Monitoring during Anesthesia Flashcards
1
Q
What do you need to know?
A
what is normal
how old is the patient?
species?
what drugs did the patient recieve?
what is the procedure?
what is normal for this specific patient?
2
Q
what do we monitor?
A
CNS
CVS
respiratory
renal
temperature
other? -case dependent
3
Q
CNS monitoring
A
- need to maintain good anesthetic depth
- check for reflexes:
- eye (palpebral, corneal, nystagmus, lacrimation)
- jaw tone
- anal reflex
- pedal reflex
- EEG and other monitoring not used regularly
4
Q
evaluating plane of anesthesia:
A
- species and individual variations
- position of eye
- movement
- muscle tone
- certain reflexes
- response to surgical stimulation
- nystagmus (usually in horse)
- shivering (light)
- eye reflexes present
5
Q
light plane of anesthesia
A
- central eye position
- cessation of limb movements
- muscle tone remains
- response to surgical stimulation (either movement or breathing/hemodynamic response)
- nystagmus (horse)
- eye reflexes present
- shivering
- moist cornea
6
Q
medium plane of anesthesia (goal)
A
- no spontaneous movement
- no reflex movement
- no change in hemodynamic or breathing in response to surgical stimulation
- moderate muscle tone
- decrease in tidal volume
- no palpebral reflex
- no shivering
- ventromedial rotation of the eye
- small pupil aperture
- moist corneas
7
Q
deep plane of anesthesia
A
- decrease in tidal volume
- abdominal breathing may be noted
- eyes fixed centrally
- no pedal reflexes
- no spontaneous or reflex movement
- bradycardia/hypotension and worsening of hemodynamic function
- no palpebral and corneal reflex
- dilated pupil
- dry cornea (dead…)
8
Q
CV monitoring
A
maintain perfusion to body organs and maintain a normal rhythm and rate
use clinical skills as well as specific equipment to monitor HR, BP, etc
9
Q
evaluating mucous membranes
A
- pale pink/pink: normal
- white/pale: anemia, vasoconstriction, lack of circulating fluid
- cyanosis: lung disease, decrease in oxygen flow to the breathing circuit, endobronchial intubation
- red/bright pink: hypercapnia
10
Q
evaluating CRT
A
- the time it takes for blood flow back into the capillary bed after it is manually compressed with a digit of the anesthetist
- may be deceptive in determining peripheral perfusion: may refill from engorged veins as well as arteries
- normal < 1-2 seconds
11
Q
evaluation of pulse
A
- information about the rate, rhythm and pulse quality
- subjective
- SA: lingual, femoral and digital
- LA: facial, transverse facial, digital arteries
12
Q
equipment/techniques used to monitor CVS
A
- esophageal stethoscope
- ECG
- BP monitoring
- pulse ox
- central venous pressure
- urine output
13
Q
esophageal stethoscope
A
- blind-ended tube that is passed into the esophagus at the level of the heart and is connected to ear pieces to which you can listen to
- can evaluate rhythm, rate
- cannot evaluate adequacy of circulation
- can be annoying to the anesthetist
14
Q
ECG
A
- electrical activity of the heart
- heart rate and rhythm
- not good for evaluation cardiac function or disease
-
placement of leads
-
LA-lead I
- RA-right jugular farrow
- LA- ventral midline under heart apex
- RL- any site remote from heart
-
LA-lead II
- RA-right elbow
- LA-left elbow
- LL-left stifle or abdomen
-
LA-lead I
15
Q
common arrhythmias
A
sinus tachycardia
sinus bradycardia
second degree AV block
VPCs
16
Q
normal HR for different species:
A
dog 70-140
cat 110-140
horse 30-45
cattle 60-80
sheep 70-130
goat 90-160
17
Q
BP monitoring
A
- maintain adequate perfusion to the vital organs
- a mean BP should be maintained above 60 mmHg (70 in horses)
- two methods:
- direct
- indirect
18
Q
direct BP
A
- provides real time beat by beat pressure monitoring
- invasive: place an arterial catheter which is connected to tubing then to a pressure transducer
- aseptic technique when placing arterial lines
- hematoma formation common
-
arteries used:
- dogs: femoral, dorsal pedal
- cats: dorsal pedal, tail
- horse: facial arteries, transverse facial, great metatarsal
- cattle: middle coccygeal, median auricular
- sheep/goat: median auricular artery
19
Q
indirect BP monitoring
A
- sphymomanometry
- occlusion of artery by inflatable cuff and return of BF distally to the cuff as the pressure of the cuff is reduced
- when pressure is reduced, 1st sound heard is systolic P
- cuff measure at which BF ceases to increase with decreasing cuff P is diastolic P
- stethoscope, doppler pulse detectors
- systolic should be > 80 mmHg
20
Q
why is cuff size important when measuring BP?
A
width of cuff should be ~40 % of circumference of limb
bigger width than circumference: underestimate BP
smaller width than circumfrence: overestimate BP
too tight: underestimate
too loose: overestimate
21
Q
oscillometric method
A
- cuff is inflated to a pressure and pressure is slowly released as the monitor detects the oscillations in the cuff caused by BF under cuff
- as pressure decreases, there is an increase in BP and oscillations
- systolic: rapid increase in amplitude of oscillations
- mean: lowest cuff pressure at which maximum oscillation occurs
- diastolic: rapid decrease in oscillation after max oscillation
- MAP > 60 mmHg
22
Q
measuring cardiac output
A
- invasive method (thermodilution)
- requires special and expensive equipment
- not used routinely
- CO = SV x HR
23
Q
pulse oximetry
A
- arterial oxygen saturation
- heart rate monitoring
- placed on tongue, ears, digits
- measures light absorption of two different wavelengths at fast intervals during pulsation
- detects reduced hemoglobin and oxyhemoglobin
- sensitive to movement, cold, vasoconstriction
- should be maintained >95%
24
Q
at what percent do you consider the patient to be hypoxemic?
A
<90%
25
central venous pressure
* pressure within the **thoracic vena cava**
* **balance** **between venous blood volume and contractility of the heart**
* **decreased CVP** = hypovolemia
* **increased CVP** = fluid overload
* **normal**
* SA: 2-7 cmH2O
* LA: 15-25 cmH2O
26
urine output
* **dependent on CO, blood volume, and renal function**
* not used often in anesthesia
* need to **catheterize** in order to quanitify
* **normal 1-2 mL/kg/hr**
27
monitoring respiratory system
* maintain **oxygenation and remove CO2**
* **respiratory rate**
* **chest excursions**
* **abdominal effort**
* **tidal volume** can be subjectively evaluated based on movement of rebreathing bag and thoracic excursions
* monitor **MM color**
28
normal respiration rates
dog 10-30
cat 24-42
horse 8-15
cow 12-35
sheep 15-40
goat 15-25
pig 10-45
29
equipment/techniques for monitoring respiration
ventilometer/respirometer
blood gas analysis
capnograph
pulse ox
30
ventilometer/respirometer
measures the **tidal volume and minute volume** of the patient
normal tidal volume **10-15 mg/kg**
**creates dead space**, can accidentally extubate patient
31
blood gas analysis
measures levels of **oxygen and CO2 in arterial blood**
provides **acid-base status**
can also measure electrolytes/glucose/lactate
32
capnography
* measures the **end tidal CO2 and the inspired CO2 tension**
* connected between the **patient and the breathing system**
* provides info on: **adequacy of ventilation, CVS, patient's metabolism**
* useful to measure: **hypoventilation, hyperventilation, apnea, disconnection, rebreathing, obstruction, embolism**
33
phases of capnogram
**Phase I: inspiratory baseline**
**Phase II: expiratory upstroke**
**Phase III: expiratory plateau**
**Phase IV: inspiratory downstroke**
34
Phase I
* **inspiratory baseline**
* represents the **inspiration of fresh gas with CO2**
* the baseline should stay at the level that corresponds to **zero concentration (mmHg) of CO2**
* normal end tidal CO2 = 35-45
35
Phase 2
* **expiratory upstroke**
* occurs **shortly after the inspiration ends**
* upstroke is **caused by the rapid washing out of the fresh gas** in the anatomic space and then **replacement by CO2-rich alveolar gas**
* should be **steep**
36
Phase 3
* **expiratory plateau**
* represents **continuous exhalation**
* line will be perfectly horizontal if ventilation and perfusion were perfectly matched
* however, **ventilation and perfusion are not perfectly matched**
* this results in **CO2 slowlly increasing as the gas from the lung areas** with lower ratio of ventilation to perfusion **reaches the sampling site**
37
phase 4
* **inspiratory downstroke**
* occurs **shortly after expiration ends** and represents the **rapid washing out of the CO2 by fresh gas** as inspiration starts
* should be **steep**
38
pulse ox to monitor respiratory system
**lower oxygen tension** means **lower arterial oxygen saturation**
will also see **low saturation with pulmonary embolism**
39
body temperature
* **hypothermia and hyperthermia should be avoided**
* **thermistor/thermocouple** inserted into the **esophagus** (core temp)
* can use a **rectal** thermometer
* maintain **\>94 deg F**
* rule out malignant hyperthermia in pigs
40
anesthetic complications due to hypothermia:
decrease in anesthetic requirements
not responding to anticholinergics
prolonged recovery
cardiopulmonary depression
