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Biomedical subjects

W O Richards

Publications and source records attributed to W O Richards.

At least 19 recordsLinked to original sources

Incidence and significance of pneumomediastinum after laparoscopic esophageal surgery.

BACKGROUND: Pneumomediastinum can be a sign of esophageal perforation. During laparoscopic esophageal surgery, the mediastinum is exposed to carbon dioxide gas under pressure that can cause pneumomediastinum. METHODS: Forty-five patients undergoing laparoscopic esophageal procedures had erect, inspiratory, single-view chest radiographs (CXR) performed in the recovery room (RR). Patients with extraabdominal gas underwent daily erect, inspiratory, single-view CXR until resorption of the gas or discharge from the hospital. Insufflation time and pressure were recorded, and morbidity was evaluated. Results are expressed as mean +/- SEM. RESULTS: Twenty-five men (56%)and 20 women (44%) aged 33.0 +/- 2.9 years underwent 10 Heller myotomies (22.2%), 27 Nissen fundoplications (60.0%), six Toupet fundoplications (13.3%), and two paraesophageal hernia repairs (4.4%). Twenty-four patients (53.3%) had normal CXR in RR, and 21 (46.7%) had extraabdominal gas. Eighteen (85.7%) of the 21 had pneumomediastinum, three (14.3%) had pneumothorax, and 12 (57.1%) had subcutaneous emphysema in RR. Sixteen of these 21 remained hospitalized and had repeat CXR on postoperative day 1. Of these 16, five (31.3%) had normal CXR, 11 (68.8%) had pneumomediastinum, and seven (43.8%) had subcutaneous emphysema. There were no esophageal perforations and no chest tube insertions, and there was no morbidity related to pneumomediastinum. CONCLUSION: Pneumomediastinum is observed frequently following laparoscopic esophageal operations and often persists past 24 h. After these operations, pneumomediastinum is not necessarily indicative of esophageal perforation. In this group, it caused no clinically significant events that altered the course of the patients.

Adolescent↗

Adhesion formation is reduced after laparoscopic surgery.

BACKGROUND: Adhesion formation after abdominal operations causes significant morbidity. METHODS: Adhesion formation in pigs was compared after placement of prosthetic mesh during celiotomy (group 1), laparoscopy with large incision (group 2), and laparoscopy (group 3). After peritoneum was excised, polypropylene mesh was fixed to the abdominal wall, then to the opposite abdominal wall in the preperitoneal space followed by peritoneal closure. Adhesion area, grade, and vascularity were measured. RESULTS: More adhesions (p < 0.02) covered intraperitoneal mesh (7.57 +/- 1.89 cm2) than covered reperitonealized mesh (2.16 +/- 1.13 cm2), and adhesion grade was significantly greater (p < 0.02). Adhesion areas were significantly greater in groups 1 and 2 than in group 3 (p = 0.001 and 0.03, respectively). Adhesion grade was significantly greater in groups 1 and 2 than in group 3 (p = 0.02 and p = 0.04, respectively). Groups 1 and 2 had more vascular adhesions than group 3 (p < 0.01 and p = 0.02, respectively) CONCLUSIONS: A foreign body within the peritoneum stimulates more numerous and denser adhesions. Tissue trauma distant from the site of adhesions increases their formation. A major advantage of laparoscopic surgery is decreased adhesion formation.

Abdomen↗

Prevalence of gastroesophageal reflux after laparoscopic Heller myotomy.

BACKGROUND: There is still some controversy over the need for antireflux procedures with Heller myotomy in the treatment of achalasia. This study was undertaken in an effort to clarify this question. METHODS: To determine whether Heller myotomy alone would cause significant gastroesophageal reflux (GER), we studied 16 patients who had undergone laparoscopic Heller myotomy without concomitant antireflux procedures. Patients were asked to return for esophageal manometry and 24-h pH studies after giving informed consent for the Institutional Review Board (IRB)-approved study at a median follow-up time of 8.3 months (range, 3-51). Results are expressed as the mean +/- SEM. RESULTS: Fourteen of the 16 patients reported good to excellent relief of dysphagia after myotomy. They were subsequently studied with a 24-h pH probe and esophageal manometry. These 14 patients had a significant fall in lower esophageal sphincter (LES) pressure from 41.4 +/- 4.2 mmHg to 14.2 +/- 1.3 mmHg, after the myotomy (p < 0.01, Student's t-test). The two patients who reported more dysphagia postoperatively had LES pressures of 20 and 25 mmHg, respectively. Two of 14 patients had DeMeester scores of >22 (scores = 61.8, 29.4), while only one patient had a pathologic total time of reflux (percent time of reflux, 8%). The mean percent time of reflux in the other 13 patients was 1.9 +/- 0.6% (range, 0.1-4%), and the mean DeMeester score was 11.7 +/- 4.6 (range, 0.48-19.7). CONCLUSIONS: Laparoscopic Heller myotomy is effective for the relief of dysphagia in achalasia if the myotomy lowers the LES pressure to <17 mmHg. If performed without dissection of the entire esophagus, the laparoscopic Heller myotomy does not create significant GER in the postoperative period. Clearance of acid refluxate from the aperistaltic esophagus is an important component of the pathologic gastroesophageal reflux disease (GERD) seen after Heller myotomy for achalasia. Furthermore, GERD symptoms do not correlate with objective measurement of GE reflux in patients with achalasia. Objective measurement of GERD with 24 h pH probes may be indicated to identify those patients with pathologic acid reflux who need additional medical treatment.

Digestive System Surgical Procedures↗

Endoscopic coverage of fetal myelomeningocele in utero.

OBJECTIVE: Our goal was to evaluate the safety and efficacy of minimally invasive surgery for the coverage of myelomeningocele in utero. STUDY DESIGN: Women in the mid-second trimester of a pregnancy complicated by fetal myelomeningocele were offered an experimental procedure designed to prevent ongoing exposure of the spinal cord to the intrauterine environment. The procedure consisted of maternal laparotomy while the patient was under both general and epidural anesthesia, with exposure of the gravid uterus. Endoscopic ports were placed for camera and operating instruments. Amniotic fluid was removed and replaced with carbon dioxide. The fetus was then positioned and a maternal split-thickness skin graft was placed over the exposed spinal cord or neural elements. The skin graft and a covering of Surgicel Absorbable Hemostat were attached with fibrin glue prepared from autologous cryoprecipitate. RESULTS: Four fetuses with open myelomeningocele underwent endoscopic coverage of the spinal lesion between 22 weeks 3 days and 24 weeks 3 days of gestation. One infant, delivered by planned cesarean section at 35 weeks' gestation after demonstration of fetal lung maturity, is almost 3 years old. A second infant was delivered by cesarean section at 28 weeks after preterm labor and is now almost 6 months old. Both survivors manifest only mild motor and somatosensory deficits. One fetus who was delivered 1 week after operation after development of amnionitis died in the delivery room of extreme prematurity. The final fetus died intraoperatively from abruptio placentae. CONCLUSION: Minimally invasive fetal surgery appears to constitute a feasible approach to nonlethal fetal malformations that result in progressive and disabling organ damage.

Adult↗

Noninvasive detection of ischemic bowel.

PURPOSE: Acute mesenteric arterial occlusion is an abdominal catastrophe that carries high morbidity and mortality rates. Current diagnostic methods, however, lack sensitivity and specificity and do not provide information about the viability of the affected bowel. Early diagnosis and intervention would improve patient outcomes and survival rates. The basic electrical rhythm (BER) is the omnipresent electrical slow wave of the gastrointestinal tract that characterizes the underlying electrical activity of the bowel. BER frequency is known to fall with ischemia. Superconducting quantum interference devices (SQUIDs) can detect BER by measuring the magnetic fields generated by the electrical activity of the smooth muscle of the small bowel. The purpose of this study was to determine the ability of a SQUID to detect mesenteric ischemia in a free-lying section of small bowel in an animal model of acute superior mesenteric artery occlusion. METHODS: Seven adult male rabbits (six experimental and one control) were studied with transabdominal SQUID and electrode recordings during baseline and after the induction of mesenteric ischemia with balloon occlusion of the superior mesenteric artery. Continuous recordings were taken for 120 minutes of ischemia and analyzed with autoregressive spectral analysis to determine the BER frequency during specific time points of the study. Two independent investigators blinded to the experimental preparation examined the results to determine whether there was decreased BER frequency and thus ischemia. The results are expressed as mean +/- SEM, and paired t tests were used to determine statistical significance. RESULTS: BER was detected in all seven animals and fell from 10.7 +/- 0.5 cpm to 7.0 +/- 1.8 cpm after 30 minutes of ischemia in the magnetic channels (P <.05, with t test). The fall in BER was detected by the SQUID in all six experimental animals. The blinded observers correctly identified healthy and ischemic magnetic data recording, with a sensitivity of 94% and specificity of 100%. CONCLUSION: SQUIDs can noninvasively detect bowel ischemia early in a free-lying segment of small bowel in this animal model with a high degree of sensitivity and specificity.

Animals↗

18Fluorodeoxyglucose-positron emission tomography in the management of patients with suspected pancreatic cancer.

OBJECTIVE: To assess the accuracy and clinical impact of 18fluorodeoxyglucose-positron emission tomography (18FDG-PET) on the management of patients with suspected primary or recurrent pancreatic adenocarcinoma, and to assess the utility of 18FDG-PET in grading tumor response to neoadjuvant chemoradiation. SUMMARY BACKGROUND DATA: The diagnosis, staging, and treatment of pancreatic cancer remain difficult. Small primary tumors and hepatic metastases are often not well visualized by computed tomographic scanning (CT), resulting in a high incidence of nontherapeutic celiotomy and the frequent need for "blind resection." In addition, the distinction between local recurrence and nonspecific postoperative changes after resection can be difficult to ascertain on standard anatomic imaging. 18FDG-PET is a new imaging technique that takes advantage of increased glucose metabolism by tumor cells and may improve the diagnostic accuracy of preoperative studies for pancreatic adenocarcinoma. METHODS: Eighty-one 18FDG-PET scans were obtained in 70 patients undergoing evaluation for suspected primary or recurrent pancreatic adenocarcinoma. Of this group, 65 underwent evaluation for suspected primary pancreatic cancer. Nine patients underwent 18FDG-PET imaging before and after neoadjuvant chemoradiation, and in eight patients 18FDG-PET scans were performed for possible recurrent adenocarcinoma after resection. The 18FDG-PET images were analyzed visually and semiquantitatively using the standard uptake ratio (SUR). The sensitivity and specificity of 18FDG-PET and CT were determined for evaluation of the preoperative diagnosis of primary pancreatic carcinoma, and the impact of 18FDG-PET on patient management was retrospectively assessed. RESULTS: Among the 65 patients evaluated for primary tumor, 52 had proven pancreatic adenocarcinoma and 13 had benign lesions. 18FDG-PET had a higher sensitivity and specificity than CT in correctly diagnosing pancreatic carcinoma (92% and 85% vs. 65% and 62%). Eighteen patients (28%) had indeterminate or unrecognized pancreatic masses on CT clarified with 18FDG-PET. Seven patients (11%) had indeterminate or unrecognized metastatic disease clarified with 18FDG-PET. Overall, 18FDG-PET suggested potential alterations in clinical management in 28/65 patients (43%) with suspected primary pancreatic adenocarcinoma. Of the nine patients undergoing 18FDG-PET imaging before and after neoadjuvant chemoradiation, four had evidence of tumor regression by PET, three showed stable disease, and two showed tumor progression. CT was unable to detect any response to neoadjuvant therapy in this group. Eight patients had 18FDG-PET scans to evaluate suspected recurrent disease after resection. Four were noted to have new regions of 18FDG-uptake in the resection bed; four had evidence of new hepatic metastases. All proved to have metastatic pancreatic adenocarcinoma. CONCLUSIONS: These data confirm that 18FDG-PET is useful in the evaluation of patients with suspected primary or recurrent pancreatic carcinoma. 18FDG-PET is more sensitive and specific than CT in the detection of small primary tumors and in the clarification of hepatic and distant metastases. 18FDG-PET was also of benefit in assessing response to neoadjuvant chemoradiation. Although 18FDG-PET cannot replace CT in defining local tumor resectability, the application of 18FDG-PET in addition to CT may alter clinical management in a significant fraction of patients with suspected pancreatic cancer.

Adenocarcinoma↗

The human vector magnetogastrogram and magnetoenterogram.

Electrical activity in the gastrointestinal system produces magnetic fields that may be measured with superconducting quantum interference device magnetometers. Although typical magnetometers have detection coils that measure a single component of the magnetic field, gastric and intestinal magnetic fields are vector quantities. We recorded gastric and intestinal magnetic fields from nine abdominal sections in nine normal human volunteers using a vector magnetometer that measures all three Cartesian components of the magnetic field vector. A vector projection technique was utilized to separate the magnetic field vectors corresponding to gastric and intestinal activity. The gastric magnetic field vector was oriented in a cephalad direction, consistent with previously observed data, and displayed oscillatory characteristics of gastric electrical activity (f = 3.03 +/- 0.18 cycles/min). Although the small bowel magnetic field vector showed no consistent orientation, the characteristic frequency gradient of the small bowel electrical activity was observed. Gastric and intestinal magnetic field vectors were oriented in different directions and were thus distinguished by the vector projection technique. The observed difference in direction of gastric and intestinal magnetic field vectors indicates that vector recordings dramatically increase the ability to separate physiological signal components from nonphysiological components and to distinguish between different physiological components.

Analog-Digital Conversion↗

Intestinal tachyarrhythmias during small bowel ischemia.

The electrical control activity (ECA) of the bowel is the omnipresent slow electrical wave of the intestinal tract. Characterization of small bowel electrical activity during ischemia may be used as a measure of intestinal viability. With the use of an animal model of mesenteric ischemia, serosal electrodes and a digital recording apparatus utilizing autoregressive spectral analysis were used to monitor the ECA of 20 New Zealand White rabbits during various lengths of ischemia. ECA frequency fell from 18.2 +/- 0.5 cycles per minute (cpm) at baseline to 12.2 +/- 0.9 cpm (P < 0.05) after 30 min of ischemia and was undetectable by 90 min of ischemia in all animals. Tachyarrhythmias of the ECA were recorded in 55% of the animals as early as 25 min after ischemia was induced and lasted from 1 to 48 min. Frequencies ranged from 25 to 50 cpm. These tachyarrhythmias were seen only during ischemia, suggesting that they are pathognomonic for intestinal ischemia. The use of the detection of ECA changes during intestinal ischemia may allow earlier diagnosis of mesenteric ischemia.

Animals↗

Effects of mesenteric ischemia and reperfusion on small bowel electrical activity.

UNLABELLED: Previous studies involving basic electrical rhythm (BER) have not been carried out far enough to fully characterize the relationship between mesenteric ischemia and BER. The phenomenon of reperfusion injury has also not been correlated with BER activity. The goal of this study was to characterize changes in BER during mesenteric ischemia and reperfusion and to correlate them with changes in pathology. METHODS: Serosal electrodes were used to record the electrical activity of rabbit jejunum (n = 20) at baseline, during ischemia (90-210 min), and during reperfusion (120-240 min). BER frequency and amplitude were monitored, and biopsies were taken at the end of ischemia and reperfusion. A pathologist blinded to the specimen identity graded the histology on a scale of 0 (no changes) to 6 (transmural necrosis). Paired t test, the Kruskal-Wallis test of non-parametric ranks, and Fisher's r to z test were used for statistical significance where appropriate. RESULTS: BER frequency and amplitude fell significantly after 15 min of ischemia and became undetectable by 90 min of ischemia in all animals. The likelihood that BER would return during reperfusion was highly correlated with length of ischemia (r = 0.99). Longer periods of reperfusion were associated with increasing pathologic grade. CONCLUSIONS: BER frequency and amplitude are very sensitive to ischemia and their changes occur well before histopathologic changes. The variation in electrical activity of the small bowel during ischemia and reperfusion is a dynamic process that reflects the metabolic state of the smooth muscle. If electrical activity of the bowel is to be used for assessment of viability, continuous recordings more accurately reflect the metabolic state of the smooth muscle.

Animals↗

Selective effect of liver disease on the activities of specific metabolizing enzymes: investigation of cytochromes P450 2C19 and 2D6.

BACKGROUND AND OBJECTIVES: Drug metabolism is influenced by liver disease because of the central role that the liver plays in metabolic activities in the body. However, it is still unclear how activities of specific drug-metabolizing enzymes are influenced by the presence and severity of liver disease. As a consequence, alteration in metabolism of specific drugs cannot be easily predicted or appropriate dosage adjustment recommendations made. METHODS: The activities of cytochromes P450 (CYP) 2C19 and 2D6 were investigated in a group of patients with mild or moderate liver disease (n = 18) and a group of healthy control subjects (n = 10). The disposition of racemic mephenytoin for CYP2C19 and debrisoquin for CYP2D6 were characterized in plasma and urine samples collected over 192 hours. RESULTS: The elimination of S-mephenytoin was severely reduced among patients with liver disease, resulting in a 79% decrease in plasma clearance for all patients combined. This reduction was related to the severity of disease, patients with moderate disease being affected more severely than patients with mild disease. Similar differences were observed in the urinary excretion of 4'-hydroxymephenytoin metabolite. By contrast, there was no effect on the disposition of R-mephenytoin or debrisoquin. CONCLUSION: These results show selectivity in the effect of liver disease on activities of specific metabolizing enzymes, CYP2C19 being more sensitive than CYP2D6. They suggest that recommendations for modification in drug dosage in the presence of liver disease should be based on knowledge of the particular enzyme involved in metabolism of the drug. The results emphasize the need for further studies of each specific drug-metabolizing enzyme in the presence of liver disease.

Adult↗

The outcome of laparoscopic Heller myotomy without antireflux procedure in patients with achalasia.

We retrospectively reviewed 30 patients with achalasia (18 males, 12 females) undergoing laparoscopic Heller myotomy without antireflux procedure to determine relief of dysphagia and prevalence of postoperative gastroesophageal reflux. Preoperative symptoms were obtained by history alone before 1996 and by standardized questionnaire after September 1996. Twenty-nine patients (97%) had dysphagia, 22 patients (73%) had regurgitation, 21 patients (70%) had weight loss, 7 patients (23%) had heartburn, and 4 patients (13%) had nocturnal aspiration. The first 3 patients were done thoracoscopically, with the subsequent 27 patients performed laparoscopically; 4 cases (13%; 1 thoracoscopic and 3 laparoscopic) were converted. The mean postoperative stay was 1.9 days (1-6 days). One patient underwent repeat laparoscopic myotomy for persistent dysphagia. Twenty-eight patients (93%) were available for follow-up. Patients were asked on a standardized questionnaire to grade their relief of dysphagia, regurgitation, and heartburn. Good to excellent relief of dysphagia was obtained in 25 patients (89%), whereas 3 patients (11%) continued to have significant dysphagia postoperatively. Twenty-four patients (86%) had little or no regurgitation. Four patients (14%) had frequent regurgitation. Twenty-four patients (89%) reported little or no heartburn. Three patients (11%) reported significant postoperative heartburn. Laparoscopic Heller esophagomyotomy without antireflux procedure provides excellent symptomatic relief of dysphagia in patients with achalasia. Early follow-up suggests that minimal occurrence of symptomatic postoperative reflux can be achieved without performing an antireflux procedure.

Adolescent↗

Superconducting quantum interference device magnetometer for diagnosis of ischemia caused by mesenteric venous thrombosis.

Although mesenteric venous thrombosis carries a better prognosis than arterial thrombosis, mortality and morbidity are still high. Previous studies have shown that the basic electrical rhythm (BER) of the bowel decreases early after induction of arterial ischemia. Furthermore, our studies have shown that these changes occur prior to pathologic changes and that they can be recorded noninvasively using a superconducting quantum interference device (SQUID). SQUIDs measure magnetic fields that are created by the electrical activity of the gastrointestinal smooth muscle and have been used to measure the BER of the small intestine in human volunteers. This study was conducted to determine if a SQUID could be used for early noninvasive detection of mesenteric venous ischemia in an animal model. Simultaneous recordings from serosal electrodes and a SQUID outside the abdomen were taken from anesthetized New Zealand rabbits. Recordings were made for 15 minutes before and 90 minutes after injection of thrombin into the superior mesenteric vein. The basic electrical rhythm of the small bowel dropped from 16.42 +/- 0.69 to 8.80 +/- 0.74 cycles per minute at 30 minutes and to 6.82 +/- 0.722 after 90 minutes (p < 0.0001, paired t-test). The correlation coefficient between the SQUID and electrical recordings was 0.954 (p < 0.0001). These data suggest that the ischemia caused by mesenteric venous thrombosis results in changes in the bioelectrical activity, which can be noninvasively detected using a SQUID.

Animals↗

Laparoscopic surgical treatment of achalasia.

BACKGROUND: The authors have performed 11 myotomies in 10 patients (aged 12 to 77) with achalasia using minimally invasive techniques. METHODS: The initial 3 patients were treated via transthoracic approach; the subsequent 7 patients via transabdominal approach. The length of the myotomy was determined in conjunction with intraoperative endoscopy to facilitate dissection and demonstrate division of the lower esophageal sphincter. RESULTS: Only 1 patient required intravenous and intramuscular narcotics more than 24 hours postoperatively; 2 patients required no postoperative narcotics. The average hospital stay for those patients successfully treated endoscopically averaged 2.0 +/- 0.5 days (range 1.5 to 3). One patient was converted to open thoracotomy secondary to perforation of the mucosa. One patient required repeat laparoscopic myotomy at 3 months due to recurrent dysphagia. Follow-up conducted at clinic visits showed all patients to have benefitted with relief of dysphagia; 80% (8) reported excellent results, 10% (1) reported good results, and 10% (1) fair results. CONCLUSION: We converted from thoracic to laparoscopic myotomy because the abdominal approach simplified anesthetic and surgical management. We conclude that laparoscopic myotomy is a simple and effective treatment of achalasia.

Adolescent↗

Correlation and comparison of magnetic and electric detection of small intestinal electrical activity.

The small intestinal basic electrical rhythm (BER) was detected simultaneously with serosal electrodes and a transabdominal superconducting quantum interference device (SQUID) magnetometer in anesthetized rabbits. We induced mesenteric ischemia to correlate serosal electrode recording of changes in BER with the SQUID magnetometer. The BER frequency was obtained by spectral analysis of the data using Fourier and autoregressive techniques. There was a high degree of correlation (r = 0.96) between the BER frequency determined using the serosal electrodes and the BER frequency ascertained from SQUID data. Additionally, the effects of an electrical insulator on the external electric and magnetic fields were studied in the rabbit model. The presence of an insulator profoundly attenuates external electric potentials recorded by cutaneous electrodes but does not significantly affect external magnetic fields or serosal potentials. We conclude that SQUID magnetometers could noninvasively record small intestinal BER that was highly correlated with the activity recorded by invasive serosal electrodes. The advantages of magnetic field measurements have encouraged us to investigate clinical applications.

Abdomen↗

Magnetoenterography (MENG): noninvasive measurement of bioelectric activity in human small intestine.

The basic electrical rhythm (BER) of the gastrointestinal tract creates minute magnetic fields that have been measured in animals using a Superconducting QUantum Interference Device (SQUID) gradiometer. The aim of this study was to measure noninvasively the biomagnetic fields of human stomach and small intestine. Twenty-one human volunteers were studied using a 37-channel SQUID gradiometer positioned over the epigastrium and umbilicus. In one volunteer additional biomagnetic recordings were performed in order to map the spatial variation of the biomagnetic fields. Cyclical waveforms consistent with gastric BER [3.0+/-0.5 cycles per minute (cpm)] and small intestine BER (10.26+/-1.74 cpm) were seen in the epigastrium and umbilicus, respectively. The mapping study identified the expected frequency gradient (12.0 cpm in duodenum, 11.3 cpm in jejunum, to 9.7 cpm in ileum) within the small intestine. Noninvasive recordings of human gastric and small intestinal BER can be obtained using a SQUID gradiometer.

Adult↗

Laparoscopic esophagomyotomy for achalasia in children.

Achalasia is an uncommon condition in children. The authors report on two children who were evaluated and treated with laparoscopic esophagomyotomy. A 6-port technique was used, with five 5-mm ports and one 10-mm port. During the procedure, esophagoscopy was performed simultaneously, which provided esophageal distension for easier dissection and aided the surgeon by documenting when a complete myotomy had been accomplished. The patients' symptoms have resolved, and no postoperative complications have developed. Laparoscopic esophagomyotomy can be performed safely in children and is an effective approach for treatment of this disorder. Its advantages over the open approach include shorter hospitalization and less discomfort.

Adolescent↗