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