anesthesia- maintenance period

maintenance period definition

period of time following anesthetic induction in which a stable level of anesthesia is achieved

why is an animal getting too deep

1. individual variation

2. ventilating too frequently

3. improper vaporizer function

4. technician error

why is an animal getting too light

1. innapropriate O2 flow rate

2. is there gas in the vaporizer?

3. are there leaks in the system?

4. is your et tube placed properly?

5. over usage of O2 flush valve

3 body systems we monitor

• cardiovascular system

• respiratory system

• CNS

blood pressure normals

• systolic- 80-140 mmHg

• diastolic- 50-80 mmHg

• MAP- 70-100 mmHg

3 things that contribute to blood pressure

1. cardiac output

2. blood volume

3. vascular resistance

cardiac output equation

CO= SV x HR

causes of hypotension

• hypovolemia

• overdose of anesthetic

• decrease in CO

causes of decrease in CO

• bradycardia

• intense tachycardia

• v tach

• decreased SV

• drugs

• decrease in venous return to heart

• positioning of the pt

managing hypotension

1. ± decrease anesthetic gas

2. bolus IV fluids

3. give pos inotropic drugs

pos inotropic drugs

• ephedrine

• dopamine

• dobutamine (equine)

• ca gluconate

3 ways to measure BP

• doppler

• oscillometric

• direct arterial catheter

values doppler gives you

• BP (systolic)

• pulse rate

values pulse oximeter gives you

• Spo2 (or Pao2)

• pulse rate

locations pulse ox can be placed

• tongue

• pinna of ear

• webbing of toe

• vulva

• prepuce

• rectal probe

causes of desaturation

• V/Q mismatch

• disconnect of breathing system

• blocked airways

• inadequate o2 flow rate

• erroneous readings

  • probe placement, motion of pt, cautery

• hypovolemia

general anesthesia leads to a decreased what?, it can also lead to?

• tidal volume of 25%

• hypercapnia or atelectasis

4 ways to monitor respiratory system

• capnograph

• res bag

• flutter valves, et tube fogging, esophageal stethoscope, pulse ox

• rate and character

capnograph gives what values

• RR

• etco2

• inco2

2 types of capnographs

• mainstream

• sidestream

controlled ventillation

controlling the volume of air, rate of respiration and pressure of air being introduced into the animal

normally ventilate every 5 min, why?

• prevent hypercapnia

• prevent atelectasis

3 steps to ventilating

• close pop off

• squeeze res bag to 20 cmH2O

• open pop off

why provide pos pressure ventilation

• prevent hypercapnia

• precent atelectasis

• helps mitigate hypoventilation

• help counteract low tidal volume

• prevent hypoxemia

• if surgical procedure requires it

how to completely take over respirations

• ventilate pt at rate of 12-16 rpm to gain control of pt breathing

• after approx 3-5 min pt will not be breathing on their own

• decrease ventilations to 8-12 rpm for remainder of surgery

• after surgery must gradually decrease ventilations to wean pt off

mechanical ventilators

• machine will always be hooked up to the res bag port

• good for long procedures

mechanical ventilators control what 4 things

• inspiratory pressure

• inspiratory time

• tidal volume

• respiratory rate

3 types of mechanical ventilators

• pressure cycle ventilator

• volume cycle ventilator

• time cycle ventilator

values ecg gives you

• HR

• heart rhythm

most common artifacts on ecg

• movement

• cautery

• 60 cycle interference

• drying of the electrodes

PVC’s (premature ventricular contractions)

• some ectopic source causing ventricles to fire prematurely

• have widened QRS complex

• see occasionally, no tx needed

2 types of PVC’s

• unifocal- originates from same place in ventricle

• multifocal- originates from multiple places

generalized causes of PVC

• electrolyte imbalance

• GDV

• excess circulating catecholemines

• drugs

tx of PVC’s

• find underlying cause

• increase ventilations (and then decrease gas)

• notify dr

  • can turn life threatening very quickly

ventricular tachycardia

• multiple vpc’s in arow

v- tach causes

• same as pvc

• very bad cardiac output

v-tach tx

• lidocaine drip/cri

v-fib

usually a terminal rhythm

v-fib tx

• defibrillation

• cpr

asystole

• animal must be dead for 3-5 min before you will ever see this

sinus tachycardia

• increased heart rate

• rhythm is regular

• yes to all systemic approach questions

• results in increased workload of heart muscle

sinus tachycardia tx

• deepen animal

sinus bradycardia

• decreased heart rate

• rhythm is regular

• yes to all systemic approach questions

• results in decreased CO

sinus bradycardia tx

• ± change anesthetic plane

• anticholinergic

atrial ventricular blocks

either a delay in or block of conduction between SA node and AV node

1st degree AV block

• delay in conduction between atrium and ventricle

• be aware of them, but are not a significant problem

2nd degree AV block

• some impulses between atrium and ventricle are blocked

• not life threatening yet

3rd degree AV block

• have more than one lone p wave in consecutive sessions

• life threatening condition

t waves normal

should be no more than 25% height of r wave

abnormalities with t waves

• spiked = hyperkalemia

• broadened + heightened = myocardial hypoxiaabno

abnormal t wave interventions

• ventilate pt

• ± decrease anesthetic gasmali

malignant hyperthermia

• not very common

• a genetic disorder will have increased muscle activity leading to hyperthermia (under anesthesia)

causes of hypothermia

• decreased muscle activity

• decrease in overall metabolic rate

• introduction of cold anesthetic gas into alveolar sacs

• surgical preparation of pt

• opening up body cavity

ways to prevent hypothermia

• always keep something between pt and table

• use a circulating water blanket

• use bair hugger

• warm IV fluids

consequences of hypothermia > 96 F

no physiologic damage

consequences of hypothermia 90-94 F

decrease in anesthetic requirements

consequences of hypothermia 82-86 F

medically induced coma- no anesthetic requirements