Transcript blood pressure - Dr. Roberta Dev Anand

MONITORING ANIMALS WITH THE USE OF
INSTRUMENTATION
These machines can be very useful, especially in the
situations where the technician can’t always be
with the patient through the entire procedure;
however you should never completely rely on
your machines
The following can be monitored via machines: Blood
pressure, Central Venous Pressure, Blood Gases,
Pulse Oximetry, Capnography, and
Electrocardiography
EKG
 Measures the electrical activity of the heart – NOT
the mechanical activity.

REMEMBER THAT THE EKG CAN CONTINUE EVEN IF
YOUR PATIENT’S HEART IS NOT CONTRACTING. This is
called electromechanical dissociation.
 The complexes should be of normal configuration,
consistent size, rate, and rhythm
 If the complexes look abnormal:



Alert the Dr.
Check the patient!
Check the lead placement
EKG
Cardiac arrhythmia is any pattern of electrical
activity that differs from the healthy, awake
animal
MOST COMMON EKG ABNORMALITIES SEEN WHICH
MUST BE ADDRESSED are:
 1)Sinus Tachycardia
 Diagnosed when a patient’s HR under anesthesia is:
>200 bpm in cat
>180 bpm in small dog
> 160 bpm in large dog
EKG: SINUS TACHYCARDIA
 Causes:
 Can be drug-related (atropine, ketamine), or
response to surgical stimulation


If animal is also “huffing”, during surgery
if reflex activity is present or moving occurs, it may be too “light”

Can also occur in situations of hypoxia (early),
hypotension, or high CO2 levels

Pre-existing conditions of the heart, thyroid, anemia,
shock

Emergency treatment can include applying
pressure to the eyeballs
EKG:SINUS BRADYCARDIA
 2) Sinus Bradycardia
 Diagnosed when patient’s HR under anesthesia is:
< 60 bpm in large dog
<70 bpm in small dog
< 100 bpm in a cat
 Causes:


Can be drug related (xylazine, medetomidine, opiods)
Increased anesthetic depth, hypoxia (late stages),
hypothermia
 Treatment:
 Can give reversal agents or atropine
 Assess other parameters before deciding management
EKG: HEART BLOCKS
 3) AV Heart Blocks
 Electrical impulse through the heart is not being
transmitted efficiently.

1st Degree: There is a P wave for every QRS complex, but
the P-QRS interval is prolonged

2nd Degree: Some P waves are not followed by QRS
complexes

3rd Degree: The atria and ventricles are contracting
independently. No normal relationship between P waves
and QRS complexes
EKG:HEART BLOCKS

2nd and 3rd degree blocks can be seen after alpha-2agonist administration, high vagal tone, and some
other conditions
 4) Ventricular premature contractions (VPCs)
 Impulse arising from the ventricular muscle
causing an uncoordinated heart contraction
 QRS complexes are wide and bizarre
 Also caused by hypoxia, heart disease or trauma,
electrolyte abnormalities, etc
 Epinephrine release can stimulate the formation of
VPCs

Don’t forcibly restrain an animal during the induction of
anesthesia!
EKG: VENTRICULAR TACHYCARDIA
 Ventricular Tachycardia: > 3 VPCs in a row,
more than 15 in one minute, or VPCs +
falling blood pressure


EMERGENCY!!
Can be treated with Lidocaine given IV
EKG:FIBRILLATION
 Fibrillation
 Contraction of small muscle bundles within the
atria or ventricles


Atrial fibrillation
 No p-waves, high HR, normal QRS complexes
Ventricular fibrillation
 Absence of QRS complexes
 CARDIAC ARREST IS IMMINENT
ECG: Atrial Fibrillation
BLOOD PRESSURE
 Refers to arterial blood pressure
 Systolic Pressure – produced by the contraction of
the ventricles as it propels blood through the aorta,
pulmonary artery, and other major arteries
 Diastolic Pressure – the pressure that remains when
the heart is resting between contractions.
 Mean Arterial Pressure (MAP) - average pressure
through the cardiac cycle and best indicator of
organ perfusion under anesthesia
= diastolic pressure + (systolic-diastolic pressures)
3
BLOOD PRESSURE
 Pulse pressure – pressure detected by manual
palpation
 the difference between systolic and diastolic
pressure
 Blood pressure can vary with age, breed, species,
and instrumentation
 It is important to monitor TRENDS in blood
pressure in addition to actual values
BLOOD PRESSURE
 Normal systolic BP in awake dogs and cats:120
 Normal range 90-150 mm Hg
 Should ideally remain at or above 90 mm Hg in
anesthetized patients
 Normal diastolic BP in awake dogs and cats: 80
 Normal range = 50-90 mm Hg
 Normal MAP: 90-100 mm Hg
-Should be maintained above 60 mm Hg in
anesthetized patients
- This is the best indicator of blood perfusion to
the internal organs
BLOOD PRESSURE MONITORING
 INDIRECT BP MONITORING
 Method most commonly used in private practice
 Noninvasive, less technically difficult than direct
monitoring
 2 types of monitors:

DOPPLER – determines SYSTOLIC PRESSURE ONLY by
detecting the echo of RBCs passing through an artery


Probe is placed on the leg or tail of an animal and a cuff is used to
compress an artery and then detect the pressure at which blood
flow resumes
OSCILLOMETRIC – determines, systolic, diastolic, and MAP
by detecting the oscillations within the cuff caused by
the pulsation of the artery beneath the cuff
INDIRECT BP MONITOR: OSCILLOMETRIC
INDIRECT BP MONITOR: OSCILLOMETRIC
Less labor intensive than Doppler
monitors but tend to be less consistent
in their ability to register blood
pressures for smaller patients
 Set to automatically cycle every 2 to 3
minutes
-1 minute cycles tend to create an ischemic

challenge to the extremity
INDIRECT BP MONITOR: OSCILLOMETRIC
 Cuff width should be 30%-50% of limb
circumference for dogs and cats
-Excessively wide cuffs will lead to an under-estimation of blood
pressure
-Excessively narrow cuffs will lead to an over-estimation of blood
pressure
 Location of cuff is important
-Most consistent cuff location for small patients is the midforeleg, tailbase
-Don’t hesitate to try all locations as needed
-Good locations for larger animals include metacarpus, metatarsus,
and distal tibia just above tarsus
INDIRECT BP MONITOR: DOPPLER
-More consistently effective when monitoring small
patients
-Measures systolic pressure only
-Hair is clipped at the probe site
-The depression in the probe must be filled
with ultrasound gel
-Once you hear the swishing sound, tape the
probe in place
-Both excessive and inadequate pressure can
create difficulties measuring accurately
INDIRECT BP MONITOR: DOPPLER
-It is often possible to obtain readings by first wetting the site with
alcohol, then applying coupling gel to the site and the probe without
clipping any hair
-The cuff is placed just proximal to the probe
-Cuff width is as important with doppler BP measurement as with
oscillometric BP measurement
-Cuff width should be 30-50% of limb circumference for dogs
-Excessively wide cuffs will lead to an underestimation of blood
pressure
-Excessively narrow cuffs will lead to an overestimation of blood
pressure
-5 readings are taken, the highest and lowest are
thrown out. The average of the other 3 are used to
determine the SAP.
http://www.youtube.com/wa
tch?v=Li4oGhfKmDQ
http://www.vasg.or
g/doppler_use.htm
DIRECT BP MONITORING
 Used less than indirect methods in private practice
 Indwelling catheter is placed in femoral or dorsal
pedal artery
 Catheter is connected to a manometer or pressure
transducer via a fluid-filled tubing and the pressure is
displayed
http://www.vasg.org/direct_arterial_pressures.htm
WHAT CAN I DO IF THE BLOOD PRESSURE IS TOO
LOW?
 Check the patient!
 Decrease the inhalant anesthetic setting
 Increase the IV fluid flow rate (check with the Dr. first of
course)
 Check the cuff to ensure proper placement/positioning
 Location
 Selection: cuff size should be 30-50% of the circumference of
the selected location. So, hold the cuff up to the desired
location and turn it sideways – it should go roughly halfway
around the limb or tail.
 Finally…. Hetastarch, Dopamine, Dobutamine ….to be used in
emergencies!
CENTRAL VENOUS PRESSURE
 -Measurement of the blood pressure in a central vein
-anterior vena cava
 -Assesses how well the blood is returning to the
heart and the ability of the heart to receive and
pump blood
 -Helpful in monitoring animals with right sided
heart failure and preventing overhydration in
animals receiving IV fluids
CENTRAL VENOUS PRESSURE
www.dcavm.org/08techmar.html
http://books.google.com/books?id=LtGS0t1MIskC&pg=
PA410&lpg=PA410&dq=manometer+veterinary+medici
ne&source=web&ots=BIOCQL_14Z&sig=MZnEtUSN6v
pdi4TTnNjYkAduva4&hl=en&sa=X&oi=book_result&r
esnum=9&ct=result#PPA410,M1
BLOOD GASES
Refers to measurement of blood pH and dissolved
oxygen and carbon dioxide gas in arterial or
venous blood.
 -Indicate how well the patient is obtaining
oxygen and delivering it to the tissues and
how well the lungs are expelling carbon
dioxide
 -All of these depend on the respiratory function of
the patient.
BLOOD GASES
OXYGEN
 OXYGEN EXISTS IN 2 FORMS IN THE BLOOD:
 Free molecule dissolved in plasma (PaO2)
 Measured by a blood gas analyzer
 Values below 60 mm Hg indicate hypoxia!!
 To treat: supplement oxygen, assist ventilation

Chemically combined with hemoglobin in RBCs (SaO2 or SpO2)
 Measured by a pulse oximeter
 Values below 90% indicate hypoxia!!
 To treat: supplement oxygen, assist ventilation
BLOOD GAS ANALYZER
 Not commonly used in private practice
 Blood sample should be taken from an artery
 Sample is placed on ice and should be run within 2
hours of collection
PULSE OXIMETER
 Inexpensive, noninvasive, portable, easy to use
 Clip is placed on a thin strip of tissue that is
nonpigmented and hairless
 Most commonly the tongue, but can also use the
pinna, rectal mucosa, toe webbing, lip, vulvar
fold, Achilles tendon, under base of tail
PULSE OXIMETER
 Values should ideally read 97% or greater under
anesthesia
 Animals that are not anesthetized can also be
connected to a pulse oximeter
 Used during emergencies in animals with respiratory
distress.
BLOOD GASES: CARBON DIOXIDE
 PaCO2 = The portion of carbon dioxide that is
dissolved in plasma (Carbon dioxide partial pressure
in the arteries)
 Blood gas analyzers tell how well the patient is
eliminating CO2
 An awake patient’s levels are usually less than 45 mm
Hg. It is common to see levels of 45-60 mm Hg in an
anesthetized patient because the animal doesn’t
breathe deeply enough to eliminate the usual amount
of CO2
 If greater than 60 mm Hg, hypoventilation is present.
Assess other parameters to determine oxygenation and assist
ventilation if necessary
CARBON DIOXIDE
 Carbon dioxide build-up can result in respiratory
acidosis
 Commonly seen levels are 7.2-7.3 as compared to normal
values of 7.35-7.45
 Blood pH is measured via blood gas analyzers
CAPNOGRAPHY
 A capnometer is placed on the
endotracheal tube: it monitors the
amount of CO2 that is expired
 Noninvasive
 Info is displayed as a graph
CAPNOGRAPHY
 Measure End Tidal CO2
 As inspiration occurs, CO2 should be around zero
 Hypercapnea = ET CO2 greater than 55 mm Hg
 CO2 canister needs changing, hypoventilation (should
correct when patient is bagged)
 Hypocapnea = ET CO2 less than 35 mm Hg
 Tachypnea, dead space, too much assisted ventilation,
improper endotracheal tube placement/connection
Correcting Blood Gas Abnormalities
 The main reason for a low SpO2 in an anesthetized patient
is decreased ventilation
 1) The animal is not breathing well and you need to assist
it
 Respiratory rate should be 8 – 20 breaths /min for the
average patient (avg = 10-12 bpm). Small patient may
need more breaths. You can ventilate the patient
by closing the pop – off valve, squeezing the bag
to inflate the lungs. NEVER SQUEEZE THE BAG
TO MORE THAN 20 cm H20!!!
 Try just occasional breaths at first – the more breaths
you give, the less the patient’s brain will stimulate
the patient to breathe on it’s own. Use the patient
and the pulse ox as a guide.
Correcting Blood Gas Abnormalities

2) The patient has ventilation/perfusion mismatch – the oxygen
isn’t getting to the areas in the lungs where the blood is
 Check that the machine is hooked up properly
 Check that the oxygen is turned on/in tank
 Check that the endotracheal tube is placed correctly and the cuff
is properly inflated. If the tube is in too far, the gas/O2 will
only go to one side of the lungs.

3) The patient’s pulse is weak


Check that the patient isn’t too deep
Check the blood pressure and act accordingly (see
section on blood pressure)
Correcting Blood Gas Abnormalities

4) The sensor is slipping off the patient

5) The sensor has been at one location for a long time and is too dry
or is pinching off blood supply to the area. The following locations
may be used for the pulse ox. probe: tongue, lips, ear, toe webbing,
prepuce, and vulva.

6) The patient may have a preexisting lung disease

7) Bradycardia or severe arrhythmias