Dear Editor,
This is with reference to the article “Midazolam, a new more potent benzodiazepine, compared with diazepam as sedative during spinal analgesia” [1]. While I am in agreement with the results of the study, but I wish to highlight a few aspects related to sedation during spinal anaesthesia, lest wrong signals may be passed to the less experienced.
The authors have used 0.5% plain (isobaric) bupivacaine and thus managed to maintain a predictable lower level of blockade till T10. The more commonly used solution of bupivacaine for spinal anaesthesia is 0.5% hyperbaric solution and it is known to cause higher spread compared to isobaric solution [2, 3, 4]. Moreover there is always unpredictability about the level of spread as it is dependent on many factors like dose, volume and basicity of the drug position of patient during and after injection, interspace used etc. Hence sedation during higher level of spinal block may be hazardous due to combined effects of high block and sedation. In a retrospective study of 14 cases of unexplained cardiac arrest during spinal anaesthesia, Caplan et al [5] revealed that all of them had received intraoperative sedation. It has also been proved that patients having high spinal anaesthetic are more sensitive to sedative effect of Midazolam [6]. Midazolam has a depressant effect on respiratory responses to hypercarbia and hypoxia [7, 8]. This effect may be more obvious or aggravated in compromised patients.
In view of the above following suggestions are made:-
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(a)
Sedation during spinal anaesthesia should not be generalised. A carefully selected and motivated patient feels more comfortable and reassured without sedation (personal experience).
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(b)
Occasional deep breath on command in an awake patient compensates for the decrease in oxygen saturation, This also acts as an additional safeguard.
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(c)
Patients with cardio-respiratory problems will need closer supervision intraoperatively. Oxygen inhalation by nasal prongs via oxygen concentrator would be ideal.
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(d)
The unpredictability about height of block and its consequences should be kept in mind intraoperatively. The sedation if required should be restricted to infraumbilical blocks.
References
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