Week 7 Acid Base Balance

acid-base balance

the process of regulating the pH, bicarbonate concentration, and partial pressure of carbon dioxide of body fluid

acidotic

pH <7.35

Too much acid (H+) or too little base (HCO3-)

optimal

pH 7.35-7.45

PaCO2, HCO3- normal

Alkalotic

pH >7.45

Too much base (HCO3-) or too little acid (H+)

Sources of Acid

Respiratory = CO2

Metabolic = HCO3

Metabolic acids:

• lactic acid

• ketones

Buffering

Body systems “buffer” to maintain pH normal range using:

• Respiratory

• Renal

BicarbProteins

Phosphate

Excretion

• carbonic acid excretion

• metabolic acid excretion

If H+ increases:

HCO3- binds it → forms carbonic acid → becomes CO2 → exhaled.

If H+ decreases:

Reaction shifts the other way.

Respiratory Acidosis

(pH<7.35, HCO3 <20 mmMol/L)

• Reduced respiration (chronic or acute); COPD, MS, airway obstruction, pneumonia, trauma, brain injury, asthma

Symptoms: anxiety, hypoxic changes, headache, shortness of breath, hyperkalemia, arrhythmias

Metabolic Acidosis

(pH<7.35, HCO3 <20mmMol/l)

• Causes: Inability to excrete acid or conserve base, renal disease, severe dehydration, diarrhea, ketoacidosis, aspirin overdose, antifreeze ingestion, alcohol, starvation

Symptoms: hyperkalemia, vomiting, SOB, confusion, anxiety, rapid breathing

Metabolic Alkalosis

(pH > 7.45, HCO3 > 26mmMol/l)

• Causes: gain of base or excretion of acid: vomiting and diarrhea, diuretics, hypokalemia, blood transfusion, TPN, sepsis, liver failure, resp failure

• Symptoms: resp depression, muscle twitching, seizures, LoC

Respiratory Alkalosis

(pH < 7.35, HCO3 <20 mmMol/l)

Causes hyperventilation, mechanical ventilation

Symptoms: tachycardia, rapid breathing, hypokalemia, numbness or tingling, seizures, LoC

Risk factors for Acid-Base Disorders

Resp. Acid: (Respiratory depression = CO2 retention i.e. respiratory issues)

• hypoventilation

• asthma

• COPD

• obesity

• MS

Resp. Alka.: (Hyperventilation)

• stress/anxiety

• pyrexia

• sepsis

• mechanical ventilation

• liver disease

Metabolic Acid.: (Excess acid buildup or loss of bicarb [HCO3])

• chronic renal failure

• diabetes - ketoacidosis

• GI loss - diarrhea

• shock

• heart failure

• ingesting antifreeze

Metabolic Alka.: (Lose hydrogen or have build of bicarb)

• GI loss - excessive vomiting, NG suctioning, diarrhea

• overuses of diuretic

• hypovalemia

• laxatives

• genetic conditions - cystic fibrosis

Nursing Interventions: Respiratory Acidosis

Related to addressing impaired gas exchange:

• O2 admin, O2 sats, Resp assessment, deep breathing

Monitor heart rate - (b/c of increase in K+)

Safety - changes in LoC, skin assessment, PI and falls risk

Consider underlying cause: over-sedation, pulmonary oedema, aspiration

Possible Med admin - may need IV KCI (replace K moving out of cells due to acidosis), bronchodilators, sodium bicarb in emergency but be aware of rebound)

Nursing Interventions: Respiratory Alkalosis

• Respiratory rate and try to determine cause of hyperventilation - anxiety/pain

• Encourage slow deep breaths

• Assess of LoC and cognition changes

• risk of falls and safety

• may have associated hypokalemia so monitor for arrhythmias

Nursing Interventions: Metabolic Acidosis

• Monitor BP and for signs of hypovolemia, tissue perfusion

• Monitor for signs of hypoxia and changes in LoC

• safety related to falls and airway

• Monitor heart rate and rhythm

• Monitor I/O

• Test urine for acidity related to kidneys excreting Hydrogen ions

• Address underlying cause: DKA, liver and renal failure

• Monitor IVI

Nursing Interventions: Metabolic Alkalosis

Respiratory rate and depth - body trying to compensate for reducing resp rate

Assess LoC and cognition

Heart rate and rhythm

Address underlying cause - nausea, diarrhea

Nursing Intervention for People with Disrupted Acid-Base Balance

Ongoing assessment

Implement safety measures

Implement comfort measures

Support compensatory mechanisms

Implement collaborative interventions focused om:

• Treatment of the underlying cause

• Adjustment of the pH (controversial)

most (65%) of fluid is

intracellular fluid (ICF)

Dehydration vs Overhydration

Lose H2O = Concentrate Na+

• fever/sweating/diabetes

Lose H2O and electrolytes = Hypovolemia

• Vomiting / Diarrhea/ Gi Suction or drainage/blood loss

• Lose Na+ and K+

• Kidneys retain Na+ and excrete K+

Lose more Na+ than H2O = Hyponatremia

• diuretics

Renal failure

• K not excreted = hyperkalemia

Fluid Overload = dilution of electrolytes

• HF, liver failure, IV fluids

Why would you give a hypotonic solution (lower Na conc than plasma)?

To/For:

Replace fluid loss/ Maintenance fluids

Hypernatremia

Ketoacidosis

Why would you give an isotonic solution (same Na+ conc as plasma)?

Expand extracellular volume - deficit due to hemorrhage, dehydration, fluid loss

Why would you give a hypertonic solution (higher Na conc than plasma)?

Replace sodium - hyponatremia

Volume expanders

Cerebral edema

Signs of Fluid Imbalances

• skin turgor

• edema

• JVP

• changes in LoC - coma

• Fontanel (babies)

• hypo/hypertension

• convulsions (overhydration)

• increased thirst

• tachycardia/bradycardia

• urine output

• bloods - changes in electrolytes

Causes of Fluid Imbalances

Dehydration

• vomiting

• hemorrhage

• burns

• pleural effusion

• diabetes (increased urination)

• fever

• heat stroke

• diarrhea

• diuretics

• Addison’s disease

Overhydration/ Fluid Retention

• renal failure

• heart failure

• overloading IV therapy

• ascites

Dehydration Signs and Symptoms

• increased thirst (maybe??)

• decreased skin turgor

• dry mucous membranes

• hypotension

• decreased LoC

• coma

• decreased urine output

Nursing Priorities:

• Vitals and O2 sats

• Cardiac status

• Assess mental status

• Urine output

• Address fluid loss - fluids, IV

• Safety

• Inform physician

Fluid Overload Signs and Symptoms

• weight gain

• peripheral edema

• increased BP

• tachycardia

• SoB

• crackles lung base

• headaches

• confusion

• seizures

Nursing Priorities

• airway

• monitoring vitals and O2 sats

• review and check IV fluids

• safety

• notify physician/prescriber

• reassurance

Hyponatremia (<135mmMol/l)

Causes:

• water retention relative to sodium e.g. Renal failure

• Excessive water intake

• Medications: diuretics, antidepressants

• Cardiac, renal or liver failure

• Overproduction of ADH (anti-diuretic hormone)

• Severe and chronic vomiting and diarrhea

• Addison’s disease

• Recreational drugs - ecstasy

Risk factors/Populations:

• older people

• dementia

• people with heart failure, renal failure

• liver cirrhosis

• alcoholics

• hypertension - diuretics and renal failure

• recreational drug users

• distance athletes - marathons

• receiving IV therapy

Symptoms and impact:

• nausea

• headache

• confusion

• changes in LoC

• seizures

• coma

• death

Management

• fluid restriction, IVI saline

• address underlying cause

Hypernatremia ( >145mmMol/l)

Causes:

• Water loss relative to sodium e.g. overloading with hypertonic Na sol’n

• dehydration

• diabetes

• renal disease

• fever and infection

• severe burns

• parenteral and enteral feeds

Risk factors/populations

• older people

• dementia infants

• receiving IV therapy

• NG feeding

Symptoms

• thirst

• dry mucous membranes

• irritability and mood changes

• confusion

• lethargy

• tachycardia

• seizures

• coma

• death

Management

• fluids, addressing underlying causes

Hypokalemia (<3.5mmol/l)

Causes:

• medications - diuretics

• excessive alcohol use

• renal disease

• diabetic ketoacidosis

• diarrhea

• overuse of laxatives

• renal disease

• Folic acid deficiency

• primary aldosteronism (disorder of adrenal glands)

Risk factors/ populations:

• diuretics (most common)

• alcoholics

• food poisoning

• chronic nausea and vomiting

• C-diff

Symptoms

• muscle weakness

• muscle damage

• tingling

• cramps

• fatigue

• arrhythmias

• lightheaded

• polyuria

• polydipsia (thirst)

Management

• K supplements (oral/IV), cardiac monitoring)

Hyperkalemia (>5mmol/l)

Causes:

• renal failure

• adrenal insufficiency (Addison’s)

• diabetes

• chemotherapy

• major trauma

• Medications: beta blockers, ACE inhibitors

• K supplements

Risk factors / populations:

• trauma patients

• renal failure

• diabetics

• taking beta blockers, K-sparring diuretics

• Others: male, heart disease, stroke

Symptoms:

• muscle weakness

• fatigure

• heart palpitations

• arrhythmias

• numbness or paralysis

• nausea

• chest pains

Management:

• Calcium gluconate (reduces cardiac toxicity)

• dialysis (if available)

• insulin and glucose (encourages movement K into cell

• diuretics (furosemide)