Faeco-pneumothorax as the presenting feature of a traumatic diaphragmatic hernia.
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Colonic Diseases↗
Biomedical subjects
B T Jackson
Publications and source records attributed to B T Jackson.
Whither general surgery?
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General Surgery↗
Fetal responses to altered maternal oxygenation in rhesus monkey.
The purpose of this study was to establish (in the primate) maternal-fetal relations for blood gas parameters and certain related aspects of fetal cardiovascular function with the mother at rest and subjected to a range of altered states of oxygenation. In 10 chronically cannulated rhesus monkey fetuses, with the mother lightly sedated with phencyclidine, on each of two days we studied the effects of maternal hypoxia and hyperoxia [(15, 10, and 100% maternal fractional concentration of inspired O2 (FIO2)] on maternal and fetal pH, PCO2, PO2 and O2 concentration (CaO2) and fetal heart rate, blood pressure, and superior vena caval (SVC) flow distribution. We observed a linear correlation between maternal and fetal pH and PCO2. There was evidence of a fetal metabolic acidosis with 10 but not with 15% hypoxia. Maternal-fetal PO2 and CaO2 correlated in curvilinear and linear fashion, respectively. Maternal-fetal CaO2 difference was maintained within a narrow range (2.7-4.8 vol%) for various states of maternal oxygenation, showing a tendency to expand only with severe (10%) hypoxia. Results indicate that quantitative delivery of O2 to the placenta was of paramount importance as a determinant of O2 transfer to the fetus and are compatible with a "concurrent flow" model of transplacental O2 diffusion. Fetal heart rate decreased progressively with 15 and 10% hypoxia. SVC flow to lungs and placenta varied reciprocally with changes in fetal oxygenation. As indicated by distribution to the heart, shunting of SVC flow through the foramen ovale was modest at rest, with no evident change in response to fetal hypoxemia.
Animals↗
Plasma catecholamines in the hypoxaemic fetal rhesus monkey.
To assess the response of the sympathoadrenal system of the primate fetus to oxygen deprivation, we measured plasma catecholamines in 8 chronically catheterized fetal rhesus monkeys. A range of fetal hypoxaemia was produced by having the mother inspire 15, 10, or 9% oxygen mixtures while tranquilized with ketamine. Catecholamines from fetal carotid and maternal femoral arteries were measured by radioenzymatic assay. Fetal plasma norepinephrine and epinephrine concentrations increased significantly at all levels of hypoxaemia, but dopamine increased only at very low fetal oxygen tensions. Norepinephrine levels exceeded those of epinephrine and dopamine under all conditions. Relatively more severe hypoxaemia was necessary to elevate concentrations of epinephrine above baseline as compared with norepinephrine. A negative exponential correlation (P less than 0.001) was found between both fetal arterial PO2 and oxygen content and plasma norepinephrine and epinephrine, which was qualitatively similar to that observed previously in the sheep fetus. Maternal catecholamines were found to increase during hypoxaemia as well, but to a lesser degree than in the fetus.
Animals↗
Bile peritonitis after removal of T-tubes from the common bile duct.
Bile peritonitis can occur when a T-tube is electively removed from the common bile duct, but this is regarded as a rare complication. Plastic T-tubes are known to increase the risk and should not be used. Latex rubber T-tubes are preferred but the complication can still occur. We present three patients with this complication despite the use of a latex T-tube. A questionnaire was sent to 107 surgeons in the South East Thames Region. The replies showed that the complication is far more common than generally realized. Based on these replies the risk of bile peritonitis each time a latex T-tube is electively removed from the common bile duct is calculated to be 0.84 per cent or 1 in every 119 explorations.
Aged↗
Transfemoral placement of intraluminal polyurethane prosthesis for abdominal aortic aneurysm.
Because of the significant mortality associated with the conventional surgical approach to abdominal aortic aneurysms (AAA) in the high risk patients and in those with ruptured aneurysms, we have developed a new approach to this problem, intraluminal aneurysm exclusion. This was achieved by an intraluminal prosthesis which approximated the diameter of the aorta above and below the aneurysm and is inserted through the femoral artery. The prosthesis consisted of biomedical grade elastomeric polyurethane with a NITINOL and/or stainless steel frame and was designed in such a configuration that it could be compressed inside a 15 F catheter and then regain its original shape after being discharged inside the aorta. The polyurethane prosthesis tolerated static pressures in excess of 300 Torr. Aneurysmal aortas were created in three adult sheep using large knitted Dacron pathches (6 X 9 cm) sewn onto a longitudinal aortotomy. After 4-6 weeks, an intraluminal prosthesis was passed transfemorally to the location of the aortic aneurysm. Following satisfactory placement and expansion of the prosthesis, a laceration was produced in the aneurysmal wall. No bleeding developed, which confirmed the integrity of the prosthesis in excluding the aneurysm from the aorta proper. Pulsation in the iliac arteries indicated the presence of aortic blood flow through the prosthesis. Autopsy examination demonstrated directly that the prosthesis was open and that its two ends were fixed in the aorta above and below the aneurysm. The study has demonstrated that intraluminal AAA exclusion could be achieved with an intraluminal polyurethane prosthesis inserted through the femoral artery.
Animals↗
Full thickness rectal prolapse associated with primary intraabdominal pathology.
Full thickness rectal prolapse as a presenting feature of occult intraabdominal disease is rare. Two such cases are described and the possible mechanisms discussed. The importance of adequate investigation is emphasized.
Aged↗
Investigations of the simian ontogenic switch from fetal to adult hemoglobin at the progenitor cell level.
The ontogenic switch from fetal to adult hemoglobin could result from discontinuous events, such as replacement of fetal erythroid progenitor cells by adult ones, or gradual modulation of the hemoglobin program of a single progenitor cell pool. The former would result in progenitors at midswitch with skewed fractional beta-globin synthesis programs, the latter in a Gaussian distribution. For these studies, we obtained bone marrow from rhesus monkey fetuses at 141-153 d (midswitch). Mononuclear cells were cultured in methyl cellulose with erythropoietin, and single BFU-E-derived colonies were removed and incubated with [3H]leucine. Globin synthesis was examined by gel electrophoresis and fluorography. The beta-globin synthesis pattern of single fetal colonies was skewed, and did not fit a normal distribution. The fetal pattern resembled the pattern of an artificial mixture of fetal and adult progenitors, suggesting that the fetal progenitor pool could contain populations with different beta-globin programs. This non-Gaussian distribution in the progenitors of midswitch fetuses is consistent with a discontinuous model for hemoglobin switching during ontogeny.
Animals↗
Temporal response of immunoreactive erythropoietin to acute hypoxemia in fetal sheep.
Acute hypoxemia was produced in chronically catheterized sheep fetuses to determine the response time necessary to increase plasma immunoreactive erythropoietin (Ep) concentration. Sodium nitrite (0.2 mM) was infused via a fetal vein to induce fetal hypoxemia. The resultant fetal methemoglobinemia was associated with a predictable, incremental decrease in arterial oxygen content. Twelve nitrite infusions were performed in eight fetal sheep preparations (gestational ages 115-146 days). Mean methemoglobin level increased to 33% of total Hb after 1-2 h of NaNO2 infusion. These results were compared to those obtained in nine control studies in eight fetuses in which no change was observed for plasma Ep, arterial oxygen content, PaO2, pHa, or whole blood lactate. In the nitrite infused group, however, a significant and progressive increase in mean plasma Ep level over baseline levels was observed during the 4th and 5th h of hypoxemia (p less than 0.01). This change in Ep was significantly greater compared to the control group. These results, however, were confounded by the concomitant development of a lactic acidemia secondary to the fetal hypoxemia. To examine the theoretic possibility that lactic acidemia may primarily affect fetal Ep levels, an additional group of five fetuses was infused with L-lactic acid for the same time period. Although the decrements in pHa and whole blood lactate levels achieved in these fetuses were in excess of those observed during the nitrite infusions, this possibility was ruled out since no change in fetal plasma Ep levels occurred. We conclude that during the 4th h of acute fetal hypoxemia a predictable, progressive increase in plasma Ep level is observed.(ABSTRACT TRUNCATED AT 250 WORDS)
Acidosis↗
Relationships among maternal and fetal amino acid blood concentrations and amniotic fluid amino acid levels in pregnant rhesus monkeys.
This study was designed to explore relationships among maternal and fetal amino acid blood concentrations and amniotic fluid amino acid levels in pregnant rhesus monkeys. Although there was no constant pattern for all amino acids in the three body fluids, we observed specific patterns for most neutral amino acids, imino acids, and acidic amino acids relative to their concentrations in maternal blood, fetal blood, and amniotic fluid. Moreover, there was no correlation between fetal phenylalanine blood levels and phenylalanine concentrations in amniotic fluid indicating that amniotic fluid phenylalanine levels would not be useful to monitor fetal phenylalanine blood concentrations during pregnancy.
Amino Acids↗
Bile duct varices.
The diagnosis of biliary duct varices and portal vein occlusion should be considered when nodular or notched defects in the wall of the biliary duct system are shown by cholangiography or when pedunculated vascular structures in the bile ducts are seen at surgery. We present two cases of common hepatic and common bile duct varices due to portal vein occlusion.
Adult↗
Fetal cardiovascular responses to asphyxia induced by decreased uterine perfusion.
Cardio-respiratory responses to asphyxia produced by decreased uterine perfusion were studied in 15 sheep fetuses. In chronic (spinal-anesthetized) and acute (inhalation-anesthetized) preparations, we measured fetal PO2, PCO2, pH, heart rate, arterial and umbilical venous pressures at rest and 5 min after controlled reductions of maternal aortic blood flow. Umbilical blood flow was determined by electromagnetic flow transducer on the fetal descending aorta with the iliac arteries ligated, in conjunction with radionuclide-labelled microspheres. In contrast to previous studies in which fetal hypoxaemia was produced by decreased maternally inspired O2 concentrations, decreasing degrees of uterine perfusion were associated with increasing degrees of hypercapnea and acidemia, as well as hypoxaemia. In chronic experiments, heart rate and umbilical blood flow fell significantly in response to decreased uterine perfusion with all degrees of hypoxaemia studied. In acute experiments, during the control period, PO2 values were similar to those of chronic experiments while values for pH and umbilical blood flow were lower and those for umbilical vascular resistance were higher. In the acute experiments, hypoxic stresses identical to those in the chronic studies failed to produce significant hemodynamic changes, except for bradycardia in response to severe hypoxaemia. These differences were apparently due to the pharmacologic effects of halothane and the operative stresses.
Anesthesia↗
Fetomaternal placental transfer mechanisms of aromatic amino acids in Macaca mulatta.
We investigated aromatic amino acid transfer mechanisms from fetus to mother in third-trimester pregnancies in rhesus monkeys after the administration of radioactive phenylalanine to the fetal circulation. The results indicated that fetomaternal transfer takes place mainly by facilitated diffusion via specific membrane carriers. This mechanism might participate in regulating amino acid concentrations in the fetus.
Amino Acids↗
Adrenal secretion of catecholamines during hypoxemia in fetal lambs.
A new method for quantifying adrenal secretory function in chronically catheterized fetal lambs was developed. This preparation included insertion of a catheter distally into the fetal left renal vein and placement of a remotely operated, hydraulically controlled choker around the renal vein at its junction with the vena cava. With the choker open, adrenal venous blood flowed into the renal vein and then into the vena cava. With the choker closed, adrenal blood flowed into the catheter so that timed samples of adrenal venous effluent could be obtained. With this technique, left adrenal secretory rates of norepinephrine and epinephrine were determined across a spectrum of oxygen concentrations in five near-term fetal lambs. There was a rapid rise in norepinephrine secretion after induction of hypoxemia. Maximum secretory rates occurred at about 5 min, concomitantly with the lowest attained fetal arterial partial pressure of oxygen (PO2s). There was an inverse exponential relation between these catecholamine secretion rates and fetal arterial PO2 (P less than 0.001). Norepinephrine secretion appeared to increase in response to lesser degrees of hypoxemia than did epinephrine, although a longer time delay between stimulation and epinephrine response may have been a factor. Overall, norepinephrine secretion was greater than that of epinephrine. The ratios of norepinephrine to epinephrine in individual adrenal samples varied considerably and in some instances were less than one. These ratios did not correlate significantly with the degree of hypoxemia. During 25 min of a relatively steady state of hypoxemia, norepinephrine secretion declined markedly after about 5 min, although it remained above control levels throughout. Epinephrine secretion rose more gradually but then was relatively stable during the remaining period of hypoxemia.
Adrenal Glands↗
Fetal polycythemia and hyperviscosity: effect on umbilical blood flow and fetal oxygen consumption.
To evaluate the effect of fetal polycythemia and hyperviscosity on fetal oxygen transport, we induced those conditions in eight chronically instrumented fetal lambs by isovolemic exchange transfusion with packed red cells obtained from a donor ewe. This procedure resulted in polycythemia and hyperviscosity without altering fetal arterial blood oxygen content. The fetuses were studied at 1 and 48 hours after polycythemia and hyperviscosity. In spite of decreased oxygen delivery to the fetus, the fetal oxygen consumption was unchanged because of an increase in oxygen extraction by the fetus.
Animals↗
Placental transfer of aromatic amino acids in non-human primates.
Macaca fascicularis (crab-eating monkeys) underwent an operative procedure at 120 to 130 days of pregnancy that allowed fetal blood sampling. During subsequent experiments L-phenylalanine and p-chlorophenylalanine were injected into the maternal circulation. Blood obtained from mother and fetus revealed that phenylalanine is actively transported across the placenta and hence is markedly increased in the fetus if the maternal blood phenylalanine concentration is below the "saturation" level of 1.82 mM to 2.12 mM. The results of these studies which provide a better understanding of placental transport mechanisms of aromatic amino acids will be of assistance in future management of pregnant phenylketonuric females.
Amino Acids↗
Evidence for a clonal model for hemoglobin switching.
The ontogenic switch from fetal to adult hemoglobin could be due to gradual replacement of fetal by adult erythroid progenitor cells, each with unique potential hemoglobin expression programs. We have studied globin synthesis in single colonies derived from the BFU-E of human newborn infants and rhesus monkey fetuses, both at the time of the switch. In the 140-day rhesus fetal colonies, beta synthesis ranged from 8% to 44% of (beta + gamma) in 47 colonies. When fetal colonies were arbitrarily defined as those with below 26% beta, and adult colonies those with above 26% beta, we predicted that there would be 12 adult colonies; 14 were observed. The rhesus fetal results were compatible with the presence of two or more classes of progenitors within the population seen at the time of the switch. In the human newborn study, the number of colonies increased fourfold from day 14 to day 21 in culture. beta synthesis also increased. These increases occurred even in cultures from which red, well-hemoglobinized colonies were completely removed as they appeared. New cohorts of late-appearing colonies were derived from immature progenitors. The early colonies showed correlation of G gamma and beta synthesis, but the late colonies did not show this correlation. We had found the latter pattern previously in adult, fetal-like colonies. Thus fetal progenitors in man have high levels of Hb F and G gamma, with correlation of these parameters at the level of single-progenitor-derived colonies; these fetal progenitors are found in fetuses and newborns. Adult, fetal-like progenitors have lower levels of Hb F and G gamma, without any correlation between the levels of each. The adult progenitors appear in newborn infants as the switch occurs, and they are the only class found in adults. Our observations in the simian and human studies support a clonal model for hemoglobin switching.
Animals↗