Spinal anesthesia with tetracaine--effect of added vasoconstrictors

The effect of adding 0.2 ml of 1:1000 epinephrine or 0.5 ml of 1% phenylephrine to 1.5 ml of 1% tetracaine for spinal anesthesia was assessed in 30 patients in a double-blind study. Phenylephrine but not epinephrine produced a significant prolongation of sensory loss in the T12 dermatome. Both vasoconstrictors produced a significant prolongation of the total duration of sensory and motor blockade. These findings differ from those in previous studies in which lidocaine and bupivacaine were used.     

Epinephrine increases the effectiveness of tetracaine spinal anesthesia

The effect of epinephrine on the need for supplementation of spinal anesthesia produced with hyperbaric tetracaine was assessed in 60 patients undergoing transurethral resection of the prostate. Patients were randomly assigned to receive either 6 mg tetracaine alone (n = 20), 6 mg tetracaine with 0.2 mg epinephrine (n = 20), 10 mg tetracaine alone (n = 10), or 10 mg tetracaine with 0.2 mg epinephrine (n = 10). Observers were blinded to the presence or absence of epinephrine. Sensory level of anesthesia was assessed by pin prick, and surgery did not start until the level reached T10. Anesthesia was considered successful if the patient had no pain at the operative site. The success rate of low-dose tetracaine (6 mg) with epinephrine was 95% compared with 65% in patients receiving low-dose tetracaine alone (P = 0.04). All patients receiving 10 mg had successful anesthesia. Compared with patients receiving 6 mg tetracaine, those given 10 mg had higher dermatomal levels of anesthesia (P = 0.0001) and a higher incidence of nausea (P = 0.04). Thus, epinephrine can increase the effectiveness of low-dose tetracaine.     

Prolongation of lidocaine spinal anesthesia with epinephrine and phenylephrine

The effect of vasoconstrictors on the duration of lidocaine spinal anesthesia is controversial. We conducted a double-blind study of 28 neurologically normal ASA Class I or II patients to determine the effect of vasoconstrictors (epinephrine and phenylephrine) on the duration of lidocaine spinal anesthesia. The patients were randomized into three groups. All patients received 1.2 mg lidocaine per inch body height, mixed with 0.5 ml of test solution. Group 1 patients received lidocaine plus 0.5 ml normal saline; Group 2 patients received lidocaine plus 0.3 mg epinephrine; Group 3 patients received lidocaine plus 5 mg phenylephrine. Segmental sensory blockade was assessed by pinprick at 2-min intervals for the first 20 min and then every 5 min thereafter. Mean highest level was between T-2 and T-3 for all 3 groups. Time from injection to highest sensory level was similar in Groups 1 and 3, 11.6 +/- 3.57 and 12.0 +/- 5.10 min, respectively, but was significantly prolonged in Group 2, 18.1 +/- 4.33 min. Time for regression by two sensory dermatomes were significantly prolonged in both Groups 2 and 3, 102.9 +/- 18.1 and 105.7 +/- 33.1 min, respectively, compared to 78.1 +/- 12.6 min in Group 1. Times for regression to T-12 was also significantly prolonged in both Groups 2 and 3, 153.7 +/- 27.6 and 156.8 +/- 26.7 min, respectively, compared to 117.71 +/- 10.0 min in Group 1. In the doses used in the present study, both epinephrine and phenylephrine significantly prolong the duration of lidocaine spinal anesthesia.     

Prolongation of tetracaine spinal anesthesia by oral clonidine.

The effects of oral clonidine on the duration of isobaric tetracaine spinal anesthesia were studied in 30 patients undergoing urologic procedures. All patients received 15 mg of tetracaine intrathecally in isobaric saline solution. Group 1 (n = 10) received 0.25 mg of oral triazolam; group 2 (n = 10) received 0.15 mg of oral clonidine; and group 3 (n = 10) received 0.25 mg of oral triazolam and 0.75 mg of intrathecal phenylephrine. In group 1, the times for two- and four-segment regression of the level of analgesia to pin-prick were 80 +/- 17 and 123 +/- 22 min, respectively (mean +/- SD). The corresponding values of those measurements were 170 +/- 27 and 273 +/- 48 min in group 2 and 175 +/- 34 and 273 +/- 68 min in group 3. All the regression times in groups 2 and 3 were significantly longer than those in group 1. Regression times were not different between groups 2 and 3. The authors conclude that prolongation of tetracaine sensory analgesia may be produced by premedication with 0.15 mg of oral clonidine. The prolongation is similar to that produced by intrathecal phenylephrine.     

Clonidine prolongs canine tetracaine spinal anaesthesia

Using a randomized blind cross-over design, the comparative efficacy of clonidine in prolonging tetracaine spinal anaesthesia was studied in six mongrel dogs. Lumbar subarachnoid injections (1 ml) of: tetracaine 4 mg with clonidine 150 micrograms, tetracaine 4 mg with epinephrine 200 micrograms, tetracaine 4 mg, clonidine 150 micrograms, epinephrine 200 micrograms, and five per cent dextrose in H2O (vehicle) were administered randomly to each animal at 5-7 day intervals. Subarachnoid tetracaine produced a motor blockade of 186 +/- 58 (mean +/- SEM) min. Both clonidine and epinephrine produced a similar prolongation of tetracaine motor blockade, 135 per cent (p less than 0.01) and 116 per cent (p less than 0.05) respectively, compared with tetracaine alone. No motor blockade was observed in dogs receiving clonidine, epinephrine or five per cent dextrose in H2O. The addition of clonidine to tetracaine spinal anaesthesia produced a significant increase in duration of sensory blockade, 56 per cent (p less than 0.01) and 107 per cent (p less than 0.01) respectively, when compared to tetracaine with and without epinephrine. Subarachnoid clonidine alone produced a sensory blockade of 76 +/- 17 minutes, while only one animal receiving subarachnoid epinephrine had a sensory blockade (40 minutes). No neurologic deficits were observed in any of the animals. The study concludes that during spinal anaesthesia with tetracaine in dogs, clonidine is as effective as epinephrine in prolonging motor blockade, but is more effective in prolonging sensory blockade.     

The clinical use of small-dose tetracaine spinal anesthesia for transurethral prostatectomy

In a double-blinded study, we compared conventional dose tetracaine (8 mg), small-dose tetracaine (4 mg) with added fentanyl and epinephrine, and small-dose tetracaine (4 mg) with added fentanyl subarachnoid anesthesia. Forty-five patients scheduled for transurethral resection of prostate (TURP) under subarachnoid anesthesia were randomly assigned to Group 1 (8 mg hyperbaric tetracaine), Group 2 (4 mg hyperbaric tetracaine, 10 microg fen-tanyl, and 0.2 mg epinephrine), and Group 3 (4 mg hyperbaric tetracaine, 10 microg fentanyl, and 0.2 mL saline). Evaluations were performed after spinal anesthesia. Subarachnoid block was successful in all patients except one in Group 1, who required general anesthesia by mask. The median peak sensory levels 10 min after the induction of spinal anesthesia in Group 1 was T8, which was significantly higher than Group 2 and Group 3 (P < 0.05). The time of sensory and motor recovery in Group 3 was less than in Groups 1 and 2 (P < 0.05). Hypotension was observed in four patients in Group 1 and none in Groups 2 and 3. We conclude that small-dose 4-mg hyperbaric tetracaine plus 10 microg fentanyl might provide adequate anesthesia and fewer side effects for TURP when compared with the conventional (8 mg) dose. IMPLICATIONS: Small-dose hyperbaric tetracaine (4 mg with 10 microg fentanyl added) may provide adequate anesthesia and fewer side effects for transurethral resection of the prostate.     

Modification of local anesthetic toxicity by vasoconstrictors

We studied the effects of epinephrine or levonordefrin on the toxicity (convulsions) and lethality of four local anesthetics in mice. Appropriate doses of procaine, lidocaine, tetracaine or bupivacaine--either alone or in combination with 15 mcg/kg epinephrine or levonordefrin--were injected intravenously into the tail vein of male mice. Dose-response curves were constructed from the data obtained, and the CD50 and LD50 values for each local anesthetic alone and in combination with each of the vasoconstrictors were calculated by probit analysis. Both epinephrine and levonordefrin decreased the toxicity and lethality of procaine with respect to dose. Epinephrine, but not levonordefrin, increased the toxicity and lethality of bupivacaine as well as the lethality of tetracaine. Neither vasoconstrictor significantly affected the toxicity of lidocaine in mice but in rats epinephrine markedly increased lidocaine's lethality under identical conditions. Tight physical restraint decreased the LD50 values of all four local anesthetics and eliminated any modifying effect of the vasoconstrictor.     

Treatment of Hypotension after Hyperbaric Tetracaine Spinal Anesthesia: A Randomized, Double-blind, Cross-over Comparison of Phenylephrine and Epinephrine

Background: Despite many advantages, spinal anesthesia often is followed by undesirable decreases in blood pressure, for which the ideal treatment remains controversial. Because spinal anesthesia-induced sympathectomy and management with a pure alpha-adrenergic agonist can separately lead to bradycardia, the authors hypothesized that epinephrine, a mixed alpha- and beta-adrenergic agonist, would more effectively restore arterial blood pressure and cardiac output after spinal anesthesia than phenylephrine, a pure alpha-adrenergic agonist.

Methods: Using a prospective, double-blind, randomized, cross-over study design, 13 patients received sequential infusions of epinephrine and phenylephrine to manage hypotension after hyperbaric tetracaine (10 mg) spinal anesthesia. Blood pressure, heart rate, and stroke volume (measured by Doppler echocardiography using the transmitral time-velocity integral) were recorded at baseline, 5 min after injection of tetracaine, and before and after management of hypotension with epinephrine and phenylephrine. Cardiac output was calculated by multiplying stroke volume x heart rate.

Results: Five min after placement of a hyperbaric tetracaine spinal anesthesia, significant decrease in systolic (from 143 +/- 6 mmHg to 125 +/- 5 mmHg; P < 0.001), diastolic (from 81 +/- 3 to 71 +/- 3; P < 0.001), and mean (from 102 +/- 4 to 89 +/- 3; P < 0.001) arterial pressures occurred. Heart rate (75 +/- 4 beats/min to 76 +/- 4 beat/min; P = 0.9), stroke volume (115 +/- 17 to 113 +/- 13; P = 0.9), and cardiac output (8.0 +/- 1 l/m to 8.0 +/- 1 l/m; P = 0.8) did not change significantly after spinal anesthesia. Phenylephrine was effective at restoring systolic blood pressure after spinal anesthesia (120 +/- 6 mmHg to 144 +/- 5 mmHg; P <0.001) but was associated with a decrease in heart rate from 80 +/- 5 beats/min to 60 +/- 4 beats/min (P < 0.001) and in cardiac output from 8.6 +/- 0.7 l/m to 6.2 +/- 0.7 l/m (P < 0.003). Epinephrine was effective at restoring systolic blood pressure after spinal anesthesia (119 +/- 5 mmHg to 139 +/- 6 mmHg; P < 0.001) and was associated with an increase in stroke volume from 114 +/- 12 ml to 142 +/- 17 (P < 0.001) and cardiac output from 7.8 +/- 0.6 l/m to 10.8 +/- 1.1 l/m (P < 0.001).     

The effect of adjuvant epinephrine concentration on the vasoactivity of the local anesthetics bupivacaine and levobupivacaine in human skin

BACKGROUND AND OBJECTIVES: The recommended optimal concentration of adjuvant epinephrine for use with local infiltration anesthesia is usually 5 microg/mL. However, a lower dose might be as effective at prolonging the anesthetic effects, while limiting the risk of hazards associated with unintentional intravascular injection. The aim of our study was to determine the lowest effective vasoconstrictor concentration of epinephrine in human skin for a range of doses of bupivacaine and its less-vasodilatory S(-) isomer, levobupivacaine. METHODS: We injected combinations of 0.125%, 0.25%, and 0.75% bupivacaine and levobupivacaine with 1.25, 2.5, and 5 microg/mL epinephrine into the forearm skin of 10 healthy volunteers and measured the resulting blood flow changes over 1 hour using laser Doppler imaging. RESULTS: All 3 concentrations of epinephrine produced marked vasoconstriction, both alone and in combination with all 3 doses of the anesthetics ( P <.001 in all cases). There was almost no difference in effect between the 3 epinephrine concentrations. CONCLUSIONS: We conclude that 1.25 microg/mL epinephrine produces a comparable vasoconstrictor effect in human skin to that of higher concentrations when coinjected with clinical doses of bupivacaine and levobupivacaine and may be equally effective for infiltration anesthesia.     

Effect of injection rate on level and duration of hypobaric spinal anesthesia

The purpose of this study was to determine whether injection rate affects the spread of hypobaric spinal anesthesia. Hypobaric spinal anesthesia was performed on 20 patients for total hip arthroplasty. Dural puncture was performed with a 22-gauge Whitacre needle. All patients received 10 mg of hypobaric tetracaine with epinephrine. An electrically driven syringe pump was used to inject the anesthetic solution at either slow (250 sec) or fast (10 sec) rates. Ten patients received slow injections, and 10 received fast injections. Anesthetic levels, duration of anesthesia, and specific gravities of injectate and CSF were measured. Slow injection resulted in less spread of spinal anesthesia. Four-segment regression of anesthetic levels took significantly longer in the slow injection group. Local anesthetic mixtures used were consistently hypobaric compared to patient CSF. We conclude that slow injection of hypobaric tetracaine through a 22-gauge Whitacre needle produces lower levels of spinal anesthesia that tend to be of longer duration than levels resulting from fast injection.     

Dose-response relationship of clonidine in tetracaine spinal anesthesia

The study was undertaken to define a dose-response relationship for clonidine in prolonging canine tetracaine spinal anesthesia. Using a randomized blind cross-over design, six mongrel dogs were given subarachnoid injections (1 ml) of the following solutions over an 8-week period: tetracaine 4 mg (control), or tetracaine 4 mg with clonidine in doses of 10, 25, 50, 100, 150, 200, and 300 micrograms. With clonidine doses equal to or exceeding 50 micrograms/ml, motor and sensory blockade were significantly (P less than 0.01) prolonged, when compared to the control times. Analysis of data by second order polynomial regression analysis produced a relationship defined by Y = 23.241 + 1.104(x) - 0.0023(x2) with r2 = 0.92 and P less than 0.001 for sensory blockade and Y = 38.7072 + 1.64425(x) - 0.004125(x2) with r2 = 0.90 and P less than 0.005 for motor blockade. From these curves, a plateau in clonidine dose-response for both sensory blockade and motor blockade occurred at 150 micrograms. The increase in duration of spinal anesthesia with clonidine may be related to a direct post-synaptic alpha 2 adrenoceptor arteriolar effect, a spinal cord pre- or post-synaptic alpha 2 antinociceptive action or supraspinal alpha 2 modulation of nociception. No animals showed evidence of neurologic dysfunction during the study. The authors conclude that a well-defined dose-response relationship exists for clonidine in canine tetracaine spinal anesthesia.     

Spinal Cord and Cerebral Blood Flow Responses to Subarachnoid Injection of Local Anesthetics with and without Epinephrine

Subarachnoid anesthesia with lidocaine, mepivacaine, or tetracaine with and without added epinephrine (1:100 000) produced no demonstrable changes in average cerebral (CBF) or segmental spinal cord blood flow (SCBF) in 38 cats anesthetized with pentobarbital. Blood flow was measured by the injection of radioactive microspheres. Seven groups of cats received either lidocaine 15 mg, lidocaine 15 mg with epinephrine, mepivacaine 10 mg, mepivacaine 10 mg with epinephrine, tetracaine 5 mg, tetracaine 5 mg with epinephrine, or saline with epinephrine 1:100 000. Mean arterial pressure (MAP) decreased significantly (P less than 0.05) in Groups I-VI. Added epinephrine had no effect on the decrease in MAP. Amplitude of the somatosensory cortical evoked response decreased significantly in Groups I-VI, but did not change from control in Group VII. No significant change in CBF or SCBF was demonstrated in any group at any time. Plasma lidocaine and mepivacaine levels were significantly less at 5 min after subarachnoid injection in the groups receiving epinephrine compared to those not receiving epinephrine (P less than 0.05). The data appear to support the hypothesis of a vasoconstrictive reduction in systemic absorption of intrathecal local anesthetics, but suggest that significant segmental spinal cord ischemia does not occur. Maintenance of total flow in the face of a decrease in MAP suggests that autoregulation in brain and spinal cord may be maintained. Changes in regional SCBF or CBF may have been present but were not examined in this study. Further studies of brain and spinal cord blood flow dynamics, regional flow changes, and regulation of flow after intrathecal agents are necessary.     

Spinal anesthetic agents

Lidocaine, tetracaine, and bupivacaine are the local anesthetic agents most commonly employed for spinal anesthesia in the U.S. Lidocaine provides a short duration of anesthesia and is primarily useful for surgical and obstetrical procedures lasting less than one hour. Tetracaine and bupivacaine are used for procedures lasting 2 to 5 hours. Tetracaine appears to provide a somewhat longer duration of anesthesia and a more profound degree of motor block than does bupivacaine. On the other hand, compared with tetracaine, bupivacaine has been demonstrated to be associated with a decreased incidence of hypotension. In addition, bupivacaine may be better than tetracaine for use in orthopedic surgical procedures since it appears to be associated with a lower incidence of tourniquet pain. Vasoconstrictors can prolong the duration of spinal anesthesia of all three agents. However, the greatest duration is seen when vasoconstrictors are added to tetracaine solutions. Lidocaine and bupivacaine do not appear to benefit as much from the addition of vasoconstrictors. In general, the local anesthetic agents that are currently available for spinal anesthesia provide significant versatility. By carefully considering the planned surgical procedure, the surgeon's requirements, and the patient's characteristics (e.g., age, height, gravidity), and by understanding the factors that influence spinal anesthesia, the anesthesiologist can select a local anesthetic agent that will assure adequate and satisfying spinal anesthesia.     

Epinephrine does not prolong lidocaine spinal anesthesia in term parturients

The effect of adding epinephrine to spinal anesthesia performed with lidocaine in young, healthy patients was determined in a prospective, controlled, randomized double-blind study. Patients were randomly assigned to one of two groups. One group received lidocaine in dextrose, and the other, lidocaine in dextrose plus epinephrine. Maximum segmental level, time to maximum level, and duration as determined by time to two-segment regression were determined for each of the two groups. There were no significant differences between the two groups in any of the observed parameters, most notably, duration. The present results substantiate those from a previous study in an older population that showed that epinephrine did not significantly prolong lidocaine spinal anesthesia. The present results do not, however, support the hypothesis based upon these earlier data that failure of epinephrine to prolong lidocaine spinal anesthesia is restricted to elderly patients.     

Effect of volume on spinal anesthesia level with hyperbaric tetracaine.

The purpose of this prospective, randomized, double-blind study was to determine if the volume of a fixed milligram dose of hyperbaric tetracaine hydrochloride injected into the subarachnoid space affected the average maximal dermatomal spread of sensory anesthesia, determined by pinprick testing. One hundred two adults received spinal hyperbaric tetracaine in a volume of 2 mL, 3 mL, or 4 mL with the dose based on the patient's height. The addition of 0.2 mg of epinephrine to the anesthetic solution was allowed at the discretion of the attending anesthesiologist. A two-way analysis of variance (ANOVA) demonstrated that neither the dose selected nor the use of epinephrine affected anesthetic spread. ANOVA showed that anesthetic volume insignificantly affects the spread of sensory anesthesia. A Tukey HSD multiple comparisons test demonstrated a mean difference greater than 1 sensory dermatome between volumes of 2 mL and 4 mL, which was clinically detectable but statistically insignificant. Increasing the volume of hyperbaric spinal tetracaine solutions to improve anesthetic spread is unjustified.     

The addition of epinephrine to tetracaine injected intrathecally sustains an increase in glutamate concentrations in the cerebrospinal fluid and worsens neuronal injury

We have reported that large concentrations of intrathecal tetracaine increase glutamate concentrations in the cerebrospinal fluid (CSF) and cause neuronal injury in the spinal cord. In this study, we investigated whether the addition of epinephrine to tetracaine modulates these events. New Zealand white rabbits were assigned into five groups (six rabbits in each group) and intrathecally received 0.3 mL of epinephrine 0.1 mg/mL in NaCl solution (control), 1% tetracaine dissolved in saline (1%T), 1% tetracaine with epinephrine (1%TE), 2% tetracaine (2%T), or 2% tetracaine with epinephrine (2%TE). Glutamate concentrations in the lumbar CSF were monitored by microdialysis. Neurologic and histopathologic assessments were performed 1 wk after the administration. Glutamate concentrations significantly increased in all four groups that received tetracaine, whereas no change was observed in the Control group. The addition of epinephrine to tetracaine sustained large concentrations of glutamate. Sensory and motor dysfunction was observed in the 1%TE, 2%T, and 2%TE groups, and the dysfunction tended to be progressively exacerbated in this order. Characteristic histologic changes in animals with sensory and motor dysfunction were vacuolation in the dorsal funiculus and chromatolytic damage of motor neurons. The vacuolation of the dorsal funiculus in the 1%TE group was significantly worse than in the 1%T group. These results suggest that the addition of epinephrine to tetracaine may increase its neurotoxicity, which may possibly be related to a sustained increase of glutamate concentrations in the CSF. IMPLICATIONS: Sustained increase of glutamate concentrations produced by the addition of epinephrine to intrathecal tetracaine can cause neuronal injury.     

The effects of lidocaine and adrenergic agonists on rat sciatic nerve and skeletal muscle blood flow in vivo

It has been proposed that epinephrine prolongs lidocaine nerve blockade duration by exerting a local vasoconstrictive effect on tissues at the injection site, slowing lidocaine's local clearance. However, previous studies have failed to demonstrate consistent effects of lidocaine and epinephrine, injected alone and in combination, on vascular tone or regional blood flow. To reinvestigate this idea, in this study we used the radiolabeled microsphere technique to measure in vivo tissue blood flow before and at several time points after perisciatic nerve and intramasseter muscle injection of lidocaine alone, epinephrine, the selective alpha(1)-adrenergic receptor agonist phenylephrine, or lidocaine combined with these adrenergic receptor agonists. Repeated-measures analyses of variance were used to assess significant changes in blood flow over time. Lidocaine (2, 10, and 20 mg/mL) and epinephrine (10 micro g/mL or 1:100,000) injected alone did not alter blood flow in sciatic nerve, perisciatic muscle, or masseter muscle. Injections of lidocaine (10 mg/mL) combined with epinephrine (10 micro g/mL) did not affect adjacent muscle blood flow but caused a mild reduction in sciatic nerve blood flow, which was significant 30 min after injection. However, phenylephrine (10 micro g/mL), a potent vasoconstrictor, combined with lidocaine (10 mg/mL) significantly reduced blood flow in all three tissues. Our findings suggest that mechanisms other than local vasoconstriction may contribute to the prolongation of lidocaine nerve blocks by epinephrine. IMPLICATIONS: Accepting that the microsphere technique may be limited in its sensitivity to detect small but clinically relevant changes in tissue blood flow, our findings suggest that mechanisms other than local vasoconstriction may contribute to the prolongation of lidocaine nerve blocks by epinephrine.     

Hypotension in spinal anesthesia: a comparison of isobaric tetracaine with epinephrine and isobaric bupivacaine without epinephrine

Two isobaric spinal anesthetic solutions (bupivacaine 0.5%/20 mg without epinephrine and tetracaine 0.5%/15 mg with 0.2 mg epinephrine) were compared in a double-blind study of 60 patients. Patients were injected while in the lateral recumbent position and were immediately turned supine and horizontal. Up to 30 min after injection, no differences were found between the groups regarding segmental level of analgesia, changes in heart rate, and onset to or maximum decrease in mean arterial pressure (MAP). No correlation was found between maximum decrease in MAP and level of analgesia. At time of maximum decrease in MAP (tetracaine group - 16.7 +/- 12.8% (mean + SEM), bupivacaine group -19.4 + 14.8%) the level of analgesia was significantly higher in the tetracaine group (T5-6) than in the bupivacaine group (T7-8). Hypotension occurred in five patients in the bupivacaine group and in six in the tetracaine group. Two patients in the tetracaine group (but none in the bupivacaine group) had bradycardia. Hypotension together with bradycardia was observed in one patient in the tetracaine group but in no patient in the bupivacaine group. Two patients in each group developed postlumbar puncture headache. The authors conclude that the choice of local anesthetic agent, by itself, is not the sole cause of hypotension seen with spinal anesthesia.     

Spinal 2-chloroprocaine: a dose-ranging study and the effect of added epinephrine

With the availability of preservative- and antioxidant-free 2-chloroprocaine (2-CP), there may be an acceptable short-acting alternative to lidocaine for spinal anesthesia. We examined the safety, dose-response characteristics, and effects of epinephrine with spinal 2-CP. Six volunteers per group were randomized to receive 30, 45, or 60 mg of spinal 2-CP with and without epinephrine. Intensity and duration of sensory and motor blockade were assessed. When 11 of the 18 volunteers complained of vague, nonspecific flu-like symptoms, breaking of the blind revealed that all spinal anesthetics associated with the flu-like symptoms contained epinephrine. There were no complaints of flu-like symptoms in the volunteers who received 2-CP without epinephrine. No further spinal anesthetics containing epinephrine were administered, resulting in 29 anesthetics (11 with epinephrine, 18 without epinephrine.) Plain 2-CP demonstrated a dose-dependent increase in peak block height and duration of effect at all variables except time to 2-segment regression and time to regression to T10. Time to complete sensory regression with plain 2-CP was 98 +/- 20, 116 +/- 15, and 132 +/- 23 min, respectively. 2-CP with epinephrine produced times to complete sensory regression of 153 +/- 25, 162 +/- 33, and 148 +/- 29 min, respectively. Preservative and antioxidant free 2-CP can be used effectively for spinal anesthesia in doses of 30-60 mg. Epinephrine is not recommended as an adjunct because of the frequent incidence of side effects. IMPLICATIONS: Hyperbaric spinal 2-chloroprocaine is effective and has an anesthetic profile appropriate for use in the surgical outpatient over the dose range of 30-60 mg without signs of transient neurologic symptoms. The addition of epinephrine is not recommended because of the frequent incidence of side effects.     

The Addition of Phenylephrine Contributes to the Development of Transient Neurologic Symptoms after Spinal Anesthesia with 0.5% Tetracaine

Background: Recent reports indicate that transient neurologic symptoms commonly occur after single-injection spinal anesthesia with lidocaine. Information regarding tetracaine has been limited to a single case report. In addition, little is known about the cause of these symptoms or the cofactors that affect their occurrence. The present study sought to determine whether the presence of phenylephrine or the concentration of glucose in the anesthetic solution affects the incidence of transient neurologic symptoms after spinal anesthesia with 0.5% tetracaine.

Methods: One-hundred sixty patients classified as American Society of Anesthesiologists physical status I or II who were scheduled for elective surgery on a lower limb or perineum were sequentially assigned to one of four equal groups to receive intrathecal 0.5% tetracaine in 7.5% or 0.75% glucose, with or without 0.125% phenylephrine. Patients were evaluated on postoperative day one for the presence of pain, dysesthesia, or both in the legs or buttocks by an investigator unaware of the drug given.

Results: Symptoms were present in 10 patients (12.5%) receiving a spinal anesthetic containing phenylephrine, but in only one patient (1.3%) receiving spinal anesthesia without phenylephrine. There was no significant difference in the incidence of symptoms between groups receiving 7.5% glucose and those receiving 0.75% glucose (8.8% and 5% of patients, respectively).