Acid Base Balance

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Acid Base Balance

• EMT Paramedic
• Fall 2007

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And Now!Acids and BasesYippy!
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Homeostasis

• The biological and chemical processes occurring
  in our bodies depend on a consistent environment.
• Homeostasis is our bodys system for maintaining
  that consistency.

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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.

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Lets First Review

• SpO2 90-100 (measures saturated hemoglobin
  through skin)
• SaO2 90-100 (measures saturated hemoglobin in
  arterial blood)

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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)

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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

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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.

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Acids and Bases

• Here we go!

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Acids

• A substance that releases H Ions when dissolved
  in water
• Lactic acid
• Ketones
• Carbonic acid

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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

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Acid-Base Physiology

• During energy production, byproducts are
  released. Two of these main byproducts effect
  acid-base.
• Carbon dioxide (CO2)
• Hydrogen (H)

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Control that Hydrogen

• The key to acid-base regulation is controlling
  hydrogen ion concentrations.

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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.

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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?

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pH and Hydrogen

• pH levels are inversely proportional to H
• This means as H increases pH decreases and as pH
  increases, H decreases.

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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 alkalin.

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Fatal Values

• pH of less than 6.9 and pH of greater than 7.8
  are typically not conducive with life.

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Picky Picky

• The body must maintain a fairly narrow alkaline
  environment in order for things to go smoothly.
• Any imbalances can be very serious.

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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

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How do we keep it all balanced?
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Balancing Systems

• Buffer System
• Respiratory System
• Renal System

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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.

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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 lt-gt HCO3 lt-gt - H2CO3 lt-gt - H2O lt-gt CO2
• Hydrogen Bicarb Carbonic Acid
  Water Carbon Dioxide

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Gosh! Whats that mean?

• Easyif 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

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Respiratory System

• Second fastest to respond (usually within
  minutes)
• Triggered by Chemoreceptors in the vessels.
• Example Diabetic keto-acidosis

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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.

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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

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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.

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Gee Whiz!

• After the CO2 has been blown away in the
  lungswhat happens?
• Exactly! The pH increases, bringing the body back
  to normal.

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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.

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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.

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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.

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More Values

• Base Excess BE or- 6
• Bicarb HCO3 22-26mEq/L

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Acid-Base Derangements

• Respiratory
• Acidosis
• Alkalosis
• Metabolic
• Acidosis
• Alkalosis

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Respiratory Acidosis

• Hypoventilation
• Retained CO2
• pH decreases
• Causes
• Trauma, illness, medications.
• You guys can treat this!

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Causes of Resp. Acidosis

• Lungs COPD, Pneumonia, ARDS
• Airway obst. Mucous plug, atelectasis, FBAO
• Respiratory depression anesthesia, OD, trauma
• Inadequate lung expansion skeletal trauma,
  pneumothorax, ascites

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S/S for Resp. Acidosis

• H/A (cerebral vasodilation)
• Tachycardia (hypercapnia)
• Bradycardia (incr. K)
• Cardiac arrhythmias (hyperkalemia)
• Decr. CNS confusion to coma
• neuromuscular weakness - hyporeflexia, flaccid
  paralysis

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Tx for Resp Acidosis

• Adequate hydration
• Bronchodilators
• OXYGEN

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Respiratory alkalosis

• Hyperventilation
• Pain, anxiety
• Blows off CO2
• pH Increase
• O2 or Rebreathe CO2???

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Causes of Resp Alkalosis

• Anxiety, pain, or hypoxia due to epi release
• Febrile
• ASA OD
• Brain trauma/tumor
• Septic shock (early)

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S/S of Resp. Alkalosis

• Dizziness
• Numbness, tingling in fingers, around mouth
• Cardiac arrhythmias (decr. K and Ca)

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Tx for Resp. Alkalosis

• Rebreathe CO2
• OXYGEN

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Metabolic acidosis

• Excessive acid production
• N/V/D, DM, Rx
• pH Decreased
• CO2 Normal
• EMS tx is ventilation
• Sometimes NaHCO3-

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Causes of Metabolic Acidosis

• Ketoacidosis
• Lactic acidosis
• Renal failure
• Incr. Metabolic rate
• Poisoning
• Severe diarrhea

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S/S of Metabolic Acidosis

• Skin warm, flushed
• Cardiac arrhythmias (decr. Contractility and
  inotropic response to catecholamines)
• Lethargy to coma
• Decr. Pulse (decr. CO)
• Decr. BP, dehydration (GI losses)

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Tx for Metabolic Acidosis

• 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

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Tx for Metabolic acidosis, cont.

• Admin. Sodium bicarb. IV when pH is lt7.2
• Potassium replacement when acidosis is
  corrected, K will shift back into cells
  hypokalemia
• Mechanical ventilation compensatory
  hyperventilation

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Metabolic alkalosis

• Infrequent
• Diuretics, vomiting
• Too much IV bicarb
• pH Increased
• CO2 Normal
• HCO3 Increased
• H HCO-3 lt----gt H2CO3 lt---gt H20 CO2

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Causes of Metabolic Alkalosis

• Persistent vomiting
• Gastric suctioning
• Thiazide diuretics
• Antacid over-use
• Hyperal, Ringers lactate

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S/S of Metabolic Alkalosis

• Postural hypotension
• Muscle weakness due to hypokalemia
• Severe dizziness, tingling fingers, toes due to
  decr. calcium

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Tx for Metabolic Alkalosis

• Fluids and electrolytes
• 0.45 or 0.9 NS

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Cool Web-Sites

• http//www.acid-base.com
• http//www.health.adelaide.edu.au/paed-anaes/javam
  an/respiratory/a-b/AcidBase.html

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Elderly Edna

• Vomiting profusely for 24 hours
• pH 7.46
• PCO2 45
• SpO2 92

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Emphysemic Eddy

• Chronically SOB secondary to COPD
• pH 7.38
• PCO2 50
• SpO2 88

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Heroin Holly

• Found unconscious in the 7-11 restroom
• pH 7.20
• PCO2 55
• SpO2 50

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Panicky Pat

• Freaking out about an acid/base quiz
• pH 7.48
• PCO2 20
• SpO2 100