Long-Tapered Double Needle Used to Reduce Needle Stick Nerve Injury

Background and ObjectivesNeedle trauma may cause peripheral nerve injuries during performance of peripheral nerve block.MethodsFour types of 21-gauge needles for regional anesthesia were compared: a beveled nerve block needle (Quincke type); a short-tapered needle with a side orifice (Whitacre type); a long-tapered needle with a side orifice (Sprotte type); and a long-tapered double needle combining an inner pencil-point fine needle with an outer truncated conical needle (a new type). This new needle was developed to reduce the potential for nerve injury while retaining a suitable flow rate of anesthetic solution and the ability to inject the solution precisely at the point of paresthesia elicited by the tip. Each type of needle was used to produce puncture injuries to rabbit sciatic nerves. Eighteen specimens were studied within each needle group. The beveled needle was used to produce two different types of nerve injuries by inserting it either transverse or longitudinal to the nerve fibers. Each histologic specimen of the nerve with the needle puncture was surfacestained with hematoxylin-eosin and Bodian's method. Subsequently, the number of damaged axons was histomorphologically counted and statistically evaluated.ResultsBoth long-tapered needles produced significantly fewer transected axons than the beveled needle inserted with the bevel longitudinal to the nerve fibers.ConclusionThe long-tapered needles produced the least number of transected nerve fibers after sciatic nerve puncture.

Comparison of Clonidine and Epinephrine in Lidocaine for Cervical Plexus Block

Background and ObjectivesCarotid endarterectomy under cervical plexus block offers the advantage of awake neurologic assessment. The hypothesis was tested that the addition of clonidine 5 μg/mL to lidocaine 1.5% for the block is as effective clinically as the addition of epinephrine 5 μg/mL but without the associated tachycardia.MethodsIn a double-blind, randomized, prospective trial of 40 patients, local anesthetic solutions of lidocaine 1.5% containing either clonidine 5 μg/mL or epinephrine 5 μg/mL were compared for cervical plexus block in patients undergoing carotid endarterectomy. Each solution was administered to 20 patients with a total lidocaine dose of 7 mg/kg. The electrocardiogram, heart rate, and arterial pressure (radial artery catheter) were continuously monitored. Blood samples were drawn for determination of serum lidocaine levels during the first hour.ResultsThe block onset time (8.4 ± 0.6 minutes for epinephrine, 8.8 ± 0.8 minutes for clonidine) and duration (139 ± 6.7 minutes for epinephrine, 148 ± 5.8 minutes for clonidine) were not different between the two groups. During the period from completion of the block until incision there was a significant heart rate increase in the epinephrine group (23% mean rise) as compared with the clonidine group (4% mean rise) (P < .003). There was no difference in blood pressure between the two groups. The maximum plasma concentrations of lidocaine were 2.5-7.6 μg/mL (mean, 4.5 ± 0.3 μg/mL) for the epinephrine group and 4.7-18.4 μg/mL (mean, 7.5 ± 0.7 μg/mL) for the clonidine group (P < .0002). The maximum concentrations were reached 0-30 minutes (mean, 8 ± 1.4 minutes) after injection for the epinephrine group and 0-10 minutes (mean, 4.5 ± 7.1 minutes) for the clonidine group (P < .03).ConclusionsClonidine 5 μg/mL is a useful additive to lidocaine 1.5% for cervical plexus block to reduce the incidence of tachycardia; however, omission of epinephrine results in higher serum lidocaine levels.

Epidural Space as a Starling Resistor and Elevation of Inflow Resistance in a Diseased Epidural Space

Background and ObjectivesThe origin and the presence of negative pressure in the epidural space as well as the relationship of the extent of epidural anesthesia to epidural pressure has long been a subject of controversy. To further elucidate epidural pressure and its time course, the pressure at the needle tip was continuously measured as it traversed the interspinous ligament and the ligamentum flavum.MethodsIn a group of 22 patients, fluid was infused under gravity, and in a second group of 25 patients, boluses of fluid were administered at controlled infusion rates and under gravity. The volume-pressure-flow relationship was thus measured in one of two ways, either with a manual syringe and pressure transducer or with a pressure-monitoring-computer-controlled volumetric infusion pump.ResultsNatural pressure, (i.e., pressure in the epidural space before instrumentation is applied) could be approached when the space was first entered before fluid was infused (initial pressure); or after fluid had been infused (residual pressure). Epidural pressure could be extrapolated from the upsweep of the volume-pressure-flow relationship by projecting it back to just before the first injection. The extrapolated pressure lay between the initial and residual pressures. Medicinal solution placed in the barrel of the syringe did not infuse under gravity until the syringe barrel was lifted to a certain height, at which flow began and continued at a perceptible rate, with very little or no further increase in height required to maintain flow. The pressure at which flow began was the critical opening pressure, a characteristic of a Starling resistor. Furthermore, resistance to inflow of fluid was related to the presence or absence of natural or surgical disease in the epidural space. Resistance was significantly higher in the diseased than in the surgical group, at 114 (range, 22-226) mm Hg/L/h versus 46 (range, 8-86) mm Hg/L/h. Three phases were seen in the pressure-time recordings.ConclusionsVolume-pressure-flow relationships in the epidural space can be explained by a model in which epidural and subarachnoid pressures are inextricably related with the Starling pressure, dependent on the subarachnoid pressure. This model suggests reasons why spread of anesthetics might be difficult to predict.

Interpleural Analgesia in the Management of Esophageal Perforation

Background and ObjectivesInterpleural analgesia was used in a case of esophageal perforation due to surgical mishap. The medical literature cites no reference to use of this technique in this condition.MethodInterpleural bupivacaine analgesia was used along with conventional forms of pain relief.ResultsSuperior analgesia was obtained, and the method proved to be safe and complication free on a general surgical ward over the period of several days that it was used.ConclusionInterpleural analgesia is safe and effective for management of pain due to esophageal perforation.

Detection of Intravascular Epidural Catheters Using 2-Chloroprocaine: Influence of Local Anesthetic Dose and Nalbuphine Premedication

Background and ObjectivesDetecting the intravascular placement of epidural catheters is essential to avoid local anesthetic toxicity. Small doses of intravenous local anesthetics produce changes in sensorium and are often used to test newly placed epidural catheters. Many parturients receive nalbuphine for analgesia prior to epidural catheter placement. This study examines how nalbuphine premedication influences symptoms following intravenous 2-chloroprocaine.MethodsThirty-one volunteers were randomized to receive premedication with placebo or 0.15 mg/kg of nalbuphine intravenously. Starting 10 minutes later, intravenous injections of 0.0, 0.3, 0.6, 0.9, 1.2, and 1.5 mg/kg of 2-chloroprocaine were given in random order at 10 minute intervals. After each injection, volunteers were asked to report changes in hearing, taste, or other symptoms.ResultsSymptoms reported (in decreasing order of frequency) were auditory changes, taste changes, dizziness/lightheadedness, tingling in the extremities, and visual changes. The probability that volunteers will report symptoms is proportional to the dose of 2-chloroprocaine administered (auditory symptoms, P < .001; taste symptoms, P = .01; any symptoms, P < .001). Nalbuphine-premedicated volunteers were more likely to report symptoms (auditory symptoms, P = .004; taste symptoms, P = .004; any symptoms, P = .02). A dose of at least 1.5 mg/kg appears to be necessary to produce a 90% probability that patients will report symptoms when they receive 2-chloroprocaine intravenously.ConclusionsThis study suggests that patients who receive nalbuphine for analgesia prior to epidural placement will be more likely to report symptoms after receiving intravenous 2-chloroprocaine during epidural test dosing.