Acid-Base Flashcards
Metabolic disorders involve changes in _____, while respiratory disorders involve changes in _____.
HCO3-, pCO2
normal pCO2 level (ABG)
35-45 mmHg, “remember 40”
normal HCO3- level (ABG)
22-26 mEq/L “remember 24”
normal pO2 and O2 sat
95-100 mmHg, >95%
cardiovascular effects of acidosis
(1) decreased cardiac output
(2) diminished contractility
(3) increased pulmonary vascular resistance
(4) arrhythmias
metabolic effects of acidosis
(1) insulin resistance
(2) hyperkalemia
(3) inhibition of anaerobic glycolysis (generates lactic acid)
CNS effects of acidosis
(1) coma
(2) altered mental status
other effects of acidosis
(1) decreased respiratory muscle strength
(2) dyspnea
(3) hyperventilation (respiratory compensation)
cardiovascular effects of alkalosis
(1) decreased coronary blood flow
(2) arteriolar constriction
(3) decreased anginal threshold
(4) arrhythmias
metabolic effects of alkalosis
(1) decreased potassium, calcium, and magnesium
(2) stimulation of anaerobic glycolysis
CNS effects of alkalosis
(1) reduced cerebral blood flow
(2) seizures
other effects of alkalosis
(1) decreased respiration (to conserve pCO2 and lower pH)
What are three ways acids are formed in the body?
(1) aerobic glycolysis (generates CO2)
(2) diet (0.1 mEq/kg/day consumed)
(3) nonvolatile acid production (lactic and pyruvic acid, TG oxidation to ketone bodies, AA metabolism)
three standard physiological pH regulation mechanisms
(1) buffering
(2) renal regulation
(3) ventilation
What three buffers are present in the body?
bicarbonate/carbonic acid, phosphate, and proteins
The bicarbonate buffer has ______ onset and ______ buffering capacity.
rapid, intermediate
The phosphate buffer has ______ onset and ______ buffering capacity.
intermediate, intermediate
Which buffering system has a rapid onset but a limited capacity?
proteins
Describe how the body uses the bicarbonate/carbonic acid buffering system.
varying the amount of HCO3- (kidneys) and CO2 (lungs) present in the blood, used as first line of pH defense because it is present in the largest amount and is the most readily available
Which two proteins are primarily involved in buffering?
albumin, hemoglobin
Where is a majority of filtered bicarbonate reabsorbed?
proximal convoluted tubule
Describe the mechanism for bicarbonate reabsorption in the PCT.
As filtered bicarbonate passes through the tubule, it combines with excreted H+ to form carbonic acid. Carbonic anhydrase forms CO2 and HCO3- from this, both of which pass readily through the membranes of cells lining the tubule. Once inside the cell, they are converted back into carbonic acid. After dissociation, bicarbonate passes through channels in the basilar membrane (with sodium) back into the blood, while the H+ is excreted back into the tubule.
How do carbonic anhydrase inhibitors cause acidosis?
Anything that limits H+ secretion will limit bicarbonate reabsorption. CA inhibitors prevent the entry of CO2 and H2O back into tubular cells because they are no longer being made from carbonic acid. HCO3- is no longer salvaged by H+, and corresponding acidosis occurs.
By which two mechanisms is new bicarbonate generated? Of these two mechanisms, which has a greater capacity to generate bicarbonate?
ammonium excretion and titratable acidity, ammonium excretion to a greater extent due to increased availability of ammonia compared to phosphate