In a pregnant lady there is decreased requirement of anaesthetic agents because of all the following, EXCEPT:
During pregnancy there is a reduction in the requirement of anaesthetic agent. Factors contributing to this are -increased levels of B-EP -increased neuronal sensitivity -vascular congestion in spinal canal and -increased levels of progesterone. Increased lumbar lordosis has not been mentioned any where as a contributing factor for decreasing requirement of anaesthetic agents in pregnancy. During pregnancy enlarged uterus obstructs the inferior venacava and distends epidural venous plexus and increases epidural blood volume. This inturn results in decreased spinal CSF volume, decreased potential volume of subarachnoid space and increased epidural space pressure. The first two effects enhance the spread of LA solutions during spinal and epidural anaesthesia respectively whereas last may predispose to higher incidence of dural puncture with epidural anaesthesia. Ref: Maternal, Fetal, & Neonatal Physiology: A Clinical Perspective By Susan Tucke page 548.
Higher sensitivity of nerves to anaesthetics
Increased lumbar lordosis
Engorged spinal veins
Decreased sub arachnoid space