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Acid Base Balance
EMT Paramedic
Fall 2008
And Now!
Acids and Bases
Yippy!
Homeostasis


The biological and chemical processes
occurring in our bodies depend on a
consistent environment.
Homeostasis is our body’s system for
maintaining that consistency.
Homeostasis & Acid-Base


Metabolic processes within our bodies
function within a very narrow pH range.
Many diseases and environmental
influences can greatly impact this delicate
range.
Lets First Review


SpO2 = 90-100 (measures saturated
hemoglobin through skin)
SaO2 = 90-100 (measures saturated
hemoglobin in arterial blood)
More review


PaCO2 = 35-45 (dissolved CO2 in blood)
PaO2 = 80-100 for adult and child
40-70 for newborn
60-80 for geriatric (measures
dissolved oxygen in blood)
Matilda




Matilda is 87 years old. Her doctor has
called and told her to come down because
her blood gasses were off in her labs.
These are her labs.
SpO2 = 68
PaCO2 = 50
PaO2 = 55
Who cares?

You do! Because the more we know
about acid-base derangements the better
we can treat patients in order to correct
the derangements.
Acids and
Bases
Here we go!
Acids

A substance that releases H+ Ions when
dissolved in water
Lactic
acid
Ketones
Carbonic acid
Bases

Also known as alkalis, these are H+
seekers and also dissociate in water.
When bases dissolve in water the hydroxyl
ion is released (OH-) this little guy actively
seeks out and attaches itself to acids
floating around in the blood-stream.
 Bicarbonate
is most common base.
 OH- + CO2 = HCO3
Acid-Base Physiology



During energy production, byproducts are
released. Two of these main byproducts
effect acid-base.
Carbon dioxide (CO2)
Hydrogen (H+)
Control that Hydrogen

The key to acid-base regulation is
controlling hydrogen ion concentrations.
pH

P-what? I thought we were talking about
hydrogen.
The hydrogen ion concentration outside
the cell is typically 4x10-8 mols/L or
0.00000004 equivalents per liter.
That number is to small to work with so
we use the pH scale instead.
pH Scale

Potential of Hydrogen
 1-14
7
is mid-range
 7.35-7.45 is normal for human body.
Hmm? So are we acidic or alkaloid?
pH and Hydrogen


pH levels are inversely proportional to H+
This means as H+ increases pH decreases
and as pH increases, H+ decreases.
Condition
pH
H+
Alkalosis
increases
decreases
Acidosis
decreases
increases
Hmm So?

If we are normally 7.35 to 7.45 and that is
considered slightly alkaloid then at what
point are we acidotic?
 Anything
below 7.35 is acidotic to
humans and anything above 7.45 is
alkaloid.
 0.4
either way is as far as we like to
go. About 6.9 acid and 7.8 alkaline.
Fatal Values

pH of less than 6.9 and pH of greater
than 7.8 are typically not conducive with
life.
Picky Picky


The body must maintain a fairly narrow
alkaline environment in order for things to
go smoothly.
Any imbalances can be very serious.
Back to Matilda





So here are her values from before and
now what do you think that means to her
pH?
SaO2 = 68
PaCO2 = 50
PaO2 = 55
pH= 7.23
How do we keep it all balanced?
Balancing Systems

Buffer System

Respiratory System

Renal System
Buffer System



Fastest acting (nano-seconds)
Considered the chemical sponge (too
much H+ use a sponge to clean it up. Or,
need more give it a squeeze)
It can collect hydrogen ions when they are
over-abundant and release them when
they are scarce.
How does it work?

Basically the cells produce CO2 and H+
during metabolism. The buffer system will
change those two through chemical
reactions to keep things balanced.
H+ <-> HCO3 <-> - H2CO3 <-> - H2O <-> CO2
Hydrogen
Bicarb
Carbonic Acid
Water
Carbon Dioxide
Gosh! What’s that mean?

Easy…if the body needs more acid, the
buffer system takes water and carbon
dioxide and makes carbonic acid (with the
help of the enzyme carbonic anhydrase).
Then carbonic acid can be split apart to
make bicarbonate and hydrogen. This can
go both directions
Respiratory System



Second fastest to respond (usually within
minutes)
Triggered by Chemoreceptors in the
vessels.
Example Diabetic keto-acidosis
Breathe!

When the pH gets a little out-o-wack, a
message is sent to the lungs. It tells them
whether to breathe faster and harder or
slower and more shallow.
How does that work?



Hydrogen binds with bicarbonate. This makes
carbonic acid. Carbonic acid then breaks down
into water and carbon dioxide.
In red blood cells carbon dioxide is carried to the
lungs and exchanged for oxygen.
The majority of CO2 is transported as
bicarbonates in the plasma
So in the lungs?


Oxygen has an affinity to hemoglobin and
it climbs on board kicking off the CO2
The CO2 and water are displaced and
through osmosis and diffusion are blown
out with expiration of air.
Gee Whiz!


After the CO2 has been blown away in the
lungs…what happens?
Exactly! The pH increases, bringing the
body back to normal.
Renal System

If the lungs and buffers are not able to
keep up with the amount of acids, then
the kidneys must take action.
 It
may take the kidneys hours or days
to react to an imbalance.
What do the kidneys do to help?


They regulate pH by expelling excess
hydrogen or bicarbonate ions.
The kidney tubules are smart. When they
expel one ion they will exchange it for
another.
Kidneys work OT with COPD


When someone chronically retains CO2
the kidneys become the primary balancing
system.
Example is the chronic emphysema
patient. They rely entirely on the renal
system to maintain pH.
More Values

Base Excess BE = +or- 6

Bicarb HCO3 = 22-26mEq/L
Acid-Base Derangements

Respiratory:
Acidosis
 Alkalosis


Metabolic:
Acidosis
 Alkalosis

Respiratory Acidosis

Hypoventilation
Retained CO2
 pH decreases


Causes:


Trauma, illness, medications.
You guys can treat this!
Causes of Respiratory Acidosis

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Lungs – COPD, Pneumonia, ARDS
Airway obstruction – Mucous plug,
atelectasis, FBAO
Respiratory depression – anesthesia, OD,
trauma
Inadequate lung expansion – skeletal
trauma, pneumothorax, ascites
S/S for Respiratory Acidosis

H/A (cerebral vasodilation)

Tachycardia (hypercapnia)

Bradycardia (incr. K+)

Cardiac arrhythmias (hyperkalemia)

Decreased CNS – confusion to coma

Neuromuscular weakness - hyporeflexia,
flaccid paralysis
Treatment for Respiratory Acidosis

Adequate hydration

Bronchodilators

OXYGEN
Respiratory Alkalosis

Hyperventilation



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Pain, anxiety
Blows off CO2
pH Increase
O2 or Rebreathe CO2???
Causes of Respiratory Alkalosis

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Anxiety, pain, or hypoxia due to epi
release
Febrile
ASA OD
Brain trauma/tumor
Septic shock (early)
S/S of Respiratory Alkalosis

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Dizziness
Numbness, tingling in fingers, around
mouth
Cardiac arrhythmias (decreased K+ and
Ca++)
Treatment for Respiratory Alkalosis

Rebreathe CO2

OXYGEN
Metabolic Acidosis

Excessive acid production

N/V/D, DM, Rx

pH Decreased

CO2 Normal
EMS treatment is ventilation

Sometimes NaHCO3-
Causes of Metabolic Acidosis

Ketoacidosis

Lactic acidosis

Renal failure

Incr. Metabolic rate

Poisoning

Severe diarrhea
S/S of Metabolic Acidosis

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Skin warm, flushed
Cardiac arrhythmias (decreased
Contractility and inotropic response to
catecholamines)

Lethargy to coma

Decreased Pulse (decreased CO)

Decreased BP, dehydration (GI losses)
Treatment for Metabolic Acidosis

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DKA – insulin, fluids
Alcoholism-related ketoacidosis – glucose
and saline
Diarrhea – correct fluid and electrolyte
imbalances
Acute renal failure – dialysis
Lactic acidosis – correct hypoxia and
hypoperfusion
Treatment for Metabolic Acidosis, cont.

Admin. Sodium bicarb. IV when pH is <7.2

Potassium replacement – when acidosis is
corrected, K+ will shift back into cells =
hypokalemia

Mechanical ventilation; compensatory
hyperventilation
Metabolic Alkalosis

Infrequent

Diuretics, vomiting

Too much IV bicarb

pH Increased

CO2 Normal

HCO3 Increased
H+ + HCO-3 <----> H2CO3 <---> H20 + CO2
Causes of Metabolic Alkalosis

Persistent vomiting

Gastric suctioning

Thiazide diuretics

Antacid over-use

Hyperal, Ringer’s lactate
S/S of Metabolic Alkalosis

Postural hypotension

Muscle weakness due to hypokalemia

Severe dizziness, tingling fingers, toes due
to decreased calcium
Treatment for Metabolic Alkalosis

Fluids and electrolytes

0.45% or 0.9% NS
Cool Web-Sites
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http://www.acid-base.com
http://www.health.adelaide.edu.au/paedanaes/javaman/
Elderly Edna
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Vomiting profusely for 24 hours
pH = 7.46
PCO2 = 45
SpO2 = 92
Metabolic alkalosis
Emphysemic Eddy
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Chronically SOB secondary to COPD
pH = 7.38
PCO2 = 50
SpO2 = 88
Respiratory acidosis
Heroin Holly
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Found unconscious in the 7-11 restroom
pH = 7.20
PCO2 = 55
SpO2 = 50
Respiratory acidosis
Panicky Pat
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Freaking out about an acid/base quiz
pH = 7.48
PCO2 = 20
SpO2 = 100
Respiratory alkalosis