Monitoring devices

multiparameter machine

What is perfusion

circulation of blood thru tissues

List the order of the cardiac circulation

• deoxygenated blood → body → vena cava → RA →Tricuspid valve → RV → Pulmonic valve → Pulmonary artery → Lungs (O₂ gained) → Pulmonary veins → LA → Mitral valve → LV → Aortic valve → Aorta → Body

Understand and be able to explain this formula: CO = SV X HR

CO: amount of blood heart pumps in one minute

• cannot be measured directly → pulse, or BP

SV: amount of blood pumped by one ventricle per beat

HR: number of beats per minute

How can we increase CO

↑ HR and SV

• but if HR too high → heart having less time to fill b/w beats → ↓ SV

What is it called when there is a fast HR

tachycardia

How do you increase stroke volume?

• stronger contractions

• more blood in heart

• increasing heart space by giving fluids

What is the reaction of the body/CO = SV X HR when experiencing dehydration?

• ↓ preload (blood filling heart) → less stretch → ↓ SV = ↓ CO

• body response is increasing HR

Arteries, veins, and arterioles

Arteries: elastic tissue, stretch and snap back

Veins: thin walls, huge capacity to hold blood

Arterioles: smooth muscle, relax and contract

Understand and be able to explain this formula: BP = CO x SVR

SVR: systemic vascular resistance, amount of resistance blood flow encounters

CO: amount of blood pumped by heart per minute

What can affect systemic vascular resistance SVR

• Diameter of blood vessels : ↑ SVR → ↑ Resistance → Narrow vessels = vasoconstrict

• length

• viscosity : how think blood is → polycythemia= ↑ SVR

What changes in the short-term in SVR

diameter of blood vessels

What will the body do to shift blood to important organs?

vasoconstrict to less important organs (toes/fingers) and direct blood to lungs, liver, brain, kidneys

What is expected for the blood pressure to happen during anesthesia

expected to be lower due to anesthetic drugs

what we can do to affect CO

increase or Decrease HR or SV

↑CO

• Atropine → ↑HR → CO ↑

• IV fluids → ↑ SV → CO ↑

↓ CO

• Bradycardia =↓ HR

• Dehydration = ↓ SV → ↓ CO.

What can we do to affect BP

BP ↑

• Increase CO → Increase HR or SV.

• Increase SVR → Vasoconstriction.

BP ↓

• Decrease CO or SVR.

• Propofol, acepromazine, inhalants = Vasodilation → ↓ SVR → ↓ BP.

what can we do to affect SV

SV ↑

• Give IV fluids → ↑ preload

SV ↓

• Dehydration → ↓ Preload → ↓ SV

• Blood loss → ↓ Preload → ↓ SV

What can we do to affect SVR

SVR ↑

• Vasoconstrict → ↑ SVR. ex. Dexmedetomidine, xylazine

SVR ↓

• Vasodilation → ↓ SVR. ex. Propofol, acepromazine, inhalants

what does hypotension mean and what are the causes? drugs related?

means low BP. causes from

• drugs: inhalants, acepromazine, propofol, ACE inhibitors

• blood loss (hypovolemia)

• dehydration

What is dose dependent hypotension and how does that relate to how you would administer anesthesia?

the higher the dose of anesthetic drug the more BP to decrease

• give lowest effective dose anesthesia and adjust to maintain anesthesic depth

• Too much anesthesia → Vasodilation → SVR ↓ → BP ↓ (hypotension).

What is anticipated in surgery with excessive bleeding?

• lower BP

• pale MM (vasoconstrict)

• tachycardia b/c heart making up for blood loss

Hypertension

not common under anesthesia, caused b/c of

• too light, feeling pain, fear

• vasoconstriction → dexmedetomidine = bradycardia, hypothermia

What would you expect to happen if an animal was too deep under anesthesia?

• Central eye position

• Pupil dilated

• Loss of all reflexes

• HR ↓ (bradycardia).

• BP ↓ (hypotension).

What would you expect to happen if an animal was too light under anesthesia?

• Tense jaw tone

• Central eye position

• Normal pupil size

• HR ↑ (tachycardia).

• BP ↑ (hypertension).

What color mm would you expect to see with vasoconstriction and vasodilation? what are their causes

Vasoconstriction: pale mm

• Impairs peripheral perfusion

• hypothermia

• hyperventilation

Vasodilation: pink or red mm

• improves peripheral

• hypotension

• hyperthermia

What are some actions you can take in response to hypotension in surgery?

We can reduce anesthetic depth to increase BP

give fluids to preload ↑ → SV ↑ → CO ↑ → BP may increase

control blood loss using suction or cautery to stop bleeding

Blood pressure monitoring and what do systolic and diastolic measure?

allows numeric assessment of diastolic, systolic, and mean arterial pressure (MAP), measured in MMhg

• Systolic : pressure in blood vessels when heart beats

• diastolic : pressure in blood vessels when heart rests

What are the normal systolic, diastolic and MAP ranges

1. Systolic normal range is 110-160 MM of mercury

2. Diastolic normal range 60-90 MM of mercury.

3. Mean arterial pressure (MAP) normal range is 85-120 MM of mercury

What is the general guidelines regarding systolic and MAP

• systolic has to be greater than 180 MMHG

• minimally acceptable is MAP 60

What are types of blood pressure measurement devices?

1. Direct arterial line

2. doppler → ultrasound waves by transducer detect motion of arterial wall, only gets systolic reading, cuff

3. oscillometric → measure oscillations within a cuff bladder and able to obtain MAP, cuff

How do you measure a BP cuff? How will the readings be affected if you choose the incorrect size?

40% of limb in dogs and 30% in cats

• too large= falsely lower BP

• too small = falsely higher BP

What are the three areas of a normal ECG

• P wave: atrial depolarization → triggers atria contraction

• QRS wave: ventricular depolarization → triggers ventricular contraction

• T wave: ventricular recovery

What is the meaning of sinus, supraventricular, ventricular, premature

• Sinus - comes from SA node

• Supraventricular - comes from above the SA node where QRS normal

• Ventricular - comes from ventricle where QRS abnormal (wide and bizzare)

• Premature - comes early

What is the difference between SA node and AV node

SA node is the pacemaker of the heart starting electrical impulse

AV node stimulates contractions

Electrocardiograph ECG

measures electrical impulses of heart muscle and help detect arrhythmias

• can give false signals if pt is not responding and not best info for quality of beat

which leads go where and which lead we typically use in surgery

(think snow and grass are at ground, Christmas at the end of year) pt always in R lateral recumbency

• White: right forelimb

• Green : right hindlimb

• Black : left forlimb

• Red : left hindlimb

There are 6 lead ECG but LEAD II used as main lead to read ECG

What are the two types of conductions

1. conductive gel (U/S gel) - does not dry out

2. Alcohol - cooling, need to reapply

Cardiac arrhythmias -

Normal sinus rhythm

Cardiac arrhythmias -

Sinus arrhythmia

normal in dogs not in cats

• HR speeds up on inspiration

Cardiac arrhythmias -

Sinus bradycardia

• slow HR but all p,t, and qrs waves normal equal

Cardiac arrhythmias -

Ventricular Premature complexes VPCS

abnormal beats coming from ventricular myocardium

• not usually treated

• “wide and bizarre” QRS

Cardiac arrhythmias -

1st degree AV block

conduction thru AV node delayed

• PR interval prolonged

Cardiac arrhythmias -

2nd degree AV block

no QRS wave

• disruption of AV nodal conduction

Cardiac arrhythmias -

3rd-degree AV block

P and QRS are independent

What conditions can cause bradycardia?

• anesthetic depth → too deep

• hyperkalemia

• hypothermia

• drugs → opioids, a 2 agonist

• vagal tone

What conditions can cause tachycardia?

• drugs → atropine

• anesthetic depth → too light

• pain

• hypoxia

• hypercapnia

What is the vagal tone? What are changes in vagal tone? Two reflexes?

the activity of the vagus nerve, key component of PNS

• increase tone= lower HR

• decrease tone= high HR

1. oculovagal and carotid

What is meant by vasovagal? which type are dogs prone?

there is a drop in HR and BP in response to excitement

• brachycephalic and athletic dogs - high vagal tone

What is the result of hard intubation

result in a vagal response

Two types of catherters

1. over-the-needle catheter

2. through-the-needle catheter

Which type of monitoring is most critical

respiratory monitoring

Type of monitor -

Apnea monitor

located b/w ET tube and breathing circuit and it measures the lapse time in seconds since the previous breath

• one sound for normal breathing and a different sound for absence of breathing

• alarm sounds different if exceeding 10 secs

Type of monitor -

Pulse oximetry

measures HR and oxygen saturation, % of hemoglobin that carries oxygen

• light passes thru arterial bed and measures if hemoglobin is saturated with oxygen

• place oximetry in hairless minimally pigmented area like tongue, ear

• >95% but desire of >98%

What does pulse oximetry need, when would you not have one

Needs a pulsatile arterial bed

• during faint pulse

• drug like dexmedatomdine → vasoconstriction → decre peripheral blood flow

What causes inaccurate pulse ox

vasoconstriction, occlusion of pulsatile arterial bed or dark pigmented skin

What is the relationship between SPO2 and HR

they both need to match, if HR does not match SPO2 (peripheral oxygen saturation) then sensor is incorrect

Type of monitoring -

Capnometry

measures level of CO2 (waste product) in pt’s exhaled breath or ETCO2

• normal ETCO2 = 35-45 mmHg

• also used to confirm ET tube placement/ CPR compressions

What stimulates breathing?

CO2 drives respiration NOT the lack of O2

What is hypoventilation, what would CO2 do?

breathing too slowly or shallowly in which CO2 not being exhaled → buildup in blood

• CO2 will increase and have a ETCO2 = 60

• causes: narcotic OD, CNS dysfunction, heavy sedation

What can cause hypercapnia

hypoventilation → hypercapnia (result of too much CO2), ETCO2=60

• apnea - propofol and alfaxone → ↓ Respiratory drive

• expiratory one-way valve (flutter valve)

• CO2 absorber exhausted

• dead space

What is hyperventilation and how would CO2 look like?

breathing too fast or too deeply, removes too much CO2 from body,

• CO2 ↓, ETCO2 = 25

• leads to hypocapnia

What causes hypocapnia? And actions to take?

hyperventilation → hypocapnia

• panting

• esophageal intubation

Give breaths , asses anesthetic depth , check CO2 absorber

SCENARIO

An animal is hyperventilating under anesthesia

The technicians gives breath, but instead of giving deep breaths, she gives multiple shallow breaths

The animal stops breathing

Why?

experiences hypocapnia → decrease CO2 (its main driver for respiration) → causing apea (stop breathing)

• making ETCO2 low = 25

What is the difference b/w mainstream and sidestream capnometry?

MAINSTREAM

• quicker results but adds dead space, measure directly, EMMA

SIDESTREAM

• removes gas from circuit but problem w smaller pt, has a lag time and moisture from condensation

What is happening in this graph

the pt is rebreathing CO2

• causes: flowmeter too low, malfunction flutter valve, or exhausted CO2 absorber

What is the meaning of the CO2 capnometry wave

There is presence of a leak

• causes: leaky ET cuff

• artificial airway too small for pt

Meaning of this wave

“shark fin” obstruction in airway

• causes: airway kinked, presence of foreign body, obstruction, or bronchospasm

What are the three types of deadspace and what contributes it

• Anatomic - involves upper airway structures that do not participate in gas exchange → nasal passagess, larynx, trachea

• Alveolar - Alveoli receive ventilation but w little or no blood flow (perfusion) → ineffective gas exchange.

• Mechanical

Mainstream

What two types of make up physiologic dead space ?

anatomic and alveolar dead space

• these do not particpate in CO2 or O2 exchange

Mechanical dead space, what can contribute to increasing this? how to reduce ?

it is the space in a breathing circuit where both inhalation and exhalation passes thru common path, like oxygen mask or pt monitor adaptors or Et tubes extending beyond the incisors.

• makes pt possibly inhale unfiltered exhaled gas

• Exhausted CO2 absorber or malfunctioning one-way valves

• never 0

Reduce by minimizing # of connectors to tube, do not use face mask, pt < 6 kg Mechanical dead space refers to the volume within a breathing circuit where inhaled and exhaled gases mix, which can lead to rebreathing of exhaled gases. To reduce mechanical dead space, one can minimize the number of connectors in the tubing system, avoid using face masks, and ensure appropriate equipment for small patients.

What makes up total deadspace

anatomic, alveolar, and mechanical