Clin Med- Fernandez 2

drraythe's version from 2016-02-03 21:54

Acid Base Balance

Question Answer
pH → What does this represent?The [H+] content!
What is pCO2?The partial pressure of carbon dioxide
What is base excess?Amount of base reqd to normalize pH
1° metabolic acidosis → explain this in terms of the components in relation to pH↓ [HCO3-] & ↓ pH
1° respiratory acidosis → explain this in terms of the components in relation to pH↑ PCO2 & ↓ pH
1° metabolic alkalosis → explain this in terms of the components in relation to pH↑ [HCO3-] & ↑ pH
1° respiratory alkalosis → explain this in terms of the components in relation to pH↓ PCO2 & ↑ pH
Why would you calculate a base excess?Allows evaluation of severity of metabolic disturbance (independent of respiratory compensation)
Is alkalemia a POSITIVE or a NEGATIVE base excess?Positive
Is acidemia a POSITIVE or a NEGATIVE base excess?Negative
What are some ways you might know that there is a MIXED disturbance of acid-base balance? (3 ways)(1) Normal pH + abnormal pCO2 or [HCO3-] or BOTH
(2) When PCO2 & [HCO3-] change opposite each other
(3) pH changing in opposite direction for a known 1’ disorder
**What is an exception to the rule about determining if there is a mixed acid-base disturbance?1 of the ways to tell if there is a mixed disturbance is if there is Normal pH + abnormal pCO2 or [HCO3-] or BOTH... HOWEVER! IN A CHRONIC RESPIRATORY ALKALOSIS (breathing too fast too often) the METABOLIC COMPENSATION will return the pH to normal, but this is a 1° chronic condition & NOT a mixed condition!!!
**What is the equation for the Anion Gap?([Na+] + [K+]) – ([HCO3-] + [Cl-]) (positives minus the negatives)
***What do you use an anion gap for?Help define cz of metabolic acidosis
Why is there a "gap" in an anion gap? What is a "normal" anion gap?The "gap" is just artificial, bc we can't measure every ion. We measure more cations than anions on average, thus, "anion gap." a NORMAL anion gap is 12-24 mEq/L
*ONCE AGAIN-ANION GAP IS USED TO MEASURE WHICH ACID BASE BALANCE?Defines the cz of METABOLIC ACIDOSIS (anion acidos..& you eat electrolytes, not breathe them, so, metabolic)
What are the 2 general mechanisms for metabolic acidosis?(1) LOSS OF HCO3-from the body
(2) Excess acid in the system
**Explain how the anion gap is affected/ tries to balance out a metabolic acidosis due to... EXCESS ACID in the systemToo much H+? The H+ will combine w/ the HCO3-in the system. However, this means that whatever anion was accompanying the H+ (for example, HCl) will start to build up then (The H+ binds to HCO3-& then Cl-accumulates)
**So, in which metabolic acidosis does the anion gap remain normal & in which does it ↑?In a LOSS OF HCO3-, Cl-compensates, NORMAL GAP. In an EXCESS OF ACID, the gap will ↑!! (bc compensation will result in accumulation of anion the excess acid was initial attached to)
What are 4 REASONS you'd have excess acid in your system? (Remember the acronym!)D.U.E.L.!
D = Diabetic ketoacidosis
U = Uremic acids (renal failure)
E = Ethylene glycol toxicity
L = Lactic acid (think shock, which results in elevated amount of anaerobic metabolism)
What might an anion gap help you identify?May help identify which disorders are present in mixed disturbance
What does an ↑ in the anion gap mean?↑ in organic acids in body! (Like lactic acid)
Is there ever a ↓ in the anion gap? Explain.VERY RARELY! She gives 3 examples of when this might happen-hypoproteinemia, respiratory acidosis & severe hypernatremia
*Whats the average pH of cats/dogs?7.4


Question Answer
How much of the body is water?TOTAL BODY WATER IS 60% OF THE-LEAN-BODY WEIGHT!
Which is bigger → ICF or ECF? Explain divisionsEVEN THO the ECF if broken into 2 compartments (interstitial & plasma), the ECF is STILL SMALLER than the ICF!!
How/where can water move? Electrolytes?Water moves freely w/ compartments. Electrolytes move easily btwn ECF compartments
What is movement of solutes/electrolytes like in the ICF compartment?It requires a transport system
Larger particles don't easily cross the vascular endothelial membrane-what is the size where a particle is considered large? What do you call these particles & what are some examples?>20 Daltons large. These are "natural colloids" (they attract small charged particles & cz osmotic draw) & some examples are albumin, globulin & fibrinogen
Forces favoring reabsorption to the BVs (starlings forces-explain which forces are doing what to do this)↑ capillary oncotic pressure & low hydrostatic pressure
Forces favoring filtration out of the BVs (starlings forces-explain which forces are doing what to do this)↓ capillary oncotic pressure & high hydrostatic pressure
Never forget, fluids are ___DRUGS
Crystalloids can be used for ___ or ___Replacement or maintenance
What are the 2 kinds of colloids?Synthetics vs natural (like plasma or albumin)
What are 3 examples of fluids you could give which you'd consider "free water"D5W (this is 5% dextrose in water), drinking water & sterile water
What are some pros & cons of crystalloids?PRO: Cheap, easy to use, easy to address overload
CON: Fluid overload is possible, may exacerbate preexisting electrolyte derangements
What is the fluid you use for replacement therapy? What osmolality are replacement fluids? What are the electrolyte levels like?You’d use CRYSTALLOID fluids at a ISOTONIC osmolality (Same osmolality as plasma (290-310 mOsm/L)). The Electrolyte composition similar to ECF (replacing w/o electrolyte imbalance is important)
What is the purpose of replacement fluids?Uses – expand IV & interstitial spaces (maintain hydration)
4 examples of replacement crystalloidsNormosol-R
0.9% Sodium Chloride
Lactated Ringer’s Solution
Plasmalyte 148
When you administer a replacement fluid, what percent of the fluid goes to which compartments & how long does it take?Replacement fluids cz Extracellular expanding → 75% redistributes to interstitium & 25% remains in vasculature. This takes about 30 minutes.
What is "maintenance" in regards to maintenance fluids?Volume of fluid & electrolyte content that body needs for daily balance
What is the osmolality of maintenance fluids like? ExplainHypotonic: less Na, low osmolality, high K compared to plasma
How do maintenance fluids distribute in the body?Distributes to all body fluid compartments
How should you NEVER administer maintenance fluids?NEVER BOLUS! (Higher K+ levels in maintenance fluids than in serum)
What are 4 examples of maintenance fluids?0.45% Sodium Chloride
Plasmalyte 56
1/2 Lactated Ringer’s Solution w/ 2.5% Dextrose
"Free water" is a solution which contains...Contains NO electrolytes or buffers!
What is free water used for? What is a good example? How should you NOT administer it?Used to replace free water deficit → such as in hypernatremia & Ongoing free water losses (DI). An example of free water is D5W (water w/ 5% dextrose)-the dextrose is just to ↑ osmolality (252 mOsm/kg)... & NEVER BOLUS
What are 2 examples of things where HYPERtonic crystalloids are super helpful?In situations like shock resuscitation, cerebral edema too
What is a hypertonic crystalloid? What is the osmolality of this hypertonic solution & what is normal for the body? What are you creating by administering this?HYPERTONIC SALINE solution (7.2-7.5%) (Fun note: the ocean is like 3.5). The Osmolality is 2400mOsm/L! (normal is like 290, FYI). By administering this solution you are creating an osmotic gradient
How do hypertonic crystalloids redistribute among the body compartments?The fluid Redistributes 1:3 vascular to interstitial ratio
What is the unique benefit provided by a solution being hypertonic? Explain some specifics of this benefit.Rapidly expands IV volume w/ small volumes administered! This small amount will cz a 3-6 times expansion!
How much/how do you administer hypertonic fluids?Typically give in 3-4ml/kg boluses over 4 minutes
What are some pros to hypertonic crystalloids? What are some cons?PROs: Small volume, Czs arteriolar vasodilation & improved microcirculation, Good for traumatic brain injury, Cheap, Quick set-up
CONs: Cannot give to a dehydrated PTx, HYPERNATREMIA (ESP renal PTxs who might not be able to excrete the excess Na+), ↑ osmolality, Can lead to bradycardia, hypotension, bronchoconstriction w/overly fast administration
When are colloids indicated?Intravascular volume expanding, or in low oncotic states (like hypoalbuminemia)
What is the dose/route of colloids you should give as a fluid challenge? How about as a shock dose? (Dogs & cats)CHALLENGE: 5ml/kg (3ml/kg for cat) bolus as fluid challenge
SHOCK: 10-20ml/kg shock dose (5-10ml/kg for cat)
What are the 3 examples of colloid fluids she gives?(1) Hydroxyethyl starch (“Hetastarch”) (6% solution)
(2) Dextran-70 (6% solution)
(3) Plasma, Canine Albumin (no human Alb!!)
What are the PROS & CONS of colloid fluids?PROS: Vascular volume expansion w/ lower fluid administered, relatively cheap, Useful in PTx clinical for hypoalbuminemia
CONS: Can’t remove it easily if overload, Coagulation impairment (>20-40ml/kg/day), Renal insult, allergic rxns (rare).
How much colloid would you have to give PER DAY to cz coagulation impairment?>20-40ml/kg/day
If you are concerned about shock, you would want to assess the perfusion Parameters of the animal. What are these?Mentation
Pulse quality
Heart rate
Extremity temperature
What is the SHOCK RATE for dogs? Cats? How would you administer?DOGS: 90ml/kg
CATS: 60ml/kg
(What you wanna do is give little boluses, reassess & then give more as needed →) 10-20ml/kg increments & monitor response
If you are Txing intravascular losses, which fluid do you want to give? How would you give it? What is the goal? (See other card for sp. based amounts etc)Use Isotonic crystalloids, in a IVF bolus. You want to Give rapidly (pressure bag, syringe)
What does PRN mean?PRN = as needed
If you need to treat intravascular loss, do you want to give the fluids slowly or quickly?GIVE RAPIDLY!
If you can't give IV fluids but you must give lots of fluids ASAP, what should you do?Give IO! (Intraosseous...goes right to the blood)
When you give IVFs, how long do they expand/stay in the IV space?30min
Dehydration is mainly a loss from which body compartment?The INTERSTITIUM of the ECF
What % dehydrated is considered "subclinical dehydration"? & how would you know they were this dehydrated if it's subclinical?5% & under is subclinical. You might not be able to tell, but if the dog has been vomiting a bunch, it's probably at least a little dehydrated
At what percent dehydration have you crossed into life-threatening territory?Greater than 12 percent → welcome to shock country
How would you determine the volume of fluid you'd need to replace in a dehydrated animal?Assess hydration-estimate % deficit. Then % deficit x body weight = volume to replace
If you are doing fluid replacement therapy for a fluid deficit, after you have determined the volume you are going to give, would you want to replace the deficit slow or fast? (Be specific)Replace deficit over 4 – 24 hours
If you are doing fluid replacement therapy, what factors MUST you consider when determining how much to give?1st determine DEFICIT AMOUNT, THEN ALSO ADD any ongoing losses, then account for MAINTENANCE ALSO!!!
What are the CS of a 5-8% dehydrated PTx?↓ skin turgor, dry MM
What are the CS of a 8-10% dehydrated PTx?↓ skin turgor, dry MM, +/-sunken eyes, slightly prolonged CRT
What are the CS of a 10-12% dehydrated PTx?Severe skin tenting, prolonged CRT, dry MM, sunken eyes, +/-signs of shock
What are the CS of a >12% dehydrated PTx?All of the above (Severe skin tenting, prolonged CRT, dry MM, sunken eyes, +/-signs of shock) + shock; often life threatening
You shouldn't be afraid to push fluids, EXCEPT when...They don't have good hearts or kidneys
If you have interstitial loss of fluids, do you want to replace w/ fluid, or w/ fluid & electrolytes? How do you want to administer it?Fluid & electrolytes! You can admin IV or SQ, but SQ space is usually not enough volume
What are 2 examples of when a PTx will have a loss of HYPOTONIC fluid? What complication will/might arise?Usually hypotonic loss w/ diabetes insipidus & prolonged panting.... this usually leads to & ↑ in the ECF osmolality....esp. hypernatremia
Does hypotonic loss of fluid deplete the ICF, the ECF, or both?Both
What are some examples of situations that would result in hypertonic solute loss? What complication will/might arise?Situations like heat exhaustion or concentrated urine might result in hypertonic fluid loss. This often leads to hypoosmolality & very often, hyponatremia.
If you are in a hypoosmolar state, what does the water do? What are the resulting problems?Water moves into the ICF (bc the ECF doesnt have enough solute to create a draw for water) → dehydration, cellular edema
*If your PTx is in diabetic ketoacidosis, what fluid should you NOT give them?Don’t give LRS – can’t convert lactate → bicarbonate
*Which fluid is preferable to give in young animals? Why?LRS is preferable bc lactate is fuel for neonates
* If your PTx is in Hypochloremic metabolic alkalosis, what fluid would be best?Benefit from ↑ chloride in 0.9% NaCl
*If you have a PTx w/ head trauma, which fluid would you want to give & why?0.9% NaCl least likely to cz osmotic water shiftsI
If youre giving fluid IV, what kinda catheter would you want to use?Short, large bore
What situations would you use IO admin of fluids in?Emergencies, exotics & pediatrics
When would you NOT do IO admin of fluids?Never w/ bone fractures!