RENAL- ACID/BASE Flashcards
Which ACID is powerful quick, harmful?
CO2
Which ion is slow, complex, creative for ACIDs?
Bicarbonate
HCO3
TCO2 (on chem panel) ABG (essentially HCO3 is a byproduct of CO2>
How do LUNGS compensate using CO2?
Exhale-fast flexible
INC RR- BLOW OFF CO2 (raises pH)
DEC RR
RESPIRTORY
How do KIDNEYs compensate using HCO3?
save HCO3-inc pH
discard HCO3-dec pH
METABOLIC- RENAL
but OTHER system occure
How dose our body use HCO3 and CO2?
Provides automatic and predictable outcomes
What is the ratio to bicarb and acid?
20 parts bicarb to one part acid (carbonic acid).
pH (pH = potential of Hydrogen).
What is the pH of our extracellular fluid?
7.35 – 7.45pH
Remember 7.40
Means fully compensated
Tells us the CONDITION of the Pt.
What condition results in the accumulation of H+ ions? What is the result and pH?
ACIDOSIS
ACEDEMIA
LOWERED ARTERIAL pH.
too much acid or too little HCO3***
What condition results in the excess of bicarbonate ions? What is the result and pH?
ALKALOSIS
ALKALEMIA,
ELEVATED ARTERIAL pH.
too much HCO3*** or too little acid
What is significant about pH in regards to its value?
ANY small change outside of NORMAL is SIGNIFCANT 7.2 VERY SICK, UNCONSCIOUS <7.0 LIFE THREATENING <6.8 RARE SURVIVAL
PH>8.0 LIFE threatening
How is Acidosis or Alkalosis actually harmful?
-Acidosis
-Shifts the oxyhemoglobin dissociation curve to the right (Bohr effect), most marks INC CO2, temp, H+, (low O2)
-Depression of CNS, hypercarbia
-Disorders of respiration
-Decreased cardiac contractility
-Decreased vascular response to catecholemines and
decreased vascular tone (low blood pressure)
-Interference with pharmacologic agents
- Alkalosis (lowered CO2 or too much HCO3)
- Shifts the oxyhemoglobin dissociation curve to the left- most marks DEC CO2, temp, H+, (high O2)
- Decreased cerebral blood flow, alterations of consciousness
- Over-excitation of CNS resulting in muscle spasm and tetany (severe)
What Indicates need for ABG?
- significant hypoxemia, hypercapnia or Chem panel abnormalities
- Toxicology or the Mystery Patient
- Monitoring effects of therapy (intubated pt’s; DKA, COPD management, etc)
How do we obtain an arterial blood gas?
-Venous (VBG) ok if pH is all you need now becoming common
- Radial artery, Femoral now (big target), Brachial is last
- **Allen’s test every time to verify patency of ulnar artery
- Arterial blood is bright red and fills the tube on it’s own
- LABEL Put specimen on ice
- 5 min. firm pressure at site - you’ve punctured an artery
WHat are THE FOURS?
pH-7.40
CO2-40
HCO3-24
What is “simple” “pure” primary entails?
Primary event results
Compensatory even that leads to min. effect
Which compesatory event takes hours vs sec.
Metabolic take HRS-Kidney deciding
Respiratory takse sec- easy hypervenilation
What are the common Primary Disorders?
RESPIRATORY ACIDOSIS
RESPIRATORY ALKALOSIS
METABOLIC ACIDOSIS (2 types)- w/ ANION GAP OR W/O ANION GAP
METABOLIC ALKALOSIS
What are the FIVE QUESTIONS?
1- pH - acidosis or alkalosis or normal?
- Respiratory or Metabolic?
- Who should be compensating (CO2 or HCO3-)?
- Look at the patient - Is there an anion gap? (automatic metabolic acidosis if AG >20). ALWAYS CALULATE
5 If a metabolic acidosis exists, is it a “pure” or “mixed” disorder?
-Respiratory process other than compensation?
-Rule of 15? Are the CO2 and last 2 digits of pH same?
NO-Winter’s formula?
-If an anion gap >20 exists, is there an additional Metabolic process? Winter’s formula? Calculate the Delta gap or Delta Ratio
- Is this a Primary Respiratory or Metabolic disorder?
Normal CO2 = 35 - 45 or 40
Normal HCO3- = 22 -26 or 24
Which one is abnormal?
HIGH OR LOW
For each, does indicate acidosis or alkalosis?
Which one caused the pH change?
ROME
For simple, single acute acid-base disorders:
LOW pH, HIGH CO2 (lots of acids) = RESPIRATORY ACIDOSIS
HIGH pH, LOW CO2 = RESPIRATORY ALKALOSIS
HIGH pH, HIGH HCO3- = METABOLIC ALKALOSIS
LOW pH, LOW HCO3- = METABOLIC ACIDOSIS
If the CO2 drives the pH in the opposite direction,
primary respiratory disorder exists
If the CO2 and pH move in the same direction (up or down)
primary metabolic disorder exists
What begins immediately which may throw values into confusion?
-Are BOTH the CO2 and HCO3- abnormal?
Compensation begins immediately. CO2, HCO3- values are off a bit, reflecting the attempt.
pH abnormal = acute illness or partial compensation.
-Has there been time for compensation?
-If the compensation doesn’t make sense, there is “mixed disorder” – very common condition
Rare CO2 >55, a respiratory process also present
“Primary respiratory acidosis with adequate metabolic compensation”
“ pH adequate will see how treatment helps
RESPIRATORY ACIDOSIS
pH - low (<7.35), CO2 - high, HCO3- normal or elevated compensation: acute or chronic
Inadequate ventilation - results in retention of CO2
CO2 retention: d/t lung disease or obstruction; muscles or chest wall aren’t working; alveolar ventilation dfx, arterial CO2 goes up; you are unconscious you have stopped breathing (CPR).
- Pulmonary – COPD/emphysema, asthma, pneumonia, aspiration, pulmonary edema, pleural effusion, pneumothorax, smoke inhalation
- Cardiac – cardiac arrest, CHF
- Mechanical – Airway obstruction – infection, foreign body, bronchospasm
- Central/CNS – Neuromuscular Dz (Guilain-Barre, polio, myasthenia gravis, MS, etc), stroke, tumors, CNS infection, anesthetic/paralyzing drugs
RESPIRATORY ALKALOSIS- Most common acid-base disorder.
pH - high (>7.45), CO2 - low, HCO3- normal or low compensation: acute or chronic
Inc RR- excessive removal of CO2.
hyperventilation.
Hypoxia also stimulates respiration - tachypnea.
Disorders
- airway obstruction/bronchospasm, CHF, infection, PE, altitude
- Drugs – stimulants, salicylates (OD), catecholamines
- Central/CNS – tumors, infection, trauma, stoke, fever, sepsis, pain
- Miscellaneous – pregnancy, hyperthyroid, liver failure, ventilator settings
- Anxiety, psychiatric
METABOLIC ALKALOSIS
-pH - high, HCO3- is high, CO2 is usually elevated, compensating (quick)
-Excess of serum HCO3- ions through H+ ion loss
-retention of HCO3-, or
- addition of alkali rich substances.
Kidneys are overwhelmed or sick.
No ABG needed
Chloride Responsive (correction) Causes
-Volume depletion (dehydrated), severe vomiting, diuretics, NG tube
-Fix: IV hydration; replacing sodium/chloride balances the anion/cation pool
-Be aware of hypokalemia. precursor and result
Chloride Unresponsive Causes
-mineralcorticoid excess and severe hypokalemia.
METABOLIC ACIDOSIS
-pH - low, HCO3- low, CO2 is usually low depending on severity of acidosis and compensation.
- Direct Depletion of bicarbonate
- excessive use of Bicarb stores,
- relative acid gain
- decreased renal excretion of H+ ion.
What should you considered in all HIGH anion GAPS during Metbolic acidosis?
M – Metformin, methanol (Sterno) ingestion
U - uremia (think aminoglycosides, NSAID’s)-ARF
D - diabetic ketoacidosis, alcoholic ketoacidosis
P - paraldehyde (liquid sedative - rare anymore), phenphormin (diet pill RX)
I - INH or iron overdose
L - lactic acidosis (post-seizure, sepsis, carbon monoxide, cyanide, etc)
E - ethylene glycol ingestion (antifreeze, wiper fluid)
R – Renal failure, rhabdomyolysis
S - salicylate overdose (aspirin), starvation
What should you considered in an anion gap (>20)? How do you calculate it
a metabolic acidosis automatically, regardless of value of pH, CO2 or HCO3
Calculate all the time in head
WHat is the RULE of 15
Add 15 to HCO3
if pH and CO2 #s are close
if add 15, the sum should match the last #in pH and CO2
-CO2 and last two digits of the pH should be roughly the same (HCO3 10 or >)
fifth question uncovers concurrent processes that may be missed-Determines if something other than just respiratory compensation exists.
Is the anion GAP open or Closed?
calculation of unmeasured anions in the serum.
- Anions negative charge acids.
- In the face of depletion, the body will produce acids compensate. Thus acid disorders only
- drug overdoses
-Anion gap of >18 is significant
Normal AG = 8 to 12 (or 15)
Na- (Cl+HCO3)
Non-Anion Gap (Normal Gap) Metabolic Acidosis.
Direct HCO3- loss (diarrhea most common), or kidney fails to excrete H+ ions.
Another pneumonic – H.A.R.D.U.P.
H – hypoaldosteronism/Addison’s, hyperalimentation
A – acetazolamide (Diamox), spironolactone
R – renal tubular acidosis, renal failure, nephritis
D - diarrhea
U – ureterosigmoidostomy/ileostomy
P – pancreatic fistula
low Delta Gap/Delta Ratio
So how do you know if a mixed disorder exists?? Is there a chronic disorder?
if the CO2 and HCO3- are abnormal in the same direction, a mixed disorder is UNLIKELY but not ruled out, particularly with metabolic conditions and chronic conditions.
Mixed Disorders - Rule Number One:
EXISTS if the pH is NORMAL and the CO2 is ABNORMAL (if no chronic condition exists)
Mixed Disorders - Rule Number Two:
In a “pure” respiratory process:
A change in the CO2 by 10 will change the pH by .08 in the OPPOSITE direction (CO2 changes by 20, pH changes by 1.6, etc)
-If pH is higher than it should be, then a metabolic ALKalosis also exists
-If pH is lower than it should be, then a metabolic acidosis also exists
Mixed Disorders - Rule Number Three:
A change in HCO3- by 10 will change the pH by .15 in the SAME direction (HCO3- changes by 20, pH changes by .30, etc)
-If the pH is higher or lower than it should be, then a respiratory or another metabolic process also exists
CHRONIC ACID-BASE IMBALANCES
- baseline chronic acid base imbalance, but fine and walking a fine line.
- Identify patients at risk for decompensation in the event of acute illness.
- Follow rules for interpreting blood gases, tell us if the compensation attempted by the body is adequate, or acute or chronic.
CHRONIC RESPIRATORY ACIDOSIS
COPD’ers, asthmatics, lung cancer/mass, neuromuscular dz
pH - 7.36 almost normal – due to chronic compensation
CO2->50-60’s
HCO3- around 55
Rule-increase in CO2 by 10 will decrease pH by .03 and increase HCO3- by 3.5
If doesn’t roughly match the patient’s blood gas, there is another problem addition to the chronic problem.
CHRONIC RESPIRATORY ALKALOSIS
hypoxia, CHF, CNS tumors, hyperthyroidism, pregnancy
pH - almost normal
CO2 - low
HCO3- low as well
Rule-decrease in CO2 by 10 will increase pH by .03 and decrease HCO3- by 5
If doesn’t roughly work out, something else
Is this a “pure” metabolic acidosis or a mixed disorder?
-Determines if something OTHER than just respiratory compensation exists
ASK ONLY if ANION GAP metabolic acidosis >20
-“Rule of 15”:
1. HCO3- plus 15 should equal CO2 and last 2 digits of pH, (HCO3 10 or >)
2. CO2 too low? = Primary Respiratory Alkalosis also exists
3. CO2 too high? = Primary Respiratory Acidosis also exists
IF the RULE 15 not roughly the same, calculate if the respiratory compensation to this metabolic acidosis adequate:
Winter’s formula: CO2 = 1.5 x HCO3 + 8 (±2) (use after 12-24hrs)
CO2 too low? = Primary Respiratory Alkalosis also exists
CO2 too high? = Primary Respiratory Acidosis also exists
What Uncovers a hidden/chronic metabolic or respiratory process?
Use only if gap >20
All values are from the Chem panel:
Delta Gap = HCO3 + change in the anion gap (Anion gap-12) (normal 24 +/- 1)
>30 = metabolic alkalosis also exists
<18= non-gap metabolic acidosis also exists
18-30=no addn chronic dz
Example: Na 136, Cl 99, HCO3 10; AG = 136 – (99 + 10) = 27
Delta Gap = 10 + (27 – 12)
10 + 15 = 25
