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PubMed2002

Endoscopic thoracic sympathectomy for hyperhidrosis: experience with both cauterization and clamping methods.

The goal was to review results of sympathectomy, performed with use of either cauterization or clamping, in patients with hyperhidrosis (n = 1,312): 653 early patients undergoing electrocautery sympathectomy, 305 later patients undergoing cauterization, and 354 patients treated with a clamping procedure. Patients were interviewed by telephone about the status of symptoms, adverse outcomes, and satisfaction. Palmar hyperhidrosis was cured in all but one patient, with a 98% satisfaction rate in the clamping group and 94.3% and 95.1% in the two cauterization groups ( < or = 0.025, clamping > cauterization). Facial sweating or blushing was cured in the majority (88%) of the 301 patients reporting this symptom. Severe compensatory hidrosis occurred in less than 6% (3% of the clamping group; < or = 0.001, clamping < cauterization). Recurrence rate was 3.0%. A number of factors were related to outcome. Endoscopic thoracic sympathectomy with clamping appears to be at least as safe and effective as earlier cauterization techniques, with the potential advantage of reversibility in those patients unhappy with the outcome.

Adolescent↗
PubMed2002

A three-stage alcohol clamp procedure in human subjects.

BACKGROUND: Multiple factors can influence blood alcohol levels (BALs) after oral ethanol intake. To minimize the variability in BALs, an alcohol "clamping" method in which alcohol is administered intravenously has been previously reported. We have modified this method and developed a multistage alcohol clamp procedure in humans. METHODS: Infusion of alcohol to achieve sequentially increasing steady-state BALs at 50, 100, and 150 mg/dl (e.g., an alcohol clamp procedure) was performed in five subjects. The method used intravenous infusion of 6% alcohol in saline and followed a protocol generated by a physiologically based pharmacokinetic model for alcohol infusion. Real-time measurement of BALs was used to base decisions for necessary adjustments in the infusion rates on a negative feedback principle to achieve and maintain the desired BALs. Additionally, in three of these subjects, breath alcohol levels were determined simultaneously with BAL measurements. RESULTS: A three-stage alcohol clamp procedure was used to achieve BALs of 50, 100, and 150 mg/dl. The intra-assay and interassay variations for measurement of BALs were 1.6 and 2.1%, respectively. The coefficients of variation for the 50, 100, and 150 mg/dl alcohol clamps were 9.8, 5.6, and 4.6%, respectively. The deviation from target BALs for the three clamps were less than 5%. Breath alcohol levels were lower than BALs across all time points, with the mean ratio between the two being 0.84. Correlation analysis showed a very strong correlation between the two alcohol measurement methods ( r= 0.96; p < 0.001). CONCLUSIONS: A three-stage alcohol clamp procedure (50, 100, and 150 mg/dl) has been developed by following a protocol generated with a physiologically based pharmacokinetic model for alcohol infusion in human subjects. This is a suitable procedure to examine the responses on cognitive measures and physiologic parameters under steady states of desired BALs.

Breath Tests↗
PubMed2003

Atrial natriuretic peptide infusion improves ischemic renal failure after suprarenal abdominal aortic cross-clamping in dogs.

OBJECTIVE: The suprarenal abdominal aortic cross-clamping during aortic aneurysm repair causes renal dysfunction after surgery. Atrial natriuretic peptide (ANP), a hormone synthesized by the cardiac atria, induces diuresis-natriuresis and increases glomerular filtration rate. Therefore, we tested the hypothesis that prophylactic ANP infusion could limit the development of acute renal failure after aortic cross-clamping. DESIGN: Prospective, comparative, experimental study. SETTING: Laboratory at a university hospital. SUBJECTS: Twelve male beagle dogs (10-13 kg) with mechanical ventilation under pentobarbital anesthesia. INTERVENTIONS: A catheter was inserted into the femoral vein, and lactated Ringer solution (10 mL/kg/hr) was administered throughout the study period. Two groups of animals were studied: the control group (n = 6), which received saline vehicle before and after suprarenal abdominal aortic cross-clamping for 1.5 hrs; and the ANP group (n = 6), which received ANP (1 microg/kg/min) for 5 hrs, starting from 10 mins before suprarenal abdominal aortic cross-clamping until the end of procedure. MEASUREMENTS AND MAIN RESULTS: Changes in systemic and renal hemodynamics, blood gases, and renal function were measured at baseline and 1, 2, 3, 4, and 5 hrs after aortic cross-clamping. After aortic cross-clamping, urine volume, renal blood flow, and creatinine clearance significantly (p <.01) decreased, and serum creatinine concentrations significantly (p <.01) increased, but these effects were limited by continuous ANP infusion. CONCLUSIONS: The present study shows that ANP infusion preserved renal function after suprarenal abdominal aortic cross-clamping in dogs. These results justify a trial of ANP infusion in humans during aortic aneurysm repair.

Acute Kidney Injury↗
PubMed2005

Effects of intrarenal administration of the cox-2 inhibitor parecoxib during porcine suprarenal aortic cross-clamping.

The aim of this study was to investigate the effects of intrarenal administration of the cyclooxygenase-2 inhibitor parecoxib during suprarenal aortic cross-clamping. In a prospective, controlled, blinded, randomized manner, 16 anesthetized and mechanically ventilated pigs were instrumented to measure systemic and right kidney hemodynamics, oxygen exchange, and metabolism. During 45 min of suprarenal aortic cross-clamping, animals received 40 mg of parecoxib (n = 8) or vehicle (n = 8) infused continuously into the right renal artery. Hemodynamic and metabolic data, right kidney venous blood, as well as urine samples were obtained before clamping, as well as before and 75 and 195 min after declamping. Clamping transiently increased mean arterial pressure in both groups. Systemic and renal blood flow did not differ between the pre- and postclamping measurements or between groups. Parecoxib attenuated the otherwise significant fall in right kidney creatinine clearance (controls: from 45 [7;111] to 17 [9;22] mL/min; parecoxib: from 39 [3;59] to 27 [11;45] mL/min, P = 0.039 and P = 0.297, respectively versus before clamping, P = 0.021 versus controls at 195 min) and prevented the impairment of renal lactate balance observed in the control group (controls: from 0.5 [-0.8;3.5] to 0.2 [-0.2;0.6] mumol/kg/min; parecoxib: from 0.6 [-1.0;2.0] to 0.4 [-1.2;0.6] mumol/kg/min, P = 0.038 and P = 0.285, respectively, versus before clamping). In conclusion, intrarenal parecoxib infusion beneficially influenced kidney function in this clinically relevant model of suprarenal aortic cross-clamping.

Angiography↗
PubMed2007

A cadaver study of the trochanteric pelvic clamp for pelvic reduction.

OBJECTIVE: The purpose of this study is to evaluate the ability of the trochanteric pelvic clamp to reduce anterior-posterior compression pelvic ring disruptions. DESIGN: Eight fresh-frozen cadavers underwent sequential disruption of the pelvic ring to represent both anterior-posterior compression type II (APC II) and anterior-posterior compression type III (APC III) injury patterns. Reduction with the trochanteric pelvic clamp was performed. Prereduction and postreduction anterior/posterior pelvic displacements were determined radiographically. SETTING: Institutional research laboratory. INTERVENTION: Application of a trochanteric pelvic clamp to reduce a pelvic ring disruption. MAIN OUTCOME MEASURE: Radiographic measurements of anterior and posterior pelvic displacement were evaluated and compared to similar values after reduction with the trochanteric pelvic clamp. RESULTS: The application of the trochanteric pelvic clamp to simulated APC II and APC III pelvic injuries in a cadaver model demonstrated a significant reduction of the anterior pubic diastasis and the posterior disruption of the sacroiliac joint. Anterior pelvic vertical displacement did not improve with application of the trochanteric pelvic clamp. Measurement of symphysis diastasis for APC II injuries was 4.07 cm (+/-0.31) prereduction and 0.38 cm (+/-0.18) postreduction, (P < 0.001); for APC III injuries, 6.32 cm (+/-0.84) prereduction and 1.24 cm (+/-1.01) postreduction, (P < 0.001). For posterior sacroiliac disruptions, APC II injury measurements were 1.81 cm (+/-0.35) prereduction and 0.69 cm (+/-0.32) postreduction (P < 0.001); for APC III injuries, 3.81 cm (+/-1.06) prereduction and 1.86 cm (+/-0.82) postreduction (P = 0.002). At the symphysis pubis, APC II vertical displacement was 0.32 cm (+/-0.36) prereduction and 0.30 cm (+/-0.38) postreduction (P < 0.740); for APC III injuries, 0.5 cm (+/-0.31) prereduction and 0.88 cm (+/-0.53) postreduction (P < 0.098). CONCLUSIONS: The application of the trochanteric pelvic clamp is reliable for obtaining reduction of anterior-posterior compression pelvic injuries in a cadaver model.

Aged↗
PubMed1996

Effect of various irrigant and autoclaving regimes on the fracture resistance of rubber dam clamps.

Rubber dam clamps are known to break during clinical use in endodontics. This in-vitro study examined some of the variables which may contribute to the fracture. Stainless steel rubber dam clamps were subjected to various cleaning and autoclaving regimes and exposure to various solutions of sodium hypochlorite (NaOCl). Each clamp was examined after four cycles of cleaning and exposure to NaOCl. During environmental exposure to NaOCl, the clamp was stressed over a perspex rod to simulate placement onto the crown of a tooth. Clamps were examined after each test cycle visually and microscopically, or immediately after breakage. Results suggested that the fractures were because of a stress corrosion cracking phenomenon. There was evidence of intergranular and transgranular cracking of the metal. Corrosion spots were seen on the surface of the clamps and fracture occurred mainly through these spots. A number of recommendations to reduce breakage of clamps have been suggested.

Corrosion↗
PubMed1997

Delayed umbilical cord clamping in preterm infants: a feasibility study.

OBJECTIVES: To assess: (i) the size of placental transfusion following a 30 s delay in cord clamping following vaginal and Caesarean births; and (ii) the feasibility of delaying cord clamping in the labour ward and particularly in the operating theatre. METHODS: Fourty-six infants born at 26-33 weeks gestation were randomized to having the umbilical cord clamped either immediately or 30 s after birth. The venous haematocrit was measured at 1 and at 4 h of age. RESULTS: There were trends towards higher mean haematocrits in the infants following delayed clamping, but these were not significant either at 1 h (55 +/- 7.7 vs 52.9 +/- 7) or at 4 h of age (55 +/- 7 vs 52.5 +/- 7). The trends were more marked in the infants born by Caesarean section, and in those born at 26-29 weeks gestation. CONCLUSIONS: A 30 s delay in cord clamping is feasible at both vaginal and Caesarean births, but does not lead to the predicted difference in infant haematocrit. Although physiological studies suggest that a placental transfusion of 15-20 mL/kg occurs within 30 s of delivery, these data suggest that future trials should either delay cord clamping for more than 30 s, or should alter the position of the infant in relation to the uterus in order to facilitate the transfusion. Delayed cord clamping is feasible at Caesarean section.

Blood Transfusion, Intrauterine↗
PubMed1992

The effect of early and late cord-clamping on blood viscosity and other hemorheological parameters in full-term neonates.

This study was done to compare postnatal alterations in blood viscosity (capillary viscometer) and its determinants: hematocrit, plasma viscosity (capillary viscometer), red cell aggregation (Myrenne aggregometer) and red cell deformability (rheoscope) in the first five days of postnatal life in full-term neonates with early (< 10 s) and late (3 min) cord-clamping. The fetal blood volume of the placenta ("residual placental blood volume") decreased from 52 +/- 8 ml/kg of neonatal body weight after early cord-clamping to 15 +/- 4 ml/kg after later cord-clamping. Neonatal blood volume, calculated as the difference between an assumed total feto-placental blood volume of 115 ml/kg and the measured fetal blood volume of the placenta, was 50% higher in the late cord-clamped infants than in the early cord-clamped infants. Both groups showed similar viscosity, hematocrit and other rheological parameters in cord blood. In the infants with early cord-clamping, the hematocrit decreased from 0.48 +/- 0.04 l/l at birth to 0.43 +/- 0.6 l/l after 24 h (p < 0.05). Whole blood viscosity did not change significantly with age. After late cord-clamping, the hematocrit rose from 0.50 +/- 0.04% at birth to 0.63 +/- 0.05 l/l at 2 h of age (p < 0.005) and dropped to 0.59 +/- 0.5 l/l (p < 0.05) at 24 h. Blood viscosity increased by 40% (p < 0.001) within the first 2 h, but did not change significantly during the following five days. In both groups, plasma viscosity and red cell aggregation increased significantly (p < 0.05) on day 5 due to significant increases in total plasma protein and fibrinogen concentrations (p < 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)

Blood Proteins↗
PubMed1997

Acute cortisol responses of lambs castrated and docked using rubber rings with or without a castration clamp.

OBJECTIVE: To measure the plasma cortisol response in lambs castrated and docked by three different methods (ring castration and tail docking, ring and clamp castration and tail docking; ring and clamp castration and ring tail docking) for 4 h after treatment. DESIGN: A physiological study with controls. PROCEDURE: A rubber ring was applied to the scrotum. Then the castration clamp was placed, distal to the ring, on each spermatic cord such that there was no overlap of the crush lines. RESULTS: There were no differences in the cortisol secretion of the lambs castrated and tail docked by the ring only and by the ring plus castration clamp methods. Using the castration clamp in addition to the ring on the tail had no effect on cortisol secretion. CONCLUSIONS: Using the castration clamp did not appear to reduce the cortisol response to ring castration and docking, as demonstrated elsewhere, because the areas of uncrushed tissue between the two castration clamp crush lines allowed nociception from ischemic scrotal tissue to be transmitted cranially via undamaged nerve fibers.

Analysis of Variance↗
PubMed1979

Extracellular potassium accumulation in voltage-clamped frog ventricular muscle.

1. Application of voltage clamp pulses (1--10 sec) to frog ventricular strips causes temporary changes in the extracellular K concentration. 2. The changes in the extracellular K concentration can be estimated from (a) slowly decaying post-clamp after-potentials, (b) changes in the action potential duration, and (c) measurements with a K-selective micro-electrode. 3. The depolarization of the resting potential and the shortening of the action potential are present in approximately the same proportions during voltage-clamp induced extracellular K accumulation and during perfusion with a K-ricn Ringer solution but small consistent differences are noticed. 4. The measurements of the after-potential, the action potential shortening, and the K-electrode response were analysed as indicators of extracellular K+ activity and it was concluded that the after-potential provides the most convenient and reliable estimate of the absolute magnitude of the voltage-clamp induced extracellular K accumulation. 5. The depolarizing after-potentials decay more slowly than the hyperpolarizing after-potentials but it is found that this reflects the selectivity of the membrane to K+ concentrations as predicted by the Nernst or the Goldman equations. 6. Analysis of the redistribution of accumulated K+ from the decay of the after-potential suggests that the major part of the redistribution process can be described by a single time constant (2--4 sec). A much longer time constant is required for a smaller component of the 'tail' in order to bring [K]o to the normal resting state. 7. N-shaped relations similar to the 'steady state' current-voltage relation are obtained when the post-clamp after-potential, the action potential shortening, and the K-electrode response are plotted versus the clamped membrane potential. The maxima of these curves are located around -40 mV and the minima around -20 mV. 8. In spite of a significant outward membrane current (1--1.5 microamperemeter) in the minimum region (-20 mV), the post-clamp after-potential is often hyperpolarizing in nature suggesting extracellular K depletion. 9. These findings indicate that the K efflux is lower at -20 mV than at both higher and lower potentials and suggest that the N-shape 'steady state' current-voltage relation mainly reflects the voltage dependency of the K current. 10. A theory for K accumulation in a single compartment is presented which predicts that a simple linear RC-circuit may describe the electrical response of the preparation in a limited potential range around the resting potential. The extracellular accumulation space was estimated to be 13--16% of the total volume of the preparation. It is tentatively suggested that the accumulation space is equivalent to the subendothelial fraction of the extracellular space.

Action Potentials↗
PubMed1992

Regulation of acute parathyroid hormone release in normal humans: combined calcium and citrate clamp study.

The objective of the present study was to elucidate the dynamics of parathyroid hormone regulation, with particular reference to the mechanism controlling the acute parathyroid hormone release. Through utilization of the citrate clamp technique and the calcium clamp technique we were able, in a standardized way, to stimulate and suppress the parathyroid hormone secretion. Precise bedside measurements of blood ionized calcium and measurements of intact parathyroid hormone were performed. Twelve healthy young volunteers participated in two trials 6-12 wk apart, a citrate clamp (delta-blood ionized calcium -0.19 mmol/l) and a calcium plus citrate clamp (delta-blood ionized calcium +0.22 mmol/l and -0.19 mmol/l). During the citrate clamp, preceded by normal calcemia, serum intact parathyroid hormone peaked to a maximum after 5-10 min, four to six times above baseline concentration and then declined to a steady state two to three times above baseline concentration. During the citrate clamp, preceded by hypercalcemia induced by a calcium clamp, serum intact parathyroid hormone also peaked immediately to about five to nine times above its suppressed level, approximately two times above the baseline concentration. Subsequently, serum intact parathyroid hormone declined to a steady state just below the baseline concentration. In conclusion, within the range studied, the mechanism eliciting the acute serum intact parathyroid hormone release from its depot is a fall in blood ionized calcium, not the absolute concentration of ionized calcium.

Adult↗
PubMed1985

Glucose clamping and cardiovascular function in endotoxic dogs.

Fasted mongrel dogs were anesthetized with pentobarbital sodium and instrumented for the continuous measurement of blood glucose (BG), a lead II electrocardiogram, and pressures in the left ventricle (LV), pulmonary artery, and aorta. Cardiac output was measured every 15 min using thermodilution and LV stroke work, and pulmonary and systemic resistances were calculated. After a 30-min pretreatment period, glucose clamping was initiated. The desired glucose levels were reached within 45 min (hypoglycemic 20 +/- 1 mg/dl, n = 11; normoglycemic 85 +/- 1, n = 7; hyperglycemic 156 +/- 3, n = 7). At this point dogs were treated with either endotoxin (8 mg/kg to 6 hypoglycemic, 4 normoglycemic, and 4 hyperglycemic) or saline (5 hypoglycemic, 3 normoglycemic, and 3 hyperglycemic). All infusions were terminated after 2 h glucose clamping, and all dogs were monitored either until death or for a maximum of 10 h. Hypoglycemic clamping curtailed survival in endotoxic dogs. Hyperglycemic clamping markedly prolonged survival. Normoglycemic clamping left survival time unchanged compared with untreated dogs. The effects of glucose clamping on cardiovascular function during endotoxic shock paralleled the effects on survival. Cardiovascular function was also depressed in hypoglycemic-clamped saline dogs. It is concluded that glucose dyshomeostasis may be a crucial factor in the development of fatal cardiovascular dysfunction and shock after endotoxin administration.

Animals↗
PubMed1977

Effect of aortic clamping on proximal reabsorption and sodium excretion in the rat.

It has been suggested that aortic clamping prior to expansion of the extracellular fluid volume prevents the natriuretic response normally seen in this setting. To further evaluate this finding, two groups of re-collection micropuncture studies were performed before and after 7.5% body wt expansion with Ringer solution. Group I, immediate-clamp studies, n, 11. After control collections, perfusion pressure to the left kidney was decreased to 75 mmHg followed by Ringer loading. Group II, delayed-clamp studies, n, 8. After control collections, Ringer solution was given for 40 min. Then the left renal perfusion pressure was reduced to 75 mmHg and the Ringer infusion was continued at the same rate. In the immediate-clamp group, there was no change in total kidney glomerular filtration rate (GFR) (1.16 vs. 1.11 ml/min), nephron GFR (40 vs. 39 nl/min), tubular fluid-to-plasma inulin ratio (2.40 vs. 2.28), or filtrate delivery out of the proximal tubule (18 vs. 18 ndium excretion were not significantly altered. In the delayed-clamp studies, there was also no change in total or nephron GFR, but the tubular fluid-to-plasma inulin ratio fell from 2.52 to 1.65 (P less than .001) and distal delivery rose 9 nl/min after expansion (P less than .001). Sodium excretion increased 3.83 mueq/min and fractional sodium excretion rose 2.28%, both values being markedly greater than in the immediate-clamp studies (P less than .005 for both). These results demonstrate that immediate clamping obviates the fall in proximal reabsorption and the natriuretic response to Ringer loading and suggests that intrarenal adjustments are a major determinant of the magnitude of the natriuretic response to expansion of the extracellular volume

Animals↗
PubMed1993

Paraplegia following thoracic aortic cross-clamping in dogs. No difference in neurological outcome with a barbiturate versus isoflurane.

BACKGROUND AND PURPOSE: We compared the incidence and severity of paraplegia following thoracic aortic cross-clamping in dogs for two anesthetic regimens. Animals were randomly assigned to receive methohexital (group M; n = 9) or isoflurane (group I; n = 9). We expected a better neurological outcome in animals administered methohexital because of superior neuronal protection and greater spinal cord perfusion pressure (mean arterial pressure below the cross-clamp site minus mean cerebrospinal fluid pressure). METHODS: After surgical preparation and a 30-minute stabilization period, dogs in group M received 14 +/- 6 mg.kg-1 i.v. methohexital to induce an isoelectric electroencephalogram followed by a continuous infusion of methohexital at 20 mg.kg-1 x h-1. Dogs in group I received 1.4 +/- 0.2% end-tidal isoflurane (1 minimum alveolar concentration). The thoracic aorta was then occluded 2.5 cm distal to the left subclavian artery for 30 minutes and then released. Hemodynamics and cerebrospinal fluid pressure were measured at (1) baseline, (2) 2 minutes after aortic cross-clamping, (3) 20 minutes after aortic cross-clamping, (4) 5 minutes after aortic unclamping, and (5) 30 minutes after resuscitation. At 24 hours a neurological assessment was performed. After the clinical assessment the dogs were killed and the spinal cord removed immediately for histopathologic study. RESULTS: There were no differences in nasopharyngeal temperature, PaCO2, pH, or hemoglobin at any time between groups. With cross-clamping, the spinal cord perfusion pressure decreased precipitously. However, there was no difference in spinal cord perfusion pressure between groups at any time (P = .5555). The neurological outcome, assessed at 24 hours after thoracic aortic cross-clamping by a veterinarian unaware of the anesthetic protocol, was not different between groups (P > .5, two-tailed Mann-Whitney rank-sums test). When anesthetized with methohexital 5 of 9 dogs were paraplegic; with isoflurane 7 of 9 dogs were paraplegic. By Spearman's rank test, a strong inverse correlation between the Tarlov score and the ratio of dead to total lumbar anterior spinal cord neurons was seen (Spearman's correlation coefficient = -.8358; P = .0001). CONCLUSIONS: We conclude that no advantage was offered by the choice of anesthesia to neurological outcome after 30 minutes of thoracic aortic cross-clamping in this canine model.

Analysis of Variance↗
PubMed2000

Preoperative MRA flow quantification in CEA patients: flow differences between patients who develop cerebral ischemia and patients who do not develop cerebral ischemia during cross-clamping of the carotid artery.

BACKGROUND AND PURPOSE: We sought to investigate whether preoperative volume flow in the internal carotid arteries (ICAs), the basilar artery (BA), and the middle cerebral arteries (MCAs) and collateral flow via the circle of Willis differ between patients who do and patients who do not develop cerebral ischemia during clamping of the carotid artery in carotid endarterectomy (CEA). METHODS: Quantitative volume flow in the ICAs, BA, and MCAs and directional flow in the circle of Willis were measured preoperatively with 2-dimensional phase-contrast MR angiography in 86 CEA patients. During the operation, electroencephalographic (EEG) recordings were obtained that were monitored by a clinical neurophysiologist. Reference volume flow values were assessed in 24 control subjects. RESULTS: In patients with an ICA stenosis without contralateral ICA occlusion (n=62), of whom 16% developed ischemic EEG changes during clamping, preoperative flow in the clamped ICA was significantly higher in patients with cerebral ischemia than in patients without (mean, 278 versus 160 mL/min; P:<0.05). Flow in the contralateral ICA (156 versus 273 mL/min; P:<0.01), flow in the BA (116 versus 165 mL/min; P:<0.05), and presence of collateral flow via the circle of Willis to the clamped ICA (0% versus 37%; P:<0.05) were significantly lower. MCA flow did not differ significantly between groups. Additionally, in patients with an ICA stenosis and a contralateral ICA occlusion (n=24), of whom 42% developed cerebral ischemia, preoperative flow in the clamped ICA was significantly higher in patients with cerebral ischemia than in patients without (309 versus 239 mL/min; P:<0.05). BA flow, MCA flow, and presence of willisian collateral flow (0% versus 14%) did not differ significantly between groups. CONCLUSIONS: Preoperative volume flow in the clamped ICA is significantly higher in CEA patients with ischemic EEG changes during clamping than in CEA patients without such changes. The latter patients probably have better developed collateral pathways preoperatively.

Aged↗
PubMed1987

Equivalence of the insulin sensitivity index in man derived by the minimal model method and the euglycemic glucose clamp.

Studies were done to determine whether the minimal model approach and the glucose clamp measure equivalent indices of insulin action. Euglycemic glucose clamps (glucose, G: 85 mg/dl) were performed at two rates of insulin (I) infusion (15 and 40 mU/min per m2) in 10 subjects (body mass index, BMI, from 21 to 41 kg/m2). Insulin sensitivity index (SI) from clamps varied from 0.15 to 3.15 (mean: 1.87 +/- 0.36 X 10(-2) dl/[min per m2] per microU/ml), and declined linearly with increasing adiposity (versus BMI: r = -0.97; P less than 0.001). SI from modeling the modified frequently sampled intravenous tolerance test varied from 0.66 to 7.34 X 10(-4) min-1 per microU/ml, and was strongly correlated with SIP(clamp) (r = 0.89; P less than 0.001). SI and SIP(clamp) were similar (0.046 +/- 0.008 vs. 0.037 +/- 0.007 dl/min per microU/ml, P greater than 0.35); the relation had a slope not different from unity (1.05 P greater than 0.70) and passed through the origin (P greater than 0.40). However, on a period basis, SI exceeded SIP(clamp) slightly, due to inhibition of hepatic glucose output during the FSIGT, not included in SIP(clamp). These methods are equivalent for assessment of overall insulin sensitivity in normal and insulin-resistant nondiabetic subjects.

Adult↗
PubMed2003

Endotension in the closed aneurysm sac during aortic and iliac cross clamping: implications of pressure and flow measurements.

PURPOSE: To relate the mean and pulse pressures in the cross-clamped aortic aneurysm sac to the systemic pressures during open repair (OR) of abdominal aortic aneurysm (AAA). To correlate the intrasac pressures to the number of bleeding lumbar arteries (LA) and the flow pattern of the inferior mesenteric artery (IMA). METHODS: In a prospective study of 55 patients (45 men; median age 69 years, range 47-84) undergoing open repair, the IMA flow and the mean pressure in the aneurysm sac (ASP(mean)) were measured before and after aortic and iliac artery cross clamping. The systemic mean pressure (SP(mean)) was recorded simultaneously. The aneurysm sac (ASP(pulse)) and systemic pulse pressures (SP(pulse)) were calculated, as were the mean pressure ratio (ASP(mean)/SP(mean)) and the pulse pressure ratio (ASP(pulse)/SP(pulse)). Values are given as the median (range). RESULTS: Cross clamping of the proximal aortic neck significantly reduced the mean pressure to 31 mmHg (14-64), with a pressure ratio of 0.39+/-0.14; the pulse pressure decreased to 0 mmHg (0-13) (p<0.001). Additional cross clamping of the iliac arteries did not alter the pressure levels any further. In the patent IMA (n=23), an orthograde median flow of 43 mL/min (2-135) was measured; sequential cross clamping of the aorta and iliac arteries reduced the flow to -6 mL/min (-130 to +21) and -3 mL/min (-120 to +22), respectively. There was no correlation between the pressure ratio and IMA patency, its volume flow, or the number of backbleeding lumbar arteries. CONCLUSIONS: The aneurysm sac is still pressurized with no pulsatility after cross clamping during open AAA repair. The aneurysm mean and pulse pressures did not correlate to the number of backbleeding lumbar arteries. Finally, the pressure ratios did not correlate to the highly variable IMA flow pattern during aortic cross clamping.

Aged↗
PubMed1993

Lower extremity hypothermia is beneficial during infra-renal aortic cross-clamping in pigs.

The effects of lower extremity hypothermia during aortic cross-clamping are unknown. To compare the effects of lower extremity hypothermia with normothermia during aortic cross-clamping, two groups of six (25-40 kg) anesthetized pigs had their aortas cross-clamped below the renal arteries for 2 h. The cold group had their lower extremities cooled during cross-clamping to a quadriceps muscle temperature of 28 degrees C by using convective cooling. The warm group had the quadriceps muscle temperature maintained at 38 degrees C with convective warming. Saline, 0.9%, was used to maintain the pulmonary capillary wedge pressures at 5 mm Hg in both groups. Reperfusion of the lower extremities resulted in a small but significant decrease in the blood temperature from 36.6 +/- 0.3 degrees C (mean +/- SE) to 35.6 +/- 0.3 degrees C 1 min after reperfusion in the cold group, but did not change the blood temperature in the warm group. Both the cardiac output and the lower extremity arterial flow were greater in the cold group at 1 and 5 min after cross-clamp release. Also one pig in the warm group required resuscitation with 1 mg of epinephrine intravenously to treat severe hypotension and myocardial depression after cross-clamp release. We conclude that hypothermia of the lower extremities may be beneficial for surgery involving aortic cross-clamping.

Animals↗