E2- ABGs Flashcards
- In order to ensure optimal function of __________ function, acid-base balance is tightly regulated at what pH?
- changes in [] of F/E - changes waters ability to ____?
- 1831 = O’Shaughness discovrered ?? in what pts?
- enzymatic
- 7.35 to 7.45
- auto-ionize
- loss of carbonate of soda in CHOLERA pts
What causes acidemia?
- Excess production of H+ (in relation to hydroxyl ions)
What causes alkalemia?
- Excess production of OH- (in relation to hydrogen ions)
OH = hydroxyl ions
What is known as the measured hydrogen concentration?
- pH
The Power of Hydrogen
The stability of pH is managed by what 3 factors?
- CO2 = enters/leaves the body via lungs
- HCO3 = enters/leaves the body via kidneys = via proximal tubule
- H+ = reabsorbed = via distal tubule + collecting duct
What is the equation to calculate “acid-base balance”?
Henderson-Hasselbalch equation
pH = 6.1 + log [ serum bicarb / (0.03 x PaCO2) ]
- Water can be acid or base + is considered ______?
- _____ is a strong acid that _______ proton w/ water
- _____ is a strong base that ______ proton w/ water
- amphoteric
- HCl - donates to water
- KOH - receives from water
- Degree of dissociaition in water determines what?
- _____ has a pKa of 3.4 ,, completely dissociates = strong acid
- ______ has a pKa of 6.4 ,, partially dissociates = weak acide
- strength
- lactic acid
- carbonic acid
3 rules
Describe Electrical Neutrality
o Add all positive + negative charges – should be EQUAL to each other
3 rules
Describe Dissociation Equilibria
o The propensity of substance to dissociate
o Put chunk of substance into water + it wants to break up
3 rules
Describe Mass Conservation
o The amount of substance remains constant
o Not in size ,, but amount
o Cannot create or lose substance unless another process interfering
What is the most abundant ECF strong cation + anion?
Other ones?
**Na+, Cl- **
K+, SO42-, Mg2+, Ca2+
- Thestrong ion difference is the ability of ECF to maintain a more _______ environment.
- It is an __________ predictor of pH
- Equation?
- positive
- independent
- total = strong cations - strong anions
- acid-base disorder= primary disorder with secondary compensation?
- acid-base disorder = mixed acid/base problem?
- Both PaCO2 + HCO3 change in same direction
- PaCO2 + HCO3 in different directions
What is the Acid/Base Disorder
pH: 7.34
PCO2: 48
HCO3: 24
Uncompensated Respiratory Acidosis
What is the Acid/Base Disorder
pH: 7.58
PCO2: 38
HCO3: 29
Uncompensated Metabolic Alkalosis
What is the Acid/Base Disorder
pH: 7.28
PCO2: 46
HCO3: 18
MIXED met/resp acidsois
What is the Acid/Base Disorder
pH: 7.48
PCO2: 32
HCO3: 22
Uncompensated Respiratory Alkalosis
probs starting to compensate
5 Cardiovascular Consequences of Acidosis
- Impaired contractility = pH 7.2
- Decreased arterial bp
- Sensitive to re-entry dysrhythmias
- Decrease threshold for V-fib
- Decreased responsiveness to catecholamines = pH 7.1
CBD is VC (very cool)
2 Nervous System Consequence of Acidosis
- Obtundation
- Coma
3 Pulmonary Consequences of Acidosis
- Hyperventilation (d/t compensation, blowing off CO2)
- Dyspnea
- Respiratory Muscle Fatigue
3 Metabolism Consequence of Acidosis
- Hyperkalemia (contributes to reentry dysrhythmias)
- Insulin Resistance
- Inhibition of anaerobic glycolysis
Define Respiratory Acidosis
- An acute decrease in alveolar ventilation resulting in increase PaCO2
- pH < 7.35
- Caused by respiratory failure
What are the causes of Respiratory Acidosis?
- Drug-induced ventilatory depression
- Permissive hypercapnia
- Upper airway obstruction
- Status asthmaticus
- Restriction of ventilation (rib fx, flail chest)
- Disorder of neuromuscular function
- MH
- PNA/ Pulmonary Edema, Pleural Effusion
How do we cause Resp Acidosis?
inadequate NMBD reversal
opioid excess
CO2 insufflation
What are the 3 categories that can cause Respiratory Acidosis?
- Central ventilation control (neuro/brain)
- Peripheral ventilation control (neuromuscular disease)
- VQ mismatch (Pneumonia)
ACUTE hypercarbia, how long does it take for the bicarb to compensate for the acid-base disorder?
PaCO2 increases by 10 mmHg = increase _______ mEq/L of HCO3- for system to be compensated
- Very slowly (2-3 days)
- Increase in **1 mEq/L **of HCO3 for every 10 mmHg of PaCO2
COPD from 40 > 50 ,, Bicarb from 24 >25
How much will HCO3- increase with compensated CHRONIC hypercarbia?
- ↑ PaCO2 of **10 mmHg **= ↑ HCO3- by 3 mEq/L
This is prevalent in COPD patients
Upon arrival at the ICU, the patient has a PaCO2 of 80 mmHg.
What is the expected HCO3 if this patient has compensated ACUTE hypercapnia?
* 28 mEq/L
Normal PaCO2 : 40 mmHg
Normal HCO3 : 24 mEq/L
PaCO2 = =80 mmHg
PaCO2 **increased by 40 mmHg **
For acute hypercapnia, every 10 mmHg PaCO2 = ↑HCO3 by 1 mEq —- increase by 4
Below 28 = add aggressive treatment bc body not compensate
Upon arrival at the ICU, the patient has a PaCO2 of 80 mmHg.
What is the expected HCO3 if this patient has compensated CHRONIC hypercapnia?
* 36 mEq/L
Normal PaCO2 level: 40 mmHg
Normal HCO3 level: 24 mEq/L
PaCO2 of the patient is 80 mmHg
PaCO2 increased by 40 mmHg
Chronic Hypercapnia: ↑PaCO2 10 mmHg=↑HCO3- 3 mEq
HCO3- increase by **12 mEq/L **
Expected HCO3- = 24 + 12 = 36 mEq/L
What would be the treatment for respiratory acidosis :: if hypercarbia is marked + CO2 narcosis is present?
- Mechanical Ventilation
Why should there be caution with chronic hypercarbia reversal with bicarb?
- Excessive bicarb will cause CNS irritability»_space; seizures
Define Metabolic Acidosis.
- A lowered blood pH - stimulates respiratory center to hyperventilate
- Metabolic Acidosis is secondary to an underlying disorder (fix the problem to fix acidosis)
Respiratory compensation does not fully counter excessive acid production
Metabolic Acidosis is associated with alterations in transcellular ____________ and ↑ ionized calcium.
- ion pumps
What direction will the Oxygen-Hemoglobin Dissociation Curve shift with Metabolic Acidosis?
- Rightward Shift
- This will allow O2 to be released and available to the tissues
What is your expected PaCO2 if your HCO3- is 12 mEq/L?
- PaCO2 = 26 mmHg
- If PaCO2 is HIGHER 26 mmHg, compensation is INADEQUATE
**PaCO2 = (1.5 x HCO3-) + 8 **
= (1.5 x 12) + 8
= 26 mmHg
For every 1 mEq/L of negative base excess, PaCO2 should fall ______ mmHg.
- 1.2 mmHg
- otherwise inadequate compensation
A normal anion gap maintains __________.
- Electrical neutrality
Bicarb loss is countered by the net gain of ______ ions. Often called ?
- Chloride ions
- often called hyperchloremic metabolic acidosis
3 cause metabolic acidosis + normal anion gap.
- Sodium Chloride Infusion
- Diarrhea
- Early Renal Failure
Sure dad extra little kidneys really poop (suck)
What defines a high anion gap?
- > 20 mEq/L
- Additional acid that is added to extracellular space
- Acids dissociates into H+ - combine with bicarb - form carbonic acid - decrease available bicarb
4 Causes of high anion gap.
- Lactic Acidosis
- Ketoacidosis
- Renal Failure
- Poisoning
Sure dad extra little kidneys really poop (suck)
Mneumonic for High Anion Gap Acidosis
* CAT MUDPILES
- C: Cyanide + CO
- A: Arsenic
- T: Toluene
- M: Methanol + Metformin
- U: Uremia
- D: DKA
- P: Paraldehyde
- I: Iron
- L: Lactate
- E: Ethylene glycol
- S: Salicylates
What is the simple anion gap formula?
What is the range of a simple anion gap?
- Sodium - (Chloride + Bicarb)
- 12-14 mEq/L
What is the conventional anion gap formula?
What is the range of a conventional anion gap?
- (Sodium + Potassium) - (Chloride + Bicarb)
- 14-18 mEq/L
Anion Gap frequently ___________ (overestimates/underestimates) the extent of acid-base disturbances.
- Underestimates
- complicated by hypo-albumin ,, hypo-phosphate
This is complicated by hypoalbuminemia and hypophosphatemia
Lactic Acidosis
How do you treat metabolic acidosis?
- Treat the cause!
Treatment for Metabolic Acidosis related to Ketoacidosis.
- Insulin and fluids
Treatment for Metabolic Acidosis related to Lactic Acidosis.
- Improve tissue perfusion
- Dc Metformin
- fluids
Treatment for Metabolic Acidosis related to Renal Failure.
- Dialysis
What are the parameters to treat metabolic acidosis with sodium bicarbonate?
- pH **< 7.1 **
- HCO3- < 10 mEq/L
What are the negative effects of administering bicarb to someone with metabolic acidosis?
- Bicarb will react with H+ ion and generate CO2 which will diffuse intracellularly and decrease pH
- In chronic metabolic acidosis, acute pH changes negate the right shift curve (Bohr effect) and cause tissue hypoxia
The administration of IV NaHCO3 to treat metabolic acidosis should be reserved for the emergency treatment of select conditions
Formula for HCO3- Correction Dose
- Dose of Bicarb = 0.3 x Base Deficit x Wt (kg)
- Give 1/2 dose
Oftentimes, you would give half this dose and reassess
2 reasons treat with bicrb is controversial?
- reacts with H to decrease pH more
- in chronic met. acidsosis - pH change negates Rigth shit + can’t get oxygen to tissue
What happens to elective surgery if the patient experience acute metabolic acidosis?
- Surgery will be postponed
Anesthesia management considerations for urgent/emergent surgery with metabolic acidosis.
- Hemodynamic monitoring
- Give Fluids
- Monitor Cardiac Functions
- Frequent Lab - POCUS q30 min
Define Respiratory Alkalosis.
- An acute increased alveolar ventilation
- Results in ↓ PaCO2 and pH > 7.45
What are 5 causes of Respiratory Alkalosis?
- Anxiety
- Pregnancy
- High Altitude (↑RR)
- Salicylate overdose (asprin)
- Iatrogenic hyperventilation (during perioperative period/ fear)
- What does decrease PaCO2 cause?
- What are the symptoms of Respiratory Alkalosis?
- Decrease PaCO2 will cause vasoconstriction
- Lightheadedness
- Visual disturbance
- Dizziness
Respiratory Alkalosis will result in greater binding of calcium to ________.
- Albumin
Patient will be hypocalcemic.
What are the signs and symptoms of hypocalcemia?
- Paresthesia, muscle spasm, cramp, tetany, circumoral numbness, seizures
- Trousseau’s sign
- Chvostek’s sign (Irritability on the facial nerve)
Anesthesia management of respiratory alkalosis.
- Consider what is causing the hyperventilation (anxiety)
- Consequence of Pain, Full Bladder, Agitation
- Poor mechanical ventilation strategy
- Therapeutic Hyperventilation
Define Metabolic Alkalosis.
- Marked increase in plasma bicarb usually compensated by an increase in CO2
- Renal or extrarenal causes
- Net loss of H+ or a net gain of bicarb
- excess citrate
What are other names for Metabolic Alkalosis?
* Volume depletion alkalosis
* **Volume overload **alkalosis
What are 6 causes of Metabolic Alkalosis?
- getting rid of acid !
- Hypovolemia
- Vomiting
- NG suction
- Diuretic Therapy
- Bicarb administration
- Hyperaldosteronism (Conn’s ↑ Na+, ↓ K+)
Symptoms of metabolic alkalosis?
d/t calcium imbalance
o Lightheadedness, tetany, paresthesia
Treatment for Metabolic Alkalosis?
- Treat the cause!
Treatment for Metabolic Alkalosis related to volume depletion.
- Saline fluid resuscitation
Treatment for Metabolic Alkalosis related to gastric loss.
- Proton Pump Inhibitors
Treatment for Metabolic Alkalosis related to loop diuretics.
- Potassium-sparing diuretics (Spironolactone)
