Anaesthesia for Obstetric Patient

CHALLENGESAltered physiologyPresence of fetus and gravid

uterusAortocaval compression Reflux and possible aspiration

of gastric contents Intubation difficulties Increased oxygen consumption

BLOOD AND CIRCULATORY CHANGES - - Heart rate: ↑ 15% - Stroke volume : ↑ 35%- Cardiac output : ↑ 30-40% - Blood volume : ↑ 35-40%

- Red cell : ↑ 30% , but - plasma volume : ↑ 50% physiological

anaemia

- Pain : ↑ SV and CO 40%

Anaesthetic implications1. High cardiac output Presence of systemic or pulmonary

hypertension, severe cardiac disease may induce cardiac failure and APO. May be obtunded by RA.

2. Venous distension Due to back pressure to the azygos and

epidural veins by the gravid uterus. Decrease spinal LA requirement and

increase risk of bloody tap.

Anaesthetic implications3. Aortocaval compression Due to compression of aorta and IVC by the

fetus causing ↓VR and CO. Clinical features (may be masked ↓ GA/RA)

Symptomatic : maternal SOB and dizziness, Occult : reduced placental flow, fetal

hypoxia Relieved by lateral tilt or pelvic wedge

RESPIRATORY CHANGESAnatomy Engorged airway

apparatus: nose, vocal cords, arytenoids

Lung volumesVT, MV, RR ↑- due to ↑O2 consumption and CO2

productionFRC, ERV ,RV ↓- due to upwards diaphragmatic

displacementIC ↑ , VC no changes

RESPIRATORY CHANGES

Anaesthetic implications1. Functional Residual Capacity ↓:

Smaller O2 reservoir, high O2 consumption causing rapid desaturation.

Mandatory to preoxygenate.

2. Engorged airway: Difficulty with laryngoscopy and tracheal

intubation. Compounded with large breast, ↑weight and short neck. Use short handle.

Airway obstruction is more likely to occur during sedation and anaesthesia.

Oral mucosa easily traumatised.

GASTROINTESTINAL CHANGES↑IAP, ↑gastric volume and acidity.

pH<2.5 with volume 20-25mls ~ Mendelson’s syndrome

↓LOS tone, gastric and intestinal mobilityDelayed gastric emptying in active phase of labour. Increase risk of aspiration

Anaesthetic implications:Neutralisation of gastric acid and RSI with cricoid pressure

(for GA) are mandatory(Sodium citrate, H2 antagonist)

PREOPERATIVE ASSESSMENTHistory- Age, parity, gestation period- Pregnancy complication- Fasting period- Medical, surgical and anaesthetic history- Allergies and medication history- Indication - Discussion and counselling on anaesthetic

technique - Consent

Physical examination

Airway assessmentCardiorespiratory

systemLumbar spine

InvestigationFBCRenal profileCoagulation profileGSH 2 unit PC

PREOPERATIVE ASSESSMENT

General preparationElective caseFast from 12

midnightOral Ranitidine

150mg ON and OM0.3M 30ml Na

citrate on OT call

Emergency caseIV Ranitidine 50mg

stat0.3M 30ml Na

citrate 30 min before op

IV Metoclopramide 10mg at induction

GA Advantages Shorter induction time Lower failure rate Better CVS control Rapid control of convulsion in

eclamptic pt Pt cooperation not required

Disadvantages Difficult airway management Risk of regurgitation and aspiration Awareness Stress response on

induction/reversal PONV Inadequate analgesia post op Hangover effect

RAAdvantages Avoid problems related to

GA Awake patient Effective analgesia

Disadvantages Sympathetic blockade Inadequate/failed block PDPH LA toxicity: inadvertent IV or

intrathecal injection Complications of RA –

epidural abscess, haematoma

REGIONAL ANAESTHESIAContraindication- Patient refusal- Local/systemic

infection- Hypovolaemic state- Fixed cardiac output

state- Coagulopathy- Unskilled/

unsupervised operator

Choices:Spinal/ Epidural/ CSELocal protocol

Post RA:- Left lateral tilt - Oxygen supplement- Check blockade

level :T4- Monitor BP, PR, RR,

SpO2

GENERAL ANAESTHESIAWhen?- RA contraindicated- RA potentially

dangerous- RA takes long time to

be established- RA inadequate block

Preparation- Drugs to be prepared:

- anaesthetics - resuscitation

- Airway device: airways, ETT & various sizes of laryngoscope blades

- Airway adjuncts: to be kept nearby

- Standard monitoring- Reliable IV access- Surgeon in OT

GENERAL ANAESTHESIAINDUCTION OF GAEnsure 2 skilled assistants presentWedge below the right hip to allow uterine

displacementPreoxygenate with 10 l/minute for 3 minutesAdminister Thiopentone 4-5mg/kg, Suxamethonium

100 mgCricoid pressure is applied Ensure correct ETT positionMedium acting muscle relaxant after Suxamethonium

has worn offNO OPIOID till baby is delivered.

GENERAL ANAESTHESIAMAINTENANCE OF GAO2:N2O ratio 1:1 with volatile MAC<1Aggressive treatment of hypotensionAfter baby delivered, change O2 : N2O to 1:2 ratio IV Oxytocin 5U slowly followed by infusion 40-80U over 4

hours IV opioid: Morphine 5mgAssess blood lossRectal Diclofenac 100mg and SC LA infiltration Reversal and awake extubationMove the patient to the recovery area

PROBLEMS WITH GA IN MATERNITY PATIENTS

1. Awareness• Incidence 0.7 – 1.5%• Due to :

i) no sedative premedications, ii) high FiO2 iii) low volatile concentration used intraoperatively iv) avoidance of opioids

PROBLEMS WITH GA IN MATERNITY PATIENTS

2. Pulmonary aspiration• pH<2.5 with volume >25mls ~critical factor• Signs: - intraop bronchospasm

- desaturation- postop tachypnoea and cyanosis

• Mx: - Immediate head down with oral/ETT suction, may need bronchial lavage.

- Treat bronchospasm with bronchodilator.

- Increase FiO2 and PEEP.

PROBLEMS WITH GA IN MATERNITY PATIENTS

3. Difficult intubation• FaiIed intubation incidence 1:280 compared

with 1:2200 in non-pregnant. • Aim: - maintain oxygenation,

- avoid aspiration

HEAD ELEVATED LARYNGOSCOPY POSITION “stacking”

MATERNAL DISEASES IN PREGNANCY1. Hypertensive disorders 11-17%

2. Gestational diabetes 5-11%

3. Valvular heart disease (less common)

HYPERTENSIVE DISORDERS OF PREGNANCY

Definition: BP > 140/90mmHg after 20 weeks of gestation

and settles within 6 weeks of delivery

Types:Gestational (without proteinuria)Preeclampsia (proteinuria >0.3g/day)

Severe preeclampsiaEclampsia

SEVERE PREECLAMPSIA

Def: BP >160/110 mmHg with proteinuria >5g/d associated with signs of organ hypoperfusion:

Oliguria < 500ml/dayCerebral disturbancesEpigastric /RUQ painPulmonary oedemaHELLP syndromes

Management:Anti hypertensiveLabour analgesiaEarly delivery

ECLAMPSIA

Def: Generalized convulsion during hypertensive pregnancy up to day 7 of post delivery.

Management:ABCAbort seizureIV MgSO4 Anti hypertensiveEarly delivery

CARDIOVASCULAR DISEASES IN PREGNANCY

Clinical features:SOB at rest, ↓ET,

orthopnoeaPedal oedemaTachycardia, systolic

murmurs, S3, basal rales

Recognition is important

Management:Multidisciplinary

consultationReferral to tertiary

centreEarly planning of

mode of delivery

ANY QUESTION ?