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Biomedical subjects

K Drasner

Publications and source records attributed to K Drasner.

At least 37 records · Page 2Linked to original sources
PubMed1995

Local anesthetic test dose as a predictor of effective epidural opioid analgesia.

BACKGROUND: When local anesthetic is used to produce epidural anesthesia intraoperatively, epidural catheter placement is confirmed. However, when epidural catheters are placed intraoperatively only to provide postoperative opioid analgesia, correct catheter placement may not be confirmed by administration of a local anesthetic. The current study tests the hypothesis that the extent of sensory blockade produced by a 10-ml dose of 1.5% lidocaine can be used to predict the adequacy of epidural opioid analgesia. METHODS: Forty-nine patients undergoing major abdominal surgery in whom a lumbar epidural catheter was placed intraoperatively were studied, but no more than 3 ml 1% lidocaine had been injected. Placement of the epidural catheter was assessed in the postanesthesia care unit by administration of a 10-ml dose of 1.5% lidocaine. The extent of sensory blockade was determined using the pinprick technique: All dermatomes, T2 and below, were assessed and scored using 1 point per dermatome per side from L1 to T2 to a maximum of 24 points. Scores were arbitrarily divided into three groups, where group 1, 0-7 points; group 2, 8-15 points; and group 3, 16-24 points. Epidural morphine infusion was initiated independently of the extent of the sensory blockade and adjusted using predetermined guidelines. Adequacy of opioid-induced analgesia was determined using the visual analog scale. RESULTS: Significantly lower visual analog scale scores for pain at rest and with movement from epidural morphine infusion were associated with sensory blockade score of 16-24 points. Seven patients failed to obtain a detectable sensory block. No patient requested alternative analgesia. None of the epidural catheters was removed because of inadequate pain relief, even in patients who failed to obtain a detectable sensory block. CONCLUSIONS: Extensive sensory block from 10 ml 1.5% lidocaine was associated with excellent epidural opioid analgesia. Extent of analgesia after a 10-ml test dose of 1.5% lidocaine can be used to predict the adequacy of analgesia resulting from an epidural opioid infusion. The failure of a local anesthetic dose to produce sensory blockade does not necessarily predict a failure to produce analgesia from an epidural opioid infusion, as indicated by the presence of analgesia in several patients without detectable sensory block.

Analgesia, Epidural↗
PubMed1994

Persistent sacral sensory deficit induced by intrathecal local anesthetic infusion in the rat.

BACKGROUND: Several cases of cauda equina syndrome after continuous spinal anesthesia have been recently reported. One possible etiology is toxic exposure of the sacral roots resulting from intrathecal maldistribution of a relatively large dose of local anesthetic. The current experiments sought to determine whether a local anesthetic solution, injected intrathecally to produce a restricted distribution of anesthesia, could result in a sacral deficit. In addition, we sought to test the hypothesis that, when equal volumes are administered intrathecally, significant differences exist in the potential to three commonly used anesthetic solutions to induce sensory impairment. METHODS: Thirty-two rats were implanted with intrathecal catheters to permit repetitive infusion of local anesthetic. Animals were randomly assigned to four groups of eight to receive either 5% lidocaine with 7.5% dextrose; 0.75% bupivacaine with 8.25% dextrose; 0.5% tetracaine with 5% dextrose; or normal saline. Each rat received, in sequence, a 1-h (60 microliters), a 2-h (120 microliters), and a 4-h (240 microliters) infusion; the infusions were separated by a 4-day rest period. Sensory function was assessed using the tail-flick test, which was performed immediately before each infusion and 6 days after the last infusion by an investigator blinded to the solution infused. RESULTS: There was no significant difference in baseline tail-flick latencies for the four groups. Tail-flick latency for the lidocaine group was significantly prolonged when compared with the bupivacaine, tetracaine, and saline groups. This difference was apparent after the first infusion and persisted throughout the study. CONCLUSIONS: In the rat, restricted anesthetic distribution can be achieved, and sensory impairment may result. These findings further support an etiology of local anesthetic neurotoxicity for recent clinical injuries after continuous spinal anesthesia. The functional model described appears to be suitable for in vivo study of local anesthetic neurotoxicity.

Anesthesia, Local↗
PubMed1994

In vitro modeling of spinal anesthesia. A digital video image processing technique and its application to catheter characterization.

BACKGROUND: Maldistribution of intrathecal local anesthetic has recently been implicated as a contributor to neurotoxic injury. In vitro modeling can be used to understand the distribution of anesthetic agents within the subarachnoid space. We describe an in vitro modeling technique that uses digital video image processing and its application to catheter injection of local anesthetic. METHODS: A clear plastic model of the subarachnoid space, including a simulated spinal cord and cauda equina, was filled with lactated Ringer's solution. Phthalocyanine blue dye of known concentration was injected into the model through small-bore (28-G) and large-bore (18-G) catheters. Injections were performed at a variety of controlled rates and sacral catheter positions, and the propagation of dye throughout the model was recorded on videotape, digitized by computer, and converted to a two-dimensional image of dye concentration. A subset of data was compared with results obtained from spectrophotometric analysis. RESULTS: There was a strong correlation (r = 0.98) between data obtained with analysis by digital video image processing and those obtained spectrophotometrically. Catheter size, catheter angle, and injection rate significantly influenced the distribution and peak concentration of simulated anesthetic. No major differences in distribution or peak concentration were observed with the two types of 28-G catheters. CONCLUSIONS: The digital video image processing technique can be used to quantify anesthetic distribution rapidly within a model of the subarachnoid space without disturbing the distribution. The current results demonstrate a strong dependence of anesthetic distribution on catheter angle, catheter size, and injection rate. Comparisons between 28-G catheters suggest that the difference in reported incidence of cauda equina syndrome associated with different 28-G catheters cannot be explained on the basis of differences in anesthetic distribution.

Anesthesia, Spinal↗
PubMed1991

Lumbar intrathecal morphine alters activity of putative nociceptive modulatory neurons in rostral ventromedial medulla.

Two physiologically and pharmacologically distinct classes of putative nociceptive modulatory neurons have been identified in the rostral ventral medulla (RVM) of the lightly anesthetized rat: on-cells and off-cells. We have previously shown that administration of morphine either systemically or by microinjection into the periaqueductal gray (PAG) produces an increase in the activity of all off-cells and a depression of the activity of all on-cells concomitant with inhibition of the tail flick reflex. We now demonstrate that morphine applied intrathecally has effects on RVM neurons that are indistinguishable from those of systemic or PAG administration. This may contribute to the known multiplicative effects of concurrent administration of opioids at spinal and supraspinal sites.

Animals↗
PubMed1991

Distribution of catheter-injected local anesthetic in a model of the subarachnoid space.

Maldistribution of local anesthetic administered through a subarachnoid catheter recently has been implicated as a possible cause of sacral root injury. To examine subarachnoid distribution of catheter-injected local anesthetic, we constructed a model of the subarachnoid space and administered solutions containing lidocaine and methylene blue through sacrally directed catheters. We studied three catheters: a 28-G endport, a 20-G endport, and a 20-G multiple sideport. To determine the injection rates to be used, ten clinicians were observed while they performed mock subarachnoid injections: the mean (+/- standard deviation) "normal" injection times for the 28-G and 20-G catheters were 52.6 +/- 17.2 and 11.9 +/- 7.2 s, respectively. The correlation coefficient for lidocaine concentration estimated by methylene blue spectrophotometric absorbance and measured by immunoassay was 0.977. Administration of hyperbaric local anesthetic through a sacrally directed catheter resulted in restricted distribution of anesthetic with a relatively high peak concentration. Rate of injection was a critical factor affecting distribution; faster injections tended to distribute solution more uniformly and to a higher segmental level, resulting in substantially lower peak concentrations. When catheters were injected at clinically relevant rates, the 28-G catheter produced the greatest degree of maldistribution; this difference appeared to be primarily a function of flow rate. Differences in peak lidocaine concentration between the two 20-G catheters were neither large nor consistent. However, despite sacral placement, the multiple-sideport catheter distributed anesthetic toward "higher" spinal segments more consistently. Distribution was more favorable when the injected solution was less dense (closer to isobaric).(ABSTRACT TRUNCATED AT 250 WORDS)

Anesthesia, Spinal↗
PubMed1991

Use of intrathecally administered morphine in the treatment of postoperative pain after lumbar spinal surgery: a prospective, double-blind, placebo-controlled study.

Improved control of postoperative pain is now known to reduce the incidence of morbidity. Although spinally administered narcotics have found a clear role in chest and abdominal surgery, their role in lumbar spinal surgery is debated. We conducted a prospective, double-blind, randomized, placebo-controlled trial of intrathecally administered morphine sulfate after lumbar spinal surgery in 56 patients. Patients received 0, 0.125, 0.25, or 0.5 mg of intrathecally administered morphine during extradural lumbar spinal operations, and the effects on postoperative analog pain scores, narcotic consumption, complications, and length of hospitalization were assessed. As compared with systemic narcotic administration, intrathecally administered morphine provided superior analgesia in a dose-dependent fashion without an increase in narcotic side effects. Consumption of parenteral narcotics on the first postoperative day and over the total hospitalization period decreased in correlation with increasing doses of intrathecally administered morphine. Mean length of hospitalization was significantly decreased, as compared with the control group, in patients receiving 0.25 or 0.5 mg of intrathecally administered morphine. When proper precautions are observed, intrathecally administered morphine can improve the postoperative care of patients undergoing lumbar spinal surgery.

Aged↗
PubMed1991

Cauda equina syndrome after continuous spinal anesthesia.

Four cases of cauda equina syndrome occurring after continuous spinal anesthesia are reported. In all four cases, there was evidence of a focal sensory block and, to achieve adequate analgesia, a dose of local anesthetic was given that was greater than that usually administered with a single-injection technique. We postulate that the combination of maldistribution and a relatively high dose of local anesthetic resulted in neurotoxic injury. Suggestions that may reduce the potential for neurotoxicity are discussed. Use of a lower concentration and a "ceiling" or maximum dose of local anesthetic to establish the block should be considered. If maldistribution of local anesthetic is suspected (as indicated by a focal sensory block), the use of maneuvers to increase the spread of local anesthetic is recommended. If such maneuvers prove unsuccessful, the technique should be abandoned.

Aged↗
PubMed1990

Is chronic ethanol consumption associated with tolerance to intrathecal lidocaine in the rat?

Intoxication with alcohols can produce anesthesia. In contrast, chronic ethanol consumption can produce tolerance to inhaled and other general anesthetics. We tested whether ongoing consumption decreased, and whether withdrawal from such consumption increased, the intrathecal dose of lidocaine that induces sensory and motor blockade in female Sprague-Dawley rats. Sensory blockade was assessed using the tail-flick test, and motor blockade by the animal's inability to move its hind limbs. Rats were tested before commencing ethanol intake; during ethanol ingestion (9 days after beginning ingestion); and on the 15th day of ingestion, 14 h after withdrawing ethanol from their diet. Pair-fed control rats were tested at the same intervals. Ongoing administration of ethanol decreased the dose of lidocaine required to produce sensory blockade, but this difference was not significant relative to the control group (i.e., the difference was significant within group but not across groups). Withdrawal of ethanol increased the dose requirements for sensory and motor blockade by 80% and 53% (P less than 0.01 and P less than 0.0001) and decreased the duration of the motor blockade (P less than 0.01). Dose requirements producing sensory block differed between alcoholic and control groups (P less than 0.0001). These results suggest that chronic ethanol intake produces tolerance to the local anesthetic effects of lidocaine. Whether this change results from a change in kinetics or in sensitivity is not known, but the latter would seem more likely, because duration of blockade was minimally affected or unaffected.

Alcoholism↗
PubMed1990

Preoperative laboratory testing of children undergoing elective surgery.

The routine preoperative evaluation of pediatric patients often includes a history, physical examination, complete blood count, and urinalysis (UA). We retrospectively reviewed the records of 486 elective surgeries in children to determine the role of abnormal preoperative laboratory test results in perioperative management. Anemia or microcytosis was apparent in 17% of patients, and abnormal UA results were found in 15%. More than 80% of the abnormal UA results were historically known, clinically insignificant, or false-positives. Only five children had surgery canceled owing to abnormal laboratory tests: two owing to anemia, two to an abnormal UA, and one because of a prolonged partial thromboplastin time. Both children with anemia were treated with iron and subsequently underwent surgery without complication. Of the abnormal UAs, one was contaminated, and the cancellation of surgery resulted in a complication requiring emergency surgery. The other abnormal UA was a probable asymptomatic bacteriuria, and the infant later underwent surgery uneventfully. These data suggest that a routine UA adds little to the preoperative evaluation of a healthy child, and should be omitted.

Adolescent↗
PubMed1989

Opioid peptides (DAGO-enkephalin, dynorphin A(1-13), BAM 22P) microinjected into the rat brainstem: comparison of their antinociceptive effect and their effect on neuronal firing in the rostral ventromedial medulla.

The highly mu-selective agonist Tyr-D-Ala-Gly-MePhe-Gly-ol-enkephalin (DAGO) produces potent, dose-dependent naloxone-reversible antinociception when microinjected into the ventrolateral periaqueductal gray (PAG) (ED50 = 0.72 nmol) or rostral ventromedial medulla (RVM) (ED50 = 0.05 nmol) as measured on the rat tail flick (TF) assay. In single-unit recording experiments, DAGO microinjected into the PAG also affected On- and Off-Cell firing in the RVM in the same way as previously demonstrated by our group for morphine. PAG-microinjected DAGO inhibits spontaneous and noxious-evoked On-Cell firing (attenuating the characteristic On-Cell burst) (n = 19), and excites spontaneous Off-Cell firing, preventing the characteristic Off-Cell pause (n = 12) at doses which suppress the TF. These results support a major role for the mu receptor in PAG and RVM mechanisms of opiate antinociception. In our experiments using BAM22P, an endogenous weakly mu-selective opioid peptide, we could not demonstrate a dose-dependent antinociceptive effect, whether the peptide was microinjected supraspinally into the PAG (n = 9) or RVM (n = 11), or intrathecally at the lumbar cord (n = 4). In two animals, a naloxone-reversible antinociceptive effect was observed following the microinjection of 10 nmol BAM 22P into the RVM; however, no effect was seen in 3 animals microinjected with 20 nmol. Dyn A(1-13), a putative endogenous ligand for the kappa receptor, had no antinociceptive effect when microinjected into the ventrolateral PAG, and no effect on the firing (spontaneous or noxious-evoked) of RVM On (n = 3)- or Off (n = 2)-Cells.

Action Potentials↗
PubMed1988

Intrathecal morphine reduces the minimum alveolar concentration of halothane in humans.

The authors hypothesized that the analgesia provided by intraspinal opiates would decrease anesthetic requirement. To test this hypothesis, 20 women undergoing major gynecologic surgery were divided randomly into two groups. One group received 0.75 mg morphine sulfate intrathecally, and the other, the same dose intramuscularly (control), prior to the induction of anesthesia with halothane. MAC for halothane was 0.81% in the control group and 0.46% in the intrathecal morphine group (P = 0.024). The reduction in anesthetic requirement due to intrathecal morphine is greater than that produced by low to moderate doses of systemically administered opiates.

Anesthesia, Inhalation↗