Intro to Anesthesia - Pharm

History of Anesthesia

  • The discovery of anesthesia was revolutionary to medicine
    • Surgery: painful > relief, healing
    • Early medicine (as early as 15th century BC):
      • Use plant extracts to control pain, produce sleep
        • Belladonna alkaloids (deadly nightshade plants); Opiates (from opium poppy)
      • Used for thousands of years
  • Development of Inhaled Anesthetics
    • 1500-1700s: experimentation with inhaled anesthetics occurred
      • Diethyl ether, chloroform, nitrous oxide
    • 1800: use for these techniques became more refined, widespread
    • 1846: Dentist William A.G. Morton gave first successful demonstration of diethyl ether used to control pain for a tumor removal at Mass Gen Hospital
    • Use of anesthesia spread across US and Europe
    • Veterinary Medicine - did not embrace for some time
      • Some reports of use with animals
      • Physical restraint was primary means of immobilization until well into the 20th century
  • Modern Developments in Anesthesia
    • 1930s: Injectable barbiturates (veterinarians had alternative to inhaled anesthetics)
    • 1950s: Inhaled drugs halothane, methoxyflurane
    • 1960s: Acepromazine, Xylazine
    • 1970s: Ketamine
    • 1980s: Inhaled drug isoflurane;propofol
    • 1990s: Inhaled drug sevoflurane
    • Continued development for safer, better drugs

Anesthesiology as a Discipline

  • Academy of Veterinary Technicians in Anesthesia and Analgesia (AVTAA)
    • Regnizes as VTS in 1999
    • Specialization to credentials technicians with interest in anesthesia/analgesia
    • List of requirements to demonstrate competency
  • American College of Veterinary Anesthesia and Analgesia (ACVAA)
    • Specialization to credentialed veterinarians
    • Also provides resources for anesthesia and analgesia in veterinary medicine

Terminology

  • Anesthesia:
    • From greek word for “without feeling” or “insensibility”
    • Defined as loss of sensation
    • Used daily in Vet medicine
    • Literal term “Anesthesia” is a bit outdated - many facets of it now
  • General Anesthesia:
    • Reversible state of unconsciousness, immobility, muscle relaxation, loss of sensation throughout the entire body throughout the whole body produced by 1 or more anesthetic agents
    • Commonly used for : patient prep for surgery, other acutely painful procedures
    • Patient cannot be aroused (even with painful stimuli)
  • Surgical Anesthesia:
    • Specific stage of general anesthesia
    • Sufficient degree of analgesia and muscle relaxation to allow surgery to be performed without patient pain or movement
  • Analgesia:
    • Loss of sensation of pain
  • Sedation:
    • Drug-induced CNS depression and drowsiness
    • Intensity from light to deep
    • Patient minimally aware or unaware of surroundings
    • Can be aroused by noxious stimulation
    • Can provide some analgesia (not always)
  • Tranquilization:
    • Drug-induced state of calm in which patient is reluctant to move, aware of but unconcerned about its surroundings
    • Reduced anxiety, sense of tranquility
    • No analgesic effects
  • Hypnosis vs Narcosis:
    • Hypnosis - Drug-induced sleeplike state that impairs ability of patient to respond appropriately to stimuli
      • Generally - patient can be roused with sufficient stimuli
    • Narcosis - Drug-induced sleep from which patient is not easily aroused and that is often associated with the administration of narcotics
  • Local Anesthesia:
    • Loss of sensation in: small area of body
    • Produced by administration of local anesthetic agent in proximity to area of interest
    • Example: Infiltration around small tumor to facilitate removal
  • Topical Anesthesia:
    • Loss of sensation of localized area by local anesthetics placed directly on to body surface or surgical/traumatic wound
    • Example:
      • Ophthalmic local anesthetic drops in eye before exam
      • Local anesthetic to declaw incision for pain control
  • Regional Anesthesia:
    • Loss of sensation in limited area of body by administration of local anesthetic or other agent in proximity to to sensory nerves
    • Variety of techniques - nerve blocks, epidural anesthesia
    • Example: Maxillary nerve block used to anesthetize upper dental arcade; epidural anesthesia

Balanced Anesthesia

  • Technique using:
    • Multiple drugs
    • In smaller quantities (than if used alone)
    • Maximize benefits of each drug
    • Minimize adverse effects
    • Give anesthetist ability to produce anesthesia with appropriate conditions to patient and procedure
      • Appropriate degree of CNS depression, muscle relaxation, analgesia, and immobilization
    • Example:
      • Patient premeded with acepromazine
      • Anesthetic induction with ketamine/diazepam
      • Maintained with isoflurane
      • Morphine and lidocaine infusion for analgesia

The Role of the Veterinary Technician/Nurse

  • Responsibilities include:
    • Preparation, operation, and maintenance of equipment
    • Administration of anesthetic agents
    • Endotracheal intubation
    • Patient monitoring

Challenges for Anesthetists

  • Most anesthetic agents have a very narrow therapeutic index
  • Errors in calculations or administration can be very serious
  • Care and attention to detail is critical!
  • Most anesthetic agents cause significant changes to cardiovascular and pulmonary function
    • Example:
      • Decreased cardiac output, decreased respiratory rate, decrease tidal volume, decreased blood pressure
    • Changes occur quickly, sometimes without warning; monitoring vital signs closely
  • Anesthetists must interpret a wide variety of information from a variety of sources
    • Visual, tactile, and auditory information from patient, anesthetic equipment, and monitoring devices
  • Must rapidly interpret information and distinguish what requires action from what does not
  • Anesthetist must have comprehensive understanding of physical parameters (HR, RR, Reflexes) and machine-generated data (blood pressure, oxygen saturation, etc)
  • Must understand these parameters in the frame of the anesthetic procedure, while making rapid and decisive judgments regarding patient management and carry out corrective actions quickly and effectively
  • Potential for harm with anesthetic drugs is relatively high when compared to other procedures
  • When serious accidents occur, often devastating for patient as well as client and the veterinary staff
  • Clients can pursue legal action or file complaint with state board
  • Importance of maintaining high standards
    • Sound practices
    • Maintenance of accurate medical records