Transcript Anatomy & Physiology

Denver School of Nursing – ADN & BSN Programs
Lecture: Fridays 3:00pm – 9:00pm
No Laboratory component for this class
BIO 206 & 308 – Ch 4 – pH & Fluid Balance
Distribution of Body Fluids
Total body water – all fluids 60% of weight
Intracellular fluid (ICF) 2/3 TBW
Extracellular fluid (ECF) 1/3 TBW



Interstitial fluid – between cells
Intravascular fluid – blood plasma
Lymph, synovial, intestinal, CSF, sweat, urine,
pleural, peritoneal, pericardial and intraocular
fluid
“Cells live in a fluid environment
with electrolytes and acid base
concentrations maintained within a
narrow range”
changes or shifts → radically alter
metabolism → life threatening

Sodium (Na+)
 Primary ECF cation
 Regulates osmotic forces
 Role
▪ Neuromuscular irritability, acid-base balance,
cellular reactions, and membrane transport

Chloride (Cl-)
 Primary ECF anion
 Provides electroneutrality
Sodium and Water Balance
Balance between Na+ and H2O  ↑ or ↓ of salt
 ↑ or ↓ water
Tonicity – change in concentration
of solutes (salt) with relation to
solvent (water)
Tonicity (280 – 294m Osm)

Isotonic – 0.9% NaCl – iso osmolar
imbalance no change in cells

Hypertonic – ECF > 0.9% NaCl – (↓
H2O or ↑ salt) cells shrink

Hypotonic – ECF < 0.9% NaCl (↑ H2O
or ↓ salt) cells swell
“Extracellular Fluid”- interstitial
space

90% ECF cations
135 – 145 mEq/L

Hypernatremia - > 145 mEq/L

Hyponatremia - < 135 mEq/L

Hypernatremia-causes
•
↑ Na or ↓ H2O
IV therapy – acidosis (NaHCO3)
Cushing's Syndrome - ↑ ACTH → aldosterone
fever, respiratory infection - ↓ H2O
diabetes, diarrhea - ↓ H2O
↓ H2O intake - coma
• H2O movement ICF → ECF(interstitial)
•
•
Manifestations
– Intracellular dehydration: convulsions, thirst,
fever, muscle twitching, hyperreflexia
Hyponatremia

↓ Na or ↑ H2O

Vomiting, diarrhea, GI suction, burns,
diuretics, D5W replacement (isotonic
sol’n)

Manifestations
 Lethargy, confusion, depressed reflexes,
seizures, coma, hypotension, tachycardia, ↓
urine output
Hypochloremia

Result of hyponatremia or ↑ HCO3

Vomiting – loss HCl

Cystic fibrosis
Potassium (resting potential)



Major intracellular electrolyte
98% intracellular – Na – K – ATP Pump
3.5 – 5.0 mEq/L

Transmission and conduction of nerve
impulses, normal cardiac rhythm,
skeletal and smooth muscle
contractions: “action potentials”

“Da BAD BOY of ELECTROLYTES”
Potassium Levels
Change in pH affects K+ balance
Acidosis causes:
↑ ICF H+ → K+ moves out to ECF maintains
+ ion balance

Aldosterone; insulin, epinephrine
Alkolosis causes:
K+ → into cell


Glucagon # entry into cell
Glucocorticoids → K+ excretion
Hypokalemia
 K+ < 3.5 mEq/L

↓ intake, ↑ loss, ↑ entry into cells

Manifestations: membrane
hyperpolorizations ↓ excitability –
weakness, smooth muscle,
atrophy, cardiac dysrhythmias
(bradycardia…asystole)
Hyperkalemia
 K+ > 5.0 mEq/L – rare

↑ shift from ICF (acidosis), ↓ renal
excretion, insulin deficiency or cell
trauma
Hyperkalemia

Mild attacks
 ↑ neuromuscular irritability – tingling of
lips & fingers, restlessness, intestinal cramps
– diarrhea

Severe attacks
 No repolarization → muscle weakness, ↓ tone,
flaccid paralysis
 Cardiac dysrhythmias “funky chicken”
Calcium (threshold potential)


99% located in bone – hydroxyapatite
Bone, teeth, blood clotting, hormone
secretion, cell receptor function

Hypo - ↓ block of Na into cell
↑
neuromuscular excitability (muscle cramps)

Hyper - ↑ block Na - ↓ neuromuscular
excitability (muscle weakness, cardiac
arrest, kidney stones, constipation)

Hypo - ↓ block of Na into cell
↑ neuromuscular excitability (muscle cramps)
Source: Review of Clinical Signs, Dr. Frank Urbano MD 2007.

Low SERUM K...decreased excitability
 Nerves & muscles…bradycardia---asystole

High SERUM K …increased excitability
 Cardiac dysrhythmias

Low SERUM Ca… increased excitability
 “Chvostek & Trousseau’s Signs”

High SERUM Ca… decreased excitability
pH (0 to 14)
Inverse logarithm of the H+ concentration 0.0000001 mg/L – 1x10 -7
so pH = 7
 pH = power of hydrogen
 pH changes by one unit (7 → 6)
[H+]
10 fold


Biological fluids
pH < 7.4 = acidic
> 7.4 = basic
Physiologic Range of Blood pH = 7.35-7.45
pH
 Acids are formed as end products of
protein, carbohydrate and fat
metabolism

Narrow “life range” –
7.35 – 7.45
Bone – lung – kidneys – major regulatory
organs

“Absolute Range of Life:6.8-7.8”
pH
 Body acids exist in two forms
 Volatile H2CO3 (maybe eliminated as
CO2)
 Nonvolatile – eliminated by kidneys
sulfuric, phosphoric
Image from: http://www.answers.com
Image from: http://www3.oes.edu & http://www.fitnessspotlight.com
Image from: http://www.getfit4kidz.com/
Water Movement Between ICF and ECF
“water, nutrients and waste products”
capillary

interstitial space
•
#1 Capillary hydrostatic pressure
• blood pressure “fluid out”
•
#2 Capillary oncotic pressure
• water attraction “fluid in”(Plasma Proteins)
•
#3 Interstitial hydrostatic pressure
• fluid towards capillary
•
#4 Interstitial oncotic pressure
• water attraction “fluid in”
water movement
Source: Huether, McCance Understanding Pathophysiology 4th Ed. 2008
Edema!!
Edema: 4 Major Causes
“excessive accumulation of fluids within the
interstitial space”

1)↑ hydrostatic pressure
 Venous obstruction – DVT, hepatic obstruction
 Salt and water retention – heart, renal failure

2)↓ plasma oncotic pressure
 ↓ albumin – liver disease, malnutrition, kidney
disease, burns, hemorrhage

3)↑ capillary permeability –
trauma, burns, neoplastic and
allergic reactions

4) Lymph obstruction – removal
of nodes (surgery), inflammation or
tumors
Source: Huether, McCance Understanding Pathophysiology 4th Ed. 2008

From your A&P sources…

What are the two most important body
systems for fluid, Electrolyte, and pH balance??

What are the two most important regulatory
systems for fluid, electrolyte and pH balance?
 1)
 2)
 When the Blood pH is low, it is called?
 When the Blood pH is high, it is called?

1) Metabolic Acidosis

2) Metabolic Alkalosis

3) Respiratory Acidosis

4) Respiratory Alkalosis
Much more detail to come latter in the lecture…
Image from: http://academic.kellogg.edu
Image from: http://academic.kellogg.edu

Physiology of the Urinary System:
 Renal function
▪ Filtration
▪ Reabsorption
▪ Secretion
 Regulation of Urine Volume
▪ Renin Angiotensin Aldosterone system (RAAS)
Image from: http://www.answers.com
Sodium, Chloride & Water
Balance
“kidneys and hormones” – central
role
 Water : ADH – hypothalamus –
posterior pituitary
 Na+
and Cl-
 aldosterone – adrenal gland
 Natriuretic hormones– atrial muscle
Physiological pH Control Systems- (p.1003 of our text)
Type
Response Time
Example
“Chemical buffer
systems”
Immediate
1) Bicarbonate
buffer system
2) Phosphate buffer
system
3) Protein buffer
system
“Physiological buffer
systems”
a) Minutes
a) Respiratory
Response system
b) Renal response
system
a) Hours
The Chief Blood Buffer is a Mixture of Bicarbonate and Carbon
Dioxide
~ All body fluids, inside or outside cells have buffers which defend the body against
pH changes
~ The most important buffer in extracellular fluids, including blood, is a mixture of
carbon dioxide (CO2) and bicarbonate anion (HCO3)
~ CO2 acts as an acid (it forms carbonic acid when it dissolves in water), donating
hydrogen ions when they are needed
~ HCO3 is a base, soaking up hydrogen ions when there are too many of them
~ The HCO3/CO2 buffer system is extremely important because it can be rapidly
readjusted in alkalosis and acidosis
~ There are also other buffers in blood, such as proteins and phosphate
~ The ability to resist pH change is given by the buffer capacity, which is a function of
the concentration and dissociation constant (pK) of the weak acid
~ If there is more than one buffer in the solution, the buffer capacities are additive
Source: http://www.mpoullis.net
Source Mayo Clinic: http://discoverysedge.mayo.edu
The Chief Blood Buffer is a Mixture of Bicarbonate and Carbon
Dioxide
Source: http://www.mpoullis.net
Too Much CO2 or Too Little HCO3 Will Cause Acidosis
~ The balance will swing toward a low pH, producing acidosis
~ Pathology leading to this Acidosis can be:
1) CO2 increase via hypoventilation (pneumonia, emphysema)
2) Metabolic conditions (ketoacidosis due to excess fat metabolism
(diabetes mellitus) which will lower bicarbonate.
Source: http://www.mpoullis.net
Too Much HCO3or Too Little CO2 Will Cause Alkalosis
~ The balance will swing toward a high pH, producing alkalosis
~ Pathology leading to this Alkalosis can be:
1) CO2 decrease via hyperventilation (Remember Respiration “Blows off
CO2”)
2) Emesis removed stomach acid and raises bicarbonate
(Alkalosis is clinically less common than acidosis)
Source: http://www.mpoullis.net

Buffer is a chemical that binds XS H+
or OH- without a significant change in
pH

Consists of a PAIR of a weak acid and
its conjugate base

Most important plasma buffering
system
1. Carbonic acid – bicarbonate system
2. Hemoglobin (intracellular)
H2O + CO2
Lung
H2CO3
1
H+ + HCO320
Kidney
Phosphate- HPO4

Compensation

Correction – buffer pairs →
Ammonia – NH3
 Respiratory - ↑ or ↓ CO2
 Renal - ↑ or ↓ acidity / alkalinity of urine
Other Systems not previously discussed

Proteins: - charge, mostly intracellular
Hemoglobin –
H + Hb → HHb + CO2 → HHbCO2
(weak acid)
.

Figure 4-10 (p. 116)
Source: Huether, McCance
Understanding Pathophysiology 4th Ed. 2008

Figure 4-11 (p. 117)
Source: Huether, McCance
Understanding Pathophysiology 4th Ed. 2008

Figure 4-12 (p. 117)
Source: Huether, McCance
Understanding Pathophysiology 4th Ed. 2008

Figure 4-13 (p. 118)
Source: Huether, McCance
Understanding Pathophysiology 4th Ed. 2008
1) Metabolic Acidosis – Different diseases such as untreated diabetes
mellitus or during starvation, the blood pH becomes acidic because there is
higher carbonic acid to bicarbonate ratio. This stimulated the respiratory
centers to increase respiratory rate and thus “blow off” carbon dioxide. The
kidneys will also excrete increased levels of H ions and NH3. If these
mechanisms can not compensate then the pathologic condition of
uncompensated metabolic acidosis develops
2) Metabolic Alkalosis – Excesive use of antacids or excessive emesis can
produce metabolic alkalosis. Initially the condition can result to bicarb levels
up to 40 x greater than carbonic acid. Compensatory mechanisms function to
increase the carbonic acid and decrease the bicarb. This is done via
hypoventilation and increased renal excretion of bicarb. Once again if
compensation is not adequate uncompensated metabolic alkalosis develops.
3) Respiratory Acidosis – Pneumonia, emphysema and barbiturate OD are
leading causes of retention of carbon dioxide in the blood. In these
conditions the carbonic acid is greater than bicarbonate buffer. The
compensatory reaction is for the kidneys to excrete H ions and retain more
bicarbonate.
4) Respiratory Alkalosis – Hyperventilation due to a multitude of reasons
(fever or hysteria) can result in excessive loss of carbonic acid and lead to
respiratory alkalosis. Once again the kidneys will attempt to compensate via
increased H ion reabsorption and increased bicarbonate excretion.
Source: http://www.mpoullis.net

1) Metabolic Acidosis

2) Metabolic Alkalosis

3) Respiratory Acidosis

4) Respiratory Alkalosis
pH
pO2
pCO2
HCO3
SaO2
=
=
=
=
=
7.35 – 7.45
80 to 100 mmHg
35 – 45 mmHg
22-26 mEq/L
> 90%
Patient
ABG:
1.
2.
3.
4.
pH
pCO2
pO2
HCO3
=
=
=
=
pH
=? →
pCO2 = ?
→
HCO3 = ? →
pO2 = ?
→
7.3
40 mmHg
70 mmHg
20 mEq/L
acidosis
normal
low
low

Patient







pH = 7.30
Pco2 = 30mm Hg
Po2 = 68mm Hg
HCO3 = 14mEq/L
O2 sat. = 92%
1.
2.
3.
4.
5.
pH = acidotic
Pco2 = alkalotic
Po2 = hypoxic
HCO3 = acidotic
O2 sat = low
“same directions = compensation”
 Metabolic acidosis with partial respiratory
compensation

ACIDOSIS: CNS depression
 Stupor to confusion to coma

ALKYLOSIS: CNS irritability
 Restlessness to seizures
Image Source: http://www.gilmerfreepress.net