5. Anesthetic Monitoring

1Copyright © 2011, 2003, 2000, 1994 by Mosby, Inc., an affiliate of Elsevier Inc.

To keep the patient safe and to regulate anesthetic depth

Anesthetic Monitoring

Chapter 5


Monitoring Parameters

Vital signs Homeostatic mechanism’s response to anesthesia Heart rate Heart rhythm Respiratory rate and depth Mucous membrane color Capillary refill time Pulse strength Blood pressure Body temperature

Best indicator of patient wellbeing


Monitoring Parameters (Cont’d)

Reflexes Involuntary response to stimulus Palpebral, corneal, pedal, swallowing, laryngeal,

and papillary light reflexes Indicators of anesthetic depth

Parameters offer predictable responses to anesthesia at various depths

May be affected by drugs, disease, or individual response variation

Monitor anesthetized patients as often as possible; continuously is ideal


Stages and Planes of Anesthesia

Four stages (I, II, III, IV) Stage III divided into four planes From stage I through stage IV there is a

progressive decrease in pain perception, motor coordination, consciousness, reflex responses, muscle tone, and cardiopulmonary function


Stage I

Period of voluntary movement Patient begins to lose consciousness Characterized by:

Fear, excitement, disorientation, struggling, urination, defecation

Increased heart rate and respiratory rate Stage ends with loss of ability to stand and

recumbency


Stage II

Period of involuntary movement; the “excitement stage”

Characterized by: Breathing irregular Vocalization, struggling, paddling Increased heart and respiratory rate, pupils

dilated, muscle tone marked, reflexes present Actions are not under conscious control Stage ends with muscle relaxation,

decreased respiratory rate, and decreased reflex activity


Stage III

Period of surgical anesthesia Divided into four planes Plane 1: not adequate for surgery:

Regular respiratory pattern, no involuntary limb movements

Eyeballs start to rotate ventrally, pupils partially constricted, decreased pupillary light reflex

Endotracheal tube may be passed and connected to gas anesthetic machine

Other reflexes are still present but decreased response


Stage III Plane 2

Suitable depth for most surgical procedures Characterized by:

Regular and shallow respiration with decreased rate

Blood pressure and heart rate mildly decreased Relaxed muscle tone Pedal and swallowing reflexes are absent Ventromedial eye rotation


Stage III Plane 2 (Cont’d)

Surgical stimulation may produce: Mild increase in heart rate, blood pressure, or

respiratory rate Patient remains unconscious and immobile Pupillary light response is sluggish; pupil size is

moderate


Stage III Plane 3

Deep anesthesia—excessive for most procedures

Characterized by: Low heart and respiratory rates, decreased tidal

volume Reduced pulse strength Increased capillary refill time (CRT) Poor to absent papillary light reflex; central

eyeballs; moderately dilated pupils Reflexes are totally absent; muscle tone is very

relaxed


Stage III Plane 4

Early anesthesia overdose Characterized by:

Abdominal breathing Fully dilated pupils; dry eyes All reflexes are absent Marked depression of the cardiovascular system,

pale mucous membranes, increased CRT Flaccid muscle tone


Stage IV

Period of anesthetic overdose Characterized by:

Cessation of respiration Circulatory collapse Death

Resuscitate immediately to save the patient


Stage III in 3 Planes

Alternative classification Plane 1: “light” surgical anesthesia

Not suitable for surgery Plane 2: “medium” surgical anesthesia

Optimum depth for most surgical procedures Plane 3: “deep” surgical anesthesia

Excessive depth


Objectives of Surgical Anesthesia

Patient doesn’t move Patient isn’t aware Patient doesn’t feel pain Patient has no memory of the procedure


Monitoring Patient Safety

Assess vital signs Physical

• Touch, hearing, vision Mechanical instruments

• Electrocardiogram• Blood pressure monitor• Capnograph• Doppler blood flow monitor• Pulse oximeter


Monitoring Patient Safety (Cont’d)

Vital signs groupings Circulation

• Heart rate and rhythm, pulse strength, CRT, mucous membrane color, blood pressure

Oxygenation• Mucous membrane color, CRT, hemoglobin saturation,

inspired oxygen, arterial blood oxygen Ventilation

• Respiratory rate and depth, breath sounds, end-expired carbon dioxide levels, arterial carbon dioxide, blood pH


Indicators of Circulation

To ensure adequate circulatory function “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.” ACVA Guidelines 2009


Indicators of Circulation: Heart Rate

Physical assessment Palpation of apical pulse through the thoracic wall Palpation of the peripheral pulse Auscultation with stethoscope: more difficult in

recumbent, anesthetized animals Mechanical assessment

ECG machine Blood pressure monitor

• Doppler blood flow detector or oscillometric monitor Intraarterial line and transducer


Indicators of Circulation: Heart Rate (Cont’d)

Bradycardia Depressant effect of most anesthetics Alpha2-agonists and opioids Excessive anesthesia depth Adverse effects of drugs


Indicators of Circulation: Heart Rate (Cont’d)

Tachycardia Anticholinergics and cyclohexamines Inadequate anesthetic depth Pain Hypotension Blood loss and shock Hypoxemia and hypercapnea


Indicators of Circulation: Heart Rhythm

Assessed along with heart rate Normal sinus rhythm vs. sinus arrhythmia

Both can be seen in anesthetized animals First- or second-degree heart block

Use ECG to detect Causes of arrhythmias

Drugs• Anticholinergics, alpha2-agonists, barbiturates, cyclohexamines

Medical states or diseases• Hypoxia, hypercarbia, heart disease, trauma, gastric dilatation-

volvulus


Instruments Used to Monitor Heart Rate and Rhythm

Esophageal stethoscope Thin flexible catheter attached to audio monitor or

conventional stethoscope Electronically amplifies heart sounds Inserted into esophagus to level of the fifth rib and adjusted

for maximum sound Electrocardiography

A graphic representation of the electrical activity of the heart Used to detect arrhythmias, which are common in

anesthetized animals Differentiate normal from abnormal and dangerous from

harmless rhythms


Esophageal Stethoscope


Cardiac Conduction System


ECG Pattern of Waveforms, Intervals, and Segments


Commonly Encountered Cardiac Arrhythmias

Sinus arrhythmia (SA) Heart rate coordinated with respirations Decreases during expiration Increases during inspiration Normal in dogs, horses, and cattle Abnormal in cats


Commonly Encountered Cardiac Arrhythmias (Cont’d)

Sinus bradycardia Abnormally slow heart rate Common during anesthesia: excessive anesthetic

depth and drug reactions Correct with reversal agents or anticholinergics

Sinus tachycardia Abnormally fast heart rate Inadequate anesthetic depth, drug reactions,

surgical stimulation Treat according to cause


Sinus Arrhythmia



A-V heart block Delay or interruption of electrical impulse

conduction through the A-V node First-degree A-V heart block

Prolonged P-R interval Second-degree A-V heart block

Occasional missing QRS complexes Third-degree A-V heart block

Atrial and ventricular contractions occur independently

Randomly irregular P-R intervals


First-, Second-, and Third-Degree A-V Heart Blocks



Premature complexes: complexes that occur too early

Supraventricular premature complexes (SPC) One or more normal QRS complexes closely

following the previous QRS complex


Supraventricular Tachycardia

A series of three or more SPCs in a row


Ventricular Premature Complexes (VPC)

One or more wide, bizarre QRS complexes closely following the previous QRS complex


Ventricular Tachycardia

A series of three or more VPCs in a row


Fibrillation

Chaotic, uncoordinated small muscle bundle contractions within the artria and ventricles

Atrial fibrillation Fine undulating baseline Absence of P-waves Tachycardia Normal QRS complexes at irregular intervals


Ventricular Fibrillation

Undulating baseline Absence of QRS complexes


Pulseless Electrical Activity (PEA)

Cessation of heart contractions and/or palpable pulse in the presence of normal or nearly normal ECG Associated with cardiac arrest, the mechanical

activity of the heart ECG measures the electrical activity of the heart Anesthetist must do both physical monitoring and

ECG monitoring


Indicators of Circulation: Capillary Refill Time (CRT)

Rate of color return to oral mucous membrane after application of gentle digital pressure Indicates peripheral tissue blood perfusion >2 seconds is prolonged and indicates poor

perfusion May result from epinephrine release, low blood

pressure, hypothermia, cardiac failure, excessive anesthetic depth, blood loss, shock

Results in reduced temperature of affected part(s)


Indicators of Circulation: Blood Pressure (BP)

Force exerted by flowing blood on arterial walls

Evaluates tissue perfusion during anesthesia Factors involved:

Heart rate Stroke volume Vascular resistanceArterial compliance (elasticity) Blood volume

Varies throughout cardiac cycle Hypotension vs. hypertension


Measuring Blood Pressure

Systolic pressure Produced by contraction of the left ventricle All BP monitoring instruments can measure

systolic pressure Diastolic pressure

Pressure that remains in the arteries when the heart is in the resting phase between contractions

Not all BP monitoring instruments can measure diastolic pressure


Measuring Blood Pressure (Cont’d)

Mean arterial pressure (MAP) Average pressure through the cardiac cycle Best indicator of blood perfusion to internal organs A mathematical calculation


Indicators of Circulation: Pulse Strength

Used as a rough indicator of blood pressure Determined by the difference between

systolic and diastolic blood pressure, vessel diameter, and other factors

Palpate the peripheral artery Lingual, dorsal pedal, femoral, carotid, facial, aural Different arteries are appropriate for different

species Lowered in anesthetized animals A subjective interpretation


Blood Pressure Monitors

Direct Reading obtained via indwelling catheter inserted

into an artery (facial or aural) and attached to a pressure transducer and monitor

Most commonly used in equine practices and research facilities

Provides continuous reading throughout the cardiac cycle

Most accurate


Blood Pressure Monitors (Cont’d)

Indirect Reading is obtained by using an external sensor

and cuff Most commonly used in general veterinary

practices Noninvasive; cuff is placed over appropriate

superficial artery Doppler and oscillometric methods Sphygmomanometer


Central Venous Pressure

Blood pressure in a large central vein (anterior vena cava) Assess blood return to the heart and heart function,

especially right-sided heart failure A direct method of measurement

Catheter from the jugular vein into the anterior vena cava Connected to a water manometer

• >12-15 cm H2O considered elevated Monitor trends over time rather than single readings

May detect overhydration when administering IV fluids


Indicators of Oxygenation

To ensure adequate oxygenation of the patient’s arterial blood “Assessment of oxygenation should be done

whenever possible by pulse oximetry, with blood gas analysis being employed when necessary for more critically ill patients.” ACVA Guidelines 2009


Indicators of Oxygenation: Mucous Membrane Color

Assessed by observing the gingiva Varies from patient to patient Evaluate prior to each procedure to determine

baseline for patient Rough assessment of oxygenation and tissue

perfusion Alternate sites: tongue, conjunctiva of lower

eyelid, mucous membrane lining of prepuce or vulva


Indicators of Oxygenation: Mucous Membrane Color (Cont’d)

Pale mucous membranes: blood loss, anemia, poor capillary perfusion

Cyanotic membranes (blue to purple): respiratory arrest, oxygen deprivation, pulmonary disease

Affected by: body temperature, vascular resistance, gum disease


Physiology of Oxygen Transport

Adequate oxygen necessary for metabolic processes

Components of total oxygen content Free, unbound oxygen molecules dissolved in

plasma (minor content) Oxygen chemically bound to hemoglobin in

erythrocytes (four binding sites/hemoglobin molecule)

Most oxygen is carried by hemoglobin 100% saturation: all available hemoglobin binding

sites are filled with oxygen


Indicators of Oxygenation: Measuring Blood Oxygen

Calculated oxygen content Measures both bound and dissolved oxygen An accurate measurement expressed as mL/dL (CaO2) = (Hb × 1.39 × SaO2/100) + (PaO2 × 0.003)

Partial pressure (PaO2) (N = 80-120 mm Hg arterial blood) Measures unbound oxygen dissolved in plasma (N

= ~1.5% total content) Expressed as mm Hg and varies in arterial,

capillary, or venous blood Highest in arterial blood; lowest in venous blood


Indicators of Oxygenation: Measuring Blood Oxygen (Cont’d)

Percent oxygen saturation (percent SaO2) Percentage of total number of available

hemoglobin binding sites occupied by oxygen molecules (N =>97% total content)

Varies in arterial, capillary, or venous blood Highest in arterial blood; lowest in venous blood


Partial Pressure and Oxygen Saturation

A nonlinear direct relationship As one decreases so does the other, but not at the

same rate As partial pressure decreases the oxygen

saturation also decreases, but not as rapidly Indicates oxygen availability in animals with

normal hemoglobin levels


Partial Pressure and Oxygen Saturation (Cont’d)

Patient with low hemoglobin (one cause of anemia) Neither parameter gives an accurate indication of oxygen

availability Both parameters may be normal Insufficient hemoglobin is available to carry all the oxygen

necessary Patient is breathing pure oxygen from anesthetic

machine Amount of dissolved oxygen will increase, not the percent

saturation Marginally affects the total oxygen content of blood


Measuring Partial Pressure and Oxygen Saturation

Blood gas analyzers measure partial pressure

Pulse oximeters measure oxygen saturation PaO2 and SaO2 are elevated in anesthetized

patients breathing pure oxygen Low PaO2 and SaO2 observed during

anesthesia can indicate hypoxemia and the need for oxygen supplementation or assisted ventilation


Pulse Oximeter

Measures the saturation of hemoglobin and the heart rate

Red and infrared wavelength light technology with digital readout >95% saturation normal in patient breathing pure oxygen <90-95% saturation: patient is hypoxemic <90% saturation: therapy is required <85% saturation for >30 seconds: medical emergency

Also used on nonanesthetized animals in intensive care


Pulse Oximeter Use

Two types of probes: transmission or reflective

Transmission probes Clothes pin configuration

• One jaw light source, one jaw sensor Applied over nonpigmented tissue, relatively

hairless and thin enough to transmit light• Tongue, pinna, toe web, vulvar fold, prepuce, Achilles

tendon, lip Light passes through the tissue and is measured

by the sensor


Pulse Oximeter Use (Cont’d)

Reflective probes Light source and sensor are located next to each

other Placed in a hollow organ—esophagus or rectum Light is reflected off tissue and is measured by the

sensor


Pulse Oximeter with Transmission Lingual Probe


Pulse Oximeter Probes and Placement Locations


Low Pulse Oximeter Readings

Incorrect instrument use Anesthetic agent causes vasoconstriction Inadequate tissue perfusion Inadequate oxygen delivery to patient Inadequate ventilation Inadequate circulation


Indicators of Ventilation

To ensure that the patient’s ventilation is adequately maintained “Qualitative assessment of ventilation is essential

as outlined for either (1) Observation of thoracic wall movement or observation of breathing bag movement when thoracic wall movement cannot be assessed. Or (2) Auscultation of breath sounds with an external stethoscope, an esophageal stethoscope, or an audible respiratory monitor; and capnography is recommended with blood gas analysis as necessary.”ACVA Guidelines 2009


Ventilation vs. Respiration

Ventilation: movement of gas in and out of the alveoli

Respiration: processes by which oxygen is supplied to and used by the tissues and carbon dioxide is eliminated from the tissues


Indicators of Ventilation: Respiratory Rate (RR)

Number of breaths per minute (bpm) Monitored visually by watching chest wall

movements or movements of reservoir bag Monitored mechanically with apnea monitor or

capnograph Normally decreases during anesthesia

Tachypnea May be caused by hypercapnea, pulmonary

disease, or mild surgical stimulus May indicate a progression from moderate to light

anesthesia during recovery


Indicators of Ventilation: Tidal Volume (VT)

The amount of air inhaled during a breath Monitored visually by watching chest wall

movements or movements of reservoir bag Monitored mechanically with respirometer Hypoventilation

Subnormal tidal volume or shallow breathing Can lead to atelectasis Reversed by gentle bagging

Hyperventilation: elevated tidal volume Can result from hypercapnea or surgical

stimulation


Indicators of Ventilation: Respiratory Character

The effort required to breathe Monitored visually by watching the chest wall

movements Measure time relationship between inspiration and

expiration Monitor by auscultating the chest

Listen for harsh noises, whistles, or squeaks Dyspnea: labored or difficult breathing Apneustic respiratory pattern

Prolonged pause between inspiration and expiration


Apnea Monitor

Monitors respirations Warns anesthetist if patient hasn’t taken a

breath in a preset time period Detects temperature differences between

inspired air (cool) and expired air (warm) Sensor placed between endotracheal tube

connector and breathing circuit


Apnea Monitor (Cont’d)


Indicators of Ventilation: Capnograph

End-tidal carbon dioxide monitor (ETCO2) Measures the carbon dioxide in air that is inhaled

and exhaled Value closely mirrors arterial CO2 (PaCO2)

Mainstream capnograph: sensor placed directly between the endotracheal tube and breathing circuit

Sidestream capnograph: sensor located in a computerized monitor; air is pulled in through a tube attached to the fitting between the endotracheal tube and breathing circuit


Capnograph


Capnogram

Waveform of carbon dioxide levels passing through the capnograph Normal shape is a modified rectangle

Inspiration = CO2 is 0 mm Hg Duration of 0 mm Hg reading is baseline

Expiration = CO2 is 35-45 mm Hg Increases slightly until end of expiratory effort Abruptly returns to baseline at beginning of inspiration

“End-tidal” monitor CO2 value at end of expiration most reflective of arterial CO2

levels


Capnogram (Cont’d)


Interpretation of a Capnogram

Abnormal CO2 levels are most commonly due to ventilation changes

Must evaluate Baseline value ETCO2 value Waveform shape Rate of change


Capnogram Abnormalities Related to Ventilation or Equipment Problems

Hyperventilation Gradual decrease in ETCO2 value

Hypoventilation Gradual increase in ETCO2 value

Flat line (No waveform) Lack of carbon dioxide reaching sensor or machine

malfunction Elevated baseline

Patient is rebreathing carbon dioxide or the sensor is contaminated

Rounding of edges of waveform Leaking cuff or partially kinked endotracheal tube


Capnogram Abnormalities Unrelated to Ventilation or Equipment Problems

Cardiac arrest Rapid loss of waveform that returns if CPCR is successful

Hypotension or sudden decrease in cardiac output Rapid decrease in height of rectangle

Hypothermia Gradual decrease in ETCO2 value (short rectangle)

Hyperthermia Gradual increase in ETCO2 value (tall rectangle)

Subtle waveform changes


Indicators of Ventilation: Blood Gas Analysis

Blood pH Dissolved oxygen and carbon dioxide gas in

arterial blood (PaO2 and PaCO2) or Dissolved oxygen and carbon dioxide gas in

venous blood (PvO2 and PvCO2) Indicator of oxygenation, ventilation, acid-

base status Influenced by respiratory function

Rate, depth, and character


Carbon Dioxide Transport

Bound to hemoglobin: 20-30% Dissolved in plasma: 5-10% Converted to bicarbonate and hydrogen ions

by reaction with water: 60-70% Evaluate patient CO2 elimination by

measuring PaCO2 Normal PaCO2 =<45 mm Hg in an awake patient Often normally elevated during anesthesia:

45-60 mm Hg Hypoventilation PaCO2 =>60 mm Hg


Carbon Dioxide Levels and Acid-Base Status

Anesthetized patients may become mildly acidotic Higher CO2 levels produce higher hydrogen ion

concentration Blood pH will be lower (7.20-7.30)

Correct the underlying cause to correct the acidosis Compare blood pH and PaCO2 levels to determine

if acidosis is metabolic or respiratory


PaO2

Partial pressure of dissolved oxygen in arterial blood Should be five times the inspired oxygen

concentration Room air is ~21% oxygen so PaO2 should be

~100 mm Hg Pure oxygen is 100% oxygen so PaO2 should be

500 mm Hg Hypoxemia in the absence of disease

Rarely seen in anesthetized small animals or ruminants

Commonly seen in anesthetized horses


Indicators of Body Temperature

To ensure that patients do not encounter serious deviations from normal body temperature “Temperature should be measured periodically

during anesthesia and recovery and if possible checked within a few hours after return to the wards.” ACVA Guidelines 2009


Indicators of Body Temperature: Core Body Temperature

A vital sign regulated by thermoregulation Controlled by the hypothalamus Shivering, metabolic rate, and peripheral blood flow keep

temperature in the normal range Is not an indicator of circulation, oxygenation, or ventilation

Monitor every 15-30 minutes during anesthesia Rectal thermometer Esophageal or rectal probe with monitor

Anesthesia most often decreases body temperature


Body Temperature Loss During Anesthesia

Influencing factors Shaving and skin preparation Lack of shivering or muscular activities Decreased metabolic rate Opened body cavity and exposed viscera Vasodilation caused by preanesthetic and

anesthetic drugs Age: pediatric and geriatric animals are more

predisposed Size: small patients lose heat faster Temperature of IV fluids Use of nonrebreathing systems


Body Temperature Loss Complications During Anesthesia

Prolonged anesthetic recovery Reduced anesthetic dose to maintain surgical

anesthesia Predispose patient to anesthetic overdose Shivering during recovery will increase

oxygen demands CNS depression and heart malfunction


Minimize or Manage Heat Loss During Anesthesia

Avoid cold prep, surgery, and treatment rooms

Barrier between patient and table top Warm IV fluids to ~100° C (37.5° F) Circulating warm water blanket Forced warm air blanket Warm water bottles Infrared heating lamps Warmed fluids for abdominal cavity flush Avoid heating pads


Hyperthermia During Anesthesia

Influencing factors Excess external heat administration Drug-induced reactions Patient cannot dissipate heat

Most often seen during or just before recovery Management

Cold fluids IV, IP, or rectally Fans Ice or alcohol application Reversal agents Increase flow rate of oxygen in nonrebreathing systems


Malignant Hyperthermia

Most commonly seen in pigs Genetic defect

Excess muscle metabolism when using some anesthetic drugs or muscle relaxants

Can be caused by restraint Clinical signs

Patient becomes hot and stiff Ears turn red Increased carbon dioxide production Tachyarrythmias


Malignant Hyperthermia (Cont’d)

Management Stop anesthesia immediately and administer 100%

oxygen Use cooling methods Treat with dantrolene


Assessment of Anesthetic Depth

To make sure the patient is at a depth that provides immobility, unconsciousness, and lack of awareness of pain while avoiding conditions that endanger the patient such as hypoventilation, hypoxemia, hypotension, and hypothermia.


Assessment of Anesthetic Depth: Reflexes

An unconscious response to a stimulus Conscious animals and protective reflexes Decreased reflexes to stage III, plane 3 level

anesthesia (when there are few to none) Reflexes evaluated

Swallowing, laryngeal, pedal, palpebral, corneal, papillary light reflex

Reported as present, decreased, or absent


Swallowing Reflex

A normal response to food or saliva in the pharynx

Monitored by viewing the ventral neck region Present in light surgical anesthesia Lost in medium surgical anesthesia Returns just before the patient regains

consciousness Used to determine when to pull the

endotracheal tube


Laryngeal Reflex

Epiglottis and vocal cords close immediately when larynx is touched by an object

Prevents tracheal aspiration Observed during intubation if animal is in the

light plane of anesthesia Makes intubation difficult

Especially in cats, pigs, and small ruminants May cause laryngospasm in cats, pigs, and

small ruminants


Palpebral Reflex

The blink reflex in response to a light tap on the medial or lateral canthus

May be elicited by lightly stroking the hairs of the upper eyelid

Present in light anesthesia Often lost during medium anesthesia, although the

exact point varies Slow palpebral response in horses indicates

adequate surgical anesthetic depth Ruminants tend to have a slightly stronger reflex than

horses


Palpebral Reflex (Cont’d)


Pedal Reflex

Flexion or withdrawal of limb in response to squeezing, twisting, or pinching a digit or pad

Used in small animals only Varies from subtle muscle contraction to full

withdrawal of limb Varies with depth of anesthesia

Present in light anesthesia Absent in medium anesthesia

Requires a high intensity stimulus


Pedal Reflex (Cont’d)


Corneal Reflex

Retraction of eyeball within orbit and/or a blink in response to corneal stimulation

Touch the cornea with a drop of sterile saline or artificial tears

Most useful in large animals; difficult to elicit in small animals

Present in light and medium anesthesia; absent in deep or excessive anesthesia

Used primarily to determine if a LA patient is too deep


Corneal Reflex (Cont’d)


Pupillary Light Reflex (PLR)

Constriction of pupils in response to bright light shined on one retina

Present in light and medium anesthesia; absent in deep anesthesia

Dazzle reflex Blink response to bright light shined on retinas Same significance as PLR Lost very early in anesthesia


Other Indicators of Anesthetic Depth

Spontaneous movement Muscle tone Eye position Pupil size Nystagmus Salivary and lacrimal secretions Heart and respiratory rates Response to surgical stimulation


Indicators of Anesthetic Depth


Indicators of Anesthetic Depth (Cont’d)


Judging Anesthetic Depth

Monitor as many variables as possible No one piece of information is reliable by

itself Each animal will respond in its own unique

way to anesthesia


Recording Information During Anesthesia

Objective:“To maintain a legal record of significant events related to the anesthetic period.To enhance recognition of significant trends or unusual values for physiologic parameters and allow assessment of the response to intervention.”ACVA Guidelines 2009


Recording Information During Anesthesia (Cont’d)

Recommendations:“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.” ACVA Guidelines 2009



Recommendations:“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.” ACVA Guidelines 2009



Recommendations:“Record heart rate, respiratory rate, and temperature in the early recovery phase.Any untoward events or unusual circumstances should be recorded for legal reasons, and for reference should the patient require anesthesia in the future.” ACVA Guidelines 2009


Anesthesia Record


Completed Anesthetic Record

Documents

5. Anesthetic Monitoring