export_acidsbases (1) Flashcards
What are the normal reference ranges for pH, PCO2, and PO2?
pH=7.35-7.45
PCO2=38-42 torr or mmhg
PO2=80-100 torr or mmhg
What are the major blood buffer systems in the body?
o Protein
o Phosphate buffer
o Hemoglobin
o Bicarbonate/Carbonic Acid
What are buffers? What are the best kind?
· Substance that minimizes changes in pH
· The best buffers are weak acids or bases because they do NOT dissociate readily
What is pKa? equation?
it is the logarithm of the acid dissociation constant.
pka= -logka
What is the Henderson–Hasselbalch equation?
pH=pKa+log[A-]/[HA]
It can be used for pH calculation of a solution containing pair of acid and conjugate base
A buffer has the best buffering capability when…
pH=pka
or
[A-]=[HA]
What is the pka of the carbonic acid/bicarbonate buffer?
6.1
If pH changes are due to primary PCO2 changes it is called…
Respiratory
If pH changes are due to primary HCO3- changes it is called….
metabolic
Total (ct) CO2 in body are:
HCO3-
CO2 (g)
CO2 (dissolved)(ca)
H2CO3(trace/constant)
What is the Boyles and Charles law?
PV=nRT
correlates the volume of an ideal gas to temperature and pressure
What is Daltons law?
total pressure of gas mixture equals the sum of the partial pressures of each gas in the mixture.
Total pressure=sum of partial pressures
How would you find the partial pressure of O2 (20.9%)
20.9/100X(760-47)
What is Henry’s law?
the concentration of a dissolved gas equals the partial pressure of that gas times its solubility constant (a)
CO2(d)~PCO2(a)
Equation for total CO2
Total CO2=HCO3- + PCO2(a)
What is hypercapnia? Ranges?
too much CO2 in the blood
>45 mmhg/torr
What is hypocapnia?
low levels of CO2 in the blood
<35 mmhg/torr
What is used to monitor O2 levels in the blood?
Pulse Oximetry
What is the Haldane effect?
O2 affects the affinity of Hb for CO2/H+
increased O2–>decreased CO2 affinity
What are the ranges for mild, moderate and severe hypoxemia?
Mild:60-80
Moderate:50-60
Severe: <40
Alkalosis is a decrease in..
PCO2
What is the Bohr effect?
Hb’s oxygen binding affinity is inversely related to acidity and CO2
Affinity of Hb for oxygen depends on:
- Temp
- pH
- PCO2
- 2-3DPG
- other hb species that are non-functional
A Shift to the left creates a _____ hb affinity for O2 and can be caused by:
Increased affinity.
Caused by:
- Increased pH
- Decreased-
- PCO2
- 2-3,DPG
- Temp
A Shift to the right _____ Hb affinity for O2 and caused by:
Decreased affinity for O2
Caused by:
- Deceased pH
- Increased-
- PCO2
- 2,3 DPG
- Temp
What is the normal ratio of HCO3-/PCO2?
20/1
What is primary compensation?
One parameter causing pH alteration
What is Partial compensation?
opposite parameter changing (outside reference range) but pH remains abnormal.
what is full compensation?
- pH is restored
- but parameters may or may not be within normal range
- Ratio is normal
What is overcompensation?
opposite acid base disturbance develops
What is “mixed” compensation?
Classification of an acid base disturbance when both metabolic and respiratory are contributing to the acid base disturbance and correction isn’t expected.
Respiratory Acidosis is due to?
Increased PCO2
Metabolic acidosis is due to
decrease in HCO3-
Respiratory Acidosis is due to
increase in PCO2
Metabolic Alkalosis is due to
increase in HCO3-
Respiratory Alkalosis is due to
decrease in PCO2
What is the primary protein buffer?
Albumin
How do protein buffers work?
pick up CO2 or H+
Carbamino
imidazole group
Describe the phosphate buffer system
- works in plasma and renal tubular cells
- Plasma-
- HPO4:H2PO4 (exchange H+ for H20) Renal-
- Renal tubular cells form Ammonia from AA degradation–Excrete H+ in the form of NH4+
- Conservation of Na and buffering H+
Respiratory center (medulla) is sensitive to:
- PCO2
- PO2
- pH
- Chemoreceptors; in aortic arch and carotid sinuses and are receptive to : dec PO2, pH change, and PCO2 change
Renal compensation responds by…
- Na+-H+ exchange
- ammonia formation
- phosphate buffer system (HPO4-H2PO4)
- Reabsorption/excretion of bicarbonate
Causes of Respiratory Acidosis
- Increase in PCO2
- Hypoventilation
- Respiratory Center depression (alcohol, barbiturates, CO2, morphine, anesthesia)
- Asphyxia
- Pulmonary disease
- Decreased cardiac output
- Apnea
Causes of Respiratory Alkalosis
- Decrease CO2
- hyperventilation
- Respiratory Center Stimulation (CNS disease, Drug toxicity, salicylate poisoning, quinine, sulfonamides)
- hypoxia
- hiccups
- high room or ambient temperature
PO2 of alveolar air is greater than or less than that of inspired air?
Less Than
Diffusion rate of O2 in blood is _____ that of CO2.
1/20
What is the PO2 of venous blood? Arterial?
Venous: 40
Arterial: 90
causes of metabolic acidosis?
- decrease in HCO3
- Excess organic acids:
- –Diabetes, ketoacidosis, impaired liver function, endocrine disorder, convulsions, hypoxia –>lactic acid, shock, late stage salicylate intoxication, MEOH ingestion, ethylene glycol ingestion Excess loss of bicarbonate:
- –Diarrhea, Addisons dis, Renal tubular disease, GI/Pancreatic disease
Causes of Metabolic Alkalosis
- Excess loss of Acid (H+ + HCL)
- Vomiting, diuretics, lavages
- Body deficit of K+ (the less K+, more H+ exchanged for Na creating more acidic urine, alkaline plasma)
- increased reabsorption of HCO3- (edema)
- Hyperaldosteronism (loss of K)
What is the effect of using a tourniquet for blood gas samples?
- creates stasis
- decreasing PO2 & pH
- increasing PCO2
What is ABE?
ABE stands for base excess and it is a clacluation reflecting the possible amount of actual base needed (lost) independent of the PCO2 in non-respiratory conditions
Which component is always calculated in a blood gas determination?
HCO3 (Bicarbonate)
What type of sample could be used for a blood gas analysis?
Heparinized, arterial, venous, capillary, and cord blood
What would be the acid base disorder in a Unconscious patient- known drug overdose (oxycodone) with respiratory depression
—Mixed acid-base disorder
An unconscious patient is experiencing shock and buildup of lactic acid- (Resp alkalosis/Metabolic Acidosis?) in the case of the overdose patient, the drug was oxycodone a morphine derivative that can cause CNS depression- (Resp, Acidosis)
What would be the acid-base disorder in a p atient experiencing pneumonia, anxious and hyperventilating?
Respiratory Alkalosis
Pt. would have a decreased PCO2 with possible decreased gas exchange due to the pneumonia
Would would the acid base disorder be in a p atient with severe sleep apnea and decreased cardiac output (CHF).
—Respiratory Acidosis
reduced cardiac output can have a buildup of CO2 in the tissue and apnea can further cause the increase in CO2.
What impact does an acidosis have on the compensatory mechanisms discussed?
Increase Na-H exchange (Na in and H out) HCO3 reabsorption,
ammonia formation, and phosphate buffer system
