Acid-Base Disorders Flashcards
Differentiate between acidemia and acidosis
Acidemia is a decreased blood pH (normal is 7.36-7.44)
Acidosis is a clinical process in the body that decreases blood pH
Differentiate between alkalosis and alkalemia
Alkalemia is an increased blood pH (normal is 7.36-7.44)
Alkalosis a clinical process in the body that increases blood pH
What are the terms for increased and decreased CO2 in the blood?
Hyperkanpia - increased Co2
hypokapnia - decreased pCO2
What is minute ventilation measured in?
What is the calculation?
L/min
MV= RR*VT
MV: minute ventilation
RR: respiratory rate
VT: Tidal volume
What do we call increased or decreased minute ventilation?
Hyperventilation and hypoventilation
Hyperventilation leads to… (as far as pCO2)
Hypokapnia
Hypoventilation leads to what with regard to pCO2?
hyperkapnia
Respiratory acidosis and alkalosis are clinical processes that occur due to increase or decrease in ventilation and usually associated with?
Pulmonary diseases
WHAT… is the henderson-hasselbach equation for blood pH?
¨pH = 6.1 + log [HCO3-/(0.03 x pCO2)]
Hypoventilation leads to…? which leads to?
hyperventilation –> hyperkapnia –> respiratory acidosis
What are three processes/events that lead to metabolic acidosis?
Over-production or accumulation of acid
Loss of base (HCO3-)
Under-excretion of acid
What are two things that lead to metabolic alkalosis (super general here)?
Loss of acid
Under-excretion of base
What does a primary acid-base disorder result from?
pathological process
What does a secondary acid-base disorder arise from?
Secondary acid-based “disorder” is a normal physiological compensation in response to a primary acid-base disorder
What is the timeline for compensation in acid-base disorders?
Buffering - occurs within minutes
respiratory compensation (in metabolic disorders) - within hours
metabolic compensation by kidneys - 2 to 3 days
What is the normal pCO2?
40 mmHg
What is the normal [HCO3-]?
24mM
Acute acid base disorders result from conditions that develop within hours of presentation. What are acute respiratory disorders considered to be?
Uncompensated - resulting in acidemia or alkalemia
Chronic respiratory disorders are considered?
Fully compensated
Characterize the compensation for metabolic disorders.
fully or partially compensated depending on the degree of the acidosis/alkalosis and on a lung function
What are the two causes of respiratory acidosis?
From hypoventilation…
- decreased RR
- decreased Tidal Volume
What are three examples given to us that decrease respiratory drive?
Drugs
Coma
Stroke
What are five or so examples of conditions that can decrease tidal volume
Neuro-muscular disorders
Severe kyphoscoliosis
Airways obstruction
COPD
Obstructive sleep apnea/Obesity
What are the two broad types of metabolic acidosis?
Normal anion gap acidosis
High anion gap acidosis
How do you calculate anion gap?
A.G.=Na+– HCO3- - Cl-
Anion gap represents unmeasured anions in the plasma, what are some examples of these?
Anionic proteins (albumin)
Phosphate
Sulfate
Organic anions
What are the causes of high AG metabolic acidosis?
- Methanol
- Uremia (End Stage Renal Disease)
- Diabetic ketoacidosis
- Paraldehyde
- Infection, Iron, Isoniazide
- Lactic acidosis
- Ethylene glycol (antifreeze), alcohol
- Salicylates, starvation ketoacidosis
MUDPILES - to remember
When do you see uremic acidosis?
What is it due to?
¨Occurs when renal function is severely decreased (Creatinine clearance is less than 25ml/min)
decreased excretion of acids
decreased excretion of H+
Decreased reabsorption/synthesis of HCO3
What are some examples of conditions that lead to anaerobic metabolism in tissues and can lead to lactic acidosis?
- Hypoxemia
- Circulatory failure (hypotension, sepsis)
- Peripheral vessels blockage
- Anemia
What are some medications that are known to cause lactic acidosis?
Looking for 3 here.
Metformin
Some HIV meds
Isoniazide (toxic levels)
What are some non-medicinal and non-anaerobic causes of lactic acidosis?
Liver failure due to decreased clearance
Thiamine deficiency
Hypophosphatemia
Sepsis (due to decreased perfusion of the tissues, impaired gluconeogenesis and poor clearance)
Seizures (due to release of lactate from muscles)
Describe the process of DKA from insulin deficiency to acidosis!
- Insulin deficiency
- increased lipolysis
- increased fatty acid delivery to the liver
- production of ketones
- acidosis
¨Large ethanol intake leads to altered hormonal and enzymatic activities leading to increase in?
ketones production and consequently alcoholic ketoacidosis
What is a normal osmolal gap? How is this calculated?
normal is less than 10
OG= measured serum Osmolality - calculated serum osmolality
OG should be equal to the (ethanol level/4.6) if ETOH is the culprit, if it is more than that then?
Look for other alcohols.
Ethylene glycol is found in antifreeze and in industrial solvents. Its metabolites are highly toxic and it will increase OG. What are two things you likely will see in a patient with ethylene glycol induced alcohol acidosis?
Calcium oxalate crystals in urine
acute renal failure is common
Methanol is found in wood alcohol and windshield fluid and increases OG. What are two common consequences of methanol consumption?
Blindness
Acute renal failure
Salicylate poisioning may cause metabolic acidosis and/or respiratory alkalosis. What are six common symptoms a patient with this type of poisoning may present with?
Hemorrhage
Fever
nausea and vomiting,
Diaphoresis
Tinnitus
Pulmonary edema
What are some causes of normal AG metabolic acidosis?
Diarrhea
Ileal drainage with stoma/bypasses
Decreased reabsorption of bicarb by renal tubules
Increased anion intake (parenteral nutrition)
Large amount of NaCl (expansion acidosis)
What are the three types of renal tubular acidosis?
RTA type I
RTA type II
RTA type IV
(NO TYPE III)
Where in the nephron does RTA type I go down and what is involved?
Decreased hydrogen ions excretion in the collecting ducts leading to alkaline urine and acidic serum
What are some of the likely consequences of RTA Type I?
- Increased calcium excretion and decreased citric acid concentration leading to kidney stone formation
- Increased potassium loss leading to hypokalemia
Where does RTA type II arise in the nephron? What is involved?
Proximal tubules.
Due to a defect in bicarb reabsorption, so more bicarb is excreted, lowering serum bicarb and leading to acidemia and elevated urinary bicarb.
Does RTA type II predispose patients to nephrolithiasis?
Rarely, although there is increased Ca++ in the urine the normal citric acid concentration prevents stone formation.
What is the urine pH like in a patient with RTA type II?
¨Because distal tubules work OK, ability to acidify urine in response to acidemia is intact, so urine pH is low.
What does a patient’s potassium level look like if they have RTA type II?
Hypokalemia due to high K loss.
I what patients does RTA type IV occur? What is it due to?
Occur in patient with moderate chronic renal failure
Due to insufficient aldosterone production (hypo-reninemic) and/or aldosterone tubular resistance (due to renal failure)
What impact does RTA type IV have on a patients potassium levels?
¨Insufficient K excretion leads to hyperkalemia
Urine pH in Type I RTA?
>5.5
Urine pH in Type II RTA?
<5.5
Urine pH in Type IV RTA?
<5.5
Serum K+ In RTA I, II and IV
I: low
II: Low
IV: high
Kidney stones in RTA types I, II and IV?
I: yes
II: no
IV: no
What is urinary anion gap used for?
Differentiate between renal and extrarenal bicarb loss
urinary ion gap is calculated by?
UG= (Na++K+)-Cl-
If urinary anion gap is negative, then? What causes this?
This indicates extrarenal loss of bicarb.
This is due to high levels of unmeasured NH4+, which is excreted by healthy kidneys as a compensatory mechanism for acidosis.
What is urinary anion gap like in renal loss of bicarb?
Positive or non-existent
Due to low level of NH4+ and increased level of bicarb.
List a bunch of possible causes of respiratory alkalosis, go!
(up to 8)
- Pain
- Anxiety
- Salicylates overdose
- Fever
- Sepsis
- Hypoxia from some pulmonary disorders
- CHF
- Pneumonia
- PE
- Mild asthma
- Mechanical ventilation
What are 4 causes of metabolic alkalosis?
- Vomiting/NG suctioning
- Contraction alkalosis due to increased bicarb reabsorption
- hypokalemia
- recent correction of chronic respiratory acidosis
What are the characteristic clinical manifestations of metabolic acidosis?
- Kussmal respiration
- Nausea/vomiting
- cardiac effects
- neurological effects
- symptoms of underlying disease
What kind of cardiac effects would you see with metabolic acidosis?
Arrhythmia
hypotension
What are the neurological effects associated with metabolic acidosis?
Confusion
lethargy
coma
What are some common clinical manifestations of metabolic alkalosis?
- Decreased respiration (compensatory). This may lead to ineffective respiration and hypoxia
- Neurological
- Parasthesia
- Carpopedal spasm due to secondary hypocalcemia
- Confusion
- Seizures
- Dizziness
- Coma
- Weakness
What are the clinical manifestations of respiratory alkalosis?
- Hyperventilation
- Neurological
- Parasthesia
- Dizziness
- Symptoms of underlying disease
What are the seven steps we should be using to interpret arterial blood gases?
- Look at pH: acidemia (<7.4) vs. alkalemia (>7.4).
- Look at HCO3- to determine if primary process is metabolic or respiratory.
- Determine if process is compensated (chronic), uncompensated (acute), or partially compensated (somewhere in between)
- Calculate anion gap to classify the metabolic acidosis or to determine if there is a mixed disorder with other types of acid-base disturbances
- If anion gap is present, Calculate delta-delta gap to find mixed disorders
- If metabolic disorder, look at pCO2 to determine if additional respiratory process exist.
- Refer back to clinical picture and see if your calculations make any clinical sense
