Combined spinal-epidural anesthesia for outpatient surgery. Dose-response characteristics of intrathecal isobaric lidocaine using a 27-gauge Whitacre spinal needle

Spinal Anesthesia for Primary Hip and Knee Arthroplasty: Comparative Rates of Transient Neurological Symptoms and Urinary Retention using Lidocaine, Mepivacaine, and Bupivacaine

BACKGROUND

Short-acting spinal anesthetics enable rapid recovery hip and knee arthroplasty, however concerns with transient neurological symptoms (TNS) cause some to avoid using lidocaine. Post-operative urinary retention (POUR) is also a concern with spinal anesthesia. We sought to study the comparative rates of TNS and POUR between lidocaine, mepivacaine, and bupivacaine in a high-volume hip and knee arthroplasty setting.

METHODS

Data for 1,217 primary THA, TKA, and UKA cases were reviewed and grouped by spinal anesthetic agent (Lidocaine, Mepivacaine, or Bupivacaine). Of the 1,217 cases, utilization was 523 Lidocaine, 573 Mepivacaine, and 121 Bupivacaine. The incidence of TNS and POUR requiring catheterization was measured both by clinical evaluation as well as a questionnaire sent to patients 14 days postoperatively.

RESULTS

The overall rate of TNS was 8%. With the numbers available, there was no difference in rates of TNS between groups (6.9% Lidocaine, 9.2% Mepivacaine, and 4.1% Bupivacaine; P=0.297). There was no difference in rates of TNS or POUR between THA and TKA/UKA. Bupivacaine had a significantly higher rate of urinary retention (9.1%; P<0.001) than mepivacaine (2.8%) or lidocaine (1.5%).

CONCLUSIONS

This study showed no difference in the rate of TNS between the 3 common agents used in spinal anesthesia. Short-acting spinal anesthetics such as lidocaine and mepivacaine can lower the rate of POUR requiring catheterization helping to enable rapid recovery hip and knee arthroplasty.

Neuraxial anesthesia and bladder dysfunction in the perioperative period: a systematic review

PURPOSE

Urinary retention requiring catheterization carries the risk of infection. Neuraxial anesthesia causes transient impairment of bladder function ranging from delayed initiation of micturition to frank urinary retention. We undertook a review of the literature to determine the elements of neuraxial anesthesia and analgesia that prolong bladder dysfunction and increase the incidence of urinary retention.

METHODS

We performed a systematic search of the PubMed, MEDLINE, and EMBASE databases (from January 1980 to January 2011) to identify studies where neuraxial anesthesia and/or analgesia were employed and at least one of the following outcomes was reported: urinary retention, time to micturition, or post void residual. We included randomized controlled trials and observational studies published in the English language and we excluded case reports. The randomized trials were graded according to the Jadad score.

PRINCIPAL FINDINGS

Our search yielded 94 studies, and in 16 of these studies, the authors reported time to micturition after intrathecal anesthesia of varying local anesthetics and doses. Intrathecal injections were performed in 41 of these studies, epidural anesthesia/analgesia was used in 39 studies, and five studies involved both the intrathecal and epidural routes. Meta-analysis was not possible because of the heterogeneity of interventions and reported outcomes. The duration of detrusor dysfunction after intrathecal anesthesia is correlated with local anesthetic dose and potency. The incidence of urinary retention displays a similar trend and is further increased by the presence of neuraxial opioids, particularly long-acting variants. Urinary tract infection secondary to catheterization occurred rarely.

CONCLUSIONS

Neuraxial anesthesia/analgesia results in transient detrusor dysfunction. The duration of dysfunction depends on the potency and dose of medication used; however, it does not appear to result in significant morbidity.

[Spinal anaesthesia in day-case surgery. Optimisation of procedures]

BACKGROUND

Since prilocaine is being increasingly used for day case surgery as a short acting local anaesthetic for spinal anaesthesia and because of its low risk for transient neurological symptoms, we compared it to bupivacaine.

PATIENTS AND METHODS

Patients (n=88) who were scheduled for lower limb surgery with spinal anaesthesia randomly received 15 mg hyperbaric bupivacaine 0.5% or 60 mg hyperbaric prilocaine 2% (administered in a sitting position). Onset time, intensity, duration of the sensomotoric block, vital parameters and time of spontaneous miction were recorded and patients were questioned on satisfaction with the anaesthesia procedure and the occurrence of adverse side-effects after 24 h.

RESULTS

Bupivacaine caused a significantly higher sensory block than prilocaine (T6 vs. T8). Both groups were similar in reaching an analgesic level of at least T12, block intensity and onset times. Median analgesic levels at T12 were maintained for 60 min with prilocaine versus 120 min with bupivacaine, regression of the motor block was 135 min versus 210 min, sensory block S1 was 240 min versus 360 min, and time for spontaneous miction was 306 min versus 405 min, respectively (differences for all comparisons were statistically significant).

CONCLUSION

Under the present study conditions, hyperbaric prilocaine 2% was superior to hyperbaric bupivacaine 0.5% due to a shorter effect profile but otherwise equivalent quality of block. However, puncture in a sitting position and positioning with elevated torso for restriction of the cranial expansion of block spread might cause an enhanced sacral block with delayed recovery of bladder function.

The Median Effective Dose of Intrathecal Hyperbaric Bupivacaine Is Larger in the Single-Shot Spinal as Compared with the Combined Spinal-Epidural Technique

The combined spinal-epidural technique (CSE) has been associated with prolonged motor recovery and more frequent arterial hypotension as compared with a single-shot spinal (SSS) technique. We determined the median effective dose (MED) of intrathecal hyperbaric bupivacaine for CSE and SSS by using the up-down sequential allocation technique. Sixty male patients were randomly allocated to receive intrathecal administration through an SSS or CSE technique. Needle insertion occurred at the L3-4 interspace in all patients. In SSS, 9.5 mg of hyperbaric bupivacaine was administered through a 27-gauge Whitacre spinal needle. In CSE, a 17-gauge Tuohy needle with 4 mL of air was used to locate the epidural space, through which a 27-gauge Whitacre spinal needle was introduced and 7.0 mg of hyperbaric bupivacaine was administered. The dosing adjustment was 0.5 mg. A "successful" outcome was arbitrarily defined as sensory anesthesia at or above the T6 dermatome lasting for 60 min. A "success" resulted in a 0.5-mg decrement, whereas a "failure" resulted in a 0.5-mg increment in the next patient. There were 13 successes in both groups. The MED of bupivacaine was 9.18 mg (95% confidence interval, 8.89-9.47 mg) for CSE as compared with 11.37 mg (95% confidence interval, 10.88-11.86 mg) for SSS (P < 0.001). CSE required 19.3% (95% confidence interval, 14.9%-23.6%) less local anesthetic to achieve the defined clinical target. We found significant discrepancies in the MED of hyperbaric bupivacaine between the two techniques. Under similar clinical conditions, a 20% decrement in the dose of bupivacaine may be warranted whenever CSE is intended in place of SSS.

The combined spinal–epidural technique

In recent years, the use of regional anaesthesia techniques for surgery, obstetrics and post operative pain management have increased in popularity. The combined spinal-epidural (CSE) technique has attained widespread popularity for patients undergoing major surgery below the umbilicus who may require prolonged and effective postoperative analgesia. The CSE technique is now well established in several institutions. This chapter includes the clinical experience, advantages and potential problems, and discusses future perspectives of the CSE technique.

Spinal anaesthesia for outpatient surgery

Spinal anaesthesia in the outpatient is characterized by rapid onset and offset, easy administration, minimal expense, and minimal side effects or complications. Spinal anaesthesia offers advantages for outpatient lower extremity, perineal, and many abdominal and gynaecological procedures. Development of small-gauge, pencil-point needles are responsible for the success of outpatient spinal anaesthesia with acceptable rates (0-2%) of postdural puncture headache (PDPH). Compared with peripheral nerve blocks, spinal anaesthesia has a more predictable offset. There are many possible choices of local anaesthetics for outpatient spinal anaesthesia. These include lidocaine, prilocaine, mepivacaine and small doses of bupivacaine. Meperidine has local anaesthetic properties in addition to its opiate properties. It has been used as the sole intrathecal agent for spinal anaesthesia but has no real advantages over lidocaine. Mepivacaine and lidocaine have each been associated with transient neurological symptoms (TNS) following intrathecal administration. This has stimulated development of alternative agents, including combinations of local anaesthetics and opioids. Lidocaine remains the most useful agent for outpatient spinal anaesthesia. For longer procedures, mepivacaine is an excellent spinal anaesthetic agent. Attention to technique, reduction of dose and addition of fentanyl to lidocaine result in effective spinal anaesthesia with rapid recovery and a low incidence of significant side effects or complications.

Regional anesthesia for outpatient surgery

In summary, regional techniques offer significant advantages in the outpatient setting. They can avoid the side effects of nausea, vomiting, and pain that frequently delay discharge or cause admission. They can also provide prolonged analgesia as well as offer, with the use of continuous catheters, the promise of a pain-free perioperative period. The choice of drugs must be carefully adjusted, especially with neuraxial techniques. Despite frequently requiring some additional time at the outset, regional techniques have consistently been shown to provide competitive discharge times and costs when compared with general anesthesia. They deserve a prominent place in outpatient surgery.

A comparison of hyperbaric 1% and 3% solutions of small-dose lidocaine in spinal anesthesia

We examined whether the concentration of hyperbaric lidocaine affected the regression of motor block when the dose of lidocaine was kept constant at 30 mg. We also examined the spread, duration, and regression of sensory block. Sixty-five patients (ASA physical status I or II), scheduled for elective perineum or lower limb surgery, were enrolled in this study. Patients received spinal anesthesia with 1 mL of 3% lidocaine or 3 mL of 1% lidocaine. Adequate level of block was obtained for surgery in 63 of 65 patients. Whereas the administration of 3 mL of hyperbaric 1% lidocaine solution produced a level of sensory block similar to that produced by the administration of 1 mL of hyperbaric 3% lidocaine solution in spinal anesthesia, the administration of 3 mL of hyperbaric 1% lidocaine solution resulted in shorter times to full motor recovery and to urination and produced less motor block compared with 1 mL of hyperbaric 3% lidocaine solution. Two patients receiving 1% lidocaine and four patients receiving 3% lidocaine required IV ephedrine because of hypotension. Our results showed the clinical advantages of hyperbaric 1% lidocaine spinal anesthesia compared with hyperbaric 3% lidocaine spinal anesthesia for surgery of short duration.

IMPLICATIONS

When the dose of lidocaine was kept constant at 30 mg, hyperbaric 1% lidocaine solution resulted in shorter times for recovery from motor block and to urination than did hyperbaric 3% lidocaine solution. Levels of sensory block were similar. Therefore, the more dilute lidocaine for spinal anesthesia may be suitable for day-care surgery and short duration surgery.

Intrathecal anesthesia

PURPOSE OF REVIEW

Development of new drugs and special techniques, as well as changes in health care organization have markedly influenced the use of spinal block and its indications. The present review overviews recent developments in local anesthetic drugs, side effects and special techniques for intrathecal anesthesia.

RECENT FINDINGS

Severe complications after spinal anesthesia are acceptably rare. The cardiovascular effects associated with sympathetic block are more frequent but may successfully be treated with volume expansion and administration of vasoactive drugs while the multimodal approach to prevention of such side effects can also reduce the incidence. Based on recent magnetic resonance imaging studies the volume of cerebrospinal fluid at the lumbosacral level is the main determinant of the effects produced by intrathecal injection of local anesthetic solutions. Unfortunately, it is not possible to estimate the volume of cerebrospinal fluid at the lumbosacral region in clinical practice, but it is clear that the total dose of local anesthetic injected into the subarachnoid space is the primary determinant of both therapeutic and unwanted effects of spinal anesthesia. There is overwhelming evidence of the potential risk for neurological dysfunction associated with spinal lidocaine. This evidence is even more relevant in outpatients, in whom lidocaine is primarily indicated. On the other hand, several studies have demonstrated the efficacy and safety of using small doses of long-acting agents, such as bupivacaine or ropivacaine, to produce a short spinal block. The addition of small doses of opioids further helps to minimize the dose of local anesthetic solution required, without affecting the recovery profile from spinal block. The extensive use of pencil-point designs for spinal needles, and the availability of needles of very small size have allowed a significant reduction in the incidence of postdural puncture headache.

SUMMARY

The changes in health care organization observed during the past few years have forced us to change the indications for and clinical uses of intrathecal anesthesia techniques in accordance with the changing needs of surgery. The development of new drugs and special techniques for spinal anesthesia will further improve the clinical use of this old but trusted technique.

Spinal anaesthesia: local anaesthetics and adjuncts in the ambulatory setting

Intrathecal lidocaine remains a popular choice for ambulatory spinal anaesthesia due to its reliability, rapid onset and predictable rapid recovery profile. However, concerns with transient neurological symptoms (TNS) and their significant association with lidocaine have generated interest in alternative local anaesthetic agents to provide adequate spinal anaesthesia with the briefest possible recovery period. This chapter updates current data on drug dose-response relationships for local anaesthetics and the increasing use of intrathecal adjuncts to improve the anaesthetic and recovery profile for ambulatory spinal anaesthesia. Newer spinal anaesthetic techniques for common ambulatory procedures highlight the success of combining subclinical doses of local anaesthetics and intrathecal adjuncts. Controversies regarding the possible lower risk of TNS with newer spinal anaesthetic techniques and new discharge criteria are reviewed. The final section provides technical pearls to optimize ambulatory spinal anaesthetic outcomes.

Regional anesthesia in ambulatory surgery

Regional anesthesia is an attractive alternative for many ambulatory cases due to excellent postoperative pain relief and potential of speeding up the process from the OR to discharge. Regional anesthesia may be practised successfully in a busy ambulatory unit with a dedicated and simple regimen.

The use of bupivacaine and fentanyl for spinal anesthesia for urologic surgery

We evaluated the effect of 25 microg of fentanyl added to bupivacaine on sensory and motor block. By using a double-blinded study design, 80 men undergoing urologic surgery were randomized into the following four groups: Group I, bupivacaine 10 mg; Group II, bupivacaine 10 mg + fentanyl 25 microg; Group III, bupivacaine 7.5 mg + fentanyl 25 microg; Group IV, bupivacaine 5 mg + fentanyl 25 microg. The final volume of intrathecal injectate was adjusted to 2. 5 mL with sterile distilled water. Spinal anesthesia was administered with the 27-gauge Whitacre needle at the L2-3 interspace with the patient in the sitting position. Neural block was assessed by using pinprick and a modified Bromage scale. The degree of motor block was more profound in Group II compared with Group I at the end of operation. In Group IV, there was no motor block at the end of operation in any of the patients. The median level of the upper limit of the sensory block was higher than T(7) in all groups before the start of surgery. The addition of 25 microg of fentanyl to 5 mg of bupivacaine resulted in short-acting motor block. When 25 microg of fentanyl was added to 10 mg of bupivacaine, it increased the intensity and duration of motor block. Only 5 (6. 3%) of the patients needed supplemental analgesia during the operation. ¿abs¿

A comparison of spinal, epidural, and general anesthesia for outpatient knee arthroscopy

We compared general, epidural, and spinal anesthesia for outpatient knee arthroscopy (excluding anterior cruciate ligament repairs). Forty-eight patients (ASA physical status I-III) were randomized to receive either propofol-nitrous oxide general anesthesia with a laryngeal mask airway with anesthetic depth titrated to a bispectral index level of 40-60, 15-20 mL of 3% 2-chloroprocaine epidural, or 75 mg of subarachnoid procaine with 20 microg fentanyl. All patients were premedicated with <0.035 mg/kg midazolam and <1 microg/kg fentanyl and received intraarticular bupivacaine and 15-30 mg of IV ketorolac during the procedure. Recovery times, operating room turnover times, and patient satisfaction were recorded by an observer using an objective scale for recovery assessment and a verbal rating scale for satisfaction. Statistical analysis was performed with analysis of variance and chi(2). Postanesthesia care unit discharge times for the general and epidural groups were similar (general = 104+/-31 min, epidural = 92+/-18 min), whereas the spinal group had a longer recovery time (146+/-52 min) (P = 0.0003). Patient satisfaction was equally good in all three groups (P = 0.34). Room turnover times did not differ among groups (P = 0.16). There were no anesthetic failures or serious adverse events in any group. Pruritus was more frequent in the spinal group (7 of 16 required treatment) than in the general or epidural groups (no pruritus) (P<0.001). We conclude that epidural anesthesia with 2-chloroprocaine provides comparable recovery and discharge times to general anesthesia provided with propofol and nitrous oxide. Spinal anesthesia with procaine and fentanyl is an effective alternative and is associated with a longer discharge time and increased side effects.

IMPLICATIONS

For outpatient knee arthroscopy, anesthesia can be provided adequately with regional or general anesthesia. Epidural and general anesthesia provide equal recovery times and patient satisfaction, whereas spinal anesthesia may prolong recovery and have increased side effects. The choice of anesthesia may depend primarily on the patient's interest in being alert or asleep during the procedure.

The anesthetic and recovery profile of two doses (60 and 80 mg) of plain mepivacaine for ambulatory spinal anesthesia

Reports of transient neurological symptoms with the use of subarachnoid lidocaine has generated interest in alternate local anesthetics of intermediate duration, such as mepivacaine. This prospective randomized, double-blinded, dose-response study examined the anesthetic and recovery profiles of 60- and 80-mg doses of preservative-free plain mepivacaine for ambulatory spinal anesthesia. Sixty patients undergoing ambulatory anterior cruciate ligament repair of the knee under spinal anesthesia were randomized into two groups; Group 1 (29 patients) received 4 mL of 1.5% (60-mg dose) and Group 2 (31 patients) received 4 mL of 2% (80-mg dose) of plain mepivacaine. All patients received a combined spinal-epidural anesthetic technique. The epidural catheter was used only in the event the surgery outlasted the duration of surgical anesthesia with subarachnoid mepivacaine. Epidural supplementation was administered in three patients (12%) in Group 1 and one patient (3%) in Group 2 when the sensory block regressed to L-1 with surgery expected to last longer than 15 min. The cephalad dermatome level of the block and degree of motor block was comparable in the two groups. Times to two-segment and T-10 regression were comparable in the two groups (112 +/- 26 min in Group 1 versus 122 +/- 28 min in Group 2). Time to L-1 regression was significantly longer in Group 2 (146 +/- 28 min in Group 1 versus 159 +/- 19 min in Group 2). All of the ambulatory milestones were significantly faster in Group 1. Side effects, such as hypotension and emesis were negligible, severe bradycardia and urinary retention did not occur, and none of the patients in the two groups reported transient neurological symptoms over 24 h. In conclusion, plain mepivacaine in a 60- or 80-mg dose is a suitable local anesthetic choice for ambulatory spinal anesthesia with respect to anesthetic, as well as recovery profiles.

IMPLICATIONS

We evaluated the anesthetic and recovery profiles of 60- and 80-mg doses of plain mepivacaine for ambulatory spinal anesthesia. Both doses produced comparable sensory and motor block. Sensory and motor regression and ambulatory milestones were 20-30 min longer with the 80-mg dose. Side effects were negligible and transient neurological symptoms were not reported during a 24-h follow-up.

Potential neurotoxicity of spinal anesthesia with lidocaine

Spinal (intrathecal) anesthesia has evolved into a safe, widely accepted method of anesthesia with many advantages. However, the past decade has seen a large number of case reports and incidence studies that implicate the local anesthetic (LA) lidocaine as being more neurotoxic than other commonly used LAs such as bupivacaine and tetracaine, based on patterns of clinical use current at the time of those reports. Available studies suggest a risk of persistent lumbosacral neuropathy after spinal lidocaine by single injection in about 1 in 1300 procedures and a risk as high as about 1 in 200 after continuous spinal anesthesia with lidocaine. While uncommon, this risk is probably an order of magnitude higher than the risk reported for other commonly used LAs or for general anesthesia. Spinal lidocaine is also implicated in the syndrome of transient neurologic symptoms (previously referred to as transient radicular irritation), manifest by pain or dysesthesia in the buttocks or legs after recovery from anesthesia. Although the pain typically resolves within 1 week without lasting sequelae, it can be severe in up to one third of patients with the syndrome. In addition to clinical studies, both whole animal and in vitro studies have shown that lidocaine can be neurotoxic at clinically available concentrations and that lidocaine is more neurotoxic than equipotent concentrations of other commonly used LAs. The mechanism of this neurotoxicity may involve changes in cytoplasmic calcium homeostasis and mitochondrial membrane potential.

The combined spinal-epidural technique

Epidural and spinal blocks are well-accepted regional techniques, but they have several disadvantages. The CSE technique can reduce or eliminate the risks of these disadvantages. CSE block combines the rapidity, density, and reliability of the subarachnoid block with the flexibility of continuous epidural block to extend duration of analgesia. The CSE technique is used routinely at many institutions, particularly for major orthopedic surgery and in obstetrics. It has been used in tens of thousands of patients without any reports of major problems. Although at first sight the CSE technique appears to be more complicated than epidural or spinal block alone, intrathecal drug administration and siting of the epidural catheter are both enhanced by the combined, single-space, needle-through-needle method. Concerns about the epidural catheter entering the theca via the small puncture hole are now considered to be unfounded, but as with all epidural catheter techniques, vigilant monitoring of the patient during and after any injection is paramount. CSE is an effective way to reduce the total drug dosage required for anesthesia or analgesia. The intrathecal injection achieves rapid onset with minimal doses of local anesthetics and opioids, and the block can be prolonged with low-dose epidural maintenance administration. In addition, the sequential CSE method can be used to extend the dermatomal block with minimal additional drugs or even saline. Reduction in total drug dosage has made truly selective blockade possible. Many studies have confirmed that low-dose CSE with local anesthetic and opioid, or low-dose epidural block alone, will provide effective analgesia with minimal motor and proprioceptive block. Such neurologic selective blockade has made it possible for most patients to walk and bear down normally in labor or postoperatively. There remains concern about the risk of infection being increased when the CSE technique is used in place of epidural block alone. Despite a recent flurry of reports of meningitis with CSE procedures, there is no evidence the CSE block is more hazardous than epidural or subarachnoid block alone. Arguably, the single-space, needle-through-needle CSE technique will continue to improve with new needle designs and other advances to improve further the success rate and reduce complications, such as neurotrauma, PDPH, and infection. Over the past decade it has become clear that the CSE technique is a significant advance in regional blockade.

Combined spinal-epidural techniques

The combined spinal-epidural technique has been used increasingly over the last decade. Combined spinal-epidural may achieve rapid onset, profound regional blockade with the facility to modify or prolong the block. A variety of techniques and devices have been proposed. The technique cannot be considered simply as an isolated spinal block followed by an isolated epidural block as combining the techniques may alter each block. This review concentrates on technical and procedural aspects of combined spinal-epidural. Needle-through-needle, separate-needle and combined-needle techniques are described and modifications discussed. Failure rates and causes are reviewed. The problems of performing a spinal block before epidural blockade (potential for unrecognised placement of an epidural catheter, inability to detect paraesthesia during epidural placement, difficulty in testing the epidural, delay in positioning the patient) are described and evaluated. Problems of performing spinal block after epidural blockade (risk of catheter or spinal needle damage) are considered. Mechanisms of modification of spinal blockade by subsequent epidural drug administration are discussed. The review considers choice of technique, needle type, patient positioning and paramedian vs. midline approach. Finally, complications associated with combined spinal-epidural are reviewed.

The epidural "top-up" in combined spinal-epidural anesthesia: the effect of volume versus dose

The reinforcement of anesthesia by an epidural "top-up" in combined spinal-epidural anesthesia may be explained by a dual mechanism: a volume effect compressing the dural sac and a local anesthetic effect. The purpose of our study was to investigate the relative importance of each of these factors. Fifty patients scheduled for lower limb orthopedic surgery under combined spinal-epidural anesthesia were randomly allocated to one of five groups comprising 10 patients each. Using a needle-through-needle technique, all patients received a subarachnoid injection of 10 mg of plain bupivacaine and an epidural catheter. After the maximal level of sensory blockade as a result of the subarachnoid injection had been established, an epidural top-up was given according to the randomization code. Patients in Group 1 received 10 mL of bupivacaine 0.25%; patients in Group 2 received 10 mL of saline; patients in Group 3 received 5 mL of bupivacaine 0.5%; patients in Group 4 received 5 mL of saline; and patients in Group 5 received no epidural top-up. The maximal level of sensory blockade was then assessed for an additional 30 min. In Groups 1-4, the maximal level of sensory blockade increased significantly, whereas there was no significant increase in Group 5. There was no significant difference in the increase in the maximal level of sensory blockade among Groups 1-4. We conclude that, under the conditions of our study, there is no difference between 5 and 10 mL with regard to the volume effect of an epidural top-up in combined spinal-epidural anesthesia and that to produce an additional local anesthetic effect with bupivacaine, the dose must be larger than 25 mg.

IMPLICATIONS

In combined spinal-epidural anesthesia, an epidural "top-up" may increase the maximal level of sensory blockade by means of a volume effect and a local anesthetic effect. In this study, volumes of 5 and 10 mL produced a similar increase, and 25 mg of bupivacaine was insufficient to produce an additional local anesthetic effect.

Postoperative pain control in ambulatory surgery

Optimizing postoperative pain control is the key to further advancement in the field of ambulatory anesthesia. The current situation in postoperative pain management indicates room for improvement, especially in the area of patient education and the development of individualized discharge analgesic packages. Multimodal analgesia provides superior analgesia with a lower side-effect profile. Preoperative administration of analgesia would decrease the intraoperative analgesic requirement, which may lead to a smooth and rapid recovery. Finally, new, portable analgesic delivery systems are under investigation and may prove to be the method of choice for future postoperative pain, management in ambulatory anesthesia.

Impact of new guidelines on physicians' ordering of preoperative tests

OBJECTIVE

To compare the number of preoperative tests ordered for elective ambulatory surgery patients during the 2 years before and the 2 years after the establishment of new hospital testing guidelines.

MEASUREMENTS

The patterns of preoperative testing by surgeons and a medical consultant during the 2 years before and the 2 years after the establishment of new guidelines at one orthopedic hospital were reviewed. All tests ordered preoperatively were determined by review of medical records. Preoperative medical histories, physical examinations, and comorbidities were obtained according to a protocol by the medical consultant (author). Perioperative complications were determined by review of intraoperative and postoperative events, which also were recorded according to a protocol.

MAIN RESULTS

A total of 640 patients were enrolled, 361 before and 279 after the new guidelines. The mean number of tests decreased from 8.0 before to 5.6 after the new guidelines ( p =.0001) and the percentage decrease for individual tests varied from 23% to 44%. Except for patients with more comorbidity and patients receiving general anesthesia, there were decreases across all patient groups. In multivariate analyses only time of surgery (before or after new guidelines), age, and type of surgery remained statistically significant ( p =.0001 for all comparisons). Despite decreases in surgeons' ordering of tests, the medical consultant did not order more tests after the new guidelines ( p =.60) The majority of patients had no untoward events intraoperatively and postoperatively throughout the study period, with only 6% overall requiring admission to the hospital after surgery, mainly for reasons not related to abnormal tests. Savings from charges totaled $34,000 for the patients in the study.

CONCLUSIONS

Although there was variable compliance among physicians, new hospital guidelines were effective in reducing preoperative testing and did not result in increases in untoward perioperative events or in test ordering by the medical consultant.

Advances in regional anaesthesia and pain management

Advances in regional anaesthesia to date have made it one of the safest modalities for surgical anaesthesia and pain management. Continued refinement and development of new block techniques and approaches enhance the potential for block success, rapid postoperative recovery and patient safety. This will benefit both patient care and the health care economy.

Comparison of continuous spinal with combined spinal-epidural anesthesia using plain bupivacaine 0.5% in trauma patients

We investigated the efficacy and complications of microcatheter spinal anesthesia (CSA) in comparison to a combined spinal-epidural technique (CSE) using plain bupivacaine 0.5%. Sixty trauma patients randomly received either CSA using a 22-gauge Sprotte needle and a 28-gauge microcatheter or CSE after insertion of a 22-gauge epidural catheter through an 18-gauge Tuohy needle followed by dural puncture with a 25-gauge pencil-point needle inserted through the backeye of the Tuohy needle. An initial subarachnoid bolus of 2 mL of plain bupivacaine 0.5% was injected. If analgesia did not reach T12 within 20 min, supplemental bupivacaine was injected either intrathecally or epidurally up to a maximum of 5 mL in the CSA group or 16 mL in the CSE group. Mean arterial blood pressure, heart rate, and analgesic levels were recorded. On postoperative Day 4, patients were interviewed for postanesthetic complaints. Technical problems were more frequent in the CSE group than in the CSA group (47% vs 13%). Performance of anesthesia was faster (8 +/- 3 vs 15 +/- 8 min) and the total dose of bupivacaine lower (3.2 +/- 1.0 vs 9.7 +/- 5 mL) in patients who received CSA. The incidence of hypotension did not differ significantly. However, more patients in the CSE group were treated for bradycardia (4 vs 0). The number of patients suffering from postdural puncture headache was comparable in both groups, but there were more patients with lower back pain in the CSE group (8 vs 2). In conclusion, our data suggest that microcatheter CSA is not associated with an increased rate of complication in patients with lower limb fractures.

The efficacy of epinephrine test doses during spinal anesthesia in volunteers: implications for combined spinal-epidural anesthesia

Epinephrine test doses may be administered during combined spinal-epidural anesthesia to determine intravascular placement of epidural catheters. This study was designed to determine systolic blood pressure (SBP) and heart rate (HR) responses to intravenous injection of epinephrine (15 microg) during spinal anesthesia. Twelve volunteers received three spinal anesthetics (lidocaine 100 mg, tetracaine 15 mg, and bupivacaine 15 mg) in a randomized, double blind, cross-over fashion. Epinephrine was administered prior to spinal anesthesia (control), 30 min after injection of spinal anesthesia, and at regression of sensory block to T-10. SBP was measured with a radial arterial catheter and HR with an electrocardiogram. Positive responses were defined as peak increase in SBP > or = 15 mm Hg or HR > or = 20 bpm after injection of epinephrine. Compared with control, peak SBP responses decreased by a mean of 12 mm Hg during spinal anesthesia with tetracaine and bupivacaine (P < 0.05). Peak HR responses decreased by 11 bpm during all three spinal anesthetics (P < 0.05). Incidences of detection of intravenous injection by positive SBP and HR responses ranged from 50% to 100% and were not significantly affected by spinal anesthesia. Spinal anesthesia reduces hemodynamic responses to intravenous epinephrine injection but is unlikely to reduce detection by positive SBP and HR criteria.

A comparison of three regional anaesthesia techniques for outpatient knee arthroscopy

PURPOSE

The purpose of this study was to compare intraoperative conditions and postoperative pain control of three peripheral regional anaesthesia techniques for outpatient knee arthroscopic procedures.

METHODS

Sixty patients were randomized to one of three groups. Group 1A received portal injections (10 ml lidocaine 1%), intraarticular lidocaine (20 ml CO2 lidocaine 2% with 1/200,000 adrenaline) and a placebo femoral nerve block (20 ml saline). Group FNB received a femoral 3-in-1 nerve block (20 ml chloroprocaine 2% with 1/200,000 adrenaline), placebo portal injections (10 ml saline) and placebo intraarticular saline (20 ml saline with 1/200,000 adrenaline). Group FNB + IA received a femoral 3-in-1 nerve block, intraarticular lidocaine and placebo portal injections. The following were assessed: intraoperative pain (10 cm VAS: 0 = no pain, 10 = extreme pain), surgical operating conditions (1 = excellent, 4 = unacceptable), intraoperative use of sedation and analgesia, time to discharge, patient satisfaction score (1 = very satisfied, 5 very unsatisfied) and postoperative analgesia. Data were analyzed using ANOVA, Kruskal-Wallis, and Chi-square tests as appropriate, P < 0.05 was considered significant.

RESULTS

There were no differences among the groups regarding any of the variables tested. Considerable post-operative pain (VAS > or = 5) was experienced by 20/54 (37%) patients.

CONCLUSION

Any of the three anaesthetic techniques tested provide reliable intraoperative patient and surgical conditions for outpatient knee arthroscopy. Patient discomfort postoperatively was considerable in all groups and requires further investigation.

Comparison of lidocaine and saline for epidural top-up during combined spinal-epidural anesthesia in volunteers

This study was designed to determine the efficacy of saline as an epidural top-up to prolong spinal anesthesia during combined spinal-epidural anesthesia (CSEA). Eight volunteers received three separate CSEAs with intrathecal lidocaine (50 mg). After two-segment regression, each subject received either a saline (10 mL), lidocaine 1.5% (10 mL), or control sham (0.5 mL saline) epidural injection in a randomized, double-blind, triple cross-over fashion. Sensory block was assessed by pinprick and tolerance to transcutaneous electrical stimulation (TES) equivalent to surgical stimulation at the knee and ankle. Motor strength was assessed with iso-metric force dynamometry. Data were analyzed with a repeated measures analysis of variance and a paired t-test. Sensory block to pinprick was prolonged in the thoracolumbar dermatomes only by lidocaine (P < 0.05). Neither lidocaine nor saline prolonged the duration of tolerance to TES at the tested sites. Instead, saline decreased the duration of tolerance to TES by 20 and 24 min at the knee and ankle (P < 0.05). Recovery from motor block at the quadriceps was prolonged by an epidural injection of lidocaine (P < 0.05). We conclude that when 10 mL of epidural saline is administered after two-segment regression, it is an ineffective top-up and may decrease the duration of spinal anesthesia during CSEA.

The direction of the Whitacre needle aperture affects the extent and duration of isobaric spinal anesthesia

The use of Whitacre spinal needles results in directional flow out of the needle aperture, diverting local anesthetic from the longitudinal axis of the needle. Thus, a change in orientation of the needle aperture would be expected to result in a different local anesthetic distribution in the subarachnoid space. We studied 40 outpatients undergoing elective knee arthroscopy under spinal anesthesia with 60 mg plain lidocaine 2% in a prospective, double-blinded manner. Patients were randomly assigned to either Group I (needle aperture oriented in a cephalad direction throughout intrathecal injection) or Group II (aperture directed caudally). Onset and offset of sensory and motor block were analyzed at frequent intervals. Times to completion of ambulatory milestones, including discharge, were recorded. Group I was characterized by a higher sensory level (T 3.4 +/- 1.3 vs T 6.6 +/- 2.8, P < 0.001). Group I had significantly shorter duration of lumbar sensory anesthesia (149.2 +/- 30.6 min vs 177.8 +/- 23.5 min, P < 0.01) and motor blockade (117.6 +/- 26.1 min vs 150.0 +/- 22.8 min, P < 0.001). Mean time to outpatient discharge was approximately 32 min shorter in Group I. The orientation of the Whitacre needle aperture exerts a major influence on sensory level, as well as the duration of isobaric lidocaine spinal anesthesia.