Importance of the Perineural Spaces in Nerve Blocking

Abstract

Physicians who inject nerve blocking agents, either to produce local anesthesia or to alleviate pain, are aware of the possible complications associated with these procedures. However, few seem to be cognizant of the potential significance of the relationship of the perineural spaces to the subarachnoid space and the spinal cord as the determining factor in the development of some of the more serious complications. This relationship was bluntly called to our attention by recent experiences after the use of Efocaine (a solution of 1% procaine, 0.25% procaine hydrochloride, and 5% butyl-p-aminobenzoate in a solvent composed of 2% polyethylene glycol 300, 78% propylene glycol, and water). It was originally advertised as a safe, long-acting (two to four weeks' duration), local anesthetic mixture unassociated with encapsulation, abscesses, foreign body reactions, tissue sloughs, or other such adverse effects encountered after the use of oil solvents.1 Early published reports seemed to support the claim of its manufacturer that its prolonged action was effected by the precipitation of procaine crystals in the body tissues.-However, later pub¬ lished reports indicated that the long action was actually due to tissue damage, particularly to nervous tissue, from the propylene and polyethylene glycol that are the principal solvents in the Efocaine mixture. These pub¬ lications reported sloughs, cellulitis, transverse myelitis, and deaths.3In reviewing two deaths and 11 cases of transverse myelitis following the use of Efocaine, it was noted ;i0 that all of the patients received paravertebral injections of the peripheral somatic nerves except one, who re¬ ceived a lumbar sympathetic block. The maximum dis¬ tance of the injection site from the intervertebral foramen was 8 cm., by actual postmortem measurement. Four of these patients had percutaneous injections-in two the intercostal nerves were blocked, and in one the lum¬ bar sympathetic nerves were injected. In the remaining nine patients, the intercostal nerves were injected intraneurally under direct vision for the relief of postopera¬ tive pain prior to closure of thoracotomies. In most instances, the physician blamed himself for having in¬ advertently injected the anesthetic agent into the subarachnoid space through unusually long cuffs of dura. This is exemplified by the following statement from a recently published paper by Brittingham, Berlin, and Wolff *: "An almost unavoidable hazard of paravertebral nerve block is inadvertent injection of the agent used into the subarachnoid space. This probably occurs be¬ cause of an outward prolongation of the subarachnoid space or in other instances because of movement of the patient and tearing of the tissues after the needle is in place." In spite of this possibility, it is unlikely that durai cuffs extend 6 to 8 cm. past the intervertebral foramina; thus, direct injection into the subarachnoid space by this route is doubtful.5If long durai cuffs are not the route of entrance into the spinal subarachnoid space, what other rou...

Spread of Analgesic Solutions in the Epidural Space and Their Site of Action: A Statistical Study

“…(3) On mixed spinal nerves in the paravertebral spaces after they have left the intervertebral foramina (this latter suggestion being regarded as rather improbable in view of the available evidence). There is one remaining possibility which has been hinted at by several authors (Moore et al, 1954;Marx, Zemaitis and Orkin, 1961), but which has not until now been seriously advanced as an explanation for one of the main pathways and sites of action of epidural analgesia. This possibility appears to reconcile all the clinical and experimental evidence which is available at present.…”

Direct injection into the dorsal root ganglion: Technical, behavioral, and histological observations

“…While intrathecal injection is a simple and relatively noninvasive means to deliver agents to sensory neurons, it is not possible to restrict injected solution to a single side or to a limited longitudinal range of vertebral levels. Material injected into peripheral nerves may be conveyed to the DRGs (Moore et al, 1954), but this pathway may also result in nerve and spinal cord damage (Hogan, 2008), and would convey agents to multiple DRGs proximal to the injection site. Direct injection into the DRG has the benefits of specific targeting of sensory pathways on a segmental basis, and clinical methods for injecting drugs directly to selected DRGs are well established (Hogan, 1998; Pfirrmann et al, 2001).…”

Cervical Myelopathy Caused by Injections into the Neck

“…Moore and colleagues demonstrated central spread of Efocaine, colored with methylene blue, following intraneural injection into the lumbar and brachial plexus of a killed monkey. 1,2 The colored Efocaine reached the spinal cord in 2 to 5 minutes, initially spreading up and down the surface of the cord subpially. After 10 to 15 minutes, the spinal fluid became tinged, suggesting that the Efocaine had crossed the pia mater.…”

“…In the 1950s, Moore and colleagues 1,2 described cases of acute-onset clinical “transverse myelitis” following paravertebral blocks with Efocaine. These patients developed immediate, severe bilateral leg weakness with only minimal improvement after many months of observation.…”