Direction of injection does not affect the spread of spinal bupivacaine in parturients

One of the factors that can affect the distribution of local anaesthetic solutions in the subarachnoid space is the direction of the spinal needle through which injections are made. This study investigated the effect of the direction of the aperture of the Whitacre needle on the spread of hyperbaric bupivacaine in parturients undergoing elective caesarean section.

Forty healthy term parturients scheduled for caesarean delivery under spinal anaesthesia with 12 mg hyperbaric bupivacaine + 0.2 mg morphine were randomly assigned to one of two groups: needle orifice cephalad (I) or caudad (II). Spinal blocks were administered in the sitting position with patients being positioned supine immediately after. A blinded observer assessed the dermatome level of analgesia to ice every minute for the first 10 minutes, every three minutes for the following 35 min, then every 15 min until the sensory level regressed to T10.

There was no difference between the groups regarding the maximal number of segments blocked cephalad to T11 (11.4 +/- 3.4: group I and 12.0 +/- 3.4: group II), time to highest cephalad spread of sensory block (22 +/- 10: group I and 19 +/- 10 min: group II), or time to regression to T10 (164 +/- 26: group I and 153 +/- 24 min: group II). The maximum decrease in blood pressure (33.9 +/- 9.6: group I and 36.8 +/- 11.8 mmHg: group II) and dosage of ephedrine administered (14.7 +/- 10.7: group I and 16.2 +/- 11.0 mg: group II) did not differ.

The direction of the aperture of the Whitacre needle does not influence the spread of hyperbaric bupivacaine in the term parturient.