ABGs,. CVADs. Zoya. . Minasyan. , RN, MSN-. Edu. Purpose. Maintain a balance between acids and bases to achieve homeostasis: State of equilibrium. Health problems lead to imbalance. Diabetes mellitus. ID: 710110
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Fluid, electrolyte, and acid-base imbalances; ABGs, CVADs
, RN, MSN-
PurposeMaintain a balance between acids and bases to achieve homeostasis: State of equilibriumHealth problems lead to imbalance
Vomiting and diarrhea
pHMeasure of H
Blood is slightly alkaline at pH 7.35 to 7.45.
<7.35 is acidosis.
>7.45 is alkalosis.Slide4
Range of pH
normal range of plasma pH is 7.35 to 7.45. A normal pH is maintained by a ratio of 1 part
carbonic acid to 20 parts bicarbonate.Slide5
Regulators of Acid/BaseMetabolic processes produce acids that must be neutralized and excreted.
Regulators of Acid/BaseBuffers: Act chemically to neutralize acids or change strong acids to weak acids
Cannot maintain pH without adequate respiratory and renal function
The buffers in the body include
intracellular and plasma protein
Regulators of Acid/BaseRespiratory system:
Respiratory center in medulla
Responds within minutes/hours to changes in acid/base.
Increased respirations lead to
Regulators of Acid/Base
When released into circulation, CO
enters RBCs and combines with H
O to form H
This carbonic acid dissociates into
hydrogen ions and bicarbonate
The free hydrogen is
molecules, and the bicarbonate diffuses into the
In the pulmonary capillaries, this process is reversed, and CO
is formed and excreted by the lungs.
As a compensatory mechanism, the respiratory system acts on the CO
O side of the reaction by altering the rate and depth of breathing to
hyperventilation) or “retain
If a respiratory problem is the cause of an acid-base imbalance (e.g., respiratory failure), the respiratory system loses its ability to correct a pH alteration.Slide9
Regulators of Acid/BaseRenal system:
and reabsorbs HCO
Reabsorption and secretion of electrolytes (e.g., Na
Responds within hours to daysSlide10
Regulators of Acid/Base
The three mechanisms of acid elimination are
secretion of small amounts of free hydrogen into the renal tubule,
combination of H
with ammonia (NH
) to form ammonium (NH
excretion of weak acids.
The body depends on the kidneys to excrete a portion of the acid produced by cellular metabolism.
Thus the kidneys normally excrete acidic urine (average pH equals 6).
As a compensatory mechanism, the pH of the urine can decrease to 4 and increase to 8.Slide11
Alterations in Acid-Base BalanceImbalances occur when compensatory mechanisms fail.
Classification of imbalances
Affect carbonic acid concentration
Respiratory AcidosisCarbonic acid excess caused by
Kidneys conserve HCO
and secrete H
Respiratory AcidosisHypoventilation results in a buildup of CO
carbonic acid accumulates in the blood
Carbonic acid dissociates, liberating H
, and a decrease in pH occurs.
is not eliminated from the blood, acidosis results from the accumulation of carbonic acid.
In acute respiratory acidosis, the renal compensatory mechanisms begin to operate within 24 hours.Slide14
Respiratory AlkalosisCarbonic acid deficit caused by
Hypoxemia from acute pulmonary disordersSlide15
Base bicarbonate deficit caused by
Lactic acid accumulation (shock)
Metabolic acidosis (base bicarbonate deficit) occurs when an acid other than carbonic acid accumulates in the body, or when bicarbonate is lost from body fluids.
excretion by lungs
respirations (deep and rapid)
Kidneys excrete acidSlide16
Metabolic AlkalosisBase bicarbonate excess caused by
Prolonged vomiting or gastric suction
Gain of HCO
Decreased respiratory rate to increase plasma CO
Renal excretion of HCO
Blood Gas ValuesArterial blood gas (ABG) values provide information about
Underlying cause of imbalance
Body’s ability to regulate pH
Overall oxygen statusSlide18
Interpretation of ABGsDiagnosis in six steps:
Determine if CO
matches the alteration.
Decide if the body is attempting to compensate.Slide19
Normal Blood Gas ValuesSlide20
Sample ABG InterpretationSlide21
Interpretation of ABGs
38 mm Hg
70 mm Hg
What is this?
Interpretation of ABGs
35 mm Hg
75 mm Hg
What is this?
A patient with an acid-base imbalance has an altered
potassium level. The nurse recognizes that the potassium
level is altered because:
1. Potassium is returned to extracellular fluid when metabolic acidosis is corrected.
causes an alkalosis that results in potassium being shifted into the cells.
3. Acidosis causes hydrogen ions in the blood to be exchanged for potassium from the cells.
4. In alkalosis, potassium is shifted into extracellular fluid to bind excessive bicarbonate.
AnswerAnswer: 3Rationale: Changes in pH (hydrogen ion concentration) will affect potassium balance.
hydrogen ions accumulate in the intracellular fluid (ICF),
and potassium shifts out of the cell to the extracellular fluid to maintain a balance of
across the cell membrane.
ICF levels of hydrogen diminish,
and potassium shifts into the cell.
If a deficit of H
occurs in the extracellular fluid, potassium will shift into the cell.
Acidosis is associated with
Alkalosis is associated with
Fluid volume deficitCan occur withAbnormal loss of body fluids-Diarrhea, hemorrhage, polyuria
Inadequate fluid intake
Shift of fluid from plasma into interstitial space
Correct the underlining cause
Replace the fluid and electrolyte (LR or NS isotonic solutions)Slide27
Fluid volume excessMay result from excessive intake of fluid
Abnormal retention of fluids(heart failure, renal failure)
Shift of fluid from interstitial fluid into plasma fluid
ID primary cause
Diuretics and fluid restriction
Restriction of Na intake
Fluid excess may result to
or pleural effusion, and
may be necessary.Slide28
Commonly prescribed crystalloid solutionsDextrose in water
Dextrose in Saline
5% in 0.225% isotonic
5% in 0.45% hypertonic
5% in 0.9% hypertonic
Multiple Electrolyte Solutions
Ringer’s solution- isotonic, includes CL, Na, K, Ca
Lactated Ringer’s solution- isotonic-Na, K,
, Ca, and lactate(the precursor of bicarbonate)Slide29
CVADs (central venous access
Catheters placed in large blood vessels of people who require frequent access to the vascular system
vein, jugular vein
Three different methods
Centrally inserted catheter(by MD)
Peripherally inserted central catheter
Implanted ports( by MD)Slide30
Permit frequent, continuous, rapid, or intermittent administration or monitoring
Indicated for patients with limited peripheral vascular access or need for long-term vascular accessSlide31
Centrally Inserted Catheter
Inserted into a vein in the neck, chest, or groin with tip resting in the distal end of the superior vena cava
Single, double, triple, or quad lumen
Nontunneled or tunneledSlide32
Central .Venous CatheterSlide33
Copyright © 2011, 2007, 2004, 2000, 1996, 1992, 1987, 1983 by Mosby, Inc., an affiliate of Elsevier Inc.PICC
Central venous catheters inserted into a vein in the arm
Single or multilumen, nontunneled
For patients who need vascular access for 1 week to 6 months
Complications include catheter occlusion and phlebitis.Slide34
Implanted Infusion Ports
Central venous catheter connected to an implanted, single or double subcutaneous injection port
Port is metal sheath with self-sealing silicone septum
Implanted Infusion PortSlide37
Implanted Infusion Port
Port accessed with special Huber-point needle
Good for long-term therapy
Low risk of infection
Care requires regular flushing.
Complication: (table 17-21 page 330)
occlusion(kinked, precipitate build up)
Embolism( dislodgment of thrombus, air entry,
Inspect catheter and insertion site.
Change dressing and clean according to institution policies.
Change injection caps.
Flushing is important.
Catheter and insertion site assessments include inspection of the site for redness, edema, warmth, drainage, and tenderness or pain. Observation of the catheter for misplacement or slippage is important.
Transparent dressing or gauze may be used.
cleaning techniques with
-iodine, and isopropyl
Teach the patient to turn the head to the opposite side of the CVAD insertion site during cap change.
Flushing: Use a normal saline solution in a syringe that has a barrel capacity of 10
or more to avoid excess pressure on the catheter. If resistance is felt, force should not be applied.Slide39
Should be done according to policy and procedures.
Ensure that catheter tip is intact.
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