ACID BASE BALANCE ( METABOLIC)

METABOLIC ACIDOSIS

  • A relative increase in the H+ concentrations occurs as a result of losing huge amount of bases and holding too much acid
  • PH is decreased; PCO2normal; PO2normal; HCO3 decreased

Cause:

  • Diabetes mellitus / diabetic ketoacidosis- an insufficient supply of insulin cause increased fat metabolism, leading to an excess accumulation of ketones or other acids.

  • Renal insufficiency or failure – increase waste product of protein metabolism is retained.
  • Inability of kidney to produce HCO3.
  • Insufficient metabolism of carbohydrate- when an insufficient supply of O2 is available for proper burning of carbohydrate into glucose and water; instead of O2, lactic acid is produced .it result acidosis.
  • Excessive ingestion of acetylsalicylic acid, eg aspirin can cause increase H+ concentration.
  • Severe diarrhea- intestinal and pancreatic secretion is normally alkaline therefore excessive loss of base leads to acidosis.
  • Malnutrition – improper metabolism of nutrients cause fat catabolism leading to the excessive build up of ketones and acids.
  • High fat diet- a high intake of fat leading to excessive production of ketones and acids.

Signs and symptoms



  • In an attempt to blow of the extra CO2 and compensate for the acidosis hyperpnoea with kussmaual’s respiration occurs
  • Head ache
  • Nausea, vomiting, diarrhea.
  • Fruity smelling breath as a result of fat metabolism
  • N.S depression
  • Mental dullness
  • Drowsiness
  • Stupor, coma
  • Twitching, convulsion ,
  • Hyperkalemia

Management

  • Access the level of consciousness and CNS depression.
  • Monitor I/O chart
  • Replace fluid and electrolytes
  • Prepare to administer I.V solution such as N.S, 5% D, ½ NS or bicarbonate to increase buffer base.
  • Initiate safety and seizure precaution
  • Monitor serum potassium level closely because when acidosis is treated potassium will move back into the cell and serum potassium will be dropped.
  • Treatment of DM and diabetic acidosis properly to prevent formation of ketones.
  • Treatment of renal failure and do dialysis to remove protein and waste products thereby lesser acidosis

METABOLIC ALKALOSIS

  • An increase of Hco3 and a decrease in H+ concentration result of an accumulation of base
  • Ph increases, Pco2 normal, Po2 normal, Hco3 increases

Causes

  • Ingestion of excess Hco3
  • Excessive vomiting or gastrointestinal suctioning lead to an excessive loss of acid
  • Diuretics- the loss of H+ and chloride causes a compensatory increase in the Hco3 in the blood
  • Hyperaldosteronism- increase renal tubular reabsorption of Na occurs, causes loss of H+ ions.
  • Massive transfusion of whole blood- the citrate, anticoagulant use for the storage of blood is metabolized to bicarbonate

Signs and symptoms

  • In an attempt to compensate respiratory rate and depth, rate go down to conserve Co2
  • Nausea, vomiting, diarrhea
  • Restlessness
  • Numbness and tingling in extremities
  • Twitching in the extremities
  • Hypokalemia, hypocalcemia
  • Tachycardia
  • Dysrhythmias

Management

  • Monitor potassium and calcium level in the blood
  • Institute safety precautions
  • Administer medication to promote kidney excretion of bicarbonate
  • Replace potassium if necessary

ARTERIAL BLOOD GASES

Normal ABG values

  • Ph 35 to 7.45
  • Pco2 35 to 45 mmHg
  • Po2 80 to 100 mmHg
  • Hco3 22 to 27 mEq/L
  • O2 concentration 95 to 100%

Nursing responsibility




  • Obtain vital signs.
  • Determine whether the client has an arterial line in place.
  • Perform the Allen test to determine the presence of collateral circulation.
  • Assess the factor that may affect the accuracy of ABG result. such as, Change in oxygen settings, Suction in last 20 minute, client activity.
  • Provide emotional support to patient
  • Draw the specimen by a heparinized syringe.
  • Apply pressure immediately to the puncture site following the blood draw.
  • Maintain pressure for 5 minutes or for 10 minutes if the client is taking anticoagulants.
  • Appropriately label the specimen and transport it on ice to the laboratory.

Allen test

  • Apply direct pressure over the client’s ulnar and radial arteries simultaneously.
  • While pressure is applied ask the client to open and close the hand repeatedly, the hand should be blanched.
  • Release pressure from the ulnar artery while compressing the radial artery.
  • Assess the color of the extremity distal to the pressure point.
  • If pinkness fails to return within 6 seconds, the ulnar artery is in sufficient, indicating that the radial artery should not be used for obtaining blood specimen.

ANALYZING ABG RESULTS

Pyramid points

  • In acidosis the Ph is down.
  • In alkalosis Ph is up.
  • The respiratory function indicator is the Pco2.
  • The metabolic function indicator is the Hco3.

Pyramid step 1

  • Look at the blood gas report; look at the Ph is it up or down.
  • If it is up it reflects alkalosis.
  • If it is down it reflects acidosis.

Pyramid step 2

  • Look at the Pco2 is it is up or down.
  • If it reflects an opposite response to the Ph then you know that it is respiratory imbalance.
  • If it is not reflect an opposite response to the Ph then move on to pyramid step 3

Pyramid step 3

  • Look at Hco3.
  • If Hco3 reflect a corresponding response with Ph, it is a metabolic imbalance.

Pyramid step 4

  • Compensation has occurred, if the Ph is in a normal range of 7.35 to 7.45, if Ph is not within the normal range look at the respirator or metabolic function indicator.

Respiratory imbalance

  • If it is respiratory imbalance look at the Hco3 to determine the state of compensation.
  • if the Hco3 is normal; then condition is uncompensated.
  • If it is in abnormal then the condition is Partial compensation.

Metabolic imbalance

  • If it is in metabolic imbalance look at the Pco2.
  • If the Pco2 is normal then condition is uncompensated.
  • If the Pco2 is abnormal then the condition is partial compensation.

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