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At least 919 records · Page 51Linked to original sources
PubMed1980

Pulmonary microembolism during and after aortic cross-clamping in heparinized and non-heparinized pigs.

The occurrence of pulmonary microembolism after aortic clamping and declamping was investigated in 21 young pigs. The prophylactive effect of heparin was also examined. Eight animals were heparinized, while 13 did not receive heparin. In 15 pigs the plasma concentration of fibrinogen was determined before, during and after clamping of the aorta. External detection of 51Cr-labelled platelets and 125I-labelled fibrinogen was performed. Lung tissue from these animals was homogenized and analysed for radioactivity. Specimens were taken from the lungs of all animals for morphological investigation. A significant decrease in plasma fibrinogen concentration was noted during the aortic clamping in non-heparinized animals. Morphological studies of lung tissue revealed numerous fibrin/platelet thrombi, leukocyte and platelet aggregates, atelectases and bleedings. In homogenized lung tissue, areas with elevated radioactivity were found, indicating fibrin/platelet entrapment. No such changes were seen in pigs pretreated with heparin. It was found that pulmonary microembolism occurs frequently after aortic clamping if heparin is not given at an early stage of the procedure.

Animals↗
PubMed1979

Hemodynamic effects of aortic clamping and decompression with a temporary shunt for resection of the descending thoracic aorta.

To assess the effects clamping of the proximal thoracic aorta and of subsequent decompression with a temporary shunt on cardiac function during resection of aneurysms of the descending thoracic aorta, mean arterial (MAP), central venous (CVP), mean pulmonary arterial (MPAP), and pulmonary capillary wedge pressures (PCWP), as well as cardiac index (CI), were measured in eight patients at baseline, 2 minutes after clamping the aorta beyond the left carotid or left subclavian artery, and 2 minutes after opening the shunt. Following clamping, MAP, CVP, and PCWP increased significantly (P less than 0.05), while CI decreased significantly, an average of 29%, and heart rate remained unchanged. After opening the shunt, all pressures returned to baseline levels. CI increased, but remained below the baseline level in seven of the eight patients (P less than 0.05). Our data indicate that significant deterioration of left ventricular performance results from clamping and that the deleterious effects can be reversed by use of a temporary shunt. They support the recommendation of proximal aortic decompression during thoracic aneurysmectomy.

Adult↗
PubMed1994

Comparison studies of passive and active shunting during cross-clamping of the descending thoracic aorta.

The effects of passive (no pump) and active (using centrifugal pump) shunting on hemodynamics and metabolisms during cross-clamping of the descending thoracic aorta were compared in mongrel dogs. In Group I (control), the aorta was cross-clamped for 2 hours without shunting; in Group II (passive), a temporary shunt was placed between the left common carotid and left femoral arteries during cross-clamping; and in Group III (active), left heart by-pass, matching flow to that in group II, was performed. Hemodynamic and metabolic parameters were recorded prior to cross-clamping and following every 30 min for 4 hours. All animals in Group I suffered from hemodynamic instability, metabolic abnormal and neurologic injury and died within 12 hours. Hemodynamic changes were unstable in Group III than II, and three dogs in Group III, but none in Group II, suffered from neurologic injury. Metabolic changes between Group II and III were not significant. We conclude that passive shunting is superior to active shunting for aortic by-pass.

Animals↗
PubMed1994

Halifax interlaminar clamps for posterior atlanto-axial arthrodesis with spinal fusion by "H" bone+graft.

The use of Halifax interlaminar clamps in posterior arthrodesis for atlanto-axial instabilities has recently been reported. The four Anderson II fractures submitted were surgically treated by posterior arthrodesis with Halifax clamps and bilateral "H" shaped bone-grafts obtained from the iliac crest. Only in the first case--initially treated without fusion--a review of the system became necessary due to the loosening of one clamp. No post-operative neurological complications appeared and non malunion or nonunion occurred at follow-up. Posterior arthrodesis with Halifax clamps does not involve any complication connected with the use of metal wire and the association of posterior fusion by lateral "H" shaped bone grafts ensures a stable and physiological reduction of dens fractures and atlanto-axial luxations/subluxations often associated.

Adult↗
PubMed1994

Resection of aortic aneurysms without aortic clamp technique with the aid of hypothermic total body retrograde perfusion.

Aneurysms involving either the aortic arch or the proximal descending thoracic aorta in five patients were resected with the aid of profound hypothermic total body retrograde perfusion. Traditional surgical management of the aortic arch and the descending thoracic aorta necessitates clamping of the aorta. However, this technique may be associated with rupture or atheroembolism. Rupture occurring at the clamping site may be difficult to repair. Atheroembolism to the brain compromises the neurologic system, and multiple organ embolism is associated with disseminated intravascular coagulopathy. Atheroembolism in cardiovascular surgery has become increasingly prevalent. It is necessary to prevent clamp injuries and to preserve the function of the vital organs, such as the brain, heart, and liver, during aortic reconstruction. We applied a total body retrograde perfusion technique to operations for aortic aneurysms. Total body retrograde perfusion consists of cerebral protection by continuous perfusion through the superior vena cava, intermittent retrograde coronary perfusion through the coronary sinus, and continuous abdominal visceral perfusion through the inferior vena cava. It can yield a relatively bloodless operating field without the need for aortic clamping. We believe this new adjunct offers excellent results in the surgical treatment of aneurysms of the aortic arch or adjacent structures.

Adult↗
PubMed1993

[Monitoring of peripheral tissue oxygenation with near infrared spectrophotometry during abdominal or iliac aortic cross-clamping surgery].

Peripheral tissue oxygenation was monitored with near infrared spectrophotometry during abdominal or common iliac aortic cross-clamping surgery. Six patients who had abdominal aortic aneurysm (AAA) and eight patients who had aortic sclerotic occlusive disease (ASO) were studied. At the beginning of cross-clamping, oxyhemoglobin was decreasing and deoxyhemoglobin was increasing in all AAA patients. Average of 37 minutes following cross-clamping of abdominal aorta, both hemoglobin values were stabilized. On the other hand, changes in both hemoglobin values were delayed or missing in ASO patients. The results suggest that the duration from cross-clamping to stabilization is related to co-lateral blood flow. During operation, monitoring of peripheral blood flow with near infrared spectrophotometry is useful for detection of peripheral ischemia and for the estimation of postoperative local blood flow.

Aorta, Abdominal↗
PubMed1993

[Clinical preeminence of single aortic cross-clamping for proximal anastomoses in coronary artery bypass surgery].

We evaluated the preeminence of the construction of proximal anastomoses during single aortic cross-clamping periods in coronary artery bypass surgery. Twenty-six patients were divided into two groups; single aortic cross-clamping (SAX) group: 13 patients, partial aortic clamping (PAC) group: 13 patients. In this study, these two groups were compared in terms of aortic cross-clamping time (AXT), total extracorporeal circulation (ECC) time (TECCT), ECC weaning time (WT), amount of cardioplegic solution, total levels of serum CPK and CPK-MB, and graft patency. The results were analyzed by ANOVA and chi-square test. AXT was longer in the SAX group compared with the PAC group (78.2 +/- 5 versus 63.2 +/- 4 min; p < 0.05). TECCT (120.4 +/- 6 versus 109 +/- 5 min) and WT (37.4 +/- 2 versus 41 +/- 2 min) were not significant between the two groups. The total amount of cardioplegic solution was greater in the SAX group compared with the PAC group (1100 +/- 60 versus 927 +/- 43 ml; p < 0.05). The levels of serum CPK and CPK-MB were a little lower in the SAX group, but there were no significant differences between the SAX group and the PCA group. The graft patency of both two groups were excellent. From these results, SAX is not critical in the routine of coronary artery bypass surgery. Clinically, the SAX technique allows us to select more suitable areas of the ascending aorta for placement of all the proximal grafts if the ascending aorta is short.(ABSTRACT TRUNCATED AT 250 WORDS)

Anastomosis, Surgical↗
PubMed1996

The effects of nimodipine on ischemic injury of the spinal cord during thoracic aortic cross-clamping.

BACKGROUND: The purpose of this study was to evaluate the protective effects of a neuroselective calcium antagonist, nimodipine on spinal cord ischemia during and after thoracic aortic cross-clamping. METHODS: Thirty adult dogs underwent 60 minutes of thoracic aortic cross-clamping via a left thoracotomy. The dogs were randomized into 3 groups (n = 10) and received either intravenous control (normal saline), sham (polyethylene glycol) or nimodipine solution during a period of 150 minutes. Spinal cord perfusion (SCP) was directly monitored using a laser doppler flowmeter. After 48 hours, neurologic status was assessed using Tarlov scores and the spinal cords evaluated histologically for evidence of ischemia (grades 1-4: severe to mild ischemia). RESULTS: Twenty-six dogs survived the operation. Proximal (carotid) blood pressure increased 30-40% and cerebrospinal fluid (CSF) pressure increased 50% during cross-clamping for all 3 groups. The SCP decreased predictably during cross-clamping in all dogs but after unclamping, the nimodipine group had significantly less hyperperfusion than the saline and sham control groups (30 min after unclamping, control: 74.1 +/- 12.6 ml/min, sham: 51.8 +/- 4.15 ml/min, nimodipine: 33.1 +/- 3.9 ml/min, p = 0.04). This hyperperfusion phenomenon correlated with adverse neurologic (Tarlov score) outcome (p = 0.01). Paraplegia rates were 78% (control), 70% (sham) and 71% (nimodipine) (p = NS). The histologic grades of the spinal cords from those dogs which received nimodipine tended to correspond to better tissue preservation (control: 1.72 +/- 0.49, sham: 1.75 +/- 0.46, nimodipine: 2.14 +/- 0.56, p = NS). CONCLUSIONS: Nimodipine used as single agent therapy failed to show a statistically significant clinical neurologic benefit. However, nimodipine significantly decreased postischemic reperfusion hyperemia in the spinal cord as measured by laser doppler flowmetry. This reduced hyperperfusion, which significantly correlated with functional outcome, may be responsible for dampening neural cell damage. Thus, nimodipine should be considered as an adjunct to a multimodality approach in the prevention of spinal cord ischemia during thoracic and thoracoabdominal aortic reconstructions.

Animals↗
PubMedDate not supplied

Management of malignant tumor with intracaval extension by selective clamping of IVC.

BACKGROUND/AIMS: Malignant tumors with retrohepatic intracaval extensions are difficult to treat. We report five cases of intracaval tumor emboli (3 hepatocellular carcinoma, 2 renal cell carcinoma). MATERIAL AND METHODS: The tumor embolus is removed by the following methods according to site: in the right atrium, by open heart surgery after clamping of the inferior vena cava between the superior vena cava and the intrahepatic inferior vena cava and of the portal vein, in combination with a cardiopulmonary bypass using a pump oxygenator; above the confluence of the hepatic vein with the inferior vena cava, by inferior vena cava clamping between its suprahepatic and intrahepatic portions, shunting from the inferior vena cava and the portal vein to the axillary vein; below the inferior vena cava-hepatic vein confluence, by inferior vena cava clamping below the confluence and in the infrahepatic portion; and around the confluence, by side clamping of the inferior vena cava, maintaining both hepatic and systemic circulations. RESULTS: Pulmonary emboli were diagnosed in one patient. However, the patient's condition improved with anti-coagulant therapy. No major complication was observed in any other patient. All patients were discharged after a mean postoperative period of 32.8 days. One patient with HCC died of lung metastasis at 5 months and the other two, of recurrence in the residual portion of the liver at 4 and 16 months, and the two with RCC are still alive without recurrence of the carcinoma 9 and 14 months later. CONCLUSIONS: Preoperative recognition by ultrasonography, computed tomographic scanning, cavography and especially trans-esophageal endoscopic ultrasonography is important. Vascular exclusion may also be performed by various techniques depending on the site of the tumor embolus.

Adult↗
PubMed1996

[History of surgical instruments: 5. The development of tangentially closing vascular clamps].

We demonstrate the historical development of tangential occlusion clamps, which by partially clamping the vessels and by partially maintaining the blood flow, allow to reconstruct or to anastomose large vessels in the side-by-side-technique. The first tangential occlusion clamp was developed by Friedrich Trendelenburg (1844-1924) in 1908, when he performed the operative treatment of embolism of the pulmonary artery. This clamp was modified later by A.W. Meyer [1927] and V.P. Satinsky [ca. 1950].

Animals↗
PubMed1997

[A simple method for improvement of the measurement of respiratory impedance in humans by increasing oropharyngeal impedance using cheek and mouth floor clamps].

It is known, that the upper airway (oropharyngeal) impedance (Z(op)) influences the measured input impedance of the respiratory system (Zrs). This investigation deals with simple methods reducing the artefact caused by Z(op). The following methods have been examined: (1) Supporting the cheeks with fingers, (2) supporting the cheeks and the floor of the mouth with fingers and (3) using a new mechanical clamp for the cheeks and the floor of the mouth. The effect of these procedures on Zrs, were investigated on two subjects. Also Z(op) has been estimated during a voluntary closure of the glottis (VALSALVA manoeuvre). The impedance has been assessed as well with forced sine shaped oscillations as with the pulsatile technique. All three procedures show, compared to measurements without any support, an increase of the Zrs, especially at high values. The highest increase has been obtained while using the clamp (up to 50%). The varied impedance must be placed in parallel to Zrs, because Z(op) increases even more than Zrs. So, by applying the clamp the subjects is better coupled to the measuring system. The clamp is easy to handle, leads to more exact values, and increases the inter- and intra-individual reproducibility.

Airway Resistance↗
PubMedDate not supplied

Biology, physiology and physiopathology of clamping during liver surgery.

Liver surgery is currently performed with minimal morbidity and mortality, mostly thanks to reduced intraoperative blood loss, achievable by various types of liver clamping. A better knowledge of the physiological and physiopathological changes caused by liver clamping is however still necessary. The "natural" evolution of biochemical and liver function tests after liver surgery have been described. This paper describes the hemodynamic changes observed with different types of clamping and discusses several ways in which liver clamping techniques might be improved.

Blood Loss, Surgical↗
PubMedDate not supplied

Major liver resections without vascular clamping: retrospective study of 84 cases.

BACKGROUND/AIMS: The question as to whether vascular clamping aggravates mortality and morbidity of major liver resection was investigated in this study. Major liver resection with vascular clamping for parenchyma transection has mortality between 0 and 5%, and higher morbidity reaching 47% with healthy liver in recent report. METHODOLOGY: Eighty-four major liver resection without vascular clamping were carried out between January 1986 to December 1996 were reviewed. There were 57 men and 27 women with average age of 58.2 (12.2) years old. Indications of resection were adenoma (4.8%) angioma (11.9%) focal nodular hyperplasia (1.2%) hematoma (1.2%) metastases (60.7%) hepatocellular carcinoma (14.3%) and cholangiocarcinoma (5.9%). Resections used ultrasonic dissector (Sonoca) with intraoperative ultrasonography were right hepatectomy in 56 cases extended right hepatectomy in 10 cases left hepatectomy in 17 cases and middle hepatectomy in 1 case. Remnant liver was cirrhotic in 3 cases. RESULTS: Three patients died (3.5%) and the rate of major complications were 11.2%. 46 patients (54.8%) had no blood transfusion. The mean of blood transfusion was 1.5 (2.7) units. The mean of operative length was 286.23 (63.3) minutes and the mean hospital stay was 15.8 (8.1) days. Liver function tests are same with the others authors at day 1, 4 and 7 after operation with return to normal value after 1 week. CONCLUSION: In major liver resection, vascular clamping is not always necessary.

Blood Loss, Surgical↗
PubMed2006

Microchip technology for automated and parallel patch-clamp recording.

The patch-clamp technique is the state-of-the-art technology for the study of a large class of membrane proteins called ion channels. Ion channels mediate electrical current flow, have crucial roles in cellular physiology, and are important drug targets. However, patch clamping is a laborious process requiring a skilled experimenter and is, therefore, not compatible with the high throughput needed in drug development. The solution for automated and parallel patch-clamp measurements that is provided by microchip technology is presented here.

Animals↗
PubMed1995

Single-microelectrode voltage clamp measurements of pancreatic beta-cell membrane ionic currents in situ.

A conventional patch clamp amplifier was used to test the feasibility of measuring whole-cell ionic currents under voltage clamp conditions from beta-cells in intact mouse islets of Langerhans perifused with bicarbonate Krebs buffer at 37 degrees C. Cells impaled with a high resistance microelectrode (ca. 0.150 G omega) were identified as beta-cells by the characteristic burst pattern of electrical activity induced by 11 mM glucose. Voltage-dependent outward K+ currents were enhanced by glucose both in the presence and absence of physiological bicarbonate buffer and also by bicarbonate regardless of the presence or absence of glucose. For comparison with the usual patch clamp protocol, similar measurements were made from single rat beta-cells at room temperature; glucose did not enhance the outward currents in these cells. Voltage-dependent inward currents were recorded in the presence of tetraethylammonium (TEA), an effective blocker of the K+ channels known to be present in the beta-cell membrane. Inward currents exhibited a fast component with activation-inactivation kinetics and a delayed component with a rather slow inactivation; inward currents were dependent on Ca2+ in the extracellular solution. These results suggest the presence of either two types of voltage-gated Ca2+ channels or a single type with fast and slow inactivation. We conclude that it is feasible to use a single intracellular microelectrode to measure voltage-gated membrane currents in the beta-cell within the intact islet at 37 degrees C, under conditions that support normal glucose-induced insulin secretion and that glucose enhances an as yet unidentified voltage-dependent outward K+ current.

Animals↗
PubMed1995

Effects of voltage clamping on epithelial cell composition in toad urinary bladder studied with x-ray microanalysis.

Toad urinary bladder epithelial cells were incubated in Na Ringer's with the serosal surface of the epithelium clamped at either +50 mV, 0 mV (short-circuited) or -50 mV with respect to the mucosal surface. Following incubation, portions of tissue were coated with an external albumin standard and rapidly frozen. Cryosections were freeze-dried and cell composition determined by x-ray microanalysis. Cell water and ion contents were unaffected when tissues were short-circuited rather than clamped close to their open-circuit potential difference (+50 mV). Incubation with vasopressin at +50 mV, and under short-circuit conditions, caused Na uptake without cell swelling or gain in Cl. Clamping at -50 mV resulted in uptake of water and ions, with considerable variation from cell to cell. These variations in cell composition were exacerbated by vasopressin. The greater the increase in water content, the greater the rise in cell Cl. However, there was no consistent pattern to the associated changes in cation contents. Most cells gained some Na. In some cells, this gain was accompanied by an increase in K. In others, the gain of Na was predominant and cell K content actually fell. At -50 mV with ouabain, many of the cells also gained water. As was found in our earlier study with ouabain under short circuit conditions (Bowler et al., 1991), there was considerable variation in the extent of the Na gain and K loss; some cells were largely depleted of K while in others the K content remained relatively normal. These results indicate differences between granular cells in the availabilities in the plasma membranes of ion pathways, either as a consequence of differences in the numbers of such pathways or in their control.

Animals↗
PubMed2003

Patch-clamping of primary cardiac cells with micro-openings in polyimide films.

Patch-clamping is a powerful method for investigating the function and regulation of ionic channels. Currently, great efforts are being made to automate this method. As a step towards this goal, the feasibility of patch-clamping primary cells with a microscopic opening in a planar substrate was tested. Using standard microfabrication and ion beam technology, small-diameter openings (2 and 4 microm) were formed in polyimide films (thickness 6.5 microm). Single cells (sheep Purkinje heart cells, Chinese hamster ovary cells) in a suspension were positioned on top of the opening and sucked towards the opening to improve adhesion of the cell to the planar substrate, hence increasing the seal resistance. Voltage/current measurements yielded a median seal resistance of 1.3 Mohms with 4 microm openings (n=24) and 26.0 Mohms with 2 microm openings (n = 75), respectively. With 2 microm openings, successful loose-patch recordings of TTX-sensitive inward currents and action potentials in sheep Purkinje heart cells (n = 18) were made. In rare cases, gigaseals (n = 4) were also measured, and a whole-cell configuration (n = 1) could be established. It was concluded that the simple planar patch approach is suitable for automated loose-patch recordings from cells in suspension but will hardly be suitable for high-throughput whole-cell patch-clamping with high-resistance seals.

Animals↗
PubMed2005

Insulin sensitivity, proinsulin and insulin as predictors of coronary heart disease. A population-based 10-year, follow-up study in 70-year old men using the euglycaemic insulin clamp.

AIMS/HYPOTHESIS: The association between CHD and insulin sensitivity (Si) measured by the euglycaemic insulin clamp has not been examined previously. Earlier studies found a relationship between CHD and elevated plasma insulin, an analysis that may have been confounded by co-determination of proinsulin, which has evolved as a stronger predictor of CHD. The aim was to determine the longitudinal relationships between Si, intact proinsulin, 32-33 split proinsulin, specific insulin and subsequent CHD. METHODS: This was a population-based cohort study of 815 men in Uppsala, Sweden, aged 70 years at baseline with a follow-up of up to 10 years. Baseline insulin sensitivity was determined by euglycaemic insulin clamp. Fasting proinsulin, 32-33 split proinsulin and specific insulin concentrations were analysed using specific two-site immunometric assays. CHD was taken as diagnosed, if stated (in the event of death) on the Cause of Death Registry, or for subjects hospitalised for the first time with CHD, if CHD was recorded in the Hospital-Discharge Registry. The associations were analysed using Cox's proportional hazards, presented as hazard ratios (HRs) with their 95% CIs for a one-SD increase in the predictor. RESULTS: In multivariate analysis, Si (HR:0.80, CI:0.65-0.97) adjusted for serum cholesterol, systolic blood pressure, fasting plasma glucose, BMI and smoking predicted CHD. Intact proinsulin (HR:1.18, CI:1.01-1.38), adjusted as the model above, predicted CHD, whereas 32-33 split proinsulin (HR:1.13, CI:0.95-1.35) or specific insulin (HR:1.07, CI:0.89-1.30) did not. CONCLUSIONS/INTERPRETATION: Insulin resistance measured by the euglycaemic insulin clamp predicts subsequent CHD in elderly men. Proinsulin provides a better prediction of CHD than insulin.

Aged↗