Biomedical subjects
Publications and source records attributed to E Y Cheng.
The use of epidural opioids for postoperative analgesia has been associated with respiratory depression. This report demonstrates the ability of nalbuphine to rapidly reverse the respiratory depression caused by epidural sufentanil while maintaining postoperative pain relief.
The effects of sustained lung inflation on systemic vascular capacitance (SVC), systemic vascular resistance (SVR), and cardiac sympathetic efferent nerve activity (SENA) were investigated in anesthetized dogs. By use of a total cardiopulmonary bypass, the lungs were inflated to tracheal pressures of 10, 15, and 20 mmHg. Tracheal pressures of 10, 15, and 20 mmHg increased system vascular capacitance by 1.4, 3.1, and 4.3 ml/kg and decreased systemic vascular resistance by 0.11, 0.15, and 0.16 mmHg.kg.min-ml-1, respectively, at low carotid sinus pressure (CSP) of 41 mmHg. SENA showed a concomitant decrease. Bilateral vagotomy attenuated the change in SVR by 69%, SVC by 62%, and SENA by 97% when lungs were inflated to a tracheal pressure of 20 mmHg at a low CSP. These results indicate that lung inflation causes a reflex induced increase in SVC as well as a decrease in both SVR and SENA. The lung inflation reflex is mediated primarily through vagal afferent nerve fibers with a small contribution from other afferent nerve pathways.
Glass particle contamination of the contents of single-dose glass ampules can occur upon opening. In our study we determined if different aspirating techniques or different ampule types had any effect on glass particle contamination. In part 1 of this study different aspiration techniques were evaluated. The four groups included a control group of 3 mm tubing, an 18-g 1.5-inch needle, a filter needle, and an in-line filter. A significant reduction in glass particle contamination was found when using either an in-line filter or a filter needle compared with the control group or when aspirating through an 18-g needle. The average number of glass particles found per ampule for each group was 100.6 +/- 16.3, 65.6 +/- 18.7, 1.3 +/- 0.3, and 1.2 +/- 0.3, respectively, for the control group, 18-g needle, filter needle, and in-line filter. In part 2 we examined four types of glass ampules: transparent metal etched, transparent chemically etched, amber metal etched, and amber chemically etched. There was a significantly greater number of glass particles found in the transparent metal etched ampules compared with that found in the other three ampule types. Transparent metal etched ampules yielded an average total number of particles per ampule of 45.9 +/- 15.4 compared with 3.2 +/- 0.9, 6.0 +/- 1.7, and 3.1 +/- 0.6, in the transparent chemically etched, amber metal etched, and amber chemically etched ampule types, respectively. This study demonstrates that using drugs supplied in ampules other than transparent metal etched type and by using filters will decrease the risk of parenteral injection of glass particles.
Usual monitoring sites for pulse oximetry involve the fingers, toes, ear lobe, and nasal septum. This study examined the performance of a forehead sensor compared with a finger sensor for the pulse oximeter and arterial blood gas (ABG) analysis. Ten healthy adult volunteers and 22 ventilator-dependent patients were studied. The arterial oxygen saturation detected by forehead pulse oximetry (SpO2) correlated well with finger SpO2 and arterial oxygen saturation (SaO2) determined by arterial blood gas analysis in the healthy volunteers. Forehead SpO2 in mechanically ventilated patients correlated well with finger SpO2 and SaO2 when heart rate detected by pulse oximeter differed less than 10% from apical heart rate. Factors that caused a difference in oximeter-detected heart rate and apical heart rate were extensive tissue edema, head movement, and difficulty securing good tape placement. This suggests that when signal strength is weak, causing poor pulse rate detection, there will also be problems associated with accurate SpO2. The forehead pulse oximeter sensor works well on healthy, well-oxygenated volunteers. Difficulty was experienced when applying and using the sensor on critically ill patients. The reliability of the forehead pulse oximeter sensor has not been established at low saturations.
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Nasal tip surgery is a compromise, in which the surgeon gives away something to achieve something--a narrower, more defined, and stable tip component of the nose. Years of experience are required to thoroughly understand and master tip surgery techniques. While gaining this arduous but invaluable insight, emphasis should always be placed on conservation of tip anatomic structures and avoidance of radical excision and sacrifice of tip tissue. Compulsive long-term follow-up and evaluation of patients, both by frequent examination and review of standardized, uniform photographs, best facilitates the development of expertise in nasal tip surgical refinement.
We report on the incidence of Rh isoimmunization after genetic amniocentesis at our institution. In 115 Rh negative women who underwent amniocentesis and subsequently delivered Rh positive infants, there were 4 (3.4%) sensitizations before birth. This was significantly greater than the 1.5% rate of gestational sensitization found in pooled populations of women who did not undergo amniocentesis. We also noted a significant increase in the number of sensitizations that occurred before 28 weeks. The results were consistent with those of previous studies of this issue, and are discussed in relation to current policies for managing Rh negative women who have second trimester amniocentesis.
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The superior rehabilitative potential of the below knee amputee versus the above knee amputee is well known. In end-stage occlusive vascular disease, the limiting factor in determining how distal an amputation can be performed is whether or not the stump will heal. The use of clinical judgement to determine the correct amputation level has historically been proven to be too subjective. Therefore, several procedures have been proposed which would hopefully fulfill the need for a reliable, objective method for determining the optimal amputation level. These procedures include the measurement of local and cutaneous blood flow and pressure, blood volume, and skin temperature. After evaluating the studies done on each of these procedures, it is evident that the measurement of skin capillary blood flow is the most accurate parameter for predicting wound healing potential.
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Monitoring of the effectiveness of ventilation is a significant problem during high-frequency ventilation (HFV). The time necessary to achieve equilibrium of the arterial tension of carbon dioxide (Paco2) following step changes in ventilation is appreciable, because of large body stores of CO2. Waiting for Paco2 to reach equilibrium is not only time-consuming but a potentially dangerous means of monitoring ventilator adjustments during HFV. Five kittens of mean +/- SD 1,082 +/- 383 gm weight were studied during HFV, both with normal lungs and lungs injured by saline lavage-induced surfactant depletion. The transcutaneous tension of carbon dioxide (Ptcco2) was monitored continuously to determine the time required to achieve equilibrium of Paco2 following a step change in ventilation. The rate of pulmonary CO2 elimination (VECO2) was measured immediately before and immediately after (less than 12 sec) step changes in ventilation and was used to predict the change in Paco2 achieved once equilibrium was reestablished. With normal lungs, equilibration time following step changes in ventilation was found to be approximately 20 minutes. After step decreases in ventilation of the injured lung, achieving equilibrium state took significantly longer, approximately 30 minutes. The Paco2 predicted was significantly related to the change in Paco2 achieved at equilibrium for both normal and injured lung studies. We concluded that direct monitoring of VECO2 during HFV may be a useful clinical monitoring technique, allowing rapid and accurate assessment of the efficiency of ventilation following step changes in ventilation and potentially assisting in optimizing ventilator settings.
Approximately 40% of physician office time and 33% of hospital time are devoted to patients 65 years of age or older. Over half of the older population requires some surgical intervention. Because of decreased physiologic reserve and increased number of underlying medical disorders, the older patient is at increased risk for intraoperative and postsurgical complications. Since cardiovascular, pulmonary, and renal complications are frequent in the elderly patient, the preoperative evaluation should emphasize these organ systems. Risk factors should be assessed initially by a focused history and physical examination and by simple tests. Additional diagnostic testing should be reserved for the patient who is not clearly at low or high risk. For optimal preoperative evaluation of the elderly patient, the physician should identify systemic disease, determine if the patient is receiving appropriate therapy, delineate the operative risks, and make recommendations that can potentially reduce the operative risks and postoperative complications.
Amniotic fluid embolism (AFE) is a rare obstetric problem characterized by sudden onset of hypotension, hypoxemia, and coagulopathy. This case represents the difficulty in differentiating AFE from other etiologies of cardiopulmonary compromise. The definitive diagnosis of AFE is made at autopsy with the demonstration of fetal cell elements in the pulmonary vasculature. Diagnosis can be highly suspected if squamous cells and other debris of presumed fetal origin are demonstrated in blood aspirated from the central venous or pulmonary artery circulation of symptomatic parturients. Predisposing factors for AFE include advanced maternal age, multiparity, large fetal size, and short tumultuous labor, especially if uterine stimulants are used. Cardiopulmonary resuscitation is the key to the treatment of parturients with AFE. A pulmonary artery catheter can be helpful in diagnosis and hemodynamic management of parturients with AFE.
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BACKGROUND AND OBJECTIVES: Pain from labor and delivery is often attenuated with epidural anesthesia. A complication of indwelling epidural catheters is intraspinal hematoma. The development of a bleeding diathesis can worsen complications markedly. CONCLUSIONS: Frequent assessment of neurologic status is important until the underlying cause of the coagulopathy can be treated and the bleeding resolves. If there is no indication of intraspinal bleeding, we recommend removing the catheter because of potential catheter migration. If bleeding is occurring around the catheter insertion site and possibly in the epidural or subarachnoid space, the catheter may be left in place to tamponade the insertion site. In cases of intraspinal hematoma, which can cause neurologic deficits, immediate decompression surgery is needed.
This study was designed to determine the contribution of diaphragm dysfunction and pain to respiratory insufficiency after upper abdominal surgery. Respiratory insufficiency and postoperative pain in humans were evaluated by pulse oximetry, pulmonary function tests, and a visual analog scale. Diaphragm shortening in dogs was evaluated with biplane videoroentgenography. In humans, despite reasonable pain control, pulmonary function, as reflected in forced vital capacity (FVC), forced expiratory volume in one second (FEV1) and arterial oxygen saturation (SpO2) were significantly reduced on the first postoperative day. Improved pain control was not associated with improvements in FVC or FEV1. In the dogs, diaphragm shortening and tidal volume were significantly reduced in the immediate postoperative period. Phrenic nerve stimulation immediately after surgery resulted in supramaximal diaphragm shortening, which indicated neither the diaphragm nor phrenic nerves were significantly injured by surgical manipulation. Diaphragm dysfunction has a major role in postoperative pulmonary insufficiency; an afferent-mediated reflex inhibition of the phrenic nerves may be responsible.