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Let’s review. Regulation of Acid-Base Balance. Buffering systems neutralize acids & bases & include lungs & renals Buffer— substance or a group of substances that can absorb or release H+ to correct an acid-base imbalance Arterial pH indirect measurement of H+ ion.

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regulation of acid base balance
Regulation of Acid-Base Balance
  • Buffering systems neutralize acids & bases & include lungs & renals
  • Buffer—substance or a group of substances that can absorb or release H+ to correct an acid-base imbalance
  • Arterial pH indirect measurement of H+ ion
regulation of acid base balance1
Regulation of Acid-Base Balance
  • pH reflection of balance between CO2 (lungs) & HCO3- (renal)
  • Acidosis
    • Increased amount of H+ ions
    • Normal pH 7.35-7.45
    • pH = 7 is neutral
    • pH < 7 is acid
    • pH > 7 is alkaline
regulation of acid base balance2
Regulation of Acid-Base Balance
  • AB balance exists when the rate at which the body produces acid or bases = the rate at which the acids or bases are excreted
  • Normal hydrogen ion level is necessary to maintain cell membrane integrity & speed of cellular enzymatic actions
acid base regulators
Acid-Base Regulators
  • Chemical regulation
    • Largest chemical buffer in ECF is carbonic acid/bicarb buffer system
    • First buffer system to react
    • Reacts in seconds
    • Lungs control excretion of carbon dioxide
acid base regulators1
Acid-Base Regulators
  • Kidneys control excretion of hydrogen & bicarbonate ions
  • ECF becomes more acidic pH decreases
  • ECF receives more base substances, pH rises
acid base regulators2
Acid-Base Regulators
  • Biological Regulation
    • Occurs after chemical buffering
    • Occurs hydrogen ions are absorbed or released by cells
    • Hydrogen ion + charged & must be exchanged with another + charged ion—frequently K+
  • Conditions that produce excess acidH+ ion enter cellpotassium ion leaves cellenters ECFelevated K+ levels
acid base regulators3
Acid-Base Regulators
  • Biological buffer
    • Hemoglobin-oxyhemoglobin system
    • CO2 diffuses to RBCforms carbonic aciddissociates to H+ & HCO3+ ionsH+ ions attach to hemoglobinHCO3+ available for buffering
  • Chloride shift in RBCs
    • Bld oxygenated in lungs, bicarb diffuses into cellchloride travels from hemoglobin to plasma to maintain electrical neutrality
acid base regulators4
Acid-Base Regulators

Metabolic acidosisresp increasegreater amt CO2 exhaleddecreased acidic level

  • Physiological regulation
    • Lungs & kidneys
    • If diseased is no longer effective for regulation
    • Lungs adapt rapidly to imbalance
    • Increased H+ & CO2 ions stimulate respiration
acid base regulators5
Acid-Base Regulators
  • Physiological Regulation
    • Kidneys take a few hrs to several days to regulate acid-base balance
    • Inc or dec HCO3+ production
    • Certain amino acids in renal tubules change to ammonia NH3- & excreted by kidneys
acid base balance
Acid-Base Balance
  • Acid-base balance is regulated by the body’s ability to maintain arterial pH 7.35-7.45
  • Checked by ABGs
  • Deviation from normal value indicates experiencing an acid-base imbalance
breakdown of abgs
Breakdown of ABGs
  • pH
    • Measures H+ ions concentration in body fluids
    • Slight change can be life threatening
    • Acidic—increase in H+ ions
    • Alkaline—decrease in H+ ions
slide37
ABGs
  • PaCO2
    • Partial pressure of carbon dioxide in arterial bld
    • Reflection of depth of pulmonary ventilation
    • Normal 35-45 mm Hg
    • **Hyperventilation PaCO2 < 35 mm Hg
    • Carbon dioxide is exhaled & amt dec
slide38
ABGs
  • **hypoventilation
    • PaCO2 is > 45 mm Hg
    • Less carbon dioxide is exhaled
    • Increasing concentration of carbon dioxide
slide39
ABGs
  • PaO2
    • Parital pressure of O2 in arterial bld
    • Normal 80-100 mm Hg
    • N0 primary role in A-B regulation when normall
    • PaO2 < 60 causes anaerobic metabolism—produces lactic acid—metabolic acidosis
slide40
ABGs
  • Oxygen Saturation
    • When hemoglobin is saturated with O2
    • Normall 95-99%
    • Changes in temp,PaCO2 & pH affect oxygen
slide41
ABGs
  • Base Excess
    • Amt of blood buffer
    • Normal +/- 2 mEq/L
    • High value—alkalosis
      • Citrate excess from rapid blood transfusions
      • IV HCO3 infusion DKA\
      • Ingestion large amt bicarb solutions (antacids)
slide42
ABGs
  • Base excess
    • Low value—acidosis
      • Lg amts of bicarb ion excretion
      • ie: diarrhea
slide43
ABGs
  • Bicarbonate
    • Major renal component
    • Kidneys excrete & retain to maintain normal balance
    • Principal buffer ECF
    • Normal 22-26 mEq/L
    • Metabolic acidosis < 22 mEq/L
    • Metabolic alkalosis > 26 mEq/L
acid base imbalances
Acid-Base Imbalances
  • Either respiratory or metabolic, depend on their underlying cause
  • Corrects AB imbalances through process known as compensation
respiratory acidosis
Respiratory Acidosis
  • pH < 7.35
  • PaCO2 >45 mm Hg
  • PaO2 < 80 mm Hg
  • Bicarb level normal if uncompensated
  • Bicarb level > 26 mEq/L if compensated
  • HypoventilationCSF & brain cells become acidicneurological changes hypoxemiafurther neurological impairment
  • Hyperkalemia & hypercalcemia can occur
  • Kidneys hold to bicarb & release hydrogen ions UA—may take 24 hrs
respiratory acidosis causes
Respiratory Acidosis Causes
  • Hypoventilation resulting primary respiratory problems
    • Chest wall injury
    • Respiratory failure
    • Cystic fibrosis
    • Pneumonia
    • Atelectasis (obstruction of small airways often caused by mucus)
  • Hypoventilation resulting from factors other than resp system
    • Obesity
    • Head injury
    • Drug overdose (OD) with resp depressant
    • Paralysis of resp muscles caused by neurological alterations
respiratory acidosis1
Respiratory Acidosis
  • S/S
    • Convulsion
    • Coma
    • Muscular twitching
    • Confusion
    • Dizziness
    • Lethargy
    • HA
    • Warm flushed skin
    • Ventricular dysrhythmia
respiratory alkalosis
Respiratory Alkalosis
  • pH >7.45
  • PaCO2 <35 mm Hg
  • PaO2 normal
  • HCO3 nl if short-lived or uncompensated
  • HCO3 <22 mm Hg if compensated
  • Begins outside resp system ie: anxiety, panic attack OR within resp system ie: initial phase of asthma attack
  • Body does not usually compensate because pH returns to nl before kidneys can respond
respiratory alkalosis1
Respiratory Alkalosis
  • Causes
    • Salicylate overdoes
    • Anxiety
    • Hypermetabolic states ie: fever, exercise
    • CNS disorders ie: head injury, infections
    • Asthma
    • Pneumonia
    • Inappropriate vent settings
  • S/S
    • Confusion
    • Dizziness
    • Convulsions
    • Coma
    • Tachypnea
    • Numbness/tingling of extremities
    • dysrhythmias
metabolic acidosis
Metabolic Acidosis
  • High acid content of bld
  • Loss of HCO3
  • pH <7.35
  • PaCO2 normal if uncompensated
  • <35 mm Hg if compensated
  • PaO2 normal or increased
  • HCO3 < 22 mEq/L
  • O2 Sat normal
metabolic alkalosis
Metabolic Alkalosis
  • pH >7.45
  • PaCO2 normal if uncompensated
  • PaCO2 >45 mm Hg if compensated (occurs by decreasing RR & no renal disease)
  • PaO2 normal
  • HCO3 > 26 mEq/L
  • Causes
    • Excessive vomiting
    • Prolong gastric sx
    • Excess aldosterone
    • Hypokalemia
    • Hypercalcemia
    • Use of drugs ie: steriods, diuretics, sodium bicarb
question
Question
  • Interpret the following ABGs:
    • pH ?
    • PCO2 ? mm Hg
    • PO2 ? mm Hg
    • HCO3 ? mEq/L
    • O2 Sat ? %
slide57
Normal blood gas in an artery for humans:

pH 7.35–7.45

PaCO2 35–45 mmHg

PaO2 80–100 mmHg

HCO3− 22–26 mmol/L

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