ACID BASE
DISTURBANCES
Hinkle and Cheever Chapter 10
Acid- base balance
Homeostasis of the hydrogen ion
concentration is Soooo important that the
body is very creative to maintain balance
Balance
• Acid base is a
balanced with a ratio of
1 carbonic acid to 20
parts bicarbonate base
pH - Plasma
pH is an indicator of hydrogen ion concentration: 7.35 - 7.45
Bases can accept hydrogen ions to convert strong acids to weak acids.
• Primary base - bicarbonate HCO3• Lesser bases - hemoglobin, protein, and phosphate (less important
buffer system)
The body’s pH is maintained by:
• Chemical buffering system
• The lungs
• The kidneys
Three Regulatory Systems
• Chemical Buffers – act
immediately
• Bicarbonate, Phosphate,
and protein
• Respiratory System –
uses hypoventilation or
hyperventilation as
needed.
• Kidneys – excretes or
retains acids and bases
as needed
Chemical buffering
• The body’s primary buffer system is:
Bicarbonate (HCO3-) carbonic acid (H2CO3-) in the
plasma
Respiratory Regulation
• When the amount of CO2 (carbon dioxide) produced is not equal
to the amt removed, a CO2 imbalance occurs.
• Chemoreceptor's in the medulla are sensitive to the
concentration of CO2 and alter the rate and depth of
respiration accordingly.
• Either to remove – tachypnea or retain CO2 - bradypnea.
• Carbonic acid - (H2CO3) Carbon dioxide and water combined.
Most abundant body acid.
• Respiratory compensation takes 12-24 hours to work
Renal Regulation
• Maximum response takes 3-4 days
• Regulate bicarbonate (HCO3- Buffer) concentration in the ECF
• Regenerate and reabsorb bicarbonate ions
• In acidosis, the kidneys excrete hydrogen cations (H+) and reabsorb
(conserve) bicarbonate anions (HCO3-).
• To restore the balance with reabsorption of bicarbonate (HCO3-),
Chloride anions (Cl-) are excreted
• In alkalosis, the kidneys retain hydrogen ions and excrete bicarbonate
ions and reabsorb (conserve) chloride anions.
• Renal regulation is through
Renal Regulation
H+, Na+, HCO3- (bicarb).
• H+ excreted into tubules,
combined with HCO3, and forms
H2CO3 (carbonic acid)
• H2CO3 separates and forms
H20 and CO2.
• H2O is excreted and CO2 is
converted back to HCO3
• In acidosis Lots of HCO3 is
produced and in alkalosis little
HCO3 is produced
Na3HPO4 - Sodium phosphate
is alkaline in water
Serum Electrolytes
• State of Acidosis: K+ shifts out of cell and H+ shifts into cell
• State of alkalosis: K+ shifts into cell and H+ shifts out of cell
• State of acidosis: Hco3- is conserved and cl- is excreted
• State of alkalosis: Hco3- is excreted and cl- is conserved
• Anion gap: difference between cations (Na+/K+) and anions
(cl- and HCO3-) in blood.
• The gap reflects unmeasured anions: phosphates, sulfates and
proteins
• >16 results from accumulation of fixed acids (Metabolic acids): lactate,
ketoacids, uremia
• Elevated anion gap is an indication of metabolic acidosis
• Anion gap = Na+ - (Cl- + HCO3-) Normal 8 – 12 mEq/L
• Anion gap = Na+ + K+ - (Cl- + HCO3-) Normal 12 – 16 mEq/L
• The nurse reviews the following laboratory
results
• Na+
145
• K+
3.2
• Cl100
• HCO3- 24
• Calculate the anion gap
• Anion gap = Na+ - (Cl- + HCO3-)
• Is this metabolic or respiratory acidosis or alkalosis??
ABG
pH
7.35-7.45
perfect 7.40
PaCO2
35-45 mm Hg
HCO3
22-26 mEq/L
PaO2
80-100 mm Hg
<Hypoxemia
Base Excess
+ or - 2
O2 saturation
> 94%
Respiratory Acidosis
• Hypoventilation
• Hypercapnia: PaCO2 >45mmHg
• Acute: Drugs, cerebral injury, sudden cardiac arrest, Fx rib,
airway obstruction, pneumonia, congestive heart failure
• Chronic: COPD, cystic fibrosis, sleep apnea, kyphoscoliosis,
brain tumor, obesity,
ROME
resp. acidosis
Respiratory Acidosis - ROME
pH
No
Compensation
Partial
Compensation
Full
Compensation
pH 7.35 - 7.4
PaCO2
Lungs
HCO3
Kidneys
Respiratory Acidosis
Signs and Symptoms
Treatment
• S/S: anxiety, headache, confusion,
lethargy, cyanosis,
Arrhythmias with elevated K+
• PaCO2 >60 -> cerebral vasodilation
and edema
• TX: Oxygen, antibiotics,
bronchodilators, suction,
reposition, chest
physiotherapy, intubation, IV
buffers and lowering K+
• (sodium bicarb) and ringers
lactate IV
• Treat cause
Respiratory Alkalosis
• Hyperventilation
• Hypocapnia: PaCO2 <35 mm Hg
• Stimulation of Respiratory Center: anxiety, fever, pain,
salicylates, gram-neg sepsis,
• Hypoxemia: pneumonia, high altitude, severe anemia,
• Pulmonary disorders: pulmonary emboli, pulmonary
edema, asthma (early)
Resp alkalosis
• S/S: Acute
• Anxiety,
• Lightheadedness: cerebral
vasoconstriction
• Paresthesia: (low Ca+)
• Circumoral numbness
• Dysrhythmias: (Low K+)
• S/S: Severe
• Confusion
• Tetany
• Syncope
• Seizures
• Treatment
• Sedatives, O2,
• Pain medication, IV.9NaCl
• Treat Cause
Respiratory Alkalosis - ROME
pH
No
Compensation
Partial
Compensation
Full
Compensation
pH 7.4 - 7.45
PaCO2
Lungs
HCO3
Kidneys
Metabolic Acidosis
• HCO3- <22 mEq/L
• With acidemia: pH <7.35
• Cause
• Loss of Base: diarrhea, ileostomy, renal failure with decrease
HC03- production, acetazolamide –Diamox (carbonic
anhydrase inhibitor) CO2 + H2O <--CA--> H2CO3 <--> H+ + HCO3-.
Diuretic leading to excretion of base
• Excess Acid Production: ketoacidosis, alcohol & starvation,
DKA, lactic acidosis with anaerobic metabolism (drop in B/P),
• Excess Acid Ingestion: salicylates, cocaine, ecstasy,
methamphetamine
• Inability of kidney to excrete H+ ions: renal failure, K+
sparing diuretics
Metabolic acidosis
• S/S
• Headache
• Confusion drowsiness
• N & V, diarrhea
• Vasodilation: low B/P, tachycardia,
tachypnea
• Severe
• Dehydration: s/s
• Dysrhythmias: hyperkalemia
• Kussmaul’s-rapid/deep compensation
• Stupor, coma
• Treatment
• Sodium bicarbonate (NaHCO3) or
lactate ringers
• Correct underlying disease: dialysis,
Insulin, fluids, glucose
• Check anion gap
• Cause: Pancreatitis, renal or liver
failure, DM, dehydration, diarrhea,
ETOH, ASA, diuretics
Metabolic Acidosis - ROME
pH
No
Compensation
Partial
Compensation
Full
Compensation
pH 7.35 - 7.4
PaCO2
Lungs
HCO3
Kidneys
Metabolic Alkalosis
• HCO3- > 26 mEq/L
• With alkalosis pH >7.45
• H+ ion loss: N/V, NG sx,
• H+ shift out of the cells: hypokalemia, rapid correction post starvation
and Hi PCO2 levels when HCO3- is still elevated
• Hypokalemia: K+ moves out of Vessels and H+ moves into Vessel to
correct
• Bicarbonate retention: bicarbonate antacids intake PO IV or citrate in
blood transfusions.
• Contraction Alkalosis: diuretics (loss of fluids with H+, Cl-, and HCO3-)
HCTZ & lasix
Metabolic Alkalosis
• S/S: Many d/T low
K+/Ca++
• Paresthesia: (low Ca)
• Dizziness
• Muscle weakness (low K+)
• Hyporeflexia (Low K+)
• Dysrhythmia (Low K+)
• Bradypnea: resp compensation
• Severe:
• Tetany : (low Ca)
• Confusion
• stupor
• Treatment
• Correct underlying disease:
• Urine loss of Cl-: stop diuretics
• Low K+: IV KCL
• Isotonic fluid tx diuretic effect
• Acetazolamide: Diamox
(carabonic Anhydrase inhibitor)
blocks HCO3- reabsorption)
Metabolic Alkalosis - ROME
pH
No
Compensation
Partial
Compensation
Full
Compensation
pH 7.4 - 7.45
PaCO2
Lungs
HCO3
Kidneys
Elderly
• High risk group
• Lots of meds: Diuretics
• Poor diet, low Na,
• Co-morbidities: renal,
cardiac, pulmonary,
endocrine,
• Compensation slow!!!
• Risk of falls enhanced with
weakness
• Mrs. R.L., a 68-year-old woman, is being seen in the emergency
department after 3 days of diarrhea. Her son says that his
mother seemed confused and drowsy for the past 2 days. Mrs.
R.L. receives dialysis treatment three times a week, her last
treatment being yesterday. On admission the patient’s vital signs
are:
• blood pressure, 108/56 mm Hg; respiration, 28 breaths/min
(regular, deep and rapid); pulse, 98 beats/min; and temperature,
37º C (98.9º F).
• The results of the arterial blood gases on Mrs. R.L. are:
• pH - 7.32; HCO3 - 20; and PaCO2 - 40.
• What acid-base imbalance does this patient have?
• What are the s/s of this acid base imbalance?
• What are some interventions that can help this patient?
• What caused Mrs. R.L. to have this acid-base imbalance?
• A patient has a 3 day history of nausea and vomiting. ABG
results are:
• pH 7.51
• PaCO2 42 mm Hg
• HCO3 34 mEq/L
• PaO2 92
• What acid base disorder is this acidemia or alkalemia?
• Is it respiratory or metabolic?
• Has compensation occurred?
• What contributed to the condition?
• What s/s would you assess for?
• What treatment is indicated?