Transcript Chapter 8
Anesthetic Induction 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 Copyright © 2011, 2003, 2000, 1994 by Mosby, Inc., an affiliate of Elsevier Inc. 1 IV Induction Drugs used Mixture of equal volumes of ketamine and diazepam or midazolam Propofol Neuroleptanalgesics Thiopental sodium Etomidate Various other combinations containing dissociatives, tranquilizers, and opioids Copyright © 2011, 2003, 2000, 1994 by Mosby, Inc., an affiliate of Elsevier Inc. 2 IV Induction (Cont’d) Administer IV to effect (unconsciousness) Don’t administer the entire calculated dose all at once Allow for individual patient response to anesthetic Copyright © 2011, 2003, 2000, 1994 by Mosby, Inc., an affiliate of Elsevier Inc. 3 IV Induction (Cont’d) 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 Copyright © 2011, 2003, 2000, 1994 by Mosby, Inc., an affiliate of Elsevier Inc. 4 Inhalation Induction 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 Copyright © 2011, 2003, 2000, 1994 by Mosby, Inc., an affiliate of Elsevier Inc. 5 Inhalation Induction (Cont’d) Mask induction 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 Copyright © 2011, 2003, 2000, 1994 by Mosby, Inc., an affiliate of Elsevier Inc. 6 Inhalation Induction: Facemask Cautions 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 Copyright © 2011, 2003, 2000, 1994 by Mosby, Inc., an affiliate of Elsevier Inc. 7 Inhalation Induction: Chamber 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 Copyright © 2011, 2003, 2000, 1994 by Mosby, Inc., an affiliate of Elsevier Inc. 8 Inhalation Induction: Chamber (Cont’d) Complications 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 Copyright © 2011, 2003, 2000, 1994 by Mosby, Inc., an affiliate of Elsevier Inc. 9 IM Induction 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 Copyright © 2011, 2003, 2000, 1994 by Mosby, Inc., an affiliate of Elsevier Inc. 10 IM Induction vs. IV Induction 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 Copyright © 2011, 2003, 2000, 1994 by Mosby, Inc., an affiliate of Elsevier Inc. 11 Endotracheal Intubation 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 Copyright © 2011, 2003, 2000, 1994 by Mosby, Inc., an affiliate of Elsevier Inc. 12 Endotracheal Intubation (Cont’d) Benefits 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 Copyright © 2011, 2003, 2000, 1994 by Mosby, Inc., an affiliate of Elsevier Inc. 13 Feline Intubation Copyright © 2011, 2003, 2000, 1994 by Mosby, Inc., an affiliate of Elsevier Inc. 14 Equipment for Endotracheal Intubation 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 Copyright © 2011, 2003, 2000, 1994 by Mosby, Inc., an affiliate of Elsevier Inc. 15 Intubation Equipment Copyright © 2011, 2003, 2000, 1994 by Mosby, Inc., an affiliate of Elsevier Inc. 16 Selecting an Endotracheal Tube Diameter Length: minimize mechanical dead space Must reach the thoracic inlet Must not extend beyond the end of the muzzle Patient Small enough to not cause trachea injury Large enough to provide a seal with inflated cuff Species, conformation, and breed Preparation Copyright © 2011, 2003, 2000, 1994 by Mosby, Inc., an affiliate of Elsevier Inc. 17 Proper Endotracheal Tube Placement Copyright © 2011, 2003, 2000, 1994 by Mosby, Inc., an affiliate of Elsevier Inc. 18 Intubation Procedure Know the anatomy of the throat Know the proper restraint and positioning techniques Pharynx and larynx 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 Copyright © 2011, 2003, 2000, 1994 by Mosby, Inc., an affiliate of Elsevier Inc. 19 Anatomy of the Pharynx Copyright © 2011, 2003, 2000, 1994 by Mosby, Inc., an affiliate of Elsevier Inc. 20 Intubation Procedure 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 Copyright © 2011, 2003, 2000, 1994 by Mosby, Inc., an affiliate of Elsevier Inc. 21 Endotracheal Intubation in Small Animals Copyright © 2011, 2003, 2000, 1994 by Mosby, Inc., an affiliate of Elsevier Inc. 22 Checking for Proper Tube Placement 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 Copyright © 2011, 2003, 2000, 1994 by Mosby, Inc., an affiliate of Elsevier Inc. 23 Laryngospasm 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 Copyright © 2011, 2003, 2000, 1994 by Mosby, Inc., an affiliate of Elsevier Inc. 24 Laryngospasm (Cont’d) Prevention 2% injectable lidocaine or lidocaine gel Adequate depth of anesthesia Wait for glottis to open before intubating Don’t force the tube Copyright © 2011, 2003, 2000, 1994 by Mosby, Inc., an affiliate of Elsevier Inc. 25 Securing the Tube and Cuff Inflation 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 Copyright © 2011, 2003, 2000, 1994 by Mosby, Inc., an affiliate of Elsevier Inc. 26 Complications of Intubation 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_________________Mrs. Singers big no no!! Tracheal and/or laryngeal irritation-______________ Copyright © 2011, 2003, 2000, 1994 by Mosby, Inc., an affiliate of Elsevier Inc. 27 Maintenance of General Anesthesia Inhalant agent Repeated boluses of ultrashort-acting agents Continuous rate infusion (CRI) Injectable and inhalant agents Intramuscular injections Copyright © 2011, 2003, 2000, 1994 by Mosby, Inc., an affiliate of Elsevier Inc. 28 Patient Positioning, Comfort, and Safety 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 Copyright © 2011, 2003, 2000, 1994 by Mosby, Inc., an affiliate of Elsevier Inc. 29 Patient Positioning, Comfort, and Safety (Cont’d) 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 Copyright © 2011, 2003, 2000, 1994 by Mosby, Inc., an affiliate of Elsevier Inc. 30 Patient Positioning, Comfort, and Safety (Cont’d) 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 Copyright © 2011, 2003, 2000, 1994 by Mosby, Inc., an affiliate of Elsevier Inc. 31 Anesthetic Recovery 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 Copyright © 2011, 2003, 2000, 1994 by Mosby, Inc., an affiliate of Elsevier Inc. 32 The Anesthetist’s Role in Recovery 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 Copyright © 2011, 2003, 2000, 1994 by Mosby, Inc., an affiliate of Elsevier Inc. 33 The Anesthetist’s Role in Recovery (Cont’d) 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 Copyright © 2011, 2003, 2000, 1994 by Mosby, Inc., an affiliate of Elsevier Inc. 34 The Anesthetist’s Role in Recovery (Cont’d) 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 Copyright © 2011, 2003, 2000, 1994 by Mosby, Inc., an affiliate of Elsevier Inc. 35 The Anesthetist’s Role in Recovery (Cont’d) 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 Copyright © 2011, 2003, 2000, 1994 by Mosby, Inc., an affiliate of Elsevier Inc. 36 The Anesthetist’s Role in Recovery (Cont’d) 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 Copyright © 2011, 2003, 2000, 1994 by Mosby, Inc., an affiliate of Elsevier Inc. 37