Assessing the height of block for caesarean section over the past three decades: trends from the literature

Abstract

SummaryThere are multiple methods of assessing the height of block before caesarean section under regional anaesthesia, and surveys of practice suggest considerable variation in practice. So far, little emphasis has been placed on the guidance to be gained from published research literature or textbooks. We therefore set out to investigate the methods of block assessment documented in published articles and textbooks over the past 30 years. We performed two searches of PubMed for randomised clinical trials with caesarean section and either spinal anaesthesia or epidural anaesthesia as major Medical Subject Headings. A total of 284 papers, from 1984 to 2013, were analysed for methods of assessment of sensory and motor block, and the height of block deemed adequate for surgery. We also examined 45 editions of seven anaesthetic textbooks spanning 1950-2014 for recommended methods of assessment and height of block required for caesarean section. Analysis of published papers demonstrated a wide variation in techniques, though there has been a trend towards the increased use of touch, and an increased use of a block height of T5 over the study period. Only 115/284 (40.5%) papers described the method of assessing motor block, with most of those that did (102/115; 88.7%) describing it as the 'Bromage scale', although only five of these (4.9%) matched the original description by Bromage. The required height of block recommended by textbooks has risen over the last 30 years to T4, although only four textbooks made any recommendation about the preferred sensory modality. The variation in methods suggested by surveys of practice is reflected in variation in published trials, and there is little consensus or guidance in anaesthetic textbooks.

Complications in obstetric anaesthesia

“…Surveys of anaesthetists have shown a variation in modality of assessment and the height of the block aimed for – the loss of cold or light touch sensation is most commonly used. The most frequently quoted block height that anaesthetists aim for before caesarean section is bilateral loss of cold sensation below T4, and/or bilateral block to light touch to T5 . If this is not initially achieved, then more time may be needed for the block to spread.…”

Learning from the Law. A review of 21 years of litigation for pain during caesarean section

“…Over 95% of anaesthetists document the upper level of the block in the anaesthetic record with 63% also recording the lower level . Analysis of textbooks and published papers shows that the recommended upper level of block has risen with time, and that there is a trend towards using touch, rather than cold, as the testing modality .…”

Monitoring regional blockade

“…The degree of testing and the meticulousness of documentation probably depend not only on the practitioner but also on the type of surgery, the possibility that the effect of the block can be directly assessed and the context. Testing before caesarean section under spinal anaesthesia may well be more carefully performed and noted than, for instance, a transverse abdominis plane block performed after induction of general anaesthesia .…”