MODULE 2: PREOPERATIVE ASSESSMENT & PREMEDICATION

Q21: What are the aims of preoperative assessment?

Answer:Aims of Preoperative Assessment:

1. Risk Stratification:

   • Assess surgical and anesthetic risk
   • Identify high-risk patients
   • Optimize medical conditions

2. Patient Optimization:

   • Stabilize medical conditions
   • Adjust medications
   • Plan perioperative management

3. Informed Consent:

   • Explain anesthetic procedures
   • Discuss risks and benefits
   • Obtain legal consent

4. Anesthetic Planning:

   • Choose appropriate technique
   • Plan monitoring requirements
   • Anticipate complications

5. Patient Education:

   • Explain fasting guidelines
   • Discuss postoperative expectations
   • Address patient concerns

6. Resource Planning:

   • Allocate appropriate personnel
   • Plan ICU/HDU requirements
   • Schedule elective procedures

Q22: What are the aims of premedication?

Answer:Aims of Premedication:

1. Anxiolysis:

   • Reduce preoperative anxiety
   • Provide psychological comfort
   • Improve patient cooperation

2. Analgesia:

   • Reduce preoperative pain
   • Decrease intraoperative anesthetic requirements
   • Improve pain thresholds

3. Amnesia:

   • Produce anterograde amnesia
   • Reduce traumatic memories
   • Improve patient satisfaction

4. Autonomic Stability:

   • Reduce sympathetic stimulation
   • Prevent reflex responses
   • Maintain hemodynamic stability

5. Gastric Emptying:

   • Reduce gastric volume
   • Increase gastric pH
   • Decrease aspiration risk

6. Prophylaxis:

   • Prevent nausea and vomiting
   • Reduce infection risk
   • Prevent allergic reactions

7. Smooth Induction:

   • Facilitate smooth induction
   • Reduce emergence phenomena
   • Improve recovery quality

Q23: What are the different types of premedication?

Answer:Types of Premedication:

1. Benzodiazepines (Most Common):

• Diazepam: 5-10 mg PO/IV
• Lorazepam: 1-2 mg PO/IV
• Midazolam: 0.05-0.1 mg/kg PO/IV/IM

2. Opioids:

• Morphine: 0.1-0.2 mg/kg IM
• Meperidine: 1-2 mg/kg IM
• Fentanyl: 1-2 mcg/kg IV

3. Anticholinergics:

• Atropine: 0.02 mg/kg IV
• Glycopyrrolate: 0.01 mg/kg IV

4. Antihistamines:

• Promethazine: 0.5-1 mg/kg
• Diphenhydramine: 25-50 mg

5. Antacids:

• Ranitidine: 150-300 mg PO
• Omeprazole: 20-40 mg PO

6. Antiemetics:

• Ondansetron: 4-8 mg IV
• Dexamethasone: 4-8 mg IV

Q24: Mention the properties and uses of midazolam

Answer:Midazolam Properties:

Pharmacokinetics:

• Onset: 1-3 minutes IV, 10-15 minutes IM
• Peak Effect: 3-5 minutes IV
• Duration: 15-30 minutes IV
• Half-life: 2-3 hours (metabolites longer)
• Metabolism: Hepatic via CYP3A4
• Excretion: Renal

Advantages:

• Water-soluble (no pain on injection)
• Rapid onset and offset
• Predictable effects
• Reversible with flumazenil
• Minimal cardiovascular effects

Uses:

1. Premedication: 0.05-0.1 mg/kg PO/IV/IM
2. Induction: 0.2-0.3 mg/kg IV
3. Sedation: 0.025-0.1 mg/kg IV
4. Procedural Sedation: Small incremental doses
5. Amnesia: 1-2 mg IV before procedure

Side Effects:

• Respiratory depression (dose-dependent)
• Hypotension (rare)
• Prolonged sedation in elderly
• Paradoxical reactions (rare)

Q25: Mention the properties and uses of morphine

Answer:Morphine Properties:

Pharmacokinetics:

• Onset: 5-10 minutes IV, 30-60 minutes IM
• Peak Effect: 20 minutes IV, 60-90 minutes IM
• Duration: 3-4 hours
• Half-life: 2-3 hours
• Metabolism: Hepatic (morphine-6-glucuronide active)
• Excretion: Renal

Advantages:

• Excellent analgesic
• Produces euphoria
• Antitussive effect
• Reduces anesthetic requirements
• Long duration of action

Uses:

1. Premedication: 0.1-0.2 mg/kg IM
2. Intraoperative: 0.1 mg/kg IV bolus
3. Postoperative: 0.02-0.05 mg/kg IV/IM
4. Severe Pain: 2-10 mg IV/IM
5. Myocardial Infarction: 2-8 mg IV

Side Effects:

• Respiratory depression
• Nausea and vomiting
• Pruritus
• Constipation
• Urinary retention
• Miosis

Q26: Mention the properties and uses of fentanyl

Answer:Fentanyl Properties:

Pharmacokinetics:

• Onset: 30-60 seconds IV, 7-15 minutes IM
• Peak Effect: 5 minutes IV, 30 minutes IM
• Duration: 30-60 minutes
• Half-life: 2-4 hours
• Metabolism: Hepatic (norfentanyl inactive)
• Excretion: Renal

Advantages:

• Potent analgesic (100x morphine)
• Rapid onset
• Minimal cardiovascular effects
• No histamine release
• Short duration of action

Uses:

1. Premedication: 1-2 mcg/kg IV
2. Induction: 3-5 mcg/kg IV
3. Maintenance: 1-3 mcg/kg bolus or infusion
4. Analgesia: 0.5-2 mcg/kg IV
5. Transdermal: 25-100 mcg/hr patches

Side Effects:

• Respiratory depression
• Chest wall rigidity (high doses)
• Nausea and vomiting
• Pruritus
• Bradycardia

Q27: What are the indications and contraindications for regional anesthesia?

Answer:Indications for Regional Anesthesia:

Patient Factors:

• High risk for general anesthesia
• Patient preference
• Severe respiratory disease
• History of difficult intubation
• Obesity

Surgical Factors:

• Lower abdominal surgery
• Lower extremity surgery
• Urological procedures
• Gynecological procedures
• Ambulatory surgery

Medical Benefits:

• Better pain control
• Reduced postoperative nausea
• Early mobilization
• Cost-effective

Contraindications for Regional Anesthesia:

Absolute Contraindications:

• Patient refusal
• Infection at puncture site
• Coagulopathy (relative for some blocks)
• Increased intracranial pressure (spinal/epidural)
• Allergy to local anesthetics

Relative Contraindications:

• Sepsis
• Hypovolemia
• Neurological disease
• Multiple sclerosis
• Severe aortic stenosis
• Uncooperative patient

Q28: What are the side effects of spinal anesthesia?

Answer:Side Effects of Spinal Anesthesia:

Common Side Effects:

1. Hypotension (60-90% of patients)

   • Due to sympathetic blockade
   • Treat with IV fluids and vasopressors

2. Nausea and Vomiting (20-30%)

   • Secondary to hypotension
   • Treat underlying hypotension

3. Shivering (10-20%)

   • Thermoregulatory response
   • Treat with warming

4. Headache (1-5%)

   • Post-dural puncture headache
   • Due to CSF leak

Less Common Side Effects:

1. High Spinal Block

   • Respiratory depression
   • Cardiovascular collapse

2. Urinary Retention

   • Bladder dysfunction
   • More common in males

3. Back Pain

   • Local trauma at puncture site
   • Usually temporary

4. Infection

   • Meningitis (rare)
   • Epidural abscess (rare)

Neurological Complications:

• Transient neurological symptoms
• Cauda equina syndrome (very rare)
• Permanent neurological damage (rare)

Q29: Write the properties of etomidate

Answer:Etomidate Properties:

Pharmacokinetics:

• Onset: 30-60 seconds
• Duration: 3-5 minutes
• Half-life: 1-3 hours
• Metabolism: Hepatic hydrolysis
• Excretion: Renal

Cardiovascular Effects:

• Minimal cardiovascular depression
• Maintains blood pressure and heart rate
• Preserves baroreceptor reflexes
• Ideal for hemodynamically unstable patients

Respiratory Effects:

• Mild respiratory depression
• Less than propofol or thiopentone
• Maintains hypoxic ventilatory response

Neurological Effects:

• Reduces cerebral metabolic rate
• Decreases intracranial pressure
• Preserves cerebral blood flow
• Neuroprotective properties

Advantages:

1. Cardiovascular stability
2. Rapid onset and offset
3. Smooth induction
4. Minimal respiratory depression
5. Antiemetic properties

Disadvantages:

1. Myoclonus (30-80%)
2. Pain on injection
3. Adrenal suppression
4. Vomiting

Uses:

• Induction in unstable patients
• Cardiac surgery
• Neurosurgery
• Septic shock

Q30: What are the properties and uses of propofol?

Answer:Propofol Properties:

Pharmacokinetics:

• Onset: 30-40 seconds IV
• Duration: 3-8 minutes
• Half-life: 2-24 hours (context-sensitive)
• Metabolism: Hepatic (inactive metabolites)
• Excretion: Renal

Advantages:

1. Rapid onset and offset
2. Smooth induction
3. Antiemetic properties
4. Clear-headed recovery
5. Reduces intracranial pressure
6. Short context-sensitive half-time

Disadvantages:

1. Cardiovascular depression
2. Respiratory depression
3. Pain on injection
4. Hypotension

Uses:

1. Induction: 2-2.5 mg/kg IV
2. Maintenance: 100-200 mcg/kg/min infusion
3. Sedation: 25-75 mcg/kg/min
4. Procedural sedation: Intermittent bolus

Cardiovascular Effects:

• Decreases blood pressure (10-20%)
• Reduces systemic vascular resistance
• Minimal effect on heart rate

Respiratory Effects:

• Dose-dependent respiratory depression
• Apnea common after induction
• Decreases ventilatory response to CO2

Q31: What are the properties of sevoflurane?

Answer:Sevoflurane Properties:

Physical Properties:

• MAC: 1.8-2.0% in oxygen
• Blood:Gas Partition Coefficient: 0.65
• Vapor Pressure: 160 mmHg @ 20°C
• Molecular Weight: 200 g/mol

Pharmacokinetics:

• Low solubility → rapid induction and emergence
• Quick equilibration between alveoli and brain
• Minimal metabolism (<5%)
• Excreted unchanged via lungs

Cardiovascular Effects:

• Minimal myocardial depression
• Maintains cardiac output
• Causes peripheral vasodilation
• Rarely arrhythmias

Respiratory Effects:

• Respiratory irritant: minimal
• Bronchodilator properties
• Decreases airway resistance
• Facilitates mask ventilation

Neurological Effects:

• Reduces cerebral metabolic rate
• Maintains cerebral blood flow
• Reduces intracranial pressure
• Seizure threshold: controversial

Advantages:

1. Rapid induction and emergence
2. Pleasant odor
3. Cardiovascular stability
4. Bronchodilation
5. Low solubility

Disadvantages:

1. Expensive
2. May trigger malignant hyperthermia
3. Potential nephrotoxicity (compound A)
4. Hypotension

Q32: What are the properties of isoflurane?

Answer:Isoflurane Properties:

Physical Properties:

• MAC: 1.15-1.5% in oxygen
• Blood:Gas Partition Coefficient: 1.4
• Vapor Pressure: 240 mmHg @ 20°C
• Molecular Weight: 184 g/mol

Pharmacokinetics:

• Moderate solubility → intermediate onset/offset
• Minimal metabolism (<0.2%)
• Primarily excreted via lungs
• No toxic metabolites

Cardiovascular Effects:

• Myocardial depression: moderate
• Decreases systemic vascular resistance
• Maintains heart rate or causes mild tachycardia
• Coronary steal: minimal

Respiratory Effects:

• Respiratory irritant
• Decreases tidal volume
• Increases respiratory rate
• Maintains hypoxic drive

Neurological Effects:

• Increases cerebral blood flow
• Increases intracranial pressure
• Contraindicated in raised ICP
• Provides good muscle relaxation

Advantages:

1. Cardiovascular stability
2. Cost-effective
3. Low toxicity
4. Good muscle relaxation
5. Predictable effects

Disadvantages:

1. Pungent odor (irritating)
2. Slower emergence than sevoflurane
3. Increases ICP
4. Can cause breath-holding

Uses:

• General maintenance
• Cardiac surgery (in low concentrations)
• Neurosurgery (avoided due to ICP effects)

Q33: Write about desflurane

Answer:Desflurane Properties:

Physical Properties:

• MAC: 6-7% in oxygen
• Highest volatility of all inhalational agents
• Blood:Gas Partition Coefficient: 0.42
• Vapor Pressure: 669 mmHg @ 20°C
• Requires special vaporizer

Pharmacokinetics:

• Lowest solubility → fastest emergence
• Rapid equilibration between compartments
• Minimal metabolism (<0.02%)
• Primarily excreted unchanged

Cardiovascular Effects:

• Tachycardia: may cause
• Increases blood pressure (low concentrations)
• Decreases systemic vascular resistance
• Coronary steal potential

Respiratory Effects:

• Respiratory irritant
• Cough and breath-holding common
• Increases respiratory rate
• Decreases tidal volume
• May trigger laryngospasm

Neurological Effects:

• Maintains cerebral blood flow
• Minimal intracranial effects
• Provides excellent muscle relaxation
• Fastest emergence of all agents

Advantages:

1. Fastest emergence and recovery
2. Precise control of anesthetic depth
3. Low metabolism
4. Minimal cardiac depression

Disadvantages:

1. Expensive
2. Respiratory irritant
3. Requires special vaporizer
4. Tachycardia and hypertension (may occur)

Uses:

• Long procedures requiring rapid emergence
• Ambulatory surgery
• Neurosurgery (minimal ICP effects)
• Cardiac surgery (cautiously)

Q34: What are the side effects of morphine?

Answer:Side Effects of Morphine:

Central Nervous System:

1. Respiratory Depression (most serious)

   • Dose-dependent
   • May persist postoperatively
   • Naloxone reversal if severe

2. Sedation and Drowsiness

   • Common side effect
   • More pronounced in elderly

3. Nausea and Vomiting

   • Chemoreceptor trigger zone stimulation
   • Antiemetics may be needed

4. Pruritus

   • Histamine release
   • More common with morphine than synthetic opioids

5. Mood Changes

   • Euphoria or dysphoria
   • Confusion in elderly

Cardiovascular:

1. Hypotension

   • Histamine release
   • May cause bradycardia

2. Bradycardia

   • Vagal stimulation

Gastrointestinal:

1. Constipation

   • Most common side effect
   • Requires prophylactic management

2. Biliary Spasm

   • Increases intracholedochal pressure
   • May mask biliary colic

Genitourinary:

1. Urinary Retention

   • Increased sphincter tone
   • More common in males

2. Reduced Libido

   • Hormonal effects

Other Effects:

• Miosis (pinpoint pupils)
• Cough Suppression
• Physical Dependence (chronic use)
• Tolerance (with repeated use)

Q35: What is MAC?

Answer:MAC (Minimum Alveolar Concentration):

Definition: The minimum alveolar concentration of an inhalational anesthetic that prevents movement in 50% of patients in response to a standardized surgical stimulus (skin incision).

Clinical Significance:

1. Potency Measure: Higher MAC = less potent
2. Dose Relationship: Multiple of MAC determines depth
3. Drug Comparison: Allows comparison between agents
4. Clinical Guidance: Helps determine delivery rates

MAC Values in 100% Oxygen:

• Desflurane: 6-7%
• Sevoflurane: 1.8-2.0%
• Isoflurane: 1.15-1.5%
• Halothane: 0.75%
• Nitrous Oxide: 105%

Factors Affecting MAC:

Increases MAC:

• Hyperthermia
• Chronic alcohol use
• Chronic amphetamine use
• Thyrotoxicosis
• Increased catecholamines

Decreases MAC:

• Age: Every decade reduces MAC by 6-10%
• Hypothermia
• Pregnancy
• Hypotension
• Acute alcohol intoxication
• Opioids and sedatives
• Alpha-2 agonists

MAC-BAR: Minimum alveolar concentration that blocks autonomic responses in 50% of patients (usually 1.3-1.5 × MAC)

MAC-AWAKE: Minimum alveolar concentration at which 50% of patients respond to verbal command (usually 0.3-0.5 × MAC)

Q36: What are the contraindications for regional anesthesia?

Answer:Contraindications for Regional Anesthesia:

Absolute Contraindications:

1. Patient Refusal

   • Cannot obtain informed consent
   • No alternatives available

2. Infection at Site

   • Risk of spreading infection
   • Epidural abscess risk
   • Meningitis risk

3. Coagulopathy

   • INR >1.5 (spinal/epidural)
   • Platelet count <80,000/μL
   • Bleeding diatheses

4. Increased Intracranial Pressure

   • Spinal/epidural contraindicated
   • Risk of herniation

5. Local Anesthetic Allergy

   • True IgE-mediated allergy
   • Cross-reactivity concerns

Relative Contraindications:

1. Sepsis/Infection

   • Risk of bacteremia
   • Potential for abscess formation

2. Hypovolemia

   • Sympathetic blockade effects
   • Severe hypotension risk

3. Neurological Disease

   • Multiple sclerosis
   • Myasthenia gravis
   • Poliomyelitis
   • May mask new deficits

4. Severe Aortic Stenosis

   • Fixed cardiac output
   • Cannot tolerate decreased SVR

5. Uncooperative Patient

   • Cannot remain still
   • Agitation/restlessness

6. Severe Deformity

   • Anatomical landmarks obscured
   • Increased technical difficulty

Procedure-Specific Contraindications:

• Spinal/Epidural: Coagulopathy, infection, raised ICP
• Upper Extremity Blocks: Infection, lymphadenopathy
• Paravertebral Blocks: Coagulopathy, infection

Q37: Write about the side effects of spinal anesthesia

Answer:Side Effects of Spinal Anesthesia:

Hypotension (Most Common - 60-90%):

• Mechanism: Sympathetic blockade → vasodilation
• Treatment:
  • IV crystalloids (500-1000 mL)
  • Vasopressors (ephedrine 5-10 mg, phenylephrine 50-100 mcg)
  • Leg elevation
  • Left uterine displacement (pregnancy)

Nausea and Vomiting (20-30%):

• Cause: Hypotension → cerebral hypoxia
• Treatment: Treat underlying hypotension
• Prophylaxis: Adequate hydration, avoid hypotension

Shivering (10-20%):

• Mechanism: Thermoregulatory response
• Treatment:
  • Warming (forced air blankets)
  • Warm IV fluids
  • Meperidine if severe

Post-Dural Puncture Headache (1-5%):

• Cause: CSF leak through puncture site
• Characteristics:
  • Positional (worse upright)
  • Frontal/occipital location
  • Associated with neck stiffness
• Treatment:
  • Conservative (hydration, caffeine)
  • Epidural blood patch if severe

High Spinal Block:

• Symptoms:
  • Dyspnea/breathing difficulty
  • Loss of consciousness
  • Cardiovascular collapse
• Treatment:
  • Airway management
  • Vasopressors for hypotension
  • Supportive care

Neurological Complications:

• Transient Neurological Symptoms (TNS):
  • Back pain, buttock pain
  • Radiation to legs
  • Usually self-limiting
• Cauda Equina Syndrome (Rare):
  • Saddle anesthesia
  • Bowel/bladder dysfunction
  • Permanent if not treated

Other Side Effects:

• Urinary Retention: Bladder dysfunction
• Back Pain: Local tissue trauma
• Infection: Meningitis, epidural abscess (rare)

Q38: What is the difference between spinal and epidural anesthesia?

Answer:Differences between Spinal and Epidural Anesthesia:

Aspect	Spinal Anesthesia	Epidural Anesthesia
Anatomy	Dura mater punctured	Dura mater NOT punctured
Needle	22-27 gauge, pencil point	16-18 gauge, Tuohy needle
Injection Site	Subarachnoid space	Epidural space
Drug Volume	2-4 mL	10-20 mL
Onset	Rapid (1-5 minutes)	Slower (10-20 minutes)
Density	Dense block	Less dense block
Spread	Gravity-dependent	Segmental
Duration	2-4 hours	3-6 hours
Test Dose	Not required	Essential (3 mL lidocaine)

Advantages of Spinal:

• Rapid onset
• Dense block
• Reliable
• Less drug required
• No test dose needed

Advantages of Epidural:

• Can be titrated
• Catheter can be placed
• Longer duration possible
• Can be used for postoperative pain
• Less risk of PDPH

Complications:

Spinal:

• Post-dural puncture headache (1-5%)
• High spinal (rare)
• Neurological damage (rare)
• Infection (rare)

Epidural:

• Inadequate block (10-15%)
• Dural puncture (1-5%)
• Local anesthetic toxicity
• Catheter-related problems

Combined Spinal-Epidural (CSE):

• Benefits of both techniques
• Rapid onset with catheter for supplementation

Q39: What are the properties and uses of midazolam?

Answer:Midazolam Properties:

Physical Properties:

• Water-soluble (no pain on injection)
• pH-dependent lipid solubility
• Benzodiazepine structure

Pharmacokinetics:

• Onset: 1-3 minutes IV, 10-15 minutes IM
• Peak Effect: 3-5 minutes IV
• Duration: 15-30 minutes IV
• Half-life: 2-3 hours (parent), 1-10 hours (metabolites)
• Metabolism: Hepatic via CYP3A4
• Excretion: Renal

Pharmacodynamics:

• Binds to GABA-A receptors
• Enhances GABA inhibitory effects
• Anxiolytic, sedative, amnestic
• Anticonvulsant properties
• Muscle relaxant effects

Advantages:

1. Water-soluble (no injection pain)
2. Rapid onset and offset
3. Predictable effects
4. Reversible with flumazenil
5. Minimal cardiovascular effects
6. Good oral bioavailability (40-50%)

Disadvantages:

1. Respiratory depression (dose-dependent)
2. Hypotension (rare)
3. Prolonged sedation in elderly
4. Paradoxical reactions (rare)
5. Accumulates with repeated doses

Uses:

Premedication:

• Dose: 0.05-0.1 mg/kg PO/IV/IM
• Route: PO (preferred for children), IV, IM

Induction:

• Dose: 0.2-0.3 mg/kg IV
• Often combined with other agents

Procedural Sedation:

• Dose: 1-2 mg IV bolus
• Redosing: 0.5-1 mg as needed

Reversal:

• Flumazenil: 0.2 mg IV (repeat to max 1 mg)

Special Populations:

• Elderly: Start with 50% dose
• Renal failure: No adjustment needed
• Liver failure: Prolonged effects

Q40: What are the properties and uses of fentanyl?

Answer:Fentanyl Properties:

Chemical Structure:

• Synthetic opioid (phenylpiperidine derivative)
• Highly lipophilic
• PKa: 8.4

Pharmacokinetics:

• Onset: 30-60 seconds IV, 7-15 minutes IM
• Peak Effect: 5 minutes IV, 30 minutes IM
• Duration: 30-60 minutes (bolus), 60-120 minutes (higher doses)
• Half-life: 2-4 hours (context-sensitive: up to 16 hours)
• Volume of Distribution: 4 L/kg
• Protein Binding: 84%
• Metabolism: Hepatic (norfentanyl inactive)
• Excretion: Renal (75% as metabolites)

Pharmacodynamics:

• μ-opioid receptor agonist
• 100x more potent than morphine
• Analgesic, sedative, respiratory depressant
• Minimal histamine release
• Rapid CNS penetration

Advantages:

1. Potent analgesic effect
2. Rapid onset
3. Short duration (bolus dosing)
4. Minimal cardiovascular effects
5. No histamine release
6. Transdermal formulation available

Disadvantages:

1. Chest wall rigidity (high doses/rapid administration)
2. Respiratory depression
3. Bradycardia
4. Nausea and vomiting
5. Accumulates with prolonged infusion

Uses:

Premedication:

• Dose: 1-2 mcg/kg IV
• Provides analgesia and sedation

Induction:

• Dose: 3-5 mcg/kg IV
• Blunts hemodynamic response to intubation

Maintenance:

• Dose: 1-3 mcg/kg bolus
• Infusion: 0.02-0.1 mcg/kg/min

Procedural Analgesia:

• Dose: 0.5-2 mcg/kg IV
• Bronchoscopy, endoscopy

Transdermal:

• Patches: 25-100 mcg/hr
• For chronic cancer pain

Special Formulations:

• Sublingual: For breakthrough pain
• Nasal: For pediatric use
• Lollipop: For pediatric premedication

Reversal:

• Naloxone: 0.4-2 mg IV (titrate to effect)

Side Effects:

• Respiratory depression
• Chest wall rigidity
• Bradycardia
• Nausea/vomiting
• Pruritus
• Miosis