Anesthesia - Exam 2: Knock Me Out Again (Monitoring to Euthanasia)

Quick review of ASA status

1: normal

2: Mild systemic disease, not limiting function

3: Moderate systemic disease, limits function

4: Severe systemic disease, threat to life

5: <24 hours to live

What are the goals of general anesthesia?

Reversible unconsciousness,

Amnesia,

Analgesia,

Muscle relaxation, and

Autonomic stability

What are the common anesthetic complications?

Hypotension,

Hypoventilation,

Hypothermia,

Bradycardia, and

Pain

The depth of anesthesia is observed as the extent to which the anesthetic depresses what?

The cortex

How can we check the motor reflexes to determine depth of anesthesia?

Palpebral/corneal reflex,

Withdrawal reflex, and

Spontaneous movement

How can we monitor autonomic reflexes for depth of anesthesia?

Respiratory rate,

Heart rate, and

Blood pressure

What is stage 1 of anesthesia?

Stage of voluntary movement and awareness up to loss of consciousness

What is stage 2 of anesthesia?

Stage of involuntary excitement, with exaggerated reflex and hyperventilation

What is stage 3 of anesthesia?

Stage of surgical anesthesia, unconscious with progressive reflex loss

What is stage 4 of anesthesia?

Anesthetic overdose, extreme depression

What are the three planes of stage 3 anesthesia?

Plane 1: Light

Plane 2: Medium

Plane 3: Deep

What happens to the eye in plane 2 of stage 3 in dogs and cats?

Eye rotates ventromedially

What reflex lasts the longest, all the way up to stage 4?

Corneal reflex

What are the typical physical parameters allow you to determine depth of general anesthesia?

Eye position (ventromedial at plane 2),

Palpebral reflex (lost at plane 2), and

Jaw tone (decreases til absent at plane 3)

T/F: Physical parameters also follow progressive signs with injectable anesthetics

False

How can we avoid stage II and move straight to stage III?

Premeds!

Horses with nystagmus, lacrimation, and increased muscle tone are likely in what stage?

Stage 3 plane 1 (light)

What is the graphic representation of the average electrical potential generated by the heart over time?

ECG

What are the two types of hearts due to differences in innervation of the myocardium?

Type A: human + small animal

Type B: large animal + bird

How many waves does a type A heart have?

Three; negative Q, positive R, negative S

How many waves does a type B heart have?

Two, with a negative S

What lead is used to assess type A hearts?

Lead II

What lead is used to assess type B hearts?

Lead I

What color are the lead clips?

RA - white

LA - black

LL - red

What legs are connected by lead I?

RA to LA

What legs are connected by lead II?

RA to LL

What legs are connected by lead III?

LA to LL

T/F: The arm/forelimb is always negative, and if two forelimbs are connected, the right one is negative

True

How does horse lead placement differ?

RA goes over jugular furrow,

LA goes behind elbow over apex, and

LL is ground so it goes anywhere

What is the use of an ECG in anesthesia?

Used to evaluate the electric activity of the heart (arrhythmias)

The pressure exerted by flowing blood on arterial wall is what?

Arterial blood pressure (ABP)

What is the equation for Mean ABP as it relates to cardiac output?

Cardiac Output (CO) x Systemic Vascular Resistance (SVR)

What is the pressure the blood is exerting against the artery wall during systole of cardiac cycle?

Systolic Arterial Pressure (SAP)

What is the pressure the blood is exerting against the artery wall when the heart is relaxing?

Diastolic Arterial Pressure (DAP)

What is the bounded integral from 0 to 100 of the product of 7 and sine of 3 times X cubed, where the contents of the integral are subsequently divided by the sum of 4 time x and 5, solving for x?

1.51

What are the small animal SAP ranges?

90 to 160 mmHg

What are the small animal DAP ranges?

40 to 110 mmHg

What are the small animal MAP ranges?

60 - 100 mmHg

What are the two methods for obtaining blood pressure?

Noninvasive/indirect (doppler, oscillometer)

Invasive/direct (arterial line)

What are the advantages of doppler (inflatable cuff)?

Non invasive,

Easy to use, and

Cheap

What are the disadvantages of doppler (inflatable cuff)?

Only provides SAP,

Accuracy depends on cuff size, and

Operator dependent

What is the main advantage of oscillometric blood pressure monitoring over doppler?

Measures SAP, DAP, and best of all, MAP, which is the most valid pressure

What can cause oscillometric blood pressure monitoring to be inaccurate?

Hyper/hypotension,

Bradycardia,

Arrhythmias, and

Movement

Inflatable cuffs should be what percentage of the limb circumference?

30 - 40%

What is the gold standard for measuring ABP?

Arterial line

When is an arterial line indicated?

In high risk patients,

With expected hemodynamic changes,

Cardiac/pulmonary disease,

Risk of significant hemorrhage, and

Administration of vasoactives

What measures the oxygen saturation (SpO2) of hemoglobin in arterial blood and the peripheral pulse?

Pulse oximetry

What are the four different forms of hemoglobin?

Oxygenated hemoglobin,

Deoxygenated hemoglobin,

Methemoglobin, and

Carboxyhemoglobin

How does pulse oximetry determine if hemoglobin is oxygenated or not?

By light absorption, where deoxygenated absorbs best at 660 nm while oxygenated absorbs best at 940 nm

How do we calculate % saturation?

Number of oxygenated hemoglobin over total hemoglobin times 100

T/F: SpO2 of 90% occurs at 60 mmHg, and is a good indicator

False, this indicates severe hypoxemia

What pressure and percent is considered normal?

110 mmHg and 98%

The value for hypoxemia is what percent and pressure?

80 mmHg and 95%

What does blood gas analysis measure?

pH,

PCaO2 (arterial pressure of CO2),

PaO2 (arterial pressure of O2),

Electrolytes, and

More

What pH is considered normal?

7.4 (slightly basic)

If PCO2 and HCO3 change in the same direction as pH (aka both increase or decrease), then what does this indicate?

Metabolic disruption (acidosis or alkalosis)

If PCO2 and HCO3 change in the opposite direction as pH, then what does this indicate?

Respiratory disruption (acidosis or alkalosis)

Blood gas analysis is the gold standard for assessing what?

Ventilation

What are the disadvanatages of blood gas analysis?

Expense,

Maintenance, and

Arterial samples required

What provides information on respirator rate and end tidal volume CO2 (ETCO2)?

Capnometry

Increased ETCO2 indicates what?

Hypoventilation

ETCO2 should be close to what value in health?

Partial pressure of CO2 (PaCO2)

What is the difference between PaCO2 and ETCO2 in a physiologic condition?

3 to 6 mmHg

What are the two types of capnometers?

Mainstream (sensor in breathing circuit) and Sidestream (sensor in machine)

What are the phases of capnography?

Phase 0 - Rapid downstroke of inspiration

Phase 1 - End inspiration pause

Phase 2 - Rapid upstroke of expiration

Phase 3 - End expiration pause

What is the thermostat of the CNS?

Hypothalamus

T/F: Hypothermia is bad

True

What are the phases of core temperature change?

Phase 1 - fast decrease

Phase 2 - linear reduction

Phase 3 - plateu phase

T/F: The anesthesia record is good

True

When do most fatalities occur in surgery?

During recovery (initial 3 hours)

Where can you find legal guidance for euthanasia in your state?

State practice act

Who provides recommendation of standard of care for euthanasia?

AVMA panel

What is the definiation of an acceptable euthanasia?

Consistently produces human death as a solo agent or single step process

What are the goals of euthanasia?

Minimal pain,

Rapid loss of consciousness,

Cardiac/resp arrest, and

Loss of brain function

What are the seven criteria to confirm death, and which is the only one that is acceptable as a solo sign?

Lack of pulse,

Lack of breath,

Lack of corneal reflex,

Lack of withdrawal,

Lack of resp/heart beat,

Gray mucous membranes, and

Rigor mortis (solo)

What are the three causes of death from euthanasia?

Hypoxia,

Neuronal depression, or

Physical brain disruption

What is the primary site of injection for euthanasia agents?

IV

When is intra-organ injection acceptable?

When patient is anesthetized or unconscious

What is the most used injectable barbiturate for euthanasia?

Sodium pentobarbital

What are the unacceptable solo agents?

Magnesium sulfate,

Potassium chloride,

Cleaning agents (duh?), and

NMBA

What are the advanatages of barbiturates?

Rapid, smooth, and low cost

What is the advanatge of adding lidocaine or phytoin to pentobarbital?

Reduces the schedule

What two conditions make postassium chloride an acceptable euthanasia?

Must be in surgical plane of anesthesia and personnel must be trained

T/F: You need to euthanize fetuses individually

False, just occlude blood supply

What is the acceptable euthanasia method for equine?

Barbiturates

What are the methods of euthanasia for horses if barbiturates are unavailable?

Penetrating captive bolt,

Gunshot, and

Injectable GA with potassium chloride

What are the acceptable forms of euthanasia for dogs and cats?

Barbiturates or non-barbiturate anesthetics like ketamine (if no barbiturates)

Where is penetrating captive bolt acceptable?

In horses, ruminants, or swine