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Vincent W S Chan

Publications and source records attributed to Vincent W S Chan.

At least 19 recordsLinked to original sources
PubMed2007

Ultrasound-guided peripheral nerve blockade.

Peripheral nerve blockade (PNB) for orthopedic surgery is usually performed without visual guidance, relying mainly on surface anatomic landmarks and electrical stimulation to localize nerves. Moreover, multiple trial and error attempts to place a needle can frustrate the operator, cause unwarranted pain to the patient, and waste valuable time in the operating room. Inaccurate needle placement and spread of local anesthetic account for most PNB failures, whereas "trial and error" needle manipulations for nerve localization can cause complications. The recent application of ultrasound (US) to PNB affords real-time imaging of the target nerve, needle, and surrounding vasculature, such that needle proximity to the nerve is ensured and vascular puncture avoided. This article reviews the advantages, principles, and techniques of US for the most common types of PNB.

Brachial Plexus↗
PubMed2006

Ultrasound examination and localization of the sciatic nerve: a volunteer study.

BACKGROUND: Few studies have examined the use of ultrasound for sciatic nerve localization. The authors evaluated the usefulness of low-frequency ultrasound in identifying the sciatic nerve at three locations in the lower extremity and in guiding needle advancement to target before nerve stimulation. METHODS: In this prospective observational study, 15 volunteers underwent sciatic nerve examination using a curved ultrasound probe in the range of 2-5 MHz and a Philips-ATL 5000 unit (ATL Ultrasound, Bothell, WA) in the gluteal, infragluteal, and proximal thigh regions. Thereafter, an insulated block needle was advanced inline with the ultrasound beam to reach the nerve target, which was further confirmed by electrical stimulation. The quality of sciatic nerve images, ease of needle to nerve contact, threshold stimulating current, and resultant motor response were recorded. RESULTS: The sciatic nerve was successfully identified in the transverse view as a solitary predominantly hyperechoic structure on ultrasound in all of the three regions examined. The target nerve was visualized easily in 87% and localized within two needle attempts in all patients. Nerve stimulation was successful in 100% after two attempts with a threshold current of 0.42 +/- 0.12 (mean +/- SD) eliciting foot plantarflexion or dorsiflexion. CONCLUSIONS: These preliminary data show that a curved 2- to 5-MHz ultrasound probe provides good quality sciatic nerve imaging in the gluteal, infragluteal, and proximal thigh locations. Ultrasound-assisted sciatic nerve localization is potentially valuable for clinical sciatic nerve blocks.

Adult↗
PubMed2005

Needle placement and injection posterior to the axillary artery may predict successful infraclavicular brachial plexus block: a report of three cases.

PURPOSE: The combined use of ultrasound and nerve stimulation for localization of the brachial plexus during infraclavicular block has not been evaluated. We describe three cases of infraclavicular block where we used ultrasound to place the needle and catheter, observe type of muscle twitch obtained and local anesthetic spread after injection. CLINICAL FEATURES: Injection of local anesthetic after obtaining proximal muscle stimulation was associated with local anesthetic spread between the axillary artery and pectoral muscle. This resulted in block failure (case 1). In case 2, proximal stimulation was associated with anterior spread after a test injection. The needle and subsequently the catheter were repositioned posterior to the axillary artery and distal muscle stimulation obtained. Injection through the catheter resulted in local anesthetic spread posterior to the artery and successful block. In case 3, no distal twitch could be obtained but in light of previous experience the needle and then the catheter were placed posterior to the axillary artery. Posterior local anesthetic spread was observed and successful block ensued despite absence of any muscle stimulation. CONCLUSION: Ultrasound guidance during infraclavicular brachial plexus block enables direct visualization of needle/catheter tip location and confirmation of appropriate local anesthetic spread. Our early experience suggests that spread of injectate posterior to the second part of the axillary artery is associated with successful block.

Adult↗
PubMed2005

The measurement of postoperative pain: a comparison of intensity scales in younger and older surgical patients.

The psychometric properties of pain intensity scales for the assessment of postoperative pain across the adult lifespan have not been reported. The objective of this study was to compare the feasibility and validity of the Numeric Rating Scale (NRS), Verbal Descriptor Scale (VDS), and Visual Analog Scale (horizontal (VAS-H) and vertical (VAS-V) line orientation) for the assessment of pain intensity in younger and older surgical patients. At 24h following surgery, 504 patients, who were receiving i.v. morphine via patient-controlled analgesia, completed the pain intensity measures and the McGill Pain Questionnaire (MPQ) in a randomized order. They were asked which scale was easiest to complete, the most accurate measure, and which they would most prefer to complete in the future, as an index of face validity. The amount of opioid self-administered was recorded. Age differences in postoperative pain intensity were not found. However, elderly patients obtained lower MPQ scores and self-administered less morphine than younger people. Psychometric analyses suggested that the NRS was the preferred pain intensity scale. It had low error rates, and higher face, convergent, divergent and criterion validity than the other scales. Most importantly, its properties were not age-related. The VDS also had a favourable profile with low error rates and good face, convergent and criterion validity. Finally, difficulties with VAS use among the elderly were identified, including high rates of unscorable data and low face validity. Its use with elderly postoperative patients should be discouraged.

Adolescent↗
PubMed2004

Early but no long-term benefit of regional compared with general anesthesia for ambulatory hand surgery.

BACKGROUND: The purpose of this study was to determine whether either regional anesthesia (RA) or general anesthesia (GA) provided the best analgesia with the fewest adverse effects up to 2 weeks after ambulatory hand surgery. METHODS: Patients undergoing ambulatory hand surgery were randomly assigned to RA (axillary brachial plexus block; n = 50) or GA (n = 50). Before surgery, all patients rated their hand pain (visual analog scale) and pain-related disability (Pain-Disability Index). After surgery, eligibility for bypassing the postanesthesia care unit ("fast track") was determined, and pain, adverse effects, and home-readiness scores were measured. On postoperative days 1, 7, and 14, patients documented their pain, opioid consumption, adverse effects, Pain-Disability Index, and satisfaction. RESULTS: More RA patients were fast-track eligible (P < 0.001), whereas duration of stay in the postanesthesia care unit was shorter in the RA group (P < 0.001). Time to first analgesic request was longer in the RA group (P < 0.001), and opioid consumption was reduced before discharge (P < 0.001). In the RA group, the pain ratings measured at 30, 60, 90, and 120 min after surgery were lower (P < 0.001), and patients spent less time in the hospital after surgery (P < 0.001). More GA patients experienced nausea/vomiting during recovery in the hospital (P < 0.05). However, on postoperative days 1, 7, and 14, there were no differences in pain, opioid consumption, adverse effects, Pain-Disability Index, or satisfaction. CONCLUSIONS: Despite significant reduction in pain before discharge from the hospital after ambulatory hand surgery, single-shot axillary brachial plexus block does not reduce pain at home on postoperative day 1 or up to 14 days after surgery when compared with GA. However, RA does provide other significant early benefits, including reduction in nausea and faster discharge from the hospital.

Adult↗
PubMed2004

Pain management following discharge after ambulatory same-day surgery.

AIM AND BACKGROUND: Same-day surgeries are becoming routine for many surgical procedures. However, the degree to which patients need help with pain management at home following laparoscopic cholecystectomy (LC), shoulder, or hand ambulatory day surgery has received minimal examination. This study examined pain and related interference, analgesic use and adverse events, complications and resources utilized, and adequacy of postdischarge information at four time periods. METHODS: Data were collected from 180 patients by telephone interviews at 24, 48 and 72 hours, and 7 days after discharge. Patients (n = 78 hand, 48 shoulder, 54 LC surgery) were on average 41 years old. RESULTS: For all patients, worst 24-hour pain was reported as moderate to severe at all time periods. Using repeated measures anova demonstrated that shoulder patients had significantly more pain and overall pain-related interference, particularly in sleep and work, from 24 hours to day 7 than did hand or LC patients. The main analgesic taken was acetaminophen (paracetamol) with codeine 30 mg; 50% took no analgesia from 72 hours. About 20% experienced analgesic adverse events within 72 hours, mainly constipation and nausea. Only </=6% used non-pharmacological strategies. Bleeding (4%) and sore throat (11%) at 24-48 hours were identified as complications; six patients (4%) called their physician. Most patients received no information about analgesic use with inadequate pain relief and/or adverse events. CONCLUSIONS: Despite the considerable pain reported across all time periods, analgesic use and other interventions were minimal. Adverse events, which were problematic for some, may explain why patients stopped analgesics despite pain. These data support further research on more effective pain interventions and related education for day-surgery patients after discharge.

Adult↗
PubMed2004

Are patients comfortable consenting to clinical anesthesia research trials on the day of surgery?

UNLABELLED: Consent for clinical anesthesia research trials is often sought on the day of surgery when patients are most anxious and have little privacy or time for reflection. We conducted a retrospective survey of patients' perceptions and concerns regarding consent for clinical anesthesia trials on the day of surgery. Questionnaires were mailed to 175 patients who had participated in 1 of 6 negligible- or minimal-risk clinical anesthesia trials within the preceding year. Seventy-six patients responded (43%). Most patients (80%) reported that they understood the purpose of their trial, did not feel obligated (61%) or pressured (67%) to participate, and were satisfied (mean visual analog scale: 71 mm) with the recruitment and consent process on the day of surgery. Few patients (7%) believed that their well-being was put at risk because of their participation in the trial. IMPLICATIONS: This retrospective survey suggests that patient recruitment and consent for negligible- or minimal-risk clinical anesthesia research trials is appropriate when performed on the day of surgery.

Adult↗
PubMed2004

A survey of orthopedic surgeons' attitudes and knowledge regarding regional anesthesia.

UNLABELLED: We conducted a survey to explore the surgical attitudes and preferences regarding regional anesthesia among Canadian orthopedic surgeons. Surveys were returned by 468 (61%) of 768 surgeons. Forty-eight percent of respondents directed their patients' choice of anesthetic. Forty percent of surgeons directed their patients to choose regional anesthesia. The principal reasons for favoring regional anesthesia were less postoperative pain (32%), decreased nausea and vomiting (12%), and safety (14%). Reasons for not favoring regional anesthesia were delays in the induction of anesthesia (43%) and an unpredictable success rate (12%). This survey suggests that orthopedic surgeons are supportive of regional anesthesia. Barriers to increased popularity include perceived delays and unreliability. IMPLICATIONS: Orthopedic surgeons understand the benefits of and are supportive of the use of regional anesthesia in their practices. Barriers to increased popularity include perceived operating room delays and lack of reliability.

Adult↗
PubMed2003

Intravenous ropivacaine bolus is a reliable marker of intravascular injection in premedicated healthy volunteers.

PURPOSE: We designed the following volunteer study to determine if an intravascular bolus dose of ropivacaine could be found that would reliably produce mild symptoms of central nervous system (CNS) toxicity in sedated humans. METHODS: After Ethics Committee approval and informed consent 15 volunteers were recruited. Cardiovascular (CVS) monitoring including pulse oximetry, electrocardiogram and non-invasive blood pressure monitoring was applied. In phase 1, volunteers received in sequence placebo, 30 mg, 45 mg and 60 mg of ropivacaine as a 10-mL iv bolus over 20 sec with a two-hour rest period between each injection to allow plasma clearance of drug. Volunteers were asked to report symptoms of local anesthetic toxicity on a verbal response scale. After any dose volunteers reporting greater than three symptoms with a severity of > 3/10 for greater than three minutes were excluded from further study doses. The dose that consistently produced mild CNS toxic effects was chosen for phase 2 of the study. In phase 2, volunteers were given iv midazolam 0.03 mg*kg(-1) prior to bolus ropivacaine or placebo in a randomized double-blind crossover fashion. Volunteers were asked to report toxic symptoms and venous blood samples were obtained for ropivacaine assay. RESULTS: In phase 1, ropivacaine 60 mg was found to produce consistent mild symptoms of CNS toxicity. No volunteer experienced major CNS or CVS adverse effect during the study. After midazolam premedication all volunteers reported symptoms with bolus ropivacaine 60 mg. Mean peak ropivacaine venous concentration was 4.48 mg*L(-1). CONCLUSION: An intravascular bolus of ropivacaine 60 mg reliably produces mild CNS toxic symptoms in premedicated volunteers.

Adjuvants, Anesthesia↗
PubMed2003

Postoperative morphine use and hyperalgesia are reduced by preoperative but not intraoperative epidural analgesia: implications for preemptive analgesia and the prevention of central sensitization.

BACKGROUND: The aim of this study was to evaluate the postoperative morphine-sparing effects and reduction in pain and secondary mechanical hyperalgesia after preincisional or postincisional epidural administration of a local anesthetic and an opioid compared with a sham epidural control. METHODS: Patients undergoing major gynecologic surgery by laparotomy were randomly assigned to three groups and studied in a double-blinded manner. Group 1 received epidural lidocaine and fentanyl before incision and epidural saline 40 min after incision. Group 2 received epidural saline before incision and epidural lidocaine and fentanyl 40 min after incision. Group 3 received a sham epidural control (with saline injected into a catheter taped to the back) before and 40 min after incision. All patients underwent surgery with general anesthesia. RESULTS: One hundred forty-one patients completed the study (group 1, n = 45; group 2, n = 49; group 3, n = 47). Cumulative patient-controlled analgesia morphine consumption at 48 h was significantly lower (P = 0.04) in group 1 (89.8 +/- 43.3 mg) than group 3 (112.5 +/- 71.5 mg) but not group 2 (95.4 +/- 60.2 mg), although the hourly rate of morphine consumption between 24 and 48 h after surgery was significantly lower (P < 0.0009) in group 1 (1.25 +/- 0.02 mg/h) than group 2 (1.41 +/- 0.02 mg/h). Twenty-four hours after surgery, the visual analog scale pain score on movement was significantly less intense (P = 0.005) in group 1 (4.9 +/- 2.2 cm) than group 3 (6.0 +/- 2.6 cm) but not group 2 (5.3 +/- 2.5 cm), and the von Frey pain threshold near the wound was significantly higher (P = 0.03) in group 1 (6.4 +/- 0.6 log mg) than in group 3 (6.1 +/- 0.8 log mg) but not group 2 (6.2 +/- 0.7 log mg). CONCLUSIONS: Preincisional administration of epidural lidocaine and fentanyl was associated with a significantly lower rate of morphine use, lower cumulative morphine consumption, and reduced hyperalgesia compared with a sham epidural condition. These results highlight the importance of including a standard treatment control group to avoid the problems of interpretation that arise when two-group studies of preemptive analgesia (preincisional vs. postsurgery) fail to find the anticipated effects.

Adaptation, Psychological↗
PubMed2003

Brachial plexus examination and localization using ultrasound and electrical stimulation: a volunteer study.

BACKGROUND: Current techniques of brachial plexus block are "blind," and nerve localization can be frustrating and time consuming. Previous studies on ultrasound-assisted brachial plexus blocks are mostly performed with scanning probes of 10 MHz or less. The authors tested the usefulness of a state-of-the-art, high-resolution ultrasound probe (up to 12 MHz) in identifying the brachial plexus in five locations of the upper extremity and in guiding needle advancement to target before nerve stimulation. METHODS: In this prospective observational study, 15 volunteers underwent brachial plexus examination using an L12-L5 MHz probe and a Philips-ATL 5000 ultrasound unit in the interscalene, supraclavicular, infraclavicular, axillary, and midhumeral regions. Thereafter, an insulated block needle was advanced under direct ultrasound guidance to target nerves before confirmation by electrical nerve stimulation in five volunteers in each of the interscalene, supraclavicular, and axillary regions. The quality of brachial plexus images, anatomic variations, and the technique of needle advancement for nerve localization were recorded. RESULTS: The brachial plexus components were successfully identified in the transverse view as round to oval hypoechoic structures with small internal punctuate echos in all regions examined except the infraclavicular area (visualized in 27% of the cases). The authors' technique of advancing the needle in-line with the ultrasound beam allowed moment-by-moment observation of the needle shaft and tip movement at the time of nerve localization. Hypoechoic structures were stimulated electrically and confirmed to be nerves. CONCLUSIONS: These preliminary data show that the high-resolution L12-L5 probe provides good quality brachial plexus ultrasound images in the superficial locations i.e., the interscalene, supraclavicular, axillary, and midhumeral regions. The needle technique described here for ultrasound-assisted nerve localization provides real-time guidance and is potentially valuable for brachial plexus blocks.

Adult↗
PubMed2003

Ultrasound-guided supraclavicular brachial plexus block.

UNLABELLED: In this study, we evaluated state-of-the-art ultrasound technology for supraclavicular brachial plexus blocks in 40 outpatients. Ultrasound imaging was used to identify the brachial plexus before the block, guide the block needle to reach target nerves, and visualize the pattern of local anesthetic spread. Needle position was further confirmed by nerve stimulation before injection. The block technique we describe aligned the needle path with the ultrasound beam. The block was successful after one attempt in 95% of the cases, with one failure attributable to subcutaneous injection and one to partial intravascular injection. Pneumothorax did not occur. Our preliminary data suggest that a high-resolution ultrasound probe can reliably identify the brachial plexus and its neighboring structures in the supraclavicular region. The technique of real-time guidance during needle advancement can quickly localize nerves. Distinct patterns of local anesthetic spread observed on ultrasound can further confirm accurate needle location. IMPLICATIONS: Real-time ultrasound imaging during supraclavicular brachial plexus blocks can facilitate nerve localization and needle placement and examine the pattern of local anesthetic spread.

Adult↗