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Biomedical subjects

C Lincoln

Publications and source records attributed to C Lincoln.

At least 73 records · Page 4Linked to original sources
PubMed1991

Abnormal systolic atrioventricular flow related to incoordinate motion of the ventricular wall after the Fontan operation.

The development of abnormal flow has been described in patients with incoordinate motion of the ventricular wall. In all cases so far documented, these abnormal patterns of flow have been restricted to the ventricular cavity, and the atrioventricular valve remained closed. We identified a patient after a Fontan operation in whom the degree of ventricular mural incoordination was of such severity that the atrioventricular valve remained open and atrioventricular flow occurred for 140 msec after the onset of QRS complex. As far as we know, this phenomenon has not previously been described.

Child↗
PubMed1991

[Arterial switch operation in transposition of great arteries and double-outlet right ventricle. Experience at the Brompton Hospital, London].

Between 1981 and 1989 89 patients underwent anatomic correction of transposition of the great arteries with intact ventricular septum (n = 32), transposition with ventricular septum defect (n = 37) and double outlet right ventricle with subpulmonary ventricular septal defect (n = 20). The perioperative mortality was 17% (n = 15). The causes of death are discussed. The most common postoperative complication is right ventricular outflow tract-obstruction (RVOTO), accounting for two late deaths and necessitating reoperations in many patients. Besides RVOTO the mid-term results in arterial switch-operation are encouraging. Especially satisfactory are the absence of any problems with growth of the transferred coronary arteries, the function of the new aortic valve as well as the performance of the left ventricle. Of course, long-term experience is not yet available.

Cardiac Catheterization↗
PubMed1991

Cerebral perfusion and metabolism during profound hypothermia in children. A study of middle cerebral artery ultrasonic variables and cerebral extraction of oxygen.

Flow velocity of the right middle cerebral artery was studied in eight children during cardiac operations performed with profound hypothermia. Cerebral oxygen consumption was estimated by relating the difference in oxygen content between arterial and venous blood (jugular bulb) to flow velocity. In another six children, also during profound hypothermic procedures, the diameter of the middle cerebral artery was studied with an electronic echo-tracking instrument connected to a real-time ultrasound scanner. Flow velocity and estimated oxygen consumption decreased during cooling in proportion to the temperature decrease (r = 0.67, p less than 0.001, and r = 0.86, p less than 0.001, respectively), whereas the diameter was unaffected by temperature. At a nasopharyngeal temperature of 16.9 degrees +/- 1.9 degrees C flow velocity was reduced to 33.1% +/- 7.0% of the value obtained at 35 degrees C after induction of anesthesia. Correspondingly, the oxygen consumption decreased to 20.1% +/- 6.4%. The increase in oxygen consumption per 10 degrees C change in temperature was 3.6 (2.0 to 3.9) during surface cooling, 2.6 (1.9 to 2.7) during cardiopulmonary bypass cooling, and 2.7 (1.5 to 4.6) during rewarming. Flow velocity was not influenced by perfusion pressure during profound hypothermia within the range of 20 to 42 mm Hg (r = 0.14, p = 0.52) but was related to pump flow (r = 0.73, p less than 0.001). A pump flow down to 0.5 L/min/m2 was found to be adequate during stable profound hypothermia, as judged from the maintained high jugular bulb venous oxygen saturation (70% to 80%). It is concluded that flow velocity is reduced at hypothermia in proportion to the reduced metabolic rate, although modified by other factors that influence cerebral blood flow.

Blood Flow Velocity↗
PubMed1990

The potential for subpulmonary obstruction in complete transposition after the arterial switch procedure. An anatomic study.

Increasing experience with the arterial switch procedure has revealed that, in some instances, obstruction of the newly created sub-pulmonary outflow tract is a major problem. In this study, we examined the right ventricular outflow tract in 51 specimens of complete transposition, 18 of which were associated with a ventricular septal defect. We focussed our attention on the musculature which made up the outflow region and considered variations from that found in the normal right ventricle. Our gross observations showed differences in morphology which produced a sharper angulation between inflow and outflow when compared to the normal. Discrete outflow obstruction was found in 11 hearts (8 with ventricular septal defect and 3 with an intact ventricular septum). The obstruction was due to deviation of the outlet septum in 5, and anomalous muscle bundle in 1, hypertrophy of septomarginal and septoparietal trabeculations in 3 and circumferential infundibular hypertrophy in 2 hearts. Coexisting obstruction of the left ventricular outflow was present in 3 hearts. The anatomical substrates of discrete obstruction should be identified by preoperative cross-sectional echocardiography and/or angiography. Modifications in surgical techniques or radical resection of the obstructing musculature could then be performed to avoid the problem of subpulmonary obstruction after the arterial switch procedure.

Heart Septal Defects, Ventricular↗
PubMed1990

Growth and development of the axr1 mutants of Arabidopsis.

We have recovered eight new auxin-resistant lines of Arabidopsis that carry mutations in the AXR1 gene. These eight lines, together with the 12 lines described in a previous report, define at least five different axr1 alleles. All of the mutant lines have a similar phenotype. Defects include decreases in plant height, root gravitropism, hypocotyl elongation, and fertility. Mutant line axr1-3 is less resistant to auxin than the other mutant lines and has less severe morphological abnormalities. This correlation suggests that the morphological defects are a consequence of a defect in auxin action. To determine whether the altered morphology of mutant plants is associated with changes in cell size or tissue organization, tissue sections were examined using scanning electron microscopy. No clear differences in cell size were observed between wild-type and mutant tissues. However, the vascular bundles of mutant stems were found to be less well differentiated than those in wild-type stems. The auxin sensitivity of rosette-stage plants was determined by spraying plants with auxin solutions. Mutant rosettes were found to be significantly less sensitive to exogenously applied auxin than wild-type rosettes, indicating that the AXR1 gene functions in aerial portions of the plant. Our studies suggest that the AXR1 gene is required for auxin action in most, if not all, tissues of the plant and plays an important role in plant development. Linkage studies indicate that the gene is located on chromosome 1 approximately 2 centiMorgans from the closest restriction fragment length polymorphism.

Drug Resistance↗
PubMed1990

Exercise ability after Mustard's operation.

Twenty children who were well six to 12 years after undergoing Mustard's operation for transposition of the great arteries were studied. Each child performed a graded maximal treadmill test with measurements of gas exchange and oxygen saturation, and had electrocardiography carried out. Nineteen were also catheterised, and oxygen consumption was measured so that pulmonary and systemic flow could be calculated. Compared with 20 age and size matched controls, seven of the patients had normal exercise tolerance (as judged by a maximal oxygen consumption of greater than 40 ml/kg/min), 10 showed a moderate reduction (30-39 ml/kg/min), and three were more seriously limited. None of the patients with normal exercise tolerance had obstruction of venous return but six of those with mild impairment of exercise ability had partial or complete obstruction of one or both of the vena cavas. More severe limitation was associated with pulmonary vascular disease and fixed ventricular outflow tract obstruction. Formal exercise testing of apparently well children who have undergone Mustard's operation identifies those with haemodynamic abnormalities that may require intervention.

Adolescent↗
PubMed1990

Open valvotomy for critical aortic stenosis in infancy.

Over a 5 year period open valvotomy was performed on 13 patients under the age of one year with critical aortic stenosis. All 13 survived operation. There were two late deaths--one 38 days after operation, associated with an unrelated neurosurgical procedure and the other 2 years 6 months after when aortic root enlargement and replacement of the aortic valve were performed. During this period two other infants presented with aortic stenosis. One, who was very ill before transfer, died before operation could be performed. The second patient had a hypoplastic left ventricle with a small mitral valve ring and was, therefore, considered to be part of a different subgroup. All the surviving children have been followed up (median length of follow up 2 years and 11 months, range 7 months-5 years). Left ventricular function, in terms of percentage systolic wall thickening, was shown to be significantly impaired in all age groups. Peak diastolic thinning was abnormal in those children aged from 3 to 5. The aortic valve gradient, as assessed by peak instantaneous continuous wave Doppler, was less than 40 mm Hg in five patients and between 40 and 70 mm Hg in seven patients. One patient, with appreciable restenosis, has undergone successful percutaneous balloon dilatation of the aortic valve.

Aortic Valve↗
PubMed1990

Brain type creatine kinase in relation to oxygen desaturation in the blood of children with congenital heart disease.

The concentration of brain type creatine kinase (CK-BB) was measured in blood from the internal jugular vein in 32 children (less than 1 year old) with congenital heart disease. In transposition of the great arteries the CK-BB levels were significantly higher than in children without cyanosis (10.1 +/- 4.1 vs. 3.0 +/- 0.5 ng/ml). A negative correlation was found for CK-BB concentration and arterial oxygen saturation (r = -0.41, p less than 0.02 for all children and r = -0.62, p less than 0.05 for those with tetralogy of Fallot). It is suggested that the increased CK-BB levels in the blood of cyanotic children reflect chronic cerebral hypoxia, which may explain other reports of reduced psycho-intellectual function in patients with cyanotic heart disease.

Brain↗
PubMed1990

Options for surgical repair in hearts with univentricular atrioventricular connection and subaortic stenosis.

Thirteen patients have undergone surgical treatment because of subaortic obstruction in hearts with a univentricular atrioventricular connection. Nine patients underwent surgical enlargement of the ventricular septal defect and four patients had construction of an aortopulmonary anastomosis and closure of the pulmonary trunk (the Damus-Kaye-Stansel procedure). Two patients undergoing enlargement of the septal defect and two having the Damus-Kaye-Stansel procedure also had a modified Fontan procedure. One patient had complete atrioventricular dissociation after direct enlargement of the ventricular septal defect, which necessitated insertion of an epicardial pacemaker. One patient died within 30 days of the operation after enlargement of the defect and two patients after the Damus-Kaye-Stansel procedure. There was one late death, occurring in a patient who underwent enlargement of the ventricular septal defect. Ten patients have subsequently undergone conventional cardiac catheterization and angiography or transcutaneous Doppler flow studies to assess the relief of the subaortic obstruction. The result has been satisfactory in all. Because of this experience, we now recommend direct surgical enlargement of the restrictive ventricular septal defect for direct relief of subaortic stenosis occurring with a univentricular atrioventricular connection to a dominant left ventricle, inasmuch as it appears to be hemodynamically effective with a low operative mortality and morbidity. The Damus-Kaye-Stansel procedure can also have a role in relieving subaortic stenosis when the atria are connected to a dominant right ventricle.

Aortic Valve Stenosis↗
PubMed1990

The effect of propranolol on the cerebral electrical response to deep hypothermia and total circulatory arrest in lambs.

Deep hypothermia with total circulatory arrest is an important technique in the surgical treatment of complex congenital heart defects. The effects of propranolol on cerebral electrical activity in lambs undergoing a 90-minute period of circulatory arrest after initial surface cooling to 26 degrees C and subsequent core cooling to 15 degrees C was studied by means of the cerebral function analyzing monitor. Five of the lambs were pretreated with intravenous propranolol 0.2 mg/kg (group I) and five acted as controls (group II). The surface cooling phase was associated with a continuous decrease in mean electroencephalographic voltage +/- standard error, which decreased from 82.8 +/- 11.8 microV at 37 degrees C to 31.6 +/- 2.4 microV at 26 degrees C in the control group compared with 75.0 +/- 7.4 microV and 63.2 +/- 9.2, respectively, in the propranolol group (p less than 0.05). During the rewarming phase, the latency to (1) initial appearance of electrical activity, (2) continuous recording with the cerebral function analyzing monitor, and (3) maximum voltage and frequency recovery was 2.0 +/- 1, 5.9 +/- 4, and 32.4 +/- 8 minutes in the propranolol group, which was significantly (p less than or equal to 0.01) shorter than in the control group (18.4 +/- 3, 38.2 +/- 5, and 111.0 +/- 9 minutes, respectively). These results suggest that pretreatment with propranolol may play an important part in the brain tolerance to deep hypothermia and circulatory arrest.

Animals↗
PubMed1989

Is cerebral blood flow/metabolic mismatch during rewarming a risk factor after profound hypothermic procedures in small children?

The relation between cerebral blood flow and oxygen consumption was studied in six children during cardiac operations with profound hypothermia. A combination of topical cooling and core cooling was used to reduce the nasopharyngeal temperature to 15 degrees C. The alpha-stat principle for pH management was used. Blood flow and oxygen consumption decreased significantly with temperature. At a nasopharyngeal temperature of 15 degrees C, blood flow was reduced to 25% of the awake level, corresponding to 34% of the asleep value obtained 15-30 min after intubation. Oxygen consumption decreased to 25% of the asleep value. During stable profound hypothermia, venous saturation in the jugular bulb was at the same level as 15 min after intubation (70%). Markedly lower values were observed during topical cooling, and particularly during rewarming (down to 21%), indicating a mismatch between cerebral blood flow and oxygen consumption. The speed of rewarming correlated with the fall in venous oxygen saturation (rs = 0.82, P less than 0.05). It is suggested that periods of cerebral blood flow/metabolic mismatch during topical cooling and rewarming may explain postoperative cerebral dysfunction after deep hypothermic procedures. A moderate speed of rewarming is advocated.

Blood Flow Velocity↗
PubMed1989

The pathophysiology of atypical tamponade in infants undergoing cardiac surgery.

A small solid state transducer was used to measure pericardial pressure (PP) in 13 pediatric patients (mean age 18 months) at hourly intervals for 24 h following cardiac surgery. The mean PP following closed cardiac surgery via a left thoracotomy (group 1: 5 patients) was 2.7 +/- 1.4 mmHg and did not change with time. Maximum PP occurred during isovolumic relaxation of the ventricle rising to a peak at the onset of the 'a' wave of the central venous pressure (CVP). PP was strongly correlated with CVP (r = 0.58, P less than 0.001) but not with airways pressure (r = 0.27, P less than 0.2). Mean PP in the 3 patients undergoing transatrial surgery (group 2) was 4.5 +/- 2.7 mmHg (group 1 vs group 2, P less than 0.001). PP was significantly raised in the 2 patients undergoing transventricular correction of Fallot's tetralogy (group 3, PP = 10.2 +/- 3.2 mmHg; group 3 vs group 2, P less than 0.001) and in the 3 patients undergoing homograft conduit reconstruction of the right ventricular outflow tract for truncus arteriosus (group 4, PP = 9.3 +/- 2.6 mmHg; group 4 vs group 2, P less than 0.001). The results confirm that PP is a mathematical function of the expansile forces of the heart and the restricting forces of the pericardium and mediastinum. Patients with pulmonary regurgitation or pulmonary hypertensive crisis leading to increased right ventricular end diastolic dimension or a space occupying conduit have a high PP and are therefore at risk of atypical tamponade. In this situation splinting open the chest may reduce PP and break the cycle of falling cardiac output.

Cardiac Tamponade↗
PubMed1989

Does the endoscope control head need to be disinfected between examinations?

An evaluation was made of the incidence of contamination of endoscope control heads during gastroduodenoscopy and colonoscopy, and of the efficacy of a simple disinfection technique. Contamination of the control heads occurred in 4 out of 17 examinations. Scrubbing in detergent followed by wiping with swabs impregnated with 70% isopropyl alcohol and 2% chlorhexidine achieved adequate disinfection of artificial heavy contamination of the control head. The endoscope control head represents a potential source of cross-infection and should not be neglected in any cleaning procedure.

1-Propanol↗
PubMed1989

No flow or low flow? A study of the ischemic marker creatine kinase BB after deep hypothermic procedures.

Twenty-seven children with complex congenital heart malformations necessitating early repair were studied before and after deep hypothermic procedures. The children were allocated into two groups. One group underwent total circulatory arrest (40 +/- 6 minutes). In the other group perfusion was maintained during deep hypothermia but reduced a 25% of normal at normothermia. The temperature was reduced to 15 degrees C (nasopharynx) in both groups with a combination of topical and core cooling. To study cerebral injury, were made serial measurements of creatine kinase isoenzyme BB from arterial samples before and for 8 hours after the deep hypothermic procedure. Creatine kinase isoenzyme BB increased after both procedures from 4.3 +/- 0.9 ng/ml to 10.4 +/- 1.8 ng/ml in the circulatory arrest group and from 2.8 +/- 0.7 ng/ml to 9.9 +/- 1.9 ng/ml in the low-flow group (no significant difference). The results were analyzed in relation to age, size, study group, hemoglobin, blood glucose, and blood gases. The creatine kinase BB levels were positively related to preoperative hemoglobin and blood glucose values before the hypothermic procedures.

Blood Glucose↗
PubMed1989

Elective deep hypothermia with total circulatory arrest: changes in plasma creatine kinase BB, blood glucose, and clinical variables.

Serial measurements of a marker of brain ischemia, creatine kinase isoenzyme BB, were performed in arterial and internal jugular venous blood from 20 infants younger than 1 year of age before and during the first 20 hours after deep hypothermic total circulatory arrest procedures. A two-site monoclonal method was used, and the results were analyzed in relation to age, size, type of cardiac lesion, hemoglobin level, blood glucose level, pH, and duration of the total circulatory arrest. The creatine kinase BB concentrations increased after the arrest, more so in venous than in arterial blood, from 3.2 +/- 0.5 ng/ml to 17.5 +/- 4.5 in arterial blood and from 3.5 +/- 0.5 ng/ml to 18.1 +/- 5.8 in venous blood. Arterial-venous concentration differences correlated with venous concentrations (r = 0.92, p less than 0.01). The duration of the arrest correlated with creatine kinase BB concentrations during reperfusion with correlation coefficients between 0.50 to 0.90 depending of what sequence of the 20-hour sampling period was analyzed. The best correlation was obtained during the first 4 hours of reperfusion. Age, size of the child, and preoperative cyanosis correlated with postoperative creatine kinase BB but were less important than the arrest time, blood glucose level (r = 0.62, p less than 0.01), pH (r = -0.78, p less than 0.01), and hemoglobin level (r = 0.76, p less than 0.01) during reperfusion. It is suggested that a different control of blood glucose level and pH during reperfusion may be of importance to reduce biochemical signs of cerebral dysfunction after deep hypothermic total circulatory arrest procedures.

Blood Glucose↗
PubMed1988

Plasma histamine profiles in paediatric cardiopulmonary bypass.

We have previously reported our findings of very high plasma histamine levels in the extracorporeal blood primes of infants undergoing cardiopulmonary bypass (CPB) for correction of congenital cardiac defects and have now extended this enquiry to examine the whole peri-operative period. In this preliminary study, samples of blood for plasma histamine were drawn from a mixed group of congenital cardiac patients featuring varying degrees of cyanosis, differing hypothermic operative conditions and utilising two oxygenator systems. Despite the diversity of this group a common pattern of histamine release emerged with a clear origin at the commencement of bypass, and continuing during the operative period. Our results suggest that priming procedures using stored donor blood provide a major contributing source of histamine release with inevitable deleterious consequences to the post-operative outcome.

Cardiopulmonary Bypass↗
PubMed1988

The clinical significance of elevated CSF and plasma histamine in cerebral aneurysm surgery utilizing cardiopulmonary bypass with total circulatory arrest.

Recently there has been a renewed interest in the neurosurgical treatment of large cerebral aneurysms and AV malformations utilising cardiopulmonary bypass (CPB) and total circulatory arrest (TCA). However, the differing tolerance limits of coagulation and bleeding, pH control and fluid constraint are difficult to reconcile. Although clinical assessment, electro encephalogram (EEG) and intracranial pressure-monitoring assist in identification of cerebral damage, CPB and TCA inflict their own penalties with resultant uncertainty in post-operative neurological evaluation, and producing difficulties in interpretation and management. Additionally, an unanswered question is, to what extent the known cardiac and cerebral effects of circulating histamine might influence the post-circulatory arrest recovery in these patients, and whether this would further compromise the neurological result. We report our experience of 9 such cases who underwent this procedure, and were able to achieve a satisfactory neurological result in 7 patients with differing lesions. During the operation both CSF (from the open cranium) and blood (from the right internal jugular vein) were sampled at intervals for subsequent plasma histamine estimation. Despite markedly elevated histamine levels during CPB and TCA, this was not associated with an unfavourable neurological outcome. These early findings have given us encouragement to the useful role of CPB and TCA in these complex neurosurgical presentations, and raise interesting questions about the clinical importance of histamine-evoked cerebral ischaemia that has been demonstrated in experimental models.

Adult↗