acids.
H2 Receptor Blockers:
Medications that reduce gastric HCl loss by inhibiting the action of histamine on stomach cells, thus decreasing acid production.
What’s Respiratory Acidosis
Results from any abnormality that increases PCO2 (partial pressure of carbon dioxide).
Cause of respiratory acidosis?
Artificial Ventilation:
Hypoventilation due to mechanical issues.
Guillain-Barré syndrome (GBS), snake bites, spinal cord injury, paralytic polio.
Myasthenia gravis, kyphoscoliosis, Pickwickian syndrome.
- Airway Obstruction:
Conditions: Asthma, COPD (chronic obstructive pulmonary disease), foreign body obstruction.
- Inhibition of Respiratory Centre:
Conditions: CVA (cerebrovascular accident), head injury, opiates, benzodiazepines.
Abnormal Ventilation:
Conditions: Pulmonary edema, interstitial lung disease.
Pathophysiology: Respiratory Acidosis
Reduced Respiratory Effort:
Leads to accumulation of CO2.
Acute Increase in PCO2:
Results in hypercapnia (excess CO2 in the bloodstream).
Hypercapnia: Decreases pH in CSF and blood.
Effects: Causes cerebral vasodilatation leading to headache, stupor, and coma. Acidaemia (low blood pH) reduces myocardial contractility.
Respiratory Acidosis: Investigations
Blood Gases:
Increased PCO2 is the hallmark of diagnosis.
pH:
- Decreased or normal, depending on the level of compensation.
Electrolytes:
Generally not very helpful.
Bicarbonate (HCO3):
- Usually mildly raised, about 1-2 mmol/L for each 10 mmHg increase in PCO2.
In chronic cases, the increase can be by 3-4 mmol/L.
Respiratory Acidosis: Treatment
Treat Underlying Cause:
Address the primary condition causing respiratory acidosis.
Improve Ventilation:
Enhance respiratory effort and gas exchange.
Treat Drug Intoxication:
Use specific antidotes like Naloxone for opioid overdose.
Respiratory Stimulant:
Medroxyprogesterone can be used to stimulate breathing
Respiratory Alkalosis
A group of disorders resulting from the stimulation of the respiratory center leading to increased respiration and subsequent decrease in PCO2 (hypocapnia).
Causes of Respiratory Alkalosis
Stimulation of Respiratory Center:
Psychogenic: Anxiety, hysteria, pregnancy, encephalopathy.
Sepsis
Salicylate overdose
Hypoxemia: Congestive cardiac failure (CCF), high altitude.
Pulmonary Disease: Pneumonia, pulmonary embolism.
Mechanical Ventilation: Hyperventilation.
Pathophysiology: Respiratory Alkalosis
Results in Hypocapnia:
Reduced PCO2: Causes cerebral vasoconstriction, which can lead to nausea and vomiting.
Changes in Hydrogen Ion Concentration: Causes increased binding of calcium to albumin.
Symptoms: Carpo-pedal spasm, facial twitching, may result in cardiac arrhythmias.
Glucose Metabolism: Increases glycolysis, leading to elevated lactate and an increased anion gap
Investigations that suggests respiratory Alkalosis
Investigations
Electrolytes:
Decreased bicarbonate (HCO3).
Arterial Blood Gases (ABG):
Decreased PCO2, which is the diagnostic hallmark.
Serum Calcium:
May be normal.
Bicarbonate (HCO3):
Falls by 1-2 mmol/L for every 10 mmHg decrease in PCO2.
In chronic cases, the fall is about 5-7 mmol/L.
Possible treatment of respiratory Alkalosis
Treatment
Treat Underlying Cause:
Address the primary condition causing respiratory alkalosis.
Sedation:
Used for anxiety and hysteria.
Re-breathing into a Paper Bag:
Helps increase CO2 levels in the blood.
What’s Mixed Acid-Base Disorders
Mixed acid-base disorders occur when a patient has more than one type of acid-base imbalance simultaneously.
What are the causes & features of Respiratory and Metabolic Acidosis
Cardiopulmonary arrest
Drug overdose (sedatives and narcotics)
Severe pulmonary edema
Featurees
Features:
Blood pH: Low
Plasma Bicarbonate (HCO3): Low
PCO2: High
What are the causes & features of Respiratory and Metabolic Alkalosis
Causes:
Pneumonia associated with severe vomiting
Diuretic therapy in patients with liver failure
Features:
Blood pH: Very high
Respiratory Alkalosis: Low PCO2
Metabolic Alkalosis: Normal or high HCO3
