Acid-Base Balance Flashcards
Regulators of Acid-Base Balance
-Buffers
- Primary regulators
- Act immediately (within 1 second of abnormal pH)
- Combine w/ acids or base to prevent pH changes (Examples include: Carbonic acid-sodium-bicarbonate, protein & phosphate buffering systems)
Regulators of Acid-Base Balance
-Resp system
- Responds within minutes to hours to changes in acid/base to eliminate or retain CO2.
- Respiratory center in medulla controls breathing
- Increased respirations leads to increased CO2 eliminated from body + decreased CO2 in blood
- Decreased respirations leads to decreased CO2 elimination from body + increased CO2 in blood
Regulators of Acid-Base Balance
-Renal system
- Responds within hours to days (last line of defense; may take hours or days to restore normal hydrogen ion concentration)
- Secretes hydrogen (H+) ions + reabsorbs bicarbonate (HCO3) ions
- Reabsorption + secretion of electrolytes (e.g., Na, Cl)
Acid-Base Balance
-pH
- Measures hydrogen ion concentration in body fluids
- Body maintains a slightly alkaline pH of 7.35-7.45
- Metabolic and respiratory processes work together to keep H+ levels within a normal range
- Increase in H+ makes solution more acidic
- Decrease in H+ makes solution more alkaline
Acid-Base Balance
-PaCO2
- Partial pressure of CO2 in arterial blood
- Reflection of depth of pulmonary ventilation
- Normal range is 35-45 mmHg
Acid-Base Balance
-PaO2
- Partial pressure of O2 in arterial blood
- No primary role in acid-base balance regulation if within normal limits
- Normal range is 80-100 mmHg
- Hypoxemia may cause
-anaerobic metabolism
-hyperventilation
Acid-Base Balance
-Oxygen saturation
- Percentage of Hgb saturated by oxygen
- Normal value is 95-100%
- If PaO2 drops below 60 mmHg, then will see a large drop in saturation
Acid-Base Balance
-Base excess
- Amount of blood buffer that exists
- Normal value is +/- 2
-Base Excess
-Base Deficit
Acid-Base Balance
-Bicarbonate
- Major renal component of acid-base balance
- Excreted + reproduced by the kidneys to maintain normal acid-base
- Principle buffer of extracellular fluids in the body
- Normal range is 22-26 mEq/L
Acid-Base Balance
-Anion gap
- Reflection of anions, not routinely measured
- Normal range is 12 mEq/L (+/-2)
- Increase: Seen with lactic acidosis or ketoacidosis
- Normal: Usually caused by loss of bicarb (i.e. diarrhea, diuretics)
Summary (via professor google)
* AG = (Na+ + K+) - (HCO3 + Cl-)
-w/ potassium given
w/o potassium given, eliminate K+
* Unmeasured anions
* HCO3 decrease is acidosis, but sometimes Chloride increases to maintain anion gap
How to obtain Arterial Blood Gases
- Heparinized syringe
- Blood from an artery
- Make sure at least 15-20 minutes have passed after procedures
- Apply pressure for 5 minutes
- On ice
- Prompt delivery to lab
Acid-Base Balance
-ABG norm values
- pH 7.35-7.45 (7.4)
- PaCO2 35-45 mmHg (acid)
- HCO3 22-26 mEq/L (base)
- PaO2 80-100 mmHg (partial pressure of oxygen in arterial blood)
- SaO2 96-100% (arterial saturation)
Interpretation of ABGs
-Dx in 6 steps
1-Analyze pH
2-Analyze PaCO2
3-Analyze HCO3
4-Determine if PaCO2 or HCO3 matches alteration
5-Compensation?
6-Analyze PaO2 and SaO2
ROME
Respiratory
Opposite
-Alkalosis ↑ pH ↓ PaCO2
-Acidosis ↓ pH ↑ PaCO2
Metabolic
Equal
-Acidosis ↓ pH↓ HCO3
-Alkalosis ↑ pH↑ HCO3
If both respiratory and metabolic components match the pH, maybe it is a _.
If both respiratory and metabolic components match the pH, maybe it is a mixed disorder.
Degree of compensation
-Absent
- pH is not within normal range
- The component that does not match the pH imbalance is still within its normal range
Degree of compensation
-Partial
- pH is not within normal range
- The component that does not match the pH disorder is above or below the normal range
Degree of compensation
-Complete
- pH is within the normal range
- Both components are either above or below normal range
Respiratory Acidosis
- high PaCO2
- d/t alveolar hypoventilation
Respiratory Alkalosis
- low PaCO2
- d/t alveolar hyperventilation
Metabolic Acidosis
- low pH
- low HCO3-
- d/t gain of hydrogen or loss of bicarbonate
Metabolic Alkalosis
- high pH
- high HCO3-
- d/t gain of bicarbonate or loss of hydrogen
IV Fluid Replacement
-Crystalloids
Solutions w/ small molecules that flow easily from the bloodstream into cells & tissues
-General term for iso-/hypo-/hyper-tonic solution
Isotonic Solutions?
- Osmolality 275-290 mOsm/L
- Same concentration of osmotically active particles in ECF
- Osmotic pressure is the same inside & outside
- Fluid does not shift b/w extracellular & intracellular areas
- Therefore good choice for ECF dehydration. Used most commonly.
Isotonic Solutions
-Examples
- Dextrose 5% in water (remember dangers associated with D5W!!)
-provides carbohydrates./causes hyponatremia d/t diluting in fluid
-tx=hypernatremia/provide free water to kidneys - 0.9% Sodium Chloride (Normal Saline), actually 154 mEq Na+
-tx=hemorrhage/vomiting/diarrhea/drainage from GI suction/metabolic acidosis/shock - Lactated Ringers
-tx=burn/trauma pts d/t similar to blood plasma concentration./acute blood loss/hypovolemia from third-space shifts/electrolyte imbalance/metabolic acidosis - Plasmalyte
Hypotonic Solutions?
- Osmolality less than 275 mOsm/L
- Less concentrated than extracellular fluid
- Fluid will move from blood stream into cell
- Used to dilute ECF + rehydrate cells
- Used for hypertonic imbalances
Hypotonic Solutions
-Examples
0.45% Sodium Chloride (1/2 Normal Saline)
tx=hypernatremia/diabetic ketoacidosis
disolving too quickly can cause hemolysis in RBCs
Hypertonic Solutions?
- Solutions w/ osmolality greater than 295 mOsm/L
- Draws fluid from intracellular space, causing cells to shrink + extracellular space to expand
Hypertonic Solutions
-Examples
- Dextrose 5% in half normal saline solution
- Dextrose 5% in normal saline solution
- Dextrose 10% in water
- 3% Saline
Colloids?
- Plasma expanders used if blood volume does not improve w/ crystalloids
- Pulls fluid into bloodstream
- Needs close monitoring d/t risk of volume overload=not used as first-line tx
Colloids
-Examples
Solutions w/
* Albumin
* Dextran
Needle Gauges
- Higher the gauge, smaller diameter of angiocath
- Increased fluids over short amt of time
- Routine IV fluid administration
IV
-Regulation & maintenance
- Assessment
- Infiltration
- Phlebitis
- Review complications
- Dressing
- Changes/tubing changes
- Site Changes
Transfusions?
- Restores blood volume or corrects deficiencies in blood’s oxygen carrying capacity or coagulation components
- Requires consent
- Review in Taylor & Hinkle:
-Administration
-Assessment
-Symptoms of transfusion reaction
-Interventions for reaction
Respiratory Acidosis
-Causes
- Acute resp dz
- pulmonary edema
- aspiration of foreign body
- actelactasis
- overdose of secative or anesthetic
- cardiac arrest
- chronic resp dz
- emphysema
- bronchial asthma
- cystic fibrosis
- inadeq mechanical ventilation
- CNS depression
- neuromuscular dz
Respiratory Acidosis
-S/s
- Acute respiratory acidosis
- mental cloudiness
- dizziness
- muscular twitching
- unconsciousness
- chronic respiratory acidosis
- weakness
- dull headache
Respiratory Acidosis
-Tx(s)
- directed at improving ventilation
- pharmacologic measures
- pulmonary hygiene measures
- adequate hydration
- supplemental O2
- Mechanical ventilation to correct disorder but must be used cautiously to decrease PaCO2 slowly
Respiratory Alkalosis
-Causes
- hyperventilation
- extreme anxiety MOST COMMON CAUSE
- hypoxemia
- high fever
- early sepsis
- excessive ventilation by mechanical ventilator
- CNS lesion involving resp center
Respiratory Alkalosis
-S/s
- lightheadedness
- inability to concentrate
- hyperventilation syndrome
- tinnitus=ringing in ears
- palpitations
- sweating
- dry mouth
- tremulousness
- convulsions & LOC
Respiratory Alkalosis
-Tx(s)
- if anxiety, encourage pt to breathe more slowly or breath in closed system=paper bag, to accumulate CO2./sedative may be neccessary in extreme anxiety
- if other causes, correct underlying problem
Metabolic Acidosis
-causes
- diarrhea
- intestinal fistulas
- parenteral nutrition
- excessive intake of acids (such as Salicylates)
- diabetic ketoacidosis
- renal failure
- starvational ketoacidosis
Metabolic Acidosis
-S/s
- headache
- confusion
- drowsiness
- increased resp rate & depth
- Nausea & vomiting
- peripheral vasodilation
- hyperkalemia, freq present
Metabolic Acidosis
-Tx(s)
- aimed at correcting metabolic deficit
- if excessive intake of chloride, focus on eliminating source. admin bicarb, when neccessary
Metabolic Alkalosis
-causes
- vomiting or gastric suction
- hypokalemia
- potassium-wasting diuretic
- alkali ingestion (bicarb-containing antacids)
- renal loss of H+ (ex: from steroid or diuretic use)
Metabolic Alkalosis
-S/s
- dizziness
- tingling of fingers & toes
- hypertonic muscles
- depressed respirations (compensatory)
- hypokalemia may be present
Metabolic Alkalosis
-Tx(s)
- aimed at reversal of underlying disorder.
-sufficient chloride must be supplied for kidney to absorb sodium w/ chloride (allows excretion of excess bicarb)
-tx also incl admin of NaCl to restore normal fluid volume
