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Biomedical subjects

M Y Chow

Publications and source records attributed to M Y Chow.

12 recordsLinked to original sources
PubMed2000

Formulation and process considerations for beads containing Carbopol 974P, NF resin made by extrusion-spheronization.

Preliminary studies revealed that Carbopol 974P, NF resin could be incorporated into beads manufactured by extrusion and spheronization, and can slow the release of a highly water soluble drug if calcium chloride was included in the granulating fluid to reduce the tack of the wetted polymer. In this study, the same approach was used to produce high quality chlorpheniramine maleate beads with a prolonged release duration. Because of the complex nature of the extrusion and spheronization process and the various components in the bead formulations, a statistically sound factorial experiment was considered for this study. A one-half fraction of a two level factorial design with three center points was employed to estimate the effects of simultaneously modifying multiple process and formulation variables, including the Carbopol concentration, calcium chloride concentration, water content, and the spheronization speed and time. Product yield, average bead roundness, and the drug release profile were selected as responses. Increasing the Carbopol content across the experimental range resulted in a significant (P<0.05) reduction in the percentage drug released at 25, 40, and 60 min. Results suggest that combining the conditions of high Carbopol, high water, and low calcium chloride levels with low spheronization speeds at long spheronization times produce the highest quality bead with the longest drug release duration.

Acrylates↗
PubMed1999

Predicting the size of a double-lumen endobronchial tube using computed tomographic scan measurements of the left main bronchus diameter.

UNLABELLED: We investigated the use of chest computer tomographic (CT) scan measurement of the left mainstem bronchial diameter to predict the correct left-sided double-lumen endobronchial tube (DLT) size in Asian patients who may require smaller DLT sizes. Fifty consecutive Asian adults aged 17-80 yr with preoperative chest CT scans undergoing elective thoracic surgery were entered into the study. The measurements of the left main bronchus diameter were made by using the electronic calipers of the spiral scanner to the nearest millimeter. The sizes of DLT selected were 32F, 35F, 37F, 39F, and 41F for left main bronchus diameters of <10 mm, 10 mm, 11 mm, 12 mm, and >12 mm, respectively. All DLT placements were confirmed and positioned by using fiberoptic bronchoscopy. The tracheas of all patients were successfully intubated with the predicted DLT sizes. Thirty-four patients (68%) were predicted to require smaller DLTs (37F or smaller). Six patients were correctly predicted to receive 32F DLTs. Twelve patients (24%) received an oversized DLT, but none received an undersized DLT. The overall positive predictive value for the male and female patients was 84.4% and 61.1%, respectively. Our study showed that CT scan measurements of the diameter of the left bronchus were especially useful in choosing smaller DLTs. IMPLICATIONS: We used computer tomographic scans to measure the diameter of the left mainstem bronchus, then selected the size of the left-sided double-lumen endobronchial tube (DLT) accordingly. We found that we could predict the sizes of the DLT fairly accurately, especially the smaller DLTs.

Adolescent↗
PubMed1999

Comparison of sevoflurane with propofol for laryngeal mask airway insertion in adults.

UNLABELLED: We performed a prospective, randomized, controlled trial to compare the quality and ease of laryngeal mask airway (LMA) insertion after either rapid inhaled sevoflurane or i.v. propofol induction of anesthesia. Seventy-six unpremedicated ASA physical status I or II patients were anesthetized with either a single vital capacity breath of sevoflurane 8% or i.v. propofol 3 mg/kg, which produced equally rapid loss of consciousness (40.5 +/- 13.9 vs 37.7 +/- 9.9 s; P > 0.05). The LMA was inserted more rapidly in patients in the propofol group (74 +/- 29 vs 127 +/- 35 s; P < 0.01) and required fewer attempts (1.2 vs 1.6; P < 0.05) than the sevoflurane group. There was a greater incidence of initially impossible mouth opening in the sevoflurane group (45% vs 21%; P < 0.05). Once mouth opening was possible, the degree of attenuation of laryngeal reflexes was similar. The overall incidence of complications related to LMA insertion, especially apnea (32% vs 0%; P < 0.01), was more frequent in the propofol group (82% vs 26%; P < 0.01). There were four failures of LMA insertion in the propofol group and none in the sevoflurane group. Both groups had stable hemodynamic profiles and good patient satisfaction. We conclude that sevoflurane vital capacity breath induction compares favorably with i.v. propofol induction for LMA insertion in adults. However, prolonged jaw tightness after the sevoflurane induction of anesthesia may delay LMA insertion. IMPLICATIONS: In this randomized, controlled trial, we compared the ease of insertion of the laryngeal mask airway in adults after induction of anesthesia with either a sevoflurane vital capacity breath technique or propofol i.v.. We conclude that sevoflurane compares favorably with propofol, although prolonged jaw tightness may delay laryngeal mask airway insertion.

Adult↗
PubMed1998

Alkalinization of lidocaine does not hasten the onset of axillary brachial plexus block.

UNLABELLED: We assessed the onset of sensory and motor blockade as well as the distribution of sensory blockade after axillary brachial plexus block with 1.5% lidocaine hydrochloride 1:200,000 epinephrine with and without sodium bicarbonate in 38 patients. The onset of analgesia and anesthesia was recorded over the distributions of the median, ulnar, radial, and medial cutaneous nerves of the forearm, medial cutaneous and lateral cutaneous nerves of the arm, and musculocutaneous nerve. The onset of motor blockade of elbow and wrist movements was also recorded. Data were analyzed by using survival techniques and compared by using log rank tests. Only the onset of analgesia in the medial cutaneous nerves of the arm and forearm, and the onset of anesthesia in the medial cutaneous nerve of the arm were significantly faster (P < 0.05) with alkalinization of lidocaine. Our study showed that alkalinization of lidocaine does not significantly hasten block onset in most terminal nerve distributions. IMPLICATIONS: We examined whether alkalinizing a local anesthetic would quicken the onset of a regional upper limb nerve blockade. We found that alkalinization of lidocaine did not offer a significant clinical advantage in axillary brachial plexus blockade.

Adult↗
PubMed1998

Predicting the size of a double-lumen endobronchial tube based on tracheal diameter.

UNLABELLED: We assessed whether using the tracheal diameter to predict the correct size of the left double-lumen endobronchial tube (DLT) could be used for our generally smaller sized Asian patients. Sixty-six consecutive adult patients under anesthesia for elective surgery requiring the use of a DLT were studied. The size of the left-sided DLT used was based on the width of patients' trachea measured from the preoperative posterior-anterior chest radiograph. The placement of the DLT was standardized and confirmed with fiberoptic bronchoscopy. The correct size of the DLT was the largest size tube inserted into the left bronchus with a small air leak detectable when the endobronchial cuff was deflated but not exceeding the recommended resting volume when inflated for lung isolation. Using this method of choosing our DLT, we found that an oversized DLT was often chosen especially among our female Asian patients. The overall positive predictive values for the male and female patients were 77.3% and 45.5%, respectively. We postulate that this could be due to our criteria for correct DLT size or that our local Asian patients, especially the females, were smaller and shorter. IMPLICATIONS: This study assessed whether the correct double-lumen endobronchial tube size could be predicted from tracheal diameter measurements taken from the chest radiograph. We found that this method of choosing the double-lumen endobronchial tubes was not always reliable.

Adolescent↗
PubMed1997

Intrathecal pethidine: an alternative anaesthetic for transurethral resection of prostate?

We aimed to determine the usefulness of intrathecal pethidine as the sole anaesthetic for transurethral resection of prostate (TURP) while comparing the incidence of hypotension with intrathecal bupivacaine. A double-binded randomized prospective trial was conducted involving 40 patients for TURP. The patients were divided equally into two groups; group A received 2 ml 0.5% bupivacaine intrathecally and group B received 40 mg pethidine intrathecally. Changes in blood pressure and heart rate were measured over the first 30 minutes. The highest sensory block and the time to reach it were documented. The degree of motor blockade was also recorded. There was no significant difference in the incidence of hypotension. The pethidine group had significantly greater reduction in heart rate, a lower degree of motor block, shorter period before requests for postoperative analgesia but a higher incidence of sedation, nausea and vomiting. Intrathecal pethidine did not offer any advantage over intrathecal bupivacaine for TURP.

Aged↗
PubMed1997

A case of fluid embolism from transcervical endometrial resection.

Hysteroscopic transcervical endometrial resection (TCER) using a urological resectoscope offers an alternative to hysterectomy for some women with menorrhagia. The advantages of this technique are a shorter operating time and a rapid recovery and discharge. However, this procedure is not without risk of complications and one of them is related to dilutional hyponatraemia from absorption of the irrigation solution. This report describes a patient who experienced such a problem.

Adult↗
PubMed1994

Relationship between a fuzzy logic and a steepest descent approach to optimize a feedforward artificial neural network configuration.

The neural network designer must take into consideration many factors when selecting an appropriate network configuration. The performance of a given network configuration is influenced by many different factors such as: accuracy, training time, sensitivity, and the number of neurons used in the implementation. Using a cost function based on the four criteria mentioned previously, the various network paradigms can be evaluated relative to one another. If the mathematical models of the evaluation criteria as functions of the network configuration are known, then traditional techniques (such as the steepest descent method) could be used to determine the optimal network configuration. The difficulty in selecting an appropriate network configuration is due to the difficulty involved in determining the mathematical models of the evaluation criteria. This difficulty can be avoided by using fuzzy logic techniques to perform the network optimization as opposed to the traditional techniques. Fuzzy logic avoids the need of a detailed mathematical description of the relationship between the network performance and the network configuration, by using heuristic reasoning and linguistic variables. A comparison will be made between the fuzzy logic approach and the steepest descent method for the optimization of the cost function. The fuzzy optimization procedure could be applied to other systems where there is a priori information about their characteristics.

Electronic Data Processing↗