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MODEL ANAESTHESIA CASE SHEET

LAVH (Laparoscopy Assisted Vaginal Hysterectomy) in a Patient with Hypothyroidism

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PART I - PATIENT PROFILE

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PART II - HISTORY

Chief Complaint

Present Illness

• Menorrhagia since 8 months, passing clots
• Mild lower abdominal heaviness, no acute pain
• Treated with Tab. Levothyroxine 75 mcg once daily for 3 years (hypothyroidism)
• No symptoms of myxedema: no excessive fatigue, no periorbital puffiness at present
• Last TFT done 5 months ago - TSH 3.2 mIU/L (within normal range)

Past History

Drug History

• Tab. Levothyroxine 75 mcg OD (morning, empty stomach) - CONTINUED on morning of surgery
• Tab. Iron (ferrous sulfate 200 mg) BD - for anaemia secondary to menorrhagia

Family History

• Mother: hypothyroidism (autoimmune)
• No family history of malignant hyperthermia, pseudocholinesterase deficiency

Personal History

• Non-smoker, non-alcoholic
• Diet: mixed
• No significant weight gain recently; mild cold intolerance

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PART III - PHYSICAL EXAMINATION

General Examination

Airway Assessment

Note: Macroglossia is a feature of severe/long-standing hypothyroidism. Examine the tongue carefully. Prepare for potentially modified airway.

Systemic Examination

• S1, S2 heard, no murmurs
• No signs of pericardial effusion
• No JVP elevation
• ECG: sinus bradycardia at 62/min, low voltage complexes in limb leads (characteristic of hypothyroidism), QTc 440 ms

• Air entry equal bilaterally
• No added sounds
• Mild obesity - anticipate reduced FRC in Trendelenburg position

• Uterus 14 weeks size, midline, mobile, non-tender
• No ascites

• No altered sensorium
• Delayed relaxation of ankle jerk (characteristic hypothyroid sign)

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PART IV - INVESTIGATIONS

Haematological

Note on coagulation: Hypothyroidism can cause acquired von Willebrand disease and factor VIII deficiency. Check coagulation profile carefully.

Biochemistry

Note: Hyponatremia (impaired free water clearance) and hyperlipidaemia are common in hypothyroidism. Na+ must be corrected if <130 mEq/L before elective surgery.

Thyroid Function Tests

Conclusion: Patient is currently EUTHYROID on levothyroxine. Elective surgery can proceed. TFT done within 6 months is acceptable per Miller's Anesthesia guidelines - no need to repeat if patient is on stable dose and was last assessed as euthyroid within 6 months.

Cardiovascular

Note on pericardial effusion: Mild pericardial effusion is a known feature of hypothyroidism. It is usually haemodynamically insignificant and resolves with adequate treatment. ECHO mandatory preoperatively.

Other Investigations

• Urine routine/microscopy: Normal
• Pap smear: No malignant cells
• Pelvic USG: Fibroid uterus, uterus 14 weeks size, multiple fibroids
• Cervical biopsy: Benign

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PART V - PREOPERATIVE PREPARATION & OPTIMIZATION

Optimization Checklist

Consent

• Explained: risks of GA, endotracheal intubation, invasive monitoring
• Procedure-specific: bleeding, conversion to laparotomy, DVT, bladder/ureter injury
• Anaesthesia-specific: PONV, awareness, failed intubation, hypothermia (especially relevant in hypothyroid patient)
• Signed informed consent obtained

Pre-anaesthetic Orders

• NBM from midnight (solids 8 hrs, clear fluids 2 hrs prior)
• Continue Levothyroxine on morning of surgery
• Tab. Ranitidine 150 mg night before and morning of surgery (aspiration prophylaxis - relevant for hypothyroid patients who have reduced GI motility)
• Tab. Metoclopramide 10 mg HS (prokinetic - reduces risk of aspiration given delayed gastric emptying in hypothyroidism)
• IV access: 18G cannula in right antecubital fossa
• Cross-match 2 units PRBC
• Warm IV fluids ready

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PART VI - ANAESTHETIC PLAN

Type of Anaesthesia

1. LAVH requires steep Trendelenburg + pneumoperitoneum - IPPV with ETT mandatory for airway protection and management of respiratory mechanics
2. Prolonged procedure with lithotomy and Trendelenburg - high aspiration risk without secured airway
3. Hypothyroid patient - delayed gastric emptying increases aspiration risk further

Monitoring Plan

• Pulse oximetry (SpO2)
• ECG (5-lead - watch for bradycardia, dysrhythmias from hypothyroidism + CO2 pneumoperitoneum)
• NIBP (every 3 minutes during induction, every 5 minutes intraoperatively)
• End-tidal CO2 (ETCO2) - essential during pneumoperitoneum to detect CO2 absorption and guide ventilation
• Temperature monitoring (nasopharyngeal or oesophageal) - MANDATORY; hypothyroid patients prone to hypothermia
• Urine output (Foley catheter, target >0.5 mL/kg/hr)

• Arterial line (radial) if haemodynamically borderline
• Neuromuscular monitoring (Train-of-Four) - neuromuscular blockade reversal critical; hypothyroid patients may have prolonged NMB

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PART VII - INTRAOPERATIVE MANAGEMENT

Pre-Induction

• IV access confirmed, warm Ringer's lactate infusion started
• Antacid premedication: Inj. Ranitidine 50 mg IV + Inj. Metoclopramide 10 mg IV
• Pre-oxygenation with 100% O2 for 3-5 minutes (denitrogenation)
• Forced warm air blanket applied
• Temperature baseline recorded
• Vasopressors available: Inj. Ephedrine 30 mg/10 mL and Inj. Phenylephrine 100 mcg/mL ready (hypothyroid patients prone to haemodynamic depression with induction)

Induction

Ketamine (alternative induction agent, 1-2 mg/kg) - preferred by some authorities because it stimulates the sympathetic nervous system and supports haemodynamics in hypothyroid patients with reduced cardiac output (Barash, Clinical Anesthesia 9e).

Airway Management

• Laryngoscopy: Direct laryngoscopy with Macintosh blade size 3
• Tube: Cuffed ETT 7.5 mm ID (oral RAE if available for gynae positioning)
• Video laryngoscope on standby (goitre, possible macroglossia)
• Cuff inflated; tube position confirmed with bilateral auscultation + ETCO2 waveform
• Secure tube with tape; ensure tube does not dislodge during steep Trendelenburg

Maintenance

Special Intraoperative Considerations

• CO2 insufflation at 12-14 mmHg (not >15 mmHg - reduces renal and splanchnic flow at higher pressures)
• Anticipate: ↑ ETCO2, ↑ airway pressures, ↑ SVR, ↑ MAP, ↓ cardiac output initially
• Increase minute ventilation (RR or TV) to compensate for CO2 absorption and maintain normocapnia

• Cardiovascular: ↑ SVR, ↑ MAP, ↑ myocardial O2 consumption
• Respiratory: ↓ FRC, ↓ compliance, ↑ peak airway pressures, V/Q mismatch
• CNS: ↑ ICP, ↑ intraocular pressure
• Risk of: tracheal tube displacement (upward migration to carina), brachial neuropraxia, facial/airway oedema

• Recheck ETT position after positioning
• Pad pressure points (shoulders, arms)
• Shoulder braces to prevent patient sliding
• Reduce TV slightly, increase PEEP 5 cmH2O to recruit alveoli
• Monitor for cardiovascular changes from abrupt return to supine (haemodynamic swings)

• Modified lithotomy position
• Watch for: leg compartment syndrome (avoid >2 hours in lithotomy), DVT risk
• Ensure SCDs (sequential compression devices) on both legs

• Active forced-air warming blanket throughout
• All IV fluids warmed to 37°C
• Keep OT temperature 22-24°C
• Monitor core temperature continuously (oesophageal/nasopharyngeal)
• Target: core temperature >36°C

• Sensitivity to sedatives, opioids, anaesthetic agents possibly increased
• Prolonged NMB recovery possible (hypothyroid myopathy)
• Reduced drug metabolism (lower hepatic blood flow, reduced enzyme activity)
• Use TOF monitoring strictly; consider sugammadex for reversal of rocuronium

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PART VIII - REVERSAL AND EXTUBATION

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PART IX - POSTOPERATIVE MANAGEMENT

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PART X - COMPLICATIONS SPECIFIC TO THIS CASE

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VIVA QUESTIONS

Section A - Hypothyroidism: Basics & Perioperative Relevance

• Cardiovascular: Bradycardia, reduced cardiac output, increased peripheral vascular resistance, pericardial effusion (low voltage ECG), impaired baroreceptor reflexes, prolonged QTc
• Respiratory: Reduced hypoxic and hypercapnic ventilatory drive (potentiated by opioids and GA), obstructive sleep apnoea (macroglossia, myxoedema of pharynx), reduced FRC
• Neurological: Altered sensorium, psychosis (myxoedema madness), increased sensitivity to sedatives and opioids, peripheral neuropathy, delayed deep tendon reflex relaxation
• Metabolic: Reduced BMR, hypothermia, hypercholesterolaemia, hyponatraemia (SIADH-like - impaired free water excretion)
• Haematological: Anaemia (normocytic normochromic), coagulopathy (reduced vWF and Factor VIII), prolonged bleeding time
• GI: Reduced motility, delayed gastric emptying, constipation, increased aspiration risk
• Musculoskeletal: Myopathy, rhabdomyolysis risk, prolonged neuromuscular blockade (Barash, Clinical Anesthesia 9e; Miller's Anesthesia 10e)

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• Euthyroid on replacement therapy (like our patient): Surgery can proceed safely
• Mild to moderate hypothyroidism (elevated TSH, normal free T4, asymptomatic): Per Miller's Anesthesia 10e, mild-moderate dysfunction has minimal perioperative impact; no compelling reason to postpone, but monitoring is important
• Moderate-severe symptomatic hypothyroidism (elevated TSH + low free T4): Elective surgery should be POSTPONED until euthyroid state achieved. Surgery, stress, or illness can precipitate myxedema coma in these patients
• Emergency surgery: Proceed with precautions; consult endocrinologist; consider IV T4 200-300 mcg as loading dose

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• Sinus bradycardia (most common)
• Low voltage complexes in limb leads and precordial leads (due to pericardial effusion and myxoedema)
• Prolonged PR interval, QRS widening
• Prolonged QTc interval (risk of Torsades de Pointes)
• Flattened or inverted T waves
• First-degree AV block

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• Tracheal intubation and controlled ventilation
• IV Levothyroxine 200-300 mcg over 5-10 minutes (then 50-100 mcg/day IV)
• IV Liothyronine (T3) 10-25 mcg initially, then 10 mcg 8-hourly
• IV hydrocortisone 100 mg 8-hourly (to prevent adrenal crisis - commonly co-existent adrenal insufficiency in Hashimoto's/Schmidt's syndrome)
• Passive external warming (avoid active warming - precipitates vasodilation and cardiovascular collapse)
• Correct hyponatraemia cautiously with normal saline
• Correct hypoglycaemia with IV dextrose
• Vasopressors for refractory hypotension (norepinephrine preferred)

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• Ketamine is considered the preferred induction agent in hypothyroid patients because it stimulates the sympathetic nervous system, offsetting the reduced cardiac output and peripheral vasodilation that can occur with other agents (Barash, Clinical Anesthesia 9e)
• Etomidate is also suitable as it is haemodynamically stable (but concerns about adrenal suppression if there is co-existent adrenal insufficiency)
• Propofol can be used but requires dose reduction and slower titration due to the reduced cardiac output and increased drug sensitivity
• Thiopentone is less preferred (vasodilatory, reduced cardiac reserve)
• Note: Per Barash 9e: "Most anesthetic medications may be used without difficulty in hypothyroid patients" when the patient is euthyroid; ketamine is proposed as ideal particularly for haemodynamically compromised hypothyroid patients

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• Barash's Clinical Anesthesia (9e) notes there is "little, if any, decrease in the MAC for volatile agents" in hypothyroid patients
• However, reduced cardiac output alters drug uptake kinetics - the rate of rise of alveolar concentration of volatile agents is FASTER with reduced CO (similar to a right-to-left shunt effect), potentially speeding induction
• Clinically, titration to clinical endpoints and depth-of-anaesthesia monitoring (BIS if available) is more reliable than relying on MAC values

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Section B - Anaesthesia for LAVH

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• Steep Trendelenburg + pneumoperitoneum increases aspiration risk - ETT with cuffed tube is the only reliable airway protection
• Raised intra-abdominal pressure reduces respiratory compliance - IPPV with controlled ventilation is needed to manage hypercapnia
• Prolonged and variable procedure with patient position changes - secured airway essential
• LMA: inadequate seal at increased airway pressures; risk of regurgitation in lithotomy
• Spinal: Insufficient for the laparoscopic phase (high level needed, diaphragmatic irritation from CO2, patient discomfort from Trendelenburg, cannot control ventilation for CO2 management)

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• At insufflation, ETCO2 rises within 20-30 minutes due to systemic CO2 absorption
• Increase respiratory rate (by 15-25%) or tidal volume to maintain ETCO2 at 35-40 mmHg (normocapnia)
• Use pressure-controlled ventilation if peak airway pressures are high with volume control
• Apply PEEP 5 cmH2O to prevent alveolar collapse (particularly important in steep Trendelenburg)
• Keep insufflation pressure <15 mmHg (higher pressures associated with renal impairment and cardiovascular compromise)
• In hypothyroid patient: blunted hypercapnic respiratory response - rely entirely on monitoring ETCO2 (patient cannot compensate independently)

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• Confirm correct ETT placement (capnography waveform)
• Guide ventilator adjustments to maintain normocapnia during CO2 absorption from pneumoperitoneum
• Detect CO2 embolism (sudden fall in ETCO2, haemodynamic collapse, mill-wheel murmur)
• Detect endobronchial intubation after Trendelenburg positioning (ETCO2 rise with unilateral breath sounds)
• Detect equipment circuit leaks or disconnection (sudden fall in ETCO2)
• In hypothyroid patient specifically: blunted ventilatory response to CO2 makes clinical assessment unreliable - ETCO2 monitoring is essential

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• Steep Trendelenburg: ETT migration to right main bronchus (check after positioning), facial/pharyngeal oedema (avoid prone to post-op stridor), ↑ ICP (caution in patients with raised ICP), brachial plexus stretch (padded shoulder braces, avoid extreme positions)
• Lithotomy position (vaginal phase):
  • Compartment syndrome of leg (avoid >2 hours; release every 30-60 minutes if prolonged)
  • Common peroneal nerve palsy (protect with padding at fibular head)
  • Obturator, femoral, and saphenous nerve injuries (avoid hyperabduction/external rotation)
  • DVT (use SCDs; LMWH post-op)
  • Hypotension on returning legs to neutral (venous pooling - pre-empt with fluid bolus)

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1. Temperature: Hypothyroid patient has reduced BMR + pneumoperitoneum impairs normal thermoregulation - double risk of perioperative hypothermia; aggressive active warming mandatory
2. Aspiration: Delayed gastric emptying (hypothyroid GI dysmotility) + lithotomy + Trendelenburg = triple aspiration risk; RSI or modified RSI, full anti-aspiration prophylaxis
3. Haemodynamic monitoring: Reduced cardiac reserve (hypothyroid ↓CO) + pneumoperitoneum-induced ↑SVR = potential for acute hypertension or hypotension; arterial line if borderline
4. Drug dosing: Reduced drug metabolism in hypothyroidism (reduced hepatic blood flow); titrate all agents
5. NMB reversal: Hypothyroid myopathy may prolong NMB; TOF monitoring mandatory; do not extubate until TOF >0.9
6. Postoperative ventilation: Hypothyroid patients are at risk of prolonged ventilatory depression from opioids/anaesthetic agents + Trendelenburg-induced FRC reduction; monitor SpO2 extended post-op
7. Levothyroxine continuity: Resume PO levothyroxine next morning; IV T4 if prolonged NPO >5 days

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Section C - Higher-Order Viva Questions

• Elevated Anti-TPO (anti-thyroperoxidase) antibodies indicate Hashimoto's thyroiditis (autoimmune hypothyroidism) - the most common cause of hypothyroidism in iodine-sufficient regions
• Clinically relevant because:
  • Hashimoto's is associated with other autoimmune conditions - Screen for Type 1 DM (check fasting glucose), Addison's disease (Schmidt's syndrome = Hashimoto's + Addison's), pernicious anaemia, vitiligo
  • Adrenal insufficiency co-existing with Hashimoto's (Schmidt's syndrome) is important perioperatively - patient may need perioperative steroid cover
  • Risk of perioperative adrenal crisis if undetected adrenal insufficiency
  • Maternal anti-TPO in women of childbearing age is relevant for future pregnancy (not immediately relevant here)

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• Levothyroxine has a half-life of 6-7 days due to protein binding; missing a single dose does NOT significantly affect thyroid status acutely
• However, standard practice is to continue levothyroxine on the morning of surgery with a small sip of water (per current guidelines - Miller's Anesthesia 10e notes "preoperative additional thyroid function is not needed if patient is on stable medication dose and was assessed euthyroid within previous 6 months")
• If patient is NPO post-operatively for a prolonged period (>5 days), IV levothyroxine at 70-80% of the oral dose can be given (oral absorption is 80%, hence dose adjustment)
• Abrupt prolonged cessation risks a slow drift back toward hypothyroid state - important in perioperative metabolic stress

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• Hypothyroidism leads to:
  • ↓ Hepatic blood flow and reduced hepatic drug metabolism
  • ↓ Renal clearance
  • ↓ Plasma protein levels (reduced drug binding = increased free drug fraction)
  • Reduced phase I hepatic enzymatic activity
• Result: Increased and prolonged effect of opioids
• Clinical implications:
  • Dose reduction of all opioids (start at 50-75% of usual dose, titrate to effect)
  • Extended PACU monitoring for respiratory depression
  • Multimodal analgesia (NSAIDs, paracetamol, regional blocks) to minimize opioid requirements
  • Avoid neuraxial morphine in this patient if possible (prolonged respiratory depression risk)

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• Volume of distribution: Increased total body water (myxoedema) increases VD for hydrophilic drugs; decreased lean body mass reduces VD for lipophilic drugs
• Protein binding: Hypoalbuminaemia increases free fraction of highly protein-bound drugs (propofol, fentanyl, vecuronium)
• Metabolism: Reduced hepatic CYP enzyme activity, reduced hepatic blood flow - prolongs t1/2 of most anaesthetic agents
• Renal clearance: Mildly reduced GFR
• Net effect: Unpredictable drug sensitivity - always titrate to effect; use the lowest effective dose with careful monitoring

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• Hyperkalaemia risk: Hypothyroid myopathy may cause mild muscle membrane abnormalities; succinylcholine-induced K+ release of 0.5-1.0 mEq/L is normally well-tolerated but if pre-existing hyperkalaemia (rare in hypothyroidism - usually normoK+ or even hypoK+), this could be relevant
• Prolonged block: Pseudocholinesterase activity may be mildly reduced in hypothyroidism - potential for slightly prolonged phase I block
• Rhabdomyolysis trigger: Very rare with succinylcholine alone, but hypothyroid myopathy theoretically increases susceptibility
• Preferred alternative: Rocuronium 1.2 mg/kg + sugammadex reversal is a safer and equally rapid RSI alternative in this patient; avoids depolarising block complications entirely

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• Use multimodal PONV prophylaxis: Ondansetron 4 mg + Dexamethasone 8 mg + Metoclopramide 10 mg
• Consider Total Intravenous Anaesthesia (TIVA) with propofol infusion instead of volatile agents (propofol reduces PONV)
• Minimize opioid use (TAP block, NSAIDs)
• Adequate hydration intraoperatively
• Note: Dexamethasone is appropriate here - no contraindication in euthyroid hypothyroidism; it will not precipitate adrenal crisis in a patient not known to have adrenal insufficiency

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1. Stop precipitating cause (if during peritoneal insufflation - vasovagal response; lower CO2 pressure, deflate)
2. Inj. Atropine 0.6 mg IV (repeat if no response up to 3 mg total)
3. Inj. Glycopyrrolate 0.2-0.4 mg IV (alternative/adjunct - less CNS effects)
4. If atropine-resistant: Inj. Ephedrine 6 mg IV boluses (sympathomimetic)
5. External transcutaneous pacing if haemodynamically unstable
6. Consider: underlying myxoedema as cause if refractory - treat with IV T4 if suspected
7. Rule out: hypoxia, hypercarbia, CO2 embolism, volatile overdose as causes

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1. Pre-oxygenation 3-5 minutes (maximise O2 reserves)
2. First attempt with video laryngoscope (McGrath or C-MAC) as primary tool
3. If first attempt fails: facemask ventilation with oropharyngeal airway, call for help
4. Second attempt: change blade, manipulate (BURP/ELM), use bougie
5. If still unsuccessful: insert supraglottic airway (i-gel or LMA ProSeal)
6. If cannot intubate, cannot oxygenate: CICO (Can't Intubate, Can't Oxygenate) - front-of-neck airway (surgical or needle cricothyrotomy)
7. Awake fibreoptic intubation should be planned from the outset if airway assessment suggests high risk (Mallampati 3-4, reduced mouth opening, large goitre with tracheal deviation)

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What's Covered and Key Teaching Points

The Case Design

• 45F with Hashimoto's thyroiditis (autoimmune hypothyroidism), currently euthyroid on levothyroxine 75 mcg - this is the most common and realistic scenario
• Fibroid uterus with menorrhagia (logical indication for LAVH)
• Mild anaemia (Hb 10.2), trace oedema, borderline dyslipidaemia, goitre Grade I - all authentic hypothyroid features
• Trivial pericardial effusion on echo - a classic, often-missed finding in hypothyroid patients

Core Anaesthetic Principles Applied

The 20 Viva Questions span:

• Basic sciences (thyroid physiology, pharmacokinetics)
• Clinical management (when to postpone surgery, myxoedema coma)
• Procedure-specific (pneumoperitoneum physiology, Trendelenburg, LAVH positioning)
• Higher-order integration (combined risk hypothyroid + LAVH, Schmidt's syndrome, PONV, difficult airway)