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At least 1,189 records · Page 66Linked to original sources
PubMed2004

Pelvic emergency clamps: anatomic landmarks for a safe primary application.

The application of the pelvic clamp as a tool for emergency stabilization of unstable pelvic ring fractures has proved to be a life-saving procedure. Using correct technique, the pelvic clamp can be applied within a few minutes after the patient's admission. To avoid severe complications (eg, pin perforation into the pelvis) during the application, anatomic landmarks for the correct pin placement have to be defined. The surface landmarks that are presently recommended for the correct pin placement are not always reliably found due to deformation of the body surface caused by swelling and hematoma. Our experience with 43 emergency applications of the pelvic C-clamp showed that reliable anatomic landmarks on the bony surface of the innominate bone could be identified to ensure correct pin placement. The ideal insertion point of the pins is an anatomic region on the lateral cortex of the ileum, where an easily palpable "groove" is formed by angulations of the lateral cortex of the iliac wing. Being increasingly used as an entry point for percutaneous transiliosacral screw fixations of sacroiliac joint injuries and sacral fractures, this region, which is close to the sacroiliac joint, represents an ideal point for maximum compression of the posterior pelvic ring. With the described technique, this "groove" can be identified easily even in emergency situations by blunt palpation with an instrument, avoiding the time-consuming use of a fluoroscope in most cases.

Emergency Medical Services↗
PubMed1998

A newly developed shunt system for carotid surgery: T-shaped silicone shunt tubes and clamping devices: technical note.

BACKGROUND: Although the use of a shunt during carotid endarterectomy has been controversial, a convenient shunt system is still required. METHODS: We have devised an intraluminal shunt system, T-shaped silicone shunt tubes, and clamping devices for carotid surgery. The tube has enough pliability and length to be used in a looped or U-shaped mode and constructs a T-shape with a side arm available for monitoring blood pressure in the shunt system. Clamping devices, such as modified Sugita ring clips and encircle type bulldog clamps, make it possible to hold the tube by a simple maneuver and to minimize the intimal damage. RESULTS: This shunt system has been used in 170 carotid endarterectomies and other 10 carotid surgical operations, and the mortality and morbidity rates were 0% and 2.4%, respectively. CONCLUSION: This shunt system can be safely and easily used for cervical carotid surgery.

Brain Ischemia↗
PubMed1976

The site of reapplication of microvascular clamps.

An experiment was done with albino rats to determine whether the arterial clamp should be reapplied proximal or distal to the anastomosis when revising a venous anastomosis in microvascular surgery. Our findings showed that the reapplication of clamps should be avoided if possible. However, if it is necessary to reapply an arterial clamp, it may be placed either proximal or distal to the anastomosis - with almost the same incidence of patency resulting.

Animals↗
PubMed2000

Clamp delay: an effective new method of nonsurgical delay.

This study introduces an effective new method of nonsurgical delay. In this new method, a special clamp that compressed a bipedicled skin fold along the sides of a proposed flap was glued to rat dorsa. The study also used a control group of untreated flaps and a group of flaps delayed by the conventional surgical procedure involving conventional parallel incisions. Eight days later, 1 x 6 cm reverse McFarlane flaps were isolated from the wound and raised. After 5 days, the survival length of the flaps was measured. Viability of the flaps delayed by the clamps [40.5 +/- 2.0 mm (mean +/- standard error); n = 10] did not differ from that of surgically delayed flaps (41.3 +/- 3.6 mm; n = 8) and was significantly higher (p < 0.001) than the survival of control flaps (26.3 +/- 0.6 mm; n = 10). Clamp delay can be useful in flap research that explores the relative significance of the vessel obstruction and biochemical processes that follow the surgical delay procedure. This method also offers a new perspective by introducing the concept of nonsurgical delay into clinical practice.

Animals↗
PubMed2006

The trochanteric C-clamp for provisional pelvic stability.

The application of a pelvic clamp for provisional stability of unstable pelvic fractures has been advocated in the orthopaedic literature. Although the technique has gained some supporters, problems with placement and associated complications have prevented widespread acceptance. We have modified the pelvic clamp (ACE Pelvic Stabilizer) technique by applying the clamp to the trochanteric region of the femur and applying a reduction force similar to a pelvic binder or external fixator.

Adult↗
PubMed2004

Laparoscopic partial nephrectomy of solid renal masses without hilar clamping using a monopolar radio frequency device.

PURPOSE: Partial nephrectomy is currently recommended for most amenable solid renal tumors, especially if they are exophytic and less than 4 cm. We reviewed our initial experience with laparoscopic partial nephrectomy for solid renal masses without clamping the renal vasculature using a monopolar device that uses radio frequency energy with low volume saline irrigation for simultaneous blunt dissection, hemostatic sealing and coagulation of the renal parenchyma (TissueLink, TissueLink Medical, Inc., Dover, New Hampshire). MATERIALS AND METHODS: From September 2002 to April 2003, 10 patients underwent transperitoneal laparoscopic partial nephrectomy, including 9 with solid renal masses and 1 with a complex cyst. In all cases the renal hilum was dissected and the renal vessels were isolated but none had renal vascular clamping. The TissueLink DS dissecting sealer or Floating Ball (TissueLink Medical, Inc.) was used to dissect the tumor free bluntly, while simultaneously sealing and coagulating bleeders. RESULTS: Mean patient age was 54.6 years (range 42 to 72). Mean American Society of Anesthesiologists score was 2.3 (range 2 to 4). Mean tumor size was 3.9 cm (range 2.1 to 8). The mass had a peripheral location in 7 cases and a central location in 3. Mean operative time was 232 minutes (range 144 to 280) and mean blood loss was 352 ml (range 20 to 1000). One patient received blood transfusion and all tumor margins were negative. Mean hospital stay was 1.7 days (range 1 to 5) and pain medication use was minimal. One patient had a brief period of urine leakage from the lower pole calix, which was managed successfully by ureteral stenting and Foley catheter drainage of the bladder. CONCLUSIONS: Laparoscopic partial nephrectomy can be performed without renal vascular clamping. TissueLink technology allows complete tumor resection and provides adequate parenchymal hemostasis of the tumor bed. Its scant tissue charring production does not interfere with the pathological assessment of the tumor margin status.

Adult↗
PubMed1984

The slow inward current, isi, in the rabbit sino-atrial node investigated by voltage clamp and computer simulation.

The properties of the slow inward current, isi, in the sino-atrial (s.a.) node of the rabbit have been investigated using two microelectrodes to apply voltage clamp to small, spontaneously beating, preparations. Many of the experimental results can be closely simulated using the computer model of s.a. node electrical activity (Noble & Noble 1984) which has been developed from models of Purkinje fibre activity (Noble 1962; DiFrancesco & Noble 1984). Comparison of the computed reconstructions with experimental results provides a test of the validity of the modelling. Experiments using paired depolarizing clamp pulses show that inactivation of isi is calcium-entry dependent although, unlike the inactivation of Ca2+ currents in some other systems, it also shows some voltage-dependence. Re-availability (recovery from inactivation) of isi in s.a. node is much slower than inactivation at the same potential, showing that isi is not controlled by a single first order process. This very slow recovery from inactivation of isi in the s.a. node and the slow time course of its activation and inactivation at voltages near threshold (-40 to -50 mV) can be closely modelled by assuming that there are two components of 'total isi': a fast inward current, iCa,f' representing the 'gated' fraction and a second, slower, inward current component, iNaCa which, we propose, is caused by the sodium-calcium exchange that ensues when the initial Ca2+ -entry triggers the release of stored intracellular Ca2+. When repetitive trains of clamp pulses are given, a 'staircase' of isi magnitude is seen which can be increasing ('positive') or decreasing ('negative') according to the potential level and frequency of the pulse train given. When computer reconstructions of such staircases are made, it is found that the positive staircases (which, in contrast to negative staircases, imply that more complex processes than simple inactivation are present) can be closely simulated by a model which incorporates slower processes (suggested Na-Ca exchange current) in the total isi in addition to the gated current component.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed2005

Passive all-optical force clamp for high-resolution laser trapping.

Optical traps are useful for studying the effects of forces on single molecules. Feedback-based force clamps are often used to maintain a constant load, but the response time of the feedback limits bandwidth and can introduce instability. We developed a novel force clamp that operates without feedback, taking advantage of the anharmonic region of the trapping potential where the differential stiffness vanishes. We demonstrate the utility of such a force clamp by measuring the unfolding of DNA hairpins and the effect of trap stiffness on opening distance and transition rates.

Avidin↗
PubMed2001

Crystal structure of an archaeal DNA sliding clamp: proliferating cell nuclear antigen from Pyrococcus furiosus.

The proliferating cell nuclear antigen (PCNA) is now recognized as one of the key proteins in DNA metabolic events because of its direct interactions with many proteins involved in important cellular processes. We have determined the crystal structure of PCNA from a hyperthermophilic archaeon, Pyrococcus furiosus (pfuPCNA), at 2.1 A resolution. pfuPCNA forms a toroidal, ring-shaped structure consisting of homotrimeric molecules, which is also observed in the PCNA crystals from human and yeast. The overall structure of pfuPCNA is highly conserved with other PCNA proteins, as well as with the bacterial ss clamp and the bacteriophage gp45. This result shows that the three-dimensional structure of the sliding clamp is conserved in the three domains of life. pfuPCNA has two remarkable features compared with the human and yeast PCNA molecules: it has more ion pairs and fewer intermolecular main chain hydrogen bonds. The former may contribute to the thermal stability of pfuPCNA, and the latter may be the cause of the stimulatory effect of pfuPCNA on the DNA synthesizing activity of P. furiosus DNA polymerases in the absence of the clamp loader replication factor C in vitro.

Amino Acid Sequence↗
PubMed1987

Very low density lipoprotein metabolism after insulin over-treatment and during a euglycaemic clamp.

The disturbance of very low density lipoprotein (VLDL) metabolism that occurs as a result of intensive insulin treatment and during a euglycaemic clamp have been investigated in a rat model. Normal rats were maintained with fed blood glucose levels below 5 mmol l-1 for 8 weeks by subcutaneous insulin injections (normal fed levels 5.8 +/- 0.4 (SD) mmol l-1). Glucose requirement to maintain a glucose clamp was significantly reduced (116 +/- 3 mumol min-1 kg-1 (SE) vs. 173 +/- 5 mumol min-1 kg-1, P less than 0.001), compared with weight-matched normal control rats. In the fasting state (blood glucose 3.5 +/- 0.2 mmol l-1 vs. 3.9 +/- 0.1 mmol l-1, NS) plasma non-esterified fatty acid levels were reduced. Fasting VLDL-triglyceride turnover, measured by bolus injection of 14C-VLDL, was also lower (3.17 +/- 0.12 mumol min-1 kg-1 vs. 3.50 +/- 0.07 mumol min-1 kg-1, P less than 0.05). Despite decreased turnover, insulin over-treated rats had normal plasma triglyceride concentrations indicating a removal defect. At the end of a 3-h euglycaemic clamp, plasma triglyceride concentrations and VLDL-triglyceride turnover were decreased in both normal control and insulin over-treated animals, and turnover remained significantly lower in the insulin over-treated rats (2.59 +/- 0.13 mumol min-1 kg-1 vs. 3.08 +/- 0.10 mumol min-1 kg-1, P less than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

Adipose Tissue↗
PubMed1979

Effects of thoracic epidural block and the beta-1-adrenoreceptor agonist prenalterol on the cardiovascular response to infrarenal aortic cross-clamping in man.

Sixteen patients scheduled for abdominal aortic resection and grafting were randomly assigned to two groups to study the cardiovascular effects of infrarenal aortic cross-clamping. The patients in the first group had received a thoracic epidural block followed by intravenous administration of the selective beta-1-adrenoreceptor agonist prenalterol prior to induction of general anaesthesia. The patients in the second group served as controls and received no specific treatment prior to general anaesthesia. In both groups, aortic cross-clamping was followed by an equal rise in pulmonary artery diastolic pressure and mean systemic arterial pressure. There was a significant difference in systemic vascular resistance, as the control group had a 46% increase 30 s after cross-clamping, while the pretreated patients had only a 7% increase at the same time. Moreover, the patients given the thoracic epidural block followed by prenalterol increased their stroke volume and cardiac indices, as compared to the patients in the control group who showed a significant decrease in these parameters. Possible mechanisms for the mode of action of the combined thoracic epidural block and beta-1-adrenoreceptor agonist pretreatment are discussed.

Adrenergic beta-Agonists↗
PubMed1995

Haemodynamic effects of thoracic epidural anaesthesia during proximal aortic cross-clamping in pigs.

Cross-clamping (XC) of the thoracic aorta induces a hyperdynamic circulation proximal to the aortic clamp. In this investigation, the effects of thoracic epidural anaesthesia (TEA) on the haemodynamic response to XC were studied in pigs. Seventeen pigs were anaesthetized with ketamine, and the thoracic aorta was cross-clamped for 30 minutes. In eight of the animals (TEA-group) a thoracic epidural block (3 ml 0.5% bupivacaine) was added to the general anaesthesia. Prior to XC there was a lower heart rate (HR), cardiac output (CO) and mixed venous oxygen saturation (SvO2) in the TEA-group compared to the nine animals with general anasthesia only (control-group). During XC there was an increase in HR, CO, SvO2 and proximal aortic blood pressure (PPROX) in both groups, without differences between groups. Following aortic declamping central venous pressure (CVP), pulmonary artery pressure (PAP) and pulmonary capillary wedge pressure (PCWP) increased in both groups. Fifteen minutes after declamping, one animal in each group died. It was concluded that in this experimental model, TEA combined with general anaesthesia did not modify the haemodynamic response to XC of the thoracic aorta.

Anesthesia, Epidural↗
PubMedDate not supplied

Red cell sorbitol levels during hyper and hypoglycaemic clamp studies in insulin-dependent diabetic patients.

The red cell sorbitol concentration has been suggested as a measure of polyol pathway activity. Red cell sorbitol levels were higher in 53 patients having insulin-dependent diabetes mellitus (IDDM) than in 16 control subjects. Six patients having IDDM underwent hyperglycaemic 'clamp' studies; the red cell sorbitol level returned to the normal range when the blood glucose was clamped at 5 mmol/l for 1 h and rapidly increased when it was clamped at 15 and 25 mmol/l for a further hour at each level. Seven patients with IDDM were rendered hypoglycaemic; red cell sorbitol levels rapidly fell to a level less than, but not significantly different from normal. The results of these studies suggest that in IDDM red cell sorbitol levels are a reflection of prevailing blood glucose concentration and do not indicate long-term sorbitol accumulation in other tissues.

Adult↗
PubMed1992

The use of a combination nail elevator and hemostat clamp. New instruments for nail avulsion.

Nail avulsion surgery is frequently accomplished using a hemostat clamp with or without a nail elevator device. Two new instruments have been developed that combine the useful design specifications of the hemostat clamp with the nail elevator device. Specifically, one blade of the hemostat is replaced with either a nail elevator spatula or a Freer septum elevator allowing nail elevation, clamping, and removal with a single instrument. Use of either device is more efficient because nail avulsion is completed using a single instrument thereby reducing procedural steps and handling and sterilization costs. Furthermore, these instruments may reduce the risk of trauma to the nail bed and matrix during nail avulsion. The instruments and their use are described.

Humans↗
PubMed2006

Mechanical evaluation of two loop tensioning methods for crimp clamp extracapsular stabilization of the cranial cruciate ligament-deficient canine stifle.

OBJECTIVES: To describe a method of tightening nylon loops secured with a crimping system for extracapsular fabello-tibial stabilization of the cranial cruciate ligament-deficient stifle and to compare this with a method using a commercially available tensioning device. STUDY DESIGN: In vitro mechanical testing. METHODS: Fourteen standardized nylon loops were tensioned using a tensioning device and secured with crimp clamps. Another 14 loops were tightened by partially securing the crimp clamp, followed by tightening of the loop by hand, before definitively securing the crimp clamp. Loops were loaded to failure in a materials testing machine. RESULTS: Mean ultimate loads for instrument-tightened and hand-tightened loops were 383.7 and 371.4 N, respectively. Mean stiffness values for instrument-tightened and hand-tightened loops were 59.7 and 59.3 N/mm, respectively. These differences were not significant. CONCLUSIONS: The hand tightening method does not affect the mechanical properties of the loop. CLINICAL RELEVANCE: The hand tightening method described is a valuable technique for unassisted surgeons without access to tensioning devices.

Animals↗
PubMedDate not supplied

Ischemic preconditioning in myocardial revascularization with intermittent aortic cross-clamping.

BACKGROUND: This study tests the hypothesis that initial brief periods of ischemia can increase the protection obtained by intermittent aortic cross-clamping. METHODS: In the control group (n = 18), the procedure was performed under intermittent aortic cross-clamping at 32 degrees C. Patients in the preconditioned gorup (n = 17) received a stimulus of two 3-minute periods of cross-clamping followed by 2 minutes of reperfusion prior to standard operation. CKMB, troponin 1, adenosine, and lactate were obtained from the great cardiac vein at the onset of cardiopulmonary bypass (CPB), at the end of the first anastomosis, and at the end of CPB. RESULTS: CKMB and troponin I were slightly higher at the end of CPB in the control group, while there was no difference between adenosine and lactate levels. [table: see text]. CONCLUSION: There was no difference between groups in terms of myocardial protection.

Adenosine↗
PubMed1978

Crayfish stretch receptor: an investigation with voltage-clamp and ion-sensitive electrodes.

1. The membrane characteristics of the slowly adapting stretch receptor from the crayfish, Astacus fluviatilis, were examined with electrophysiological techniques consisting of membrane potential recording, voltage clamp and ion-sensitive microelectrodes. 2. The passive membrane current (Ip) following step changes of the membrane potential to levels above 0 mV required more than a minute to decay to a steady-state level. 3. The stretch-induced current (SIC, where SIC = Itotal--Ipassive) was not fully developed until the Ip had decayed to a steady state. 4. With Ip at the steady state and the stretch-induced current at the O-current potential, a slow stretch-induced inward current was isolated. The latter reaches a maximum after 1 sec of stretch and declines even more slowly after stretch. The I-V relation of the slow current had a negative slope and reversed sign near the resting potential. It is suggested that this current is due to a Cl- conductance change. 5. The stretch-induced current, consisting of a rapid transient phase and a steady component can be isolated from the slow stretch-induced current at a holding potential corresponding to the resting potential. 6. The SIC-Em relation is non-linear and reverses sign at about +15 mV. 7. In a given cell, the reversal potential of the stretch-induced potential change obtained with current clamp coincided with the 0-current potential of the stretch-induced current obtained by voltage clamp. The average value from twenty-six cells was +13 +/- 6.5 mV; cell to cell variability seemed to be correlated with dendrite length. 8. Tris (mol. wt. 121) or arginine (mol. wt. 174) susbstituted for Na+ reduces but does not abolish the stretch-induced current. 9. The permeability ratios of Tris:Na and arginine:Na were estimated from changes in the 0-current potential as these cations replaced Na+ in the external medium. The PTris:PNa was somewhat higher (0.31) than the Parginine:PNa ratio (0.25). 10. Changes in the external Ca2+ concentration had no effect on the 0-current potential in Na or Tris saline. However, reducing Ca2+ did augment the stretch-induced current in either saline. A tenfold reduction of Ca2+ increased the conductance (at the 0-current level) about twofold. 11. Intracellular K+ and Cl- activities were obtained with ion sensitive electrodes. The average values from six cells were aiK = 133 +/- 34 mM and aiCl = 15.2 +/- 1.8 mM S.D.). EK was about 20 mV more negative than Em and ECl was about 10 mV more positive than Em. 12. aik and resting Em undergo large changes in K+-free solutions. After 60 min, ak was reduced eightfold and Em was reduced from -67 to -40 mV. Reduced Ca2+ in K+-free augments the rate of these changes. Receptor potential amplitude was also reduced in K+-free solution but could be restored upon polarizing the membrane to the pre-existing resting level.

Animals↗
PubMed1983

Calcium-activated outward current in voltage-clamped hippocampal neurones of the guinea-pig.

Slow clamp currents were recorded from CA1 and CA3 pyramidal neurones in slices of guinea-pig hippocampus maintained in vitro, using a single micro-electrode sample-and-hold technique. Depolarizing voltage commands evoked a time- and voltage-dependent outward current which was suppressed by removing external Ca or by adding Cd (0.5 mM) or Mn (5 mM). This Ca-dependent current (Ic) was not reduced by muscarinic agonists (unlike IM) but was greatly reduced by 5-20 mM-tetraethylammonium (TEA). Repolarizing IC tail currents reversed at -73 +/- 5 mV in 3 mM-K solution. The reversal potential became about 30 mV more positive on raising [K]o to 15 mM. No clear change in current amplitude or tail-current reversal potential occurred on adding Cs (2 mM), reducing [Cl]o from 128 to 10 mM, or replacing external Na with Tris. The underlying conductance GC was activated at membrane potentials positive to -45 mV. At -32 mV GC showed an approximately exponential increase with time, with a time constant of approximately 0.6 sec at 26 degrees C. Repolarizing tail currents declined exponentially with time, the time constant becoming shorter with increasing negative post-pulse potentials. When the clamp was switched off at the end of a depolarizing command of sufficient amplitude and duration to activate IC, a membrane hyperpolarization to -73 mV ensued, of similar amplitude and decay time to that following spontaneous action potentials. It is concluded that the clamp current observed in these experiments is probably the Ca-activated K current thought to contribute to the post-activation after-hyperpolarization in hippocampal neurones.

Action Potentials↗