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You are in Home >> Exams >> Mitchell Anaesthetic Notes


Obstetric Anaesthesia

Created: 1/9/2006
Updated: 8/1/2007
 

Cardiac disease in pregnancy

  • Cardiac stresses
    • Pregnancy, labour, surgery (lower uterine segment Caesarean section [LUSCS]), blood loss
    • Cardiac disease may worsen in pregnancy
  • Anaesthetic interventions
    • Major regional blockade
      • Objective is to minimize physiological disturbance
        • Choice of drug: opioid vs local anaesthetic
        • Titration of drug to minimize high block
        • Volume loading to maintain preload
        • Posturing to maintain preload
        • Use of vasopressors
      • Degree of concern
        • Normal patient
        • Disease will improve with block, e.g. AR
        • Disease will worsen with block, e.g. AS
      • Monitoring
        • Routine
        • HDU
        • ICU
      • Blockade for analgesia is safer than for anaesthesia
    • General anaesthesia
      • Objective is to minimize physiological disturbance
        • Modified RSI
          • e.g. more fentanyl, less thiopentone
        • Cardiac induction
          • May compromise safe airway
  • General management of cardiac disease in pregnancy
    • Workup
      • Nature of defect
      • Severity, e.g. NYHA grading
      • Optimization, e.g. valve replacement, medical therapy
      • Assessment of likely outcome
        • Counselling patient re termination
    • Objectives
      • Survive to viability and early Caesarean (e.g. 32/40)
      • Aim for normal labour with monitoring
    • Anaesthetic plan
      • Regional suitable for analgesia or anaesthesia?
      • GA preferred?
      • Technique, level of care pre- and post-op

Management of post-partum haemorrhage for EUA

  • Post-partum haemorrhage
    • >600 ml blood loss from birth canal from third stage to 24 h post-delivery
  • Surgery
    • High risk, emergency surgery
    • Causes: uterine atony, retained products, vaginal or uterine laceration
  • Preop
    • Assessment
      • Deterine reason for EUA
      • Define risk of procedure
      • Patient
        • Concurrent disease, e.g. PE
        • Resuscitation status
        • Bloods, crossmatch, Hb
      • Anaesthesia
        • Epidural in situ?
        • IV access
        • Fluid management
        • Regional versus GA
          • Determined by urgency, haemodynamic stability, patient preference
      • Premedication
        • Effervescent ranitidine
        • O2 by mask
        • Syntocinon infusion to continue
  • Induction
    • Rapid Sequence for GA
      • Equipment, suction, drugs
      • Preoxygenation
      • Cricoid, thiopentone, suxamethonium
      • ETT
    • Spinal or epidural or CSE
  • Maintenance
    • Reduced MAC requirement, volatiles cause uterine relaxation
      • Low volatile use unless uterine relaxation required
    • Physiological hypocapnia
    • Surgical issues
      • Haemorrhage, coagulopathy, warming of infusions
      • Oxytocic agents
      • Uterine relaxants: volatiles, GTN
  • Extubation
    • When awake and protecting airway
  • Postop
    • Ward/HDU/ICU as indicated

Management of 160 kg female for Caesarean section 

  • Surgery
    • Elective, urgent or emergency
    • Determines opportunity for optimization
  • Risk factors
    • Term pregnancy
      • Airway: oedema, vascularity, risk of difficult intubation, risk of aspiration
      • Ventilation: decreased FRC, increaed O2 requirement
      • Circulatory: increased CO, increased blood volume, ACC
    • Surgery
      • Haemorrhage
      • Embolism: amniotic fluid, air
    • Obesity
      • Airway difficulty
      • Increased gastric volume, decreased pH
      • Increased O2 requirement
      • Difficulty ventilating
      • Difficult access for IV, blocks
  • Preoperative
    • Assessment
      • Pregnancy, complications
      • Concurrent disease
      • Medications, allergies…
    • Premedication
      • Non-particulate antacid, sodium citrate: increased gastric pH
      • H2 antagonist, metoclopramide: increased pH, increased motility
  • Intraoperative
    • Positioning
      • Supine with left lateral tilt 15°
      • Avoid aorto-caval compression
    • Monitoring
      • ECG, SpO2, NIBP on frequent cycle and manual BP cuff
      • Arterial pressure if likely to be unstable
      • CTG or doppler prior to positioning for surgery
      • Supplemental O2 for all mothers
    • Regional
      • Advantages
        • Avoids need to intubate potentially difficult airway
        • Spinal may be as fast as GA in experienced hands
        • Preemptive analgesia, reduced postoperative analgesic requirement
        • Allows greater experience of birth, partner present
        • Often preferred by patient
      • Disadvantages
        • May delay surgery, especially epidural
        • Spinal is of fixed duration, lacks flexibility
        • Complications
          • Failed block, hypotension, local anaesthetic toxicity, neuropraxia, PDPH
          • Minimized with careful technique: fluid loading, pressors…
        • Obese patient may require longer needle, increased technical difficulty, CSE is not possible with long epidural needle
      • Epidural
        • Lumbar epidural catheter
        • Suitable for urgent procedure if
          • Haemodynamically stable, block established
        • Bolus lidocaine 2% with adrenaline and bicarbonate, 5 ml aliquots to T4
        • Additional epidural narcotic (fentanyl 100 µg or pethidine 50 mg) improves analgesia
        • May be combined with spinal (CSE)
        • May be supplemented intraoperatively
      • Spinal
        • L2-3 or L3-4
        • Fine pencil-point needle 26 g minimizes PDPH
        • Hyperbaric bupivacaine 0.5% 2.2-2.5 ml
        • Fentanyl 10-20 µg
        • Posture for block to T4
        • Test block with cold or painful stimulus
    • General
      • Advantages
        • Reliable and rapid onset of anaesthesia
        • Greater control of airway, ventilation and haemodynamics
      • Disadvantages
        • Potential for failed intubation, aspiration
          • Major causes of anaesthetic-related death in pregnancy
        • Greater post-operative narcotic requirement
        • Neonatal depression from volatiles, N2O and induction drugs
      • Rapid sequence induction
        • Required in all pregnant women after early second trimester or with other indications
        • Suction and difficult airway equipment must be at hand
        • Preoxygenation: 100% O2 by mask to denitrogenate FRC
        • Cricoid pressure
        • Thiopentone (4 mg/kg), suxamethonium (1.5 mg/kg) may be less in obese, correct towards LBM
        • Laryngoscopy, cuffed ETT
      • Maintenance
        • O2/N2O/isoflurane: FiO2 = 50%, isoflurane = 1 MAC
        • Higher FiO2 and PIP required with obese patient
        • Increased sensitivity to non-depolarizing relaxants, esp. with Mg2+
        • Relaxants do not cross placenta significantly
        • Minimal narcotics prior to delivery, then morphine 0.2-0.5 mg/kg
    • Post-delivery
      • Oxytocics
        • Oxytocin 5-20 U plus infusion
        • Ergometrine 0.25-0.5 mg IV or IM if continued bleeding
      • Emergence
        • Extubation when awake and protecting airway
  • Postoperative
    • Analgesia, antiemetics
    • Appropriate review

Justify an epidural test dose in obstetrics and contraindications to epidural for LUSC

  • Test dose
    • Purpose
      • Determine incorrect placement of epidural catheter
        • Intravascular or subarachnoid or subdural
      • Aspiration is a useful test if positive: blood or CSF, but may be falsely negative
    • Procedure
      • After placement of the catheter, 3 ml of local anaesthetic solution (typically bupivacaine 0.25% or lidocaine 1%) containing adrenaline 5 µg/ml is administered
      • The heart rate is observed for a rapid rise of 20-30 bpm in response to intravascular adrenaline
      • The degree of sensory and motor blockade is observed after 3-5 min for a dense spinal block as high as T10
    • Rationale
      • The potential morbidity from incorrect placement of an epidural bolus dose can be severe
        • Bupivacaine 25-75 mg or lidocaine 200-400 mg administered intravascularly can cause fitting due to neurotoxicity and cardiac arrest due to Type I antidysrhythmic effect
        • The same dose given subarachnoid may cause a total spinal requiring urgent intubation and ventilation
      • The cost or risk associated with a test dose is small: a 3-5 min delay in establishing a block
      • The test is not 100% sensitive or specific, especially in labouring women in whom the heart rate is typically high and variable, but it is the best readily available and rapid test
      • Contrast epidurography may be a better test, but involves fluoroscopy, requiring a radiation dose, and substantial delay and cost
  • Absolute contraindications
    • Refusal by a competent patient
    • Infection at the site of potential insertion
    • Hypovolaemic shock
    • Coagulopathy, severe thrombocytopenia
    • Intellectual disability or other reason for being unable to cooperate
  • Relative contraindications
    • Urgency of surgery, delay in establishing block may be 20 minutes
    • Unstable neurological disease
    • Cardiovascular disease requiring maintenance of SVR, e.g. severe aortic stenosis
    • Treatment with anticoagulants, aspirin or other NSAIDs
    • Disease likely to cause technical difficulty or failure, e.g. ankylosing spondylitis

Outline management of a 32 week pregnant woman who fits at home

  • Immediate management
    • ABCDE
    • Lateral position, clear airway
    • Expired air resuscitation if not breathing, oxygen when available
    • External cardiac massage if no output
      • Requires supine position with left lateral uterine displacement
    • Summon assistance: ambulance
  • Aetiology
    • Eclampsia
    • Organic brain problem
      • Idiopathic epilepsy
      • Arteriovenous malformation
      • Tumour
    • Trauma
    • Metabolic disturbance
      • Drug withdrawal
      • Uraemia, hypoglycaemia, hyponatraemia etc.
  • General management
    • Once patient is well-oxygenated, fit is terminated and she is transported to a suitable hospital, the cause of the fit needs to be determined
    • Unless another cause is found, the aetiology is assumed to be eclampsia
  • Eclampsia
    • Immediate management
      • ABCDE as above
      • Mg2+ 2-4 g IV may terminate fit
    • Incidence
      • Preeclampsia 30 per 1000 births
        • Most common in young primigravidas
      • Eclampsia 0.4 per 1000 births
        • 44% fit before delivery
        • 37% during delivery
        • 19% after delivery
    • Management
      • Definitive management is delivery of the foetus and placenta
      • Examine and test for complications
        • Hypertension, proteinuria, thrombocytopenia, hepatic dysfunction
        • Growth-retarded or distressed foetus
      • Monitoring
        • Fetal well-being: CTG
        • Mother: NIBP or IABP, urinary catheter, possibly CVC or PA catheter
        • Best managed in HDU or labour ward if adequately equipped
      • Magnesium
        • Anticonvulsant, vasodilator, tocolytic, bronchodilator, decreased renin, decreased ACE, decreased platelet activity, decreased prostacyclin release
      • Antihypertensives
        • Hydralazine, α-methyldopa, clonidine, prazosin, labetalol, nifedipine, nitrates
      • Fetal management and delivery
        • Best done by experienced obstetrician
  • Epilepsy
    • Immediate management
      • Fits usually self-limiting
      • Administer oxygen
      • Fit can be terminated with barbiturate or benzodiazepine if prolonged
    • Incidence 50 per 100,000
    • Pregnancy
      • May increase frequency of fits
        • Possibly due to increased clearance and altered distribution of drugs, electrolyte changes
      • Antiepileptic medication may be teratogenic
        • Phenytoin --> cleft lip and palate, cardiac lesions, digital hypoplasia
      • Increased incidence of preeclampsia, complications and intervention
    • Management
      • Careful monitoring of blood levels of anticonvulsant and adjustment of dose

Outline differences between spinal and epidural for LUSCS

  • Requirement
    • Both
      • Surgical anaesthesia to T4
      • Adequate duration for surgery
  • Anatomy, technique
    • Both
      • Lumbar technique midline or paramedian
      • Sitting or lateral position
    • Epidural
      • Probably safer in lateral position (less risk of dural puncture)
      • Tuohy needle 16 g-19 g used to approach epidural space
      • Space identified with LOR to air or saline
      • Catheter passed into space or single dose of anaesthetic given
      • Test for incorrect placement with aspiration and test dose of adrenaline-containing solution
    • Spinal
      • Commonly easier in sitting position
      • Pencil point needle 25g-27g used to enter subarachnoid space
      • Space identified with “pop” through dura and return of CSF
      • Single dose of anaesthetic
      • Clearer confirmation of correct placement of drug
  • Indications, contraindications
    • Safe techniques for elective and urgent LUSCS
      • Spinal usually faster to get the case started
      • Epidural can be fast if block already establised
      • Both thought to be safer than GA (no conclusive evidence)
    • Coagulopathy or thrombocytopenia: both contraindicated, but epidural more strongly
    • Haemodynamic compromise, e.g. aortic or mitral stenosis
      • Relative contraindication to regional
      • Fall in SVR more rapid and uncontrolled with spinal
      • May be safer to use graduated epidural
  • Drugs used
    • Epidural
      • Local anaesthetic: lidocaine 2%, ropivacaine 0.5-1%, bupivacaine 0.5%
      • Dose up to 20 ml of 2% lidocaine
      • Addition of fentanyl or pethidine or morphine
    • Spinal
      • Local anaesthetic: bupivacaine 0.5%, cinchocaine (obsolete)
      • Dose typically 2.2-2.5 ml of hyperbaric bupivacaine 0.5%
      • Addition of fentanyl 10-20 µg or morphine 100-200 µg
  • Reliability, duration
    • Spinal a more reliable technique
      • Clearer end-point
      • Denser block
      • Fixed duration, typically 45-60 min of good surgical anaesthesia
    • Epidural
      • May be patchy, unilateral
      • Intraoperative supplementation allows longer duration
  • Complications, risks
    • Both
      • Major risks of anaesthetic
        • Failed block, inadequate block, headache, infection, neuropraxia, drug toxicity, hypotension
      • Major risks of surgery
        • Haemorrhage, embolism, nausea, vomiting, infection probably unaffected by anaesthetic technique
    • Spinal
      • Less risk of failure, headache, local anaesthetic toxicity
      • Minor risk of respiratory depression with intrathecal morphine
    • Epidural
      • Larger dose of local anaesthetic, possible intravascular injection so greater risk of toxicity

Management of a term female with moderate aortic stenosis for elective Caesarean section

  • Surgery
    • Elective, moderate risk
  • Preoperative
    • Assessment
      • Routine anaesthetic assessment
      • Obstetric issues
        • Size, obesity
        • Airway compromise
        • Obstetric complications, e.g. preeclampsia
        • Crossmatch
      • Aortic stenosis
        • Severity moderate
        • History
          • Symptoms of severity
            • Exercise limitation, dyspnoea, angina, drop attacks
        • Examination
          • BP, pulse character
          • Murmur, radiation
          • Signs of failure: creps, oedema
        • Investigations
          • CXR, ECG, echocardiographic findings required
          • Catheter study results if performed
    • Optimize condition
      • Consult with cardiologist, obstetrician
      • Symptoms often worsen with pregnancy, fall in SVR
      • Treat failure
      • Valvuloplasty if indicated
    • Premedication
      • Ranitidine or antacid
      • Benzodiazepine if anxiolytic required
    • Transport
      • Left lateral position
      • Supplemental O2
  • Intraoperative
    • Monitoring and access
      • Large bore IV access
      • Routine monitoring, plus
      • Arterial line
      • If severe consider PA catheter or TOE
    • Induction
      • Position with 15° left lateral tilt and uterine displacement
      • Preload with fluid
      • Prepare resuscitation drugs
        • Vasoconstrictor agents: metaraminol, phenylephrine
      • Regional
        • Graduated epidural
          • L2-3 or 3-4 catheter
          • Incremental boluses of lidocaine plus fentanyl to block to T4
          • Maintain contractility, HR and BP with pressors and fluid
      • General
        • Preoxygenation, cricoid pressure
        • Narcotic plus midazolam titrated to unconsciousness
        • Relaxation with suxamethonium
        • Oral intubation
        • Pressors as needed to maintain BP
  • Maintenance
  • General
  • Remifentanyl infusion or
  • N2O, O2, low concentration volatile
  • Slow administration of required syntocinon to prevent hypotension
  • Expect neonate to require resuscitation: naloxone ± ventilation
  • Aggressive replacement of volume loss
  • Emergence
  • Awake extubation in lateral position
  • May be delayed by high narcotic dose
  • Postoperative
  • HDU or ICU care
  • Continue ECG, arterial BP monitoring
  • Analgesia with morphine PCA plus NSAID and paracetamol

Anaesthesia for LUSCS  

  • Rate 62,000/year
  • Indications
    • Distress 20%
    • Malpresentation 15-20%
    • FTP 40%
    • Previous Caesarean 30%
  • Maternal death rate 1/10000
  • Technique
    • Regional vs GA vs local
      • Urgency, patient choice, anaesthetic opinion, indication for LUSCS
      • Complications of pregnancy (PE, placenta praevia…)
      • Classify as needs of: mother, baby, obstetrician
    • GA
      • Advantages
        • Rapid, reliable, good conditions, safer in unstable conditions or coagulopathy, familiar to patients
      • Disadvantages
        • Requirement for airway control, awareness, fetal depression, increased analgesic requirement, decreased breast feeding at 6 months, no participation in birth
    • Regional
      • Advantages
        • Participation, no airway problems, decreased analgesic requirement, better Apgar at 1 minute
      • Disadvantages
        • Limited duration, ? more hypotension, inadequate block, PDPH, neurological complications, total spinal, difficult conversion to GA, LA toxicity from IV injection
      • Assessing block
        • T4-T6 required for surgery
        • Consider resiting epidural or CSE for poor block
      • Contraindications
        • Refusal, thrombocytopenia, coagulopathy, conditions markedly worsened by afterload reduction (e.g. AS), urgency of induction
      • Premedication
        • Possibility of conversion to GA, so non-particulate antacid immediately before, H2 blocker or metoclopramide premedication
      • Complications
        • Hypotension
          • Prevent with fluid load (0.5-1 L), left lateral tilt, suitable spinal dose or titrated epidural, early use of ephedrine, close monitoring of BP and symptoms of hypotension
        • High block, inadequate block
      • Supplemental oxygen
        • Increased materal and foetal PO2, given during block in case of hypotension before uterine incision: load with O2 before reduced placental perfusion
      • Doses
        • In recipes
    • GA
      • Complications
        • Aspiration, failed intubation management, aortocaval compression,
      • Priorities
        • Maintain oxygenation, adequate ventilation (PCO2 32-34), minimize incision to delivery time, avoid depressant drugs
      • Initial gas mixture: 50:50 + 0.5 MAC volatile (initial overpressure)
      • Reduced anaesthetic requirements (25-40% MAC reduction)
      • Reduced FRC --> rapid hypoxia and rapid equilibration of anaesthetic gases
      • Awareness most likely: intubation and incision

Perinatal mortality 1997

  • Declining birth rate
    • 62,000 in 1997, similar number of births since 1962, but rate has fallen from 21.1 per 1000 population to 13.4
  • Declining perinatal deaths
    • 429 deaths, 6.9 per 1000 births
      • 269 stillborn, 160 before 28 days post-delivery
    • Rates are lower using WHO criteria (4.3 per 1000 births)
      • Count infants = 1000 g or 28 weeks rather than 500 g or 22 weeks
  • Preventable causes of perinatal death
    • Mostly related to obstetric practice
    • Some anaesthetic relevance
      • Initiate management of maternal illness prior to transfer (e.g. controlling hypertension or treating preeclampsia)
      • Avoid surgery unless mandatory
      • Discourage smoking in pregnancy

Maternal mortality 1997

  • Older population of mothers
    • Median age increased from 27 in 1984 to 30 in 1997
    • Perinatal mortality rate increases with maternal age
  • Method of delivery has changed
    • 1984 16% forceps, 15% Caesarean
    • 1997 10% forceps, 20% Caesarean
  • Duration of hospital stay has fallen
    • 1985 84% stayed = 5 days
    • 1997 42% stayed = 5 days
  • Maternal death
    • Rate continues to fall from 0.66 per 1000 births in 1953 to 0.08 in 1997
    • Only five deaths reported
      • 36 yo G4P2 29/40 - massive PE with history of DVT
      • 35 yo P4 41/40 - vaginal haemorrhage, Caesarean, failed intubation
      • 32 yo P1 24/40 - obese asthmatic hypertensive smoker, arrhythmia
      • 32 yo P2 34/40 - hypertensive, SAH in doctor's rooms
      • 26 yo P0 - recurrent glioma

Analgesia in labour

  • Schema for examining analgesic techniques
    • Evidence
      • Basic science
      • Clinical
    • Efficacy
    • Costs
    • Complications
      • Mother
      • Baby
    • Monitoring reqirement
    • Technique, skill
    • Effect on obstetric outcome
  • Analgesic options
    • Psychological
      • Education, visualization…
    • Pharmacological
      • Systemic: N2O, pethidine
      • Regional: epidural, spinal, nerve blocks
  • Indications for early epidural
    • Preeclampsia without severe thrombocytopenia
    • Serious contraindication to GA
      • Failed intubation, morbid obesity
    • Trial of scar
    • Twins
    • Poor cardiac reserve
    • Likely Caesarean section
  • Indications for GA in labour ward
    • Stuck second twin or shoulder dystocia without an epidural
  • Difficulties in pregnancy with epidural
    • More likely to be fat, oedematous
    • Increased lordosis, difficulty positioning
    • Contractions increase risk of movement or bloody tap (?10%)
    • Reduced volume of epidural space and increased sensitivity to LA
    • Raised CO, low SVR before block
    • Remote location
    • Increased O2 consumption, ineffective CPR in pregnancy if complicated
  • Contraindications
    • Risk/benefit consideration
      • Usual technique
      • Modified technique
    • Fever
      • Generalized sepsis vs local vs febrile due to labour alone
      • Epidural abscess is rare even in septic patients
      • Modification of technique
        • More likely to use a agonist for hypotension
        • Close onservation of neurological status post-procedure
    • Thrombocytopenia
      • <80 usually contraindicated
      • >100 usually safe unless other contraindication
      • 80-100 consider other options: systemic analgesia, GA for Caesarean, spinal with 27g needle
    • Hypovolaemia
    • Valvular heart disease
      • Modified technique usually suitable
        • Gradual development of block
        • Closer monitoring

Tocolysis

  • Preterm labour
    • Preterm delivery (before 37 weeks) incidence 7%
    • Increased risk of respiratory distress, hypothermia, hypoglycaemia, jaundice
  • Risk factors
    • Young, low body weight, low socioeconomic class, unsupported, smokers
    • Previous preterm delivery, early bleeding, heart disease, cervical incompetence, multiple pregnancy, premature rupture of membranes
  • Causes
    • Medical induction
    • Infection
      • Streptococci, mycoplasma, fusiform bacilli
      • Increased IL-1ß, IL-6, TNF-α, --> PG production --> labour
      • Risk might be reduced with antibiotics for Gardnerella vaginosis
    • Ruptured membranes
    • Multiple pregnancy
      • Rising incidence with IVF, GIFT etc.
      • 1985-95: twins 10 to 14 per 1000 births, triplets 0.14 to 0.44
    • Polyhydramnios, intrauterine death, fetal abnormality, uterine abnormality, cervical incompetence
  • Diagnosis
    • Cervical dilatation too late for treatment
    • Fetal fibronectin in vaginal mucus unreliable
    • Diagnosis is clinical, 30-40% false positive
  • Management
    • Tocolytic drugs
      • Effective for less than 48 hours
        • Time for transfer or steroids
        • Greatest gains in 25-30 week gestations
      • β-agonists
        • Salbutamol 100 µg bolus
      • MgSO4
        • Muscle weakness
      • Nitrates
        • GTN best acute agent (first report 1986)
          • 200-600 µg dose IV
          • Onset 90 s, duration 3-5 min
          • Surprisingly little hypotension
      • Indomethacin
        • Causes DA closure after 34 weeks --> pulmonary hypertension
      • Ca2+ channel blockers
        • Nifedipine --> hypotension, uteroplacental flow dysfunction
      • In trials
        • Atosiban (oxytocin blocker), nimesulide (COX-II inhibitor)
      • Obsolete
        • Alcohol, isoxuprine, amyl nitrite
      • Contraindications
        • Chorioamnionitis
    • Antibiotics for ruptured membranes (unproven)
    • Steroids to prevent neonatal respiratory distress
    • Mode of delivery depends on presentation
    • Delivery should be in a centre with NICU
  • Other uterine relaxants
    • Volatile agents (and cyclopropane)
      • MAC equipotent
    • Indications
      • Tocolysis (above)
      • Manipulative delivery
        • Malpresentation, breech, second twin, abnormal uterine anatomy
      • Manual removal of placenta
      • Acute uterine inversion
        • Pain, bleeding, vagal discharge, air embolism, venous congestion and difficulty reducing
      • Acute hypertonus
        • Drug-induced, following axial blockade
      • Intrauterine surgery

Antenatal class


Analgesia in labour

  • Historical perspective
    • e.g. Queen Victoria and chloroform
  • Potential benefit of analgesia in labour
    • Maternal distress
    • Possible tocolytic effect of endogenous catecholamines
  • Epidemiology
    • Caesarean section rate 20-25%
    • Epidural analgesia in primiparas approximately 50%
  • Analgesic options
    • Psychological
      • Visualization, relaxation
    • Simple physical
      • Position, heat, massage
    • Pharmacological
      • Systemic
        • Oral analgesics
        • Narcotics, N2O
      • Regional
        • Epidual
        • Spinal
        • CSE
  • For various techniques
    • Basic mechanism
    • Safety, efficacy
    • Advantages, disadvantages
    • Complications

Anaesthesia for Caesarian section

  • General
    • Indications
    • Advantages, disadvantages
  • Regional
    • Spinal vs epidural
    • Advantages, disadvantages
  • Post-operative analgesia

Foetal monitoring


Antenatal 

  • Noninvasive
    • Simple
      • Auscultation for foetal heart
      • Palpation of uterus, fundal height (cm above symphysis pubis = gestational age - 20)
      • Kick chart
    • Complex
      • Ultrasound
        • Head and abdominal circumference
        • Amniotic fluid index
        • Anatomical anomalies
        • Doppler flows in umbilical arteries
      • Cardiotocography
      • Biophysical profile
        • Scoring system derived from movements (limb and breathing), tone, AFI and CTG
  • Invasive
    • Amniocentesis
    • Chorionic villous sampling
    • Lecithin/sphingomyelin ratio (oestriol)

Intrapartum 

  • Noninvasive
    • Foetal heart rate monitoring (auscultation or CTG)
    • Examination of liquor for meconium
  • Invasive
    • Foetal scalp electrode for CTG
    • Foetal scalp pH (sensitive for stress)
    • Vibroacoustic stimulation

Trauma in pregnancy 

  • Primary survey
    • A
      •  Difficult airway, increased risk of aspiration
    • B
      • Increased VO2, decreased PCO2, risk of hypoxia, fetal consideration
    • C
      • Resting tachycardia, expanded blood volume, altered resting BP, vasodilated
      • Potential for aortocaval compression
      • Blood loss related to pregnancy
        • Abruption
      • Abdominal assessment difficult, e.g. retroperitoneal haemorrhage
      • Pelvic fracture causes greater bleeding with enlarged vessels
      • Coagulation altered, physiological anaemia, thrombocytopenia
  • Tests
    • Bloods: increased WCC, decreased Hb, platelets, decreased PCO2
    • ECG: LAD
    • Abdo: Altered US assessment, risk with DPL
    • Imaging: consider radiation dose
    • Additional assessment of foetus: cardiotocograph (CTG), consultation with obstetrician
  • Obstetric management
    • Resuscitation of mother is first priority
      • Suitable hospital for trauma
    • Management of foetus determined by mother’s stability, fetal/placental well-being, uterine damage
    • Options
      • Expectant, delivery, Caesarean
    • Monitoring and frequent reassessment is important
  • Presentations
    • Arrest
      • ABC resuscitation, left lateral tilt, CPR may be ineffective
      • Caesarean if failed resuscitation at 4 min
        • Even if foetus is non-viable, improves CPR effectiveness
    • Major uterine injury
      • Rupture: pain, hypovolaemia, foetal distress or death, vaginal or IDC bleeding
      • Emergency laparotomy
    • Minor trauma, mother and baby apparently okay
      • Increased risk of premature labour, foetal distress
      • Monitoring with CTG, expectant management
      • If minor abruption
        • Risk of DIC: monitor fibrinogen, possible amniotic fluid embolism 
        • Fetomaternal haemorrhage: Kleihauer, anti-D if indicated
  • Doses
    • PGF: 5 mg (1 amp) in 20 ml, 1-2 ml up to 20 ml in myometrium
    • Mg2+ : 4 g bolus (30 min) 1-2 g/h 6 hourly levels
    • Ergometrine: 250 µg IV, 250 µg IM

Case scenarios

1. Inadequate perineal cover from epidural

  • LA bolus 5 ml 0.25% bupivacaine
  • ± pethidine 25-50 mg
  • ± clonidine 30-50 µg
  • Still failed: lidocaine 2% or bupivacaine 0.5% to block motor and sensory
  • Caudal an option in theory (risk of toxicity and foetal injection)

2. Head at spines requests analgesia

  • Combined spinal-epidural: 0.5 ml 0.5% bupivacaine, 25 µg fentanyl intrathecal
    • Epidural infusion to start after approximately 30 min

3. LUSCS with L3-4 epidural in situ top-up 15 ml 2% lignocaine, 50 µg fentanyl, block at T8

  • Bolus 5 ml lidocaine
  • Still no block: resite epidural to approximately T12-L1

4. Inadequate perineal block with LUSCS open on table

  • Wait, bolus epidural, narcotic, N2O, clonidine, ketamine
  • Lidocaine 0.5% applied by surgeon to bladder, pelvis

5. Late decelerations, emergency GA LUSCS. RSI, can’t see cords

  • Ventilate?
    • Yes: introducer, bougie, Fastrach, FOB, wake-up --> regional
    • No: help!, airway position, BURP (backward upward rightward pressure)position, different blade (straight, McCoy), ventilation is a higher priority than intubation, two hands on mask, Guedel, LMA, COPA, Combitube, cricothyroid puncture
  • Cricothyroid puncture
    • 14G Jelco with syringe, aspirate air, attach 3 way tap, O2 tubing, Sanders
    • injector (50 psi initially), airway to improve exhalation
  • Cricothyroidotomy

6. Post delivery, 14 hour labour, PPH 600 ml, BP 70 mmHg, HR 110 bpm, no IV access

  • Acute resuscitation: ABC
  • Supplemental O2, large bore IV access, rapid fluid replacement
  • Blood specimen for crossmatch, FBE
  • Obstetric management of haemorrhage
    • Remove placenta, rub fundus, oxytocin, ergometrine, PGF, aortic compression, theatre
  • Anaesthesia in theatre
    • RSI with reduced doses, reduced volatile (uterine relaxant)
    • Rapid IV infusion: Level 1 or warmer with pump set
    • Scale up monitoring when time available: arterial line, CVC
    • Early access to blood products: packed cells, platelets, FFP likely to be needed

7. 39 weeks, BP 155/95 mmHg, protein +, oedema, 95 kg, req. analgesia in labour at 4 cm

  • FBE, clotting, U&E, LFT, G&H, uric a., IDC (UO), CTG
  • Mg2+ bolus 4 g over 30 min, 1-2 g/h, 6 hourly levels
  • Add hydralazine if still hypertensive after an hour 5 mg bolus, infusion
    • Aim 120-140/70-90 mmHg
  • If platelet count = 80 × 109/L and clotting normal, epidural preferred with patient discussion of risks


Kindly provided by Dr James Mitchell from his pharmacodynamics series


ArticleDate:20060901
SiteSection: Article
 
   
    
                                            
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