Physiology in Anaesthesia: Part 3 Flashcards
Aetiological factors in the development of retinopathy of prematurity
- prematurity
- hyperoxia
- hypocarbia
- vitamin E deficiency
- acidaemia
Preferred trimester for non-obstetric surgery in obstetric patients
second
What factors cause the increased in maternal intravascular fluid volume
- increased production of renin, angiotensin, and aldosterone
- promotion of sodium absorption and water retention
- progesterone circulation
Haematological changes in maternity
- increased intravascular fluid volume
- relative reduction in plasma protein concentration
- physiologic anaemia due to greater increase in plasma than RBC
- mild thrombocytopaenia
- mild leukocytosis
- increased fibrinogen and factor 7
- decreased factors 6, 8, and antithrombin 3
- decreased PT and PTT (20%)
What accounts for the large increase in cardiac output immediately after delivery
- autotransfusion after delivery
- reduced vascular capacitance from loss of placenta
- decreased lower extremity venous pressure from release of aortocaval compression
Do the following increase, decrease, or stay the same in pregnancy:
1. systemic blood pressure
2. central venous pressure
3. pulmonary capillary wedge pressure
4. venous capacitance
- decrease
- stay the same
- stay the same
- increase
Signs of aortocaval compression
nausea, vomiting
diaphoresis
dizziness
Cardiac auscultation in pregnancy
S1: accentuated, increased splitting
S3: common
S4: minority
EJS: 2/6
Acid-base changes in pregnancy
- PaCO2 reduced to 30mmHg
- Mild increase in arterial pH
- HCO3 reduced to 20-21 (increased renal excretion)
Lung volume changes in pregnancy
- FRC reduced 20%
- Equal reductions in RV and ERV
- Closing capacity unchanged
- Vital capacity not significantly changed
Reasons for increased risk of aspiration in pregnancy
- upward movement of oesophageal sphincter
- reduced oesophageal sphincter tone
- gastrin secreted by placenta stimulates gastric acid secretion
- gastric emptying unchanged unless in labour
- increased residual gastric volume
Why do pregnant women require smaller volumes of local anaesthetic for neuraxial blockade
- decreased size of epidural space
- decreased volume of CSF in subarachnoid space
- engorgement of epidural veins
- hormonal changes
Causes of decreased uterine perfusion pressure
- maternal hypotension
- hypovolaemia
- aortocaval compression
- anaesthesia
- increased uterine pressure
- hypocapnoea
- valsalva
- endogenous catecholamines, exogenous vasopressors
Why is foetal haemoglobin left shifted
HbF does not interact with 2,3-DPG
GA at which FHR monitoring is acceptable
25 weeks