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Biomedical subjects

F M Clements

Publications and source records attributed to F M Clements.

At least 19 recordsLinked to original sources
PubMed2000

Transesophageal echocardiography in quantification of emboli during femoral nailing: reamed versus unreamed techniques.

We quantified the embolic load to the lungs created with two different techniques of femoral nailing. Eleven patients with 12 traumatic femur fractures were randomized to reamed (7 fractures) and unreamed (5 fractures) groups. Intramedullary nailing was with the AO/ASIF* universal reamed or unreamed nail. Transesophageal echocardiography (TEE) was used to evaluate the quantity and quality of emboli generated by nailing. Data were analyzed using software that digitized the TEE images and quantified the area of embolic particles in each frame. The duration of each level of embolic phenomena (zero, moderate, severe) was used to determine total embolic load with various steps (fracture manipulation, proximal portal opening, reaming, and nail passage). Manual grading of emboli correlated highly with software quantification. Our data confirm the presence and similarity of emboli generation with both methods of intramedullary nailing. Unreamed nails do not protect the patient from pulmonary embolization of marrow contents.

Adolescent↗
PubMed1999

Comparison of direct aortic and femoral cannulation for port-access cardiac operations.

BACKGROUND: Differences in outcome after direct aortic cannulation (AORT) in the chest versus standard femoral arterial cannulation (FEM) have not been defined for minimally invasive cardiac operations utilizing the port-access approach. METHODS: A retrospective study was performed of 165 patients undergoing port-access cardiac mitral valve operation (n = 126) or coronary artery bypass grafting (n = 39). In 113 patients, FEM was used, while in 52 patients, AORT was accomplished through a port in the first intercostal space. RESULTS: AORT eliminated endoaortic balloon clamp migration (0/36 [0%] vs. 17/95 [18%]), and groin wound or femoral arterial complications (0/52 [0%] vs. 11/113 [10%]) without changing procedure times (363+/-55 vs. 355+/-70 minutes). Complications attributable to AORT were injury to the right internal mammary artery and aortic cannulation site bleeding in 1 patient each. CONCLUSIONS: Direct aortic cannulation is technically easy, allows use of an endoaortic clamp, and avoids aorto-iliac arterial disease, the groin incision, and possible femoral arterial injury associated with femoral arterial cannulation. Direct arterial cannulation should expand the pool of patients eligible for port-access operation, and may become the standard for port-access procedures.

Adult↗
PubMed1998

Cardiopulmonary bypass time does not affect cerebral blood flow.

BACKGROUND: A time-dependent decline in cerebral blood flow (CBF) has been reported in cardiac surgical patients despite stable pump flows and arterial carbon dioxide tension. Other studies have failed to support these hypothermic cardiopulmonary bypass (CPB) results, showing preservation of CBF during CPB. The purpose of the study was to define the influence of mildly hypothermic CPB duration on CBF. METHODS: Cerebral blood flow was measured using xenon-133 washout and alpha-stat blood gas management during nonpulsatile CPB. Cerebral blood flow measurements were made after the initiation of CPB and near the end of bypass during pump flows of 2.4 L.min-1.m-2. RESULTS: Fifty-two coronary artery bypass patients were studied. The average time between CBF measurements was 54 +/- 20 minutes (mean +/- standard deviation), with a range of 10 to 100 minutes. Temperature and arterial carbon dioxide tension were controlled: after the initiation of CPB, temperature was 35.5 degrees +/- 0.4 degree C and carbon dioxide tension was 37 +/- 2.8 mm Hg; whereas near the end of bypass temperature was 35.6 degrees +/- 0.5 degree C and carbon dioxide tension was 36 +/- 2.3 mm Hg. We found no correlation between CBF and time on CPB (p = 0.47; r = 0.101), in contrast to other studies suggesting that CPB duration may intrinsically affect CBF. CONCLUSIONS: Our experimental results include the following: (1) during mildly hypothermic bypass, CBF does not decrease in relation to time and (2) cerebral flow-metabolism coupling is intact at 35 degrees C.

Blood Pressure↗
PubMed1996

Effect of perfusion pressure on cerebral blood flow during normothermic cardiopulmonary bypass.

BACKGROUND: We have recently shown that during hypothermic cardiopulmonary bypass (CPB), cerebral autoregulation has a positive slope such that for every 10 mm Hg change in pressure, a 0.86 mL.100 g-1.min-1 change in cerebral blood flow (CBF) is predicted. The purpose of this study was to define the influence of mean arterial blood pressure (MAP) on CBF during normothermic CPB. METHODS AND RESULTS: CBF was measured by use of 133Xe washout and alpha-stat blood gas management during nonpulsatile CPB. CBF measurements were made at a pump flow of 2.4 L.min-1.m-2 at stable normothermia and approximately 15 minutes later after the MAP was increased or decreased > or = 20%. A third data set was recorded after the pressure was returned to the initial value. Forty-five patients were entered into the study. Temperature was held constant. We found a significant effect (P = .016) of change in MAP on change in CBF during normothermic CPB. For a 10 mm Hg increase in MAP, an increase in CBF of 1.78 mL.100 g-1.min-1 is predicted. Along with change in CBF, significant increases in both cerebral metabolic rate and cerebral oxygen delivery were observed. CONCLUSIONS: This information, along with our previous data shows that autoregulation during CPB has a positive slope that is greater with normothermia than hypothermia. Although it is unlikely that these small changes in flow are an important primary effect in the development of hypoperfusion, increased metabolic rate with increased CBF may indicate pressure-dependent collateral flow potentially in regions embolized during CPB.

Adult↗
PubMed1995

Cerebral physiologic effects of burst suppression doses of propofol during nonpulsatile cardiopulmonary bypass. CNS Subgroup of McSPI.

Central nervous system (CNS) complications are common after cardiac surgery. Death due to cardiac causes has decreased, but the number of deaths due to CNS injury has increased. As a first stage in the evaluation of its cerebral protection potential, we evaluated the cerebral physiologic effects of burst suppression doses of propofol during nonpulsatile cardiopulmonary bypass. Thirty patients without history of cerebral vascular disease were randomized to two study groups: control group (n = 15) who received sufentanil and vecuronium, or propofol group (n = 15) who received the control anesthetic and propofol infused to maintain electroencephalogram (EEG) burst suppression. Catheters were placed in the radial artery and right jugular bulb for sampling of systemic arterial and jugular bulb venous blood. 133Xe clearance was used to determine cerebral blood flow (CBF) at the start of normothermic bypass, during stable hypothermia, and when rewarmed to 35-37 degrees C nasopharyngeal temperature. Pharmacologic burst suppression with propofol produced a statistically significant reduction in CBF, cerebral oxygen delivery (DO2), and cerebral metabolic rate (CMRO2) at each measurement interval (P < 0..05 vs control). Cerebral arterial venous oxygen difference (C(a-v)O2), and jugular bulb venous oxygen saturation (SJvO2) were not statistically different between groups, indicating maintenance of cerebral metabolic autoregulation (coupling). The reduction in CBF and CMRO2, prominent during the normothermic phases of cardiopulmonary bypass (CPB), indicates a potential for propofol to reduce cerebral exposure to the embolic load during CPB.

Aged↗
PubMed1995

Revascularization of the internal mammary artery after coronary artery bypass grafting.

Symptomatic anterior myocardial ischemia as a result of stenosis at the origin of the left internal mammary artery developed in a patient who underwent prior coronary artery bypass grafting using the left internal mammary artery as a conduit. Successful revascularization of the left anterior descending coronary artery was achieved using a reversed saphenous vein bypass graft from the left common carotid artery to the proximal internal mammary artery. This approach provided myocardial revascularization and avoided reoperative median sternotomy.

Aged↗
PubMed1992

Quantitative analysis of regional wall thickening by transesophageal echocardiography.

To develop a method for quantitative analysis of regional left ventricular function from transesophageal two-dimensional echocardiograms, we conducted studies 10 and 20 minutes after induction of anesthesia in 16 patients with normal hearts who were undergoing minor orthopedic operations. Wall thickening was measured with the centerwall method along 100 chords drawn perpendicular to a line constructed around the center of the ventricular wall, midway between the endocardial and epicardial contours. Thickening, either normalized by the length of the end-diastolic perimeter or expressed as a percentage of the end-diastolic wall thickness at each chord, was compared with measurements of endocardial motion. Wall motion was relatively diminished in the anteroseptal region and enhanced on the contralateral wall, but wall thickening was homogeneous throughout the contour. Normalized wall thickening was significantly less variable (standard deviation/mean, 0.47 +/- 0.13) in the normal population than were either percent wall thickening (0.53 +/- 0.012) or wall motion (0.51 +/- 0.09) (p less than 0.005 for both comparisons). There was no significant change in regional or global function between 10 minutes and 20 minutes after the induction of anesthesia. In summary, normalized wall thickening as a parameter of regional left ventricular function is more homogeneous and less variable in subjects with normal hearts than is endocardial motion because wall thickening measurements are not subject to cardiac translocation artifacts. This low variability suggests that normalized wall thickening measured by the centerwall method may prove particularly useful for intraoperative and postoperative monitoring of regional left ventricular function by transesophageal echocardiography in patients undergoing both cardiac and noncardiac surgical procedures.

Adult↗
PubMed1990

Effects of standard mitral valve replacement on left ventricular function.

Recent studies have suggested that excision of the mitral valve apparatus during mitral valve replacement impairs left ventricular performance. However, functional measurements in humans have been difficult to obtain in a load-independent fashion. To investigate this concept, 12 patients (mean age, 65 +/- 8 years; mean New York Heart Association functional class, 3.3 +/- 0.7) with 4+ mitral regurgitation (n = 8) or mitral stenosis (valve area, 1.2 +/- 0.2 cm2) (n = 4) underwent prosthetic valve replacement using crystalloid cardioplegia. No patient required therapeutic inotropic support, every patient had at least the anterior mitral leaflet excised, and paced heart rate was maintained constant throughout. Left ventricular volume was measured with radionuclide angiocardiography, left ventricular pressure with a 3F micromanometer, and left ventricular wall volume with two-dimensional transesophageal echocardiography. Left ventricular preload was varied over a mean end-diastolic pressure range of 9 to 20 mm Hg and an end-diastolic volume range of 134 to 170 mL to generate four to five steady-state pressure-volume loops before and ten minutes after cardiopulmonary bypass. Left ventricular performance was estimated with the stroke work/end-diastolic volume relationship, which is insensitive to load. After bypass, no significant change (p greater than 0.1) was noted in wall volume for patients with mitral regurgitation or mitral stenosis (175 +/- 68 to 189 +/- 63 mL/m2 and 130 +/- 22 to 127 +/- 19 mL/m2, respectively).(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗
PubMed1990

The utility of transesophageal echocardiography and Doppler color flow imaging in patients undergoing cardiac valve surgery.

To assess the value of intraoperative transesophageal echocardiography during cardiac valve surgery, 154 consecutive patients who had a valve operation in conjunction with pre- and postcardiopulmonary bypass transesophageal imaging were studied. Prebypass imaging yielded unsuspected findings that either assisted or changed the planned operation in 29 (19%) of the 154 patients. Imaging immediately after bypass revealed unsatisfactory operative results that necessitated immediate further surgery in 10 (6%) of the 154 patients. Postbypass left ventricular dysfunction, prompting administration of inotropic agents, was identified in 13 patients (8%). Transesophageal echocardiography proved most useful when both two-dimensional and Doppler color flow imaging were employed in patients undergoing a mitral valve operation, where surgical decisions based on echocardiographic results were made in 26 (41%) of 64 cases. Postbypass echocardiographic findings identified patients at risk for an adverse postoperative outcome. Of 123 patients whose postbypass valve function was judged to be satisfactory, 18 (15%) had a major postoperative complication and 6 (5%) died, whereas of 7 patients with moderate residual valve dysfunction, 6 (86%) had a postoperative complication and 3 (43%) died (p less than 0.05 for both). Likewise, of 131 patients with preserved postbypass left ventricular function, 12 (9%) had a major complication and 7 (5%) died, whereas of 23 patients with reduced ventricular function, 17 (73%) had a postoperative complication and 6 (26%) died (p less than 0.05 for both). These data indicate that intraoperative transesophageal echocardiography is useful in formulating the surgical plan, assessing immediate operative results and identifying patients with unsatisfactory results who are at increased risk for postoperative complications.

Cardiopulmonary Bypass↗
PubMed1990

Estimation of left ventricular volume and ejection fraction by two-dimensional transoesophageal echocardiography: comparison of short axis imaging and simultaneous radionuclide angiography.

We have compared short axis images of the left ventricle (LV) obtained with transoesophageal echocardiography (TOE) to assess LV size and function with those obtained by radionuclide angiography (RNA). Simultaneous TOE and RNA images were attempted in 14 patients and results obtained in 12 patients undergoing repair of abdominal aortic aneurysms. The area of the LV cavity seen in the short axis images at a mid-papillary muscle level at end-systole (ESA) and end-diastole (EDA) were compared with volumes measured by RNA at end-systole (ESV) and end-diastole (EDV). An area ejection fraction (AEF) calculated from the TOE images (AEF = EDA-ESA/EDA) was compared with the RNA ejection fraction (EF) where EF = EDV-ESV/EDV. Good correlations were found between TOE log EDA and RNA log EDV (r = 0.86), TOE log ESA and RNA log ESV (r = 0.92) and TOE AEF and RNA EF (r = 0.96). This suggests that TOE short axis imaging at a mid-papillary muscle level is generally adequate for monitoring LV function during operation.

Echocardiography↗
PubMed1989

Right and left ventricular performance during and after abdominal aortic aneurysm repair.

To evaluate the effect of aortic occlusion and limb reperfusion on global and regional function of the right and left ventricle during infrarenal abdominal aortic aneurysm repair, 23 patients underwent five intraoperative first-pass radionuclide angiocardiograms: 1) before the skin incision, 2) at aortic cross-clamp, 3) 20 minutes after aortic occlusion, 4) at unclamping, and 5) after skin closure. A subset of twelve patients had simultaneous transesophageal echocardiography to evaluate left ventricular wall stress. Parameters measured included the electrocardiogram (ECG), heart rate, blood pressure, pulmonary artery pressure, the cardiac output, the left and right ventricular ejection fractions, left ventricular volumes, and left ventricular wall stress. Significant changes (p less than 0.01) were observed at aortic clamping in the left ventricular ejection fraction (from 0.56 to 0.48), end-diastolic volume (from 171 to 225 ml), end-systolic volume (from 85 to 127 ml), mean blood pressure (from 82 to 91 mmHg), and meridional end-systolic wall stress (from 53 to 67 10(3) dyne/cm2). Once the clamp was removed, significant variations were seen in the left ventricular ejection fraction (from 0.51 to 0.58), end-diastolic volume (from 205 to 187 ml), end-systolic volume (from 105 to 94 ml), mean blood pressure (from 84 to 69 mmHg), and meridional end-systolic wall stress (from 67 to 46 10(3) dyne/cm2). No differences were observed between the two aortic occlusion studies, and the baseline level of function was recovered in all parameters during the last study. These data quantify the changes in heart function that occur during abdominal aortic aneurysm operation and demonstrate that the majority of the adaptations that occurred were due to a variation in afterload.

Aged↗
PubMed1989

Current management of mitral valve incompetence associated with coronary artery disease.

At a time when hospital mortality for adult cardiac operations is continuing to fall, the combined mitral valve coronary bypass subset remains at relatively high risk. Efforts to improve results should be directed toward a more general application of mitral reconstruction in this population, tailoring the type of repair to the pathological anatomy of valve dysfunction. Other promising therapeutic measures include the liberal use of reperfusion therapy in the acute papillary muscle dysfunction group, better selection patients for operation, and perhaps operative recommendation to a greater proportion of the more stable patients that previously were treated medically. Finally increasing the general awareness of this problem should hasten the development of improved management strategies.

Coronary Artery Bypass↗
PubMed1989

General anesthesia during percutaneous transluminary coronary angioplasty for acute myocardial infarction: results of a randomized controlled clinical trial.

Acutely ill patients with myocardial infarction may require immediate cardiac catheterization and coronary angioplasty to achieve myocardial reperfusion. To determine the feasibility of using general anesthesia under these circumstances, a randomized clinical trial was performed. Of 50 patients, 25 received anesthesia and 25 receive intravenous sedation. There were transient increases in heart rate and blood pressure after tracheal intubation in the anesthetized patients, followed by significant and sustained decreases below baseline values once steady state anesthesia was attained. Arterial oxygenation was significantly improved in anesthetized patients. There were no serious complications due to anesthesia, but the small sample size limited the power of the study to detect differences in morbidity or mortality. Patients strongly preferred anesthesia. These results show that general anesthesia is feasible in patients undergoing interventional cardiac catheterization during acute myocardial infarction, when pain, anxiety or agitation do not respond adequately to conventional measures.

Anesthesia, General↗