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Anaesthesia Comprehensive Review

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1. Resuscitation in Pregnant Women + Surviving Sepsis Guidelines

Physiological Adaptations Relevant to Resuscitation

• Aortocaval compression: From 20 weeks gestation, the gravid uterus compresses the IVC → reduced venous return → left lateral tilt 15–30° (wedge under right hip) is mandatory during CPR/resuscitation
• Airway: Oedematous, Mallampati increases, higher risk of aspiration (reduced LOS tone, delayed gastric emptying) → early RSI with cricoid pressure
• Respiratory: Increased O₂ consumption (20%), reduced FRC (20%) → desaturates faster; PaCO₂ normally 30 mmHg (respiratory alkalosis)
• Cardiovascular: CO increases 40–50%, HR +15–20 bpm, SVR falls; BP normally lower
• Blood: Dilutional anaemia (Hb ~11 g/dL), physiological hypercoagulability

Cardiac Arrest in Pregnancy — 4H4T + Perimortem Caesarean (PMCS)

Surviving Sepsis Campaign Guidelines (SSC 2021 — "Hour-1 Bundle")

Hour-1 Bundle (initiate within 1 hour of recognition)

1. Measure lactate (remeasure if >2 mmol/L)
2. Blood cultures ×2 (before antibiotics; don't delay antibiotics >45 min)
3. Broad-spectrum antibiotics within 1 hour
4. 30 mL/kg crystalloid IV if hypotensive or lactate ≥4 mmol/L
5. Vasopressors if MAP <65 mmHg during/after fluid — noradrenaline first-line

Additional SSC Targets

• MAP ≥65 mmHg
• ScvO₂ ≥70%, CVP 8–12 mmHg (or 12–15 if mechanically ventilated)
• Urine output ≥0.5 mL/kg/hr
• Glycaemic control: maintain blood glucose <10 mmol/L (180 mg/dL)
• Corticosteroids: Hydrocortisone 200 mg/day IV if vasopressor-refractory shock
• Lung-protective ventilation: Tidal volume 6 mL/kg IBW, Pplat <30 cmH₂O, PEEP as needed
• Prone ventilation ≥16 hours/day if PaO₂/FiO₂ <150

Sepsis in Pregnancy — Special Considerations

• Most common organisms: Group A Strep, E. coli, GBS
• Avoid aminoglycosides if possible (nephrotoxicity)
• Hydrocortisone safe in pregnancy
• Delivery may be required to treat source (chorioamnionitis)
• Normal WBC in pregnancy is 9,000–15,000 → sepsis harder to detect biochemically

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2. Liver Function Tests (LFTs) and Significance + Child-Pugh Score

LFTs and Clinical Significance

• Hepatocellular: ↑↑ ALT/AST, ↑ bilirubin, ↓ albumin, ↑ PT
• Cholestatic: ↑↑ ALP/GGT, ↑ bilirubin, normal/mild ↑ transaminases
• Synthetic failure: ↓ Albumin, ↑ INR/PT, ↑ bilirubin → suggests cirrhosis/acute liver failure

Anaesthetic Implications of LFT Abnormalities

• Coagulopathy: Fresh frozen plasma, vitamin K, platelet transfusion
• Hypoalbuminaemia: ↑ free fraction of protein-bound drugs (e.g. thiopental, benzodiazepines)
• Ascites: Risk of regurgitation, diaphragm splinting, ↓ FRC
• Hepatic encephalopathy: Avoid morphine, benzodiazepines
• Avoid: Halothane (hepatotoxic), NSAIDS (renal + GI effects)
• Drug metabolism: Reduced CYP450 activity → prolonged drug effects

Child-Pugh Score

Child-Pugh C patients are high surgical risk; elective surgery should be deferred. MELD score (Model for End-stage Liver Disease) is now preferred for transplant allocation.

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3. USG-Guided Adductor Canal Block + Renal Replacement Therapy

USG-Guided Adductor Canal Block (ACB)

• Sartorius muscle — medially
• Vastus medialis — anteriorly
• Adductor magnus & longus — posteriorly

1. Position: Supine, leg externally rotated, knee slightly flexed
2. Probe: High-frequency linear probe, transverse orientation, mid-thigh (halfway between ASIS and superior patellar pole)
3. Identify: Femoral artery (pulsatile), vein (compressible), sartorius muscle superficially; saphenous nerve lies anterior to the artery (hyperechoic structure)
4. Needle: In-plane technique, insert 2–3 cm lateral to probe, advance medially into the triangular space deep to sartorius, anterior to artery
5. Confirm: Negative aspiration, spread of LA around nerve/artery
6. Volume: 15–20 mL local anaesthetic (0.25–0.5% bupivacaine or 0.2% ropivacaine)

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Renal Replacement Therapy (RRT)

• A — Acidosis (metabolic, pH <7.1, refractory)
• E — Electrolyte disturbance (hyperkalaemia >6.5, refractory)
• I — Intoxication (dialysable toxins: lithium, salicylates, methanol, ethylene glycol, theophylline)
• O — Overload (fluid overload refractory to diuretics)
• U — Uraemia (uraemic pericarditis, encephalopathy, Urea >30 mmol/L)

• Better haemodynamic tolerance
• Gradual fluid removal avoids cerebral oedema
• Allows large volumes of IV drugs/nutrition

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4. Types of Labour Analgesia + Pain Pathway in Labour Pain

Pain Pathway in Labour

• Pain from uterine contractions and cervical dilation
• Transmitted via visceral afferents (C-fibres) → enter cord at T10–L1
• Travel with sympathetic fibres through uterine and cervical plexuses → inferior hypogastric plexus → lumbar sympathetic chain → thoracic sympathetic chain → spinal cord T10–L1

• Pain from perineal distension and vaginal/pelvic floor stretching
• Transmitted via somatic afferents (pudendal nerve, S2–4)
• Combined visceral (T10–L1) + somatic (S2–4) pain

Types of Labour Analgesia

1. Neuraxial (Regional) — Gold Standard

• Most commonly used; flexible
• Space: L2-3 or L3-4; loss of resistance technique
• Drug: Low-concentration bupivacaine (0.0625–0.1%) + fentanyl (2 µg/mL) or sufentanil
• Techniques: Continuous infusion (CEI), PCEA (patient-controlled epidural), PIEB (programmed intermittent epidural bolus — superior)
• Covers T10–L1 (1st stage) and S2–4 (2nd stage)
• Side effects: Hypotension (treat with IV fluids, vasopressors), motor block, PDPH (dural puncture headache), instrumental delivery rate

• Low-dose intrathecal: Bupivacaine 2.5 mg + fentanyl 25 µg
• Rapid onset but limited duration (1.5–2 hours); not preferred alone for labour

• Best of both: rapid onset of spinal + flexibility of epidural
• Needle-through-needle technique
• Intrathecal dose: bupivacaine 2.5 mg + fentanyl 25 µg
• Ideal for advanced labour or when rapid analgesia needed

• Epidural needle + deliberate dural puncture (without injection); enhances epidural spread
• Lower risk of PDPH than CSE

2. Systemic Opioid Analgesia

3. Inhaled Analgesia

• Entonox (50% N₂O + 50% O₂): Self-administered; onset in 30–45 seconds; partial, not complete analgesia; nausea
• Methoxyflurane (Penthrox): Inhaler device; effective, rapid onset

4. Regional Nerve Blocks

• Pudendal nerve block: 2nd stage/instrumental delivery; 10 mL 1% lignocaine at ischial spine bilaterally; covers S2–4 (perineum only)
• Paracervical block: Covers cervical afferents T10–L1; risk of fetal bradycardia (vasoconstriction of uterine artery); largely abandoned
• Lumbar sympathetic block: Covers 1st stage (T10–L1) via bilateral L2–3 block

5. Non-Pharmacological

• Hydrotherapy, TENS, massage, acupuncture, hypnobirthing — limited but real analgesic effect

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5. Anaesthesia Challenges & Management of Posterior Fossa Tumour

Challenges

• Sitting position (most common for posterior fossa): Risk of Venous Air Embolism (VAE) — most dangerous complication; also risk of paradoxical air embolism if PFO present (check with bubble echo preop)
• Other positions: Prone (Concorde), lateral, park-bench
• Sitting position: Also risks pneumocephalus, haemodynamic instability, quadriplegia from neck flexion (≥2 finger-breadths between chin and chest)

• Posterior fossa tumours → hydrocephalus (4th ventricle obstruction)
• Manage: Head up 30°, avoid hypercapnia (PaCO₂ 34–38 mmHg), avoid hypoxia, judicious fluids (isotonic solutions, avoid glucose), mannitol 0.5–1 g/kg, dexamethasone

• Risk highest in sitting position (surgical site above heart level)
• Detection (in order of sensitivity): TOE > precordial Doppler > capnography (ETCO₂ drop) > pulmonary artery catheter > CVP > clinical signs
• Management of VAE: Flood field with saline, N₂O off immediately, left lateral Trendelenburg (Durant manoeuvre), aspiration via CVP catheter, vasopressors, CPR if cardiac arrest

• Risk of intraoperative injury to V, VI, VII, IX, X, XI, XII
• Neuromonitoring: SSEP (somatosensory evoked potentials), BAEP (brainstem auditory), MEP (motor), facial nerve EMG — requires TIVA (avoid volatile agents which suppress evoked potentials)

• Air enters cranial vault during surgery; worsens with N₂O (enlarges air pockets) → avoid N₂O in sitting craniotomy; use TIVA

Anaesthesia Management

• Review MRI, assess ICP signs (headache, vomiting, papilloedema)
• Neurological baseline
• Steroids (dexamethasone 4–8 mg q6h) pre-operatively
• Consent for sitting position: Doppler + CVC placement

• TIVA preferred (propofol + remifentanil infusion) — maintains neurological monitoring
• Avoid ketamine (increases ICP)
• Smooth induction: Prevent coughing/straining → IV lidocaine 1.5 mg/kg or remifentanil bolus before laryngoscopy
• Hyperventilate mildly (PaCO₂ 34–36 mmHg)

• TIVA (propofol + remifentanil) if neuromonitoring in use
• Or low-dose volatile (<0.5 MAC) + opioid if monitoring not required
• Glucose-free isotonic fluids; avoid hypo-osmolar solutions
• Maintain MAP 60–90 mmHg; cerebral perfusion pressure >60 mmHg

• Arterial line (BP beat-to-beat), CVC (VAE aspiration catheter at cavoatrial junction), ETCO₂, precordial Doppler, BIS/depth of anaesthesia, neuromonitoring probes, temperature

• Avoid hypovolaemia before sitting (leg elevation, sequential compression devices)
• Precordial Doppler or TOE in place before positioning
• Adequate neck flexion check (2-finger breadth chin-chest distance)

• Awake extubation preferred (assess neurological status)
• ICU/HDU
• Dexamethasone continued
• Monitor for: haematoma, pneumocephalus, cranial nerve deficits, hydrocephalus, cerebellar oedema
• Tension pneumocephalus → causes "Mount Fuji sign" on CT → neurosurgical emergency

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6. Airway Management of Maxillofacial Trauma + Manual Inline Stabilisation (MILS)

Challenges in Maxillofacial Trauma Airway

• Distorted anatomy: Fractures (Le Fort I/II/III, mandibular, zygomatic), oedema, haematoma → difficult laryngoscopy
• Blood in airway: Clots, active haemorrhage obscure the view
• Trismus: Limited mouth opening
• Aspiration risk: Blood, secretions, gastric contents (full stomach)
• Associated C-spine injury: ~2–5% of maxillofacial trauma; assume C-spine injury until cleared
• Unstable fractures: Mid-face fractures may allow inadvertent passage of instruments into cranial vault (cribriform plate breach)

Approach

• Check SpO₂, airway patency, respiratory rate
• GCS, C-spine status, facial anatomy
• Airway predictors: Blood, trismus, facial swelling, ability to open mouth, Mallampati (if possible), neck mobility

• Scalpel–bougie technique (preferred over needle): vertical skin incision → horizontal stab into CTM → bougie insertion → tube railroaded
• Cannula cricothyroidotomy (4 mm kink-resistant catheter) as bridge

Manual Inline Stabilisation (MILS)

1. A second operator stands to the side facing the patient's head
2. Hands placed on mastoid processes (not mandible) and occiput — bilateral grip
3. Applies gentle, firm counter-force against head/neck movement during laryngoscopy
4. Does NOT improve the laryngoscopic view — may actually worsen glottic view (by preventing atlanto-occipital extension)
5. Neutral position maintained, not immobilisation — allows mouth to open

• Remove collar, apply MILS
• Preoxygenate (high-flow O₂ 3 min or 8 vital capacity breaths)
• Induction: Ketamine 1.5 mg/kg or thiopentone 3–5 mg/kg + suxamethonium 1.5 mg/kg
• Sellick's manoeuvre (cricoid pressure) if aspiration risk
• Video laryngoscopy preferred (GlideScope, C-MAC)
• Have surgical airway immediately available

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7. Anaesthesia Management of a 2-Year-Old with Foreign Body (Emergency)

Preoperative Assessment

• Nature, size, shape of foreign body (FB); when ingested
• Airway vs oesophageal FB (stridor, wheeze, drooling vs dysphagia)
• Last oral intake (full stomach — emergency)
• Symptoms: Respiratory distress, cyanosis, drooling, complete vs partial obstruction

• SpO₂ on room air, RR, work of breathing, air entry
• Stridor (inspiratory = supraglottic; expiratory = subglottic/tracheal; biphasic = fixed obstruction)
• Signs of complete obstruction (silent chest, cyanosis) → immediate intervention

• CXR (inspiratory/expiratory): Air trapping, hyperinflation, mediastinal shift (ball-valve FB in bronchus)
• Lateral neck X-ray (radio-opaque FB)
• CT scan if needed

Anaesthetic Challenges in a 2-Year-Old

• Small airway → easy obstruction
• High O₂ consumption → rapid desaturation
• Small functional residual capacity
• Uncooperative
• Full stomach
• Risk of pushing FB further or dislodging during induction

Anaesthetic Management

• Senior anaesthetist, ENT surgeon scrubbed and ready, paediatric resuscitation equipment
• Airway trolley: Range of ETT (uncuffed 4.5 for 2-year-old; ID = age/4 + 4 = 4.5), bronchoscopes (rigid + flexible), laryngoscopes (straight blade Miller 1–2)
• Drugs: Atropine (0.02 mg/kg IV, minimum 0.1 mg — prevent bradycardia), induction agents
• IV access established (EMLA cream)

• Gaseous induction with 100% O₂ + sevoflurane if IV access not established (maintains spontaneous ventilation, less likely to dislodge FB)
• OR IV induction if IV access in place and child stable:
  • Propofol 2–3 mg/kg + dexamethasone 0.15 mg/kg (airway oedema)
  • Avoid suxamethonium if partial obstruction (loss of tone → complete obstruction risk — controversial; use clinical judgement)
  • Atropine before induction (bradycardia with sevo/rigid scope)

• Rigid bronchoscopy (ENT/paediatric surgeons): For subglottic/tracheal/bronchial FB — maintain spontaneous or controlled ventilation through side port of bronchoscope
• Direct laryngoscopy for supraglottic/laryngeal FB
• Topical lignocaine on larynx (1 mg/kg max) to reduce laryngospasm

• Spontaneous ventilation preferred for airway FB (reduces risk of complete obstruction with positive pressure)
• TPPR (Total intravenous + preserve respiration): Propofol + dexmedetomidine/remifentanil infusion
• If IPPV needed: Low tidal volume, watch for air trapping

• If complete obstruction: Back blows/chest thrusts (Paediatric BLS), emergency laryngoscopy
• CICO: Needle cricothyroidotomy in child <12 years, jet ventilation
• Post-extraction: Check for second FB, mucosal oedema (nebulised adrenaline 0.5 mL of 1:1000)

• Extubate awake, upright
• Observe for laryngospasm, bronchospasm, oedema
• Dexamethasone 0.15–0.3 mg/kg reduces post-extubation stridor
• Nebulised adrenaline if stridor present

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8. Biochemical Changes in Stored Blood + Indications & Complications of Blood Transfusion

Biochemical Changes in Stored Blood

Indications for Blood Transfusion

• Hb <7 g/dL (stable non-cardiac patients) — Restrictive trigger (TRICC criteria)
• Hb <8 g/dL in cardiac surgery, ACS, orthopaedic surgery
• Hb <10 g/dL in symptomatic patients (angina, dyspnoea, tachycardia)
• Acute haemorrhage with haemodynamic instability (Class III/IV shock)
• Symptomatic anaemia regardless of Hb level

• PT/APTT >1.5× normal with active bleeding
• Massive transfusion (1:1:1 ratio with RBCs:FFP:Platelets in military/trauma protocols)
• Reversal of warfarin in emergency
• DIC
• TTP (plasma exchange)

• Plt <10 × 10⁹/L (prophylactic)
• Plt <50 × 10⁹/L with active bleeding or surgery
• Plt <100 × 10⁹/L for neurosurgery/ophthalmic surgery

• Fibrinogen <1.5 g/L with bleeding
• Haemophilia A, vWD, hypofibrinogenaemia, DIC

Complications of Blood Transfusion

• DHTR (Delayed Haemolytic): Non-ABO antibodies; mild, self-limited
• TRALI (can be late)
• Post-transfusion purpura: Platelet antibody, day 5–10
• Graft-vs-Host Disease (TA-GvHD): Immunocompromised patients; fatal; prevent with irradiated blood
• Infection: HIV, Hep B, Hep C, CMV, variant CJD, bacterial contamination (platelets at room temp → highest bacterial risk)
• Iron overload: Repeated transfusions → haemosiderosis (chelation therapy)
• Immunosuppression: Transfusion-related immunomodulation (TRIM)

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9. Link 25 + Electrical Safety in the Operating Theatre

LINK 25 (Isolated Power Supply System)

• Standard grounded electrical systems: Any single fault can complete a circuit via earth → person touching live equipment is electrocuted (macroshock)
• Isolated power system: The power supply transformer secondary winding is not connected to earth → a single fault to ground causes NO shock and no circuit breaker trip (power continues — essential in OT)
• The LIM continuously monitors for total hazard current between isolated line conductors and earth

• When first fault occurs → LIM alarm activates (Link 25 panel shows alarm) but power NOT interrupted
• This alerts staff to find and remove faulty equipment before a second fault creates a complete circuit
• If a second fault occurs → circuit IS completed → shock hazard
• LIM alarm threshold: 5 mA hazard current (some systems 2 mA)

• When Link 25 alarms → do not panic; power continues
• Systematically identify and unplug equipment one by one until alarm clears
• The last device unplugged is the faulty one

Electrical Safety in the Operating Theatre

Types of Electric Shock

Classification of OT Electrical Zones

• Zone 1: General patient environment — standard safety
• Zone 2: Cardiac procedures — isolated power supply, extra protection (IEC 60364-7-710)
• All equipment must be Type CF (cardiac float protection) for procedures with intracardiac connection

Equipment Classifications

Diathermy Safety

• Monopolar diathermy: Current enters via active electrode → disperses through body → exits via large patient plate (return electrode)
  • Plate must have full contact (burns if partial contact → current density ↑)
  • Avoid placing over bony prominences, scar tissue, implants
  • Interference with pacemakers → use bipolar diathermy or use asynchronous pacing mode
• Bipolar diathermy: Current flows between two tips; localised; safer for cardiac devices and small structures
• Capacitive coupling: In laparoscopy → current through insulation of laparoscopic instruments → bowel/vessel injury

Fire Triangle in OT

• Oxidiser: O₂ or N₂O (enriched atmospheres)
• Ignition: Diathermy, laser, cautery
• Fuel: Surgical drapes, alcohol preps, ETT
• Prevention: Use aqueous skin prep (not alcohol) near diathermy; no pooling of alcohol; oxygen-enriched atmosphere avoidance around ignition sources

Other Electrical Hazards

• Static electricity: Detonation of flammable anaesthetic agents (historically with ether/cyclopropane — now abolished)
• Lasers: CO₂, Nd:YAG — risk of ETT fire; use laser-resistant ETT, lowest FiO₂ possible
• MRI: Ferromagnetic objects, pacemaker interference → specific MRI-compatible equipment required

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10. Post-operative Analgesia for Paediatric Lower Abdominal Surgery & Thoracotomy

Principles of Paediatric Analgesia

• Multimodal analgesia: Combining agents reduces total opioid requirements ("opioid-sparing")
• WHO analgesic ladder (paediatric modification): Non-opioid → weak opioid → strong opioid
• Doses are weight-based; children are NOT small adults
• Pain assessment tools: FLACC (0–2 years), Wong-Baker FACES (3–7 years), NRS (>7 years)

Lower Abdominal Surgery (Inguinal Hernia, Circumcision, Orchidopexy, Appendicectomy)

Regional Techniques

• Dexamethasone 0.1 mg/kg: Prolongs duration to ~12 hours
• Dexmedetomidine 1 µg/kg: Prolongs to 10–14 hours
• Clonidine 1–2 µg/kg: Prolongs to 6–10 hours
• Ketamine 0.5 mg/kg (preservative-free): Prolongs to ~8 hours

Systemic Analgesia (all paediatric surgery)

• Paracetamol: 15 mg/kg PO/IV q6h (max 60 mg/kg/day); safe in all ages
• NSAIDS: Ibuprofen 5–10 mg/kg q6h (>3 months); diclofenac 1 mg/kg; avoid in neonates, renal impairment, asthma
• Opioids (if needed): Morphine 0.1 mg/kg IV/IM (avoid in neonates <6 months — respiratory depression); consider PCA in >5 years

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Thoracotomy in Paediatrics

1. Thoracic Epidural Analgesia (TEA) — Gold Standard

• Most effective for thoracotomy pain
• Insert at T4–6 level (target dermatomal level T2–8)
• Drug: Bupivacaine 0.1–0.125% + fentanyl 1–2 µg/mL infusion
• Rate: 0.1–0.2 mL/kg/hr
• Provides excellent post-op analgesia 48–72 hours
• Facilitates early extubation, reduces lung complications
• Risks: PDPH, epidural haematoma/abscess, hypotension, motor block

2. Paravertebral Block (PVB)

• Excellent alternative if thoracic epidural contraindicated
• Single injection or catheter
• Unilateral analgesia (unlike bilateral epidural); less hypotension
• USG-guided: Identify paravertebral space (loss of resistance / USG visualisation of pleural displacement)
• Drug: 0.5 mL/kg bupivacaine 0.25–0.5% (max 2 mg/kg) per level; or catheter infusion
• Advantages over TEA: Less haemodynamic instability, no urinary retention, easier in coagulopathy

3. Intercostal Nerve Blocks

• Simple, effective; surgeon can inject under direct vision
• Bupivacaine 0.25% 0.5 mL/kg per level (max 2 mg/kg total)
• Short duration (4–6 hours); multiple levels required
• Significant systemic absorption from intercostal space → toxicity risk (highest absorption rate of any block site)

4. Serratus Anterior Plane Block (SAPB)

• USG-guided; between serratus anterior and latissimus dorsi
• Covers T2–T9 lateral chest wall
• Technically easier; no neuraxial risks
• Increasing use in paediatric thoracic surgery

5. PECS II Block

• USG-guided; covers medial/lateral pectoral nerves + intercostobrachial
• Less evidence in children; used in older paediatric patients

6. Systemic Adjuncts

• IV paracetamol 15 mg/kg q6h
• Ketorolac 0.5 mg/kg q6h (>1 year; short course only)
• IV morphine PCA (>5 years) or NCA (nurse-controlled) in younger
• Dexmedetomidine infusion 0.2–0.5 µg/kg/hr (opioid-sparing, anxiolysis)
• Gabapentin (limited paediatric evidence for post-thoracotomy)

ERAS for Paediatric Thoracotomy

• Preoperative education, premedication (midazolam 0.5 mg/kg PO)
• Regional anaesthesia first
• Multimodal analgesia
• Early oral feeding
• Early physiotherapy and ambulation

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Quick Reference Summary Table