Detection of neurovascular structures using injection pressure in blockade of brachial plexus in rat

Abstract

In the last few decades there has been a great development of regional anesthesia; all the postulates are defined and all the techniques of usage are perfected. However, like any other medical procedure, the block of brachial plexus carries a risk of certain unwanted complications, like possible intraneural and intravascular injections. The reason for great discrepancy between the injury of brachial plexus and other periphery nerves while performing the nerve blockade is the frequent usage of this block, but also the specific proximity of neurovascular structures in axilla. The purpose of this work is to determine the values of pressures which appear in para-neural, intraneural and intravascular injection applications of local anesthetic, and to compare those values in order to avoid cases of intraneural and intravascular injections in clinical practice with consequential complications. In experimental study there have been used 12 Wistar rats of both genders. After anesthesia with ether and mid-humoral access to the neurovascular structures in axilla, the injection of 2% lidocaine with epinephrine was performed with the help of automatic syringe charge. The needle was at first placed para-neural, and then also intraneural and intravascular. During every application the pressure values were monitored using the manometer, and then they were analyzed by special software program. All para-neural injections resulted with the pressure between 13,96-27,92 kPa. The majority of intraneural injections were combined with the injection pressure greater than 69,8 kPa, while the intravascular injections were combined with injection pressure less than 6,98 kPa. Based on the available data it can be noticed that so far none of the methods of prevention from unwanted complications of regional anesthesia can insure the avoidance of intraneural and intravascular injection of local anesthetic. Based on our research it is obvious that the measuring of pressure during the nerve blockade is very important in order to decrease the risk of neurological and possible systematic complications. It is also clear that a small, mobile, and financially quite available apparatus for pressure measurement can help in differentiation between para-neural, intraneural and intravascular injection. Avoiding high injection pressure prevents from lodging the needle into intraneural space, while avoiding a very low injection pressure prevents from lodging the needle into intravascular space followed by consequential complications. The usage of this apparatus can find its application in other blockades of periphery nerves, and in other branches of medicine as well.

Pressure Monitoring of Intraneural an Perineural Injections Into the Median, Radial, and Ulnar Nerves; Lessons From a Cadaveric Study

“…For six out of ten ulnar nerves intraneural injections, the injection pressure was < 20 psi. The present investigation confirms previously identified positive correlations between increased injection pressures and intraneural placement ( 13 , 18 , 20 ). Orebaugh et al ( 17 ) conducted a study in which unembalmed cadaveric nerve roots were injected intraneurally at the C6 and C7 level and the pressure of injection as well as the spread of the injected materials was recorded.…”

An improvised pressure gauge for regional nerve blockade/anesthesia injections: an initial study

“…This correlates with animal models that demonstrate that high injection pressures are associated with nerve injuries [5,6]. Therefore, measuring the ''opening'' pressure before flow commences is expected to be vital.…”

“…High injection pressure is currently thought to be one of the more reliable warning signs of intraneural injection [2], with animal models suggesting high-risk pressures of between 69 kPa (small animal model [5]) to 176 kPa (large animal model [6]) as indicative.…”

A rat model of nerve stimulator-guided brachial plexus blockade

“…Vuckovic et al. 21 demonstrated that measuring the injection pressure was an effective method for evaluating the safety of BPB in the axilla of rats. This technique would be a good supplement for NS or US-guided BPB to improve injection safety.…”

“…Further studies should be performed to investigate the US-guided BPB model in rats and to compare US and NS guided-BPB in rats for the development of a safer and more convenient BPB method. Vuckovic et al 21 demonstrated that measuring the injection pressure was an effective method for evaluating the safety of BPB in the axilla of rats. This technique would be a good supplement for NS or US-guided BPB to improve injection safety.…”