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Biomedical subjects

Ban C H Tsui

Publications and source records attributed to Ban C H Tsui.

At least 19 recordsLinked to original sources
PubMed2006

Declining randomized clinical trials from Canadian anesthesia departments?

PURPOSE: The research productivity was estimated by publications from anesthesiology departments at Canadian universities over a five-year period, and the articles published were classified into several study designs. METHODS: In this observational study, the MEDLINE database was searched for publications listed by anesthesiology departments at Canadian universities as the primary corresponding source from 2000-2004. Abstracts were reviewed and each publication categorized into its respective methodological design. Impact factors of the journals in which the articles appeared were taken into consideration. "Total impact score" was defined as the total number of articles from a particular journal in a particular year multiplied by the impact factor value. Changes in overall publication numbers over the five-year period were compared and analyzed using Pearson correlation coefficients. RESULTS: Total Canadian anesthesia publications remained constant from 2000-2004. In this five-year time frame, the University of Toronto had the highest number of publications (271) followed by the University of Montreal (86), and McGill University (84). These universities conducted primarily randomized controlled trials (RCTs) whereas smaller Canadian universities mainly published case reports, reviews, and cohort studies. The number of RCTs conducted seems to be decreasing whereas the number of case reports and reviews being published are remaining constant over the five-year period. CONCLUSION: Although overall numbers in anesthesia publications do not suggest a significant decline, the number of RCTs decreased during the years 2000-2004. The quality of anesthesia research appears to be comparable to those in other medical specialties, with larger institutions conducting RCTs and smaller institutions publishing more case reports.

Academic Medical Centers↗
PubMed2006

Compressed air injection technique to standardize block injection pressures.

PURPOSE: Presently, no standardized technique exists to monitor injection pressures during peripheral nerve blocks. Our objective was to determine if a compressed air injection technique, using an in vitro model based on Boyle's law and typical regional anesthesia equipment, could consistently maintain injection pressures below a 1293 mmHg level associated with clinically significant nerve injury. METHODS: Injection pressures for 20 and 30 mL syringes with various needle sizes (18G, 20G, 21G, 22G, and 24G) were measured in a closed system. A set volume of air was aspirated into a saline-filled syringe and then compressed and maintained at various percentages while pressure was measured. The needle was inserted into the injection port of a pressure sensor, which had attached extension tubing with an injection plug clamped "off". Using linear regression with all data points, the pressure value and 99% confidence interval (CI) at 50% air compression was estimated. RESULTS: The linearity of Boyle's law was demonstrated with a high correlation, r = 0.99, and a slope of 0.984 (99% CI: 0.967-1.001). The net pressure generated at 50% compression was estimated as 744.8 mmHg, with the 99% CI between 729.6 and 760.0 mmHg. The various syringe/needle combinations had similar results. CONCLUSION: By creating and maintaining syringe air compression at 50% or less, injection pressures will be substantially below the 1293 mmHg threshold considered to be an associated risk factor for clinically significant nerve injury. This technique may allow simple, real-time and objective monitoring during local anesthetic injections while inherently reducing injection speed.

Air Pressure↗
PubMed2006

Innovative approaches to neuraxial blockade in children: the introduction of epidural nerve root stimulation and ultrasound guidance for epidural catheter placement.

Continuous epidural blockade remains the cornerstone of pediatric regional anesthesia. However, the risk of catastrophic trauma to the spinal cord when inserting direct thoracic and high lumbar epidural needles in anesthetized or heavily sedated pediatric patients is a concern. To reduce this risk, research has focused on low lumbar or caudal blocks (ie, avoiding the spinal cord) and threading catheters from distal puncture sites in a cephalad direction. However, with conventional epidural techniques, including loss-of-resistance for localization of the needle, optimal catheter tip placement is difficult to assess because considerable distances are required during threading. Novel approaches include electrical epidural stimulation for physiological confirmation and segmental localization of epidural catheters, and ultrasound guidance for assessing related neuroanatomy and real-time observation of the needle puncture and, potentially, catheter advancement. The present article provides a brief and focused review of these two advances, and outlines recent clinical experiences relevant to pediatric epidural anesthesia.

Anesthesia, Epidural↗
PubMed2005

Failed spinal anesthesia after a psoas compartment block.

PURPOSE: To report the case of a patient who experienced failed spinal anesthesia following a psoas compartment block (PCB) and discuss its implications. CLINICAL FEATURES: A 70-yr-old male was scheduled for a right total hip arthroplasty. He agreed to a PCB for postoperative analgesia and a spinal anesthetic. The spinal anesthetic was performed after completion of the PCB. Free flow of clear fluid was demonstrated at the beginning and at the end of the presumed intrathecal injection. General anesthesia had to be induced because of failure of the spinal anesthetic. The patient awoke from his general anesthetic with a functional PCB and no evidence of residual neuraxial anesthesia. The possibility of epidural spread of local anesthetic from the PCB impairing the ability to perform spinal anesthesia is discussed and reviewed. We hypothesize that local anesthetic in the epidural space may have falsely reassured the anesthesiologist that the needle was properly placed. CONCLUSION: We describe a case of failed spinal anesthesia following a PCB and discuss its implications.

Aged↗
PubMed2005

Caudal analgesia and anesthesia techniques in children.

PURPOSE OF REVIEW: Caudal epidural blockade remains the cornerstone of pediatric regional anesthesia. In this article we provide a comprehensive review of the recent developments in caudal anesthesia in infants and children. RECENT FINDINGS: Research has focused on prolonging the duration of single-shot caudal blocks and accurately positioning continuous caudal catheters. New local anesthetics with similar potencies but less toxicity have been introduced. Opioids prolong the duration of analgesia of local anesthetic, but have also been associated with unacceptable side effects, particularly in pediatric outpatients. Various non-opioid adjuncts with more favorable side-effect profiles may increase the duration of analgesia. New ultrasound and nerve-stimulation techniques have been developed to accurately guide epidural catheters to a specific spinal level. SUMMARY: The addition of ketamine or clonidine to a caudal local anesthetic prolong the duration of the block. However, a preservative-free preparation of ketamine that is suitable for neuraxial use is not widely available. Ultrasound imaging and electrical stimulation are promising options to accurately position a caudal needle. However, because ultrasound imaging is more difficult in older children, nerve stimulation is a more-suitable technique to accurately guide caudal catheters in this patient population. Although complications associated with caudal block are rare, the risks and benefits must be carefully considered on an individual basis.

Journal Article↗
PubMed2005

Propofol total intravenous anesthesia for MRI in children.

BACKGROUND: The aim of this study was to assess clinical signs of airway patency, airway intervention requirements and adverse events in 100 children receiving propofol total intravenous anesthesia for magnetic resonance imaging, with spontaneous ventilation and oxygenation via nasal prongs. METHODS: Airway patency was clinically assessed and stepwise interventions were performed until a satisfactory airway was achieved. Propofol requirements, vital signs, procedure times and adverse events were also recorded. RESULTS: Ninety-three per cent of children had no signs of airway obstruction when positioned with a shoulder roll only, two required a chin lift, four required an oral airway and one required lateral positioning. The mean propofol induction dose was 3.9 mg.kg(-1) (range 1.8-6.4 mg.kg(-1)). The mean propofol infusion rate was 193 microg.kg(-1).min(-1) (range 150-250 microg.kg(-1).min(-1)). The initial and final mean respiratory rates were 26 and 23 b.min(-1) (P < 0.05). Movement was more likely at lower infusion rates (mean 175 microg.kg(-1).min(-1)). There were no respiratory or cardiovascular complications (calculated risk: 95% CI = 0-3%). The mean time from end of scan to discharge home was 44 min. CONCLUSIONS: This study demonstrates good preservation of upper airway patency and rapid recovery using general anesthetic doses of propofol in children.

Adolescent↗
PubMed2005

Umbilical vein catheterization under electrocardiogram guidance.

BACKGROUND: In the neonate, umbilical venous catheters (UVC) are inserted and advanced blindly to a predetermined length from the umbilicus. The reported rates for UVC misplacement into the liver (and occasionally the spleen) range from 20 to 37%. Radiographs are routinely used to confirm the positioning of UVCs. This involves movement of often critically ill infants, as well as radiation exposure. This pilot study examines the potential value of confirming UVC placement in neonates using ECG. METHODS: In critically ill neonates, a conductive Johans ECG adapter was connected to a UVC. A satisfactory tracing (lead II) was obtained (right arm lead connected to the adapter) when the UVC was filled with saline solution allowing the catheter tip to become a unipolar ECG electrode. The UVC was then advanced from the umbilicus until the tip reached the inferior vena cava (IVC) within the thoracic region, as demonstrated by appearance of normal sized QRS complexes with small P-waves. A small QRS indicated the catheter was below the diaphragm. The appearance of a tall positive P-wave indicated the tip was at the right atrium level. The UVC was then withdrawn until the P-wave size returned to normal. The final UVC position was later confirmed by X-ray. RESULTS: Eight neonates were studied. The figure shows typical ECG tracings when the UVC was placed in the liver, IVC, and right atrium, respectively. Three malpositioned catheters were detected (2 into liver and 1 into spleen). CONCLUSIONS: Based on these cases, the insertion of UVCs in neonates can be guided with ECG by observing sequential and characteristic alterations in P-waves and QRS complexes, thereby reducing the use of X-rays. In addition, this technique could prove to be beneficial in remote healthcare facilities where X-ray machines may not be readily available and quick intravenous access is required to transport sick neonates to major centers.

Catheterization, Peripheral↗
PubMed2005

Combined propofol and remifentanil intravenous anesthesia for pediatric patients undergoing magnetic resonance imaging.

BACKGROUND: A prospective observational case series of children receiving light general anesthesia for magnetic resonance imaging (MRI) was performed. Our purpose was to examine the merit of anesthesia and recovery/discharge times of combined remifentanil and propofol total intravenous anesthesia (TIVA) in spontaneously breathing children. METHODS: After IRB approval and informed consent, 56 patients receiving Remi/Propofol TIVA (Remifentanil 10 microg.ml(-1) Propofol 10 mg.ml(-1)) were observed. Blood pressure, respiratory rate, endtidal CO(2) (P(E)CO(2)), oxygen saturation and temperature were recorded at the start and finish of anesthesia. In addition, induction and recovery times were noted. Recovery time was from scan completion until discharge from the initial recovery area. Discharge time was from scan completion to discharge home. RESULTS: Fifty-six patients received Remi/Propofol TIVA. The mean Remi/Propofol recovery and discharge times were 8.9 and 28.2 min, respectively. There was a statistically significant decrease in respiratory rate and increase in CO(2) from the start to the end of the procedure. During the scan, seven patients moved. One patient experienced postprocedure nausea and or vomiting. CONCLUSIONS: The combination of remifentanil and propofol for TIVA may be an effective method of light general anesthesia in pediatric patients undergoing MRI.

Anesthesia Recovery Period↗
PubMed2005

Can continuous low current electrical stimulation distinguish insulated needle position in the epidural and intrathecal spaces in pediatric patients?

BACKGROUND: Muscle twitches elicited with electrical stimulation (6-17 mA) during epidural insertion indicate correct epidural needle placement while muscle twitches at a lower current (<1 mA) may indicate intrathecal needle placement. This study examined whether applying continuous electrical stimulation at 6 mA could indicate needle entry into the epidural space without inadvertently penetrating the intrathecal space. METHODS: After institutional review board (IRB) approval, 10 pediatric patients scheduled for lumbar puncture were studied. Following sedation with propofol, an insulated 24-gauge Pajunck unipolar needle was inserted through an 18-gauge introducer needle placed at the L4-5 interspace. The needle was first connected to a nerve stimulator (6 mA) and advanced. At the first sign of muscle twitching, needle advancement was stopped and the threshold current for motor activity was determined. The current was then turned off, the stylet was removed and the needle checked for cerebrospinal fluid (CSF). If CSF was not present, the needle was advanced into the intrathecal space (as confirmed by the presence of CSF). Ten pediatric patients (ASA II or III) aged 7.8 +/- 4.3 years (2.8-16.0 years) were studied. RESULTS: All patients had two distinguishable threshold currents as the needle advanced. The mean threshold current to elicit muscle twitch in the presumed epidural space was 3.84 +/- 0.99 mA. CSF was not present in any of the patients at this location. The mean threshold current in the intrathecal space was 0.77 +/- 0.32 mA. The average estimated distance from the first threshold location to the intrathecal space was 3 mm. All muscle twitches were at the L3-5 myotomes. Nine muscle twitches were unilateral and one was bilateral. CONCLUSIONS: Monitoring with an insulated needle with electrical stimulation at 6 mA may prevent unintentional placement of epidural needles into the intrathecal space.

Anesthesia, Epidural↗
PubMed2005

Threshold current of an insulated needle in the intrathecal space in pediatric patients.

A threshold current of <1 mA has been suggested to be sufficient to produce a motor response to electrical stimulation in the intrathecal space. We designed this study to determine the threshold current needed to elicit motor activity for an insulated needle in the intrathecal space. Twenty pediatric patients aged 7.3 +/- 3.9 yr scheduled for lumbar puncture were recruited. After sedation with propofol, patients were turned to the lateral position and an 18-gauge or 20-gauge introducer needle was placed at the L4-5 level through which an insulated 24-gauge Pajunck unipolar needle (with a Sprotte tip and stylet) was inserted. The needle was advanced into the intrathecal space as suggested by the presence of a "pop." At this point, a nerve stimulator was attached to the insulated needle and the current was gradually increased until motor activity was evident. The needle hub was checked for cerebrospinal fluid. If cerebrospinal fluid was not present, the needle was advanced further until cerebrospinal fluid was present. The threshold current was retested. The mean current in the intrathecal space required to elicit a motor response was 0.6 +/- 0.3 mA (range, 0.1-1 mA). In 19 patients, the twitches were observed at the L4-5 myotomes and 1 patient had twitches at L2. Twitches were observed unilaterally in 19 children and bilaterally in one child. This confirms the hypothesis that the threshold current in the intrathecal space is <1 mA and that it differs significantly from the threshold currents reported for electrical stimulation in the epidural space.

Adolescent↗
PubMed2005

The use of electrical stimulation to monitor epidural needle advancement in a porcine model.

Muscle twitches elicited with electrical stimulation (ES) during epidural insertion may indicate epidural needle location. We examined the potential application of ES at 5 mA as a continuous method of monitoring the response to epidural needle advancement in a porcine model. Five 20-kg pigs were used in this study. A needle with a stimulating current of 5 mA was inserted at 20 separate levels in each pig. The needle was advanced until a muscle twitch was observed without loss-of-resistance (LOR). The needle position was then assessed using LOR. At the end of the experiment, an autopsy was performed to assess the spinal cord for injury. A total of 100 needle insertions were performed in the 5 pigs. The threshold current in the epidural space was 3.6 +/- 0.6 mA. In 59 of the needle insertions, LOR was not obtained at the depth at which a muscle twitch was initially observed. However, after advancing these 59 needles another 1-2 mm, LOR was obtained. In the other 41 insertions, LOR was observed without further advancement of the needle. Autopsies indicated there were no dural punctures or spinal cord damage in any of the pigs. These observations suggest that ES can be used to signal that the epidural needle is in or approaching the epidural space. However, the high false positive predictive value (59%) makes it impractical and unreliable to detect the precise entry of a needle into the epidural space in pigs.

Anesthesia, Epidural↗
PubMed2005

The electrophysiological effect of dextrose 5% in water on single-shot peripheral nerve stimulation.

When performing regional anesthesia, a small volume of local anesthetic or normal saline abolishes a motor response induced by a low current (0.5 mA). In this case series we describe the electrophysiological effect of a nonconducting (dextrose 5% in water, D5W) injectate on a motor response elicited by low current electrical stimulation. Twenty-nine peripheral nerve blocks were performed in 20 patients using insulated needles. Each needle was primed with D5W. The needle was advanced towards the target nerve until corresponding motor responses were observed using a current of 0.5 mA or less. Once the needle position was optimally placed, 1 mL of D5W was injected followed by a predetermined dose of local anesthetic. The effects of the injectates (D5W and local anesthetic) on the motor response were observed at all needle insertion sites. In all cases, the motor response was at least maintained or augmented (96%) immediately after the injection of D5W. All motor responses diminished after the injection of local anesthetic (100%). All blocks were considered clinically successful.

Anesthetics, Local↗
PubMed2005

Can direct spinal cord injury occur without paresthesia? A report of delayed spinal cord injury after epidural placement in an awake patient.

UNLABELLED: We discuss the etiology of a delayed spinal cord injury after epidural anesthesia without paresthesia. The description of such a case in an awake, adult patient who underwent a Whipple resection is provided. An epidural was performed at approximately the T8-9 interspace with the patient in the sitting position after 1 mg of midazolam was administered. On the first attempt, a dural puncture occurred. The patient did not report any paresthesia or pain. The needle was withdrawn and a second attempt was made one interspace lower. At this level, the epidural catheter was advanced into the epidural space uneventfully. Postoperatively, the patient suffered decreased motor function in the right leg. Magnetic resonance imaging revealed high signal intensity within the spinal cord, indicating cord edema compatible with direct needle trauma. An extradural fluid collection consistent with a hematoma was also noted. Although it may be impossible to confirm if the spinal cord injury was a result of direct needle trauma, hematoma, or a combination of needle trauma and hematoma, these events clearly raise the important question of whether an awake patient will always report paresthesia secondary to spinal cord trauma. IMPLICATIONS: This case reminds anesthesiologists that we should not simply assume paresthesia will always occur and be reported if a needle encroaches on the spinal cord even in an awake patient.

Aged↗