Factors affecting the spread of bupivacaine in the adult thoracic paravertebral space

Abstract

SummaryFactors affecting the spread of bupivacaine in the paravertebral space were investigated in patients undergoing paravertebral nerve blocks for the treatment of chronically painful conditions. Injections of bupivacaine 0.5%, 10-15 ml mixed with depomedrone up to 80 mg were repeated at 2-wk intervals up to a maximum of four times. A blinded observer mapped out the subsequent distribution of sensory loss to cold on both sides of the torso at 5-min intervals after each injection. Age, sex, height and weight did not correlate with the block; nor did injectate volume, mass of bupivacaine, previous posterolateral thoractomy and spread of radiocontrast. Injections repeated at 2-wk intervals in the same patient resulted in different degrees of spread that were unrelated to one another. Time to peak onset of blockade was 40 min in 95% of patients. A single bolus of bupivacaine produces a safe but unpredictable block. Yet to be defined physical properties and anatomical factors are probably key determinants of the spread of bupivacaine in the paravertebral space. This single bolus technique may be better supplanted by a reversion to the older multiple level injection technique.Keywords Local anaesthetic. Bupivacaine: nerve block, intercostal nerve. Two aspects of paravertebral nerve blocks that have been poorly investigated are the predictability of spread of local anaesthetic and the reliability of production of the block. To identify any involved factors, we undertook this prospective, single-blinded, longitudinal, observational study of patients undergoing therapeutic paravertebral blocks as a part of their chronic pain management. MethodsThe study was approved by the local ethics committee and written informed consent was obtained from all patients.Patients listed for therapeutic paravertebral injections as a component of management of chronically painful conditions of the chest and abdomen were included in the study. Those with a pre-existing sensory deficit were excluded. A single injection technique was used, as described elsewhere [1]. All blocks were performed to the satisfaction of the same experienced operator (J.R.). Correct Tuohy needle placement alongside the vertebral column superior to the transverse process in each patient was confirmed through the injection of 3 ml of radioopaque dye (Isovist, Schering, Germany). All material was injected with the Tuohy needle opening pointing cranially and contrast medium was tracked with an image intensifier, its shape being categorised as globular or as a cranio-caudal streak. Bupivacaine 0.5%, 10-15 ml mixed with depomedrone up to 80 mg was injected over 60 s.In the recovery room, a blinded observer mapped out the subsequent distribution of sensory loss to cold on both sides of the torso at 5-min intervals until a stable block had been established, i.e. two 5-min observations were the 684Ó 2003 Blackwell Publishing Ltd same. The cold stimulus used was a mixture of ice in tap water contained in a copper test tube. Each patient also had non-invasive measurements...

The location of paravertebral catheters placed using the landmark technique

“…Similar findings have been reported for single-injection paravertebral blocks [15] and for imaging studies in infants receiving caudal blocks [18,19]. The probable explanation for this is the time delay between the injection of the contrast dye and the subsequent local anaesthetic bolus injection and continuous infusion.…”

“…It is well documented that with a multi-level single injection paravertebral technique, unilateral anaesthesia of the thorax can be achieved with a high success rate, irrespective whether a landmark-based technique [4,5,14,15] or an ultrasound-guided approach [8] has been chosen. There is, however, some controversy surrounding the use of catheters for continuous paravertebral block because of limited cranio-caudal spread of local anaesthetic [16] as well as the possible discrepancy between the needle tip position and the final catheter tip location [12].…”

The ultrasound-guided retrolaminar block

“…These studies will most likely rely on direct anatomic investigation, as clinical studies that rely on dermatomal mapping after paravertebral blockade are unable to distinguish among local anesthesia in the paravertebral, intercostal, or epidural spaces. 1,2,24,25 Since it is likely that the analgesic effects of the paravertebral block are due to some combination of paravertebral, intercostal, or epidural spread, and even systemic local anesthetic effects, it would be interesting and important to know if different block techniques result in different injectate distribution. In these cases of multiple rib fractures presented here, another factor could also play an important role in the local anesthetic spread, i.e., the traumatic injury and possibly uneven disruption of ribs, ligaments, and fascias, possibly facilitating access of the local anesthetic to the true paravertebral space.…”

Varying anatomical injection points within the thoracic paravertebral space: effect on spread of solution and nerve blockade

“…Cheema et al have recently described the unpredictable dermatomal spread of a single paravertebral blockade (PVB) injection [1] and in a previous review of PVB, Karmakar speculated whether the spreading pattern of this nerve block is influenced by a thin connective tissue structure that exists within the thoracic paravertebral space (TPVS), the so-called endothoracic fascia [2]. It is not possible with standard PVB techniques to determine on which side of this fibrous structure the tip of the needle is located.…”