Acid-Base Balance

Potential causes of respiratory alkalosis

*hyperventilation, mechanical ventilation, hypoxemia due to pulmonary disease, CHF Hyperventilation may be due to: anxiety, pulmonary embolism, fear

Respiratory alkalosis signs & symptoms

-Deep, rapid breathing -Hyperventilation -Lethargy and confusion -Tachycardia -Nausea, vomiting -Light headedness -Numbness and tingling of extremities -Hypokalemia might be present -Low or normal BP

Tx/management of metabolic alkalosis

-ID and tx underlying cause -Monitor intake and output -Restore fluid balance -IV sodium chloride solution (NS) -Administer potassium chloride (KCl) -Carbonic anhydrase inhibitors (e.g., acetaxolamide, aka Diamox) in patients with heart failure - the administration of this medication will allow for less fluids to be delivered to pts with heart failure (fluids could lead to fluid overload in these pts)

Respiratory acidosis signs & symptoms

-Rapid, shallow respirations -Decreased BP (b/c of vasodilation) -Drowsiness, dizziness, disorientation -Muscle weakness, hyperreflexia -Headache -Dyspnea -Hyperkalemia (due to high potassium) -Dysrhythmia (due to high potassium) -As hyperkalemia is often a co-morbidity, think of hyperkalemia symptoms with respiratory acidosis, as they can be seen in tandem

Respiratory alkalosis tx/management

-Relaxation techniques to slow breathing -Breathe into paper bag -Anti-anxiety meds (if anxiety) -Treat hypoxemia and hypermetabolic states -Administer IV chloride solutions

Metabolic alkalosis signs & symptoms

-Restlessness followed by lethargy -Confusion (decreased level of consciousness, dizzy, irritable) -Nausea, vomiting, diarrhea -Tremors, muscle cramps, tingling/parasthesias in fingers and toes -Compensatory hypoventilation -Dysrhythmias (tachycardia)

Tx/Management of Respiratory Acidosis

-Restore adequate ventilation -Positioning -Pulmonary hygiene -May need mechanical ventilation -Admin IV lactate solutions

Metabolic acidosis: signs and symptoms

-Warm, flushed skin (vasodilation) -Decreased BP (vasodilation) -Headache -Changes in LOC (e.g., confusion, drowsiness) -Kussmaul respirations (compensatory hyperventilation) -Muscle twitching -Nausea, vomiting, diarrhea -Hyperkalemia

ABG Analysis

1) Look at pH 2) Determine whether primary cause of imbalance is respiratory or metabolic by looking at CO2 and HCO3 -------> If CO2 is off, then it is respiratory (high - acidosis, low - alkalosis) --------> If HCO3 is off, then it is metabolic (high - alkalosis, low - acidosis) 3) Examine the O2 and SaO2 to determine if compensation is occurring

What are the primary regulatory mechanisms for acid-base balance in the body?

1. Buffer systems (carbonic acid-bicarbonate is primary buffer system) 2. Respiratory system 3. Renal system

Homeostatic bicarbonate-carbonic acid ratio

20:1 Much more bicarbonate

Normal Bicarbonate (HCO3) serum levels

22-26 mEq/L

Normal PaCO2 range (carbon dioxide blood levels)

35-42 mm HG

Normal blood pH range

7.35-7.45

A blood pH level of 7.20 would be ____________________ A blood pH level of 7.50 would be _____________________

A blood pH level BELOW 7.35 is acidosis (the blood is too acidic) A blood pH ABOVE 7.45 is alkalosis (the blood is too alkaline)

Mixed acidosis

Acidosis caused by multiple issues, each characteristic to different forms. For example, poor tissue perfusion resulting in lactic acidosis mixed with severe diarrhea from metabolic acidosis

A client overdosed on heroin and has a respiratory rate of 8 breaths/min and is unresponsive. Which arterial blood gas result does the nurse anticipate? A) pH: 7.49, PaCO2: 45 mmHg, HCO3: 33 mEq/L B) pH: 7.28, PaCO2: 60 mmHg, HCO3: 26 mEq/L C) pH: 7.31, PaCO2: 41 mmHg, HCO3: 18 mEq/L D) pH: 7.38, PCO2: 45 mmHg, HCO3: 26 mEq/L

B) pH: 7.28, PaCO2: 60 mmHg, HCO3: 26 mEq/L This result best represents what the client's ABG would be. Hypoventilation leads to retention of carbon dioxide and respiratory acidosis. ABG results of respiratory acidosis includes a decreased pH (normal range 7.35-7.45) and an increased PaCO2 (normal range 35-45 mmHg).

The nurse cares for a client with type I diabetes and a serum blood glucose of 400 mg/dL. Which set of arterial blood gases does the nurse expect to find? A) pH: 7.45, PaCO2: 38 mmHg, HCO3: 23 mEq/L B) pH: 7.29, PaCO2: 22 mmHg, HCO3: 14 mEq/L C) pH: 7.31, PaCO2: 67 mmHg, HCO3: 32 mEq/L D) pH: 7.39, PaCO2: 43 mmHg, HCO3: 22 mEq/L

B) pH: 7.29, PaCO2: 22 mmHg, HCO3: 14 mEq/L This ABG result best reflects metabolic acidosis found in DKA. A bicarbonate level of 14 mEq/L is very low (normal values are 21-28 mEq/L), indicating acidosis. Also, the pH of 7.29 (a normal range is 7.35-7.45) is reflective of acidosis. Additionally, the PaCO2 level of 22 mmHg is low (a normal range is 35-45 mmHg). This reflects the body's attempt to compensate the acid level in the blood. Though option C also represents a state of acidosis (pH of 7.31), the elevated PaCO2 demonstrates respiratory acidosis. DKA is a form of metabolic acidosis.

How can hypocalcemia be related to metabolic or respiratory alkalosis?

Brief: H+ ions decrease in blood. Usually H+ and Ca+ bind to albumin. W/less H+, more Ca+ binds to albumin, leaving less freely ionized Ca+ As blood plasma hydrogen ion concentration decreases, caused by respiratory or metabolic alkalosis, the concentration of freely ionized calcium, the biologically active component of blood calcium, decreases. Because a portion of both hydrogen ions and calcium are bound to serum albumin, when blood becomes alkalotic, the bound hydrogen ions dissociate from albumin, freeing up the albumin to bind with more calcium and thereby decreasing the freely ionized portion of total serum calcium. For every 0.1 increase in pH, ionized calcium decreases by about 0.05 mmol/L. This hypocalcemia related to alkalosis is partially responsible for the cerebral vasoconstriction that causes the lightheadedness, fainting, and paraesthesia often seen with hyperventilation.

The nurse reviews the arterial blood gas values for a client with bilateral pulmonary effusions. Which finding requires further intervention from the nurse? A) pH 7.36 B) PaCO2 40 mmHg C) PaCO2 55 mmHg D) PaO2 80 mmHg

C) PaCO2 55 mmHg This is falling outside of the normal range of 35-45 mmHg. This indicates impaired ventilation and requires attention from the nurse. All other values are within normal/expected ranges.

H2CO3

Carbonic acid Weak acid crucial in the balance of blood pH Is at a 1:20 ratio with bicarbonate In lungs, carbonic acid is reduced

The nurse cares for a client with sepsis who has an elevated serum lactate level. Which acid-base imbalance does the nurse expect? A) Respiratory acidosis B) Respiratory alkalosis C) Metabolic alkalosis D) Metabolic acidosis

D) Metabolic acidosis Elevated serum lactate results from anaerobic metabolism as a result of inadequate perfusion and decreased oxygen delivery to the tissues. This elevation of lactate leads to lactic acidosis, a metabolic acidosis.

The nurse cares for a client with severe pain and a respiratory rate of 32 breaths/min. Which acid-base imbalance does the nurse expect to find with sustained tachypnea? A) Respiratory acidosis B) Metabolic acidosis C) Metabolic alkalosis D) Respiratory alkalosis

D) Respiratory alkalosis A prolonged respiratory rate may lead to respiratory alkalosis (blood pH >7.35 and PaCO2 <35 mmHg). This occurs because the client "blows off" PaCO2, creating the acid-base imbalance.

Potential causes of metabolic acidosis

Diabetic ketoacidosis (DKA) Severe diarrhea Renal failure Shock

Other than the bicarbonate-carbonic acid buffer system, what are some other systems?

ECF: inorganic phosphate, plasma protein ICF: proteins, inorganic/organic phosphates, hemoglobin (in red blood cells) *Protein buffering - proteins have negative charges so they can act as buffers with the positive hydrogen ions These other systems are small

Respiratory alkalosis (overview)

High blood pH (greater than 7.45) Low CO2/PaCO2 (lower than 35 mm HG) Occurs with hyperventilation Compensation: kidneys decrease H+ excretion and bicarbonate resorption

pH

Hydrogen ion concentration The more hydrogen ions, the more acidic (so, the lower the pH)

Which condition (electrolyte imbalance) is very often seen with acidosis?

Hyperkalemia Potassium levels increase in acidosis Hyperkalemia is often seen in the presence of acidosis

Hyperventilation is a/n __________ in respiratory rate, which causes a/n ___________ in PaCO2

Hyperventilation is an increase in respiratory rate, which causes a decrease in PaCO2 Essentially, you're "blowing off" CO2 when you breathe. So, if you are breathing more, you are losing more CO2

A patient has both hypocalcemia and chronic metabolic acidosis. Which should be addressed first?

Hypocalcemia should be treated first - so Ca+ does not drop further when metabolic acidosis is treated. Because, in acidosis, there are too many H+ ions. In treatment, we will attempt to reduce the amount of H+ ions. But, when we do this, we will also be decreasing the amount of H+ ions that can bond with albumin. By doing this, more Ca+ will bond with albumin, decreasing the calcium blood concentration even further

What is the primary cause of respiratory acidosis?

Hypoventilation Could be caused by drug overdose, COPD, airway obstruction, decreased respiration due to anesthesia, etc.

Metabolic acidosis tx/management

ID and treat underlying cause/s Administer bicarbonate IV solutions containing lactate (forms bicarbonate in liver) Monitor K+ closely Treat hypocalcemia in chronic metabolic acidosis Dialysis

Metabolic alkalosis

Increased pH > 7.45 Increased bicarbonate HCO3 > 26 Increased bicarbonate concentration, usually from excessive loss of metabolic acids Compensation: hypoventilation and kidneys conserve H+ and eliminate bicarbonate

Which IV solution might be specifically helpful in the treatments of respiratory acidosis and metabolic acidosis?

Lactated ringer Lactate is converted to bicarbonate by the liver; the increase in bicarbonate (a base) will help restore pH balance in the blood We do NOT use this in lactic acidosis, though.

Metabolic acidosis

Low pH (below 7.35) Low HCO3 (lower than 22) Increase in noncarbonic acids, loss of bicarbonate (HCO3) from ECF, or bicarbonate cannot be regenerated by the kidney Compensation: hyperventilation and renal excretion of excess acid (latter will not occur in impaired kidney and the inability will contribute to metabolic acidosis)

Respiratory system in acid-base balance

Lungs excrete CO2 and water. The amount of CO2 in the blood directly relates to carbonic acid concentration (acidity). As respirations increase, more CO2 is expelled and less remains in the blood (less carbonic acid and H+ so pH goes up). As respirations decrease, more CO2 remains in the blood (more carbonic acid and H+ so pH goes down). The rate of respirations is controlled in the medulla in the brainstem which senses the amount of CO2 in the bloodstream and increases/decreases rate of respirations to try to balance. If the respiratory system is the cause of an imbalance, the respiratory system can not correct the pH. The respiratory system can also act as a compensatory mechanism to change respiration rates to blow off or retain CO2.

methylenedioxymethamphetamine (MDMA) is associated with which acid-base and electrolyte imbalance?

MDMA is associated with metabolic acidosis. Acidosis causes potassium to move from the cells to the extracellular fluid (plasma) in exchange for hydrogen ions, causing an increase in K+ ions, or hyperkalemia

What is the primary acid-base disturbance in metabolic acidosis? What about in metabolic alkalosis?

Metabolic acidosis - pH decreases because HCO3 (bicarbonate) decreases Metabolic alkalosis - pH increases because bicarbonate increases

What is the primary acid-base disturbance in respiratory acidosis? What about in respiratory alkalosis?

Metabolic acidosis - pH decreases because HCO3 (bicarbonate) decreases Metabolic alkalosis - pH increases because bicarbonate increases

________ ______________ may occur with prolonged gastric suctioning and removal of gastric secretions

Metabolic alkalosis; this is due to a decrease in hydrogen and the subsequent, continued alkaline state In lab values, this would likely present as: Elevated pH (alkaline state) Elevated HCO3 (increased bicarbonate level, showing alkalosis) PaCO2 would likely be within normal limits - unless there was compensation via respiration occurring

A nurse assesses a client with hyperaldosteronism and subsequent acid-base imbalance. Which client statement does the nurse expect? A) "My heart beat feels slow and weak" B) "I can't seem to catch my breath" C) "My mouth and toes feel tingly" D) "I have swelling in my feet"

Parathesias around the mouth and on the toes are a hallmark symptom of alkalosis. This would be an expected finding in an uncompensated metabolic alkalosis that would be caused by hyperaldosteronism.

What is the primary acid-base disturbance in respiratory acidosis? What about in respiratory alkalosis?

Respiratory acidosis - pH lowers because CO2 increases Respiratory alkalosis - pH increases because CO2 decreases

A client's arterial blood gas results reveal a serum pH of 7.49, a PaCO2 of 41 mmHg, and a HCO3 level of 38 mEq/L. How does the nurse interpret these results? A) Uncompensated metabolic alkalosis B) Compensated metabolic alkalosis C) Uncompensated respiratory alkalosis D) Compensated respiratory acidosis

Uncompensated metabolic alkalosis Uncompensated metabolic alkalosis is correct because there is an increase in pH (alkalosis), an increase in HCO3 (metabolic in origin), but the PaCO2 is still normal (this shows the lungs are not yet compensating by retaining PaC02 via hypoventilation).

Mixed alkalosis

a pathologic condition in which there is an elevated pH, a low PaCO2 level, and an elevated bicarbonate level, which occurs when there is both a respiratory and metabolic cause present at the same time

Parasthesias

an abnormal sensation, typically tingling or pricking ("pins and needles") ****Parasthesias are strongly related to alkalosis May indicate central nervous system excitation, which has the potential to make a pt who experiences them a higher priority (e.g., could be the preface to a seizure)

ABG

arterial blood gas analysis of the gases in the blood; used to determine the effectiveness of the lungs in exchanging gases pH: 7.35-7.45 PCO2: 35-45 mm Hg HCO3: 22-26 mEq/L PO2: 80-100 mm Hg O2 Saturation: >94% Base excess/deficit: +/- mEq/L

Acetazolamide (Diamox)

carbonic anhydrase inhibitor Prevents bicarbonate uptake in the kidneys Inhibits the function of carbonic anhydrase, which breaks down bicarbonate Pts will urinate bicarbonate

carbonic acid-bicarbonate buffer system

chemical system that helps maintain pH homeostasis of the blood *Primary regulator of acid-base balance; aims for bicarbonate-carbonic acid ratio of 20:1 Operates in lungs and kidneys ----->Lungs decrease carbonic acid ----->Kidneys reabsorb or regenerate bicarbonate but do not act as fast

Respiratory acidosis

low pH, high CO2 Blood pH lower than 7.35 PaCO2 greater than 42 mm HG Occurs due to hypoventilation* Compensation: kidneys conserve bicarbonate and excrete H+ in the urine; begins to occur within first 24 hours but takes a lot of time