MONITORING WITH INSTRUMENTATION

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Monitoring with Instrumentation
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• MONITORING ANIMALS WITH THE USE OF
  INSTRUMENTATION
• These machines can be very useful, especially in
  the situations where the technician cant 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

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EKG

• Measures the electrical activity of the heart
  NOT the mechanical activity.
• REMEMBER THAT THE EKG CAN CONTINUE EVEN IF YOUR
  PATIENTS 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

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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 patients HR under anesthesia
  is gt200 bpm in cat
• gt180 bpm in small dog
• gt 160 bpm in large dog

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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

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EKGSINUS BRADYCARDIA

• 2) Sinus Bradycardia
• Diagnosed when patients HR under anesthesia is
• lt 60 bpm in large dog
• lt70 bpm in small dog
• lt 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

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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

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EKGHEART BLOCKS

• 2nd and 3rd degree blocks can be seen after
  alpha-2-agonist administration, high vagal tone,
  and some other conditions

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• 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
• Dont forcibly restrain an animal during the
  induction of anesthesia!

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EKG VENTRICULAR TACHYCARDIA

• Ventricular Tachycardia gt 3 VPCs in a row, more
  than 15 in one minute, or VPCs falling blood
  pressure
• EMERGENCY!!
• Can be treated with Lidocaine given IV

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EKGFIBRILLATION

• 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
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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

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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

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BLOOD PRESSURE

• Normal systolic BP in awake dogs and cats120
• 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

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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

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INDIRECT BP MONITOR OSCILLOMETRIC
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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

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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 mid-foreleg, tailbase
• -Dont hesitate to try all locations as needed
• -Good locations for larger animals include
  metacarpus, metatarsus, and distal tibia just
  above tarsus

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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

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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.

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http//www.youtube.com/watch?vLi4oGhfKmDQ
http//www.vasg.org/doppler_use.htm
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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

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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!

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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

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CENTRAL VENOUS PRESSURE

• www.dcavm.org/08techmar.html
• http//books.google.com/books?idLtGS0t1MIskCpgP
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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.

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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

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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

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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

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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.

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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 patients 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
  doesnt 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

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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

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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

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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

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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 patients brain
  will stimulate the patient to breathe on its
  own. Use the patient and the pulse ox as a
  guide.

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Correcting Blood Gas Abnormalities

• 2) The patient has ventilation/perfusion mismatch
  the oxygen isnt 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 patients pulse is weak
• Check that the patient isnt too deep
• Check the blood pressure and act accordingly (see
  section on blood pressure)

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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