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Biomedical subjects

G W Stevenson

Publications and source records attributed to G W Stevenson.

At least 55 records · Page 3Linked to original sources
PubMed1994

Characterization of infection with endemic porcine reproductive and respiratory syndrome virus in a swine herd.

Infection of 8-week-old pigs with endemic porcine reproductive and respiratory syndrome (PRRS) virus was detected on a farm that had an epidemic of PRRS in 1989. During the 2.5 years since the original epidemic, reproductive performance of the breeding herd had been within acceptable limits, but mortality had periodically exceeded one-fourth of the pigs in the nursery (195 died of 761 weaned, 25.6%). Investigators attempted to determine the age and humoral immune status of pigs infected with endemic PRRS virus on the farm. Serum obtained from 9 groups of 1- to 18-week-old pigs (10 pigs/group) was examined for PRRS virus by virus isolation. Serum was obtained from 8 sows that had farrowed within the preceding 24 hours. Serum from the sows was obtained weekly until litters were weaned at 3 weeks of age. Serum was obtained from 27 newborn pigs (3 to 4 newborn pigs from each of the 8 sows) prior to intake of colostrum and at weekly or biweekly intervals until the pigs were 20 to 21 weeks of age. Isolation of PRRS virus and indirect fluorescent antibody serologic testing were performed on these serum samples. In another study, serum was obtained for serologic testing from 10 sows in each of 6 parity groups. The PRRS virus was isolated from serum of only 3- to 12-week-old pigs. The 8 sows and their 27 pigs were seronegative for PRRS virus during the 3-week lactation period. By 10 weeks of age, 18 of the 27 suckling pigs were still alive and had seroconverted (titers > or = 1:20).(ABSTRACT TRUNCATED AT 250 WORDS)

Age Factors↗
PubMed1994

Comparison of a rigid laryngoscope with the ultrathin fibreoptic laryngoscope for tracheal intubation in infants.

The flexible ultrathin fibreoptic laryngoscope allows placement of endotracheal tubes as small as 2.5 mm internal diameter. The purpose of this study was to document the safety and efficacy of intubation using an ultrathin fibreoptic laryngoscope. Proved safety and efficacy would justify the routine use of fibreoptic laryngoscopy in normal infants to maintain skills needed for management of the difficult infant airway. In this prospective study, 40 infants < 24 mo of age scheduled for elective surgery were randomly divided into two equal groups. After inhalation induction of anaesthesia, in 20 infants the trachea was intubated using direct rigid laryngoscopy, and in 20 using the ultrathin fibreoptic laryngoscope (size 1.8 mm OD) Olympus LFP. Time to successful intubation was recorded, as well as blood pressure, heart rate, end-tidal CO2 and oxygen saturation. Airway trauma in the operating room, the post-anaesthesia care unit, and on the first postoperative day was recorded. The intubation times using rigid laryngoscopy were less than those using fibreoptic laryngoscopy (13.6 +/- 0.9 sec (mean +/- SEM) vs 22.8 +/- 1.7 sec; P < 0.01). Oxygen saturation and end-tidal CO2 readings were not different between the two groups. After intubation, blood pressure and heart rate increased equally in both groups, returning to normal within one to two minutes. There was no difference in the airway trauma between groups. We conclude that the ultrathin fibreoptic laryngoscope is a safe and effective method for tracheal intubation in infants and may be used routinely in order to maintain fibreoptic airway skills.

Anesthesia, Inhalation↗
PubMed1994

Colon cancer detection: an algorithm using endoscopy and barium enema.

A review of findings on flexible sigmoidoscopy (FS), colonoscopy and selected double-contrast barium enema (DCBE) radiographs from a group of 66 patients with rectal bleeding was performed to test the value of an algorithm in the detection of colonic cancers and polyps. In this algorithm the FS findings would direct patients either to colonoscopy or to a modified DCBE which focused attention on the colon proximal to the sigmoid. Only patients with neoplasms diagnosed by FS, or by MDCBE after negative FS, would proceed to colonoscopy. The study population contained four cancers, 11 polyps > 5 mm and 11 polyps < or = 5 mm; FS+MDCBE missed four polyps, all < 5 mm. For polyps > 5 mm and cancer, FS+MDCBE had a sensitivity of 100%, a specificity of 82%, a negative predictive value of 1.0 and a positive predictive value of 0.62. Using the algorithm, 24 patients (36%) would have required colonoscopy. The results suggest that FS+MDCBE is a potentially valuable method for screening patients for colonic neoplasia.

Algorithms↗
PubMed1994

Colorectal cancer overlooked at barium enema examination and colonoscopy: a continuing perceptual problem.

PURPOSE: To evaluate reasons for missed diagnosis of colorectal carcinoma at barium enema (BE) examination and colonoscopy and determine if standards have improved since a similar study in 1981. MATERIALS AND METHODS: Relevant studies obtained within 3 years of diagnosis in 161 patients with colorectal carcinoma treated in 1990 were reviewed. RESULTS: Twenty-seven carcinomas were overlooked at BE examination and seven at colonoscopy. Fifteen percent of BE examination errors were purely perceptive (ie, the tumor was visible in retrospect). Another 15% were purely technical. Combined perceptive and technical errors occurred in 45% of cases. Interpretive errors (ie, the lesion was misinterpreted as benign) occurred in 25% of cases. CONCLUSION: Similar reasons for missing diagnoses of colorectal cancer at BE examination were seen in 1990 and 1981, with a high rate of perceptive errors. Double reading BE studies may reduce this rate, and readiness to perform BE examination after an incomplete colonoscopy may reduce colonoscopic "misses."

Barium Sulfate↗
PubMed1994

Mice and rats (laboratory and feral) are not a reservoir for PRRS virus.

Porcine reproductive and respiratory syndrome (PRRS) is caused by an unclassified arterivirus. The syndrome was first reported in the USA in 1987 as epizootics of reproductive failure in sows and respiratory disease in nursery, growing, and fattening pigs. An enzootic form of the disease has now emerged, characterized by interstitial pneumonia and an increased incidence of secondary infections. Because the disease has now become enzootic on many farms, rodents were investigated as a possible reservoir for the infection. Wild rodents from an endemically infected farm were trapped, and virus isolation for PRRS virus (PRRSV) was attempted using porcine primary alveolar macrophage cultures. PRRSV was not isolated from serum and selected pooled tissues (thymus, lung, and spleen) of 14 feral mice and 2 feral rats. Also, transmission experiments were carried out on 3-week-old Balb/c mice and 12-week-old Fischer-344 rats to determine if these species were susceptible to infection. The rodents were inoculated intranasally, orally, and intraperitoneally with a virus proven to transmit PRRS to pigs. Virus isolations from selected pooled tissues (lung, spleen, thymus, and kidney) and from serum were negative, and there were neither gross nor microscopic lesions. Weight gains and white blood cell counts were not significantly different between treated and control groups. These results indicate that rodents are not susceptible to infection with PRRSV and therefore are probably not a reservoir for the disease.

Animals↗
PubMed1994

Anesthetic considerations for the pediatric plastic surgical patient.

An understanding of the anesthesiologist's concerns during pediatric plastic surgical procedures can facilitate the coordination of efforts between the multiple services involved in the care of these children. Prior to surgery, the child's history is obtained and physical examination is performed. The condition of the airway is the primary concern. Preoperative medication is usually given by oral routes to avoid injections. Induction intubation, maintenance, and emergence are discussed. Specific postanesthesia care is described. Special precautions are given for children having surgical repair of craniofacial anomalies. Cleft lip and palate and mandibular advancement are described.

Age Factors↗
PubMed1993

Radiology and endoscopy in the pretreatment diagnostic management of colorectal cancer.

This paper discusses the imaging methods available for the detection and diagnosis of colon cancer, concentrating on endoscopy and barium radiology. Effective utilization of these two methods may be facilitated by using flexible sigmoidoscopy to direct further investigation. There is a need for educational efforts to enhance the performance of endoscopy and barium radiology so that the high standards achieved in some published series are more generally available to patients. New developments in contrast agents will alter rapidly the roles of ultrasound, CT scanning, and magnetic resonance in the investigation and management of colorectal cancer.

Colonic Neoplasms↗
PubMed1993

Same-day computed tomography during arterial portography and delayed high-dose iodine computed tomography: an efficient approach to imaging potentially resectable liver tumours.

Preoperative imaging in patients with potentially resectable liver tumours has traditionally been performed in specialized hepatobiliary centres. To assess the feasibility and value of establishing a same-day, pre-resectional hepatic imaging service, computed tomography during arterial portography (CTAP) and delayed high-dose iodine computed tomography (DICT) were used to examine patients considered suitable for curative hepatic resection. The study group comprised 27 patients (14 from hospitals not affiliated with a university and 13 from two university-affiliated hospitals) for whom pre-referral imaging showed tumour distribution amenable to resection. Among the patients from centres not affiliated with a university, seven had undergone ultrasonography (US) and equilibrium-phase CT, four had undergone US and unenhanced CT, two had undergone equilibrium-phase CT only and one had undergone bolus dynamic incremented CT (BDCT) only. For 12 of the patients coming from the university-affiliated centres, the pre-referral imaging had consisted of US and BDCT; the other had undergone US only. After CTAP and DICT, 20 (74%) of the 27 patients were reclassified as having unresectable disease: 7 (54%) of the 13 patients who had undergone BDCT before CTAP and DICT and 12 (92%) of the 13 patients who had undergone unenhanced or equilibrium-phase CT, as well as the patient who had undergone US only. By averting laparotomy in 20 of the patients, CTAP and DICT resulted in short-term health care savings of about $160,000. These findings suggest that BDCT was underused in the hospitals not affiliated with university centres.(ABSTRACT TRUNCATED AT 250 WORDS)

Angiography↗
PubMed1992

Antagonism of drug discrimination learning within the conditioned taste aversion procedure.

Animals injected with morphine prior to the presentation of a saccharin-LiCl pairing and the morphine vehicle prior to saccharin alone rapidly acquired the drug discrimination, avoiding saccharin following the administration of morphine and consuming saccharin following its vehicle after only four conditioning trials. Once stimulus control was established, the opiate antagonist naloxone (1 mg/kg) was administered prior to morphine in a test of its ability to antagonize the morphine stimulus. Pretreatment times ranged from 10 to 180 min. Naloxone antagonized the stimulus properties of morphine for all subjects, although there were individual differences in the onset, duration (time course) and degree of antagonism. Together with the rapid acquisition typically reported in this design, the fact that antagonism was demonstrated in the present study suggests that the conditioned taste aversion procedure may be useful in the general assessment of drug discriminations.

Animals↗