Anesthesia Principles for Surgeons

Pre-op Assessment & Risk - Setting the Stage

• ASA Physical Status Classification:

  Status	Description
  ASA I	Normal healthy patient
  ASA II	Mild systemic disease
  ASA III	Severe systemic disease
  ASA IV	Severe systemic disease, constant threat to life
  ASA V	Moribund, not expected to survive without operation
  ASA VI	Declared brain-dead, organ donor
  E	Emergency procedure

• Pre-anesthetic Evaluation:

  • Focused Hx: Allergies, medications, prior anesthesia Hx, comorbidities.
  • Airway Assessment (📌 LEMON mnemonic for difficult airway):
    • Mallampati score.
    • Thyromental distance (>6.5 cm).
    • Inter-incisor gap (>3 cm).
    • Neck mobility.

⭐ NPO guidelines are crucial to prevent aspiration:

• Clear liquids: 2 hrs.
• Breast milk: 4 hrs.
• Light meal/Infant formula: 6 hrs.
• Fatty/fried meal: 8 hrs.

• Informed Consent: Essential for anesthesia plan and risks discussion.

Types of Anesthesia - Pick Your Potion

• General Anesthesia (GA): Reversible loss of consciousness.
  • Phases: Induction, Maintenance, Emergence.
  • Total Intravenous Anesthesia (TIVA): GA using IV agents only.
• Regional Anesthesia: Numbs a larger body area.
  • Spinal: Injection into subarachnoid space (L3-L4/L4-L5). Agents: Bupivacaine. Baricity affects spread. Complications: Hypotension, Post-Dural Puncture Headache (PDPH).
  • Epidural: Catheter in epidural space. Advantage: Prolonged post-op analgesia.
• Local Anesthesia (LA): Numbs a small, specific area.
  • Mechanism: Blocks Na+ channels.
  • Types: Amides (Lignocaine, Bupivacaine), Esters (Procaine).
  • Max Doses: Lignocaine (plain 3-5 mg/kg; +adrenaline 7 mg/kg). Bupivacaine (plain 2-2.5 mg/kg).
  • Toxicity: 📌 SAMS: Slurred speech, Altered mental status, Muscle twitching, Seizures.
• Monitored Anesthesia Care (MAC): Sedation with local anesthesia; patient responsive.

⭐ Spinal anesthesia commonly uses hyperbaric Bupivacaine; post-dural puncture headache (PDPH) is a known complication, often managed conservatively or with an epidural blood patch.

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Types of Anesthesia - Pick Your Potion

• General Anesthesia (GA): Reversible unconsciousness. Phases: Induction, Maintenance, Emergence. TIVA option.
• Regional Anesthesia:
  • Spinal: Subarachnoid injection (L3-L5). Agent: Bupivacaine. Complications: Hypotension, PDPH.
  • Epidural: Catheter for prolonged analgesia.
• Local Anesthesia (LA): Na+ channel blockade.
  • Amides (Lignocaine, Bupivacaine), Esters (Procaine).
  • Max Doses: Lignocaine (plain 3-5 mg/kg; +adrenaline 7 mg/kg). Bupivacaine (plain 2-2.5 mg/kg).
  • Toxicity: 📌 SAMS (Slurred speech, Altered mental status, Muscle twitching, Seizures).
• Monitored Anesthesia Care (MAC): Sedation + LA.

⭐ Spinal: Hyperbaric Bupivacaine common. PDPH risk; manage conservatively or blood patch.

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Airway Management & Drugs - Breath & Beyond

• Basic Airway:
  • Maneuvers: Head-tilt/chin-lift, jaw thrust.
  • Devices: OPA, NPA (unconscious, no gag), LMA (supraglottic), ETT (definitive airway).
• RSI (Rapid Sequence Intubation): Full stomach/aspiration risk. Steps: Preoxygenate, cricoid pressure, induction, paralysis, intubate.
• IV Anesthetics:
  • Propofol: SE: hypotension, apnea.
  • Etomidate: CVS stable.
  • Ketamine: Dissociative, bronchodilation, analgesia. SE: emergence delirium.
• Inhalational: Sevoflurane, Desflurane, Isoflurane (MAC = potency). N2O (second gas effect).
• Muscle Relaxants:
  • Succinylcholine (Depolarizing): SE: hyperkalemia, fasciculations, MH trigger.
  • Rocuronium, Vecuronium (Non-depolarizing): Reverse: Neostigmine/Glycopyrrolate or Sugammadex.

⭐ Malignant Hyperthermia: Rare; due to succinylcholine/inhalational agents. Treat: Dantrolene 2.5 mg/kg IV.

Intra-op Monitoring & Complications - Crisis Control

• Standard ASA Monitoring: ECG, NIBP, SpO2, EtCO2 (ETT, ventilation), Temp.

  ⭐ Capnography (EtCO2): Most reliable for ETT confirmation & ventilation adequacy.

• Common Complications:
  • Hypotension: Causes (drugs, blood loss, sympathetic block). Mgmt: Fluids, vasopressors.
  • Hypoxia: Causes (airway, breathing, circulation). Mgmt: 100% O2, ABCs.
  • Anaphylaxis: Signs (↓BP, bronchospasm, rash). Mgmt: Adrenaline 0.3-0.5 mg IM/IV, fluids, steroids, antihistamines.
• Malignant Hyperthermia (MH):
  • Triggers: Succinylcholine, volatile anesthetics.
  • Signs: Early (↑EtCO2, tachycardia, rigidity); Late (hyperthermia, rhabdomyolysis).
  • Mgmt: Stop triggers, 100% O2 hyperventilation, Dantrolene 2.5 mg/kg IV (repeat PRN), cooling, treat acidosis/hyperK+.

• Awareness under anesthesia: Rare; risk factors (paralysis, difficult intubation).

High‑Yield Points - ⚡ Biggest Takeaways

• ASA classification predicts perioperative risk.
• Mallampati score assesses airway; higher scores mean difficult intubation.
• Malignant hyperthermia (MH), triggered by succinylcholine/volatiles, is treated with dantrolene.
• Propofol is a common IV anesthetic; ketamine provides analgesia and cardiovascular stability.
• Spinal anesthesia: local anesthetic into subarachnoid space for rapid onset.
• Local Anesthetic Systemic Toxicity (LAST): manage with IV lipid emulsion.
• Rapid Sequence Intubation (RSI) for full stomach patients prevents aspiration_._