Advanced Medical Care: Improving Veterinary Anesthesia 1 Advanced - PDF document

Advanced Medical Care: Improving Veterinary Anesthesia AAHA National Staff Meeting Web Conference -Thursday, April 23, 2009 Advanced Medical Care: Improving Veterinary Anesthesia Thursday, April 23, 2009 By Tamara Grubb, DVM, MS, DACVA AAHA gratefully acknowledges the following for their sponsorship of this Web Conference: Advanced Medical Care: Improving Veterinary Anesthesia 1

Advanced Medical Care: Improving Veterinary Anesthesia AAHA National Staff Meeting Web Conference -Thursday, April 23, 2009  1989 Standard Patient  Young, healthy  Spay, castration  2009 Standard Patient  ????  Advanced disease  Advanced age  Advanced surgical procedures  ADVANCED ANESTHESIA  Anesthesia is an event, not a drug choice  The event should include  Appropriate patient preparation  Preemptive, multimodal analgesia  Balanced anesthesia  Support & MONITORING ▪ From pre-op to post-op – not just while in the OR ▪ Most unexpected anesthetic deaths occur in recovery • Patient preparation for anesthesia Preanesthesia • SEDATION & ANALGESIA • Achieve unconsciousness smoothly & Induction rapidly; dose TO EFFECT • Dose TO EFFECT; May need to add more Maintenance analgesia; MONITOR & SUPPORT • May need more analgesia and/or sedation Recovery • MONITOR & SUPPORT 2

Advanced Medical Care: Improving Veterinary Anesthesia AAHA National Staff Meeting Web Conference -Thursday, April 23, 2009  The administration of analgesic and sedative drugs in the pre-operative period allows a decrease in the dosage of induction and maintenance anesthetic drugs  Side effects of anesthetic drugs are DOSE DEPENDENT  Decreased stress for the patient  Decreased release of catecholamines  Decreased work for the staff  Calm patients are easier to work with  Receptors in dorsal horn of spinal cord become ‘upregulated’ or ‘hypersensitized’ from painful impulses  Preemptive analgesia decreases input to these receptors  Multimodal drug delivery ‘blocks’ pain pathway at different sites  Effects of drugs are synergistic From: Pain Management for the Small Animal Practitioner, Tranquilli, et al. Teton New Media  Patients that received adequate analgesia:  experienced fewer complications ▪ GI dysfunction (indigestion, ileus, ulceration) ▪ Clotting dysfunction (hypercoaguability, emboli) ▪ Pulmonary dysfunction (atelectasis & pneumonia)  healed faster, better long term results ▪ Decreased cortisol release References: Alder et al, Swiss Med Wkly 2004; Callesen, Dan Med Bull 2003; Cohen et al, Am J Phys Med Rehabil 2004. 3

Advanced Medical Care: Improving Veterinary Anesthesia AAHA National Staff Meeting Web Conference -Thursday, April 23, 2009  Analgesics  Opioids  Alpha-2 agonists  NSAIDs  Tranquilizers  Opioids  Alpha-2 agonists  Acepromazine  Benzodiazepines  Most potent class of analgesic agents  Should be included ANYTIME that pain occurs, especially when pain is moderate to severe  This includes surgical, medical and traumatic pain whether acute or chronic  MINIMAL SIDE EFFECTS – high safety margin  ‘Respiratory depression’ is over -rated  Minimal to no cardiovascular effects  Relatively short acting when compared to the duration of pain  Use multimodal analgesia 4

Advanced Medical Care: Improving Veterinary Anesthesia AAHA National Staff Meeting Web Conference -Thursday, April 23, 2009  Morphine, hydromorphone, fentanyl  Most potent opioids due to receptor binding  Moderate duration, moderate to good sedation (depending on species, age, health)  INEXPENSIVE  Buprenorphine  Moderately potent, longer duration of analgesia, minimally sedating  Butorphanol  Moderately potent, short duration of action, excellent sedative  Advantages  Provide analgesia and sedation  Reversible  Can titrate sedation from mild to profound  Disadvantages  Cardiovascular effects ▪ Hypertension, increased cardiac work  Bradycardia is a normal reflex 5

Advanced Medical Care: Improving Veterinary Anesthesia AAHA National Staff Meeting Web Conference -Thursday, April 23, 2009  Advantages  Inexpensive  Mild to moderate sedation  Long lasting  Disadvantages  MAY contribute significantly to hypotension, hypothermia  MAY last too long  No analgesia, not reversible  Advantages  Minimal to no cardiovascular or respiratory depression  Disadvantages  Generally will not get good sedation when used alone in young or aggressive patients  Dose  0.1-0.2 mg/kg  Water soluble  Lipid soluble  Administered IV or  Can administer by orally various routes ▪ IM, IV, intranasally,  Slightly less potent rectally, orally  Slightly longer  Clinically very similar duration of action to diazepam 6

Advanced Medical Care: Improving Veterinary Anesthesia AAHA National Staff Meeting Web Conference -Thursday, April 23, 2009 • Patient preparation for anesthesia Preanesthesia • SEDATION & ANALGESIA • Achieve unconsciousness smoothly & Induction rapidly; dose TO EFFECT • Dose TO EFFECT; May need to add more Maintenance analgesia; MONITOR & SUPPORT • May need more analgesia and/or sedation Recovery • MONITOR & SUPPORT  Ketamine / valium  Propofol  Other choices  Telazol, thiobarbiturates, etomidate  USE THE RIGHT DOSE!  DOSE ‘TO EFFECT’.  Advantages  Generally, no cardiovascular depression  Minimal respiratory depression  Can administer IM  Disadvantages  Must be combined with sedative  Can cause tremors, excitement, muscle rigidity  Recoveries can be rough 7

Advanced Medical Care: Improving Veterinary Anesthesia AAHA National Staff Meeting Web Conference -Thursday, April 23, 2009  Advantages  Fast acting ▪ EASY to dose to effect  Short duration  Good muscle relaxation  Cleared from body by multiple routes  Disadvantages  Moderate respiratory depression  Mild to moderate cardiovascular depression  NOT recommended for most cases  Too slow, not controlled, excitement common  High drug dosage  STAFF EXPOSURE  DEFINITELY NOT for cases in which excitement can be detrimental  Cardiovascular disease, upper airway dysfunction, etc. • Patient preparation for anesthesia Preanesthesia • SEDATION & ANALGESIA • Achieve unconsciousness smoothly & Induction rapidly; dose TO EFFECT • Dose TO EFFECT; May need to add more Maintenance analgesia; MONITOR & SUPPORT • May need more analgesia and/or sedation Recovery • MONITOR & SUPPORT 8

Advanced Medical Care: Improving Veterinary Anesthesia AAHA National Staff Meeting Web Conference -Thursday, April 23, 2009  Advantages  Easy to change anesthetic depth  Minimal metabolism compared to injectable agents  Protected airway, O2 administration  Disadvantages  DOSE-DEPENDENT cardiovascular and respiratory depression  Dose to effect  Solubility  Virtually insoluble ▪ Blood-Gas Solubility ▪ Sevoflurane 0.69 ▪ Isoflurane 1.38  Low solubility provides extremely rapid induction, change of anesthetic depth and recovery  Can be everyday, sole inhalant  Any case benefitting from smooth, rapid and ‘thorough’ recovery ▪ No dysphoria, No residual sedation  C-sections  Outpatient procedures  Neonates / geriatrics  Etc… 9

Advanced Medical Care: Improving Veterinary Anesthesia AAHA National Staff Meeting Web Conference -Thursday, April 23, 2009  Inhalant anesthetics are biggest contributors to:  Hypotension, hypoventilation, hypothermia  KEEP YOUR VAPORIZER SETTING LOW  Best way to decrease vaporizer setting is to increase analgesia  Local anesthetic blockade  Supplemental opioid or alpha-2 agonist doses  Constant rate infusions (CRIs)  If you could have only ONE monitor, what would it be?  A good technician!  Anesthesia causes depression of ALL organ systems  Cardiovascular & respiratory depression most immediately life threatening  MONITOR BLOOD PRESSURE  Oscillometric and/or Doppler units  Should use true respiratory monitor  Pulse oximeter is not a true respiratory monitor  ETCO2 is good measurement of ventilation  Monitor the basics  MM color, CRT, jaw tone, body temperature, etc… 10

Advanced Medical Care: Improving Veterinary Anesthesia AAHA National Staff Meeting Web Conference -Thursday, April 23, 2009  If it isn’t right – FIX IT  Hypotension (MAP<60 mmHG)  Decrease anesthetic depth, increase fluid rate  Give bolus of crystalloids, consider colloids  Administer positive inotrope (eg, dopamine)  Hypoventilation (ETCO2>50 mmHg)  Occurs more often than we think  BREATHE!  Hypoventilation has many causes  Hypothermia – keep patients warm • Patient preparation for anesthesia Preanesthesia • SEDATION & ANALGESIA • Achieve unconsciousness smoothly & Induction rapidly; dose TO EFFECT • Dose TO EFFECT; May need to add more Maintenance analgesia; MONITOR & SUPPORT • May need more analgesia and/or sedation Recovery • MONITOR & SUPPORT  Most unexpected anesthesia-related adverse events occur in recovery A Description of Intraoperative and Postanesthesia Complication Rates Tarrac SE, Journal of PeriAnesthesia Nursing, 2006:21(2);88-96  26% overall complication rate  3% intraop  23% in the PACU (recovery unit) 11