Anaesthetics & the pregnant woman Flashcards Preview

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Flashcards in Anaesthetics & the pregnant woman Deck (25)
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1
Q

Cardiovascular system changes by 32 wks in pregnancy

A

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.

2
Q

Aortocaval compression

  • what is it
  • compensation
  • in context of epidural?
A
  • 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
3
Q

Respiratory system changes by 35 wks in pregnancy

A

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

4
Q

Haematological system by 35 wks in pregnancy

A

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

5
Q

Gastrointestinal system by 35wks in pregnancy

A

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

6
Q

Plasma proteins by 35wks in pregnancy

A

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

7
Q

Urinary tract changes by 16 wks in pregnancy

A

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

8
Q

Central nervous system by 16 wks in pregnancy

A

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

9
Q

Effects of post delivery in the

  • short term
  • longer term
A
  • loss placental shunt + auto-transfusion with uterine contraction = cardiovascular events
  • reversal of changes over next 5 days = thrombo-embolism
10
Q

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

A
  • risk of hypoxia (O2 consumption up 20%, FRC down, CC>FRC
  • risk of failed intubation
  • acid aspiration
  • thromboembolism
11
Q

Effect of pain in labour on

  • resp system
  • cardio system
A
  • 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)
12
Q

Explain pain transmission in labour

  • visceral
  • somatic
A
  • 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
13
Q

Pain in labour

  • stage 1
  • stage 2
A
  • 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
14
Q

Labour pain relief - non pharmacological

A
  • prepared (antenatal calsses)
  • hypnosis
  • acupuncture (infection, bleeding risks)
  • TENS (high frequency low intensity current)
15
Q

Labour pain relief -pharmacological

A
  • 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)
16
Q

Regional Analgesia types

A

Epidural
Spinal
Combined spinal epidural

17
Q

Epidural - anatomy

A

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)

18
Q

Spinal - anatomy

A

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

19
Q

Epidural indications

A
  • pain relief
  • medical indications (conditions e.g. cardiac disease; obsterical e.g. pre-eclampsia)
  • reduce delivery trauma
20
Q

Epidural contraindications

A
  • patient refusal
  • hypovolaemia
  • coagulopathy/anticoagulant treatment
  • sepsis (localised v gen)
  • active neurological (relative)
  • obstetrical (fetal distress…relative)
21
Q

Epidural advantages

A
  • effective pain relief
  • no sedation
  • improves placental blood flow (pre-eclampsia)
  • allows instrumental delivery (LUSCS)
22
Q

Epidrual complications

A
  • immediate (hypotension, dural puncture, high block, total spinal, intravascular injection)
  • delayed (PostDuralPunctureHeadache, backache, neurological, infective complications, haematoma)
23
Q

Epidural drugs

A

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

24
Q

C section GA risks

A

(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)
25
Q

C section RA

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