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Flashcards in Anaesthetics & the pregnant woman Deck (25):

Cardiovascular system changes by 32 wks in pregnancy

CO up 40%, HR up 15%, SV up 35%, peripheral resistance down 35%, Heart displaced up & left, louder heart sounds with flow murmur, ECG inverted T in II, V1, V2. L axis deviation, some ST depression.


Aortocaval compression
- what is it
- compensation
- in context of epidural?

- aorta and IVC compressed by gravid uterus when woman lies prone
- tachycardia, vasoconstriction, diversion of blood through epidural & azygous system
- (decompensation) bradycardia, nausea, sweating, pallor, faining


Respiratory system changes by 35 wks in pregnancy

Tidal volume up 40%, RR up 15%, airways resistance down 35%, alveolar ventilation up 70%, FRC down 20%, some women CC>FRC, Diaphragm up 4cm, capillary & soft tissue engorgement upper airway


Haematological system by 35 wks in pregnancy

Total blood volume up 40%, plasma volume up 50%, RBC volume up 30%, Hb down to 120, Hct down 35%, platelets down 20%, clotting factors up 800%, plasminogen & anti-thrombin III down


Gastrointestinal system by 35wks in pregnancy

GIT tone and motility down, gastric emptying delayed, acid production up, LOS pressure down, reflux present in > 80%


Plasma proteins by 35wks in pregnancy

Total amount up, concentration of protein, albumin, globulin down, plasma oncotic pressure down 15%, plasma pseudocholinesterase levels down 28% before delivery, 35% for 3 days after


Urinary tract changes by 16 wks in pregnancy

Dilation of ureters and renal pelvices, RBF up 75%, GFR up 50%, renal threshold for glucose down, aldosterone up


Central nervous system by 16 wks in pregnancy

Sensitivity up to narcotics, local anaesthetics, GA gases; endorphins up


Effects of post delivery in the
-short term
- longer term

- loss placental shunt + auto-transfusion with uterine contraction = cardiovascular events
- reversal of changes over next 5 days = thrombo-embolism


Clinical implications of pregnancy on anaesthetics (systems are at end of reserve)

- risk of hypoxia (O2 consumption up 20%, FRC down, CC>FRC
- risk of failed intubation
- acid aspiration


Effect of pain in labour on
- resp system
-cardio system

- hyperventilation due to hypocarbia and alkalaemia (hypoventilate between contraction = maternal & fetal hypoxaemia and acidosis = uteroplacental & fetoplacental vasoconstriction = left shift of oxygen dissociation curve compromises O2 delivery to fetus); increased O2 consumption
- cardiovascular (increase stroke volume, heart rate = increase cardiac output)


Explain pain transmission in labour
- visceral
- somatic

- VISCERAL (paracervical region, through pelvis [inf, mid, sup hypogastric plexuses], lumbar sympathetics, T10-L1 synapses with interneurons in dorsal horn)
- SOMATIC (pudendal nerve (S2,3,4)+ilioinguinal+gentiofemoral+post.femoral cutaneous nerve


Pain in labour
- stage 1
- stage 2

- FIRST STAGE (dilatation of cervix, lower uterine segment contraction, T10-L1/2, referred to abdomen lower back upper thigh)
- SECOND STAGE (distension of outlet, vagina, vulva, perineum, S2-4 well localised


Labour pain relief - non pharmacological

- prepared (antenatal calsses)
- hypnosis
- acupuncture (infection, bleeding risks)
- TENS (high frequency low intensity current)


Labour pain relief -pharmacological

- nitrous oxide (rapid potent analgesic gas, ENTONOX, takes 50s, use before contraction starts)
- OPIOIDS (pethidine = most common, cheap, safe, easy, IM, but maternal N&V + dysphoria AND fetal effects)
(Fentanyl = shorter acting, highly lipophilic, IV, PCA)(Remifentanil = ultra short acting, narrow safety margin, PCA)


Regional Analgesia types

Combined spinal epidural


Epidural - anatomy

between dura and spinal canal, from foramen magnum to sacral hiatus; contains fat, lymphatics, blood vessels and nerve roots; spinal cord ends at L1/2)


Spinal - anatomy

old technique, safe, reliable and simple with rapid analgesia onset BUT not titratable


Epidural indications

-pain relief
-medical indications (conditions e.g. cardiac disease; obsterical e.g. pre-eclampsia)
- reduce delivery trauma


Epidural contraindications

- patient refusal
- hypovolaemia
- coagulopathy/anticoagulant treatment
- sepsis (localised v gen)
- active neurological (relative)
- obstetrical (fetal distress...relative)


Epidural advantages

- effective pain relief
- no sedation
- improves placental blood flow (pre-eclampsia)
- allows instrumental delivery (LUSCS)


Epidrual complications

- immediate (hypotension, dural puncture, high block, total spinal, intravascular injection)
- delayed (PostDuralPunctureHeadache, backache, neurological, infective complications, haematoma)


Epidural drugs

Bupivacaine or Ropivaciane (low dose LA + opioid e.g. fentanyl)


C section GA risks

(obstetric airway harder, weight gian, fluid retention, laryngeal oedema e.g. PET, breast enlargement)
- hypoxia (less O2 store, increased O2 use so more rapid desaturation if apnoeic
- full stomach (delayed gastic empty, aspiration risk)


C section RA

- can bond (GA drugs depressant)
- nil intubation
- block T4-S4
- spinal vs. epidural