British journal of anaesthesia
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Case Reports
Sudden onset of subarachnoid block after subdural catheterization: a case of arachnoid rupture?
We describe a patient who received an apparently uneventful extradural block in labour but developed rapid extension of neural block within minutes of receiving her first incremental dose 2 h later. Computed contrast tomography revealed radio-opaque dye within both the subdural and subarachnoid spaces, but none within the extradural space. This case report demonstrates that subdural spread of low-dose local anaesthetics is not always clinically distinguishable from extradural analgesia and that the arachnoid membrane may subsequently perforate with potentially serious consequences.
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The mechanism by which racemic (R(+/-)) ketamine relaxes airway smooth muscle is unclear and there is no information on the differential effects of ketamine and its isomers. In this study, we have examined the spasmolytic effect of R(+/-) ketamine and its isomers S(+) and R(-) ketamine and the role of intracellular calcium and opioid receptors in R(+/-) ketamine-induced relaxation. The tension of isolated guinea pig tracheal strips was measured isometrically with a force displacement transducer and contraction elicited with histamine 10(-5) mol litre-1. ⋯ We conclude that although both ketamine isomers produced equipotent spasmolytic effects on airway smooth muscle precontracted with histamine, they differed in their ability to potentiate the relaxing effect of adrenaline. S(+) ketamine produced the greatest potentiation. Changes in intracellular Ca2+ level secondary to a reduction in the L-type Ca2+ current may partially mediate the spasmolytic effect of R(+/-) ketamine.