Test 1- Inhalant Anesthesia Flashcards

Question

Respiratory effects of inhalant anesthetics

Answer 1

Respiratory  Decrease ventilation  Depress central and peripheral chemoreceptors  Decreased responsiveness to CO2  Respiratory arrest at 1.5-3 MAC  Bronchodilation  Desflurane and isoflurane – irritating odor  Sevoflurane – least irritating 40 https://basicsofpediatricanesthesia.files .wordpress.com/2013/07/mask- induction.jpg

Answer 2

 Increase intracranial pressure at \> 1 MAC  Increase cerebral blood flow  Decrease cerebral metabolic rate  Act on brain and spinal cord to produce immobility (not analgesia)  Suppress seizure activity (except Enflurane)

Answer 3

 Decrease glomerular filtration rate and renal blood flow due to decreased CO  Renal failure (methoxyflurane)

Answer 4

 Produced from sevoflurane breakdown in CO2 absorbent (baralyme \> soda lime)  Higher concentrations formed during:  Prolonged anesthesia  Low fresh gas flows  Desiccated absorbent  Nephrotoxic in rats

Answer 5

 Produced from sevoflurane breakdown in CO2 absorbent (baralyme \> soda lime)  Higher concentrations formed during:  Prolonged anesthesia  Low fresh gas flows  Desiccated absorbent  Nephrotoxic in rats

Answer 6

 Reduce liver blood flow and O2 delivery (related to decrease in CO)  Halothane can cause hepatotoxicity (2 types) 1. Increased liver enzymes – mild, self- limiting, 2. “Halothane hepatitis” – immune- mediated, often fatal

Answer 7

 Myopathy occurring in genetically predisposed pigs, dogs, cats, horses, (people)  Exposure to inhalant anesthetic  Esp. halothane, but also iso, sevo, des  Uncontrolled muscle contraction  severe hyperthermiadeath  First sign is often a rapid increase in EtCO2

Answer 8

 Treatment  Discontinue volatile anesthetic, flush with O2, switch to new circuit if possible  Provide 100% O2  Administer dantrolene – muscle relaxant  Fluids, active cooling  Death likely despite treatment  EXTREMELY rare  Maybe once per CAREER (\>30 yrs) for an anesthesiologist

Answer 9

 Used more frequently in people (lower MAC) than animals  Max administration 75% (need \> 25% O2)  Low solubility (blood-gas PC 0.47)  Minimal CV and resp depression  Mild analgesic  Transfer to closed gas spaces  Equilibration leads to N2O accumulating rapidly (more soluble in blood) while Nitrogen leaves slowly (less soluble)  GI tract, sinuses, middle ear, pneumothorax, GDV, cuff of ET tube  Avoid in disease states causing increased closed gas space

Answer 10

 When N2O administration is stopped, it diffuses quickly out of the blood into alveoli (down concentration gradient)  Displaces O2 from alveoli  If breathing room airhypoxia  When discontinuing N2O, provide 100% O2 for 5-10 minutes to prevent 51

Answer 11

Common complications of inhalant anesthesia  Anesthetic-related  Hypotension  Hypoventilation  Hypothermia  Machine-related  Closed pop-off  Stuck inspiratory- expiratory valves  Exhausted soda lime  Inadequate O2 flow in non-rebreathing system  Human error  Intubation mishaps  Laryngeal damage  Stuck tube  Aspirated tube  Tracheal tears  Anesthetic overdose

Answer 12

Hypotension  MAP\<60 mmHg (small animal) or \<70 mmHg (large animal)  Roughly corresponds to Doppler BP of 80 or 90  FIRST, evaluate patient and TURN DOWN THE VAPORIZER if the patient is too deep for the current level of stimulation  This is the most appropriate and effective treatment for hypotension during inhalant anesthesia  If patient is light, consider adding a MAC-sparing drug and THEN turn down the vaporizer  Opioid, benzodiazepine, lidocaine, ketamine, etc. 55  If still hypotensive, evaluate the underlying cause and treat appropriately  Decreased vascular volume (hypovolemia)?  Give crystalloid and/or colloid bolus  Vasodilation?  Give vasopressor  Decreased contractility?  Give inotrope

Answer 13

Definition: PaCO2\>40 mmHg OR EtCO2\>45 mmHg  However, EtCO2 up to 50-55 mmHg may be tolerated in certain patients (slightly complicated and controversial topic)  FIRST, evaluate patient and TURN DOWN THE VAPORIZER if the patient is too deep for the current level of stimulation (sound familiar?)  Perform IPPV  Manual  Mechanical  Hypothermia Inhalant anesthesia abolishes the normal vascular compensatory mechanisms to conserve heat  Causes peripheral vasodilation  increased heat LOSS Prevention is more effective than treatment  Warm patient before induction (especially small ones)  Bubble wrap feet  Keep patient covered, minimize scrub time and exposure to water/alcohol  Increase room temp  Forced warm air heating (BAIR hugger)

Answer 14

What happens?  Bag fills, breathing system pressure increases, pressure transmitted to patient lungs and thoracic cavity  Decreased venous return (decreased preload)compressed great vessels (increased afterload)DECREASED CARDIAC OUTPUT  Clinical signs = apnea, bradycardia, fading Doppler signalcardiopulmonary arrest  Treatment  Pull rebreathing bag off (usually faster than unscrewing pop-off)  Start CPR if patient has arrested  Evaluate for pulmonary injury (auscultation, chest radiographs)  Revisit habits and safety checklists  Use quick-release or safety pop-offs  Don’t take hand off closed pop-off until open again (for leak check)  Potential for pneumothorax

Answer 15

 What happens?  Rebreathing system becomes bidirectional  Causes rebreathing of expired gas  hypercarbia  Signs?  Easy to see on a capnograph (rebreathing waveform)  If no capnograph, need to be more vigilant  Should be obvious visually if valves are sticking open  If concerned, check that valves are functional by inspiring and expiring through \*flushed\* system  What are signs of hypercarbia in your patient?  Treatment  Dry and clean valves frequently, especially after long cases  Replace as needed

Answer 16

 What happens?  Soda lime no longer removes CO2 from expired gases  Patient rebreathes CO2hypercarbia  Will look THE SAME as stuck inspiratory-expiratory valves on capnograph (rebreathing waveform)  What else can cause this waveform?  \*\*Inadequate O2 flow in a non-rebreathing system\*\*

Answer 17

Note that the waveform does NOT return to baseline (0) between breaths Possibilities: Stuck insp/exp valves Exhausted soda lime Inadequate O2 flow in a non-rebreathing 63 system

Answer 18

 From laryngoscope or stylet most commonly  Be gentle! Tissues are sensitive  Swelling can lead to post-op airway obstruction  If you use a stylet for cat intubation, it SHOULD NOT protrude past the end of the ET tube  Place the laryngoscope on the base of the tongue (don’t touch the epiglottis)

Answer 19

 Do not force an ET tube that is too big for your patient  It may go in, but not come out!  What would you do?  Re-anesthetize quickly (propofol or alfaxalone)  Cut tube to allow compression

Answer 20

 Aspirated tube  If patient bites through tube and aspirates the intra- tracheal portion  What would you do?  Re-anesthetize quickly (propofol or alfaxalone)  Provide O2  Retrieve tube  Long forceps  Re-intubate with smaller tube, inflate cuff, then pull both tubes out together  Tracheoscopy or bronchoscopy may be required  Ideally, avoid this complication by providing proper patient monitoring  Don’t wait too long to extubate!

Answer 21

 Not uncommon in cats  Associated with overfilling of the tube cuff  Only fill until there is no leak at 15- 20 cm H2O, no more  Do not add air unless there is a leak  Associated with traction on tube (weight of breathing tubes) and turning/twisting patient  ALWAYS disconnect patient from breathing system before moving

Answer 22

 Inhalant anesthetics have a very low therapeutic index (difference between a therapeutic and fatal dose) Overdose can happen very quickly  Especially at high flow rates and vaporizer settings If in doubt about the status of your patient – turn the inhalant down or OFF while you evaluate the situation  Remember that patient movement does not mean a conscious patient A very low blood pressure (MAP \< 50) indicates inadequate cerebral blood flow for consciousness  (The patient doesn’t need inhalant anesthesia to stay asleep)  TURN THE INHALANT ANESTHETIC OFF UNTIL BP HAS IMPROVED!  Sick patients often need VERY LITTLE inhalant  Utilize your MAC-sparing drugs – opioids, benzos, lidocaine, ketamine, etc.  A moving patient is tolerable in most cases and preferred over a dead patient