DH DeForge, VMD
Fellow of the Academy of Veterinary Dentistry
Pre-Anesthesia Examination
Animal Anesthesia
and
The Oral Care
Patient--Blog #19
Pre-Anesthesia Examination and Testing Requisites-ACVA
Monitoring Guidelines-ASA Patient Status Classification
Companion animal
advocates are very concerned when the pet that they love needs to undergo general
inhalation anesthesia for any reason.
To assist the pet advocate, this abstract
will review Pre-Anesthesia Examination and Testing; ACVA Anesthesia Monitoring
Guidelines; and ASA Pre-Anesthesia Physical Status Classification.
f veterinary preoperative medical assessment and human preoperative assessment
are identical. The goal of exam and
testing is to reduce the patient’s surgical and anesthetic peri-operative
morbidity or mortality, and to return the patient to normal functioning and a
pain free quality of life as quickly as possible.
It is imperative to realize that anesthesia
risk and recovery from anesthesia risk is multi-factorial and a function of the
preoperative medical condition of the patient; the invasiveness of the surgical
procedure; and the type of anesthetic administered.
A history and
physical examination is critical with emphasis on risk factors for cardiac and
pulmonary complications. Laboratory
investigations must be ordered based on the patient’s age; medical status; drug
therapy; or the nature of the proposed procedure.
Those veterinary
patients with co-morbidity should be optimized for the procedure. Proper consultations with appropriate medical
specialists should be scheduled to improve the patient’s health prior to
anesthesia if indicated.
These consultations
should ideally not be done in a "last second" fashion. The
pre-operative preparation involves procedures that are implemented based on the
nature of the expected operation as well as the findings of the diagnostic
workup and the pre-operative evaluation.
The referring
doctor-LDVM-RDVM-GDVM-can spear head and complete all exams and testing or refer to
a specialist for that testing.
Listed below are
many of the tests that your family doctor or Specialist may order based on the age of the
patient; pre-existing medical health of the patient; and/or other factors noted
in past Medical Records.
It is critical
to know if any patient referred has had any adverse history with anesthesia,
sedation, and/or analgesic medicines in the past.
Pre-Anesthesia
Testing Modules
[
} Physical Exam
[ ] Comprehensive Chemistry Profile and
CBC
[ ] Urinalysis
[ ] Feline
Leukemia-Immunodeficiency-and Bartonella Testing at National Veterinary Lab
[ ] CardioPet proBNP / Feline *
[ ] IDEXX SDMA Biomarker for Kidney
Function (IDEXX Adult Wellness
[ ] Blood Pressure
[ ] Coagulation Testing [PT/PTT/BMBT]
[ ] Electrocardiogram
[ ] Chest Radiology
[ ] Echocardiogram
[ ] Abdominal Sonogram
[ ] Internal Medicine Consult and
Pre-Anesthesia Testing
[ ] Cardiologist Consult
ACVA Monitoring Guidelines Update
Recommendations for monitoring
anesthetized veterinary patients
Position
Statement 2009
The American College of Veterinary
Anesthesiologists (ACVA) has revised the set of guidelines for anesthetic
monitoring that were originally developed in 1994 and published in 19951. Since then many factors have caused a shift
in the benchmark used to measure a successful anesthetic outcome, moving from
the lack of anesthetic mortality toward decreased anesthetic morbidity.
This shift toward minimizing
anesthetic morbidity has been facilitated by more objective definition and
earlier detection of pathophysiologic conditions such as hypotension, hypoxemia
and severe hypercapnia. This has resulted from the incorporation of newer
monitoring modalities by skilled attentive personnel during anesthesia.
The ACVA recognizes that it is
possible to adequately monitor and manage anesthetized patients without
specialized equipment and that some of these modalities may be impractical in
certain clinical settings. Furthermore, the ACVA does not suggest that using
any or all the modalities will ensure any specific patient outcome, or that
failure to use them will result in poor outcome.
However, as the standard of veterinary care
advances and client expectations expand, revised guidelines are necessary to
reflect the importance of vigilant monitoring. The goal of the ACVA guidelines
is to improve the level of anesthesia care for veterinary patients. Frequent
and continuous monitoring and recording of vital signs in the peri-anesthetic
period by trained personnel and the intelligent use of various monitors are
requirements for advancing the quality of anesthesia care of veterinary
patients.
1. JAVMA 1995; 206(7): 936-937.
Circulation
Objective:
to ensure adequate circulatory function.
Methods:
1) Palpation of
peripheral pulse to determine rate, rhythm and quality, and evaluation of
mucous membrane (MM) color and capillary refill time (CRT).
2) Auscultation
of heart beat (stethoscope; esophageal stethoscope or other audible heart
monitor). Continuous (audible heart or pulse monitor) or intermittent
monitoring of the heart rate and rhythm.
3) Pulse
oximetry to determine the % hemoglobin saturation.
4) Electrocardiogram
(ECG) continuous display for detection of arrhythmias.
5) Blood
pressure:
a. Non-invasive
(indirect): oscillometric method: Doppler ultrasonic flow detector
b. Invasive
(direct): arterial catheter connected to an aneroid manometer or to a
transducer and oscilloscope.
Recommendations:
Continuous awareness of heart rate and rhythm
during anesthesia, along with gross assessment of peripheral perfusion (pulse
quality, mm color and CRT) are mandatory. Arterial blood pressure and ECG
should also be monitored. There may be some situations where these may be
temporarily impractical, e.g. movement of an anesthetized patient to a
different area of the hospital.
Oxygenation
Objective:
to ensure adequate oxygenation of the patient’s arterial blood.
Methods:
(1)
Pulse oximetry (non-invasive estimation of hemoglobin saturation).
(2)
Arterial blood gas analysis for oxygen partial pressure (PaO2).
Recommendations:
Assessment of oxygenation should be done
whenever possible by pulse oximetry, with blood gas analysis being employed
when necessary for more critically ill patients.
Ventilation
Objective:
to ensure that the patient’s ventilation is adequately maintained.
Methods:
(1)
Observation of thoracic wall movement or observation of breathing bag movement
when thoracic wall movement cannot be assessed.
(2)
Auscultation of breath sounds with an external stethoscope, an esophageal
stethoscope, or an audible respiratory monitor.
(3)
Capnography (end-expired CO2 measurement).
(4)
Arterial blood gas analysis for carbon dioxide partial pressure (PaCO2).
(5)
Respirometry (tidal volume measurement).
Recommendations:
Qualitative assessment of ventilation is
essential as outlined in either 1 or 2 above, and capnography is recommended,
with blood gas analysis as necessary.
Temperature
Objective:
to ensure that patients do not encounter serious deviations from normal body
temperature.
Methods:
(1)
Rectal thermometer for intermittent measurement.
(2)
Rectal or esophageal temperature probe for continuous measurement.
Recommendations:
Temperature should be measured periodically
during anesthesia and recovery and if possible checked within a few hours after
return to the wards.
Neuromuscular Blockade
Objective:
to assess the intensity of and recovery from neuromuscular blockade.
Methods:
(1) Hand-held peripheral nerve stimulator.
(2) Spirometer.
Recommendations
For any patient in which neuromuscular blockade
is used, it is essential to control ventilation, monitor closely for signs of
awareness, and be certain of recovery of blockade prior to anesthesia recovery.
Recovery of neuromuscular function may be assumed if the evoked response
(twitch and/or tetanic fade) to a nerve stimulus, and respiratory tidal volume
as measured with a spirometer, return to at least 70% of pre- blockade status.
End tidal CO2 may also be used as an indication of adequate
ventilation in spontaneously ventilating patients.
Record
Keeping
Objectives:
(1) To maintain a legal record of significant
events related to the anesthetic period.
(2) To enhance recognition of significant trends
or unusual values for physiologic parameters and allow assessment of the
response to intervention.
Recommendations:
(1) Record all drugs administered to each
patient in the peri-anesthetic period and in early recovery, noting the dose,
time, and route of administration, as well as any adverse reaction to a drug or
drug combination.
(2) Record monitored variables on a regular
basis (minimum every 5 to 10 minutes) during anesthesia. The minimum variables
that should be recorded are heart rate and respiratory rate, as well as
oxygenation status and blood pressure if these were monitored.
(3) Record heart rate, respiratory rate, and
temperature in the early recovery phase.
(4) Any untoward events or unusual circumstances
should be recorded for legal reasons, and for reference should the patient
require anesthesia in the future.
Recovery
period
Objective:
to ensure a safe and comfortable recovery from anesthesia.
Methods:
(1) Observation of respiratory pattern.
(2) Observation of mucous membrane color and
CRT.
(3) Palpation of pulse rate and quality.
(4) Measurement of body temperature, with
appropriate warming or cooling methods applied if indicated.
(5) Observation of any behavior that indicates
pain, with appropriate pharmaceutical intervention as necessary.
(6) Other measurements as indicated by patient’s
medical status, e.g. blood glucose, pulse oximetry, PCV, TP, blood gases, etc.
Recommendations
Monitoring in recovery should include at the minimum evaluation of pulse rate
and quality, mucous membrane color, respiratory pattern, signs of pain, and
temperature.
Personnel
Objective:
to ensure that a responsible individual is aware of the patient's status at all
times during anesthesia and recovery, and is prepared either to intervene when
indicated, or to alert the veterinarian in charge about changes in the patient's
condition.
Recommendations:
(1) Ideally, a
veterinarian, technician, or other responsible person should remain with the
patient continuously and be dedicated to that patient only
(2) If this is not possible, a reliable and
knowledgeable person should check the patient's status on a regular basis (at
least every 5 minutes) during anesthesia and recovery
(3) A responsible
person may be present in the same room, although not necessarily solely
occupied with the anesthetized patient (for instance, the surgeon may also be
responsible for overseeing anesthesia)
(4) In either of
(2) or (3) above, audible heart and respiratory monitors must be available.
(5) A responsible
person, solely dedicated to managing and caring for the anesthetized patient
during anesthesia, remains with the patient continuously until the end of the
anesthetic period.(a, b)
a) Recommended for
all patients assessed as ASA status III, IV, or V
b) Recommended for
horses anesthetized with inhalation anesthetics and/or horses anesthetized for
longer than 45 minutes
ASA Patient Status:
The American Society of Anesthesiologists has developed a
classification system for human patient physical status. This system has been
widely adapted to veterinary patients. It is important to recognize that the
ASA status is not equal to patient risk classification, although a correlation
does exist between physical status and outcome. Some additional risk factors
that do not contribute to ASA status, but that do contribute to patient
outcome, include anesthetist experience, surgeon experience, facilities and
availability of monitoring and emergency care, and performance of anesthesia
outside normal hours.
ASA I--- A normal healthy patient
ASA II--- A patient with mild systemic disease
ASA III--- A patient with severe systemic
disease
ASA IV--- A patient with severe systemic disease
that is a constant threat to life
ASA V--- A moribund patient who is not expected
to survive without the operation
Questions:
email DonDeForge100@gmail.com
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