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At least 199 records · Page 11Linked to original sources
PubMed2003

Changes in cerebral microcirculation during and after abdominal aortic cross-clamping in rabbits: the role of thromboxane A2 receptor.

UNLABELLED: Little is known about any changes in cerebral hemodynamics, during and after abdominal aortic cross-clamping and unclamping, especially in the cerebral microcirculation. We studied the effects of abdominal aortic cross-clamping and unclamping on cerebral pial vessel diameter in the presence or absence of the thromboxane (Tx)A(2) receptor antagonist using a closed cranial window in 27 rabbits. Although infrarenal aortic cross-clamping did not affect pial vessel diameter, release of a 20-min aortic cross-clamp caused pial arterioles to dilate and then constrict. A significant constriction persisted for at least 60 min (maximum, -17% for large [> or =75 micro m] and -28% for small arterioles [<75 micro m] compared with baseline). Topical administration of a TxA(2) receptor antagonist, seratrodast, at 10(-7) M and 10(-6) M, significantly attenuated the constriction of large and small arterioles (at 60 min, -9% and -13% constriction for 10(-7) M, and -6% and -7% for 10(-6) M). Release of a 20-min aortic cross-clamp induced a sustained pial arteriolar constriction. Because this unclamping-induced vasoconstriction was attenuated by topical administration of seratrodast, it was likely partially mediated via the washout of TxA(2) produced in the ischemic region during the clamp and after cross-clamp release. IMPLICATIONS: Abdominal aortic unclamping after a 20-min clamp caused an initial dilation followed by a sustained constriction of pial arterioles. Seratrodast, a thromboxane A(2) receptor antagonist, attenuated the vasoconstriction suggesting that it is at least partly mediated by thromboxane A(2) washed out from the region rendered ischemic by clamping.

Animals↗
PubMed1999

A comparison of the Mogen and Gomco clamps in combination with dorsal penile nerve block in minimizing the pain of neonatal circumcision.

OBJECTIVES: 1) To compare the Mogen and Gomco clamps with regard to pain experienced during neonatal circumcision, and 2) to assess neonatal circumcision pain with and without dorsal penile nerve block (DPNB). DESIGN/METHODS: A randomized, controlled, nonblinded clinical trial; 48 healthy, full-term infants were randomized into one of the following four groups: Gomco vs Mogen with (+) or without (-) DPNB. DPNB+ infants were injected with 0.8 mL of 1% lidocaine before circumcision. DPNB- infants received no placebo injection. Heart rate, respiratory rate, and oxygen saturation (SaO2) during the procedure were monitored and data transferred to computer files by using the Datalab software system. Crying was recorded on videotape. Pre- and postcircumcision saliva samples for cortisol analysis were collected. Heart rate, respiratory rate, SaO2, cortisol changes, and duration of crying were evaluated statistically with two-way analyses of variance and t tests. RESULTS: The type of clamp but not the use of anesthesia was significantly associated with the length of the procedure (mean Mogen time, 81 seconds; mean Gomco time, 209 seconds) and percentage of respiratory rate change. The use of anesthesia but not the type of clamp was significantly associated with percentage of crying time and percentage of SaO2 change during the procedure. Heart rate changes and total crying time were significantly associated with both the type of clamp and the use of anesthesia. Neither clamp type nor anesthesia status was significantly associated with salivary cortisol changes, although the mean increase for the DPNB- group was approximately twice that for the DPNB+ group. Fifty-six percent of infants circumcised with the Mogen clamp and DPNB did not cry at all during the procedure. CONCLUSIONS: DPNB is effective in reducing neonatal circumcision pain with either the Mogen or the Gomco clamp. For a given anesthesia condition, the Mogen clamp is associated with a less painful procedure than the Gomco. The Mogen clamp with DPNB causes the least discomfort during neonatal circumcision.

Circumcision, Male↗
PubMed2026

Metabolomic Responses to Oral Glucose Tolerance Test and Hyperinsulinemic-euglycemic Clamp in CKD.

BACKGROUND: The oral glucose tolerance test (OGTT) captures integrated physiological responses involving intestinal glucose absorption, incretin signaling, and endogenous insulin secretion, whereas the hyperinsulinemic-euglycemic clamp (clamp) isolates insulin-mediated glucose uptake. Comparing plasma metabolomic responses to these two challenges may identify processes specific to intestinal nutrient delivery and how they vary in CKD. METHODS: Targeted plasma metabolomics was performed in 59 adults without diabetes (39 with CKD [eGFR <60 mL/min/1.73 m2] and 20 controls) from the Study of Glucose and Insulin in Renal Disease (SUGAR). Each participant underwent a 75-g OGTT and clamp approximately one week apart. Eighty-eight plasma metabolites were quantified at fasting and during each challenge. Metabolite levels were log-transformed and normalized using Systematic Error Removal Using Random Forest (SERRF). Metabolites were classified using adjusted regression slopes relating OGTT and clamp responses. RESULTS: The mean (SD) age and eGFR were 64 (13) years and 54 (26) mL/min/1.73 m2, respectively, and 41% were female. In the overall cohort, OGTT and clamp induced broad plasma metabolic changes, with 63 (72%) and 76 (86%) metabolites significantly altered from fasting, respectively. Seventy-three metabolites (83%) demonstrated a significant relationship between OGTT and clamp responses. Of these, 22 (25%) exhibited true concordance and 51 (58%) demonstrated similar directional changes but differed in magnitude. A total of 15 (17%) metabolites were discordant or non-corresponding, of which only three were discordant. The non-corresponding metabolites were enriched in amino acid metabolism. Eleven metabolites (13%) demonstrated differential responses between OGTT and clamp by CKD status, involving amino acid and glucose metabolism pathways. CONCLUSIONS: Metabolomic responses to OGTT and clamp were largely directionally concordant but differed in magnitude, with attenuation during OGTT. Discordant metabolites were rare, while non-corresponding metabolites were confined to amino acid pathways. CKD modified OGTT-clamp correspondence for metabolites involved in amino acid and glycolytic metabolism.

Journal Article↗
PubMed1999

A physiologically-based pharmacokinetic (PBPK) model for alcohol facilitates rapid BrAC clamping.

Alcohol clamping is a technique that maintains a constant breath alcohol concentration (BrAC) for prolonged intervals, thereby reducing experimental variance in the time course of organ exposure to alcohol, when compared with oral alcohol administration paradigms. The technique employs an intravenous (i.v.) infusion of an ethanol solution at a rate that is intermittently adjusted based on real-time BrAC measurements. In earlier studies, when the clamped state was induced with an oral ethanol loading dose, the vagaries of gastric emptying and absorption were associated with a 45 min delay (RST: reliable start time) before collection of dependent measurements could be planned with confidence. The objective of the present study was to develop an induction method that provides an earlier RST, and to compare the performance of the two methods. The "quick-clamping" method replaced the oral loading dose with a preprogrammed infusion rate profile. A three-compartment physiologically-based pharmacokinetic (PBPK) model for ethanol was constructed, then tailored to each subject using individualized estimates of model parameters. The model was used to compute the infusion-rate profile that would produce the desired time course of BrAC when infused in the corresponding subject. The two clamping methods were compared in a two-session crossover study in 20 healthy young subjects (10 males, 10 females). Compared with the oral/i.v. method, quick clamping produced a comparable precision in the control of BrACs during the clamped interval, and provided a much earlier RST (mean +/- SE for quick-clamp: 17 +/- 4 min; for oral/i.v. clamp: 45 +/- 7 min). The quick-clamping method enables, for the first time, the examination of the early-phase neuroadaptive responses to alcohol in human subjects.

Alcohol Drinking↗
PubMed1991

Longitudinal study of cerebral spinal fluid drainage in polyethylene glycol-conjugated superoxide dismutase in paraplegia associated with thoracic aortic cross-clamping.

It has been hoped that pharmacologic prophylaxis in thoracic aortic cross-clamping may avert the unpredictable complication of spinal cord paraplegia, may avoid the mechanical difficulties associated with shunts, partial bypass, or monitoring devices, and may serve as a substitute for or as an adjunct to cerebral spinal fluid drainage. Toward this end 21 mongrel dogs were studied in four groups and underwent 60 minutes of thoracic aortic cross-clamping: group I, five with thoracic aortic cross-clamping; group II, five with thoracic aortic cross-clamping and cerebral spinal fluid drainage; group III, five with thoracic aortic cross-clamping, cerebrospinal fluid drainage and intravenous administration of a single dose (5000 units/kg) of polyethylene glycol-conjugated superoxide dismutase (PEG-SOD) given 15 to 20 minutes before thoracic aortic cross-clamping; and group IV, six with thoracic aortic cross-clamping and PEG-SOD. Paraplegia was graded by the Tarlov method at 24 hours and up to 5 days after thoracic aortic cross-clamping. The carotid and femoral artery pressures, the central venous pressure, and core temperature, taken during the experiment and at the time the dogs were killed, were found to be similar between groups. At 24 hours all dogs in group I were paraplegic; groups II and III had no paraplegic dogs (p less than 0.01), and group IV had fewer paraplegic dogs (two of six) than group I (p less than 0.05). Paraplegia was averted in all dogs treated with cerebral spinal fluid drainage, even 5 days after thoracic aortic cross-clamping.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMedDate not supplied

Ferromagnetism and MR imaging: safety of carotid vascular clamps.

Metallic extracranial carotid vascular clamps of the Selverstone, Crutchfield, Poppen-Blaylock, Salibi, Kindt, and tantalum varieties have been placed for treatment of large, giant, or inoperable intracranial aneurysms. To ascertain what adverse effect, if any, MR imaging would have on these clamps, magnetic deflection at 1.5 T was measured for various carotid clamps. Marked magnetic deflection (and torque) was displayed by stainless steel Poppen-Blaylock clamps. Relatively mild magnetic deflection was displayed by the stainless steel Selverstone, Salibi, Crutchfield, and Kindt clamps. Three patients with previously placed carotid clamps (two Selverstone, one Salibi) and one patient with a nonferromagnetic tantalum carotid clip had cranial or cervical MR studies at field strengths ranging from 0.35 to 0.60 T. No patient experienced any discomfort or neurologic sequelae as a result of MR imaging. Although the ferromagnetic clamps created severe "black-hole" artifacts and image distortion within the cervical and facial regions, no significant image degradation was apparent during spin-echo imaging of the brain. The tantalum clip created a far smaller MR artifact than did ferromagnetic clamps and allowed effective spin-echo and gradient-echo imaging in the cervical region. Our findings indicate that most patients with carotid vascular clamps (and nonferromagnetic clips) can probably be imaged safely with MR.

Adult↗
PubMed1987

Monitoring of somatosensory evoked potentials during surgical procedures on the thoracoabdominal aorta. I. Relationship of aortic cross-clamp duration, changes in somatosensory evoked potentials, and incidence of neurologic dysfunction.

To determine if intraoperative monitoring of somatosensory evoked potentials detects spinal cord ischemia, we subjected 21 dogs to aortic cross-clamping distal to the left subclavian artery. Group I animals (short-term studies, n = 6) demonstrated decay and loss of somatosensory evoked potentials at 8.5 +/- 1.1 minutes after aortic cross-clamping. During loss of somatosensory evoked potentials, significant decreases in spinal cord blood flow occurred in cord segments below T6. Significant reactive hyperemia occurred without normalization of somatosensory evoked potentials after reperfusion. Fifteen Group II animals (long-term studies) were studied to determine the relationship between duration of spinal cord ischemia (evoked potential loss) and subsequent incidence of paraplegia. Extension of aortic cross-clamping for 5 minutes after loss of somatosensory evoked potentials in six dogs resulted in no paraplegia (mean cross-clamp time 12.7 +/- 0.6 minutes). Prolongation of aortic cross-clamping for 10 minutes after evoked potential loss in nine dogs (mean cross-clamp time 17.6 +/- 0.6 minutes) resulted in a 67% (6/9) incidence of paraplegia 7 days postoperatively (p = 0.02 versus 10 minutes of aortic cross-clamping). These findings demonstrate that simple aortic cross-clamping uniformly results in spinal cord ischemia and that such ischemia is detectable by monitoring of somatosensory evoked potentials. Duration of ischemia, as measured by the time of evoked potential loss during the cross-clamp interval, is related to the incidence of postoperative neurologic injury.

Animals↗
PubMed1994

Effectiveness of assistance circulations for distal circulatory support during cross-clamping of the descending thoracic aorta.

In order to find the ideal distal circulatory support during cross-clamping of the descending thoracic aorta, the author compared the effects of simple shunting (SS) and centrifugal pump (CP) on hemodynamics and metabolisms in mongrel dogs. In group I (control), the aorta was cross-clamped for two hours without SS or CP; in group II (SS), a temporary shunt was placed between the left common carotid and left femoral arteries during cross-clamping; in group III (CP), with left heart bypass, the flow was maintained about the same as that in group II; in group IV (CP), proximal pressure was maintained unchanged. Hemodynamic and metabolic parameters were recorded prior to cross-clamping and every 30 min for four hours during and after cross-clamping. All animals in group I suffered from hemodynamic instability, metabolic abnormalities and neurologic injury and died within 12 hours. Hemodynamic changes were more unstable in group III than in groups II and IV. Three dogs in group III and also in group IV but none in group II, suffered from neurologic injury. Metabolic changes in groups II, III and IV were not significant. The author conclude that hemodynamic and metabolic abnormalities can be minimized through the efficient use of a shunt in cross-clamping of the descending thoracic aorta and postoperative complications such as paraplegia, renal failure and hepatic dysfunction can be prevented. The centrifugal pump as a distal circulatory support device is able to maintain stable hemodynamics and normal distal organic metabolisms if aortic pressure proximal to the clamp is maintained essentially unchanged through regulation of pump flow. However, it is unable to prevent paraplegia during cross-clamping of the descending thoracic aorta for two hours. Shortening the time of cross-clamping of the descending thoracic aorta is necessary to prevent paraplegia.

Animals↗
PubMed1994

[A new open universal clamp for the external fixator tube system of the AO].

A new open universal clamp has been developed for the external fixator tube system of the ASIF. This new clamp is fully compatible with the previous system. All mechanical properties are at least comparable with those of the hitherto successful clamps, whereas in some cases they are even distinctly superior. The obvious advantages are: The clamp can also be pushed subsequently laterally onto the tubes and arbon fibre rods. The clamping plate for the Schanz screws can take 4-6 mm screws. It is thus possible to use this system alongside with the 4 mm system. The clamp replaces 2 of the previous clamps. An open tube-to-tube clamp can also be positioned. The clamps have been used with success and with full utilisation of all their advantages in their first clinical application.

Biomechanical Phenomena↗
PubMed1993

[Effect of aortic clamping on heart function in elective operation of the abdominal aorta: immediate effects of coronary revascularization].

Infrarenal aortic cross-clamping required during surgical treatment of abdominal aortic aneurysm is generally well tolerated but can be occasionally associated with severe cardiac and haemodynamic disturbances, particularly in patients suffering from coronary artery disease. We compared the haemodynamic changes and the ECG-records before and shortly after infrarenal aortic clamping in three groups of 20 patients (group I: without coronary artery disease, group II: with overt coronary disease without indication for prior myocardial revascularization, and group III: patients undergoing combined procedure: coronary artery bypass immediately prior to aortic repair, during the same anesthesia). There was no significant difference in demographical characteristics between the three groups. Aortic cross-clamping lead to an increase in systemic arterial pressure in all patients. Group I demonstrated a decrease in pulmonary artery pressure, pulmonary capillary wedge pressure and central venous pressure, whereas patients of group II demonstrated an increase of each value when the aorta was clamped. 11 patients of this group developed either arrhythmia and/or ischemia during aortic cross-clamping. Haemodynamic and cardiac effects of aortic clamping seen in patients who had received coronary bypass immediately prior to aortic repair (group III) were surprisingly similar to those of patients without coronary disease, probably owing to systematic application of 2 vasodilators. Tolerance to infrarenal aortic cross-clamping differs in patients with and without coronary artery disease. Development of myocardial ischemia may be predicted by an increase in wedge pressure after clamping. Afterload reduction was the best treatment of ischemia occurring when the aorta was clamped.

Aged↗
PubMed1997

Using atomic force microscopy to investigate patch-clamped nuclear membrane.

Nuclear patch clamp is an emerging research field that aims to disclose the electrical phenomena underlying macromolecular transport across the nuclear envelope (NE), its properties as an ion barrier and its function as an intracellular calcium store. The authors combined the patch clamp technique with atomic force microscopy (AFM) to investigate the structure-function relationship of NE. In principle, patch clamp currents, recorded from the NE can indicate the activity of the nuclear pore complexes (NPCs) and/or of ion channels in the two biomembranes that compose the NE. However, the role of the NPCs is still nuclear because the observed NE current in patch clamp experiments is lower than expected from the known density of the NPCs. Therefore, AFM was applied to link patch clamp currents to structure. The membrane patch was excised from the nuclear envelope and, after electrical evaluation, transferred from the patch pipette to a substrate. We could identify the native nuclear membrane patches with AFM at a lateral and a vertical resolution of 3 nm and 0.1 nm, respectively. It was shown that complete NE together with NPCs can be excised from the nucleus after their functional identification in patch clamp experiments. However, we also show that membranes of the endoplasmic reticulum can contaminate the tip of the patch pipette during nuclear patch clamp experiments. This possibility must be considered carefully in nuclear patch clamp experiments.

Animals↗
PubMed1995

Comparison of the minimal model and the hyperglycemic clamp for measuring insulin sensitivity and acute insulin response to glucose.

Glucose clamp techniques are established methods for assessment of insulin sensitivity and secretion. The minimal model technique (MMT) has been proposed as an alternative approach to the hyperinsulinemic-euglycemic clamp technique for determination of an insulin sensitivity index (ISI), but has not been directly compared with the hyperglycemic clamp for measurement of ISI or insulin secretion. To address this issue, the present study was undertaken to compare determinations of ISI and the acute insulin response to glucose (AIRg) obtained using the MMT with similar measures obtained from a hyperglycemic clamp. Measures for ISI and AIRg obtained from MMT analysis of a tolbutamide-modified frequently sampled intravenous glucose tolerance test (FSIGT) were compared with similar measures obtained from a 3-hour hyperglycemic clamp performed at a plasma glucose level of 10 mmol/L (180 mg/dL). Paired comparisons were performed in 14 women with normal glucose tolerance. Significant positive correlation coefficients were obtained for both ISI (r = .88, P < .001) and AIRg (r = .75, P < .005) between the MMT and clamp studies. We conclude that indices for ISI and AIRg obtained with the MMT are highly correlated with those obtained using the hyperglycemic clamp. The MMT is a valid alternative to the hyperglycemic clamp for assessing insulin sensitivity and AIRg.

Female↗
PubMed2006

Comparison of insulin sensitivity assessment indices with euglycemic-hyperinsulinemic clamp data after a dietary and exercise intervention in older adults.

Multiple indices to assess insulin sensitivity calculated from mathematical equations based on fasting blood parameters or oral glucose tolerance data have been developed. Although these indices have frequently been validated using euglycemic-hyperinsulinemic clamp data, the utility of each equation in measuring change in insulin sensitivity over time remains uncertain. We examined change in insulin sensitivity in response to a 12-week diet and exercise intervention in 31 older men and women with impaired glucose tolerance using a euglycemic-hyperinsulinemic clamp and 10 commonly used insulin sensitivity equations. Mean glucose disposal as calculated from clamp data was significantly higher after the intervention compared with baseline (5.92 +/- 0.38 vs 5.18 +/- 0.30 mg . kg fat free mass(-1) . min(-1), P = .013). In contrast, none of the examined indices indicated a significant change in insulin sensitivity over time (all P > .3). A limits of agreement approach to compare insulin sensitivity calculated from each equation with the measure of glucose disposal from the clamp indicated overall imperfect agreement between measures (agreement limits ranged from +/-2.48 to +/-4.23 mg . kg fat free mass(-1) . min(-1)) despite significant bivariate correlations between indices and clamp data. The wide variability in the 95% prediction limits of agreement among equations suggests that these equations vary substantially from a euglycemic-hyperinsulinemic clamp in their ability to assess insulin sensitivity. Despite the observed limited agreement using this statistical approach, changes in several calculated indices were significantly correlated with changes in clamp data, suggesting that these indices may have some utility in tracking improvements in insulin sensitivity. Further research is necessary to examine agreement between indices and clamp data in larger, more heterogeneous populations and in response to other interventions where the magnitude of change in insulin sensitivity may be larger.

Aged↗
PubMed2003

Correction of conductance measurements in non-space-clamped structures: 1. Voltage-gated K+ channels.

To understand functions of a single neuron, such as propagation and generation of synaptic or action potentials, a detailed description of the kinetics and distribution of the underlying ionic conductances is essential. In voltage-clamp experiments, incomplete space clamp distorts the recorded currents, rendering accurate analysis impossible. Here, we present a simple numerical algorithm that corrects such distortions. The method performs a stepwise approximation of the conductance density at the site of a local voltage clamp. This is achieved by estimating membrane conductances in a simulation that yields simulated clamp currents, which are then fitted to the distorted recordings from the non-space-clamped structure, relying on accurately reconstructed cell morphology and experimentally determined passive properties. The method enabled accurate retrieval of the local densities, kinetics, and density gradients of somatic and dendritic channels. Neither the addition of noise nor variation of passive parameters significantly reduced the performance of the correction algorithm. The correction method was applied to two-electrode voltage-clamp recordings of K(+) currents from the apical dendrite of layer 5 neocortical pyramidal neurons. The generality and robustness of the algorithm make it a useful tool for voltage-clamp analysis of voltage-gated currents in structures of any morphology that is amenable to the voltage-clamp technique.

Algorithms↗
PubMed2002

Improved hybrid clamp: resolution of tail currents following single action potentials.

Hybrid clamp protocols, in which a discontinuous single electrode voltage clamp (dSEVC) amplifier is switched from current to voltage clamp during the recording, are frequently used to investigate conductance changes after high frequency trains of action potentials. This technique is advantageous because it combines physiological stimulation of the cell with the possibility of analyzing the consecutive conductance changes quantitatively. In this study an improved hybrid clamp protocol, called dynamic hybrid clamp, is developed that enables the experimenter to study tail currents after single action potentials. The protocol employs real time action potential detection to assure precise timing of the mode switch and utilizes an external sample and hold amplifier to avoid voltage steps during the switch to voltage clamp. With the use of whole-cell patch clamp recordings and high switching frequencies (> or =25 kHz), dSEVC can easily be started with a minimal delay (<1.5 ms) after single action potentials and tail currents underlying afterhyperpolarisations (AHPs) and afterdepolarisations ensuing single spikes are clearly resolved. The dynamic hybrid clamp should also be useful for analysis of spontaneously occurring events such as intrinsic or population bursts.

Action Potentials↗
PubMed1994

Glucose clamps with the Biostator: a critical reappraisal.

The Biostator makes it possible to perform glucose clamp experiments almost automatically. Thus, blood glucose concentrations can be maintained at (or close to) a target level with substantially less effort than with the manual clamp technique. The automatisation also avoids a potential bias on the part of the investigator. However, as with the non-automated manual clamp technique, blood glucose concentrations do not remain exactly at the target value, as they show a considerable scatter around the target value. This scatter is generated by the time constants of the Biostator, i.e. the whole closed-loop system, and the autoregressive properties of the glucose clamp algorithm used. In order to describe the quality of glucose clamps over time more precisely, "cumulative sums" as an alternative to the usual coefficient of variation can be used. Practical work with the Biostator is burdened with technical difficulties and considerable costs in comparison to the manual clamp technique. Deficits concerning data storage and presentation capability of the Biostator have been overcome by an appropriate programme for an external computer. The use of the Biostator for the glucose clamp technique is not mandatory, but, the use of this machine makes it possible to perform glucose clamp studies under standardised and reproducible conditions.

Algorithms↗
PubMed2004

Relating glucose clamp profiles to reduction of blood glucose after insulin administration.

A model was established allowing prediction of blood glucose response from glucose clamp results performed in healthy volunteers. Data from published studies performed in healthy volunteers were used to establish, test, and validate a model for the evaluation of glucose reductions from glucose clamp results. Studies included those that measured blood glucose and glucodynamic response over time after administration of 0.05 U/kg of regular human insulin (HR) and insulin lispro (LP) with and without the benefit of a glucose clamp procedure. An inhibitory effect E(max) model was used to describe the relationship; the model differed between the HR and LP responses by the intensity of the counterregulatory response as assessed by glucagon measurements. The relationships were used to predict blood glucose responses from a clamp study assessing NPH insulin and HR administrations. Glucose concentrations measured after administration of NPH insulin and HR without a clamp were compared to the model-predicted results to assess the accuracy of the model predictions. The E(max) model successfully correlated the glucose clamp results with the blood glucose depressions in the presence and absence of a counterregulatory response. However, predictions of glucose depression were only accurately modeled in the absence of a counterregulatory glucagon response. The correlations established with a minimal counterregulatory response underscore the value of glucose clamp procedures in defining the time-activity profiles of insulins when the clamp is established at fasting glucose concentrations.

Blood Glucose↗
PubMed1998

Combined hyperinsulinaemic glucose clamp and oral acipimox for optimizing metabolic conditions during 18F-fluorodeoxyglucose gated PET cardiac imaging: comparative results.

To obtain optimal image quality in myocardial viability studies, it is recommended that 18F-fluordeoxyglucose (18F-FDG) studies be performed with hyperinsulinaemic glucose clamping. 18F-FDG imaging after oral administration of acipimox, a nicotinic acid derivative, results in comparable image quality to clamping. Twenty consecutive patients (7 with diabetes mellitus) with angiographically confirmed coronary artery disease and similar demographic/clinical profiles were randomly allocated to gated cardiac 18F-FDG-PET with a standard euglycaemic hyperinsulinaemic clamp protocol or using a combination of oral administration of acipimox and the insulin clamp technique. The image quality, expressed as the myocardial-to-blood pool activity ratio, was superior in the combined protocol compared with the insulin clamping technique alone (3.37 +/- 1.46 vs 2.27 +/- 0.62, P = 0.037). Although there were no significant differences in plasma insulin and free fatty acids concentrations between the two protocols, plasma glucose concentrations obtained with the standard protocol were elevated compared with the combined protocol (11.1 +/- 3.7 vs 6.3 +/- 3.0 mM during clamping; 10.2 +/- 3.3 vs 5.5 +/- 3.0 mM during acquisition). We conclude that gated 18F-FDG-PET imaging after oral administration of acipimox plus insulin clamping yields image quality superior to that obtained with clamping alone.

Administration, Oral↗