question

Patient prep

answer

Don't take shortcuts Don't skip steps Incomplete patient preparation can result in life-threatening consequences

question

Selection of anesthetic protocol

answer

The list of anesthetics and adjuncts prescribed for a particular patient Includes calculated dosages, routes, and order of administration Selected by the veterinarian-in-charge Calculate, check, and recheck drug doses, oxygen flow rates, and fluid administration rates Takes into account minimum patient database, patient physical status, and procedure Modified protocol for ill, pediatric, or otherwise compromised animals

question

Minimize adverse effects of anesthesia

answer

Correct physiologic abnormalities prior to anesthesia Base the protocol on the results of the patient's minimum database Use a balanced protocol consisting of multiple agents Double-check all injectable drug doses prior to administration Label all syringes with the patient name, drug name, and drug concentration Administer no more than the minimum dose needed to achieve the desired level of anesthesia Administer all IV agents "to effect" unless told otherwise

question

General anesthesia - IM induction

answer

Anesthetic agents are administered by intramuscular (IM) injection Anesthetic depth gradually increases, peaks, and gradually decreases After injection the anesthetist has little control over the anesthesia May administer more anesthetic if adequate depth is not reached If a reversal drug is available for the anesthetic agent, it can be administered if patient is too deep

question

General anesthesia - IV injection and ultra short acting agent

answer

Technique used for short procedures <10 minutes of anesthesia Drugs: Propofol, methohexital, thiopental sodium, or etomidate Drug is given to effect Anesthetic depth increases rapidly then decreases gradually Anesthetist controls peak effect and can increase depth by administering more anesthetic agent

question

General anesthesia - TIVA and ultra short acting agent

answer

TIVA: Total intravenous anesthesia Patient is induced to effect; additional boluses are administered every 3-5 minutes as needed to maintain surgical anesthesia Short-to-moderate length noninvasive procedures Propofol is the most commonly used agent Anesthetist can increase depth but can't decrease depth if excessive

question

General anesthesia - TIVA by CRI

answer

Total intravenous anesthesia by constant rate infusion (CRI) Patient is induced to effect Anesthesia is maintained by constantly infusing small amounts of anesthesia via a syringe pump Slows down and moderates changes in depth as seen with bolus administration

question

General anesthesia - inhalant agent

answer

Not an injection technique Induction is faster than IM induction, but slower than IV induction Anesthetist has control over depth of the anesthesia; can make changes rapidly Delay between time dial setting is changed and patient depth occurs Factors that affect delay time Patient respiratory drive Agent used and carrier gas flow rate Type and volume of breathing circuit

question

General Anesthesia: IV Induction and Inhalant Maintenance

answer

Most commonly used method of inducing and maintaining anesthesia in small animals Dynamic elements of both IV and inhalant administration Rapid induction Good control over both increases and decreases in anesthetic depth Rapid recovery

question

Equipment preparation

answer

Locate, check, and prepare all equipment needed for entire anesthetic period prior to induction Intubation equipment Syringes, needles, drugs, fluids required Equipment designed to prevent hypothermia Small animal anesthetic machine • Semiclosed rebreathing system (≥2.5 to 3 kg patient weight) • Non-rebreathing system (<2.5 to 3 kg patient weight) Crash cart with emergency drugs and equipment

question

Premedication or sedation

answer

Calms the patient and prepares the patient for anesthetic induction Desired effects: Sedation, cholinergic blockade, analgesia, muscle relaxation Drugs: Tranquilizers, alpha 2-agonists, opioids, dissociatives, anticholinergics

question

Premedication or sedation (cont)

answer

After IM injection place the animal in a quiet yet accessible place Close observation until agent takes effect Stimulation or excitement may diminish the beneficial effects Induction should follow immediately after desired effects are reached

question

Anesthetic induction

answer

Patient loses consciousness and enters surgical anesthesia Take the patient from consciousness to stage III anesthesia smoothly and rapidly Intubate when possible while animal is still light IV induction is most common and takes animals through the excitement stage most rapidly Attempt to avoid the excitement/struggling stage, which is seen more often with mask induction IM induction results in smooth, gradual CNS depression with little apparent time spent in the excitement stage

question

IV induction - drugs used

answer

Mixture of equal volumes of ketamine and diazepam or midazolam Propofol Neuroleptanalgesics Thiopental sodium Etomidate Various other combinations containing dissociatives, tranquilizers, and opioids

question

IV induction (cont)

answer

Administer IV to effect (unconsciousness) Don't administer the entire calculated dose all at once Allow for individual patient response to anesthetic Premedication drugs can affect the dose of general anesthetic required Titration IV drugs given as a series of bolus injections and discontinued when desired effect is reached IV induction produces up to 10-20 minutes of anesthesia If more time is needed, anesthesia is maintained with inhalation anesthetics or administration of propofol, methohexital, or etomidate by repeat boluses or CRI

question

Inhalation induction

answer

Anesthetic induction using a facemask or induction chamber Drugs used: isoflurane and sevoflurane Low blood-gas solubility coefficient Results in rapid passage through stage II anesthesia

question

Inhalation induction - Mask

answer

Use of a facemask to induce anesthesia Requires skillful restraint to prevent patient or operator injury Don't restrict chest excursions or the airway Fit the mask prior to induction Mask obscures muzzle and eyes normally used for monitoring Need higher oxygen flow rates than with endotracheal tube

question

Inhalation induction - Mask cautions

answer

Exposes personnel to waste anesthetic gas • Need adequate room ventilation Patient struggling can lead to epinephrine release • Use only on calm or sedated patients Longer induction period • Avoid in patients with poor respiratory function Intubate immediately when possible • To gain control of airway and ventilation Always keep airway open • Don't occlude nostrils or compress airway or chest

question

Inhalation induction - Chamber

answer

Placing patient in a closed chamber infused with anesthetic gas Patient is usually <5-7 kg body weight Used for small, aggressive patients Examine chamber prior to use Tight-fitting lid with two gas ports

question

Inhalation induction - Chamber complications

answer

Stress, trauma, vomiting, airway blockage Hard to monitor patient Exposes personnel to waste anesthetic gas • Attach scavenger Epinephrine release • Predisposes patient to cardiac arrhythmias and hypotension

question

IM induction

answer

Neuroleptanalgesic combinations and a variety of combinations of tranquilizers, dissociatives, and opioids used to induce general anesthesia Benefits: Use in animals in which IV injections are difficult • Young animals, aggressive animals, wild animals, captive animals in zoos May need restraint equipment, blowpipe, or tranquilizing gun

question

IM vs. IV induction

answer

The dose of a drug needed for IM induction is generally about TWICE the corresponding IV dose IM induction takes longer to achieve high enough brain concentration to induce anesthesia After peak effect of the IM drug is reached and the patient is still too light, an additional drug or inhalant agent must be administered to get the patient deep enough to intubate IM induction results in a longer recovery period because of a longer metabolism time

question

Endotracheal intubation

answer

Endotracheal tube is placed in the patient's airway after general anesthesia induction Conducts air or anesthetic gases directly from oral cavity to trachea Bypasses the nasal passages and pharynx Can be connected to an anesthetic machine to maintain anesthesia

question

Endotracheal intubation - benefits

answer

Helps maintain an open airway • Leave in place until the swallowing reflex returns More efficient delivery of anesthetic gas than facemask • Decreased exposure of personnel to waste gas With inflated cuff helps prevent aspiration of vomitus, blood, saliva Reduces anatomic dead space • Improved efficiency of gas exchange Ventilation can be supported manually or mechanically • Especially useful for patients in cardiac or respiratory arrest

question

Equipment for endotracheal intubation

answer

Three endotracheal tubes of slightly different diameters Two-foot length of IV tubing or rolled gauze to secure tube Gauze sponge to grasp tongue 12-mL syringe to inflate cuff Good light source Stylette for narrow diameter tubes Lidocaine injectable solution or gel to control laryngospasm (cats) Laryngoscope with appropriate blade

question

Selecting an endotracheal tube

answer

Diameter Small enough to not cause trachea injury Large enough to provide a seal with inflated cuff Length: minimize mechanical dead space Must reach the thoracic inlet Must not extend beyond the end of the muzzle Patient Species, conformation, and breed Preparation -clean -lubed on the end, but not covering the murphy's eye

question

Intubation procedure

answer

Know the anatomy of the throat Pharynx and larynx Know the proper restraint and positioning techniques Don't attempt intubation unless you can visualize the larynx Have proper lighting Induce patient with IV anesthetic Unconsciousness, no voluntary movement, no pedal reflex, sufficient muscle relaxation, no swallowing when tongue is pulled

question

Intubation procedure (cont)

answer

Insert tube rapidly and correctly Place patient in lateral recumbency Secure the tube and inflate the cuff Turn on the oxygen Attach the breathing circuit Turn on the anesthetic vaporizer Begin patient monitoring

question

Checking for proper tube placement

answer

Revisualize larynx and confirm the tube is in the correct location Watch reservoir bag as animal breathes Feel for air movement from the tube connector as patient exhales Fogging of the tube during exhalation Unidirectional valve motion Palpate the neck Ability of patient to vocalize indicates misplaced tube Patient coughs during intubation Capnometer connection

question

Laryngospasm

answer

Reflex closure of the glottis in response to contact with an object or substance Common in cats, swine, and small ruminants in light plane of anesthesia Makes intubation very difficult; larynx is easily damaged May lead to cyanosis or hypoxemia

question

Prevention of laryngospasm

answer

2% injectable lidocaine or lidocaine gel Adequate depth of anesthesia Wait for glottis to open before intubating Don't force the tube

question

Securing the tube and cuff inflation

answer

Tie the ET tube securely without compressing the tube Cuff the tube Extend the patient's head Have an assistant close the pop-off valve and compress the reservoir bag Listen for gas leaks Inflate the cuff until the leaking just ceases at a pressure of 20 cm H2O

question

Complications of intubation

answer

Vagus nerve stimulation Brachycephalic dogs or other breed deformities Overzealous intubation efforts Overinflation of cuff Obstructed endotracheal tube Waiting too long to remove the tube Improper cleaning and sanitizing between uses Tracheal and/or laryngeal irritation leading to postsurgical cough

question

Maintenance of general anesthesia

answer

Inhalant agent Repeated boluses of ultrashort-acting agents Continuous rate infusion (CRI) Injectable and inhalant agents Intramuscular injections

question

Patient Positioning, Comfort, and Safety

answer

Support the patient as it loses consciousness (especially the head) Remove IV needle and syringe immediately after successful intubation Lay patient in lateral recumbency immediately after intubation; then secure the tube and inflate the cuff Ensure the endotracheal tube is inserted properly without bends or kinks

question

Patient Positioning, Comfort, and Safety (cont)

answer

Temporarily disconnect tube when turning the patient Support anesthetic machine hoses so no drag is put on the endotracheal tube Check position of hoses and tube during transfer and repositioning Make sure reservoir bag is visible at all times Put animals in as normal a position as possible on the surgery table

question

Patient Positioning, Comfort, and Safety (cont)

answer

Don't use heavy drapes or instruments that will lie on the chest of small animals Don't overtighten leg restraints Place patient on a heat-retaining surface Place normal lung up if one lung is diseased Be cautious of tilting the surgery table Use artificial tears or other corneal lubricant

question

Anesthetic recovery

answer

The period between the time the anesthetic is discontinued and the time the patient is able to stand and walk without assistance Influencing factors: Length of anesthetic period Condition of patient Type of anesthetic administered and route of administration Patient body temperature Patient breed

question

The Anesthetist's Role in Recovery

answer

Discontinue administration of anesthetic agents Continually to monitor patient through the stages of recovery Administer oxygen as necessary, especially to shivering patients Oxygen source placed close to the nostrils Elizabethan collar and cellophane cover Nasal catheter Oxygen cage Administer reversal agents if available

question

The Anesthetist's Role in Recovery (cont)

answer

Maintain patent airway and extubate when appropriate Prepare by deflating cuff and untying gauze Remove when the swallowing reflex returns (dogs, cats) or when signs of impending arousal are present (voluntary limb, tail, or head movements) Remove the tube in one slow, steady motion

question

The Anesthetist's Role in Recovery (cont)

answer

Provide general nursing care Quiet handling, calm reassurance, attention to patient comfort level Prior to consciousness remove all restraint ties and make sure all accessory procedures are complete Prior to consciousness remove all monitoring equipment, probes, cuffs, and electrodes Be gentle when moving the patient Leave IV catheter in place until recovery is complete

question

The Anesthetist's Role in Recovery (cont)

answer

Provide general nursing care (Cont'd) Hasten recovery with gentle stimulation (talking, rubbing, gently move ET tube) Turn every 10-15 minutes to prevent hypostatic congestion Never leave patient unattended Gradually rewarm hypothermic patients

question

The Anesthetist's Role in Recovery (cont)

answer

Provide adequate analgesia and other prescribed medications Analgesics should be administered before the onset of pain Adequate analgesia • Patient sleeps comfortably with minimal signs of discomfort Dose adjustment or switching to a different analgesic may be necessary to control pain Prepare patient for ongoing hospital care or prepare patient for release

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