Anesthesia
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GENERAL ANESTHETIC MASTER TABLE
| Drug | Main mechanism | ⭐ Classic association |
|---|---|---|
| Propofol | ↑ GABA-A | Rapid recovery + hypotension |
| Etomidate | ↑ GABA-A | ⭐ Adrenal suppression |
| Ketamine | NMDA antagonist | ⭐ ↑ BP + analgesia + emergence reactions |
| Thiopental | GABA-A | Porphyria |
| Sevoflurane | Volatile anesthetic | ⭐ Smooth inhalational induction |
| Desflurane | Volatile anesthetic | ⭐ Rapid recovery |
| Isoflurane | Volatile anesthetic | Vasodilation/hypotension |
| Nitrous oxide | Inhaled anesthetic/analgesic | ⭐ B12 + closed-space expansion |
| Dantrolene | ↓ SR Ca²⁺ release | ⭐ Malignant hyperthermia |
General anesthesia
General anesthetics produce reversible unconsciousness and other components of anesthesia, such as amnesia and immobility.
Inhalational agents
| Drug | Key feature | Important adverse effect |
|---|---|---|
| Nitrous oxide | Analgesic, relatively weak anesthetic | Diffusion hypoxia after discontinuation; expands gas-filled spaces |
| Isoflurane | Potent volatile anesthetic | Hypotension |
| Sevoflurane | Common inhalational induction/maintenance agent | Hypotension; possible emergence agitation |
| Desflurane | Rapid adjustment and emergence | Airway irritation |
| Halothane | Historical anesthetic | Hepatotoxicity and arrhythmia risk |
Intravenous agents
| Drug | Main action/use | Important adverse effect |
|---|---|---|
| Propofol | Rapid induction; antiemetic effect | Hypotension and respiratory depression |
| Etomidate | Induction with relative cardiovascular stability | Adrenal steroid synthesis suppression |
| Ketamine | NMDA receptor antagonist; dissociative anesthesia | Emergence reactions, increased secretions, often increased heart rate/BP |
| Thiopental | Barbiturate induction agent | Respiratory and cardiovascular depression |
| Midazolam | Benzodiazepine; sedation and amnesia | Respiratory depression, especially with opioids |
Neuromuscular blockers
These agents interfere with neuromuscular transmission and are used to facilitate intubation and surgery. They do not themselves provide analgesia or unconsciousness.
| Drug | Type | Key point |
|---|---|---|
| Succinylcholine | Depolarizing | Rapid onset; hyperkalemia and malignant hyperthermia risk |
| Rocuronium | Nondepolarizing | Reversible with sugammadex in appropriate settings |
| Vecuronium | Nondepolarizing | Relatively cardiovascular stable |
| Atracurium | Nondepolarizing | Hofmann elimination and ester hydrolysis |
| Cisatracurium | Nondepolarizing | Organ-independent Hofmann elimination is clinically useful |
Succinylcholine — classic adverse effects
- Hyperkalemia.
- Malignant hyperthermia in susceptible patients.
- Bradycardia in selected settings.
- Prolonged paralysis with reduced butyrylcholinesterase activity.
- Increased intraocular or intragastric pressure may occur.
MCQ tip: Malignant hyperthermia is treated with dantrolene.
Local anesthetics
Local anesthetics reversibly block voltage-gated sodium channels, preventing action-potential propagation along nerves.
Classification
| Class | Examples | Hint |
|---|---|---|
| Amides | Lidocaine, mepivacaine, bupivacaine, prilocaine, ropivacaine | Amides contain 2 ‘I’ in their name |
| Esters | Procaine, chloroprocaine, tetracaine, benzocaine |
Pharmacology
| Feature | Amides | Esters |
|---|---|---|
| Main metabolism | Hepatic metabolism | Usually plasma pseudocholinesterases |
| Allergy | True allergy uncommon | PABA-related allergy more likely with some agents |
| Examples | Lidocaine, bupivacaine | Procaine, benzocaine |
Vasoconstrictors
Epinephrine is added to many local anesthetic formulations to:
- Reduce systemic absorption.
- Prolong anesthesia.
- Improve local hemostasis.
- Reduce peak systemic concentrations.
Local anesthetic toxicity
Early manifestations may include circumoral numbness, metallic taste, tinnitus, agitation or seizures. Severe toxicity can cause arrhythmias, cardiovascular collapse and cardiac arrest.
Management requires stopping administration, airway and cardiovascular support, seizure treatment and lipid emulsion therapy when indicated.
Dental local anesthetic dose calculations
The following are commonly taught reference limits; follow the specific product label and local guidance.
| Agent | Common maximum-dose reference |
|---|---|
| Lidocaine with epinephrine | 7 mg/kg, generally maximum 500 mg |
| Lidocaine without epinephrine | 4.5 mg/kg, generally maximum 300 mg |
| Mepivacaine | Maximum depends on formulation and local product guidance |
| Bupivacaine | Lower maximum dose; high concern for cardiac toxicity |
| Prilocaine | Dose limited by methemoglobinemia risk |
Dental exam tip: Always consider both the maximum local anesthetic dose and the maximum epinephrine dose, especially in patients with cardiovascular disease.