SPREAD OF SPINAL ANAESTHESIA FOR CAESAREAN SECTION IN SINGLETON AND TWIN PREGNANCIES

We have compared the spread of spinal anaesthesia in parturientswith singleton and those with twin pregnancies. Fifty-five unpremedicatedpatients with uncomplicated pregnancy scheduled for Caesareansection were allocated to two groups: group I = 35 singletonmothers; group II = 20 with twin pregnancy. Both groups receivedspinal anaesthesia with hyper baric bupivacaine 10 mg (2 mlof 0.5%). Mean birthweight was 3290 (SD 452) g and 5008 (495)g in groups I and II (combined birth weights), respectively.We found a statistically significant difference in onset andmaximal cephal-ad spread of spinal anaesthesia (group I median15, range 18–14; group II 13, range 16–12). Themechanisms of higher cephalad spread of spinal anaesthesia inparturients may be a decrease in cerebrospinal fluid volumesecondary to shunting of blood from the obstructed inferiorvena cava to the extradural venous plexus and increased nervesensitivity to local anaesthetics because of increased concentrationsof progesterone. The twin pregnancy group had heavier, largeruteri and greater daily production of progesterone. (Br. J.Anaesth. 1993; 70: 639–641)