ANESTHESIA 101 Surgery Core program Nov 4, 2008 Desiree Persaud MD FRCPC Associate Professor University of Ottawa Regional Anesthesia Director, The Ottawa Hospital Resident Coordinator, Dept of Anesthesiology The Ottawa Hospital Civic/Riverside
Jan 04, 2016
ANESTHESIA 101Surgery Core program Nov 4, 2008
Desiree Persaud MD FRCPC
Associate Professor University of Ottawa
Regional Anesthesia Director, The Ottawa Hospital
Resident Coordinator, Dept of Anesthesiology
The Ottawa Hospital Civic/Riverside Campus
Overview History Anesthetic principles Case presentations
Surgery prior to Anesthesia The last resort Medieval torture chamber –
restraints/gags Physical assault: blow to the jaw Ice: freezing/conduction anesthesia Plants: marijuana, belladonna Alcohol, opium Hypnosis, distraction
Anesthesia 1846: ether anesthesia
Who are we and what do we do? Perioperative acute care physicians Perioperative pain management experts 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 Interventional anesthesiology – TEE, TTE, U/S guided
nerve blocks/line placement, flouroscopic chronic pain blocks,
Definition Anesthesia: Greek: 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
Awake Unconscious
General Anesthesia
Awake Unconscious
Suppression of consciousness with profound systemic effects
Lipid theory
Protein theory
x Not an On/Off Switch
General Anesthesia - continuedX 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
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
Spinal
Pros: Quick onset Dense surgical anesthesia
Cons: Limited duration - < 4 hours Limited cephaled spread Rapid sympathectomy Limited post op analgesia
Epidural
Catheter placed – can extend duration of block Most often used in combo with GA Post-op analgesia Less need for systemic narcotic Bowel function preserved
Peripheral Nerve blocks Mainly for orthopedic and vascular surgery Unlike neuraxial—virtually no systemic side effects Provides site specific post-op analgesia
Patients/pathology come in different packages:
4 case presentations: same surgical pathology BUT 4 very different anesthetic plans!!
Case 1 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)
Pre-anesthetic assessment Assess level of hydration:
General anesthesia will depress CVS reflexes
Potential for hypotension Assess Airway – aspiration risk Assess for other comorbid conditions
Resp/CVS
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
Is an appendix always an appendix? Case 2: 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
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
Change approach to laparoscopic appendectomy?
Does it matter? Case 3: Laparoscopic approach
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
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,
Intraoperative management Fluid hydration key—reduction 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
Case 4: Change patient: morbidly obese for laparoscopic appendectomy BMI > 35 CNS: sensitive to depressants/apnea A/W: obstruction/difficult to secure Resp: restrictive defect/ PH CVS: HP, LVH, CAD GI: reflux Endo: DM
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
Emergence Reversal of anesthesia: just as risky as
induction Patients: responsive, protect A/W Stable: BP/temp Adequate reversal
Post-operative care Monitoring:
LOC/hemodynamic/O2saturation Pain control Nausea/Vomiting Ambulation/movement
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/hypothermia
Take home messages 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 Communication is KEY