monitoring anesthesia guidelines detailed

Monitoring Anesthesia

Guidelines Detailed organized from the

2011 AAHA Guidelines for

Anesthesia Monitoring

Ken Crump, AAS, AHT

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Monitoring AnesthesiaReference: 2011 AAHA Guidelines

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2011 AAHA Guidelines Suggestions for Monitoring Anesthetized Patients

• Electrocardiogram (ECG) • Pulse oximeter (SpO2) • Arterial blood pressure monitor

– Direct intra-arterial BP: Most accurate, but technically difficult to perform

– Noninvasive BP (Doppler or oscillometric monitor):

• Technically easy, but can be inaccurate.

• Evaluate trends in conjunction with other patient parameters.

• Select cuff width of 40–50% of circumference of limb.

• Thermometer: – Esophageal probe or periodic

rectal temperature with conventional thermometer

• Anesthetic gas analyzer:– Measures inspired and expired inhalant

concentration

• Capnometer/capnograph:– Measures and/or displays CO2 in expired and

inspired gas, and respiratory rate

• Physical observations – Visualization (e.g., eye position, mucous

membranes, chest excursion, blood loss, bag volume, and movement with ventilation, equipment function)

– Palpation (e.g., pulse quality, jaw tone, palpebral reflex)

– Auscultation (heart, lungs): Precordial or esophageal stethoscope

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2011 AAHA Guidelines Suggest

• Electrocardiogram (ECG)

• Pulse oximeter (SpO2) • Arterial blood pressure monitor









concentration







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Pulse Oximeter (SpO2)

• Indicates the % oxygen saturation of hemoglobin– Can be PCV dependent

• Highly positional• “Pulse” is more

trustworthy than “Oximeter”

• It tells you that the heart is responding to the electrical activity– It displays a pulse wave

• Don’t trust the numbers without a wave form– Pulse oximeters that only

display a number are very unreliable. You need to see a wave form to interpret the number

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Pulse Oximeter (SpO2)

The biggest problem with Pulse Oximeters

• Their readings are most often believed when they are good, and ignored when they are bad.

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• Electrocardiogram (ECG) • Pulse oximeter (SpO2)

• Arterial blood pressure monitor – Direct intra-arterial BP: Most

accurate, but technically difficult to perform








concentration







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Blood Pressure Monitor

The goal of monitoring blood pressure is to maintain a mean

arterial pressure (MAP) of 60mmHg to assure adequate

perfusion of vital organsSystolic = amount of pressure in the arteries during contraction of the heartDiastolic = amount of pressure in the arteries between heart beatsMean = average (mean) pressure in the arteries during one cardiac cycleCalculating the MAP = [(Systolic – Diastolic) / 3 ]+ Diastolic

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Blood Pressure Monitor

Dorsal pedal arterial catheterization

Direct intra-arterial blood pressure monitor• Most accurate• Advanced

technique• Technically difficult

to achieveNote: Pressure transducers are expensive – there is another less expensive way

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Blood Pressure MonitorIndirect Blood Pressure• Technically easy to achieve• Not very accurate in animals• Best to monitor trends

Doppler• Reads only systolic arterial

pressure (SAP)• You estimate MAP based on SAP• Be concerned when SAP is below

90 mmHg• Cuff width 40-50% circumference

of limb• Can be very positional

Oscillometric• Reads only MAP• Displays SAP, MAP, and DAP• Cuff width 40-50% circumference

of limb• Can be very positional

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concentration







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Monitoring Temperature

Thermometer:

• Use esophageal or rectal probe to monitor continuously

• Take rectal temperature with conventional thermometer periodically

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Hypothermia occurs in more than 80% of anesthetized cats and dogs.

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Hypothermia Contributors:• Small body size• Drug-altered

peripheral perfusion• Intubation bypasses

the nose• Breathing cold gases• Radiated heat loss

from skin surface• Open body cavities• Water during

dentistry

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Peri-Anesthetic Hypothermia

A review of the survival rates of Yorkshire Terriers after portosystemic shunt surgery showed the single most prognostic indicator for survival was postoperative temperature.

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Each stage of a procedure presents different hypothermia challenges…

• Premedication

• Clip and Prep

• Surgery

• Recovery

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3-step solution to hypothermia

1. Pre-warming

Prevents initial 1o – 2oF heat loss

2. Warm inspired gases

Prevents 2o – 5oF loss during clip and prep

3. Warm air blankets

Porous blanket / low air flow traps heat, warms animals

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concentration







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Capnometer / Capnograph

• Measures / displays CO2 in expired / inspired gas

• Measures respiratory rate

• Reliable– More reliable than

SpO2

• Informative– Many inferences can

be made based on CO2

• If I could only have one monitor, it would be CO2

Go to Making Anesthesia Easier blog post “Why Monitor CO2?”

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Why Monitor CO2

End-tidal CO2 monitoring is a valuable non-invasive, low risk assessment tool for the anesthetist.

• It tells you if the endotracheal tube is in the trachea

• Indicates changes in cardiac output

• Detects– Extubation– Disconnection– Cardiac arrest

• (faster than SPO2)• (faster than ECG)

• Useful to assess effectiveness of CPR Respiration rate

• Detects inspired CO2– Dead space– Circuit misfit (resistance)

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Why Monitor CO2

• Indicates ventilation status (hypo/hyper-ventilation)– Breathing is about getting rid

of CO2

– Ventilation is defined by levels of CO2

– Normal ETCO2 levels are 35-45 mmHg.

– Normal healthy animals can tolerate levels up to 60-70 mmHg• Mild hypercapnia drives the

cardiovascular system

• Hold Your Breath!– Experience mild hypercapnia

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concentration







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Anesthetic Gas Analyzer

• Measures inspired and expired inhalant gas concentration

• Fun– Allows for deeper

understanding of oxygen / gas delivery

• Who has one of these, anyway?

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concentration







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The Vet Tech Anesthetist

AAHA Guidelines:Successful anesthetic management requires trained, observant team members who understand:• Anesthesia drugs and their

effects• How to use anesthetic and

monitoring equipment• What is normal and abnormal

in a patient’s response to anesthesia

• How to react to abnormal responses effectively

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And…

• Heart rate• Respiration rate• Pulse quality• Response to surgical

stimulation• Status of the surgical

procedure• [Sometimes while answering the

phone, recovering patients, folding laundry, pre-medding the next patient, tying in surgeons, opening packs, wrapping packs, wishing you’d brought lunch…]

• Reflexes– Palpebral– Swallow– Pedal– Corneal– Laryngeal

• Jaw Tone• Eye Position• Pupillary Light Response

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Post Op / Recovery

Slow Down!A fast extubation rarely leads to a quality recovery. Emergence from general anesthesia is best when it's gradual.• Do NOT reverse drugs to

hasten extubation.• Allow the patient to gradually

emerge from general anesthesia, keeping pain relieving drugs intact.

• Often the drugs you want to reverse are of the most value to the patient at that time.

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Post Op / Recovery

We are all watching the clock and trying to get to our next case. And you can't leave your patient until it's extubated. But a comfortable emergence from general anesthesia is the beginning of a smooth recovery.• Finish the anesthetic record while

you sit with the patient.• Take the patient with you to your

next case, and monitor extubationfrom there

• Plan emergence and extubation of your next patient before the surgery is over– This is a call-back to "Know the

procedure" during your preanesthetic evaluation.

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