Acid Base Balance 1- Week 2

Question 1

Normal values of Hb and Hematocrit

Answer 1

Hb- 13-18 gm/100ml

Hemotocrit 37-49%

Question 2

Normal range of Na, K+ and Cl-

Answer 2

Na+ 135–145 mM
[K+] 3.4–4.8 mM
[Cl–] 100–108 mM

Question 3

Normal range of HCO3-, pH, Arterial pCO2 and PO2

Answer 3

[HCO3–] 22–26 mM
pH 7.37–7.43
Arterial PCO2 35–45 mm Hg
Arterial PO2 80–100 mm Hg

Question 4

What are the ranges of H+ concentration that are compatiable with life

Answer 4

Range of [H+] compatible with life is about 20 to 160 nmol/L (pH 6.8 to 7.7).
• Plasma is normally about 40 nmol/L (pH 7.4)
• Intracellular fluid [H+] is about 100 nmol/L (pH 7.0)

Question 5

What are the two main categories of Acids

Answer 5

1. cArbonic acids- 24000 mmol of CO2 made per day
2. Non carbonic- 50-100mmol/day from sulfuric and phosphoric acid frommetabolism of proteins and lipids

** there are also acid metabolic intermediates but those don’t normaly acummulate– but you can get lactic acid in hypoxemia or ketones in diabetics or starvation**

Question 6

Primary defense to maintain H+? what happens secondary to this

Answer 6

The primary defense: excrete or metabolize acids and bases at the same rate as they are produced. Regulatory mechanisms react to the change in [H+] that results when input and
output don’t match.

Question 7

Give examples of when there would be an acid/base imbalance

Answer 7

• hypo (increase inPCO2) - or hyperventilation (decrease in PCO2) or abnormal pulmonary gas exchange .
• renal failure allows accumulation of non-carbonic acids (HNC) that are normally excreted in the urine.
• loss of fluids from the body that do not have the same acidity as the body.

Examples of fluid imbalances include
• losses from the GI tract
o loss of acid gastric juice in vomiting
o loss of alkaline intestinal contents during diarrhea.
• metabolic changes cause accumulation of abnormal acidic metabolic intermediates

Question 8

What is the value of acidosis? What are the two types and causes

Answer 8

Acidosis pH <7.37 H+ concentraiton of 160

1. Respiratory increase in PCO2
2. Metabolic- increae in Non carbonic acid or decrease in base

Question 9

What is the value of alkalosis? What are the two types and causes

Answer 9

pH > 7.43 (H+ concentration of less than 20)

1. Respiratory- hyperventiliation decrease in PCO2
2. Metabolic- decrease in HNC or an increase in bases

Question 10

Two methods of correcting changes in pH

Answer 10

1. buffering: chemical reactions which bind or release H+– temporary fix that prevents excess changes, but can be used up (once all the buffers bind to H+) and need to be restored.
2. compensation=CORRECTIVE: changes in the rate of excretion of CO2 (by lungs) and/or the excretion or production of
   HCO3– (by kidneys). Resotres pH and bufffer system capacity

Question 11

List the buffer systems in importance and the time span in which they work

Answer 11

1. Carbonic acid buffered- works extraceulluar- MINUTES
2. Hb- rapid ciruclation of blood makes it readily avliable- MINUTES
3. Intracellular proteins and phosphates- HOURS
4. Plasma protein- low molar concentriaon
5. Bone C032– very slow released in peridos of aciddosis- HOURS TO DAYs

Question 12

Explain how buffer system and compensatory would work when a person is hypoventilating

Answer 12

1. Hypoventilation woudl cause an increase in PCO2 pushing the bicarb reaction towards H+ and HCO3-
2. The H+ would bind to Hb as a buffer within minutes

This buffering would reduce the change in pH but leaves the body with less Hb so we need to compensate

3. The kidneys can make omre HCO3-
4. This woudl reveerse the binding to Hb and push the rxn back resoring pH, buffering capabilites and lost Hb-

Question 13

Explain the buffering and compensatory response to added HNC

Answer 13

1. The added NC acid is most rapidly neutralized (i.e., buffered) by the plasma HCO3– and plasma proteins. MIUTES
2. Part of the remaining free H+ reacts with interstitial fluid HCO3–. Equilibrium is reached in 15 min to ½ hour.
3. H+ enters cells and is buffered by intracellular (IC) NC buffers. Hb– reacts faster than other IC buffers, requires ~1/2 to 1 hour. Others need up to 6 hours.

Compensatory

1. CO2 generate by buffering is eliminated by lungs– hence acid doesn’t change PCO2
2. Respiratory compensation retains or blows of CO2. PCO2 changes during compensationbecause of the nervous system resets the PCO2 level. The process is half complete in 6
   hours; 95% in 12 hours.
3. Renal changes (increase or decrease in H+ secretion and making new bicarb) take days