Essential drugs in surgery ward pharmacology practical
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Essential Drugs in Surgery Ward - Pharmacology Practical
This covers the drugs you need to know for a surgery ward pharmacology practical, organized by clinical phase and category.
1. PREOPERATIVE MEDICATIONS (Premedication)
A. Anxiolytics / Sedatives - Benzodiazepines
Midazolam (most commonly used)
- Route: Oral (0.5 mg/kg in children 30 min before induction), IV (1-2 mg in adults)
- Actions: Anxiolytic, amnestic, sedative - these three effects make it the most popular preoperative drug
- Onset is rapid; causes anterograde amnesia (patient does not remember pre-op events)
- More rapid onset and greater amnesia than diazepam, with less postoperative sedation
- Reversal: Flumazenil (8-15 mcg/kg IV, but brief action ~20 min, watch for resedation)
Diazepam
- Oral premedication; longer acting than midazolam
- Pain on IV injection due to poor water solubility (requires organic solvent)
"The amnestic, anxiolytic, and sedative effects of benzodiazepines make this class of drugs the most popular choice for preoperative medication." - Katzung's Basic and Clinical Pharmacology, 16e
B. Anticholinergics
Atropine
- 0.6 mg IM given 45-60 min before surgery
- Uses: Reduces oral/airway secretions (antisialagogue), prevents vagal bradycardia during intubation/surgery, reduces acid secretion
- Side effects: Tachycardia, dry mouth, blurred vision, urinary retention
Glycopyrrolate
- Better antisialagogue; does NOT cross blood-brain barrier (no central effects)
- Fewer cardiac side effects compared to atropine
C. H2-Blockers / Antacids (Aspiration Prophylaxis)
Ranitidine (or omeprazole/pantoprazole)
- Given night before and morning of surgery
- Reduces gastric acid volume and pH, lowering risk of Mendelson's syndrome (aspiration pneumonitis)
Sodium citrate (0.3 M)
- Non-particulate antacid given immediately before emergency surgery
- Rapidly neutralizes gastric acid
2. INDUCTION AGENTS
| Drug | Dose (IV) | Key Feature |
|---|---|---|
| Propofol | 1.5-2.5 mg/kg | Most widely used; rapid onset + offset; antiemetic at sub-anesthetic doses; causes pain on injection |
| Thiopental (Thiopentone) | 3-5 mg/kg | Rapid onset barbiturate; historical gold standard; causes precipitate with succinylcholine if mixed |
| Ketamine | 1-2 mg/kg IV / 4-6 mg/kg IM | Dissociative anesthetic; maintains airway reflexes + BP; causes emergence delirium; drug of choice in hypovolemic shock |
| Etomidate | 0.3 mg/kg | Minimal hemodynamic effects; drug of choice in cardiovascular compromise; inhibits 11-beta-hydroxylase (adrenal suppression with prolonged use) |
3. NEUROMUSCULAR BLOCKING AGENTS (Muscle Relaxants)
Depolarizing
Succinylcholine (Suxamethonium)
- 1-1.5 mg/kg IV
- Fastest onset and shortest duration; used for rapid sequence intubation (RSI)
- Mimics ACh at nicotinic receptors; causes fasciculations before paralysis
- Contraindicated in: burns, crush injury, hyperkalemia, myopathies, malignant hyperthermia susceptibility
- Reversal: NOT reversible with neostigmine; wait for spontaneous recovery (pseudocholinesterase)
Non-depolarizing
| Drug | Duration | Notes |
|---|---|---|
| Atracurium | Intermediate | Hofmann elimination (safe in renal/hepatic failure); histamine release |
| Vecuronium | Intermediate | No histamine release; no cardiovascular effects |
| Rocuronium | Intermediate | Fastest onset of non-depolarizers; used for modified RSI; reversed by sugammadex |
| Pancuronium | Long | Tachycardia; avoid in cardiac disease |
Reversal: Neostigmine (0.05 mg/kg) + Atropine (0.02 mg/kg) or Glycopyrrolate
4. INHALATIONAL ANESTHETICS
| Agent | Key Properties |
|---|---|
| Isoflurane | Most commonly used; minimal cardiac depression; airway irritant |
| Sevoflurane | Pleasant smell; used for mask induction (especially children); rapid onset/offset |
| Desflurane | Fastest washout; irritant to airways; not used for induction |
| Nitrous oxide (N2O) | Used as adjunct (50-70%); analgesic, amnestic, second gas effect; diffuses into air-filled cavities |
5. ANALGESICS
Opioids
| Drug | Route/Dose | Notes |
|---|---|---|
| Morphine | 0.1-0.2 mg/kg IM/IV | Gold standard opioid; histamine release; constipation; respiratory depression; used in post-op pain infusions (0.5 mg/kg in 50 mL NS at 1-3 mL/hr in children) |
| Pethidine (Meperidine) | 1 mg/kg IM | Shorter acting; toxic metabolite (norpethidine) causes seizures; avoid in MAOIs |
| Fentanyl | 1-2 mcg/kg IV | 100x more potent than morphine; intraoperative analgesia |
| Tramadol | 50-100 mg oral/IV | Mild-moderate pain; dual mechanism (opioid + SNRI); less respiratory depression |
Reversal: Naloxone (0.4-2 mg IV) - reverses opioid-induced respiratory depression
NSAIDs
| Drug | Dose | Notes |
|---|---|---|
| Diclofenac | 75 mg IM / 50 mg oral | Post-op pain; avoid in renal impairment, bleeding risk |
| Ketorolac | 15-30 mg IM/IV | Only parenteral NSAID commonly used; max 5 days |
| Ibuprofen | 400-600 mg oral | Step-down analgesia |
Paracetamol (Acetaminophen)
- 1 g IV/oral q6h (adult); mainstay of multimodal analgesia
- Safe; no opioid side effects; synergistic with opioids and NSAIDs
- Children: 120 mg (under 1 year), 240 mg (1-5 years)
6. ANTIEMETICS (PONV Prophylaxis and Treatment)
| Drug | Class | Dose | Notes |
|---|---|---|---|
| Ondansetron | 5-HT3 antagonist | 4-8 mg IV | First-line PONV; no sedation |
| Metoclopramide | D2 antagonist | 10 mg IV/oral | Prokinetic; extrapyramidal side effects with high doses |
| Promethazine | Antihistamine | 12.5-25 mg IM | Sedating; good antiemetic |
| Dexamethasone | Steroid | 4-8 mg IV | Excellent PONV prophylaxis, adjunct analgesic |
| Droperidol | Butyrophenone | 0.625-1.25 mg IV | Effective but QT prolongation risk |
7. ANTIBIOTICS (Surgical Prophylaxis)
Principles:
- Given within 60 minutes before skin incision (30 min for fluoroquinolones)
- Covers the most likely organisms for that surgery type
- Single dose usually sufficient; redose if surgery >4 hours
| Surgery Type | Drug of Choice |
|---|---|
| Clean (e.g. hernia) | Cefazolin 1-2 g IV |
| Colorectal/GI | Cefazolin + Metronidazole |
| Biliary | Cefazolin or Cefuroxime |
| Appendicectomy | Cefazolin + Metronidazole |
| Amoxicillin allergy | Clindamycin or Vancomycin |
8. FLUIDS AND ELECTROLYTES
- Normal saline (0.9% NaCl): Standard resuscitation fluid; risk of hyperchloremic acidosis
- Ringer's Lactate (Hartmann's): Balanced crystalloid; preferred for large-volume resuscitation
- Colloids (Albumin, Gelofusine): Volume expansion; used when crystalloids insufficient
- Dextrose 5%: Maintenance fluid; NOT for resuscitation (distributes to ICF)
9. ANTICOAGULANTS
| Drug | Use |
|---|---|
| Heparin (LMWH - Enoxaparin) | DVT prophylaxis post-surgery; 40 mg SC OD |
| Unfractionated heparin | Intraoperative anticoagulation (cardiac, vascular surgery); 5000 IU SC BD for DVT prophylaxis |
| Warfarin | Long-term anticoagulation post-surgery (bridged with heparin) |
| Reversal - Protamine sulfate | Reverses heparin (1 mg per 100 IU heparin) |
10. DRUGS FOR SPECIAL SURGICAL SITUATIONS
Hemostatic Agents
- Tranexamic acid (TXA): Antifibrinolytic; 1 g IV over 10 min before surgery; reduces blood loss significantly
- Adrenaline (Epinephrine) 1:200,000: Added to local anesthetic to cause vasoconstriction, prolonging block and reducing systemic absorption
Local Anesthetics
| Drug | Duration | Notes |
|---|---|---|
| Lignocaine (Lidocaine) | Short-intermediate | 4-7 mg/kg without adrenaline; 7 mg/kg with; also used IV for arrhythmia |
| Bupivacaine | Long (4-8 hrs) | 0.25-0.5%; spinal, epidural, nerve blocks; cardiotoxic in overdose |
| Ropivacaine | Long | Less cardiotoxic than bupivacaine; preferred for epidurals |
Toxicity Rescue: Intralipid (20%) 1.5 mL/kg IV bolus for severe local anesthetic systemic toxicity (LAST)
Vasopressors/Inotropes
| Drug | Use |
|---|---|
| Adrenaline (Epinephrine) | Anaphylaxis (0.5 mg IM), cardiac arrest |
| Noradrenaline | Septic shock vasopressor |
| Ephedrine | Spinal/epidural-induced hypotension (6-9 mg IV boluses) |
| Phenylephrine | Pure alpha-agonist for spinal hypotension |
Antidotes
| Scenario | Drug |
|---|---|
| Opioid overdose | Naloxone 0.4-2 mg IV |
| Benzodiazepine overdose | Flumazenil 0.2 mg IV |
| Organophosphate poisoning | Atropine (large doses) + Pralidoxime |
| Heparin overdose | Protamine |
| Malignant hyperthermia | Dantrolene 2.5 mg/kg IV |
QUICK REVISION TABLE - High-Yield for Practicals
| Category | Drug | Key Point |
|---|---|---|
| Premedication | Midazolam | Anxiolytic + amnestic; most popular premedic |
| Induction | Propofol | Rapid offset; antiemetic; pain on injection |
| Induction (shock) | Ketamine | Maintains BP; dissociative; emergence delirium |
| Depolarizing NMB | Succinylcholine | Fastest onset; fasciculations; K+ risk |
| Non-depolarizing | Rocuronium | Reversed by sugammadex |
| NMB reversal | Neostigmine + Atropine | Always combine with anticholinergic |
| Analgesia | Morphine | Gold standard opioid; watch respiratory depression |
| Opioid reversal | Naloxone | 0.4-2 mg IV; short-acting |
| PONV | Ondansetron | 5-HT3; first-line; no sedation |
| Prophylactic ABX | Cefazolin | Given 60 min before incision |
| DVT prophylaxis | Enoxaparin | 40 mg SC OD; start 12h post-op |
| Hemostasis | Tranexamic acid | Reduces surgical blood loss |
| Local anesthetic | Bupivacaine | Long-acting; cardiotoxic in overdose |
| Antichol. (preop) | Atropine | Dries secretions; prevents bradycardia |
| Spinal hypotension | Ephedrine | Maintains BP after spinal anesthesia |
Sources: Katzung's Basic and Clinical Pharmacology, 16e | Pye's Surgical Handicraft, 22e | Morgan and Mikhail's Clinical Anesthesiology, 7e | Miller's Anesthesia, 10e
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