Biomedical subjects
Publications and source records attributed to Spencer S Liu.
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STUDY OBJECTIVE: To examine the effects of plasma volume expansion on plasma volume, left ventricular end-diastolic volume (LVEDV), and cardiac index (CI) after rapid fluid infusion, as knowledge of the degree of concordance between plasma and cardiac preload expansion could optimize LVEDV expansion without administering excessive fluid. DESIGN: Randomized, double-blinded study. SETTING: Academic community hospital. PATIENTS: 20 patients undergoing elective coronary artery bypass surgery. INTERVENTIONS: Patients were administered either 5% albumin (5 mL/kg) or lactated Ringer's solution (25 mL/kg) over 30 minutes, just before incision. MEASUREMENTS: Serial measurements of plasma volume, LVEDV by transesophageal echocardiography, and CI were recorded. MAIN RESULTS: Albumin expanded plasma volume and LVEDV to a similar degree (11.3% and 13.2%). In contrast, lactated Ringer's solution increased plasma volume more than LVEDV (21.7% vs 14.4%; P = 0.0005). Increased LVEDV significantly but poorly correlated with increased CI (r(2) = 0.2, P < 0.0001) for both fluids. However, LVEDV expansion was brief and returned to baseline or less within 30 minutes for both fluids despite continued plasma volume expansion and increased CI. Correspondingly, rates of decline from peak expansion were significantly faster for LVEDV than plasma volume expansion for both albumin (-1.9% + 1.9%/min vs -0.1% + 0.1%/min; P = 0.0008) and lactated Ringer's (-1.1% + 0.8%/min vs -0.4% + 0.2%/min; P = 0.006). CONCLUSIONS: Intravenous fluids increased LVEDV to a lesser extent and duration than did plasma volume expansion. Monitoring of LVEDV was a poor guide for fluid administration to maximize CI.
Gender is believed to be an independent risk factor for the development of post-dural puncture headache, but there are some of the inconsistencies in the available data. This systematic review examined a total of 18 trials (2,163 males, 1,917 females). The odds of developing a post-dural puncture headache were significantly lower for male than nonpregnant female subjects (odds ratio = 0.55; 95% confidence interval, 0.44-0.67). Although the authors found that nonpregnant female subjects seem to have a higher incidence of post-dural puncture headache than males, the etiology behind these findings is not clear from the current meta-analysis.
Although most randomized clinical trials conclude that the addition of continuous peripheral nerve blockade (CPNB) decreases postoperative pain and opioid-related side effects when compared with opioids, studies have included relatively small numbers of patients and the majority failed to show statistical significance during all time periods for reduced pain or side effects. We identified studies primarily by searching Ovid Medline (1966-May 21, 2004) for terms related to postoperative analgesia with CPNB and opioids. Each article from the final search was reviewed and data were extracted from tables, text, or extrapolated from figures as needed. Nineteen articles, enrolling 603 patients, met all inclusion criteria. Inclusion criteria were a clearly defined anesthetic technique (combined general/regional anesthesia, general anesthesia alone, peripheral nerve block), randomized trial, adult patient population (> or =18 yr old), CPNB (or analgesia) used postoperatively (intrapleural catheters were deemed not to be classified as a peripheral nerve catheter), and opioids administered for postoperative analgesia in groups not receiving peripheral nerve block. Perineural analgesia provided better postoperative analgesia compared with opioids (P < 0.001). This effect was seen for all time periods measured for both mean visual analog scale and maximum visual analog scale at 24 h (P < 0.001), 48 h (P < 0.001), and 72 h (mean visual analog scale only) (P < 0.001) postoperatively. Perineural catheters provided superior analgesia to opioids for all catheter locations and time periods (P < 0.05). Nausea/vomiting, sedation, and pruritus all occurred more commonly with opioid analgesia (P < 0.001). A reduction in opioid use was noted with perineural analgesia (P < 0.001). CPNB analgesia, regardless of catheter location, provided superior postoperative analgesia and fewer opioid-related side effects when compared with opioid analgesia.
Total knee arthroplasty (TKA) may result in severe pain, and single-injection femoral nerve blocks (SFNB) have been demonstrated to have a limited duration of analgesia. Continuous femoral nerve blocks (CFNB) can prolong the analgesic duration of SFNB. We prospectively randomized 36 patients undergoing TKA to CFNB versus SFNB and evaluated the effect on hospital length of stay (LOS) as the primary outcome within a standardized clinical pathway. Secondary outcomes included visual analog scale (VAS) pain scores, opioid consumption, and long-term functional recovery at 12 wk. Mean VAS resting scores were significantly lower among patients who received CFNB versus SFNB: first day (1.7 vs 3.3 [P = 0.002]) and second day (0.9 vs 3.2 [P < 0.0001]) after surgery. Mean maximal VAS scores during physical therapy were significantly lower among patients who received CFNB versus SFNB: first day (4.7 vs 6.3 [P = 0.01]) and second day (3.9 vs 6.1 [P = 0.0005]) after surgery. Mean oxycodone consumption was significantly lower among patients who received CFNB versus SFNB: 15 mg versus 40 mg (P = or < 0.0001) on the first day after surgery; 20 mg versus 43 mg (P = 0.0004) on the second day after surgery. There was no difference in hospital LOS (3.8 vs 3.9 days) or long-term functional recovery (117 degrees versus 113 degrees knee flexion at 12 wk) between the two groups. The lack of effect provided by increased duration of analgesia (from CFNB) after TKA may now have minimal impact on hospital LOS and long-term functional recovery in the contemporary healthcare environment within the United States.
The authors performed a meta-analysis and found that epidural analgesia overall provided superior postoperative analgesia compared with intravenous patient-controlled analgesia. For all types of surgery and pain assessments, all forms of epidural analgesia (both continuous epidural infusion and patient-controlled epidural analgesia) provided significantly superior postoperative analgesia compared with intravenous patient-controlled analgesia, with the exception of hydrophilic opioid-only epidural regimens. Continuous epidural infusion provided statistically significantly superior analgesia versus patient-controlled epidural analgesia for overall pain, pain at rest, and pain with activity; however, patients receiving continuous epidural infusion had a significantly higher incidence of nausea-vomiting and motor block but lower incidence of pruritus. In summary, almost without exception, epidural analgesia, regardless of analgesic agent, epidural regimen, and type and time of pain assessment, provided superior postoperative analgesia compared to intravenous patient-controlled analgesia.
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.
BACKGROUND: Perioperative central neuraxial analgesia may improve outcome after coronary artery bypass surgery due to attenuation of stress response and superior analgesia. METHODS: MEDLINE and other databases were searched for randomized controlled trials in patients undergoing coronary artery bypass surgery with cardiopulmonary bypass who were randomized to either general anesthesia (GA) versus general anesthesia-thoracic epidural analgesia (TEA) or general anesthesia-intrathecal analgesia (IT). RESULTS: Fifteen trials enrolling 1178 patients were included for TEA analysis. TEA did not affect incidences of mortality (0.7% TEA vs. 0.3% GA) or myocardial infarction (2.3% TEA vs. 3.4% GA). TEA significantly reduced the risk of dysrhythmias with an odds ratio of 0.52, pulmonary complications with an odds ratio of 0.41, and time to tracheal extubation by 4.5 h and reduced analog pain scores at rest by 7.8 mm and with activity by 11.6 mm. Seventeen trials enrolling 668 patients were included for IT analysis. IT had no significant effect on incidences of mortality (0.3% IT vs. 0.6% GA), myocardial infarction (3.9% IT vs. 5.7% GA), dysrhythmias (24.8% vs. 29.1%), nausea/vomiting (31.3% vs. 28.5%), or time to tracheal extubation (10.4 h IT vs. 10.9 h GA). IT modestly decreased systemic morphine use by 11 mg and decreased pain scores by 16 mm. IT significantly increased the incidence of pruritus (10% vs. 2.5%). CONCLUSIONS: There were no differences in the rates of mortality or myocardial infarction after coronary artery bypass grafting with central neuraxial analgesia. There were associated improvements in faster time until tracheal extubation, decreased pulmonary complications and cardiac dysrhythmias, and reduced pain scores.
BACKGROUND: Ambulatory surgery is growing in popularity worldwide. For example, 50-70% of surgical procedures in North America are performed on an ambulatory basis. Use of Bispectral Index (BIS) monitoring for titration of general anesthesia may allow use of less anesthetics, reduction in side effects, and faster patient recovery. METHODS: MEDLINE and other databases were searched for randomized controlled trials examining the use of BIS monitoring versus standard practice in ambulatory surgery patients. Outcomes were extracted from these articles, and a meta-analysis was performed. RESULTS: One thousand three hundred eighty subjects from 11 trials were included in the meta-analysis. The use of BIS monitoring significantly reduced anesthetic consumption by 19%, reduced the incidence of nausea/vomiting (32% vs. 38%; odds ratio, 0.77), and reduced time in the recovery room by 4 min. However, these benefits did not result in significant reduction in time until patient discharge from the ambulatory surgery unit. Cost analysis using pooled costs to reflect North America, Europe, and Asia indicated that use of BIS monitoring increased the cost per patient by 5.55 US dollars because of the cost of BIS electrodes. CONCLUSIONS: The use of BIS monitoring modestly reduced anesthetic consumption, risk of nausea and vomiting, and recovery room time. These benefits did not reduce time spent in the ambulatory surgery unit, and cost of the BIS electrode exceeded any cost savings.
CONTEXT: Whether epidural analgesia is a better method than parenteral opioids for postoperative pain control remains controversial. OBJECTIVE: To systematically review the efficacy of postoperative epidural analgesia vs parenteral opioids, the primary alternative technique. DATA SOURCES: Studies were identified primarily by searching the National Library of Medicine's PubMed database (1966 to April 25, 2002) and other sources for studies related to postoperative epidural analgesia. STUDY SELECTION: Inclusion criteria were a comparison of epidural therapy vs parenteral opioids for postoperative analgesia, measurement of pain using a visual analog scale (VAS) or numeric rating scale, randomization of patients to either therapy, and adult patients (> or =18 years). A total of 1404 abstracts were identified, 100 of which met all inclusion criteria. DATA EXTRACTION: Each article was reviewed and data extracted from tables, text, or extrapolated from figures as needed. Weighted mean pain scores, weighted mean differences in pain score, and weighted incidences of complications were determined by using a fixed-effect model. DATA SYNTHESIS: Epidural analgesia provided better postoperative analgesia compared with parenteral opioids (mean [SE], 19.40 mm [0.17] vs 29.40 mm [0.20] on the VAS; P<.001). When analyzed by postoperative day, epidural analgesia was better than parenteral opioids on each postoperative day (P<.001 for each day after surgery). For all types of surgery and pain assessments, all forms of epidural analgesia provided significantly better postoperative analgesia compared with parenteral opioid analgesia (P<.001 for all), with the exception of thoracic epidural analgesia vs opioids for rest pain after thoracic surgery (weighted mean difference, 0.6 mm; 95% confidence interval, -0.3 to 1.5 mm; P =.12). The complication rates were lower than expected for nausea or vomiting and pruritus but comparable with existing data for lower extremity motor block. CONCLUSION: Epidural analgesia, regardless of analgesic agent, location of catheter placement, and type and time of pain assessment, provided better postoperative analgesia compared with parenteral opioids.
There are numerous physiological effects of spinal anaesthesia. This chapter focuses on the physiological effects that are of clinical relevance to the anaesthesiologist, and provides suggestions for successful management of this simple and popular technique. The mechanisms and clinical significance of spinal-anaesthesia-induced hypotension, bradycardia and cardiac arrest are reviewed. The increasing popularity of ambulatory spinal anaesthesia requires knowledge that long-acting local anaesthetics, such as bupivacaine, impair the ability to void far longer than short-acting local anaesthetics, such as lidocaine. The importance of thermoregulation during spinal anaesthesia, and the clinical consequences of spinal-anaesthesia-induced hypothermia are reviewed. Effects of spinal anaesthesia on ventilatory mechanics are also highlighted. Lastly, the sedative and minimum-alveolar-concentration-sparing effects of spinal anaesthesia are discussed to reinforce the need for the judicious use of sedation in the perioperative setting.
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STUDY OBJECTIVE: To compare the effects of ropivacaine-fentanyl patient-controlled epidural analgesia (PCEA) with morphine intravenous (IV) patient-controlled analgesia (PCA). DESIGN: Prospective, randomized, multicenter trial. SETTING: Five university-affiliated hospitals. PATIENTS: 41 patients undergoing colon surgery. INTERVENTION: Patients were randomized to receive either standardized combined epidural/general anesthesia followed by PCEA with ropivacaine 0.2% and fentanyl (2 microg/mL) or standardized general anesthesia followed by morphine IV PCA. All patients participated in a standardized postoperative clinical pathway. MEASUREMENTS AND MAIN RESULTS: Analgesia was assessed with visual analog scale (VAS) scores. Postoperative recovery was assessed by completion of prospectively defined discharge milestones and time until discharge. Statistical analyses included nonparametric and contingency table analyses. The PCEA group had better analgesia (> 50% reduction in pain scores, assessed both at rest and during a cough) for the first 3 days after surgery (p < 0.0,005). The PCEA group achieved discharge milestones approximately 36 hours faster (p < 0.002), but time until discharge was similar between groups. CONCLUSIONS: Ropivacaine-fentanyl PCEA provides superior analgesia, reduced opioid requirement, and more rapid recovery after colon surgery.
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.
UNLABELLED: Levobupivacaine is the isolated S-enantiomer of bupivacaine and may be a favorable alternative to spinal bupivacaine. However, its clinical efficacy relative to bupivacaine and its dose-response characteristics, in spinal anesthesia, must first be known. This double-blinded, randomized, cross-over study was designed to compare the clinical efficacy of hyperbaric levobupivacaine and bupivacaine for spinal anesthesia. Eighteen healthy volunteers were randomized into three equal groups to receive two spinal anesthetics, one with bupivacaine and the other with levobupivacaine, of equal-milligram doses (4, 8, or 12 mg). We assessed blockade quality and duration with pinprick, transcutaneous electrical stimulation, thigh tourniquet, abdominal and quadriceps muscle strength, modified Bromage scale, and time until achievement of discharge criteria. Sensory and motor block were similar between the same doses of levobupivacaine and bupivacaine (P > 0.56 to 0.86). For example, in the 12-mg groups of levobupivacaine versus bupivacaine, mean duration of tolerance to transcutaneous electrical stimulation at T12 was 100 min for both. The duration of motor block at the quadriceps was 71 versus 73 min, and time until achievement of discharge criteria was 164 min for both. Hyperbaric spinal levobupivacaine has equivalent clinical efficacy to racemic bupivacaine for spinal anesthesia in doses from 4 to 12 mg. IMPLICATIONS: Hyperbaric spinal levobupivacaine has equivalent clinical efficacy to hyperbaric spinal bupivacaine over the 4-12-mg ranges.
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BACKGROUND AND OBJECTIVES: Stimulating catheter-guided perineural placement may potentially increase the success rate and quality of continuous femoral nerve block as compared with a nonstimulating catheter technique. These hypotheses have not been rigorously tested. METHODS: Twenty volunteers underwent placement of bilateral femoral nerve catheters in this prospective, randomized, double-blind study. For each side, a stimulating needle was advanced until quadriceps contractions were obtained at < or =0.5 mA. On one side, a stimulating catheter was advanced 4 to 5 cm beyond the needle tip while eliciting quadriceps contractions via the catheter. If quadriceps contractions decreased or disappeared, the catheter position was adjusted until quadriceps contractions could be elicited at < or =0.5 mA. On the contralateral side, an identical catheter was advanced 4 to 5 cm beyond the needle tip without attempts to elicit quadriceps contractions via the catheter. After bolus injection of 10 mL lidocaine 1%, ropivacaine 0.2% at 10 mL/h was continuously infused through both catheters for 4 hours. Success of femoral block was defined as loss of sensation to cold and pinprick stimuli. Quality of successful block was determined by tolerance to transcutaneous electrical stimulation and force dynamometry of quadriceps strength. RESULTS: Block success was 100% via the stimulating catheters versus 85% via the nonstimulating catheters (P =.07). Overall tolerance to transcutaneous electrical stimulation (P =.009) and overall depth of motor block (P =.03) was significantly higher in the stimulating catheter-guided femoral nerve blocks. CONCLUSIONS: In this volunteer study, there was no statistically significant difference in block success between the two techniques. However, stimulating catheter-guided placement provided an increased overall quality of continuous femoral perineural blockade. Further studies are needed to verify these observations in the clinical setting.