Anaesthetic Management of Dilated Cardiomyopathy (DCM) for Caesarean Section

Note on terminology: "Tilted cardiomyopathy" is interpreted as dilated cardiomyopathy (DCM). This encompasses both pre-existing DCM and peripartum cardiomyopathy (PPCM), which are managed on the same haemodynamic principles.

Pathophysiology Relevant to Anaesthesia

• Reduced LVEF (often <45%), dilated ventricles, poor contractility
• Elevated LVEDP → pulmonary congestion
• Compensatory high SVR and tachycardia to maintain output
• Risk of arrhythmias, thromboembolism, and sudden death

Pre-operative Assessment

Haemodynamic Goals

Choice of Anaesthetic Technique

1. Regional Anaesthesia — Preferred for Most Patients

• Gradual sympathectomy → controlled reduction in SVR and preload
• Avoids haemodynamic stress of airway instrumentation
• Allows titration and haemodynamic manipulation
• Epidural opioids reduce systemic catecholamine release

• Acceptable with low-dose intrathecal component + epidural top-up
• Reduces the abrupt hypotension of single-shot spinal
• Sasaki et al. (2023, PMID 36930091): CSE was the most commonly used technique for DCM patients without heart failure (8/10 patients)

• Relatively contraindicated in severe DCM (LVEF <30%) — abrupt ↓ SVR may precipitate acute decompensation
• May be used in mild–moderate DCM with careful vasopressor support

2. General Anaesthesia — Reserved for Specific Indications

• Regional anaesthesia is contraindicated (coagulopathy, anticoagulation, haemodynamic instability, patient refusal)
• Emergency with no time for regional technique
• Severe decompensated heart failure requiring immediate delivery

• Induction: Etomidate preferred (cardiovascular stability) over propofol (myocardial depression) or thiopentone
• Ketamine: Use with caution — catecholamine release may be harmful in a depleted myocardium
• Opioids: Fentanyl/remifentanil for blunting laryngoscopy response
• Maintenance: Volatile agents cause dose-dependent myocardial depression — use at minimum effective concentration; TIVA with propofol/remifentanil may be considered
• Avoid: High-dose volatile agents, excessive positive pressure ventilation (reduces venous return)
• Sasaki et al. found general anaesthesia rate was 25% in DCM patients who subsequently developed heart failure vs 4% in those who did not, suggesting GA may reflect more severe cases

Monitoring

Intraoperative Management

Positioning

• Left lateral tilt (15°) to prevent aortocaval compression
• Aortocaval compression further reduces venous return in an already compromised heart

Fluids

• Avoid large IV bolus preload — pulmonary oedema risk
• Crystalloid used judiciously; consider colloid
• Goal-directed fluid therapy guided by CO monitoring or echo
• Vasopressors preferred over fluid loading to treat hypotension

Vasopressors

• Phenylephrine: Increases SVR; use cautiously — may increase afterload and worsen CO in severe DCM
• Norepinephrine: Preferred vasopressor — balanced α/β effect, better CO preservation than phenylephrine
• Ephedrine: Reasonable choice — has β-inotropic effect; avoids pure vasoconstriction
• Avoid high-dose pure α-agonists which dramatically increase SVR

Inotropes (if low CO/decompensation)

• Dobutamine: First-line inotrope (β1 agonist, reduces SVR)
• Milrinone: PDE inhibitor — positive inotropy + vasodilation; useful in severe DCM
• Dopamine / Adrenaline: Reserve for refractory cases

Uterotonic Agents

Postoperative Care

• HDU/ICU monitoring for 24–48 hours minimum — highest risk period is immediately postpartum
• Autotransfusion of 500–700 mL uterine blood at delivery suddenly increases preload → risk of acute decompensation/pulmonary oedema
• Resume heart failure medications early (beta-blocker, loop diuretic, ACE inhibitor — but only after breastfeeding decision confirmed, as ACEi are safe in breastfeeding)
• Continue thromboprophylaxis (high VTE + LV thrombus risk)
• Multimodal analgesia: NSAIDs with caution (fluid retention, afterload increase) — prefer paracetamol + neuraxial opioids
• Watch for postpartum haemorrhage — treat aggressively but avoid excessive fluid

High-Risk Flags Requiring Additional Planning

Summary: Anaesthetic Plan for DCM at Caesarean Section

PREOP: Echo, NT-proBNP, optimise HF meds, stop ACEi, 
        check anticoagulation, consent for invasive monitoring

TECHNIQUE: Slow incremental epidural (preferred) 
           or low-dose CSE
           GA only if contraindicated/emergency

MONITORS: Art line ± CVC; intraoperative echo if available

HAEMODYNAMIC GOALS: ↓ SVR (mild), ↑ or maintain HR (>80), 
                    normovolaemia, support contractility

VASOPRESSOR: Norepinephrine infusion titrated

OXYTOCIN: Low-dose infusion only; NO ergometrine

POSTOP: ICU/HDU 24-48h; resume HF medications early

References

• Morgan & Mikhail's Clinical Anesthesiology, 7e — Heart Disease in Pregnancy
• Barash, Cullen, & Stoelting's Clinical Anesthesia, 9e — Cardiomyopathy in Pregnancy
• Meng ML, Schroder J, Lindley K. Obstetric anesthesia management of dilated cardiomyopathies and heart failure: a narrative review. Int J Obstet Anesth. 2024. PMID 39226639
• Nayak A, Ninave S, Tayade S. Anesthetic management in peripartum cardiomyopathy: a contemporary review. Cureus. 2022. PMID 36726888
• Sasaki M, Ohnishi Y. Anesthesia during delivery in pregnant women with dilated cardiomyopathy. Medicine. 2023. PMID 36930091

Anaesthetic Management of Dilated Cardiomyopathy (DCM) for Caesarean Section

Introduction (0.5 mark)

Pre-operative Assessment (1 mark)

• Echocardiography: LVEF, LV/RV dimensions, valvular lesions, intracardiac thrombus
• NT-proBNP: marker of decompensation; guides optimisation
• ECG: LBBB, arrhythmias, QRS duration
• CXR: cardiomegaly, pulmonary oedema
• Coagulation profile: if anticoagulated for LV thrombus
• Functional class (NYHA): exercise tolerance, orthopnoea
• Medications: ACE inhibitors/ARBs stopped pre-delivery; beta-blockers, diuretics continued
• Multidisciplinary Pregnancy Heart Team involvement (obstetrician, cardiologist, MFM, intensivist)

Haemodynamic Goals (1 mark)

Choice of Anaesthetic Technique (2 marks)

Regional Anaesthesia — Technique of Choice

• Gradual, controlled sympathectomy
• Avoids haemodynamic stress of airway instrumentation
• Allows real-time titration

• Acceptable with a low-dose intrathecal component + epidural top-up
• Reduces the abrupt hypotension of single-shot spinal

• Relatively contraindicated in severe DCM (LVEF <30%) — abrupt ↓ SVR may precipitate acute decompensation

General Anaesthesia — Reserved For:

• Coagulopathy / therapeutic anticoagulation (LV thrombus)
• Haemodynamic instability / acute decompensation
• Emergency with no time for regional technique
• Patient refusal of regional

• Induction: Etomidate preferred (cardiovascular stability); avoid large-dose propofol (myocardial depression)
• Opioids: Fentanyl/remifentanil to blunt laryngoscopy response
• Maintenance: Minimum effective concentration of volatile agent; TIVA (propofol/remifentanil) is an alternative
• Avoid: High-dose volatile agents, ketamine (catecholamine surge in depleted myocardium)

Monitoring (1 mark)

Intraoperative Management (2 marks)

• Avoid large IV preload boluses (pulmonary oedema risk)
• Goal-directed therapy; vasopressors preferred over fluids for hypotension

• Norepinephrine infusion — preferred (balanced α/β, preserves CO better than pure α-agonists)
• Ephedrine — reasonable (β-inotropic effect)
• Avoid high-dose phenylephrine — raises SVR, may worsen CO

• Dobutamine — first-line (β1-agonist, reduces SVR)
• Milrinone — positive inotropy + vasodilation; useful in severe DCM

Postoperative Care (1.5 marks)

• HDU/ICU monitoring for 24–48 hours — highest risk period is immediately postpartum (autotransfusion of 500–700 mL uterine blood → acute preload surge → pulmonary oedema)
• Resume heart failure medications early (beta-blocker, loop diuretic, ACE inhibitor)
• Continue thromboprophylaxis (high risk of VTE and LV thrombus)
• Analgesia: paracetamol + neuraxial opioids; NSAIDs with caution (fluid retention, ↑ afterload)
• Watch for and aggressively treat postpartum haemorrhage
• Serial echocardiography and NT-proBNP post-delivery

Special Considerations for Severe DCM (LVEF <30%) (1 mark)

• Mechanical circulatory support on standby: IABP, Impella, or ECMO
• If RV dysfunction: avoid ↑ PVR; consider inhaled NO or prostacyclin
• Anticoagulated patients: hold IV heparin ≥4 h, LMWH ≥24 h before neuraxial
• Delivery at a Level IV maternal care centre

Summary Table (allocated within above marks)

Labour Analgesia — Principles, Techniques, Pain Pathways, and Stages of Labour

I. Introduction

II. Pain in Labour — Pathways and Stages

A. The Two Components of Labour Pain

B. Pain Pathway in Detail

1. Uterine contractions → ischaemia + myometrial distension → release of bradykinin, substance P, lactic acid, prostaglandins
2. Activation of uterine and cervical afferents (C-fibres, A-delta fibres)
3. Travel with sympathetic nerves → uterine plexus → hypogastric plexus → lumbar sympathetic chain
4. Enter spinal cord at T10, T11, T12, L1
5. Pain referred to lower abdomen, lumbosacral region, iliac crests, thighs

• Additional pressure on lumbosacral plexus, pelvic floor, rectum
• Begins to involve somatic fibres

1. Fetal head descends → distension of vagina, vulva, perineum
2. Activation of somatic afferents via pudendal nerve (S2–S4)
3. Additional contributions from ilioinguinal and genitofemoral nerves
4. Pain becomes sharp, burning, perineal

Examination Key Point: Adequate neuraxial analgesia for the first stage requires blockade of T10–L1; for the second stage it must extend to include S2–S4. — Miller's Anesthesia, 10e

C. Adverse Effects of Unrelieved Labour Pain

III. Physiological Changes of Pregnancy Relevant to Analgesia

IV. Principles of Labour Analgesia

1. Maternal safety: primum non nocere — avoid respiratory depression, haemodynamic instability
2. Fetal safety: minimise placental drug transfer and neonatal depression
3. Efficacy: adequate pain relief at the relevant spinal level for each stage
4. Minimal motor block: preserve ability to push in second stage (ambulatory epidural ideal)
5. Flexibility: technique must be adaptable for operative delivery (LSCS) if needed
6. Maternal autonomy: informed consent; maternal request is sufficient indication (ASA/SOAP guideline)
7. Timing: no cervical dilation threshold required; there is no point in first stage labour "too early" for neuraxial analgesia

V. Non-Pharmacological Techniques

VI. Pharmacological Techniques

A. Systemic Opioids

Remifentanil PCA is superior to longer-acting opioids but inferior to epidural analgesia. One-to-one nursing monitoring mandatory. — Miller's Anesthesia, 10e

B. Nitrous Oxide (Entonox — 50% N₂O/50% O₂)

• Inhaled; self-administered via demand valve
• Provides mild–moderate analgesia; does not eliminate pain
• Advantages: rapid onset/offset, no fetal accumulation, non-invasive
• Disadvantages: nausea, dizziness, environmental pollution
• Not a substitute for neuraxial analgesia in moderate–severe pain

C. Paracervical Block

• Local anaesthetic injected at lateral fornices of cervix (3 and 9 o'clock positions)
• Blocks uterine and cervical afferents → T10–L1 level
• Covers first stage pain only
• Risk: fetal bradycardia (direct fetal LA absorption or uterine artery vasospasm)
• Largely abandoned in favour of neuraxial techniques

D. Pudendal Nerve Block

• Perineal somatic analgesia for second stage and instrumental delivery
• LA injected transvaginally or transperineally near the ischial spine
• Blocks pudendal nerve (S2–S4) bilaterally
• Does not cover uterine/cervical pain (first stage)
• Simple, safe, but limited scope

VII. Neuraxial Analgesia — The Gold Standard

"Neuraxial analgesia is the most reliable and effective method of reducing pain during labour." — Miller's Anesthesia, 10e (Level I evidence, meta-analysis)

A. Epidural Analgesia

• Position: sitting (preferred) or lateral decubitus
• Loss-of-resistance technique (to air or saline) to identify epidural space
• Epidural catheter threaded 3–5 cm into space
• Test dose: 3 mL of 1.5% lidocaine + 1:200,000 epinephrine
  • Intravascular placement: HR ↑ >20 bpm (epinephrine marker)
  • Intrathecal placement: dense motor block within 3–5 min
• Loading dose: e.g., 10–15 mL bupivacaine 0.1% + fentanyl 2 mcg/mL
• Maintenance: PCEA (patient-controlled epidural analgesia) ± background infusion

• Local anaesthetics: Bupivacaine 0.0625–0.1% or ropivacaine 0.0625–0.17% (dilute = less motor block)
• Opioid adjuvants: Fentanyl 1–3 mcg/mL or sufentanil 0.1–0.5 mcg/mL → reduces LA requirement, enhances analgesia
• Epinephrine 1:400,000–1:800,000 → prolongs LA action, provides α2-mediated analgesia
• Clonidine: Effective adjuvant; FDA caution for obstetric use in USA

• Titratable, flexible — can be topped up for LSCS
• Covers both stages when extended to S2–S4
• Reduces circulating catecholamines → improves uteroplacental flow
• Does not increase caesarean section rate (Level I evidence)

B. Combined Spinal-Epidural (CSE) Analgesia

1. Epidural needle placed in epidural space
2. 27G spinal needle passed through → CSF confirmed
3. Intrathecal dose: e.g., fentanyl 10–25 mcg ± bupivacaine 1–2.5 mg
4. Spinal needle withdrawn; epidural catheter sited for subsequent dosing

• Rapid onset (5–10 min) vs epidural (15–20 min)
• Dense analgesia; minimal motor block with opioid-only intrathecal dose
• "Walking epidural" — preserves ambulation
• Epidural catheter available for maintenance and LSCS conversion

• Cannot test catheter immediately after spinal injection
• Slightly higher incidence of pruritus (intrathecal opioid)
• Transient fetal bradycardia reported (from rapid maternal pain relief → oxytocin surge → uterine hypertonia) — usually self-limiting

C. Continuous Spinal Analgesia

• Intrathecal catheter placed (usually following inadvertent dural puncture)
• Allows titrated dosing directly into CSF
• Used in high-risk patients (cardiac disease, severe scoliosis)
• Risk: PDPH if large-gauge catheter; meningitis; neurotoxicity from catheter tip positioning

D. Dural Puncture Epidural (DPE)

• Epidural needle placed; dural puncture made with spinal needle but no intrathecal drug injected
• Epidural catheter placed as normal
• The dural puncture allows enhanced drug flux into intrathecal space
• Better sacral spread compared to standard epidural
• Reduced incidence of unilateral/patchy block
• Increasingly used for labour analgesia

E. Patient-Controlled Epidural Analgesia (PCEA)

• Parturient self-administers boluses within programmed limits
• Advantages: lower total drug consumption, greater maternal satisfaction, fewer anaesthesia interventions
• Modes: PCEA alone, basal infusion + PCEA, or programmed intermittent epidural bolus (PIEB) + PCEA
• PIEB (periodic boluses from infusion pump) superior to continuous infusion — better spread, less motor block

VIII. Complications of Neuraxial Labour Analgesia

IX. Special Situations

X. Effect of Labour Analgesia on Labour Outcome

XI. Summary — Pain Levels and Technique Coverage

STAGE           PAIN ORIGIN          SPINAL LEVEL    TECHNIQUE COVERS
─────────────────────────────────────────────────────────────────────
First stage     Uterine/cervical      T10–L1          Epidural, CSE, paracervical block
                visceral                               Systemic opioids (partial)

Transition      Pelvic floor/         T10–S4          Epidural + sacral extension
                rectal pressure

Second stage    Vaginal/perineal      S2–S4           Epidural (sacral extension),
                somatic               (+T10–L1)       CSE, pudendal nerve block

Delivery/       Perineum              S2–S4           Epidural top-up, pudendal,
instrumental                                          spinal (if no existing epidural)

References

• Miller's Anesthesia, 10e — Chapter 58: Obstetric Anaesthesia
• Barash, Cullen & Stoelting's Clinical Anesthesia, 9e — Chapter 41: Obstetric Anaesthesia
• Morgan & Mikhail's Clinical Anesthesiology, 7e — Labour and Delivery Analgesia
• ASA Practice Guidelines for Obstetric Anesthesia (2016, reaffirmed 2023)

Labour Analgesia — Exam-Optimised Answer with Diagrams & Mnemonics

🧠 MASTER MNEMONIC — "LABOUR PAIN"

Use this to recall the entire topic structure in the exam hall:

L — Levels of pain (T10–L1 first stage; S2–S4 second stage)
A — Adverse effects of unrelieved pain
B — Blocks — neuraxial, regional, pudendal
O — Opioids — systemic (pethidine, fentanyl, remifentanil)
U — Uterine pathways — visceral C-fibres, hypogastric plexus
R — Regional (epidural, CSE, DPE, continuous spinal)
P — Principles — safety, efficacy, flexibility, minimal motor block
A — Assessment pre-procedure + complications
I — Indications, contraindications
N — Non-pharmacological techniques

I. Pain Pathway Diagram

Stage-by-Stage Pain Origins

╔══════════════════════════════════════════════════════════════════╗
║              LABOUR PAIN — TWO-COMPONENT MODEL                  ║
╠══════════════════════════════════════════════════════════════════╣
║                                                                  ║
║  FIRST STAGE (Latent + Active)          SECOND STAGE            ║
║  ───────────────────────────            ─────────────           ║
║  Source: Uterine contractions +         Source: Vaginal,        ║
║          cervical dilation              perineal, pelvic        ║
║                                         floor distension        ║
║  Type:   VISCERAL                       Type: SOMATIC           ║
║          Diffuse, cramping,                    Sharp, burning,  ║
║          poorly localised                      well-localised   ║
║                                                                  ║
║  Fibres: C-fibres (sympathetic)         Fibres: A-delta / Aβ    ║
║          A-delta                                (pudendal)      ║
║                                                                  ║
║  Spinal: T10 → T11 → T12 → L1          Spinal: S2 → S3 → S4   ║
║                                                                  ║
╚══════════════════════════════════════════════════════════════════╝

Afferent Pathway — Neuroanatomical Flow

UTERUS / CERVIX
      │
      │  (visceral C-fibres travel with sympathetics)
      ▼
UTEROVAGINAL PLEXUS (Frankenhauser's plexus)
      │
      ▼
HYPOGASTRIC PLEXUS
      │
      ▼
LUMBAR SYMPATHETIC CHAIN
      │
      ▼
SPINAL CORD: T10, T11, T12, L1
      │
      ▼
DORSAL HORN → SPINOTHALAMIC TRACT → THALAMUS → CORTEX
      
━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━

VAGINA / PERINEUM / PELVIC FLOOR
      │
      │  (somatic fibres via pudendal nerve)
      ▼
PUDENDAL NERVE (S2, S3, S4)
      │
      ▼
SACRAL CORD: S2–S4
      │
      ▼
DORSAL HORN → SPINOTHALAMIC TRACT → THALAMUS → CORTEX

II. Pain Levels at Each Stage — Quick Reference Box

┌─────────────────────────────────────────────────────────────────┐
│           SPINAL LEVELS BY STAGE OF LABOUR                     │
├──────────────────┬────────────────────┬────────────────────────┤
│ STAGE            │ PAIN SOURCE        │ SPINAL LEVEL           │
├──────────────────┼────────────────────┼────────────────────────┤
│ 1st stage        │ Uterine / cervical │ T10 → T11 → T12 → L1  │
│ (latent+active)  │ Visceral           │                        │
├──────────────────┼────────────────────┼────────────────────────┤
│ Transition       │ Pelvic floor       │ T10 → L1 + early S2–4  │
│ (8–10 cm)        │ Rectal pressure    │                        │
├──────────────────┼────────────────────┼────────────────────────┤
│ 2nd stage        │ Vaginal/perineal   │ T10–L1 + S2–S3–S4      │
│ (pushing)        │ Somatic            │                        │
├──────────────────┼────────────────────┼────────────────────────┤
│ Delivery +       │ Perineum           │ S2–S4                  │
│ instrumental     │ Pudendal territory │                        │
└──────────────────┴────────────────────┴────────────────────────┘

MNEMONIC: "Ten-to-One, then Two-to-Four"
  T10 → L1  =  First stage
  S2  → S4  =  Second stage (add these on top)

III. Mnemonic — Adverse Effects of Unrelieved Pain

"CRASH MOM"

C — Catecholamine surge → ↑ HR, ↑ BP, ↑ CO
R — Respiratory alkalosis (hyperventilation) → ↓ fetal O₂
A — Anxiety + psychological trauma
S — Sympathetic activation → uterine artery vasoconstriction
H — Hypermetabolism → ↑ O₂ consumption

M — Maternal exhaustion
O — Oxytocin imbalance (catecholamines inhibit uterine contractility)
M — Maternal satisfaction ↓ (negative birth experience)

IV. Techniques — Decision Flowchart

                  PATIENT IN LABOUR — ANALGESIA REQUESTED
                              │
                ┌─────────────▼──────────────┐
                │  CONTRAINDICATION to        │
                │  NEURAXIAL ANALGESIA?        │
                └──────┬──────────────┬───────┘
                       │ YES          │ NO
                       ▼             ▼
           ┌───────────────────┐  ┌──────────────────────────────┐
           │ NON-NEURAXIAL:    │  │   NEURAXIAL (PREFERRED)       │
           │ • Remifentanil PCA│  │                              │
           │ • N₂O (Entonox)   │  │  Elective/early labour?      │
           │ • IV Pethidine    │  │         │                    │
           │ • Pudendal block  │  │    ┌────┴────┐               │
           │ • TENS, massage   │  │    ▼         ▼               │
           └───────────────────┘  │  CSE      EPIDURAL           │
                                  │  (fast    (gradual,          │
                                  │  onset)   titratable)        │
                                  │    │         │               │
                                  │    └────┬────┘               │
                                  │         ▼                    │
                                  │   Maintain via PCEA / PIEB   │
                                  │         │                    │
                                  │    ┌────▼────────────┐       │
                                  │    │ Delivery       │       │
                                  │    │ imminent?      │       │
                                  │    └────┬───────────┘       │
                                  │         │YES                │
                                  │         ▼                   │
                                  │  Extend block to S2–S4      │
                                  │  (epidural top-up)          │
                                  └─────────────────────────────┘

V. Contraindications to Neuraxial Analgesia

Mnemonic: "Can't PLACE it"

C — Coagulopathy / anticoagulation (platelet <80,000)
A — Active infection at site (or untreated sepsis)
N — No consent / patient refusal

P — ↑ ICP (raised intracranial pressure)
L — Lesion at puncture site (tumour, abscess)
A — Allergy to local anaesthetic (rare)
C — Cardiovascular instability (relative — must be corrected first)
E — Exact anatomy unclear (severe scoliosis, prior spinal surgery — relative)

VI. Epidural Technique — Step-by-Step Box

┌──────────────────────────────────────────────────────────┐
│              EPIDURAL PLACEMENT — STEPS                  │
├──────────────────────────────────────────────────────────┤
│ 1. Consent + IV access + monitoring (SpO₂, BP, ECG)     │
│ 2. Position: SITTING (preferred) or LEFT LATERAL         │
│ 3. Level: L2–3 or L3–4 interspace                       │
│ 4. Sterile prep + LA skin infiltration                   │
│ 5. Tuohy needle → Loss of Resistance (LOR)               │
│    to saline or air                                      │
│ 6. Catheter threaded 3–5 cm into epidural space          │
│ 7. Aspirate: blood? → intravascular → resite             │
│              CSF?  → intrathecal → resite                │
│ 8. TEST DOSE: 3 mL lidocaine 1.5% + adrenaline           │
│    Intravascular: HR ↑ >20 bpm within 1 min              │
│    Intrathecal: dense motor block within 3–5 min         │
│ 9. Loading dose: 10–15 mL bupivacaine 0.1%              │
│                  + fentanyl 2 mcg/mL                    │
│ 10. Maintain: PCEA ± basal infusion / PIEB               │
└──────────────────────────────────────────────────────────┘

VII. Epidural Drug Choices — "BFEC" Mnemonic

B — Bupivacaine 0.0625–0.1% (dilute = less motor block)
    Ropivacaine 0.0625–0.17% (less cardiotoxic alternative)

F — Fentanyl 1–3 mcg/mL  OR  Sufentanil 0.1–0.5 mcg/mL
    (reduces LA requirement, reduces motor block)

E — Epinephrine 1:400,000–1:800,000
    (prolongs block, α2-mediated analgesia)

C — Clonidine (α2 agonist — adjuvant; FDA caution in USA for obstetrics)

VIII. CSE vs Epidural — Comparison Diagram

┌─────────────────────┬─────────────────┬──────────────────────┐
│ FEATURE             │ EPIDURAL        │ CSE                  │
├─────────────────────┼─────────────────┼──────────────────────┤
│ Onset               │ 15–20 min       │ 5–10 min             │
│ Motor block         │ Dose-dependent  │ Minimal (IT opioid)  │
│ Ambulation          │ Possible        │ YES — "walking epi"  │
│ Sacral spread       │ Variable        │ Better               │
│ Can convert to LSCS │ Yes (top up)    │ Yes (catheter)       │
│ Test catheter early │ Yes             │ No (spinal done 1st) │
│ Pruritus            │ Less            │ More (IT opioid)     │
│ PDPH risk           │ ~1–2.6%         │ Slightly higher      │
│ Best for            │ Slow onset ok,  │ Advanced labour,     │
│                     │ elective setting│ rapid analgesia need │
└─────────────────────┴─────────────────┴──────────────────────┘

IX. Complications Mnemonic — "BUMPED HF"

B — Blood patch needed (PDPH — post dural puncture headache)
U — Unintentional intravascular injection (→ LAST)
M — Motor block (dose-related)
P — Pruritus (intrathecal opioid)
E — Epidural haematoma / abscess (rare but catastrophic)
D — Dural puncture (1–2.6% labour epidurals)

H — Hypotension (most common — 10–30%)
F — Fever (epidural-associated maternal pyrexia)

X. Systemic Opioids — Quick Recall Table

┌──────────────────┬──────────┬────────────┬────────────────────┐
│ DRUG             │ ROUTE    │ ONSET      │ KEY CONCERN        │
├──────────────────┼──────────┼────────────┼────────────────────┤
│ Pethidine        │ IM/IV    │ 20–30 min  │ Active metabolite  │
│ (Meperidine)     │          │            │ normeperidine →    │
│                  │          │            │ neonatal CNS dep   │
│                  │          │            │ up to 72 hours     │
├──────────────────┼──────────┼────────────┼────────────────────┤
│ Fentanyl         │ IV/PCA   │ 1–2 min    │ Maternal sedation  │
├──────────────────┼──────────┼────────────┼────────────────────┤
│ Remifentanil     │ IV PCA   │ <1 min     │ BEST systemic opt  │
│                  │          │            │ Maternal resp.     │
│                  │          │            │ depression — 1:1   │
│                  │          │            │ nursing MANDATORY  │
├──────────────────┼──────────┼────────────┼────────────────────┤
│ Morphine         │ IM/IV    │ 20–30 min  │ Long-acting;       │
│                  │          │            │ crosses placenta   │
├──────────────────┼──────────┼────────────┼────────────────────┤
│ N₂O (Entonox)   │ Inhaled  │ 30–60 sec  │ Mild only; N+V     │
└──────────────────┴──────────┴────────────┴────────────────────┘

MNEMONIC for systemic options: "Please Find Really More Nitrous"
P — Pethidine
F — Fentanyl
R — Remifentanil (best)
M — Morphine
N — Nitrous oxide

XI. Effect on Labour — "NICE" Mnemonic

N — No increase in caesarean section rate
I — Initiation early is SAFE (no cervical dilation threshold)
C — Could mildly prolong SECOND stage only
E — Epidural is gold standard — Evidence Level I (meta-analysis)

XII. Full Pain Pathway Visual Summary

                        BRAIN (perception)
                             ▲
                             │
                    SPINOTHALAMIC TRACT
                             ▲
                             │
               ┌─────────────┴──────────────┐
               │                            │
          T10–L1                         S2–S4
          (DORSAL HORN)               (SACRAL CORD)
               ▲                            ▲
               │                            │
      SYMPATHETIC CHAIN             PUDENDAL NERVE
               ▲                            ▲
               │                            │
      HYPOGASTRIC PLEXUS           VAGINA / PERINEUM
               ▲                     PELVIC FLOOR
               │
     UTEROVAGINAL PLEXUS
               ▲
               │
    UTERUS + CERVIX ──────────────────── Distension
    (contractions, ischaemia,            + stretch
    bradykinin, substance P,             → somatic pain
    prostaglandins)
    → visceral pain

  ════ FIRST STAGE ════              ════ SECOND STAGE ════
  Block needed: T10–L1               Block needed: S2–S4
                                      + T10–L1 maintained

XIII. Non-Pharmacological Techniques — "WATCH BH"

W — Warm water (hydrotherapy)
A — Acupuncture / acupressure
T — TENS (transcutaneous electrical nerve stimulation)
C — Continuous support (doula / midwife)
H — Hypnosis

B — Breathing techniques (Lamaze, Bradley)
H — Hands-on massage

XIV. One-Page Exam Summary Box

╔══════════════════════════════════════════════════════════════════╗
║              LABOUR ANALGESIA — EXAM CHEAT SHEET                ║
╠══════════════════════════════════════════════════════════════════╣
║                                                                  ║
║  PAIN LEVELS:   1st stage → T10–L1 (visceral)                  ║
║                 2nd stage → S2–S4  (somatic) + T10–L1          ║
║                                                                  ║
║  BEST METHOD:   Epidural / CSE (neuraxial gold standard)        ║
║                                                                  ║
║  EPIDURAL DRUG: Bupivacaine 0.1% + Fentanyl 2 mcg/mL           ║
║                 Test dose: Lignocaine 1.5% + Adrenaline         ║
║                                                                  ║
║  CSE BENEFIT:   Fast onset, walking epidural, better sacral     ║
║                                                                  ║
║  SYSTEMIC BEST: Remifentanil PCA (needs 1:1 monitoring)         ║
║                                                                  ║
║  DOES NOT:      Increase LSCS rate                              ║
║                 Prolong first stage                              ║
║                                                                  ║
║  AVOID:         Ergometrine (in cardiac patients)               ║
║                 Large spinal in severe cardiac disease          ║
║                                                                  ║
║  COMPLICATIONS: Hypotension #1, PDPH, Motor block,             ║
║                 LAST (intravascular), High spinal               ║
║                                                                  ║
║  CONTRAINDIC:   Coagulopathy, ↑ICP, Refusal, Site infection    ║
╚══════════════════════════════════════════════════════════════════╝

Master Summary of All Mnemonics

Cardiac Arrest in Pregnancy — Management

I. Introduction (0.5 mark)

II. Causes — Mnemonic: "THE BASICS" (1 mark)

T — Thromboembolism (Pulmonary embolism — most common non-obstetric cause)
H — Haemorrhage (PPH, placenta praevia, abruption, uterine rupture)
E — Eclampsia / Hypertensive emergency / HELLP

B — Blood pressure drugs / Anaesthetic complications
    (High spinal, failed airway, LA toxicity — LAST)
A — Amniotic fluid embolism (AFE) — sudden cardiovascular collapse
S — Sepsis / septic shock
I — Ion / electrolyte — hypermagnesaemia, hyperkalaemia
C — Cardiac — peripartum cardiomyopathy, MI, aortic dissection
S — Stroke / intracranial haemorrhage

Other causes: anaphylaxis, trauma, aspiration, pulmonary hypertension, drug toxicity

III. Why Standard CPR is Inadequate in Pregnancy (1 mark)

┌─────────────────────────────────────────────────────────────────┐
│      WHY PREGNANCY MODIFIES CPR EFFECTIVENESS                   │
├──────────────────────────────┬──────────────────────────────────┤
│ PROBLEM                      │ MECHANISM                        │
├──────────────────────────────┼──────────────────────────────────┤
│ Aortocaval compression       │ Gravid uterus (≥20 wks)          │
│ (MOST CRITICAL)              │ compresses IVC + aorta in        │
│                              │ supine position → ↓ venous       │
│                              │ return → ↓ CO by 25–30%          │
├──────────────────────────────┼──────────────────────────────────┤
│ ↓ FRC                        │ Chest compressions less          │
│                              │ effective for ventilation        │
├──────────────────────────────┼──────────────────────────────────┤
│ ↑ O₂ consumption             │ Faster desaturation              │
├──────────────────────────────┼──────────────────────────────────┤
│ Difficult airway             │ Oedema, Mallampati worsens        │
├──────────────────────────────┼──────────────────────────────────┤
│ Full stomach                 │ High aspiration risk              │
├──────────────────────────────┼──────────────────────────────────┤
│ Elevated diaphragm           │ Alters chest compression angle    │
└──────────────────────────────┴──────────────────────────────────┘

CPR in pregnancy generates only 30–40% of normal cardiac output.
— Roberts & Hedges' Clinical Procedures in Emergency Medicine

IV. Immediate Management — The "4-4-5 Rule" Flowchart (3 marks)

            ─── MATERNAL CARDIAC ARREST RECOGNISED ───
                             │
                    CALL FOR HELP IMMEDIATELY
                 (Obstetric + Anaesthetic + Neonatal)
                             │
                             ▼
            ┌────────────────────────────────────────┐
            │       SIMULTANEOUSLY:                  │
            │  1. Start CHEST COMPRESSIONS           │
            │     • Hard, fast (100–120/min)         │
            │     • Full depth (5–6 cm)              │
            │     • HIGHER on sternum                │
            │       (one finger-breadth above        │
            │        normal landmark — due to        │
            │        elevated diaphragm)             │
            │                                        │
            │  2. LEFT UTERINE DISPLACEMENT (LUD)    │
            │     Manual: assistant pushes uterus    │
            │     to LEFT — relieves IVC compression │
            │     • DO NOT TILT TABLE (reduces       │
            │       compression effectiveness)       │
            │                                        │
            │  3. AIRWAY: RSI with cricoid pressure  │
            │     (high aspiration risk)             │
            │     • Use video laryngoscope if avail  │
            │     • Smaller ETT (6.0–7.0 mm)         │
            │                                        │
            │  4. OXYGENATION: 100% O₂               │
            │                                        │
            │  5. IV/IO ACCESS: 2 large-bore above   │
            │     diaphragm (femoral drainage may    │
            │     be impaired by uterus)             │
            └────────────────────────────────────────┘
                             │
                    ┌────────▼────────┐
                    │  ASSESS RHYTHM  │
                    └────────┬────────┘
               ┌─────────────┴──────────────┐
               ▼                            ▼
      SHOCKABLE                      NON-SHOCKABLE
   (VF / Pulseless VT)            (PEA / Asystole)
               │                            │
               ▼                            ▼
  DEFIBRILLATE (safe in          CONTINUE CPR + DRUGS
  pregnancy — standard         Identify and treat cause
  energy; remove fetal          ("THE BASICS")
  monitors)
               │
               ▼
        ◄ NO ROSC BY 4 MINUTES? ►
               │
               ▼
   ┌───────────────────────────────────┐
   │   RESUSCITATIVE HYSTEROTOMY      │
   │   (Perimortem Caesarean Section) │
   │   INITIATE at 4 minutes         │
   │   COMPLETE by 5 minutes          │
   │   Continue CPR throughout!       │
   └───────────────────────────────────┘

V. The Two Critical Modifications to AHA/ACLS (1 mark)

┌──────────────────────────────────────────────────────────────────┐
│    TWO MANDATORY PREGNANCY-SPECIFIC MODIFICATIONS                │
│                                                                  │
│  1. MANUAL LEFT UTERINE DISPLACEMENT (LUD)                      │
│     • Performed when uterus ≥ umbilicus (≥20 weeks)             │
│     • Relieves aortocaval compression                           │
│     • Increases venous return and CO by 25–30%                  │
│     • Assistant pushes uterus firmly to LEFT                    │
│     • DO NOT tilt the patient — reduces CPR effectiveness        │
│                                                                  │
│  2. PREPARE FOR RESUSCITATIVE HYSTEROTOMY                        │
│     • Do not wait for theatre — perform AT SITE OF ARREST        │
│     • Goal: initiate at 4 min, complete by 5 min of arrest       │
│     • ≥24 weeks gestation (uterus above umbilicus)               │
│     • Delivers fetus → relieves IVC → improves maternal CO       │
└──────────────────────────────────────────────────────────────────┘

VI. Drug Therapy in Pregnancy Cardiac Arrest (1 mark)

┌─────────────────────┬───────────────────┬────────────────────────┐
│ DRUG                │ DOSE / ROUTE      │ NOTE                   │
├─────────────────────┼───────────────────┼────────────────────────┤
│ Adrenaline          │ 1 mg IV q3–5 min  │ Standard dose — safe   │
│ (Epinephrine)       │                   │ in pregnancy           │
├─────────────────────┼───────────────────┼────────────────────────┤
│ Amiodarone          │ 300 mg IV bolus   │ For VF/VT              │
│                     │                   │ (preferred over        │
│                     │                   │ lignocaine)            │
├─────────────────────┼───────────────────┼────────────────────────┤
│ Sodium bicarbonate  │ 50 mmol IV        │ If prolonged arrest    │
├─────────────────────┼───────────────────┼────────────────────────┤
│ Calcium gluconate   │ 1 g IV slowly     │ Hypermagnesaemia       │
│                     │                   │ toxicity (eclampsia    │
│                     │                   │ patients on MgSO₄)     │
├─────────────────────┼───────────────────┼────────────────────────┤
│ Intralipid 20%      │ 1.5 mL/kg bolus   │ LA systemic toxicity   │
│                     │ then infusion     │ (LAST) — epidural      │
├─────────────────────┼───────────────────┼────────────────────────┤
│ Vasopressin         │ Not recommended   │ Replaced by adrenaline │
│                     │ in 2020 AHA       │ in current guidelines  │
└─────────────────────┴───────────────────┴────────────────────────┘

STOP MgSO₄ infusion immediately if arrest occurs.
GIVE calcium gluconate if Mg toxicity suspected.

VII. Resuscitative Hysterotomy (Perimortem CS) (1 mark)

INDICATION: Gestational age ≥24 weeks (uterus ≥ umbilicus)
            No ROSC despite 4 minutes of ACLS
            (Fetal viability secondary — procedure also improves maternal survival)

TIMING:     INITIATE at 4 minutes → COMPLETE by 5 minutes
            Beyond 20 minutes: virtually no survival for mother or fetus

LOCATION:   AT SITE OF ARREST — do NOT move to theatre

TECHNIQUE:
  • Continue CPR throughout the procedure
  • No anaesthesia needed (mother is in arrest)
  • Midline vertical skin incision: epigastrium → symphysis
  • Midline vertical uterine incision
  • Deliver fetus; clamp and cut cord
  • Begin neonatal resuscitation immediately

BENEFIT TO MOTHER:
  • Relieves aortocaval compression
  • Venous return ↑ 25–30%
  • Cardiac output improves → higher ROSC rates
  • Reduces O₂ demand

BENEFIT TO FETUS:
  • Best neonatal outcome if delivered within 5 min
  • Poor if >20 minutes from arrest

VIII. Cause-Specific Management Summary (0.5 mark)

IX. Post-ROSC Care (0.5 mark)

• Transfer to ICU immediately
• Targeted temperature management (TTM): 32–36°C if comatose post-ROSC (neuroprotection); fetal monitoring required as hypothermia affects fetus
• Haemodynamic optimisation: MAP ≥65 mmHg, SpO₂ 94–98%, normocapnia
• Identify and treat underlying cause
• Fetal monitoring continuously; emergency LSCS if fetal distress
• Multidisciplinary review (obstetrics, cardiology, intensivist)

X. Summary Box — "The 4-4-5 Rule" (integrated above)

╔══════════════════════════════════════════════════════════════════╗
║         CARDIAC ARREST IN PREGNANCY — EXAM CORE POINTS          ║
╠══════════════════════════════════════════════════════════════════╣
║                                                                  ║
║  CAUSES:    "THE BASICS" (Thromboembolism, Haemorrhage,         ║
║              Eclampsia, Bad drugs/LAST, AFE, Sepsis,            ║
║              Ions, Cardiac, Stroke)                              ║
║                                                                  ║
║  KEY MODS:  1. Left Uterine Displacement (LUD) — Manual         ║
║             2. Prepare Resuscitative Hysterotomy                 ║
║                                                                  ║
║  CPR:       Higher hand placement; Hard + Fast; 100% O₂         ║
║             RSI airway; IV access above diaphragm               ║
║                                                                  ║
║  DRUGS:     Adrenaline 1 mg q3–5 min; Amiodarone for VF         ║
║             Ca gluconate if MgSO₄ toxicity                      ║
║             Intralipid 20% if LAST                               ║
║                                                                  ║
║  TIMING:    4 min → initiate hysterotomy                        ║
║             5 min → complete delivery                            ║
║             >20 min → virtually no survival                      ║
║                                                                  ║
║  LOCATION:  AT THE BEDSIDE — never move to OT                    ║
║                                                                  ║
║  POST-ROSC: ICU, TTM if comatose, treat underlying cause        ║
╚══════════════════════════════════════════════════════════════════╝

References

• Barash, Cullen & Stoelting's Clinical Anesthesia, 9e — Maternal Mortality & Cardiac Arrest
• Morgan & Mikhail's Clinical Anesthesiology, 7e — Obstetric Emergencies
• Rosen's Emergency Medicine — Resuscitative Hysterotomy
• Roberts & Hedges' Clinical Procedures in Emergency Medicine — Perimortem Caesarean Section
• AHA Scientific Statement: Cardiac Arrest in Pregnancy — Circulation, 2015