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Biomedical subjects

Charles W Buffington

Publications and source records attributed to Charles W Buffington.

7 recordsLinked to original sources
PubMed2006

Human plasma ATP concentration.

BACKGROUND: Human plasma ATP concentration is reported in many studies as roughly 1000 nmol/L. The present study tested the hypothesis that the measured plasma ATP concentration is lower if ATP release from formed blood elements is inhibited during blood sample processing. A second hypothesis was that pretreatment with aspirin to inhibit platelets would reduce the measured plasma concentration of ATP. METHODS: Blood was sampled from the antecubital vein in 20 healthy individuals 30 and 60 min after ingestion of aspirin (325 mg) or placebo. Aliquots of each blood sample were added to the usual EDTA/saline solution to inhibit ATP catabolism, or to a new stabilizing solution designed to both stop ATP catabolism and inhibit ATP release from blood elements. The stabilizing solution contained NaCl, EDTA, tricine buffer, KCl, nitrobenzylthioinosine, forskolin, and isobutylmethylxanthine. Plasma ATP was measured with the luciferin-luciferase assay with standard additions in each sample to determine ATP content. Hemoglobin concentration was used as an index of sample hemolysis, and the plasma ATP concentration was corrected for the hemolysis component. RESULTS: Aspirin pretreatment had no effect on plasma ATP concentrations. However, use of the stabilizing solution resulted in mean (SD) ATP concentrations 8-fold lower than the use of EDTA alone [28 (16) vs 236 (201) nmol/L; P <0.001]. CONCLUSION: When precautions are taken to inhibit ATP release from blood elements during sample preparation, human venous plasma ATP concentration is much lower than previously reported.

1-Methyl-3-isobutylxanthine↗
PubMed2006

High-frequency jet ventilation: utility in posterior left atrial catheter ablation.

BACKGROUND: Percutaneous catheter ablation in the posterior left atrium (LA) is a technically demanding procedure that in our experience is best accomplished using general anesthesia, including endotracheal intubation and mechanical ventilation. However, using conventional intermittent positive-pressure ventilation (IPPV) technique, we were dissatisfied with motion of the posterior LA. This occurred during changes in lung volume, which destabilized ablation electrode-endocardial contact. We hypothesized that use of high-frequency jet ventilation (HFJV), a low-volume, fast-rate technique, would reduce posterior LA motion and thus facilitate the ablation procedure. OBJECTIVES: The purpose of this study was to demonstrate that, relative to IPPV, HFJV reduces posterior LA motion and facilitates catheter ablation in this region. METHODS: Patients who underwent posterior LA ablation using HFJV (n = 36) were retrospectively compared with those in whom IPPV (n = 36) was used. Indices examined included number of radiofrequency energy applications, electrode temperature, and procedure time. A prospective direct comparison of the impact of HFJV and IPPV on LA volume and mechanical function was performed in an additional 10 patients. RESULTS: Fewer ablation lesions were required in the HFJV group because of fewer incidences of ablation electrode dislodgment, resulting in significantly decreased procedure time. Although there was no significant difference in maximal electrode temperature achieved during radiofrequency application, temperature variation was diminished in the HFJV group. Direct comparison demonstrated that HFJV produced less variation in LA volume, pressure, pulmonary vein blood flow velocity, and posterior LA position than IPPV. CONCLUSION: Relative to IPPV, HFJV yields a more stable posterior LA environment, thus facilitating catheter ablation. Use of HFJV may be applicable to other interventional cardiovascular procedures.

Blood Flow Velocity↗
PubMed2006

Body position affects manual dexterity.

To evaluate the relationship between posture and psychomotor efficiency, 20 anesthesia providers performed a test requiring manual dexterity and eye-hand coordination while seated, kneeling, and standing bent forward at the waist. Performance on the Grooved Pegboard Test improved 6%-10% (P < 0.005) when subjects were seated compared to kneeling and standing bent at the waist, positions that the subjects rated as more painful and less comfortable than sitting. Sitting improved manual dexterity more in subjects with poor scores than it did in subjects with good performance. This study demonstrates improved manual dexterity in subjects seated in a comfortable position.

Adult↗
PubMed2004

Neither the accuracy nor the precision of thermal dilution cardiac output measurements is altered by acute tricuspid regurgitation in pigs.

UNLABELLED: Whether measurement of cardiac output using the thermal dilution technique (TDCO) is valid in the presence of tricuspid regurgitation (TR) is controversial. We assessed the accuracy and precision of the technique in pigs by comparison with data from an electromagnetic flowmeter on the aorta (EMCO). TR was created with sutures that immobilized the free-wall leaflets of the tricuspid valve, and cardiac output was adjusted with dobutamine to give values comparable to control measurements. TR reduced forward stroke volume from 17.2 to 12.6 mL/beat and caused the right atrium to dilate and pulse in synchrony with the right ventricle. Acute TR did not affect the linear regression relation between TDCO and EMCO and did not alter the correlation coefficient (r = 0.94 during both control and TR). These data demonstrate that acute TR does not affect the accuracy or precision of TDCO in pigs. IMPLICATIONS: Cardiac output is a valuable measurement that guides the medical care of patients with heart and lung disease. This study demonstrates that the thermal dilution technique of determining cardiac output is valid when acute tricuspid valve regurgitation is present in pigs.

Anesthesia, Inhalation↗
PubMed2004

Brand and size matter when choosing a syringe to relieve pressure in a tracheal tube cuff.

We studied the use of an inline syringe as a pressure relief valve for tracheal tube cuffs during exposure to nitrous oxide to see if the technique works. Bench testing was done to determine the stick and slip characteristics of syringes of different brands and sizes. Cuffs were inflated with 20 mL of air, producing a cuff pressure of 100-120 mm Hg. Then the plunger of the syringe was allowed to passively rebound to a steady pressure at which the plunger stopped ("stick pressure"). After several minutes, pressure in the syringe was forcibly increased with a second syringe until the plunger started moving again ("slip pressure"). Stick pressure varied from 18 to 82 mm Hg depending on the brand and size of syringe used. Slip pressures exceeded stick pressures by 20-120 mm Hg. Cuff pressure increased in a linear fashion during nitrous oxide exposure, and no syringe demonstrated automatic pressure reduction. We conclude that a syringe attached to the pilot balloon connector can be used to control tracheal tube cuff pressure during nitrous oxide anesthesia. However, not all syringes are suitable for this purpose: large syringes are better than small syringes, and the Terumo brand is more suitable than BD or Monoject. The system does not work automatically, and intermittent compression of the syringe plunger to overcome static friction is required to avoid overdistension.

Elasticity↗
PubMedDate not supplied

Hydrodynamics of the spinal epidural space in pigs determined by constant-flow methods.

BACKGROUND AND OBJECTIVES: Impressive quantities of fluid can be infused into the epidural space of the spine without causing dramatic or sustained increases in pressure. The epidural space is considered "leaky," but questions remain about how fluid leaves the epidural space. We used constant-flow infusions of saline to gain insight into the hydrodynamics involved. METHODS: We infused saline at a constant rate into the lumbar epidural space of 6 anesthetized pigs while measuring pressure at the adjacent interspace. Three or 4 infusions were performed at different flow rates in each animal. RESULTS: Epidural space pressure in the absence of flow was consistently 2 to 3 mm Hg above right atrial pressure. During each infusion, pressure increased slowly to a steady plateau value between 15 and 70 mm Hg. When flow was stopped, pressure declined exponentially to the starting pressure. The presence of a plateau indicates that fluid leaving the epidural space ends up in a structure with high capacitance. Plateau pressures were linearly related to flow rate in each animal, indicating constant resistance to outflow. The flow-pressure relation showed neither a critical opening pressure nor moderating pressures with increased flow. CONCLUSIONS: Fluid leaves the porcine spinal epidural space through channels that are open at baseline rather than being recruited as epidural pressure increases. This behavior is inconsistent with the view that the epidural space behaves like a Starling resistor.

Animals↗