Acid-Base Disorder Flashcards
Acid/Base
What is the normal pH from arterial blood gas?
7.35-7.45
Acid/Base
What is the normal PaCO2 from arterial blood gas?
35-45
Acid/Base
What is the normal PaO2 from arterial blood gas?
80+
Acid/Base
What is the normal HCO3- from arterial blood gas?
22-26
Acid/Base
What is the normal BE from arterial blood gas?
-2 to +2
Acid/Base
What are the homeostasis mechanisms for acid/bases?
- buffers
- lungs
- kidneys
Acid/Base
What buffers does the body have to maintain acid/base homeostatsis?
- bicarb (HCO3-)
- carbonic acid
- phosphate
- proteins
Acid/Base
What is the mechanism for metabolic acidosis/alkalosis?
bicarb (HCO3-)
too much= acidosis, too little= alkalosis
Acid/Base
What is the compensatory mechanism for metabolic acidosis?
decreasing paCO2 via increased respiratory rate (expelling CO2)
metabolic acidosis= too much bicard (HCO3-)
Acid/Base
What is the compensatory mechanism for metabolic alkalosis?
increasing paCO2 via respiration changes
metabolic alkalosis= too much bicarb (HCO3-)
Acid/Base
What is the mechanism for respiratory acidosis/alkalosis?
CO2
acidosis= too much CO2, alkalosis= too little CO2
Acid/Base
What is the compensatory mechanism for respiratory acidosis?
increasing bicarb (HCO3-)
Acid/Base
What is the compensatory mechanism for respiratory alkalosis?
decreasing bicarb (HCO3-)
Acid/Base
How is anion gap calculated for metabolic acidosis?
AG= (Na+) - (Cl- + HCO3-)
all drawn from BMP
Acid/Base
How is an anion gap determined for metabolic acidosis?
AG > 12 mEq/L
Acid/Base
How can albumin effect the anion gap?
low serum albumin with decrease the apparent anion gap (mask the gap) so use: AG (corrected)= AG + 2.5(4.5-[albumin])
Acid/Base
What are the causes of anion gap metabolic acidosis?
- Methanol
- Uremia
- DKA (most common)
- Paraldehyde
- Iron/isoniazid
- Lactic acidosis
- Ethylene glycol
- Salicylates
MUDPILES
Acid/Base
What are the causes of non-anion gap metabolic acidosis?
- Ureteral diversions
- Saline infusions
- Exogenous acid
- Diarrhea
- Carbonic anhydrase inhibitors
- Adrenal insufficiency
- Renal tubular acidosis
USEDCAR
Acid/Base
What are the signs and symptoms of metabolic acidosis?
- hyperventilation
- tachycardia
- decreased cardiac output, hypotension
- anorexia, nausea, vomiting
- hyperglycemia
- increased protein catabolism
- hyperkalemia
Acid/Base
What is the treatment for metabolic acidosis?
- treat underlying cause
- normalize fluid status, oxygenation, perfusion, and cardiac output
- administer sodium bicard or THAM
- adjust ventilator, lower CO2
- add acetate (base) to TPN
Acid/Base
What is the dosing of sodium bicarbonate for the treatment of metabolic acidosis?
HCO3- (mEq) deficit= 0.5 x weight (kg) x [24- serum HCO3- (mEq/L)]
Give 1/4-1/2 of dose initially over several hours, then give 1/2 dose as continuous IV over next 24 hours
Acid/Base
What is the strength in 1 amp of sodium bicarbonate?
50mEq= 50mL
Acid/Base
What are the administration options for sodium bicarbonate?
- D5W has no Na+ and 150 mEq may be added
- 1/2NS has 77 mEq of Na+ so 100mEq may be added
NS and LR are not generally used because Na+ /L will be exceeded and minimal sodium bicarbonate can be added
NTE 180 mEq/L of Na+ in IV fluids
Acid/Base
What are the monitoring parameters while on sodium bicarbonate?
- pH (goal 7.2 or greater- AVOID overcorrection!)
- bicarb (goal 10-15 mEq/L- AVOID overcorrection!)
- Na+
- K+
- clinical status
Acid/Base
What is the use of tromethamine (THAM) in metabolic acidosis?
patients that cannot tolerate sodium load from sodium bicarbonate
Acid/Base
What is the dosing of tromethamine (THAM)?
THAM (mL)= weight (kg) x base deficit (mEq/L) x 1.1
given IV over 1 hour
Acid/Base
What are the monitoring parameters while of tromethamine (THAM)?
- pH
- bicarb
- K+
- blood glucose- may cause hypoglycemia
- clinical status
DO NOT OVERCORRECT!
Acid/Base
What are the causes of metabolic alkalosis?
- Diuretics/diuresis
- Iatragenic gain of bicarb
- TPN
- Contraction alkalosis
- Hypokalemia
- Emesis
- Suctioning
DITCHES
Acid/Base
What are the signs/symptoms of metabolic alkalosis?
- arterior constriction
- reduction in coronary blood flow
- hypokalemia, tetany
- seizures, delirium
Acid/Base
What are the classifications of metabolic alkalosis?
- saline responsive (most common), Cl- (urine) < 10-15 mEq/L
- non-saline responsive, Cl- > 25 mEq/L
Acid/Base
What is the treatment for saline responsive metabolic alkalosis?
- replace volume= NS = 20-40 mEq KCl/L @ 100-200 mL/h
- acetazolamide
- potassium supplementation
Acid/Base
What is the treatment for non-saline responsive metabolic alkalosis?
- spironolactone (aldosterone inhibitor)
- ACE inhibitor
- sodium restriction
- potassium supplementation
caused due to mineralcorticoid excess and potassium imbalance
Acid/Base
What is the dosing of Acetazolamide?
250-500 mg IV push 1 x dose over 3 mins, may repeat as needed
also avaliable PO
Acid/Base
What drug for acid/base disorder must be avoided in patients with sulfa allergy?
acetazolamide
Acid/Base
What are the monitoring parameters while on acetazolamide?
- pH (goal= 7.4 or less)
- bicarb (goal= maintain 20 mEq/L or greater)
- chloride
- Cl- (urine)
- clinical status
AVOID OVERCORRECTION
Acid/Base
What is contraction alkalosis?
excessive fluid loss (specifically loss of H+, K+, Cl-), typically caused by diuretics but amount of bicarb stays the same
Acid/Base
What are the causes of respiratory acidosis?
hypoventilation
- CNS depression
- medications (sedatives, opioids)
- neuromuscular disorders
- chest wall abnormalities
- disorders affecting gas exchange
- airway obstruction
Acid/Base
What are the signs/symptoms of respiratory acidosis?
- mental status changes
- seizures
- headache
- blurry vision
- anxiety -> tremors, delirium, coma
- increased cerebral blood flow
- increased CSF pressure
Acid/Base
What is the treatment for respiratory acidosis?
- treat underlying disorder
- supply oxygen
- corticosteroids/bronchodialators
- mechanical ventilation
Acid/Base
What are the causes of respiratory alkalosis?
hyperventilation
- often induced by stressor= anxiety, pain
- hypoxemia, pulmonary embolism
- infection
- pneumonia
- sepsis
Acid/Base
What are the signs/symptoms of respiratory alkalosis?
- cerebral vasoconstriction
- lightheadedness
- confusion
- syncope
- paresthesias, numbness around mouth
- somatic symptoms (chest tightness, dyspnea)
Acid/Base
What is the treatment for respiratory alkalosis?
- treat underlying cause
- reassurance
- brown paper bag
- breath holding techniques
- mechanical ventilation
