Back pain and collapse associated with receding subarachnoid blockade

Back pain and sudden loss of consciousness during recovery from spinal anesthesia are rare. Severe pain may raise fears of serious neurological damage and result in inappropriate management. Bladder distention may present in this way and clinicians should be alert to this possibility and communicate this to nursing staff.

A lumbar spinal anesthetic was performed during a volunteer study, using 15 mg hyperbaric bupivacaine in a healthy 31 yr old man. During recovery, five hours later, as the block regressed to the L1-2 level, he complained of acute, severe back pain and briefly lost consciousness secondary to profound bradycardia. Bladder cathetherization yielded 900 mL urine with immediate and complete relief of symptoms.

Severe pain secondary to bladder overdistention in the presence of neuroaxial blockade may be referred to the thoracolumbar area, mediated by intact sympathetic afferents. As the saccral parasympathetic supply remains paralyzed, there is no subjective sensation of bladder stretching. If untreated, bladder distention can lead to excessive supraspinal parasympathetic outflow resulting in vasovagal syncope.