ANESTHESIA 101

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ANESTHESIA 101

• Desiree Persaud MD FRCPC
• Assistant professor University of Ottawa
• Resident Coordinator
• Dept of Anesthesiology
• The Ottawa Hospital Civic Campus

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Overview

• History
• Facts/Fiction
• Case presentations

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Surgery prior to Anesthesia

• The last resort
• Medieval torture chamber restraints/gags
• Physical assault blow to the jaw
• Plants marijuana, belladonna
• Hypnosis, distraction
• Alcohol, opium

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Anesthesia

• 1846 ether anesthesia

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Definition
Awake
Unconscious

• Anesthesia No sensation
• Types Alone or in combo
• General anesthesia
• Neuraxial anesthesia
• Spinals and Epidurals lower extremity/bowel
  surgery
• Peripheral Nerve Blocks
• Paravertebral breast surgery
• Femoral - knee replacement/muscle biopsies

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Anesthetic principles

• Perioperative acute care physicians
• Direct manipulation of physiology
• Intricate knowledge of pharmacology
• Expert laryngoscopist/backup A/W methods
• Regional/invasive line placement/anatomy
  knowledge
• Equipment ventilators/monitors/gas delivery
  systems

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General Anesthesia

• x Not an On/Off Switch
• Suppression of consciousness with profound
  systemic effects
• Lipid theory
• Protein theory

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General Anesthesia - continued

• X Not going to sleep
• Is a chemically induced coma
• Direct CNS system depression
• Lack of A/W reflexes
• Depression of the respiratory centres
• Direct CVS depression
• Multiple pharmacologic effects influencing every
  system gut/liver/renal/endocrine/neuromuscular

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General Anesthesia - adjuncts

• Volatile agent the gas
• Potent CVS depressant
• No analgesic effects
• Nitrous Oxide
• Not very potent
• Distends spaces eg bowel
• Narcotics
• Potent RESP depressant
• PONV

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Adjuncts - continued

• Muscle relaxants
• Succinyl choline, rocuronium
• Block NMJ
• Skeletal muscle paralysis
• Problems
• Inability to reverse
• Awareness

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Adjuncts cont.

• Induction agents
• Propofol, pentothal, ketamine
• Narcotics
• Fentanyl, remifentanil
• Non-narcotic analgesics
• Ketorolac, lidocaine, magnesium
• Anti-emetics
• Dexamthasone, ondansetron

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Neuraxial anesthesia

• Neuraxis spinal cord
• Benefits
• No direct CNS, Resp, CVS depression
• No need for muscle relaxants
• Provides analgesia
• Problems
• SNS blockade hypotension
• Spinal hematoma - anticoagulants

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Spinal

• Pros
• Quick on set
• Dense surgical anesthesia
• Cons
• Limited duration - lt 4 hours
• Limited cephaled spread
• Rapid sympathectomy
• Limited post op analgesia

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Epidural

• Similar to spinals
• Longer onset
• Catheter placed can extend duration of block
• Most often used in combo with GA
• Post-op analgesia
• Superior bowel function preserved
• Less need for systemic narcotic

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Peripheral Nerve blocks

• Mainly for orthopedic and vascular surgery
• Unlike neuraxialvirtually no systemic side
  effects
• Provides superior post-op analgesia
• Takes time for placement and onset

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Pre-assessment consults

• Pts with Hx of difficult intubation
• Personal/Family Hx of anesthesia problems
• Pts with uncontrolled resp disease
• Pts with unstable coronary disease
• Endocrinopathies pheochromocytoma
• Pts on anticoagulants plavix/ticlid/LMWH

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Appendectomy

• 4 cases scenarios
• Patients/pathology come in different packages

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Cases

• 25 yr old male for open appendectomy
• Issues
• Emergency case
• Acute abdomen risk perforation/sepsis
• full stomach aspiration risk
• Dehydration Nausea and Vomiting
• General (or neuraxial anesthesia)

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Pre-anesthetic assessment

• Assess level of hydration
• General anesthesia will depress CVS reflexes
• Potential for hypotension
• Assess for other comorbid conditions
• Resp/CVS
• Assess Airway aspiration risk

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Intra-op management

• Functioning IV volume replacement
• Optimal airway positioning
• Rapid intubation with muscle relaxant and cricoid
  pressure
• Narcotic, IV induction agent, relaxant
• Maintain with volatile/narcotics
• Extubate reversed and awake

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Is an appendix always an appendix?

• Case Change age to 75 yr old male
• Additional issues
• Compensatory mechanisms less
• More likely to have resp/CVS comorbidities
• More sensitive to CNS depressants
• Less tolerance of physiologic stressors

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Intra-operative management

• IV fluids pre-op fluid hydration more careful
  and essential
• Monitors include ST seg monitoring
• Slow, titrated induction
• Minimize volatile predispose to hypotension
• Great risk of hypotension while the surgeon is
  scrubbing!!!
• Non-compliant vasculature rapid swings of BP
• Delayed emergence possible

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Change approach to laparoscopic appendectomy?
Does it matter?

• Laparoscopy
• Trocar vessel/viscous perforation
• Relaxation, large IV
• Pneumoperitoneum
• Restrictive resp defect high PAW, atelectasis
• Vagal efferent relfex
• Reduction in preload hypotension
• Incr gastric pressure aspiration risk
• S/C emphysema
• pneumothorax

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Laparoscopy considerations - cont.

• Carbon dioxide
• SNS stimulant ?BP, ? HR
• Pulmonary V/C predispose to PH
• Cerebral V/D ?ICP
• Acidosis ?K, enzyme dysfunction
• Embolus CV Collapse
• Positioning loss of Airway, lines,

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Intraoperative management

• Fluid hydration keyreduction in preload
• Trocar insertion must ensure patient does not
  move
• COMMUNICATE
• Difficulty with trocar insertion
• COMMUNICATE
• Avoid too high intrabdominal pressures
• Avoid too steep trendelenburg

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Change patient morbidly obese for laparoscopic
appendectomy

• BMI gt 35
• CNS sensitive to depressants/apnea
• A/W obstruction/difficult to secure
• Resp restrictive defect/ PH
• CVS HP, LVH, CAD
• GI reflux
• Endo DM

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Intraoperative management

• Meticulous airway positioning
• Prone to desaturation
• Trendelenburg poorly tolerated ventilatory
  difficulty atelectasis-shunting
• Pre-existing PH high CO2/low O2
• Delayed emergence
• Prolonged PACU/overnight stay

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Emergence

• Reversal of anesthesia just as risky as
  induction
• Patients responsive, protect A/W
• Stable BP/temp
• Adequate reversal

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Why are they so slow?

• Pre-operative assessment
• Difficult IV access MO, cancer pt
• Epidural/Spinal placement
• Difficult A/W positioning/adjuncts/awake
  intubation topicalizaton
• Hemodynamic instability BP, HR, rhythm
• Line placement CVP/A. line
• Delayed Emergence excess narcotics/relaxant/hypot
  hermia

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Post-operative care

• Monitoring
• LOC/hemodynamic/sats
• Pain control
• Nausea/Vomiting
• Ambulation/movement

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Take home message

• Anesthetics are tailored to both the patient and
  procedure
• Patients and procedures come in different
  packages
• General anesthesia is not an on/off switch
• General anesthesia is not going to sleep
• Multiple dynamic physiologic effects
• Time to induce/maintain/emerg
• Regional techniques have multiple advantages
• Communication is KEY