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Biomedical subjects

D Sidi

Publications and source records attributed to D Sidi.

At least 217 records · Page 12Linked to original sources
PubMed1983

Developmental changes in oxygenation and circulatory responses to hypoxemia in lambs.

We studied moderate [fractional inspired O2 (FIO2) 0.09] and severe (FIO2 0.06) hypoxemia in 21 lambs (group 1, 1 wk old; group 2, 3-4 wk old; group 3, 5-7 wk). With moderate hypoxemia, all groups increased heart rate, cardiac output, and pulmonary arterial pressure and decreased systemic and pulmonary vascular resistance; cardiac output and pulmonary arterial pressure increases were less in group 1, because of higher resting values. With severe hypoxemia, heart rate increased similarly, cardiac output was unchanged, and aortic pressure fell associated with severe metabolic acidosis or arrhythmias. Regional blood flow changed similarly in all groups; heart and brain flow increased, carcass flow was unchanged, and skin, GI tract, and kidney flow fell. O2 consumption (VO2) and mixed venous PO2 decreased, though O2 saturation was higher in group 1 due to the lower O2 half-saturation pressure of hemoglobin. With a given decreased VO2 there was more metabolic acidosis in older lambs and an increased VO2 after termination of hypoxemia, suggesting greater O2 debt. As in the fetus, young lambs are better able to tolerate a decreased VO2 than older lambs.

Aging↗
PubMed1983

Effects of ambient temperature on oxygen consumption and the circulation in newborn lambs at rest and during hypoxemia.

To assess the effects of environmental temperature on responses to hypoxemia, we studied five unsedated lambs in the first week after birth. We catheterized the carotid artery and pulmonary artery (via the jugular vein). After recovery of at least 1 day, we measured pH, blood gases, arterial and mixed venous blood O2 content, oxygen consumption (VO2), heart rate, carotid and pulmonary arterial pressures, and cardiac output in both warm (25 degrees C) and cool (17.4 +/- 1.1 degree C) environments. In the cool environment, with no shivering, VO2 increased 40% (14.9 to 20.8 ml/kg/min). There were also increases of arteriovenous blood O2 content difference of 19%, cardiac output of 18%, and heart rate of 14%. In four lambs, we studied the same variables during hypoxemia (FiO2 = 0.09 for 1 h) at both temperatures. In the cool environment, hypoxemia produced a greater fall of VO2 (26% versus 6%) and arteriovenous oxygen differences (30% versus 19%) and a smaller increase of cardiac output (8% versus 14%) and heart rate (26% versus 43%). Also in the cool environment, core temperature decreased more (2.1 versus 0.4 degree C), but base deficit was the same (-6 versus -5 mEq/liter). Despite the greater fall in VO2 during hypoxemia in the cool environment, the lowest value achieved was still higher than the level during normoxemia in the warm environment. Similarly, cardiac output during hypoxemia was greater in the cool than in the warm environment. These findings may explain the variability in reported normal resting values and responses to hypoxemia. Contrary to previous reports, they also indicate that during severe hypoxemia neonates have a decreased reserve of metabolic and cardiovascular responses in a cool compared with a warm environment.

Animals↗
PubMed1983

[Problems posed by preparation of the left ventricle for anatomical correction in simple transposition of the great vessels].

Surgical correction of simple transposition of the great arteries by arterial detransposition can only be considered if the left ventricle is capable of functioning under systemic conditions. This is possible at birth but the operation is too big for it to succeed. After a few weeks the left ventricle may lose this capacity but it can be induced to redevelop if it is given a systolic stress by pulmonary banding. This was attempted initially in 30 children aged from 5 weeks to 3,5 years old (20 aged less than 2 months) but had to be abandoned for the following reasons: 8 immediate failures due to severe hypoxia and acidemia, 7 left ventricular failures, mainly in 3 children operated after 6 months of age; 7 severe hypoxemias, 5 pulmonary arterial lesions due to banding and/or the systemo-pulmonary anastomosis associated in some cases; in all, there were 8 failures out of the 17 anatomical corrections performed to date in 22 survivors of banding. The criteria of left ventricular readaptation after banding were difficult to determine. The final result did not appear to be related to either the duration of banding, the degree of aortic desaturation, the ratio of ventricular pressures, or to the various echocardiographic indices. Only the initial hypoxemia (less than 50 p. 100 saturation) with respect to the risk of banding, and the age at which banding was performed (over 6 months) with respect to the risk of anatomical correction, appeared to be obvious risk factors. This is the reason for a new protocol at present under study to try to maintain left ventricular growth by banding in the first days of life, so to ensure a more harmonious and effective, and also less dangerous preparation for anatomical correction. Six new born children have been "prepared" in this way: three had adequate loose banding and underwent atrial correction. Very good results were obtained in the other three patients who have already undergone detransposition at 2,5 and 3 months with excellent immediate results. We believe that neonatal pulmonary banding (before 5 days) when aortic saturation after atrioseptostomy is over 50 p. 100, provides a real alternative to the classical methods of treating simple transposition of the great arteries (Mustard or Senning). Anatomical correction can then be carried out a few weeks later under good conditions.

Angiocardiography↗
PubMed1983

[Infection of an anastomosis: a formidable complication of operations for aortic coarctation].

One 12 day newborn, a 2 year old infant and two children aged 10 and 14, operated for isthmic coarctation of the aorta by three different surgical techniques (resection-anastomosis, angioplasty with an autograft, prosthetic graft) suffered infection of the operative field, resulting in septicemia (3 staphylococcal and 1 yeast infections). The aorta ruptured after 4 days, before any collection of pus in the newborn but a mycotic false aneurysm developed in the three other patients: this was the cause of death by aortic rupture during the 5th postoperative week in one case but was diagnosed and operated successfully in the other two, 13 and 54 days after their first operation. These complications are well known. Therefore, these patients should be closely followed up for at least one month. The occurrence of pyrexia, even slight or late, should be treated with suspicion. Characteristic dilatation of the part of the aorta operated on should be actively looked for by simple radiography, 2D echocardiography and, when in doubt, right heart angiocardiography. The diagnosis is a surgical emergency: the safest technique consists in initially establishing an aorto-aortic deviation by a right sided approach followed by exclusion of the lesion. Surgery is the only means of preventing catastrophic rupture of the aorta.

Adolescent↗
PubMed1982

Comparison of methods of measuring cardiac output in newborn lambs.

To define agreement between methods, we measured cardiac output (CO) in chronically instrumented lambs by four different methods. In 23 lambs we measured CO simultaneously by the Fick and microsphere methods and with an electromagnetic flowmeter over a wide range of CO (80-454 ml/kg/min) in different experimental conditions on 97 occasions. When the electromagnetic flowmeter was corrected for coronary flow (about 8% of CO) calculated from microspheres, the mean cardiac outputs were almost identical for these three methods (237, 235, and 236 ml/kg x min, respectively). Comparisons between any two of the methods showed a correlation coefficient greater than 0.89. In four lambs, 52 measurements of CO by Fick and thermodilution had a correlation coefficient of 0.94. We conclude that any of the four methods, if appropriately applied, adequately measures CO in a variety of circumstances and may be used with confidence for physiologic or other studies.

Animals↗
PubMed1982

Recovery of cardiovascular function in newborn lambs after thoracotomy.

Knowledge of the quality and speed of recovery after thoracotomy is crucial for studies of the early changes in cardiovascular function in the neonatal period. We studied the early recovery period after thoracotomy with pericardiotomy, but without ventriculotomy, in 21 lambs operated on between 2-24 days after birth. In 15 lambs, we measured resting pH,, PaO2, PaCO2, O2 consumption, cardiac output, heart rate, and aortic and pulmonary arterial pressures, before and after thoracotomy, daily for 1 wk. We found that, except for PaO2 (82 versus 87 torr), all variables returned to normal by the third day after thoracotomy. Four lambs were exposed to hypoxia (FIO2 0.09 for 1 h) before and 3 days after thoracotomy; hypoxia-induced changes were not different at the two different periods. Six other lambs, undergoing thoracotomy within the first 3 days after birth and exposed to hypoxia on the third postoperative day, had hypoxia-induced responses similar to six age-matched nonthoracotomized lambs. These findings indicate recovery of cardiovascular function by 48-72 h after thoracotomy. We believe, therefore, that reliable studies of the circulation in lambs are possible as early as 3-4 days after birth, even if thoracotomy is required for making measurements.

Age Factors↗
PubMed1982

["Straddling" tricuspid valve across an isolated ventricular septal defect. Apropos of 4 cases].

Four cases of children from 10 months to 3 years of age with isolated ventricular septal defects and straddling tricuspid valve are reported. Three patients underwent surgery (mean age: 24 months). The lesion was diagnosed during operation in 2 cases. The VSD was a perimembranous defect with extension to the ventricular inlet in 2 cases, and in the other it was entirely muscular. The straddling involved all the septal leaflet of the tricuspid valve in 1 case. In two cases, there was doubling of the segment with one part crossing the VSD. The left ventricular attachment was a type B in 2 patients and type C in 1 patient. The tricuspid ring was normally situated in all patients (no overriding). In 2 patients, the diagnosis was made with the aid of complementary investigations, and, in particular, 2D echocardiography. One of these patients has not yet undergone surgery as the lesion is well tolerated and because of associated mitral regurgitation. In 3 patients, surgery consisted of repairing the ventricular septal defect, leaving the abnormal part of the tricuspid valve in the left ventricle. All patients survived; there were no cases of post-operative atrioventricular block or signs of tricuspid incompetence. With reference to these three cases, the authors review the main anatomical lesions, the diagnostic signs and different methods of treatment of this condition. Straddling tricuspid valve may present as a simple ventricular septal defect. This diagnosis should be considered in all cases of posterior ventricular septal defects.

Angiography↗
PubMed1981

[Treatment of ventricular septal defects with pulmonary hypertension in infancy (author's transl)].

188 infants presenting with ventricular septal defects associated with pulmonary hypertension underwent early surgical treatment. Overall death rate was 10% (6% since 1979 and even 0% in case of single defects operated on between the ages of 6 and 12 months). Surgical results were excellent in 48 controlled cases operated on during the 1st year of life. When surgery was performed later, risk of residual pulmonary hypertension remained in cases with equal pressure levels. Our results suggest that all the infants who do not respond properly to medical treatment must be operated on and that those with a major pulmonary hypertension have to be operated on during there second semester of life.

Heart Septal Defects, Ventricular↗
PubMed1978

[Long-term results of 156 Mustard operations for simple transposition of the great vessels].

156 children with simple transposition of the great vessels have been operated on by Mustard's technique between 1-6-1967 and 31-12-1976, with an immediate overall mortality rate of 8%. In the longterm, the 9% of late deaths and more especially the complications are regrettable; complications were either of severe arrhythmia (almost 30%) leading to 2 late deaths and 7 pacemaker implantations, or venous obstruction relating to problems with the patch (25%). Despite the improved techniques and consequent reduction in surgical mortality and late complications, longterm prognosis is still unsure because of the unknown fate of the intra-atrial partition, and that of the "passive" rhythms which are so commonly found after this type of surgery.

Adolescent↗
PubMedDate not supplied

Three-dimensional echocardiographic measurement of left ventricular stroke volume in children: comparison with Doppler method.

Three-dimensional echocardiography (3DE) allows calculation of ventricular volumes without geometric assumption on the ventricular shape. Our aim was to apply 3DE in a normal pediatric population and to compare the left ventricular stroke volume measurements to the Doppler method. Twenty-four normal patients (median age 7 years) underwent Doppler echocardiography and 3DE for left ventricular stroke volume calculation. The left ventricular stroke volume by Doppler method was calculated as the product of the aortic Doppler flow mean velocity and the area of the aortic annulus. The 3DE method was performed using a transthoracic rotational probe (TomTec) and left ventricular volumes were calculated using the Simpson's rule. The mean time for 3DE acquisition was 90 seconds without any sedation. 3DE correlated well with the Doppler method for left ventricular stroke volume measurements (y = 0.8x - 0.2, r = 0.94). The mean difference between the average values of left ventricular stroke volume obtained by Doppler method and 3DE was 5 +/- 4 ml. Intraobserver and interobserver variabilities in the left ventricular stroke volume measurement by 3DE were 2.6% and 4.4%. In conclusion, 3DE compared to the Doppler method is an accurate, noninvasive, and reproducible method to measure the left ventricular stroke volume in normal children.

Adolescent↗