Pathophysiology Chapter 25

Acid

a substance that donates a proton, H+

Base

a substance that accepts a proton, H+

Neutrality

concentration of hydrogen ions in pure water(H+) as well as equal amounts of hydroxyl ions(OH-)

Acidity

high concentration of hydrogen ions, H+

Basicity

low concentration of hydrogen ions, H+

Acidic

pH less than 7

Basic

pH greater than 7

normal blood pH

7.35-7.45, 7.4 best

blood pH importance

at pH less than 7.3 or greater than 7.5 proteins and vital organs lose function, pH must be maintain in the narrow physological range

chemical buffer

substance that minimizes pH changes of a solution follwoing the addition of small amounts of acid or base to that solution

carbonic acid

H2CO3

bicarbonate

HCO3-

pH=

pKa + log(HCO3-/CO2)

(HCO3-)/(CO2) must

equal 1 in order to keep pH in normal range, if one rises or falls the other must equally as well

henderson hasselbalch equation

mathematical description of the pH of a buffered solution

Physiological buffers

hemoglobin, bicarbonate, phosphate, proteins

Physiologic acids

body's metabolic pathways produce a number of waste products that are acids, volatile and fixed acids

volatile acids

carbon dioxide, CO2

Fixed acids

lactic acid, acetoacetic acids

respiratory acid base balance regulation

lungs, small and quick changes to maintain pH homeostasis

renal acid base balance regulation

kidneys, slow long term changes to mantain pH hoemostasis

buffer systems

regulate H+

Bicarbonate buffer system

ratio between H2Co3 and HCO3- is maintained by the lungs

Compensation

physicological response that acts to normalize blood pH, can be partial or complete

Metabolic causes can be compensated

by a respiratory change fast in minutes to hours

respiratroy causes can be compensated

by a renal change, slowly begins in minutes but takes days to be effective

Respiratory acidosis

abnormally high PCO2 in systemic blood

Respiratory acidosis causes

inadequate exhalation of CO2 caused by emphysema, pulmonary edema, injury to medulla oblongata, airway obstruction, or diseases of muscles invovled in breathing

Respiratory acidosis treatment

renal compensation can help but treatment is aimed at correcting respiratory problem

respiratory alkalosis

abnormally low PCO2 in systemic blood

Respiratory acidosis causes

hyperventilation, severe anxiety, drug induced, pain induced, stroke induced, pulmonary embolism

Respiratory acidosis treatment

paper bag to breath into, high amounts of CO2 being inhaled, renal compensation will occur but can be quickly fixed

metabolic alkalosis

systemic arterial HCO3- raises about 26, causing pH to rise, H+ decreases or HCO3- increases

metabolic alkalosis causes

vomiting(loss of HCl), gastric suctioning, hyperaldosterone, hypokalemia, volume deplation

metabolic alkalosis treatment

correcting the problem, fluids to correct electrolyte deficiencies but body will hypoventilate

MEtabolic Acidosis

Systemic arterial HCO3- drops below 22, dropping blood pH

MEtabolic Acidosis causes

loss of bicarbonate due to diarrhea or renal dysfunction, accumulation of acid in ketoacidosis or failure of kidneys to excrete H+(MUDPILES)

MEtabolic Acidosis treatment

correct the problem, administer sodium bicarbonate, but body hyperventilates to get rid of CO2