Physiology Flashcards
MAC during pregnancy
decreases by 40%, returns to normal by 3-4 day postpartum
Sensitivity to local anesthesitcs?
Increased sensitivity to local anesthetics during pregnancy (30%)
epidural blood volume?
Obstructing IVC –> enlarges epidural venous plexus –> increases epidural blood volume –> more uptake of epidural anesthetics
CSF volume?
lower CSF due to increased girth in abdomen –> pushes CSF cephalad as well as epidural fluid –> more spread with injection
Oxygen consumption?
increased oxygen consumption in pregnancy –> 20% of CO goes to uterus and fetus that are very metabolically active
Minute ventilation
Large increase in minute ventilation –> respiratory alkalosis during pregnancy
Respiratory mechanics during pregnancy
Elevated diaphragm, increased AP chest diameter, Vt and RR increased
Rapid desaturation?
Decreased FRC + increased O2 consumption
Inhalational induction during pregnancy?
Accelerated due to increased MV and lower MAC
Airway during pregnancy
Treat all as difficult and full stomach!
- rapid desaturation
- edema from fluid retention
- friable tissue due to capillary engorgement
- full-stomach (RSI)
Hgb-O2 dissociation curve
- Alkalosis shifts to left
- 2,3-DPG shifts back right
Anemia during pregnancy?
dilutional anemia due to increased plasma circulating volume (55%)
- reduced blood viscosity as well
Estimated blood volume
in pregnancy it increased 90 cc/kg
DO2 during pregnancy?
reduction in Hgb is offset by the increase in CO
BP in pregnancy?
reduced SVR so normotensive
increased CO?
due to HR and SV increases
- greatest increase is immediately after delivery (autotransfusion)
- CO should return to normal in 2 weeks postpartum
Aortocaval compression?
supine hypotension syndrome
- can also see bradycardia
- enlarged uterus compresses IVC and aorta –> SOB and edema
Heart changes due to increased blood volume
- Stretching of ventricles –> common regurgitant lesions
- S3 heart sound
- accentuated S2 heart sound
- systolic ejection murmur
- slight cardiomegaly
GFR in pregnancy?
GFR increases thus making BUN and Cr lower!
- a Cr of 1 is abnormal in pregnancy!
Full stomach precautions?
cephalad displacement of stomach due to uterus = promotes LES incompetence
- progesterone contributes!
Hepatic changes
liver flow unchanged, slight elevation in ALK
- decreased pseudocholinesterase
Coagulation state
pregnancy is HYPERcoagulable state
Increased coagulant factors
- Factors VII, VIII, IX, X, XII
- Fibrinogen
Decreased coagulant factors
- Factor XI
- Platelets
Metabolic state
- diabetogenic state = high FFA, ketones, TGA
- hPL creates insulin resistance
CO immediately postpartum
Drastic increases in CO immediately postpartum –> venous constriction due to sympathetic surge and contraction of the uterus (venous reservoir)
when does aortocaval compression start?
around 20th week gestation
Difficult airway in pregnancy?
10x more common to have a failed intubation - can have changes in mallampati class during course
ACid base during pregnancy
Increased RR –> resp alkalosis
- renal compensation by HCO3 excretion
Succinylcholine metabolism
plasma cholinesterase activity decreased by 25% –> back to normal 2-6 week postpartum
not clinically relevant
Gastric emptying during pregnancy
gastric emptying doesn’t change –> but decreases during active labor
