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PubMed1993

The Halifax Interlaminar Clamp for posterior cervical fusion: initial experience in the United Kingdom.

A retrospective review of patients who underwent posterior cervical stabilization with Halifax Interlaminar Clamps in four neurosurgical centers in the United Kingdom was performed. Satisfactory bone fusion without complication occurred in all patients in whom lower cervical spinal stabilization (C3-C7) was performed. Complications occurred in 14 of 45 patients undergoing atlantoaxial arthrodesis. In 10 patients, one of the screws loosened, and in 4 patients, one of the clamps disengaged; additional operations to achieve bone fusion were required in 9 patients (20%). The Halifax Interlaminar Clamp is safe and effective for posterior stabilization in the lower cervical spine; there is a significant failure rate associated with its use for atlantoaxial arthrodesis.

Arthritis, Rheumatoid↗

PubMed1988

Voltage-clamp models for the study of acute and chronic effects of ethanol on ionic currents in adult mammalian neurons.

The aim of this study was to develop and characterize a model system in which the effects of ethanol on voltage- and agonist-gated ionic currents in adult mammalian neurons could be studied using voltage-clamp techniques. We have found that neurons enzymatically isolated from the peripheral (nodose and superior cervical ganglia) and central nervous system (pyramidal layer of the hippocampus) of the adult rat and guinea pig provide several advantages over conventional neuronal preparations (e.g., intact ganglia or brain slice). First, the isolated neurons, in conjunction with the patch clamp technique, allow high fidelity recordings of both macroscopic and single channel currents. Secondly, current- and voltage-clamp recordings have revealed that active and passive membrane properties, chemosensitivity, and ionic currents in the isolated neurons resemble those described from conventional preparations. Finally, we have developed an intracellular perfusion system which allows the convenient control of the intracellular milieu. This technique should be useful for the study of intracellular second messengers on ionic currents. Our results demonstrate that isolated adult mammalian neurons are ideally suited for the study of both the acute and chronic effects of ethanol on membrane excitability.

Animals↗

PubMed2006

A prospective comparison of clamping the drain or post-operative salvage of blood in reducing blood loss after total knee arthroplasty.

We undertook a prospective, randomised study in order to evaluate the efficacy of clamping the drains after intra-articular injection of saline with 1:500 000 adrenaline compared with post-operative blood salvage in reducing blood loss in 212 total knee arthroplasties. The mean post-operative drained blood volume after drain clamping was 352.1 ml compared to 662.3 ml after blood salvage (p < 0.0001). Allogenic blood transfusion was needed in one patient in the drain group and for three in the blood salvage group. Drain clamping with intra-articular injection of saline with adrenaline is more effective than post-operative autologous blood transfusion in reducing blood loss during total knee arthroplasty.

Aged↗

PubMed2004

Gain-clamped S-band discrete Raman amplifier.

We demonstrate the advantages of an optically gain-clamped S-band discrete Raman amplifier: low gain variation over a large input dynamic range, effective suppression of Raman transients, and amplifier instability in the strong-pump-weak-signal configuration. We further investigate experimentally the operating conditions necessary for effective gain clamping and demonstrate gain flattening over 30 nm of bandwidth. Thus a gain-clamped discrete Raman amplifier shows promise for practical deployment.

Journal Article↗

PubMed2006

Delayed cord clamping in very preterm infants reduces the incidence of intraventricular hemorrhage and late-onset sepsis: a randomized, controlled trial.

OBJECTIVE: This study compared the effects of immediate (ICC) and delayed (DCC) cord clamping on very low birth weight (VLBW) infants on 2 primary variables: bronchopulmonary dysplasia (BPD) and suspected necrotizing enterocolitis (SNEC). Other outcome variables were late-onset sepsis (LOS) and intraventricular hemorrhage (IVH). STUDY DESIGN: This was a randomized, controlled unmasked trial in which women in labor with singleton fetuses <32 weeks' gestation were randomly assigned to ICC (cord clamped at 5-10 seconds) or DCC (30-45 seconds) groups. Women were excluded for the following reasons: their obstetrician refused to participate, major congenital anomalies, multiple gestations, intent to withhold care, severe maternal illnesses, placenta abruption or previa, or rapid delivery after admission. RESULTS: Seventy-two mother/infant pairs were randomized. Infants in the ICC and DCC groups weighed 1151 and 1175 g, and mean gestational ages were 28.2 and 28.3 weeks, respectively. Analyses revealed no difference in maternal and infant demographic, clinical, and safety variables. There were no differences in the incidence of our primary outcomes (BPD and suspected NEC). However, significant differences were found between the ICC and DCC groups in the rates of IVH and LOS. Two of the 23 male infants in the DCC group had IVH versus 8 of the 19 in the ICC group. No cases of sepsis occurred in the 23 boys in the DCC group, whereas 6 of the 19 boys in the ICC group had confirmed sepsis. There was a trend toward higher initial hematocrit in the infants in the DCC group. CONCLUSIONS: Delayed cord clamping seems to protect VLBW infants from IVH and LOS, especially for male infants.

Blood Transfusion↗

PubMedDate not supplied

Is subdiaphragmatic aortic cross-clamping a suitable model for spinal cord ischemia/reperfusion injury study in rats?

PURPOSE: To evaluate the efficacy of subdiaphragmatic aortic cross-clamping in an experimental model of ischemia/reperfusion injury of the spinal cord in albino rats. METHODS: Thirty-six male Wistar rats were randomized in two groups (n=18): G-1 (Sham) and G-2 (Ischemia/Reperfusion, I/R). G-2 rats were submitted to 30 min subdiafragmatic aortic cross-clamping. G-1 rats served as controls and were submitted to surgical trauma (laparotomy) without ischemia. Samples (spinal cord and arterial blood) were collected at the end of ischemic period and 10 (T-10) and 20 (T-20) min later in G-2 rats. Sham rats (G-1) samples were collected at the same time-points. Blood and tissue metabolites concentrations of pyruvate, lactate, glucose and medullary adenosine triphosphate (ATP) were assayed. RESULTS: Blood and tissue concentrations of pyruvate and glucose as well as lactate and medullary ATP were not different when comparing G1 to G2. Lactacemia was significantly elevated in G-2 compared with G-1 rats during reperfusion (T-10). CONCLUSION: Subdiaphragmatic aortic cord cross-clamping is not a suitable rat model for spinal cord ischemia/reperfusion injury study as it does not ensure changes in in vivo tissue metabolites concentrations similar to those found in tissues subjected to ischemia/reperfusion.

Adenosine Triphosphate↗

PubMed1979

The safe time limit of temporary clamping of cerebral arteries in the direct surgical treatment of intracranial aneurysm under moderate hypothermia.

Of 274 operated cases of cerebral aneurysm, temporary occlusion of the cerebral arteries was used in 215 cases (79%). Of the 215 cases, 177 (82%) showed no sequelae. The maximum safe time limit for temporary occlusion at the bilateral A1 portion of the anterior cerebral arteries was 48.5 min at 26 degrees C, 47 min at 27 degrees C, and 42 min at 28 degrees C; at the M1 portion of the middle cerebral arteries, it was 30 min at 26 degrees C, 35 min at 27 degrees C, 36 min at 27.5 degrees C, 40 min at 30 degrees C and 19 min at normothermia; and at the dominant A1 portion, in cases of hypoplasia at the contralateral A1 portion, it was 82 min at 26 degrees C, 86 min at 27.5 degrees C, and 63 min at 28 degrees C. Consequently, when performing direct surgery on aneurysms of the anterior communicating artery, unilateral clamping of the A1 portion prevents rupture during surgery and has the advantage of prolonging the occlusion time. Neurological sequelae may have been caused by the temporary occlusion of the cerebral artery in one case, and by the temporary occlusion or the surgical operation in six cases. Of the 22 fatal cases, only one was thought to be due to the temporary occlusion of the cerebral artery. Intermittent release of the clamping for 5 to 10 min is considered to be effective in prolonging the safe time limit of temporary clamping of the cerebral arteries in surgery of cerebral aneurysm under moderate hypothermia.

Adult↗

PubMed1987

Extra-anatomical bypass formation and exclusion of thoracic aortic aneurysms by "paired clamp method": the development of hind leg paralysis, the thrombus formation and the pressure ratio between the excluded cavity and the aorta.

The extra-anatomical bypass formation and the exclusion of thoracic aortic aneurysms by the "paired clamp method" applied to the thoracic aorta of mongrel dogs, and the development of hind leg paralysis was studied experimentally in relation to the ratio between the mean excluded cavity pressure and the mean aortic pressure ratio (EA-ratio). The relationship between thrombus formation in the excluded cavity and the EA-ratio was also studied. Animals were divided into 4 groups: Group 1 underwent the cross-clamping of the descending thoracic aorta for 8 min; Group 2 underwent exclusion of the entire thoracic aorta under permanent bypass; Group 3 underwent ligation of 2/3 of the proximal intercostal arteries which branched from the excluded thoracic aorta; and Group 4 underwent division of the excluded thoracic aorta into 3 parts by ligation. No animals in group 1 developed paralysis. When EA-ratios were higher than 0.48, animals in groups 2 and 3 were not paralyzed, whereas all but 1 animals with EA-ratios lower than or equal to 0.48 were paralyzed. There was statistically significant difference between the EA-ratio of the non-paralyzed animals and that of the paralyzed animals in groups 2 and 3. Four out of 5 animals in group 4 were paralyzed. However, there was no statistically significant difference between the EA-ratio in these 4 paralyzed animals and that in the non-paralyzed animals in groups 2 and 3. When the EA-ratio was lower than or equal to 0.59, all but 1 excluded cavities of groups 2 and 3 animals were fully thrombosed 7 or 8 days after the operation. None of these animals showed the aggravation of the paralysis during the observation period and, conversely, the paralysis of almost all animals was ameliorated. These results suggested that the EA-ratio is useful in predicting the development of paralysis and thrombus formation in the excluded cavity after the operation of thoracic aortic aneurysms by the "paired clamp method".

Animals↗

PubMed1986

Insulin sensitivity and exogenous insulin clearance in Graves' disease. Measurement by the glucose clamp technique and continuous indirect calorimetry.

Insulin sensitivity was measured in a group of seven thyrotoxic patients and in a group of seven normal subjects by means of the glucose clamp technique. Infusion of insulin at a rate of 0.80 +/- 0.05 mU/kg X min in the hyperthyroid patients and of 0.55 +/- 0.04 mU/kg X min in the control group was performed to obtain a steady-state plasma insulin concentration of approximately 50 microU/ml. Substrate oxidation rates were measured in the postabsorptive state and during the 2 h of the clamp by means of continuous indirect calorimetry. In the postabsorptive state, hyperthyroid patients presented a preferential oxidation of lipids. During the period 60-120 min of the clamp, mean plasma glucose (92 +/- 2 versus 93 +/- 2 mg/dl), insulin (50 +/- 5 versus 58 +/- 3 microU/ml), and total glucose metabolism (5.8 +/- 0.7 versus 6.1 +/- 0.3 mg/kg X min) were similar in the hyperthyroid patients and the control subjects. The rate of glucose oxidation was higher in hyperthyroid patients than in control subjects (4.3 +/- 0.5 versus 2.2 +/- 0.2 mg/kg X min, P less than 0.001), while that of lipid oxidation was similar in both groups (0.6 +/- 0.2 versus control 0.7 +/- 0.1 mg/kg X min). The calculated metabolic clearance rate of insulin was markedly higher in the hyperthyroid patients (1144 +/- 132 ml/min) than in the normal subjects (812 +/- 56 ml/min, P less than 0.025). It is concluded that insulin sensitivity is not altered in the thyrotoxic state. The major route of insulin-stimulated glucose disposal in the hyperthyroid patients appears to be glucose oxidation.

Adult↗

PubMed2005

Use of a rivet-like titanium clamp closure system to replace an external frontal bone flap after transfrontal craniotomy in a dog.

A 10-year-old spayed female dog was referred for surgical removal of a brain tumor that had been identified following an acute onset of seizure activity 2 weeks earlier. A computed tomographic evaluation involving contrast agent revealed the presence of a contrast-enhanced mass within the left olfactory lobe of the brain. After removal of the mass via a transfrontal craniotomy, the overlying frontal bone flap was replaced and secured by use of a biologically inert rivet-like titanium clamp closure system and 3 titanium alloy craniotomy line clamps. On reevaluation 4 weeks after tumor removal, the dog was free of seizure activity and had no proprioceptive deficits; according to the owner, the dog had marked improvement in its overall behavior and attitude. The titanium clamp closure system appears to offer an effective and rapid technique for the secure replacement of craniotomy bone flaps in dogs.

Animals↗

PubMed1985

The application of patch clamp methods to ocular epithelia.

The techniques of patch voltage clamping and whole cell clamping have been applied to the lenses and corneas of several species of animals. Numerous ion channels have been found in the basal and apical membranes of lens epithelial cells, anterior and posterior surface lens fibers, apical membrane of corneal endothelial cells, and apical membrane of the second layer of corneal epithelial cells. No ion channels have been found in deep lens fiber membranes to date. There are 9-11 different kinds of potassium channels in ocular epithelial membranes, several different kinds of non-selective cation channels, and one non-selective channel with a large unit conductance. Sodium selective channels are seen only rarely while chloride selective channels have not been seen at all. Several channels have not yet been identified unequivocally. Using the gigohm seal technique, it is possible to show that the frog lens epithelial cell membrane is dominated by potassium channels. Also, a technique is described for using the reversal potential of a 25-30 pS non-selective cation channel to measure the resting voltage of epithelial cells without penetrating them. The results of lens ion channel localization studies are in only qualitative agreement with previous lens channel localization studies which used whole lens impedance and ion substitution techniques. Limitations of using the patch clamp for ion channel localization are presented.

Animals↗

PubMed1978

Endothelial lesions associated with vascular clamping--surface micropathology by scanning electron microscopy.

The endothelial cell pavement in normal blood vessels is very fragile. In cardiovascular surgery, the need for secure clamping of the aorta results in trauma which may be followed by thrombosis or occlusion. Various types of vascular clamps and other related devices offered commercially were clinically investigated in canine models and their effects on the vascular endothelium were ascertained with the aid of scanning electron microscopy. On the basis of these studies, the Fogarty silicone filled clamp appeared to be the least traumatic. However, further technical developments in this area are needed in order to obtain a completely atraumatic method of temporarily closing major blood vessels.

Animals↗

PubMed1976

Oesophageal clamp anastomosis and stricture formation. An experimental study in the piglet.

End-to-end oesophageal anastomoses were performed with a metal clamp in 8 piglets. A transanastomotic catheter was kept in position for 5 weeks following release of the clamp. The results were evaluated by contrast radiography after a further 2 weeks. All the animals survived the operation and the pre-determined observation period. All the anastomoses healed without signs of leakage. They showed strictures of varying degrees, as assessed by radiography of the specimens. The dissected specimens showed scarred changes in the anastomoses where the thin mucosa was regenerated. The results are explained by the fact that the method of clamp anastomosis per se leads to a mucosal defect at the site of anastomosis with ensuing secondary wound healing. The intraluminal tube therby prevents wound contraction with luminal obliteration by giving the mucosa time to regenerate.

Animals↗

PubMed1995

Myocardial reperfusion after coronary bypass surgery. Suture of only distal or all anastomoses with the aorta cross-clamped?

Sixty patients undergoing elective coronary artery bypass grafting were randomly allocated into two groups, each of 30 patients and similar as regards age, sex, number of coronary artery bypasses and left ventricular ejection fraction. In group A the proximal anastomoses of vein grafts were sutured after aortic declamping during partial occlusion of the aorta, and in group B these anastomoses were done during aortic cross-clamping. The aortic cross-clamp time was significantly longer in group B than in group A (72 vs 57 min, p < 0.0001). Myocardial cooling and rewarming and the number of sustained or possible perioperative myocardial infarctions were equal in both groups. Central haemodynamics showed no intergroup difference, before or after induction of anaesthesia or at the end of surgery. Conduction disturbances were more common in group A than in group B (12 vs 3, p = 0.0246), and transient external pacing was more often required in group A (9 vs 2, p = 0.0534). Myocardial reperfusion via native coronary arteries and bypass grafts gives better protection against conduction disturbances than does reperfusion via only native arteries, despite longer aortic cross-clamping time.

Anastomosis, Surgical↗

PubMed1985

Revascularization of the extracranial vertebral artery at any level without cross-clamping.

Hemodynamic insufficiency resulting from extracranial vertebral artery stenosis or occlusion is believed to be the major cause of vertebrobasilar transient ischemic attacks. The major difficulties in treating this disorder have been exposure of the vertebral artery distal to the stenosis and the risk of vertebral artery cross-clamping for vein grafting or carotid artery transposition. The authors describe a new technique for vertebral artery reconstruction at any level by the use of an intraluminal shunt, thus avoiding the necessity to cross-clamp the artery. This procedure was successfully performed at all three levels of the extracranial vertebral artery: C7-4, C3-1, and C-1 to the foramen magnum. The technique of exposure of the vertebral artery at these three levels and the method of vein grafting without cross-clamping are described. The initial results of the procedure are presented.

Aged↗

PubMed1988

A simple technique to measure regional cerebral blood flow during intravascular balloon clamping.

A case of giant internal carotid ophthalmic aneurysm was presented. In order to clarify whether the patient could tolerate carotid occlusion, a balloon clamping test was performed. before surgery. The cerebral blood flow was measured using early imaging by single photon emission computed tomography (SPECT) with N-isopropyl-(iodine-123)-p-iodoamphetamine (123I-IMP). When the balloon clamping test was performed the tracer was injected, and scanning was performed 35 minutes after removing the catheter. This tracer enabled a "memory of blood flow" during temporary ischemia to determine the character of quick diffusion and slow wash out, that could not be performed by other methods of cerebral blood flow measurement. SPECT with 123I-IMP can simplify the measurement of cerebral blood flow during the balloon clamping test.

Adult↗

PubMed1999

The effect of direct lidocaine injection into the clamped aortic segment on the spinal evoked potential: early diagnosis for spinal cord ischemia.

PURPOSE: The aim of this study was to identify a method to determine whether segmental artery reconstruction was indicated during aortic clamping. METHOD: Spinal cord evoked potential (SCEP) and regional spinal blood flow were studied in 24 adult dogs. Using the left heart bypass technique, aortic clamping divided the aorta into thoracic, abdominal, and terminal segments. After the occlusion of the descending aorta and discontinuation of the perfusion to the abdominal segment, animals were assigned to four groups: no treatment with perfusion to the terminal aorta (group IA), no treatment with cessation of bypass (group IB), 5% lidocaine administration (5 mg/kg) into the abdominal segment with perfusion to the terminal aorta (group IIA), and lidocaine administration with cessation of bypass (group IIB). RESULTS: Cessation of bypass reduced spinal blood flow and SCEP amplitude. Lidocaine injection allowed for a significant rapid decrease in SCEP amplitude in group IIB compared with group IB (24.2% +/- 13.4% versus 92.3% +/- 33.2%; p = 0.0039). The degree of spinal blood supply was reflected immediately in the magnitude of SCEP amplitude change by the direct lidocaine injection. (group IB versus group IIB; p = 0.023). CONCLUSION: The direct injection of lidocaine into the clamped aorta results in a rapidly change in SCEP in the threat of ischemia and can be used to make an early detection of the segmental arteries perfusing to the spinal cord.

Analysis of Variance↗

PubMed1999

Clamping ischemia, threshold ischemia and delayed insertion of the shunt during carotid endarterectomy with patch.

BACKGROUND: Shunt insertion during carotid endarterectomy (CEA) is mandatory to avoid neurological damage due to clamping ischemia; however shunt insertion before plaque removal has many inconveniences (atheroembolism, intimal dissection, difficulty of endarterectomy). The aim of this study is to verify whether and how long shunt insertion may be safely delayed to permit plaque removal and ensure cerebral perfusion during the further time consuming manoeuvres of CEA (peeling, patch angioplasty). METHODS: From July 1990 to February 1996 383 patients underwent 411 CEAs under general anesthesia with EEG continuous monitoring and PTFE patch angioplasty. A Pruitt-Inahara shunt was routinely inserted only after atherosclerotic plaque removal. In 316 CEAs (76.9%) without EEG signs of cerebral ischemia (Group A) the mean clamping time was 10 min +/-4.8 (range 2-37 min). In 95 CEAs (23.1%) with EEG signs of cerebral ischemia (Group B) it was 7.3 min +/-3.5 (range 3-20 min). All patients had normal EEG signals after delayed shunt insertion and reperfusion (mean 21 min, range 5-45 min). RESULTS: In the short term results (within 30 days) there was a relevant neurological complication rate of 0.96% (2 major stroke and 2 lethal stroke); at awakening we observed 5 RINDs (1.21% of total) 1 in a patient of Group A (0.31%) and the other 4 in patients of Group B (4.21%). CONCLUSIONS: These data confirm the rationale of a delayed insertion of the shunt: actually the cerebral parenchyma may tolerate under general anesthesia a sufferance due to carotid clamping, EEG detectable, without neurological deficits for at least 7.3 min. This time is sufficient to perform the most difficult steps of CEA (plaque removal, distal intima checking) allowing shunt insertion in a clean operatory field, without inconveniences. Finally the shunt allows complementary time consuming steps, as patch angioplasty, with improvement of both short- and long-term results.

Aged↗