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At least 397 records · Page 22Linked to original sources
PubMed1977

The effect of time of cord clamping and maternal blood pressure on placental transfusion with cesarean section.

We measured the residual placental blood volume (RPBV) of 20 infants delivered at term by cesarean section of women not in labor. In all cases, the umbilical cord was clamped within 40 seconds of birth. RPBV decreased significantly with increasing age at cord clamping. In addition, RPBV for infants with cords clamped within 20 seconds of birth correlated inversely with maternal systolic blood pressure (mean RPBV = 54.8 ml. per kilogram at 105 torr and 28.4 ml. per kilogram at 148 torr). However, RPBV did not correlate with maternal blood pressure for the whole group of 20 infants or for those with cords clamped later than 20 seconds after birth. These data indicated that in infants delivered by cesarean section placental transfusion is time related during the first 40 seconds of life and that maternal blood pressure also influences the magnitude of placental transfusion during the first 20 seconds after birth. Analysis of data from this study combined with data from a previous study shows that after 40 seconds the net flow between placenta and infant reverses and that cord clamping delayed beyond this point is accompanied by a rise in RPBV back to the level found when the cord was clamped before 20 seconds.

Blood Pressure↗
PubMed1993

Effect of vascular clamp on endothelial integrity of the internal mammary artery.

The preservation of endothelial integrity is essential for maintaining patency of vascular grafts. The internal mammary artery flow is often interrupted with the application of a soft vascular clamp to achieve a bloodless field during the anastomosis. We investigated the effect of the vascular clamp on the internal mammary artery endothelium using the scanning electron and light microscope. The endothelium was examined before and at 15 and 30 minutes after clamping in both the pedicled and the skeletonized arteries. Endothelial integrity was breached by clamping with early evidence of platelet adhesion to the damaged areas. The severity of the endothelial damage was related to the clamp time, but there was no difference in the degree of damage between the pedicled and the skeletonized arteries. We conclude that the vascular clamp causes injury to the internal mammary artery endothelium and may be implicated in early postoperative graft failure.

Constriction↗
PubMed1988

Voltage clamp studies of fertilization in sea urchin eggs. II. Current patterns in relation to sperm entry, nonentry, and activation.

Following attachment of a sperm to the surface of a sea urchin egg clamped at a membrane potential (Vm) more positive than +17 mV, no changes in membrane conductance can be detected, the sperm does not enter egg, and no morphological changes can be detected. At Vm from +17 to -100 mV three characteristically different types of current profiles are observed: Type I are activation currents in eggs penetrated by a sperm. These have three phases, which occur in all eggs clamped at Vm from +17 to -20 mV and in decreasing percentages at clamped Vm more negative than -20 mV (to -75 mV). Complete fertilization envelopes are elevated, relatively large mound-shaped fertilization cones form, and the eggs develop to normal embryos. Type II are sperm transient currents in eggs not penetrated by a sperm, the eggs otherwise remaining in the unfertilized state. These transients are simpler and shorter than type I currents, and are observed only at clamped Vm more negative than -20 mV. Type III are modified activation currents in eggs not penetrated by a sperm. These have three phases, are observed only at clamped Vm more negative than -20 mV, and are the only type of activation current seen at clamped Vm more negative than -75 mV. Complete fertilization envelopes are elevated, the fertilization cones are small and filament-like, and the eggs fail to cleave. We conclude that (a) the sperm transient currents (type II) and phase 1 of the activation currents (type I and III) are similar events generated by a sperm-initiated localized conductance increase, (b) the abrupt decrease of current which terminates the sperm transients and phase 1 of type III currents results from a turnoff of the sperm-induced conductance increase and signals that the sperm will not enter the egg, and (c) the occurrence of phase 2 during an electrophysiological response induced by a sperm indicates that the egg is activating.

Animals↗
PubMed1995

Halifax clamps: efficacy and complications in posterior cervical stabilization.

BACKGROUND: Trauma, neoplasia, rheumatoid arthritis, Down's syndrome, and inflammatory conditions are well-known causes of spinal instability. The Halifax clamp is a method of posterior cervical stabilization that is attached to the adjoining laminae and tightened until no movement between involved vertebrae is possible. Our experience with cases that have utilized Halifax interlaminar clamps, their results and complications are presented. METHODS: We conducted a retrospective review of patients with spinal instability in whom Halifax interlaminar clamps were utilized for posterior spinal stabilization. RESULTS: Over a 5-year period, 38 patients in our institution underwent posterior stabilization of the cervical spine utilizing the Halifax interlaminar clamp. The patients represent a mix of motor vehicle- and sports-related traumas, rheumatoid subluxation, and a single cancer patient. Average follow-up has been 29 months (range 3 to 36 months). Thirty (78.9%) patients have had good results (i.e., stable fusion and regression of symptoms) and no complications. Three patients from our institution, and a fourth patient referred to us postoperatively, developed complications related to the Halifax clamps. Four patients died from unrelated causes. CONCLUSIONS: Halifax interlaminar clamps are a safe and effective method for posterior stabilization of various causes of cervical spinal instability.

Adolescent↗
PubMed2004

Stroke in surgery of the arteriosclerotic descending thoracic aortic aneurysms: influence of cross-clamping technique of the aorta.

OBJECTIVE: The risk of stroke caused by dislodgment of loose atheromatous plaque or mural emboli is increased by cross-clamping of the aorta. Some patients undergo descending thoracic aortic aneurysm repair with proximal aortic cross-clamping between the left common carotid artery and the left subclavian artery. The objective of this study was to determine the influence of proximal aortic cross-clamping in arteriosclerotic aneurysm or dissecting aneurysm repair. METHODS: Between May 1984 and May 2003, 81 patients underwent elective surgery for distal arch or descending aortic aneurysm repair with proximal aortic cross-clamping between the left common carotid artery and the left subclavian artery. To evaluate the influence of the proximal aortic cross-clamping, patients were divided into two groups: patients who had undergone arteriosclerotic aneurysm repair (group I, n=25) and patients who had undergone dissecting aneurysm repair (group II, n=56). RESULTS: Eight (9.9%) of the 81 patients had a stroke. Six strokes occurred in operations for arteriosclerotic aneurysm repair group I and two strokes occurred in operations for dissecting aneurysm repair group II (24 vs 3.6%; p=0.009). In-hospital mortality rates were 12% in group I and 8.9% in group II (p=0.70). Major postoperative complications included renal failure requiring hemodialysis (in 4.2% of the patients in group I and in 8.3% of the patients in group II, p=0.99) and pulmonary complication (in 20% of the patients in group I and in 16% of the patients in group II, p=0.67). CONCLUSION: Cross-clamping between head vessels should be avoided if at all possible when operating on patients who have arteriosclerotic descending thoracic aneurysms.

Adult↗
PubMed2006

Cardiomyocyte apoptosis and duration of aortic clamping in pig model of open heart surgery.

OBJECTIVE: Apoptotic cardiomyocyte death is induced during open heart surgery, but its determinants are poorly understood. Prolonged aortic clamping time is associated with adverse clinical outcomes. The purpose of this study was to determine whether occurrence of cardiomyocyte apoptosis is related to the duration of aortic clamping in experimental pig model of cardiac surgery with cardiopulmonary bypass. METHODS: The pigs (mean weight 29 +/- 1 kg) were randomly divided to undergo cardioplegic arrest for 60 (n = 4) or 90 (n = 4) min followed by reperfusion period of 120 min. Control group (n = 5) was connected to cardiopulmonary bypass for 120 min without cardioplegic arrest. Cardiomyocyte apoptosis was detected (TUNEL assay and immunohistochemical staining of active caspase-3) in left ventricular tissue samples obtained before ischemia and after the ischemia-reperfusion period. RESULTS: Apoptotic cardiomyocytes were found in all samples obtained after cardioplegic arrest and cardiopulmonary bypass alone with the TUNEL assay. The amount of apoptosis after the 120 min of cardiopulmonary bypass alone in the control group was 0.006 +/- 0.001%. Compared with this, cardiomyocyte apoptosis was increased after cardioplegic arrest. After 60 min of aortic cross-clamp the amount of apoptosis was 0.019 +/- 0.004% (p = 0.031). After 90 min of aortic cross-clamp the amount was 0.042 +/- 0.005% (p < 0.001) being significantly higher than after 60 min (p = 0.001). Aortic cross-clamp of 90 min also resulted in a detectable increase in caspase-3 activation when compared with controls. CONCLUSIONS: The occurrence of cardiomyocyte apoptosis increases with prolonged aortic clamping time during open heart surgery.

Animals↗
PubMed2005

Clamping of the renal artery in laparoscopic partial nephrectomy: an old device for a new technique.

OBJECTIVE: We describe our experience with the transient clamping of the renal artery during laparoscopic partial nephrectomy for renal cancer with a double loop clamping device, inspired by the Rumel tourniquet. The silastic rubber loop is positioned around the renal artery and clinched, thus achieving arterial occlusion. METHODS: From November 2002 until July 2004, fourteen consecutive patients (mean age of 58 +/- 11.6 years) underwent laparoscopic transperitoneal partial nephrectomy using the silastic rubber clamping device, eight of them on the right side and six on the left side. Hemorrhage of the renal defect was controlled with bipolar electrocoagulation, argon beam coagulation, laparoscopic sutures, surgical and fibrin glue. RESULTS: : The mean surgical time was 198.92 +/- 39.95 min for a mean tumour size of 2.9 +/- 2.32 cm and a mean blood loss of 104.57 +/- 77.69 ml. The clamping device was easily and successfully positioned around the renal artery in 2.05 +/- 0.45 min and the mean warm ischemic time was 25.21 +/- 6.07 min. CONCLUSIONS: The clamping device procures successful atraumatic occlusion of the renal artery during laparoscopic partial nephrectomy without the need for an additional port. As such, it could be considered as an alternative for the laparoscopic bulldog and Satinsky clamp.

Constriction↗
PubMed2005

A serrated jaw clamp for tendon gripping.

Mechanical testing of tendon and application of muscular tendon forces in cadaveric or animal studies requires the use of a clamp to hold the tendon rigidly at high loads without damaging it. Frozen type serrated clamp was able to achieve the objective but is less readily available and manageable because of its complex and massive configuration. In this study, a custom-made, serrated jaw clamp was fabricated. Maximum tension before visual slippage was monitored during tensile testing of a bovine tendon. The non-frozen serrated jaw clamp was able to sustain tension forces of more than 2500 N and strain of about 30% without slippage and cutting of the tendon. The jaw clamp can be easily customised and fabricated for biomechanical studies to hold tendons of different sizes. The commercially available, serrated plastic material enables the jaw clamp to be custom-made with minimal workmanship and manufacturing time.

Animals↗
PubMed1998

Role of left atrial appendage in left atrial reservoir function as evaluated by left atrial appendage clamping during cardiac surgery.

We evaluated the role of left atrial appendage (LAA) in the left atrial (LA) reservoir function by assessing the changes in LA flow dynamics after LAA clamping during cardiac surgery. The subjects were 8 patients who had undergone coronary artery bypass grafting (CABG) and 7 who had undergone mitral valvular surgery due to mitral regurgitation. We recorded transmitral, pulmonary venous and LAA flow velocity patterns by intraoperative transesophageal pulsed Doppler echocardiography, monitoring LA pressure before and 5 minutes after LAA clamping. The maximal LAA area was significantly greater, and the peak late diastolic LAA emptying flow velocity was significantly lower before LAA clamping in the mitral regurgitation group than in the CABG group. In both groups, the peak early and late diastolic transmitral and pulmonary venous flow velocities significantly increased, and the peak second systolic pulmonary flow velocity significantly decreased during LAA clamping. There were no significant changes in heart rate and systemic systolic blood pressure during LAA clamping, whereas mean LA pressure and maximal LA dimension significantly increased in both the groups. The LA pressure-volume relation during ventricular systole shifted upward and to the left during LAA clamping, and the slope was steeper in the MR group than in the CABG group. We conclude that the LAA is more compliant than the LA main chamber, and plays an important role in LA reservoir function in the presence of LA pressure and/or volume overload.

Aged↗
PubMed2001

Single aortic cross-clamp technique reduces S-100 release after coronary artery surgery.

BACKGROUND: Neurologic impairment after coronary artery bypass grafting is associated with cerebral embolization. An important cause of embolism is aortic manipulation. Constructing both distal and proximal anastomoses during a single period of aortic cross-clamping avoids this source of embolism and may reduce neurologic injury after coronary artery bypass grafting. METHODS: Fifty consecutive patients undergoing coronary artery bypass grafting were prospectively randomized to group 1, in which a single aortic cross-clamping was used to construct distal and proximal anastomoses, or to group 2, in which the proximal anastomoses were each constructed with a partial occluding aortic clamp. Levels of S-100 and troponin-T release were measured preoperatively and postoperatively. RESULTS: Aortic cross-clamp time was significantly longer in group 1, but other preoperative and intraoperative variables were equally represented in both groups. Control group levels of S-100 and troponin-T were similar. Postoperative S-100 levels were significantly higher in group 2 than in group 1 (p < 0.015). No significant difference was found between the groups in postoperative troponin-T levels. CONCLUSIONS: The results of this trial suggest improved cerebral protection is associated with the single aortic cross-clamp technique for coronary artery bypass grafting with no increase in myocardial damage. The single aortic cross-clamp technique is simple and inexpensive. We recommend its wider use.

Aged↗
PubMed1982

Single aortic cross-clamping for distal and proximal anastomoses in coronary surgery: an alternative to conventional techniques.

Using hypothermic cardiopulmonary bypass and a single cross-clamping period under multidose infusions of hypothermic cardioplegia, both distal and proximal anastomoses were performed in 87 consecutive patients undergoing coronary artery operation. This method allows for precise surgical technique, avoids the need for multiple clampings of the ascending aorta, and appears to avoid the threat of aortic tear. When the clamp is released, the heart has been totally revascularized. This is in contrast to more conventional methods, where an exclusion clamp is applied to the ascending aorta and where the combination of coronary stenosis, low perfusion pressure during bypass, and narrowing of the ascending aorta by the exclusion clamp may be more hazardous than a single cross-clamp period for construction of all anastomoses. This is particularly applicable to patients with severe stenosis of the left main coronary artery.

Adult↗
PubMed1999

Quick, simple clamping technique in descending thoracic aortic aneurysm repair.

BACKGROUND: Although significant advances have been made in the surgical treatment of diseases affecting the descending thoracic aorta, paraplegia remains a devastating complication. We propose the quick, simple clamping technique to prevent spinal cord ischemic injury. METHODS: From 1983 to 1998, 143 patients had descending thoracic aorta aneurysm repair. We divided the patients into the following three groups according to the surgical technique used: selective atriodistal bypass was used in group 1 (66 patients); simple clamping technique in group 2 (28 patients); and quick simple clamping technique in group 3 (49 patients). Mean aortic cross clamp time was 39+/-13 minutes in group 1, 37+/-11 minutes in group 2, and 17+/-6 minutes in group 3 (p<0.01 group 3 versus group 1 and group 2). RESULTS: The overall incidence of paraplegia was 4.8% (7 patients), 4.5% (3 patients) in group 1, 14.3% (4 patients) in group 2, and 0 in group 3 (p<0.05 group 3 versus group 2). The overall in-hospital mortality rate was 5.5%. Multivariate logistic regression analysis showed a powerful effect of aortic cross-clamping time as risk factor for both paraplegia (p<0.008), with an odds ratio of 1.03 per minute, and in-hospital mortality (p<0.001), with an odds ratio of 2.5 per minute. The mean follow-up time was 65 months with a lower overall mortality rate in group 3 than in group 1 and group 2 (p<0.05). CONCLUSION: In descending thoracic aortic aneurysm repair, spinal cord perfusion can be maintained adequately without reimplantation of segmental vessels or use of atriodistal bypass when the aortic cross-clamp time is short (<15 to 20 minutes).

Aortic Aneurysm, Thoracic↗
PubMed1969

Computed membrane currents in cardiac Purkinje fibers during voltage clamps.

Recent measurements have indicated that some of the cardiac cell electrical capacitance is in series with a resistance. The computations of currents in a voltage clamp presented below show that, in this case, there is a danger that capacitive transient currents recorded during voltage clamp experiments may be confused with currents arising through rapid active membrane conductance changes. Secondly, a voltage clamp technique aimed at avoiding capacitive transients, namely the linear or ramp clamp, has recently been introduced. An attempt has been made here to evaluate the usefulness of ramp clamps in studying membrane electrical properties, by computing ramp clamp results and considering the difficulties in reconstructing the original model from these results. It is concluded that such a reconstruction is not feasible.

Cell Membrane↗
PubMed2000

Global brain ischemia produced by clamping left subclavian artery and bicarotid trunk in the rabbit.

Thirty-five rabbits were divided randomly into 5 groups: sham operation, 10 minutes clamping bicarotid trunk (partial ischemia, PI), and 3 groups of 5, 7, and 10 minutes clamping left subclavian artery and bicarotid trunk (global ischemia, GI). Systolic arterial pressure increased slightly in the PI group, but doubled in the GI groups during clamping. Heart rate did not change in the PI group, but decreased transiently in the GI groups during clamping. Brain temperature decreased gradually in the GI groups during clamping, but did not change in the PI group. Necrotic changes were present 96 hours later in approximately 50% of the hippocampal CA1 cells in the GI groups, but in none of the cells in the PI and sham operation groups. The present results may indicate that clamping left subclavian artery and bicarotid trunk in the rabbit brings about global brain ischemia.

Animals↗
PubMed1982

[Anesthesia for carotid surgery with clamping under residual carotid pressure control].

Carotid endarterectomy with clamping is performed in 50 patients. Internal carotid artery stump pressure is measured in all cases after clamping at the beginning of the operation. In 35 patients, an increase of systolic pressure is observed which allows a stump pressure more than 70 mmHg in 29 patients. In 15 patients, systolic pressure decreases and a stump pressure more than 70 mmHg is observed in two patients. When the stump pressure is more than 70 mmHg, the clamping is maintained. When the stump pressure is low, the clamping is stopped. A perfusion of Metaraminol increases systolic pressure in all cases: stump pressure is measured again after a second clamping. In 17 cases out of 19, stump pressure increases more than 70 mmHg and the clamping is maintained. In the two cases with a low stump pressure, a shunt is used during intervention.

Aged↗
PubMed1997

Artery wall damage and platelet uptake from so-called atraumatic arterial clamps: an experimental study.

A 'traumatic' clamps are routinely used to control arteries during reconstruction, but little is known about the arterial damage caused and the effects on platelet uptake. This experiment used sheep carotid arteries to correlate the degree of histologic damage observed with the level of indium-111-labelled platelet uptake in clamped arterial segments. Scanning electron microscopy and light microscopy enabled three degrees of injury to be recognized. In mild injuries, endothelial cell orientation was changed but local platelet uptake was little different from controls. In moderate injuries, the endothelial cells directly squeezed by the clamp were morphologically altered, superficial fissures developed which extended into the media, and local platelet uptake was usually increased. Severe injuries caused extensive endothelial cell desquamation, formation of deep cavities in the media and increased platelet uptake (mean 5.51 times that of control). Platelet uptake at the site of clamp application was not significantly different from non-clamped carotids for mild injuries. However, the increased platelet uptakes for moderate (P = 0.007) and severe (P = 0.005) injuries were statistically significant when compared with non-clamped control arterial segments.

Animals↗
PubMedDate not supplied

Current best evidence: a review of the literature on umbilical cord clamping.

Immediate clamping of the umbilical cord can reduce the red blood cells an infant receives at birth by more than 50%, resulting in potential short-term and long-term neonatal problems. Cord clamping studies from 1980 to 2001 were reviewed. Five hundred thirty-one term infants in the nine identified randomized and nonrandomized studies experienced late clamping, ranging from 3 minutes to cessation of pulsations, without symptoms of polycythemia or significant hyperbilirubinemia. Higher red blood cell flow to vital organs in the first week was noted, and term infants had less anemia at 2 months and increased duration of early breastfeeding. In seven randomized trials of preterm infants, benefits associated with delayed clamping in these infants included higher hematocrit and hemoglobin levels, blood pressure, and blood volume, with better cardiopulmonary adaptation and fewer days of oxygen and ventilation and fewer transfusions needed. For both term and preterm infants, few, if any, risks were associated with delayed cord clamping. Longitudinal studies of infants with immediate and delayed cord clamping are needed.

Adult↗
PubMed2006

The replication clamp-loading machine at work in the three domains of life.

Sliding clamps are ring-shaped proteins that tether DNA polymerases to DNA, which enables the rapid and processive synthesis of both leading and lagging strands at the replication fork. The clamp-loading machinery must repeatedly load sliding-clamp factors onto primed sites at the replication fork. Recent structural and biochemical analyses provide unique insights into how these clamp-loading ATPase machines function to load clamps onto the DNA. Moreover, these studies highlight the evolutionary conservation of the clamp-loading process in the three domains of life.

Adenosine Triphosphatases↗