webnur105 acid-base part i dd

8/8/2019 WebNUR105 Acid-Base Part I DD

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Elsevier items and derived items 2006 by Elsevier Inc.

Chapter 14 Part I

Acid-Base BalanceAcid-Base Balance


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Normal Blood pH

Changes from normal blood pH (7.35 to 7.45)interfere with many normal functions by:

Changing the shape of hormones and

enzymes so that they may no longer performtheir normal functions

Changing the distribution of other electrolytes,causing fluid and electrolyte imbalances

(Continued)

Changes from normal blood pH (7.35 to 7.45)interfere with many normal functions by:

Changing the shape of hormones and

enzymes so that they may no longer performtheir normal functions

Changing the distribution of other electrolytes,causing fluid and electrolyte imbalances

(Continued)


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Normal Blood pH (Continued)

Altering the responses of excitablemembranes

Decreasing the uptake, activity, and

effectiveness of many hormones and drugs

Altering the responses of excitablemembranes

Decreasing the uptake, activity, and

effectiveness of many hormones and drugs


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Introduction to Acid-Base Chemistry

Acids are substances that release hydrogenions when dissolved in water.

Bases- are substances that bind free hydrogen

when dissolved in water.

Buffers- can either release or bind hydrogen,example Hemoglobin.

Acids are substances that release hydrogenions when dissolved in water.

Bases- are substances that bind free hydrogen

when dissolved in water.

Buffers- can either release or bind hydrogen,example Hemoglobin.


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Introduction to Acid-Base Chemistry

Body fluid chemistry

Bicarbonate ions- the most common base inthe human body.

Carbonic acid is the most common acid.

Body maintains a ratio of 1:20 carbonic acidto bicarbonate level.

Body fluid chemistry

Bicarbonate ions- the most common base inthe human body.

Carbonic acid is the most common acid.

Body maintains a ratio of 1:20 carbonic acidto bicarbonate level.


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Sources of Acids

Glucose metabolism releases CO2

1 molecule of glucose releases 6 CO2

Fat and protein metabolism- releases sulfuricacid and ketoacids.

Incomplete metabolism of glucose and fats-release lactic acid and ketoacids.

Destruction of cells- releases acids from ICF.

Glucose metabolism releases CO2

1 molecule of glucose releases 6 CO2

Fat and protein metabolism- releases sulfuricacid and ketoacids.

Incomplete metabolism of glucose and fats-release lactic acid and ketoacids.

Destruction of cells- releases acids from ICF.


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Sources of Bicarbonate Ions

Bicarbonate is the primary buffer of the ECF.

Bicarbonate comes from the breakdown ofcarbonic acid, intestinal absorption of

ingested bicarb, pancreatic production ofbicarb, and kidney reabsorption of filteredbicarb.

Once bicarbonate is in the ECF, it is keptat a level 20 times greater than that ofcarbonic acid.

Bicarbonate is the primary buffer of the ECF.

Bicarbonate comes from the breakdown ofcarbonic acid, intestinal absorption of

ingested bicarb, pancreatic production ofbicarb, and kidney reabsorption of filteredbicarb.

Once bicarbonate is in the ECF, it is keptat a level 20 times greater than that ofcarbonic acid.


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Acid-Base Regulatory Mechanisms

Buffers first line of defense, very quick

Chemical buffers, acids and base

Protein buffers ICF Hemoglobin

ECF Albumin, Globulins

Buffers first line of defense, very quick

Chemical buffers, acids and base

Protein buffers ICF Hemoglobin

ECF Albumin, Globulins


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Respiratory Acid-Base Control Mechanisms

When chemical buffers alone cannot preventchanges in blood pH, the respiratory system isthe second line of defense against changes.

Hyperventilation chemoreceptors in thebrain detect increase of CO2 in the brain andincrease the rate and depth of breathing toexhale, or blow off, carbon dioxide.

Hypoventilation- brain decreases rate anddepth to retain carbon dioxide.

Very fast, responds within minutes

When chemical buffers alone cannot preventchanges in blood pH, the respiratory system isthe second line of defense against changes.

Hyperventilation chemoreceptors in thebrain detect increase of CO2 in the brain andincrease the rate and depth of breathing toexhale, or blow off, carbon dioxide.

Hypoventilation- brain decreases rate anddepth to retain carbon dioxide.

Very fast, responds within minutes


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Renal Acid-Base Control Mechanisms

The kidneys are the third line of defense againstwide changes in body fluid pH. Renal mechanism isvery strong, but takes 24 48 hours to respond.

Kidney movement of bicarbonate- reabsorbs

filtered bicarb, if hydrogen levels are low, thebicarb is not reabsorbed, and thus excreted.Kidneys can also produce additional bicarb.

Formation of acids- hydrogen binds to base toform acid.

Formation of ammonium- made from ammonia, acommon biproduct of protein metabolism,secreted in urine, adds H+, and excreted.

The kidneys are the third line of defense againstwide changes in body fluid pH. Renal mechanism isvery strong, but takes 24 48 hours to respond.

Kidney movement of bicarbonate- reabsorbs

filtered bicarb, if hydrogen levels are low, thebicarb is not reabsorbed, and thus excreted.Kidneys can also produce additional bicarb.

Formation of acids- hydrogen binds to base toform acid.

Formation of ammonium- made from ammonia, acommon biproduct of protein metabolism,secreted in urine, adds H+, and excreted.


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Compensation

The body attempts to correct changes in bloodpH.

pH < 6.9 or > 7.8 is usually fatal.

Respiratory system is sensitive to acid-basechanges; can begin compensation efforts withinseconds.

Renal compensatory mechanisms are muchmore powerful and result in rapid changes inECF composition, but take 24 48 hours.

The body attempts to correct changes in bloodpH.

pH < 6.9 or > 7.8 is usually fatal.

Respiratory system is sensitive to acid-basechanges; can begin compensation efforts withinseconds.

Renal compensatory mechanisms are muchmore powerful and result in rapid changes inECF composition, but take 24 48 hours.


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Respiratory Compensation

Lungs compensate for acid-base imbalances ofa metabolic origin.

Exampleprolonged running causes buildup of

lactic acid, hydrogen ion levels in the ECFincrease, pH drops; breathing is triggered inresponse to the increased carbon dioxide levelsto bring the pH level back to normal.

Lungs compensate for acid-base imbalances ofa metabolic origin.

Exampleprolonged running causes buildup of

lactic acid, hydrogen ion levels in the ECFincrease, pH drops; breathing is triggered inresponse to the increased carbon dioxide levelsto bring the pH level back to normal.


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Renal Compensation

A healthy kidney can correct or compensate forchanges in blood pH when the respiratorysystem is either overwhelmed or is not healthy.

(Continued)

A healthy kidney can correct or compensate forchanges in blood pH when the respiratorysystem is either overwhelmed or is not healthy.

(Continued)


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Renal Compensation (Continued)

Exampleperson has chronic obstructivepulmonary disease, retains carbon dioxide in theblood, blood pH level falls (becomes more

acidic); kidney excretes more hydrogen ions andincreases the reabsorption of bicarbonate backinto the blood.

Exampleperson has chronic obstructivepulmonary disease, retains carbon dioxide in theblood, blood pH level falls (becomes more

acidic); kidney excretes more hydrogen ions andincreases the reabsorption of bicarbonate backinto the blood.


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Age related changes in Acid-Base

Older adults are at greater risk for pHproblems because their lungs and kidneysare less able to respond to minor changes in

hydrogen ion production or elimination. May be on medications that hamper the

bodys ability to compensate, such asdiuretics.

Risk is even greater in clients withpulmonary, vascular, cardiac or kidneyproblems.

Older adults are at greater risk for pHproblems because their lungs and kidneysare less able to respond to minor changes in

hydrogen ion production or elimination. May be on medications that hamper the

bodys ability to compensate, such asdiuretics.

Risk is even greater in clients withpulmonary, vascular, cardiac or kidneyproblems.


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Assessment of Acid-Base Balance

History

Physical assessment

Diagnostic assessment

History

Physical assessment

Diagnostic assessment

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