Advanced Medical Care: Improving Veterinary Anesthesia. Advanced Medical Care: Improving Veterinary Anesthesia

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1 Advanced Medical Care: Improving 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 1

2 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 Preanesthesia Induction Patient preparation for anesthesia SEDATION & ANALGESIA Achieve unconsciousness smoothly & rapidly; dose TO EFFECT Maintenance Dose TO EFFECT; May need to add more analgesia; MONITOR & SUPPORT Recovery May need more analgesia and/or sedation MONITOR & SUPPORT 2

3 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

4 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

5 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

6 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 mg/kg Lipid soluble Administered IV or orally Slightly less potent Slightly longer duration of action Water soluble Can administer by various routes IM, IV, intranasally, rectally, orally Clinically very similar to diazepam 6

7 Preanesthesia Induction Maintenance Patient preparation for anesthesia SEDATION & ANALGESIA Achieve unconsciousness smoothly & rapidly; dose TO EFFECT Dose TO EFFECT; May need to add more analgesia; MONITOR & SUPPORT Recovery May need more analgesia and/or sedation 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

8 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. Preanesthesia Induction Patient preparation for anesthesia SEDATION & ANALGESIA Achieve unconsciousness smoothly & rapidly; dose TO EFFECT Maintenance Dose TO EFFECT; May need to add more analgesia; MONITOR & SUPPORT Recovery May need more analgesia and/or sedation MONITOR & SUPPORT 8

9 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

10 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

11 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 Preanesthesia Induction Maintenance Patient preparation for anesthesia SEDATION & ANALGESIA Achieve unconsciousness smoothly & rapidly; dose TO EFFECT Dose TO EFFECT; May need to add more analgesia; MONITOR & SUPPORT Recovery May need more analgesia and/or sedation 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); % overall complication rate 3% intraop 23% in the PACU (recovery unit) 11

12 The incidence of postoperative complications in the PACU Mayson KV, Beestra JE, Choi PT Respiratory complications 15.2% Apnea, airway obstruction, hypoxemia CV complications 12.3% Hypertension, hypotension, arrhythmias Excessive pain 7.2% Cookbook anesthesia is okay Most patients are suitable for a basic protocol ADD ANALGESIA as pain intensity progresses DOSE TO EFFECT HAVE to have more than one recipe Compromised patients clearly need protocols that fit their underlying disease DOSE TO EFFECT Monitoring & appropriate support for ALL patients Della - Ovariohysterectomy Della 6-month old healthy Labrador Retriever PE normal Serum chemistry, CBC normal Elective OHE 12

13 Premeds Morphine or hydromorphone Medetomidine or acepromazine NSAID Induction Propofol Maintenance Sevoflurane Recovery Analgesia, as needed NSAID dispensed for post-discharge pain 4 yr, healthy MN mixed breed Acutely lame, left rear, after Frisbee Stifle swollen, painful Drawer sign elicited Surgical repair of CCL Premeds Morphine or hydromorphone Medetomidine or acepromazine NSAID Induction Propofol Maintenance Sevoflurane Epidural and/or intra-articular morphine Recovery Analgesia, as needed NSAID dispensed for post-discharge pain + tramadol, fentanyl patch or codeine 13

14 Ginger, 16 yr old FS Grade III heart murmur Regulated diabetes No other abnormalities Dentistry with extractions Premeds Morphine or Hydromorphone decrease dose, no other sedation NSAIDs? Induction Propofol Maintenance Sevoflurane Local anesthetic dental blocks Recovery Analgesia, as needed NSAIDs for post-discharge pain +/- tramadol SAME PRINCIPLES Standard protocols are good Have more than one protocol Balanced anesthesia and analgesia Each phase of anesthesia is equally important Address analgesia in all phases MONITOR & SUPPORT 14

15 Premedication Sedation / analgesia Induction Fast & smooth Maintenance Readdress analgesia MONITOR & SUPPORT Recovery Sedation / analgesia Monitor & Support Pain doesn t end at discharge THANK YOU ABBOTT! 1. Complete the evaluation by Monday, May 4, Please have only one person from your practice complete this evaluation. - To complete the evaluation, please go to the following website: 2. After completing the evaluation, you will automatically be linked to the Continuing Education Certificate. The CE certificate can only be accessed after the evaluation is completed. 3. Download the CE Certificate (in pdf format) to your computer and print enough copies for your entire team. Your input is very important! We take feedback seriously in order to provide you with the highest quality experience possible. If you have any questions about completing the evaluation or accessing your CE certificate, please us at webconference@aahanet.org or call 800/ Questions to the Speaker If you didn t get a chance to submit your questions through the online chat feature or have additional questions, please your questions to webconference@aahanet.org by Thursday, April 30, Dr. Grubb will provide written responses to all of the questions and they will be posted on AAHA s website by Monday, May 4, AAHA gratefully acknowledges the following for their sponsorship of this Web Conference. 15