Onset Of Epidural Anesthesia Research Articles

Evaluation of perfusion index as a noninvasive tool to determine epidural anesthesia effectiveness in dogs

ObjectiveTo evaluate perfusion index (PI) as a noninvasive tool to determine effectiveness and onset of epidural anesthesia in dogs. Study designProspective clinical trial. AnimalsA total of 21 adult dogs, aged 6.5 ± 3 years and weighing 34.9 ± 6.4 kg, undergoing a tibial plateau leveling osteotomy. MethodsDogs were premedicated intramuscularly with acepromazine (0.03 mg kg–1) and hydromorphone (0.1 mg kg–1) and anesthetized with intravenous propofol (to effect) and isoflurane in oxygen. A surface transflectance probe was secured to the tail base to monitor PI and a dorsal pedal artery catheter was placed for invasive blood pressure monitoring. A lumbosacral epidural was performed with the dog in sternal recumbency. Dogs were randomly assigned for inclusion of epidural morphine (0.1 mg kg–1) or morphine (0.1 mg kg–1) and lidocaine (4 mg kg–1). PI was recorded following instrumentation of each dog just prior to the epidural (baseline), at 10 minute intervals for 30 minutes, before and after the surgical skin incision and before and after completion of the osteotomy. Physiological variables and end-tidal isoflurane were recorded at the same time points. ResultsThere was no significant difference in PI between the groups at any time point. There was a significant change in end-tidal isoflurane before and after the skin incision in the epidural morphine and epidural morphine–lidocaine groups (p = 0.04, p = 0.05, respectively) and before and after the osteotomy in each group for heart rate (p = 0.001, p = 0.04), diastolic (p = 0.01, p = 0.01) and mean arterial blood pressure (p = 0.03, p = 0.05). Conclusions and clinical relevancePI did not provide an objective means for determining the onset or effectiveness of epidural anesthesia in anesthetized dogs and alternate methods of noninvasive assessment should be investigated.

Caudal Epidural Xylazineor Xylazine/Lidocainecombination in Camels (Camelus Dromedarius) and its Reversal by Atipamezole

Caudal epidural xylazine 2% (0.15 mg/kg) or xylazine (0.10 mg/kg) /lidocaine 2% (0.22 mg/kg) combination anesthesia through the first intercoccygeal space was evaluated in 8 camels (16 trials). The total volume administered was fixed at 5.0 ml by adding 0.9% NaCl. The onset of epidural anesthesia was significantly faster (P 0.05) with xylazine/lidocaine (98.3 ± 1.0 minutes) than with xylazine (71.6 ± 1.8 minutes). The reversal of epidural xylazine or xylazine/lidocaine induced- analgesia with IV atipamezole at (5.0 µg/kg, 10.0 µg/kg or 15.0µg/kg) was evaluated in 8 camels (13 trials). The total volume administered was fixed at 5.0 ml by adding 0.9% NaCl. Atipamezole at 15.0 µg/kg was the optimum dose rate for reversing the analgesic effect and provoked marked signs of arousal within few seconds without any side effects. We can concluded that caudal epidural anesthesia was easily performed in camels in standing position with xylazine or its combination with lidocaine. IV atipamezole at 15.0µg/kg for effectively reversing the induced caudal epidural anesthesia.

Epidural anesthesia in Egyptian water buffalo (Bubalus bubalis): a comparison of lidocaine, xylazine and a combination of lidocaine and xylazine

ObjectiveTo evaluate and compare the analgesic effects of a combination of lidocaine and xylazine to lidocaine or xylazine administered alone for epidural anesthesia in Egyptian water buffalo (Bubalus bubalis). Study designProspective, randomized, ‘blinded’, crossover experimental study. AnimalsA total of 12 female Egyptian water buffalo. MethodsBuffalo were randomly assigned to one of three epidural treatments administered through the sacrococcygeal joint: a local anesthetic (2% lidocaine, 0.22 mg kg−1), an alpha-2-adrenergic agonist (xylazine, 0.1 mg kg−1) or a combination of both drugs in a crossover fashion with a 14 day washout period. The total volume of each treatment was fixed at 7.0 mL by adding 0.9% NaCl. Onset, maximal effect, and duration of epidural anesthesia were recorded. ResultsCaudal epidural anesthesia was easily performed, and all three treatments produced local anesthesia of the tail and perineal structures of standing buffalo. Onset of epidural anesthesia was faster (p < 0.05) with lidocaine (3.4 ± 0.9 minutes) than with xylazine (9.1 ± 1.1 minutes) or lidocaine-xylazine (6.4 ± 1.1 minutes). The maximal effect of epidural anesthesia was reached faster (p < 0.05) with lidocaine (5.9 ± 0.64 minutes) than xylazine (14.4 ± 1.1 minutes) or lidocaine-xylazine (12.9 ± 0.64 minutes). The duration of epidural anesthesia was longer (p < 0.05) with lidocaine-xylazine (145.8 ± 3.3 minutes) than either lidocaine (118.4 ± 2.7 minutes) or xylazine (102.1 ± 3.7 minutes) administered alone. None of the treatments produced ataxia. Conclusions and clinical relevanceCaudal epidural anesthesia was easily performed in Egyptian water buffalo by administering a local anesthetic, an alpha-2-adrenergic agonist or a combination of both drugs through the sacrococcygeal joint. Administering a combination of lidocaine and xylazine provided a longer duration of anesthesia than either drug used alone. Epidural xylazine provided a useful level of systemic sedation without ataxia.

Optimal Dose of Epidural Dexmedetomidine Added to Ropivacaine for Epidural Labor Analgesia: A Pilot Study.

Background Dexmedetomidine combined with local anesthetics can decrease the concentration of epidural ropivacaine. However, the optimal dose of epidural dexmedetomidine combined with ropivacaine for labor analgesia is still uncertain. This study investigated the effect of adding different dose of epidural dexmedetomidine to ropivacaine during epidural labor analgesia. Methods One hundred women were randomly assigned to one of the four groups (Groups A, B, C, and D received 0.25, 0.5, 0.75, and 1 μg/ml of dexmedetomidine plus 0.1% ropivacaine, resp.). The onset of epidural anesthesia and stages of labor were studied, and pain was assessed using a visual analogue scale (VAS). Hemodynamic parameters and fetal heart rate were monitored. Apgar scores and umbilical artery pH were recorded. The side effects, if any, were recorded also. Results The addition of 0.25, 0.5, and 0.75 μg/ml of dexmedetomidine to 0.1% ropivacaine provided safe and effective analgesia, but 1 μg/ml of dexmedetomidine resulted in increasing incidence of motor block. The hemodynamic parameters were similar between groups (P > 0.05). Side effects in Group D were significantly higher than those in the other three groups (P < 0.05). Conclusions When dexmedetomidine is combined with 0.1% ropivacaine, the optimal concentration of dexmedetomidine is 0.5 μg/ml for epidural labor analgesia (this trial is registered with ChiCTR-OPC-16008548).

BIS versus skin conductance for assessment of depth of sedation induced by propofol target-controlled infusion

Objective To compare the accuracy of BIS and skin conductance (SC) for assessment of the depth of sedation induced by target-controlled infusion (TCI) of propofol. Methods Thirty ASA Ⅰ orⅡpatients aged 21-56 yr weighing 52-85 kg undergoing orthopedic operation on the lower limb under epidural anesthesia were enrolled in this study.After the onset of epidural anesthesia, TCI of propofol was started at an initial target plasma concentration (Cp) of 0.8 μg/ml. Th Cp was increased by 0.5-0.8 μg/ml every 3 min until OAA/S score=1. OAA/S score, BIS and SC values were recorded, SC change value (△SC) was calculated. Spearman rank-order correlation, receiver operating characteristic curve (area under curve was calculated) and logistic regression were used to analyze the relationship of OAA/S score to BIS and △SC.Results BIS and △SC were significantly correlated with OAA/S scores (r were 0.920 and-0.859 respectively). The AUC of △SC (0.919, 0.946) was significantly better correlated with OAA/S score (5→4, 4→3) than that of BIS (0.761, 0.507), while BIS was better correlated (0.781, 0.959) with OAA/S score (3→2, 2→1) than ASC (0.577, 0.630). Logistic regression correctly predicted loss of consciousness. The accuracy of prediction was 93% for BIS and 82% for △SC. Conclusion The accuracy of SC for assessment of the depth of sedation induced by propofol TCI ishigher than that of BIS before loss of consciousness,while lower than that of BIS after loss of consciousness. BIS is more accurate in monitoring the loss of consciousness. Key words: Electroencephalography; Galvanic skin response; Propofol; Conscious sedation; Drug delivery systems

Failure of Augmentation of Labor Epidural Analgesia for Intrapartum Cesarean Delivery: A Retrospective Review

In this study, we aimed to identify the incidence and predictive factors associated with failed labor epidural augmentation for cesarean delivery. Data of parturients, who had received neuraxial labor analgesia and who subsequently required intrapartum cesarean delivery during an 18-mo period, were retrospectively studied. Predictors associated with failure of extension of epidural analgesia in the presence of adequate time for onset of epidural anesthesia were identified by univariate logistic regression. Of the 1025 parturients, 1.7% had failed epidural extension. Predictors of failed epidural anesthesia included initiation of labor analgesia with plain epidural technique (compared to combined spinal-epidural) (P = 0.001), >or=2 episodes of breakthrough pain during labor (P < 0.001) and prolonged duration of neuraxial labor analgesia (P = 0.02).

A thoracic-epidural granulocytic sarcoma case that was diagnosed preceding the onset of and that recurred co-incidental to acute promyelocytic leukemia, which developed after surgical treatment.

Granulocytic sarcoma or chloroma is a tumor seen in myelocytic leukemia. Spinal epidural onset is rare and is generally seen before or together with the onset of myelocytic leukemia. An epidural mass located at the 2nd-5th thoracic levels in an 18-year-old male patient was pathologically diagnosed as granulocytic sarcoma. Radiotherapy was performed after surgical intervention. Ten months later, he was re-admitted with abdominal pain. At this time, an epidural mass at the 6th-9th thoracic levels was detected on magnetic resonance imaging, and acute promyelocytic leukemia was diagnosed. After systemic chemotherapy, partial remission was achieved. We aimed to present this rare case with its remarkable follow-up findings.

The Trendelenburg Position Increases the Spread and Accelerates the Onset of Epidural Anesthesia for Cesarean Section

The Trendelenburg Position Increases the Spread and Accelerates the Onset of Epidural Anesthesia for Cesarean Section

Hemodynamic effects of oral clonidine premedication in lumbar epidural anesthesia.

Clonidine, an α2-adrenergic agonist, has a potent sympatholytic effect and augments the pressor effect of ephedrine during general anesthesia. We evaluated whether oral clonidine premedication would alter the hemodynamic changes and enhance the pressor response to intravenous ephedrine during epidural anesthesia in 35 adult patients. They were randomly administered either premedication with clonidine approximately 5 μg·kg-1 po (n=17) or no clonidine medication (n=18). After establishment of epidural anesthesia, the hemodynamic response to ephedrine iv was measured in the awake state at 1-min intervals for 10 min. Then, the same hemodynamic measurement was repeated in the asleep state induced with midazolam iv. There were no differences in blood pressure (BP) and heart rate values between groups during the onset of epidural anesthesia, except that BP before epidural anesthesia was lower in the clonidine group than the control group (P<0.05). The magnitude and duration of pressor responses to ephedrine were comparable between groups in awake and asleep states. In conclusion oral clonidine premedication 5 μg·kg-1 alters neither the hemodynamic changes nor the pressor response to intravenous ephedrine during epidural anesthesia.

Leukocytosis after fluid loading and induction of epidural anesthesia.

The present study shows that leukocytosis occurs from fluid loading and from the small amounts of adrenaline given epidurally. Five healthy volunteers received an intravenous infusion of 25 ml·kg-1 b.w. of Ringer's acetate solution over 15, 30, 45, and 80 min, and epidural anesthesia (EDA) was induced in 25 urology patients using mepivacaine 2% with or without adrenaline 1∶200 000. In the volunteers, we found that the total leukocyte count increased by up to 33% within 1 h after rapid volume loading. This increase was accounted for by neutrophils and lymphocytes. In the patients, the leukocyte count increased by 32% during the onset of EDA when mepivacaine with adrenaline was used. This increase was accounted for by lymphocytes. Our results suggest that caution is needed when interpreting the importance of a raised leukocyte count in samples taken in association with fluid loading and also when EDA is induced by a local anesthestic solution that contains adrenaline.

The effect of epidural anaesthesia on peripheral resistance and graft flow following femorodistal reconstruction

To determine the extent to which epidural anaesthesia influences peripheral resistance and graft blood flow following femorocrural reconstruction. Prospective, controlled study measuring blood flow, arterial pressure and peripheral resistance in femorocrural bypass grafts for 20 min following onset of epidural anaesthesia with 15ml of 0.25% bupivacaine. Twenty patients undergoing femorocrural reconstruction for critical lower-limb ischaemia with in situ long saphenous vein, under general anaesthesia. Ten patients had epidural cannulae inserted preoperatively and injected with bupivacaine after completion of the graft. Peripheral resistance fell in all 10 patients receiving epidural anaesthesia from a mean (range) of 1.07 PRU (0.32-2.2) to 0.49 PRU (0.19-0.72), compared to control values of 0.95 PRU (0.39-2.0) to 0.91 PRU (0.41-1.51; P < 0.01, Wilcoxon). There was a tendency for blood pressure to fall in the study patients (not significant) but graft blood flow still increased from 98 ml min-1 (41-221) to 160 ml min-1 (101-250), compared to flow in the control patients of 101 ml min-1 (45-176) at baseline to 104 ml min-1 (56-168; p < 0.01) at 20 min. Epidural anaesthesia significantly decreases peripheral resistance and increases graft blood flow in femorocrural grafts and would appear, therefore, to be of benefit for patients undergoing femorodistal reconstruction.

Mechanism of Mesenteric Venodilatation after Epidural Lidocaine in Rabbits

Increased splanchnic venous capacitance has been observed during extensive thoracolumbar epidural anesthesia in rabbits, but the mechanism is not clear. The present study examines the contributions of intravascular pressure changes, catecholamine levels, neural input, and direct effects of lidocaine to mesenteric venodilatation. Epidural catheters were inserted in rabbits anesthetized with alpha-chloralose. Vein diameter was measured by videomicrography from segments of ileum externalized in situ. Plasma epinephrine and norepinephrine levels were measured in animals receiving epidural blockade (0.4 ml/kg lidocaine 1.5%, n = 5) and in control animals given intramuscular lidocaine 15 mg/kg (n = 5). Intraluminal pressure was monitored during the onset of epidural anesthesia (0.4 ml/kg lidocaine 1.0%, n = 9) by a servo-null micropressure technique. The effect of inhibiting norepinephrine release from sympathetic nerves in the mesenteric veins was determined by using topical tetrodotoxin (n = 8) and by assessing the effect of topical lidocaine (10 and 100 micrograms/ml, n = 5) administered in the solution bathing the mesentery. Epidural injectate extended from T2 to L5. Plasma epinephrine decreased 68.3 +/- 4.4% (mean +/- SEM) with epidural anesthesia, and norepinephrine was lower after epidural block than after intramuscular lidocaine (1,868 +/- 290 pg/ml vs. 3,049 +/- 712 pg/ml). Mesenteric vein pressure decreased 35.3 +/- 3.5% and vein diameter increased 10.2 +/- 3.3% during epidural blockade. Tetrodotoxin caused mesenteric venodilatation (7.6 +/- 2.0%) and prevented venodilatation by subsequent epidural lidocaine. Topical lidocaine 10 micrograms/kg produced no change in vein diameter, but lidocaine 100 micrograms/ml increased it 3.5 +/- 1.3%. Splanchnic venodilatation during epidural anesthesia is an active process: a decrease in intravenous pressure concurrent with dilatation indicates that vein wall tension diminished. Significant dilatation with tetrodotoxin and lack of dilatation with subsequent epidural block point to a minor role for changes in circulating catecholamines. A direct effect of lidocaine does not contribute to splanchnic venodilatation except when circulating lidocaine concentrations reach very high levels.

Does the addition of tris(hydroxymethyl) aminomethane to 0.5% bupivacaine delay epidural onset in parturients?

A rapid onset of epidural anesthesia may predispose a pregnant patient to hypotension during the first stage of labor. Sodium bicarbonate has been reported to hasten epidural onset of chloroprocaine, lidocaine and bupivacaine while tris(hydroxymethyl) aminomethane (THAM) has been shown to delay the onset of epidurally administered chloroprocaine in parturients. The purpose of this study was to determine whether the addition of THAM to bupivacaine affected the onset, cephalad spread and incidence of hypotension following epidural administration in healthy pregnant patients during the first stage of labor. Three groups each consisting of 20 ASA I or II patients were studied. Group I received 0.5% bupivacaine with saline (0.06 ml/10 ml). Group II received bupivacaine buffered with THAM (0.06 ml/10 ml) to a pH of 6.8. Group III received bupivacaine buffered to a pH of 6.8 with sodium bicarbonate (0.05 ml+0.01 ml saline/10 ml). Statistical analysis used one-way analysis of variance and the appropriate post hoc test for multiple comparisons. A P value less than 0.05 was considered significant. The onset of analgesia, the cephalad spread, and the incidence of hypotension did not differ between the groups. It is concluded that THAM does not affect the pharmacodynamics of 0.5% bupivacaine administered epidurally.

Concentration- and pH-dependent effects of local anesthetics on onset of epidural anesthesia.

This study was undertaken to determine the effect of concentration of pH-adjusted local anesthetics on the onset time of anesthesia.Lidocaine (0.9% and 1.8%) and bupivacaine (0.25% and 0.5%) were used. In the 0.9 percent lidocaine and 0.25 percent bupivacaine groups, the onset time of analgesia was shortened by about 100 and 200 seconds, when pH was adjusted to 7.4 and 7.0, respectively ( P < 0.05 and P < 0.01). In the 1.8 percent lidocaine and 0.5 percent bupivacaine groups, however, pH adjustment exerted no significant effect on the onset time. Alkalinization of low-concentration local anesthetics shortened the onset time, whereas that of high-concentration did not shorten.

The effect of pH-adjusted 2-chloroprocaine on the onset of epidural analgesia in pregnant patients in the lying and sitting position during the first stage of labor

The purpose of this prospective, randomized, double-blind study was to compare the epidural onset time of 2% 2-chloroprocaine with pH-adjusted 2-chloroprocaine administered in either the sitting or supine position in pregnant patients during the first stage of labor. Patients in Groups I and III received the control solution in the sitting and supine position, respectively. Patients in Groups II and IV received the buffered solution in the sitting and supine position, respectively. The pH and pCO 2 of the control and buffered solutions differed significantly. The pH and pCO 2 of the control and buffered solutions were 4.38 ± 0.01, 18.4 ± 2.2 mm Hg and 7.70 ± 0.04, 114.9 ± 3.0 mmHg, respectively. A statistically significant reduction in the time of onset of analgesia in the pH-adjusted groups was noted. Groups I and II had onset times of 4 ± 1.2 and 4.3 ± 1.0, whereas Groups II and IV had onset times of 2.6 ± 0.9 and 2.7 ± 0.6 min., respectively. There were no intergroup differences in the cephalad spread of analgesia or duration of analgesia. Position had no effect on the onset of analgesia at the S2–3 dermatomes nor on the bilateral cephalad spread of the epidural study solutions. Our results indicate that a pregnant patient may be dosed in the lateral supine position without adversely affecting the caudad or cephalad spread of plain or pH-adjusted 2% 2-chloroprocaine, which is clinically important because the incidence of aortocaval compression is increased in the supine position when compared with the lateral supine position. A 90-sec decrease in the onset time of analgesia when using buffered 2-chloroprocaine may not initially appear to be clinically important. However, in those patients who have had their epidural analgesia wear off for whatever reason, a faster onset of analgesia using buffered 2-chloroprocaine could be of benefit to both the mother and her fetus in cases in which an emergency forceps delivery has to be performed or imminent delivery of the baby is anticipated.

Incidence of Hypotension Associated with Epidural Anesthesia Using Alkalinized and Nonalkalinized Lidocaine for Cesarean Section

The onset of epidural anesthesia is accelerated by alkalinization of lidocaine with added epinephrine (LE). The possibility that decreases in systolic blood pressure (SBP) are also enhanced was studied in 21 patients having elective cesarean sections. Ten patients given LE + NaHCO3 (0.1 mEq/ml anesthetic solution) compared with 11 given LE alone had significantly (P less than 0.05) greater decreases in SBP (32% vs 19% from baseline values), as well as a greater rate of SBP decline to those minimum values (9%/min vs 3%/min, respectively). These differences were noted despite the fact that patients given LE + HCO3 received no less ephedrine and no more additional anesthetic than controls. Possible adverse effects of SBP reduction on uteroplacental blood flow suggest that caution be used in the use of alkalinized LE in obstetrical patients.

Incidence of Hypertension Associated with Epidural Anesthesia Using Alkalinized and Nonalkalinized Lidocaine for Cesarean Section

The onset of epidural anesthesia is accelerated by alkalinization of lidocaine with added epinephrine (LE). The possibility that decreases in systolic blood pressure (SBP) are also enhanced was studied in 21 patients having elective cesarean sections. Ten patients given LE + NaHCO3 (0.1 mEq/ml anesthetic solution) compared with 11 given LE alone had significantly (P less than 0.05) greater decreases in SBP (32% vs 19% from baseline values), as well as a greater rate of SBP decline to those minimum values (9%/min vs 3%/min, respectively). These differences were noted despite the fact that patients given LE + HCO3 received no less ephedrine and no more additional anesthetic than controls. Possible adverse effects of SBP reduction on uteroplacental blood flow suggest that caution be used in the use of alkalinized LE in obstetrical patients.

Delayed Onset of Epidural Anesthesia in Patients with Back Pain

Onset and completeness of anesthesia were compared in 15 patients with back pain or sciatica and in 10 patients without back pain given lumbar epidural anesthesia with 20 to 25 ml of 1.5% mepivacaine, 80 mg of methylprednisolone, and 1:200,000 epinephrine. Sensory block was complete within 30 minutes in patients without back pain. Eleven of 15 (73%) patients with back pain had delayed onset of anesthesia ranging from 35 to 95 minutes. The difference between the two groups was statistically significant (p less than 0.001). When there was a delay, the affected nerve roots were blocked 10 to 70 minutes after the contralateral unaffected roots. Differences in time of onset between affected nerves and contralateral nerves were also significant (p less than 0.01). The nerve roots involved, as determined from the myelogram or the electromyogram, or those adjacent to them, were the roots with delayed onset of block. Any effect of the steroid on nerve blockade was ruled out as there was solid anesthesia in patients without back pain.