CRNA Interview Clinical Review

ABG

pH range

7.35 - 7.45

ABG

pCO2 range

35-45 mmHg

ABG

HCO3 range

22 - 26 mmol/kg

ABG

Base Excess

-2 to 2

ABG

PO2

80 - 100 mmHg

ABG

SaO2 (SpO2)

95-99% on RA

Respiratory Acidosis

pH < 7.35

PaCO2 > 45 (Primary)

HCO3 > 26 (Secondary)

Metabolic Acidosis

pH < 7.35

HCO3 < 22 (Primary)

PaCO2 < 35 (Secondary)

Respiratory Alkalosis

pH > 7.45

PaCO2 < 35 (Primary)

HCO3 < 22 (Secondary)

Metabolic Alkalosis

pH > 7.45

HCO3 > 26 (Primary)

PaCO2 > 45 (Secondary)

PaCO2 is a ____, controlled by the _____

Acid

Lungs

Respiratory parameter - rapid change

HCO3 is a ____, controlled by the _____

Base

Kidneys

Metabolic parameter - slow change

Anion Gap

Normal 5 - 15 mEq/L

Difference between positive and negative anions - increase in gap correlates with metabolic acidosis

(Na + K) - (Cl + HCO3)

Problems Associated with an Increase in Anion Gap

Ketoacidosis

Uremia

Salicylate intoxication

Methanol

Alcoholic ketosis

Unmeasured osmoles: ethylene glycol, paraldehyde

Lactic acidosis: shock, hypoxemia

Problems Associated with a Normal Anion Gap

Saline Infusions (hyperchloremic acidosis)

TPN

Diarrhea

Ammonium chloride

Acute renal failure, sometimes chronic

(These are less common - normal anion gap metabolic acidosis)

Normal SVR

800 - 1200

SVR Calculation

((MAP - CVP) / CO) x 80

Cardiac Output Calculation

CO = HR x SV

CO Normal Range

4 - 8 L/min

Nicardipine

Class - Antihypertensive

MOA - Ca Ion Influx Inhibitor or Ca Channel Blocker - slows the transmembrane influx of Ca ions into cardiac muscles and smooth muscle without changing serum calcium concentrations

- selective to vascular smooth muscle than cardiac muscle

- reduces afterload more

- with little or no negative inotropic effect (unless in pts with severe LV dysfunction - leading to worsened failure)

(Contraction of heart and smooth muscles dependent on extracellular Ca ion moving into muscle cells through specific ion channels)

- liver metabolism mainly

Hydralazine

Class - Antihypertensive

MOA - Unknown - Direct vasodilation of smooth muscle (arteries and arterioles) - decrease SVR and afterload

- Reflex tachycardia (baroreceptor reflex)

- liver metabolism, kidney excretion

Labatalol

MOA - mix A1, and B1 and B2 adrenergic receptor blocker

Metoprolol

MOA - selective B1 receptor blocker

Esmolol

Class II antiarrhythmic

MOA - cardio-selective B1 blocker with rapid onset and short DOA

Activation of these receptors cause stimulatory responses

Alpha 1

Beta 1

Activation of these receptors cause inhibitory responses

Alpha 2

Beta 2

Beta 3

Alpha 1 Receptors

- More responsive to Norepi than Epi

- Activation causes vasoconstriction

- Abundant in vascular smooth muscle

- GI & urinary sphincters

- dilator muscle of the iris (reducing tone enlarges the pupils)

- arrector pili muscle of the hair follicles (reducing tone causes hair to stand on end)

Alpha 2 Receptors

- Secretary terminals of some postsynaptic adrenergic neurons

- negative feedback mechanism on Norepi secretion

Beta 1 Receptors

- cardiac pacemakers (increase rate)

- myocardium (increase force of contraction)

- salivary gland ducts

- eccrine and apocrine sweat glands

Beta 2 & 3 Receptors

RELAXATION (Tx Asthma and premature labor)

When stimulated by Epi or Norepi - inverse response

- Smooth muscle (muscle tone relaxation) in GI tract

- Urinary bladder (B3)

- Skeletal muscle arteries (enhance blood flow when epi is present)

- Bronchial tree (enhance blood flow when epi is present)

- Some coronary vessels

Dopamine

- stimulating B1 receptor (increase HR and contractility) at 5 - 10 mcg/kg/min

- minor B2 stimulation related to peripheral vasodilation (at low doses)

- higher dosing (10 - 20 mcg/kg/min) can stimulat alpha receptors leading to vasoconstriction and increase in BP

- used in tx of septic or cardiogenic shock

- neurotransmitter in the brain

- inhibits norepi release and acts as vasodilator

- increase Na secretion and UO in the kidneys

Dobutamine

- Stimulates B1 receptor (increase heart rate and contractility)

- has less B2 stimulation (vasodilation)

- tx heart failure and cardiogenic shock

- can further lower SVR therefore not used in tx of septic shock

Initial defect in septic shock

drop in SVR (vasoconstrictor recommended)

Epinephrine (Adrenaline) vs. Norepinephrine

Epi - increases HR, cardiac output but not really BP (Primarily B1 stimulation)

- B2 - drops SVR

- bronchodilator (B2)

- mydriatics (B2)

- A1 & A2

- Vasoconstrictor at higher concentrations

Norepi

- transient increase in HR and inotropy (B1) - later decreases due to baroreflex

- A1 & A2

- Increases CO and SVR (SBP)

- NO B2 stimulation

Precedex vs. Propofol

Benzos & Opioids

Anesthetic Gases

Paralytic and Reversal Agents

Brain Stem Reflexes

Cranial Nerves

Oxyhemoglobin Dissociation Curve

SIADH & DI

Vasopressin

Neosynephrine

Normal PAP

20/8 to 30/15

Mean < 20

Normal PAOP

8-12 mmHg (varies depending on LV function)

Normal PVR

50 - 250

Normal ICP & CPP

ICP 5 - 15 mmHg

CPP 70-80 mmHg

Shock States and Hemodynamics

PA Artery Wave

Coagulation Cascade

ACLS concepts***

PEA without a pulse

Nitroprusside & Nipride

Milronone