Spencer S. Liu

Effects of Perioperative Analgesic Technique on Rate of Recovery after Colon Surgery

Background Choice of perioperative analgesia may affect the rate of recovery of gastrointestinal function and thus duration and cost of hospitalization after colonic surgery.

The Neurotoxicity of Drugs Given Intrathecally (spinal)

Overall, most spinal drugs in clinical use have been poorly studied for spinal cord and nerve root toxicity. Laboratory studies indicate that all local anesthetics are neurotoxic in high concentrations and that lidocaine and tetracaine have neurotoxic potential in clinically used concentrations. However, spinal anesthesia (including lidocaine and tetracaine) has a long and enviable history of safety. Spinal analgesics such as morphine, fentanyl, sufentanil, clonidine, and neostigmine seem to have a low potential for neurotoxicity based on laboratory and extensive clinical use. Most antioxidants, preservatives, and excipients used in commercial formulations seem to have a low potential for neurotoxicity. In addition to summarizing current information, we hope that this review stimulates future research on spinal drugs to follow a systematic approach to determining potential neurotoxicity. Such an approach would examine histologic, physiologic, and behavioral testing in several species, followed by cautious histologic, physiologic, and clinical testing in human volunteers and patients with terminal cancer refractory to conventional therapy.

A comparison of regional versus general anesthesia for ambulatory anesthesia: a meta-analysis of randomized controlled trials.

Both regional anesthesia and general anesthesia have been proposed to provide optimal ambulatory anesthesia. We searched MEDLINE and other databases for randomized controlled trials comparing regional anesthesia and general anesthesia in ambulatory surgery patients for meta-analysis. Only major conduction blocks were considered to be regional anesthesia. Regional anesthesia was further separated into central neuraxial block and peripheral nerve block. Fifteen (1003 patients) and 7 (359 patients) trials for central neuraxial block and peripheral nerve block were included in the meta-analysis. Both central neuraxial block and peripheral nerve block were associated with increased induction time, reduced pain scores, and decreased need for postanesthesia care unit analgesics. However, central neuraxial block was not associated with decreased postanesthesia care unit bypass or time or reduced nausea despite reduced analgesics, and it was associated with a 35-min increase in total ambulatory surgery unit time. In contrast, peripheral nerve block was associated with decreased postanesthesia care unit need and decreased nausea but, again, not with decreased ambulatory surgery unit time. This meta-analysis indicates potential advantages for regional anesthesia, such as decreased postanesthesia care unit use, nausea, and postoperative pain. Although these factors have been proposed to reduce ambulatory surgery unit stay, neither central neuraxial block nor peripheral nerve block were associated with reduced ambulatory surgery unit time. Other factors, such as unsuitable discharge criteria and limitations of meta-analysis, may explain this discrepancy.

Standardized perioperative care protocols and reduced length of stay after colon surgery

BACKGROUND Recent studies have suggested that critical pathways and standard order sets decrease hospital length of stay and improve quality of care. A recently conducted prospective, randomized study at our institution found that patients undergoing elective colon resections had earlier return of bowel function if perioperative epidural anesthesia and analgesia were provided. All patients in the study were also placed on a standardized perioperative regimen. We hypothesized that the standardized perioperative protocol used in this study contributed to early return of bowel function and hospital discharge compared with similar patients managed off protocol. STUDY DESIGN To test this hypothesis, we performed a case-controlled study comparing the hospital courses of 36 study patients to 36 control patients undergoing colorectal surgery by the same surgeons during the same calendar year. The distribution of types of operations and anesthetic techniques was similar in both groups. RESULTS As dictated by the protocol, all study patients had their nasogastric tubes removed, were started on a low fat liquid diet, and ambulated in the first postoperative day. Nasogastric tubes were removed in control patients and study patients 2.2 +/- 0.9 (mean value +/- SD) and 1.0 +/- 0.0 days postoperatively, respectively. Control patients were started on an oral diet, usually clear liquids, an average of 2.9 +/- 1.1 days postoperatively, a specific liquid diet was started 1.0 day postoperatively in study patients (p < 0.001). Return of bowel function, as determined by bowel tones, flatus, and bowel movements, occurred approximately 1 day earlier in study patients. Study patients were discharged 1 day sooner than control patients. CONCLUSIONS Our results suggest that the return of bowel function and the length of stay of patients undergoing colon surgery are improved if patients are entered into a standardized protocol that eliminates variation in intraoperative and postoperative anesthesia and postoperative surgical care. We believe these results can be reproduced in routine clinical surgery by having a clearly outlined protocol for perioperative care similar to that used in this study.

Dose-response characteristics of spinal bupivacaine in volunteers : Clinical implications for ambulatory anesthesia

Background Small doses of bupivacaine may be a reasonable choice for spinal anesthesia for patients having ambulatory surgery. However, few dose‐response data are available to guide the selection of reasonable doses of bupivacaine for different ambulatory procedures. Methods Eight volunteers per group were randomized to receive 3.75, 7.5, or 11.25 mg of 0.75% bupivacaine with 8.25% dextrose in a double‐blind manner. Sensory block was assessed with pinprick, transcutaneous electrical stimulation equivalent to surgical incision at the ankle, knee, pubis, and umbilicus, and with duration of tolerance to pneumatic thigh tourniquet. Motor block at the quadriceps and gastrocnemius muscles was assessed with isometric force dynamometry. Times until recovery from spinal anesthesia were recorded. Dose‐response relationships were determined by linear regressions. Mean (95% confidence intervals) for durations of sensory and motor block per milligram of bupivacaine administered were calculated from linear regressions. Results Significant dose‐response relationships (P < 0.006) were determined for sensory block, motor block, and time until recovery (R from 0.6 to 0.9). Within the range of doses studied, each additional milligram of bupivacaine was associated with an increase in duration of tolerance to transcutaneous electrical stimulation of 10 (7 to 13) min, an increase in tolerance to tourniquet of 7 (2 to 11) min, an increase in duration of motor block of 8 (5 to 12) min, and an increase in time until recovery of 21 (17 to 25) min. Conclusions These dose‐response data may guide the selection of reasonable doses of bupivacaine for various outpatient procedures, although individual responses vary.

Fentanyl Prolongs Lidocaine Spinal Anesthesia Without Prolonging Recovery

Lidocaine spinal anesthesia is a popular anesthetic for short procedures due to its brief duration.The addition of fentanyl may improve the quality and duration of lidocaine spinal anesthesia. Eight volunteers received plain lidocaine 5% in dextrose (50 mg) both with and without 20 micro gram of fentanyl in a randomized, double-blind, cross-over fashion. Sensory analgesia was assessed with pinprick, cold, touch, transcutaneous electrical stimulation equivalent to surgical incision, and duration of tolerance of pneumatic thigh tourniquet. Motor block was assessed with isometric force dynamometry. Regression of pinprick, touch, and cold was prolonged with fentanyl. Duration of tolerance of electrical stimulation at the umbilicus, hip, knee, and ankle was increased with fentanyl (181% increase from plain lidocaine on average; P < 0.01). Duration of tolerance of tourniquet-induced pain was increased by an average of 48% with addition of fentanyl (P = 0.02). Neither motor block nor time to void was prolonged with fentanyl. Pruritus occurred in all subjects receiving fentanyl but was treated easily and were well tolerated. We recommend the addition of 20 micro gram of fentanyl to lidocaine spinal anesthesia as a means to improve duration of sensory anesthesia without prolonging recovery of motor function or time to micturition. (Anesth Analg 1995;80:730-4)

Sedation during Spinal anesthesia

BACKGROUND Central neuraxial anesthesia has been reported to decrease the dose of both intravenous and inhalational anesthetics needed to reach a defined level of sedation. The mechanism behind this phenomenon is speculated to be decreased afferent stimulation of the reticular activating system. The authors performed a two-part study (nonrandomized pilot study and a subsequent randomized, double-blind, placebo-controlled study) using the Bispectral Index (BIS) monitor to quantify the degree of sedation in unmedicated volunteers undergoing spinal anesthesia. METHODS Twelve volunteers underwent BIS monitoring and observer sedation scoring (Observers Assessment of Alertness/Sedation Scale [OAA/S]) before and after spinal anesthesia with 50 mg hyperbaric lidocaine, 5%. Subsequently, 16 volunteers blinded to the study were randomized to receive spinal anesthesia with 50 mg hyperbaric lidocaine, 5% (n = 10) or placebo (n = 6) and underwent BIS and OAA/S monitoring. RESULTS In part I, significant changes in BIS scores of the volunteers occurred progressively (P = 0.003). The greatest variations from baseline BIS measurement occurred at 30 and 70 min. In part II, there were significant decreases in OAA/S and self-sedation scores for patients receiving spinal anesthesia versuscontrol patients (P = 0.04 and 0. 01, respectively). The greatest decrease in OAA/S scores occurred at 60 min. BIS scores were similar between groups (P = 0.4). CONCLUSIONS Spinal anesthesia is accompanied by significant sedation progressively when compared with controls as measured by OAA/S and self-sedation scores. This effect was not related to block height. The late sedation observed by OAA/S at 60 min may indicate a second mechanism of sedation, such as delayed rostral spread of local anesthetics. BIS was not a sensitive measure of the sedation associated with spinal anesthesia in the randomized, blinded portion of this study.

dilution of Spinal Lidocaine Does Not Alter the Incidence of Transient Neurologic Symptoms

BACKGROUND Although it has been suggested that the dilution of 5% hyperbaric lidocaine before injection for spinal anesthesia may decrease the incidence of transient neurologic symptoms, previous studies have not noted a decreased incidence between 5% and 2% lidocaine. The aim of the current study was to determine whether the incidence of transient neurologic symptoms could be altered by further diluting spinal lidocaine from 2.0% to 0.5%. METHODS One hundred nine patients with American Society of Anesthesiologists physical status 1 or 2 undergoing outpatient knee arthroscopy were randomized in a double-blind fashion to receive 50 mg hyperbaric spinal lidocaine as a 2.0%, 1.0%, or 0.5% concentration. On the third postoperative day, patients were contacted by a blinded investigator and questioned regarding the incidence of postoperative complications, including transient neurologic symptoms, defined as pain or dysthesia in one or both buttocks or legs occurring within 24 h of surgery. RESULTS The incidence of transient neurologic symptoms did not differ among patients receiving 2.0% (incidence of 15.8%), 1.0% (incidence of 22.2%), and 0.5% (incidence of 17.1%) lidocaine (P = 0.756). CONCLUSIONS For ambulatory patients undergoing arthroscopy, the incidence of transient neurologic symptoms is not reduced by decreasing spinal lidocaine concentrations from 2.0% to 1.0% or 0.5%. The incidences of transient neurologic symptoms with the 0.5%, 1.0%, and 2.0% solutions are similar to previously reported incidences for 5.0% lidocaine, suggesting that dilution of lidocaine from 5.0% to 0.5% does not change the incidence of these symptoms.

Quantitative analysis of respiratory, motor, and sensory function after supraclavicular block

The incidence and clinical significance of hemidiaphragmatic paresis after supraclavicular block of the brachial plexus is unknown.Eight healthy volunteers received a supraclavicular block with a standard technique using 30 mL of 1.5% lidocaine. Respiratory function was assessed with ultrasound of the diaphragm, respiratory inductive plethysmography (RIP), and pulmonary function tests (PFT) every 20 min. Sensory block was assessed with pinprick and motor block with isometric force dynamometry every 20 min. Four of eight subjects demonstrated hemidiaphragmatic paresis on both ultrasound and RIP. No subject experienced changes in PFT values or subjective symptoms of respiratory difficulty. Motor and sensory blockade outlasted hemidiaphragmatic paresis. These results are contrasted to the often symptomatic, 100% incidence of hemidiaphragmatic paresis seen after interscalene block. In this study of healthy volunteers, supraclavicular block was associated with a 50% incidence (95% confidence interval 14-86) of hemidiaphragmatic paresis that was not accompanied by clinical evidence of respiratory compromise. Implications: Interscalene block is always associated with diaphragmatic paralysis and respiratory compromise. The significance of these side effects after supraclavicular block is unknown. Using sensitive measures of respiratory function, we determined that diaphragmatic paralysis occurs less often with the supraclavicular approach and is not associated with respiratory difficulties in healthy subjects. (Anesth Analg 1998;86:1239-44)

Comparison of 5% with Dextrose, 1.5% with Dextrose, and 1.5% Dextrose-Free Lidocaine Solutions for Spinal Anesthesia in Human Volunteers

The use of lidocaine in concentrations less than 5% for spinal anesthesia may be advantageous but has not been carefully studied.Lidocaine 50 mg (1.5% with dextrose and 1.5% dextrose-free) was administered to eight volunteers in a randomized, double blind, cross-over fashion. All of these subjects had previously received 5% lidocaine with dextrose using the same experimental protocol. Sensory analgesia was assessed with pinprick, transcutaneous electrical stimulation (TES) equivalent to surgical incision, and duration of tolerance of pneumatic thigh tourniquet. Motor block was assessed with isometric force dynamometry. Peak dermatomal level was the highest and duration until regression of pinprick the longest with the 5% solution (P < 0.05). Duration of tolerance to TES was increased (33 +/- 10 min) with the 5% solution (P < 0.04). Duration of tolerance to tourniquet pain was increased (11 +/- 3 min) with the 5% solution (P < 0.02). Duration of motor block was increased (45 +/- 9 min) with the 5% and the 1.5% without dextrose solutions (P < 0.04). Time to void was increased (33 +/- 5 min) with the 5% solution (P < 0.03). In conclusion, the use of different solutions of lidocaine for spinal anesthesia results in significant differences in sensory and motor block and time until recovery of micturition. (Anesth Analg 1995;81:697-702)