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PRINCIPLES OF PAIN MANAGEMENT ANALGESIA

• thERE IS NO COMING TO CONSCIOUSNESS WITHOUT
  PAIN.
• -CARL JUNG

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PRINCIPLES OF PAIN ANALGESIA

• WHAT IS PAIN?
• An unpleasant sensory or emotional experience
  associated with actual or potential tissue damage
• Pain results when nerve cells in the skin or deep
  tissues, called _______________, detect a noxious
  stimulus
• 2 types of sensory neurons that detect and
  transmit pain
• _________________(large, myelinated)
• Transmit sharp, discrete pain signals that allow
  the patient to localize the source of pain.
• transmits somatic pain
• _________________(small, nonmyelinated)
• Transmit dull, aching, throbbing pain that cannot
  be easily localized
• transmits somatic visceral pain (visceral pain
  is only transmitted by C fibers)

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PRINCIPLES OF PAIN ANALGESIA

• THE PAIN PATHWAY
• _________________ transformation of noxious
  thermal, chemical, or mechanical stimuli into
  electrical signals called action potentials by
  A-delta C fibers
• _________________ these sensory impulses are
  then conducted to the spinal cord
• _________________ in the spinal cord where the
  A-delta C fibers terminate, the impulses can be
  altered by other neurons, which either amplify or
  suppress them.
• _________________ the impulses are transmitted
  to the brain, where they are processed and
  recognized.

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THE PHYSIOLOGY OF PAIN
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PRINCIPLES OF PAIN ANALGESIA

• WHAT IS PAIN?
• __________ arises from the skin, soft tissues,
  muscles, bones, or joints
• Easily localized through stabbing, throbbing, or
  aching
• ___________arises from internal organs
• not easily localized and is characterized by
  cramping or burning
• ____________term used to describe the pain that
  is felt in a body part other than where the
  actual pain stimulus is coming from

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PRINCIPLES OF PAIN ANALGESIA

• WHAT IS PAIN?
• ______________ is increased sensitivity to a
  stimulus
• _______________arises from direct damage to
  peripheral nerves or the spinal cord.
• May be shooting, sharp, or tingling
• _____________or stump pain is sensation or pain
  arising from the missing body part
• Pain can also be classified according to onset
  and duration
• ________ pain has an abrupt onset and a
  relatively short duration of action. Effectively
  treated with analgesic drugs
• ________ pain has a slow onset, and duration of
  several months to years. May be unresponsive to
  drug therapy

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PRINCIPLES OF PAIN ANALGESIA

• MYTHS ABOUT PAIN IN ANIMALS
• Consider how some people without medical
  backgrounds may view the animals response to pain

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PRINCIPLES OF PAIN ANALGESIA

• THE 5 FREEDOMS OF ACCEPTABLE ANIMAL WELFARE
• Freedom from hunger
• Freedom from physical and thermal discomfort
• Freedom from pain, injury, disease
• Freedom to express normal behavior
• Freedom from fear and distress

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PRINCIPLES OF PAIN ANALGESIA

• WHAT ABOUT OUR ANIMAL PATIENTS AND/OR OUR JOBS
  COULD MAKE MONITORING FOR PAIN and ADMINISTERING
  ANALGESICS DIFFICULT?

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PRINCIPLES OF PAIN ANALGESIA

• MONITORING SIGNS OF PAIN
• Consider how we as humans display pain vs. how
  our animal patients display pain. Write some ways
  you can monitor for pain in animals.
• 3 TYPES OF BEHAVIORS ASSOICIATED W/PAIN IN ANIMALS

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PRINCIPLES OF PAIN ANALGESIA

• PAIN ASSESSMENT
• The measurement of pain is important to
• Pain scales
• Based on observers assessment of patients
  spontaneous behaviors, and behaviors on handling,
  interaction, and manipulation, maybe
  physiologic parameters.
• Pain scores should be reassessed regularly and
  preferably by the same person to minimize
  observer variation.

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PRINCIPLES OF PAIN ANALGESIA

• PAIN ASSESSMENT TOOLS Simple descriptive scale

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PRINCIPLES OF PAIN ANALGESIA

• PAIN ASSESSMENT TOOLS Numeric rating scales

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PRINCIPLES OF PAIN ANALGESIA

• PAIN ASSESSMENT TOOLS Visual analogue scale

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• PAIN ASSESSMENT TOOLS Comprehensive scales

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PRINCIPLES OF PAIN ANALGESIA

• CONSEQUENCES OF UNTREATED PAIN
• Consider the long term effects of untreated pain

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PRINCIPLES OF PAIN ANALGESIA

• PHYSIOLOGICAL SIGNS OF PAIN

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PRINCIPLES OF PAIN ANALGESIA

• WHAT IS ANALGESIA?
• ___________ is the absence of the awareness of
  pain, achieved through the use of drugs or other
  modes of therapy. It applies to the relief of
  pain without the loss of consciousness.
• WHAT ARE THE GOALS FOR PAIN CONTROL?
• Control pain at every stage of treatment
• to administer analgesics before the patient has
  an awareness of pain. This is known as
  ____________________.
• Decreases the analgesic requirements
• Decreases CNS sensitization
• To prevent __________ an event caused by a
  buildup of chemical mediators that intensify the
  pain response

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PRINCIPLES OF PAIN ANALGESIA

• METHODS OF PAIN CONTROL WITHOUT MEDS
• _______________ are endogenous compounds
  produced by the pituitary gland and the
  hypothalamus that bind to opioid receptors during
  situations of trauma or stress. They resemble
  opiates in their ability to provide pain relief
  and a feeling of well-being. natural pain
  reliever
• Nursing care
• Other therapies to control pain

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PRINCIPLES OF PAIN ANALGESIA

• METHODS OF PAIN CONTROL USING MEDS
• OPIOIDS
• NSAIDS
• OTHERS alpha-2 agonists, ketamine, steroids
• LOCAL ANESTHETICS

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METHODS OF PAIN CONTROL USING MEDS

• OPIOIDS

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OPIOIDS

• MODE OF ACTION
• Acts on 4 different receptors in the brain and
  spinal cord
• _______
• _______
• _______
• Sigma(only cause hallucination,
  euphoria/dysphoria)
• An opioid agent may act as an _______
  (stimulating agent) or __________ (blocking
  agent) at each receptor
• Some opioid agents are considered
  _________________________in that they block one
  type of receptor and stimulate another or
  _______________in that they only partially
  stimulate some opioid receptors
• Binding to these receptors can result in a
  number of effects
• ANALGESIA
• Respiratory depression
• Sedation
• Dysphoria
• And others,

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OPIOIDS

• REVERSIBILITY
• One major advantage of opioids is their
  reversibility with pure antagonists such as
  ______________, which is the most effective
• Naloxone competitively binds to opioid receptors
• It is also possible to use a mixed
  agonist/antagonist such as BUTORPHANOL or a
  partial agonist such as BUPRENORPHINE to reverse
  the effects of the pure agonists
• CONTROLLED

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OPIOIDS

• MORPHINE a FULL AGONIST (stimulates all 4
  receptors)
• Great for moderate to severe pain
• Produces significant sedation
• cardiovascular respiratory depression
• SIDE EFFECT/CAUTIONS
• Can cause excitement in cats (use lower doses)
• Often results in ______________ due to its
  effects on the CRTZ
• Give slowly IV otherwise severe
  __________________release can lead to hypotension
  and pruritis
• Other FULL AGONISTS include oxymorphone,
  hydromorphone, and fentanyl

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OPIOIDS

• FENTANYL a FULL AGONIST (stimulates all 4
  receptors)
• the injectable has a rapid onset of action and
  short duration of action. Onset of action 2 min
  duration of effect 20-30 min
• commonly used as a _____________ skin patch
• Fentanyl is slowly absorbed through the skin and
  may take 4-12 hrs in cats, and 12-24 hrs in dogs
  to reach therapeutic levels
• See pg 230 in your book, Procedure 7-1 for
  instructions on placing a fentanyl patch.

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OPIOIDS

• METHADONE a synthetic opioid that has agonist
  effects at the mu receptor similar
  characteristics to oxymorphone and hydromorphone
• Lowest likelihood of causing vomiting
• Antagonist of the NMDA receptor
• Favorable for treating pain when central
  sensitization is present
• Can be given IV,IM,SC
• May last up to 4 hours

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OPIOIDS

• MEPERIDINE (or PETHIDINE) a synthetic opioid
  FULL AGONIST, primarily mu and delta receptor
• Weak analgesic properties lasting 1-2 hrs
• Short acting overall, up to 6 hrs
• Most useful as a part of the pre-anesthetic
  protocol

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OPIOIDS

• BUPRENORPHINE partial agonist of the mu
  receptor(aka bupi, buprenex)
• Delayed onset of action, (40 min IM) but longer
  duration of action than other opioids
  ___________
• Best used for mild to moderate pain
• The injectable product is effectively given to
  cats _____________________ (applied to the
  gingiva, under the tongue, in cheek pouch)
• Can be used to reverse the effects of pure
  agonists, while maintaining some analgesic
  effect. Not as effective as naloxone
• THIS DRUG IS PART OF THE VTI PROTOCOL FOR DOGS
  CATS

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OPIOIDS

• BUTORPHANOL mixed agonist(kappa,sigma)/antagonist
  (mu)(aka torb, torbugesic)
• Best used for mild to moderate pain and is
  commonly used as a ________________
• Can be used to reverse the effects of pure
  agonists. Not as effective as naloxone
• Commonly combined with a sedative such as
  dexmedetomidine or acepromazine
• MIXING AN OPIOID SEDATIVE IS KNOWN AS
  _____________________

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OPIOIDS

• TRAMADOL a non-opiate drug that has agonist
  activity at the mu receptor
• Oral tablets
• Useful post-operative pain med in dogs and cats
• Not currently controlled

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METHODS OF PAIN CONTROL USING MEDS

• NSAIDS

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NSAIDS

• MECHANISM OF ACTION
• Inhibits the synthesis of prostaglandins by
  blocking the enzyme cyclooxygenase ( aka
  COX-1 COX-2)
• ______ leads to the production of beneficial
  prostaglandins
• ________ leads to the production of harmful
  prostaglandins that are present during tissue
  damage and inflammation.

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NSAIDS

• BENEFITS OF NSAIDS
• No strict record keeping
• Little abuse potential
• Effective when given orally
• No sedative, cardiovascular, or respiratory
  effects
• Antipyretic effects
• SIDE EFFECTS/CAUTIONS
• GI upset/GI ulcers due to inhibition of
  __________
• DO NOT USE CONCURRENTLY w/ ___________
• ______ toxicity due to inhibition of PGE2
• hepatic toxicity
• Inhibits platelet aggregation due to blockage of
  ______________

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NSAIDS

• RIMADYL (carprofen)
• Approved for use in DOGS ONLY!
• Oral(chewable tablets) and injectable forms
  available
• Less likely to cause side effects mentioned
  previously due to its COX-2 selectivity
• Common uses
• Post-operative pain relief
• Pain relief from osteoarthritis and other
  musculoskeletal injuries
• PART OF THE CANINE POST-OP PAIN CONTROL PROTOCOL
  AT VTI

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NSAIDS

• METACAM (meloxicam)
• Approved for use in dogs and cats
• COX-2 selective
• Oral and injectable formulations available
• PART OF FELINE POST-OP PAIN CONTROL PROTOCOL AT
  VTI

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NSAIDS

• ONSIOR (Robenacoxib)
• Cox-2 selective
• Oral tablets approved for use in cats only
• Approved for use in dogs in other countries
• Given SID

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METHODS OF PAIN CONTROL USING MEDS

• OTHERS
• ALPHA-2 AGONISTS
• KETAMINE

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ALPHA-2 AGONISTS KETAMINE

• ALPHA-2 AGONISTS (ex dexdomitor, xylazine)
• Short duration of action (90 minutes)
• Also causes profound sedation, bradycardia
• Commonly combined with butorphanol
• Reversible (analgesic effects are reversed as
  well)
• KETAMINE
• Works by antagonizing ____________receptors in
  the spinal cord
• Blocking NMDA receptors prevents central
  sensitization windup
• Effective for _________analgesia, but limited
  visceral analgesia
• Duration of action is short 30min

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METHODS OF PAIN CONTROL USING MEDS

• LOCAL ANESTHETICS

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LOCAL ANESTHETICS

• WHAT IS LOCAL ANESTHESIA/ANALGESIA?
• The use of a chemical agent on sensory neurons to
  produce a disruption of nerve impulse
  transmission, leading to temporary loss of
  sensation

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LOCAL ANESTHETICS

• CHARACTERISTICS OF LOCAL ANESTHETICS
• Exert their effects on neurons in the peripheral
  nervous system and spinal cord that control pain,
  heat, cold, pressure
• Relatively few effects of the cardiovascular and
  respiratory systems
• Exert their effects in the area closest to the
  site of injection
• Not normally transferred across the placenta
• Safe for c-sections

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LOCAL ANESTHETICS

• ROUTES OF ADMINISTRATION
• TOPICAL must penetrate the epidermis to reach
  the dermis where the peripheral nerves are
  located
• Sprayed on intact skin for superficial procedures
  such as skin biopsies (ex ethyl chloride)
• Creams can also be applied to desensitize skin
  for superficial minor procedures (ex
  lidocaine/prilocaine)
• Splash blocks refer to the use of sprays or
  anesthetic soaked gauze sponges on open wounds or
  surgical sites
• Applied through a chest tube in patients having
  thoracic surgery
• Should be done when patient is awake
• Absorbed through the mucous membranes (larynx,
  eye, urethra)
• Short duration of action and less pain relief
  when compared to other routes of administration
  of local anesthetics

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LOCAL ANESTHETICS

• ROUTES OF ADMINISTRATION
• INFILTRATION(injection)
• Local anesthetic can be injected subcutaneously,
  intradermally, or between muscle planes
• Ideally the site of injection is clipped and
  cleaned
• Small needle (23-25 gauge) used to prevent tissue
  damage
• Test efficacy by pricking the site with a needle
• Do not inject into infected or inflamed tissues
• Some local anesthetic drugs are combined with
  epinephrine
• Epinephrine causes vasoconstriction which
  decreases rate of absorption and prolonging
  effect
• It also decreases the amount of drug entering the
  circulation, decreasing chances of toxicity.
• CAUTION AROUND AN INCISION OR ON EXTREMITIES AND
  WITH PATIENTS WITH CV ABNORMALITIES

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LOCAL ANESTHETICS

• ROUTES OF ADMINISTRATION
• _________ BLOCKS Injection of a local anesthetic
  in the proximity of a specific nerve to
  desensitize a specific anatomic location.
  Location of target nerve must be known and
  palpated if possible.
• Lameness exams in horses
• Cornual blocks for dehorning cattle
• Dental blocks in dogs and cats
• Infiltration of nerves during amputation of a
  limb
• Declawing cats
• May take 15-20 minutes for absorption
• Nerve blocks include ________ blocks and ______
  blocks

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Cornual blocks for dehorning cattle
THIS NERVE BLOCK IS ALSO A RING BLOCK
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Dental blocks for tooth extractions
Maxillary Nerve block via The infraorbital foramen
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NERVE BLOCKS
Nerve blocks help pinpoint areas of pain
Paravertebral block
THESE ARE EXAMPLES OF LINE BLOCKS
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NERVE BLOCKS
THIS NERVE BLOCK IS ALSO A RING BLOCK
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LOCAL ANESTHETICS

• ROUTES OF ADMINISTRATION
• NERVE BLOCKS
• LINE BLOCKS continuous line of local anesthetics
  placed SQ in an area served by numerous small
  nerves
• The needle is inserted along the line of
  infiltration and the anesthetic is injected as
  the needle is withdrawn
• If placed encircling an anatomic part, it is
  called a RING BLOCK
• _________________ injecting local anesthetics
  directly into a joint usually after surgery of
  the joint, immediately after closure of the joint
  capsule

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LOCAL ANESTHETICS

• ROUTES OF ADMINISTRATION
• ____________ blockage of sensory and motor
  nerves in the rear, abdomen, pelvis, tail, hind
  limbs, and perineum
• Anesthetist must be familiar with the anatomy of
  the terminal spinal cord and lumbosacral vertebrae

Epidural space
Dura mater
arachnoid
Subarachnoid space w/CSF
Pia mater
Spinal cord
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LOCAL ANESTHETICS

• EPIDURALS

http//www.youtube.com/watch?vzmwvMHZG_5g
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SIDE EFFECTS OF LOCAL ANESTHETICS

• Allergy
• Rash or hives in the area
• Systemic toxicity
• Sedation, nausea, restlessness,
  hyperexcitability, seizures, respiratory
  suppression, coma
• Infection (esp. w/epidurals)
• Cranial infiltration of an epidural may cause
  serious toxicity, respiratory suppression
• death

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METHODS OF PAIN CONTROL
Combining drugs from different categories
(multi-modal therapy, balanced analgesia) is more
beneficial than using high doses of one
medication. Pain is alleviated via different
pathways
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SPECIAL TECHNIQUES

• NEUROMUSCULAR BLOCKING AGENTS
• MECHANICAL VENTILATION

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NEUROMUSCULAR BLOCKING AGENTS

• Aka muscle-paralyzing agents
• These agents act by interrupting normal
  transmission of impulses from motor neurons to
  the muscle synapse
• Site of action ________ _______________, where
  acetylcholine is released by the neurons to
  attach to muscle end plates.

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NEUROMUSCULAR BLOCKING AGENTS

• Two ways for these agents to disrupt the nervous
  transmission
• _________________ agents cause a single surge
  of activity at the neuromuscular junction,
  followed by a refractory period. (Ex
  succinylcholine)
• Animals may show spontaneous muscle twitching
  followed by paralysis
• Reversal agents are not effective
• _________________ agents- block the receptors and
  the end plate. (ex pancuronium, atracurium)
• No initial surge of activity at the neuromuscular
  junction, no spontaneous muscle movements.
• These agents can be reversed with neostigmine or
  edrophonium
• Not commonly used in vet med, but can be useful
  in the following situations.

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NEUROMUSCULAR BLOCKING AGENTS

• Neuromuscular blocking agents allow relaxation
  of voluntary muscles only. Skeletal muscles are
  affected in a predictable order
• 1st- __________________
• 2nd- __________________
• Last- __________________
• ADMINISTRATION
• Normally given slowly IV
• Onset of action 2 minutes
• Duration 10-30 minutes
• Animals on these drugs will require manual or
  mechanical ventilation
• ADVERSE EFFECTS
• Hypothermia
• Respiratory failure
• Cardiac arrhythmias

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MECHANICAL VENTILATION

• Patients breathing is controlled by a ________
  rather than _____________________
• The ventilator automatically compresses a
  bellows, which forces oxygen and anesthetic gas
  into the patients airways
• The bellows is compressed at a specified rate and
  a specified volume
• USES not normally used in healthy anesthetized
  patients, but can be helpful in

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MECHANICAL VENTILATION
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MECHANICAL VENTILATION

• Depending on the type of ventilator, the
  anesthetist can deliver gases according to a
  pressure cycle, a volume cycle, or a time cycle.
• ________ cycle supplies air until the pressure
  reaches a preset level. This is generally 12 cm
  to 20 cm.
• ________ cycle supplies air according to a set
  inspiratory time. This is generally 1 to 1.5
  seconds.
• IE ratio is 12 to 13
• __________cycle delivers a preset tidal volume
  regardless of the pressure required. This is
  generally 10-15 mL/kg

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MECHANICAL VENTILATION

• RISKS OF CONTROLLED VENTILATION
• Excessive airway pressure may rupture alveoli
• Cardiac output may be decreased if positive
  pressure is maintained throughout inspiration and
  expiration
• If ventilation rate is too high, excessive carbon
  dioxide may be exhaled leading to respiratory
  alkalosis
• Controlled ventilation is generally more
  efficient at delivering anesthetic gas which may
  lead to exacerbation of side effects such as
  hypotension and CNS depression.
• Anesthetist may be tempted to relax on the
  monitoring