Lactic Acidosis Overview

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Questions and Answers

What is lactic acidosis and what causes it?

Lactic acidosis is a condition characterized by an accumulation of lactic acid in the blood, causing a decrease in blood pH, primarily due to tissue hypoxia.

Explain how pyruvate relates to lactic acidosis during exercise.

During exercise, pyruvate combines with NADH to form lactate, leading to increased lactate production.

Identify two medications that can impair oxidative phosphorylation and contribute to lactic acidosis.

Antiretrovirals and metformin are two medications that can impair oxidative phosphorylation.

What is the significance of increased anion gap in diagnosing lactic acidosis?

Increased anion gap suggests the presence of unmeasured anions, which can indicate lactic acidosis. Signup and view all the answers

What is the first step in managing hyponatremia?

The first step is to differentiate between hypotonic and hypertonic hyponatremia. Signup and view all the answers

List one potential cause of pseudo hyponatremia.

High protein levels can cause pseudo hyponatremia. Signup and view all the answers

How do you differentiate acute hyponatremia from chronic hyponatremia?

Acute hyponatremia is defined as occurring in less than 48 hours, while chronic hyponatremia lasts longer than that. Signup and view all the answers

What is the recommended treatment for symptomatic hyponatremia?

Immediate treatment with hypertonic saline is recommended for symptomatic hyponatremia. Signup and view all the answers

What is a common treatment for acute hyponatremia?

A hypertonic saline bolus is commonly used. Signup and view all the answers

What is the maximum recommended rate for correcting chronic hyponatremia?

Correction should not exceed 8 mEq/L per day. Signup and view all the answers

Identify two potential causes of hypernatremia.

Water loss and hypertonic sodium gain. Signup and view all the answers

What is a critical risk factor for developing osmotic demyelination syndrome?

Low baseline sodium levels. Signup and view all the answers

What is the preferred route of correction for hypernatremia?

Oral hydration is preferred. Signup and view all the answers

Which syndrome is characterized by symptoms like high temperature and altered mental status?

Serotonin syndrome. Signup and view all the answers

What is the main treatment for neuroleptic malignant syndrome?

Bromocriptine and dantrolene. Signup and view all the answers

What medication is used as an antidote for acetaminophen toxicity?

N-acetylcysteine. Signup and view all the answers

What inappropriate reaction can occur from the rapid correction of hyponatremia?

Osmotic demyelination syndrome. Signup and view all the answers

How does carbon monoxide toxicity primarily affect the body?

It binds to hemoglobin, reducing oxygen-carrying capacity. Signup and view all the answers

What serious condition can be caused by congenital deficiencies in certain enzymes relating to hemoglobin?

Methemoglobinemia. Signup and view all the answers

Name two symptoms of opioid toxicity.

Constricted pupils and depressed respiratory drive. Signup and view all the answers

What is a typical cause of malignant hyperthermia during surgery?

Use of depolarizing neuromuscular blocking agents. Signup and view all the answers

What is the common treatment for calcium channel blocker toxicity?

Calcium administration. Signup and view all the answers

What are the two types of symptoms seen in cholinergic toxic syndrome?

Diarrhea and bradycardia. Signup and view all the answers

Study Notes

Lactic Acidosis

Lactic acidosis is a condition where there is an accumulation of lactic acid in the blood, causing a decrease in blood pH.
Pyruvate combines with NADH to generate lactate, mainly in skeletal muscles.
Lactate is continuously generated and consumed, with an increase in generation during exercise and seizures.
Mechanisms of Lactic Acidosis:
Most Common: Tissue hypoxia, due to decreased oxygen delivery or microcirculation issues.
Less Common: Stimulation of beta-2 receptors by drugs like epinephrine or albuterol.
Impaired oxidative phosphorylation: Caused by medications like antiretrovirals, metformin, and propofol.
Impaired pyruvate dehydrogenase activity: Caused by thiamine deficiency.
Diagnosis:
Increased anion gap is a clue.
Normal anion gap can occur in about half of cases with high lactate levels.
Lactate levels can be measured in arterial or venous blood.
Higher lactate levels are associated with a worse prognosis.
Management:
Primarily involves treating the underlying cause.
Sodium bicarbonate may be used if pH is less than 7.2, but this is controversial.
Dialysis is a controversial treatment option for severe cases.

Hyponatremia

Hyponatremia is defined as a serum sodium level below 136 mmol/L.
The first step in managing hyponatremia is to differentiate between hypotonic and hypertonic hyponatremia.
Hypotonic Hyponatremia:
Pseudo hyponatremia: A laboratory artifact due to high protein, triglyceride, or cholesterol levels.
Can also be caused by hyperglycemia, mannitol, and hypertonic radiocontrast.
Important Considerations:
Assess hyponatremia severity as acute (less than 48 hours) or chronic.
Consider if the hyponatremia is symptomatic or asymptomatic.
Determine if the hyponatremia is hypovolemic, euvolemic, or hypervolemic.

Hyponatremia (additional causes)

Hyponatremia is most commonly caused by diuretics, polydipsia, and water intoxication.
Other causes include dehydration, heart failure, and medications like haloperidol, diuretics, and others.

Managing Hyponatremia

Determine if hyponatremia is symptomatic.
If symptomatic, treat immediately with hypertonic saline, being careful not to overcorrect.
Obtain urine osmolality. A low urine osmolality (less than 100) suggests polydipsia or beer potomania.
Obtain urine sodium. A low urine sodium indicates decreased effective volume to the kidneys.
A high urine sodium suggests SIADH, adrenal insufficiency, hypothyroidism, or other conditions.

Treatment of Hyponatremia

Treatment depends on the cause and severity.
Acute hyponatremia: Treat with hypertonic saline bolus, followed by continuous infusion if necessary.
Chronic hyponatremia: Fluid restriction for SIADH, normal saline or lactated ringers for hypovolemic hyponatremia, and fluid restriction for hypervolemic hyponatremia.

Overcorrection of Hyponatremia

Rapid correction of chronic hyponatremia or rapid onset of acute hyponatremia can lead to osmotic demyelination syndrome.
Risk factors for demyelination syndrome include low baseline sodium, hypokalemia, alcoholism, malnutrition, and liver disease.
Aim for a correction no more than 8 mEq/L per day.

Hypernatremia

Hypernatremia is characterized by increased serum sodium concentration due to water loss or hypertonic sodium gain.
Water loss can be caused by diabetes insipidus, insensible losses, or hypotonic fluid loss.
Hypernatremia typically occurs in patients with impaired thirst mechanism, such as infants, elderly individuals, and those with altered mental status.

Managing Hypernatremia

Address the underlying cause of hypernatremia.
Correct hypernatremia gradually, aiming for a fall in serum sodium concentration no more than 0.5 mEq/L per hour.
Preferred route of correction is oral hydration; if IV solution is required, use hypotonic fluids.

Drug Poisoning

Drug overdose deaths are a significant public health issue, with fentanyl being the most common cause.
Different drug toxicities present with distinctive signs and symptoms.

Toxic Syndromes

Anticholinergic toxic syndrome: Dilated pupils, dry mucous membranes, altered mental status.
Cholinergic toxic syndrome: Diarrhea, diaphoresis, bradycardia, constricted pupils, bronchorrhea.
Opioid toxic syndrome: Constricted pupils, depressed respiratory drive.
Sympathomimetic toxic syndrome: Dilated pupils, tachycardia, hypertension.

Osmolar Gap

An elevated osmolar gap suggests the presence of an unmeasured osmotic substance, often an alcohol like ethanol, propanol, methanol, or ethylene glycol.

QT Interval Prolongation

Certain drugs can block the potassium efflux, prolonging the QT interval.
These drugs include antihistamines, antipsychotics, some antibiotics (e.g., azithromycin, clarithromycin), antiarrhythmics, macrolides, and methadone.
Maintaining normal electrolytes, especially magnesium, is important in patients with QT prolongation.

Drugs Blocking Fast Sodium Channels

Tricyclic antidepressants, carbamazepine, class 1 & 3 antiarrhythmics, cocaine, phenothiazines, propranolol, verapamil, and others can block fast sodium channels.
Blockage can lead to sine wave pattern on EKG or ventricular tachycardia.
Treatment includes sodium bicarbonate.

Serotonin Syndrome

Serotonin syndrome is typically caused by drug interactions, such as SSRIs with MAOIs, tramadol, or meperidine.
Symptoms include high temperature, altered mental status, rigidity, hyperreflexia, and clonus.
Treatment focuses on supportive care and may include cyproheptadine.

Neuroleptic Malignant Syndrome

Neuroleptic malignant syndrome is typically caused by antipsychotics but can also be caused by dopamine agonists.
Symptoms are similar to serotonin syndrome but with less hyperreflexia, including high fever, altered mental status, rigidity, autonomic instability, and elevated CPK.
Treatment includes bromocriptine and dantrolene.

Malignant Hyperthermia

Malignant hyperthermia is a genetically determined reaction to depolarizing neuromuscular blocking agents or volatile general anesthetics.
Treatment focuses on removing the inciting agents, providing supportive care, and potentially dantrolene.

Antidotes

Acetaminophen toxicity: N-acetylcysteine
Beta blocker toxicity: Glucagon, calcium, vasopressors, insulin plus glucose, lipid emulsion therapy
Calcium channel blocker toxicity: Calcium, glucagon, insulin plus glucose, lipid emulsion therapy
Opioid toxicity: Naloxone
Methanol and ethylene glycol toxicity: Dialysis
Cyanide toxicity: Hydroxocobalamin (most effective), other treatments including nitrates and sodium thiosulfate
Carbon monoxide toxicity: High-flow oxygen

Carbon Monoxide Toxicity

Carbon monoxide toxicity is typically caused by smoking, malfunctioning heating systems, or poorly ventilated motor vehicles.
Carbon monoxide binds to hemoglobin, reducing oxygen-carrying capacity and impairing oxygen delivery.
Diagnosis involves measuring carboxyhemoglobin levels using a co-oximeter.
Treatment involves high-flow oxygen; hyperbaric oxygen therapy may be necessary in severe cases.

Methemoglobinemia

Methemoglobinemia is a condition in which ferrous iron in hemoglobin is oxidized to ferric iron, rendering it unable to bind oxygen.
Congenital forms are caused by deficiencies in cytochrome b5 reductase or NADH-methemoglobin reductase.
Acquired forms can be caused by medications, chemicals, and certain foods.
Symptoms include cyanosis, hypoxemia, and discoloration of blood.
Diagnosis involves measuring methemoglobin levels using a co-oximeter.
Treatment includes methylene blue or ascorbic acid.

Hypothermia

Hypothermia is defined as a core body temperature below 35°C.
Mild hypothermia: 32-35°C
Moderate hypothermia: 25-32°C
Severe hypothermia: below 25°C
Symptoms include shivering, tachypnea, tachycardia, bradycardia, hypoventilation, hyperreflexia, altered mental status, and potential cardiac arrhythmias.
Treatment depends on the severity of hypothermia and may include passive external rewarming, active external rewarming, or invasive techniques.
It is crucial to rule out other potential causes like infection, sepsis, or hypothyroidism.

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Description

This quiz examines the key aspects of lactic acidosis, including its mechanisms, common causes, and diagnostic criteria. Explore how lactic acid accumulation affects blood pH and understand the conditions that lead to this metabolic state. Test your knowledge on the implications of lactate levels in various clinical situations.