A simple model to teach three basic regional anesthesia principles.
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Anesthesia, Conduction↗
Biomedical subjects
D J Kopacz
Publications and source records attributed to D J Kopacz.
Comparison of needle deviation during regional anesthetic techniques in a laboratory model.
Although many characteristics of needles used for spinal and epidural anesthesia have been studied extensively, the amount that a needle deviates from a straight path while passing through tissue has been relatively ignored. A laboratory model was used to determine the amount of needle deviation produced when different types of new spinal needles and epidural needles were passed through porcine tissue. Both needle point design and, to a lesser extent, needle gauge were found to influence the amount and direction of needle deviation. Deviation was found to be the least for the pencil-point spinal needles (Whitacre, Sprotte, Safetap, range 0.60-1.00 mm/50 mm tissue, analysis of variance (ANOVA) P < 0.001). Needles commonly used for epidural anesthesia (Tuohy, Hustead, Crawford) exhibited increased deviation (range 1.73-3.54 mm/50 mm tissue), although the largest amount was seen with beveled spinal needles (Quincke, Atraucan) (range 4.42-5.90 mm/50 mm tissue). The possible clinical significance of needle deviation during the performance of a regional anesthetic is discussed.
Anesthesia, Epidural↗
Quantitative assessment of differential sensory nerve block after lidocaine spinal anesthesia.
BACKGROUND: Recent technology allows for quantitative and selective measurement of A beta, A delta, and C fiber nerve transmission. To gain further insight into the physiology of differential block after lidocaine spinal anesthesia, the function of these different fibers was quantitatively measured over time, and these measurements were correlated with regression of anesthesia to pinprick, touch, cold, and tolerance of tetanic electrical current (equivalent to surgical incision). METHODS: Six volunteers received lidocaine spinal anesthesia with 50 mg lidocaine (5% in dextrose). Cutaneous current perception thresholds at 2,000, 250, and 5 Hz, which stimulate A beta, A delta, and C fibers, respectively, were determined at L2-L3 (medial aspect above knee) before and every 10 min after spinal anesthesia. Dermatomal levels to pinprick, touch, and cold were assessed every 5 min after spinal anesthesia. Tolerance to tetanic electrical stimulus was assessed at L2-L3 every 10 min after spinal anesthesia. RESULTS: Differential block was demonstrated by the sequential return of sensation to touch, pinprick, and cold at L2-L3. Recovery of function of A beta, A delta, and C fibers correlated with return of sensation to touch (R2 = 0.7, p = 0.03), pinprick (R2 = 0.75, p = 0.02), and cold (R2 = 0.67, p = 0.04) respectively. Loss of tolerance of surgical anesthesia corresponded to return of A beta current perception thresholds to baseline, whereas current perception thresholds for A delta and C fibers were still increased to greater than baseline (p = 0.025). CONCLUSIONS: Differential sensory block during spinal anesthesia is due to different recovery profiles of A beta, A delta, and C fibers. Return of A beta current perception thresholds to baseline correlated with duration of surgical anesthesia as assessed with an electrical stimulation model.
Anesthesia Recovery Period↗
Effect of needle puncture on morphine and lidocaine flux through the spinal meninges of the monkey in vitro. Implications for combined spinal-epidural anesthesia.
BACKGROUND: Combined spinal-epidural anesthesia is a technique growing in popularity. However, there have been no attempts to investigate the risk of epidural drug reaching the subarachnoid space in high concentration by passing through the meningeal hole left by the spinal needle. This study begins to address this question by quantitating the flux of morphine and lidocaine through the spinal meninges of the monkey in vitro after puncture with three different-sized needles. METHODS: Spinal meningeal tissue from anesthetized monkeys was mounted in a diffusion cell and drug flux was measured through intact tissue and through tissue punctured with a 27-G Whitacre, a 24-G Sprotte, and an 18-G Tuohy needle. RESULTS: The flux of morphine through the meningeal tissue was significantly increased by puncture with each of the study needles. The flux of lidocaine was significantly increased only by puncture with the 24-G Sprotte and 18-G Tuohy needles. The flux of morphine through intact tissue was less than the flux of lidocaine through intact tissue. In contrast, the flux of morphine and lidocaine were the same through tissue punctured with the study needles. The magnitude of the drug flux through the needle puncture was a function of the diameter of the study needle. CONCLUSIONS: Epidural anesthesia after accidental or intentional puncture of the spinal meninges has occasionally resulted in high spinal blocks and total spinal anesthesia. This study suggests that drug movement through the meningeal hole is responsible for this complication and that the risk may be decreased by using the smallest possible needle to puncture the meninges.
Anesthesia, Epidural↗
Pharmacokinetics of ropivacaine and bupivacaine for bilateral intercostal blockade in healthy male volunteers.
BACKGROUND: Intercostal blockade produces the highest serum local anesthetic concentrations of all regional anesthetic techniques. The purpose of this study was to determine the pharmacokinetic properties of ropivacaine and bupivacaine after bilateral intercostal blockade. METHODS: The pharmacokinetics of ropivacaine (n = 7) and bupivacaine (n = 7) were determined in adult human volunteers from venous samples drawn over 24 h after bilateral intercostal blockade of T5-T11 with 140 mg of either drug (0.25% plain solutions, 56 ml). Sensory (pinprick, temperature, and touch) and motor blockade (RAM-test and integrated electromyography) were assessed every 2 h. RESULTS: There was no significant difference between the maximum plasma concentrations (Cmax) obtained for either drug (ropivacaine 1.1 +/- 0.4 microgram/ml, bupivacaine 0.9 +/- 0.2 microgram/ml, P = 0.39), and there were no toxic signs observed in the obtained plasma concentration ranges. Plasma concentrations tended to peak (tmax) earlier with ropivacaine (21 +/- 9 versus 30 +/- 8 min, P = 0.09). The terminal half-life (t1/2 beta) of ropivacaine (2.3 +/- 0.8 h) was significantly less than that for bupivacaine (4.6 +/- 2.6 h, P = 0.04). Sensory blockade measured by pinprick was of shorter duration with ropivacaine (6.0 +/- 2.5 h versus bupivacaine 10.0 +/- 3.0 h; P < 0.001). Likewise, motor blockade was less intense and of shorter duration for ropivacaine by RAM-test (P = 0.02). CONCLUSIONS: The results of this pharmacokinetic study indicate that 0.25% ropivacaine and 0.25% bupivacaine (56 ml, 140 mg) produce peak plasma levels less than those considered toxic when used in bilateral intercostal blockade. Studies of ropivacaine for intercostal blockade in surgical patients are necessary before the optimum concentration for efficacy and anesthetic/analgesic duration is identified.
Adult↗
A randomized, double-blind evaluation of ketorolac tromethamine for postoperative analgesia in ambulatory surgery patients.
BACKGROUND: Given the trend toward early discharge of patients after surgery and the inherent adverse effects of opioid analgesics, we compared a new nonsteroidal antiinflammatory drug, ketorolac tromethamine, given intravenously (iv) and then orally, with two commonly prescribed opioid analgesics in ambulatory patients for up to 1 week after surgery. METHODS: In this study incorporating a double-blind, multi-dose design, 221 patients who had moderate or severe pain after surgery were randomized to one of three treatment groups: group K30 received 30 mg iv ketorolac twice, then 10 mg iv every 30 min as required to control pain, up to six doses, followed by 10 mg oral ketorolac every 4-6 h; group F50 received 50 micrograms iv fentanyl at the same time intervals as in group K30, followed by 60 mg codeine plus 600 mg acetaminophen (C+A) orally every 4-6 h; and group F10 received the same combination as did group F50, but only 10 micrograms fentanyl per dose. RESULTS: Compared with 50 micrograms fentanyl iv, 30 mg iv ketorolac provided delayed but otherwise equivalent analgesic effects and was associated with similar side effects. Compared with C+A, 10 mg oral ketorolac was associated with a lower incidence of nausea and somnolence and earlier return of bowel function but not better pain relief, drug tolerability, quality of life, or psychologic well-being. CONCLUSIONS: Ketorolac, when used in an iv and then oral sequence, is a safe and effective analgesic in the ambulatory surgery setting. It has a slower onset than fentanyl, but causes fewer side effects than C+A.
Administration, Oral↗
Continuous spinal anaesthesia for abdominal surgery in a patient receiving amiodarone.
The perioperative management of a 57-yr-old patient receiving chronic amiodarone therapy with a continuous spinal anaesthetic for a low anterior resection of the colon is discussed. The most appropriate anaesthetic technique for patients receiving chronic amiodarone therapy remains controversial, but the avoidance of general anaesthesia may be beneficial because of the risk of postoperative pulmonary failure. In this patient continuous spinal anaesthesia was slowly titrated to the desired level, coincident haemodynamic alterations were easily treated as they developed, and high serum local anaesthetic concentrations which occur with other regional anaesthetic techniques were avoided.
Adenocarcinoma↗
Accidental epidural cephazolin injection: safeguards for patient-controlled analgesia.
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Adolescent↗
Securing epidural catheters: a further modification.
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Catheters, Indwelling↗
Effect of ropivacaine on cutaneous capillary blood flow in pigs.
The effect of subcutaneous infiltration of ropivacaine and bupivacaine on local cutaneous blood flow was assessed by the laser Doppler method. One milliliter of each of ten test solutions (ropivacaine 0.25% and 0.75%, bupivacaine 0.25% and 0.75%, and saline, each with and without added epinephrine 5 micrograms/ml) was injected subcutaneously at separate sites on the side of each pig (n = 6). Skin blood flow was measured by laser Doppler at all sites before and 5, 10, 15, and 30 min after injection. Subcutaneous injection of ropivacaine 0.25% or 0.75% decreased cutaneous blood flow by a maximum of 52% +/- 11% and 54% +/- 14% (mean +/- SE), respectively. In contrast, bupivacaine 0.25% or 0.75% increased flow by 90% +/- 32% and 82% +/- 48%, and injection of saline increased blood flow by 32% +/- 17%. Cutaneous blood flow after the injection of ropivacaine was significantly lower than after injection of bupivacaine or saline, and was also lower than at the uninjected control site (P = 0.0009). All of the solutions with epinephrine decreased blood flow to a similar extent (48-73%, P = 0.3). The ability of ropivacaine to produce cutaneous vasoconstriction offers several advantages over the other local anesthetics presently available for infiltration anesthesia.
Amides↗
Accuracy of laser Doppler capillary flow measurements for predicting blood loss from skin incisions in pigs.
This study assesses the clinical applicability of laser Doppler capillary flow measurements for predicting blood loss from a surgical incision. To produce a wide range of blood flows, we injected lidocaine 1%, lidocaine 1% plus octapressin (0.03 IU.ml-1), and lidocaine 1% plus epinephrine (5 micrograms.ml-1) subcutaneously into three separate sites on the flank of each animal (N = 6). Laser Doppler flow measurements were made before and 10 minutes after injection Subcutaneous injection of lidocaine tended to increase cutaneous blood flow (96 +/- 13 to 153 +/- 30 mV, mean +/- SE, P = 0.09). Blood flow tended to decrease after injection of lidocaine with epinephrine (101 +/- 13 to 57 +/- 10 mV, P = 0.03) or octapressin (108 +/- 20 to 58 +/- 11 mV, P = 0.08). Laser Doppler measurements were higher after the injection of plain lidocaine than after that of lidocaine with either epinephrine or octapressin (P = 0.004). A standard incision was performed at each site and blood loss measured over the subsequent 10 minutes. Laser Doppler measurements correlated with the amount of bleeding from the surgical incision (R = 0.69, P less than 0.001). We conclude that the laser Doppler is a useful tool for evaluating the ability of subcutaneously injected local anesthetics (vasodilators) or vasoconstrictors to alter bleeding from skin incisions.
Animals↗
Training anesthesia personnel to perform bleeding times.
Template bleeding time results generated by residents in anesthesiology correlate well with those obtained by trained laboratory personnel (p less than 0.002). Anesthesia personnel can accurately perform bleeding time tests when laboratory support is not available. The results of these tests can be used to guide clinical decisions.
Anesthesiology↗
The reliability of epidural anesthesia for repeat ESWL: a study of changes in epidural compliance.
Changes in epidural compliance were investigated before and after extracorporeal shock wave lithotripsy (ESWL) in 11 outpatients. Epidural pressures were unchanged acutely by ESWL (p greater than 0.15). In contrast to previous reports of failures of epidural anesthesia in patients having repeat ESWL treatments, a review of our population of patients having repeat ESWL indicates that epidural anesthesia is reliable and not associated with any greater failure rate than for initial ESWL treatments. The difference between our results and previous reports of high failure rates is likely due to differences in anesthetic and surgical techniques such as: (1) use of air for loss-of-resistance when locating the epidural space, (2) differences in the time interval between ESWL treatments, and (3) frequency of use of epidural catheters.
Anesthesia, Epidural↗
Chloroprocaine and lidocaine decrease hospital stay and admission rate after outpatient epidural anesthesia.
Lumbar epidural anesthesia with 20 ml of either 3% 2-chloroprocaine (C), 1.5% lidocaine (L), or 1.5% mepivacaine (M) with epinephrine was studied in 84 outpatients undergoing surgery (extracorporeal shock wave lithotripsy (ESWL]. The average duration of the procedure was 31.9 minutes. The total duration of sensory anesthesia was 133 +/- 28 minutes (C), 182 +/- 38 (L), and 247 +/- 42 (M) (p less than 0.05). Times to discharge were 269 +/- 62 minutes (C), 284 +/- 62 (L), and 357 +/- 71 (M). The time to discharge with M, almost six hours, was significantly longer than with C or L. There was a trend to an increasing rate of unplanned overnight hospital admission with increasing duration of the local anesthetic drug employed. Continuous epidural anesthesia with C, L or M appears safe and effective for outpatient surgical procedures such as ESWL. In contrast to previous understanding, mepivacaine produces significantly longer anesthesia and recovery times and may not be optimal for outpatient epidural use.
Adult↗