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Biomedical subjects

D R Bacon

Publications and source records attributed to D R Bacon.

At least 19 recordsLinked to original sources
PubMed2000

Acute abdominal compartment syndrome with pulseless electrical activity during colonoscopy with conscious sedation.

We report an episode of acute abdominal compartment syndrome, with pulseless electrical activity, in a patient undergoing colonoscopic examination of a recently constructed mucus fistula. Associated clinical features of this acute abdominal compartment syndrome (tension pneumoperitoneum) were abdominal distention, which was very impressive, cardiopulmonary arrest, severe cyanosis, and progressive bradycardia.In general, increased intraabdominal pressure can have numerous adverse physiologic effects, which may include decreased cardiac output, altered ventilation-perfusion relationships, and decreased venous return. The magnitude of each effect likely depends on the magnitude of the increased intraabdominal pressure. Success with initial resuscitation efforts should not diminish further vigilance with these patients, as other problems may be discovered.

Abdomen↗
PubMed1999

The influence of ocular pulsatility on scanning laser Doppler flowmetry.

PURPOSE: To determine the effect of the cardiac cycle on scanning laser Doppler flowmeter measurements of retinal capillary blood flow in rhesus monkeys and humans. METHODS: Multiple scanning laser Doppler flowmetry images of rhesus monkey and human retinal capillary blood flow over a range of heart rates were obtained. Average flow values were determined for the 64 scan lines that compose the two-dimensional flow map. Cutaneous blood flow was measured simultaneously with a laser Doppler flowmeter. The temporal relationships between retinal capillary blood flow, peripheral arterial pulse, and cutaneous blood flow were determined. In addition, human retinal capillary blood flow in a 10 x 10-pixel area during different phases of the cardiac cycle was compared. RESULTS: Regular oscillations in human and rhesus monkey retinal capillary blood flow are evident as alternating bright and dark horizontal bands in scanning laser Doppler flowmetry images. These fluctuations are temporally correlated with cutaneous blood flow. Linear regression of actual vs predicted heart rate based on peaks in retinal capillary flow yielded r = 0.999 in a rhesus monkey and 0.938 in a human. Retinal capillary blood flow in a 10 x 10-pixel area fluctuated as much as 50% depending on the phase of the cardiac cycle. CONCLUSIONS: The alternating bright and dark banding pattern observed in scanning laser Doppler flowmetry scans of retinal capillary blood flow is related to the cardiac pulse. The errors introduced by pulse-related fluctuations in retinal capillary blood flow are significant and must be minimized or corrected for accurate and reproducible measurements of ocular hemodynamics.

Animals↗
PubMed1999

Blood product use in cardiac revascularization: comparison of on- and off-pump techniques.

BACKGROUND: Cardiac revascularization on a beating heart avoids the side effects of cardiopulmonary bypass (eg, neurologic injury, hemodilution, and coagulopathy). We examined perioperative bleeding and use of blood products during coronary artery bypass grafting using either on-pump or off-pump techniques. METHOD: The charts of 126 patients who had coronary artery bypass grafting were reviewed. Data from 66 patients revascularized off pump and 60 patients with cardiopulmonary bypass (on pump) were analyzed using unpaired Student's t test. RESULTS: Average age was 62.5 years in either group. More patients received heparin preoperatively in the off-pump group that resulted in mild elevation of preoperative partial thromboplastin time and activated clotting time (40.4 +/- 2.9 seconds and 150.1 +/- 5.3 seconds, respectively). However, the off-pump group had less perioperative (intraoperative or postoperative) bleeding (2312 +/- 212 mL versus 3251 +/- 155 mL, p < 0.05) and required fewer blood products compared with the on-pump group. Hemoglobin and platelets decreased more in the conventional on-pump group. CONCLUSIONS: Avoiding cardiopulmonary bypass decreases perioperative bleeding and, consequently, reduces the use of blood products after coronary artery bypass grafting, which might result in fewer transfusion-related complications.

Adult↗
PubMed1999

The development and testing of the patient record pain management assessment tool.

The article reports a study whose purpose was to develop and test the Patient Record Pain Management Assessment Tool, an instrument to evaluate compliance with the American Pain Society's quality assurance standards on acute pain and cancer pain in chart documentation. Content validity, overall validity, and interrater reliability were all found to be acceptable. The instrument is therefore a useful tool for documenting the level of pain management practice in institutional settings.

Forms and Records Control↗
PubMed1996

Sources of variability of topometric data with a scanning laser ophthalmoscope.

OBJECTIVE: To determine in a two-part study whether misalignment between the patient and the laser scanner is a major source of variability with the Heidelberg Retina Tomograph (Heidelberg [Germany] Engineering). METHODS: Three topographic images of the right optic nerve were acquired with the Heidelberg Retina Tomograph in eight patients with glaucoma. The correlations between average cup volume, variability of cup volume estimates, and direction of imaging were evaluated. Furthermore, the correlations between average rim volume, variability of rim volume estimates, and direction of imaging were evaluated. Next, the optic nerve cup volume and rim volume estimates of a rabbit's left eye were compared between three series of five topographic images acquired from three slightly different directions. RESULTS: Average cup volume, variability of cup volume estimates, and variability in the direction of imaging correlated significantly among the patients with glaucoma (multiple R2 = .95; P < .001). Average rim volume, variability of rim volume estimates, variability in the direction of imaging, and variability in the mean height of the contour line also correlated significantly (multiple R2 = .88; P = .03). In the rabbit eye, the cup volume and the rim volume differed significantly among the three image series (analysis of variance, P < .001 and P = .04, respectively). CONCLUSION: Misalignment between the patient and the laser scanner may account for significant variability with the Heidelberg Retina Tomograph.

Animals↗
PubMed1996

Measurement of optic nerve blood flow with nonradioactive colored microspheres in rabbits.

The objective of this study was to establish a nonradioactive technique to accurately assess blood flow in a small tissue such as the anterior optic nerve. Colored microspheres, 10.2 +/- 0.23 microns in diameter, were injected into the left atrium in each of 17 anesthetized rabbits. The rabbits were divided into four groups injected, respectively, with 5, 10, 50, or 100 million microspheres. Microsphere quantification in the tissue was performed after postmortem dissection and alkaline corrosion of the anterior optic nerve. Blood flow was evaluated by means of reference sample comparison method. While the relative interocular difference (range, 15.3-162.8%) was not significantly different between the rabbits injected with 5, 10, or 50 million microspheres (Kruskal-Wallis test, P = 0.11), injection with 100 million microspheres yielded a significantly lower relative interocular differences (range 2.3-12.8%) compared to the other three groups (Kruskal-Wallis test, P = 0.0048). In addition, reproducibility of microsphere counts was evaluated by ranking the difference between right and left optic nerve in percentage of the average number of microspheres per milligram of tissue in both optic nerves. The correlation between the relative interocular difference (range, 2.3-162.8%) and the average number of microspheres per milligram of tissue (1.2-78.7 microspheres/mg optic nerve tissue) was statistically significant (Spearman R, -0.90; P < 0.0001). The interocular variability in microsphere counts and interocular difference in intraocular pressure did not correlate (Spearman R, 0.33; P = 0.20). The rabbits injected with 100 million microspheres showed the highest average number of microspheres (range, 31.8-78.7 microspheres/mg optic nerve tissue). The optic nerve blood flow ranged between 0.14 and 0.24 microliters/mg/min among the rabbits injected with 100 million microspheres. The present experimental technique of optic nerve blood flow measurement is relatively inexpensive, highly reproducible, and obviates disposal of radioactive materials.

Animals↗
PubMed1996

Perfusion corrections for ultrasonic heating in nonperfused media.

The linear bio-heat transfer equation proposed by Pennes is widely used to predict temperature rise in perfused media. In this article, a mathematical relationship between the predicted temperature increase under perfused and nonperfused conditions is derived based on an analysis of the Pennes equation. The perfused temperature at time t and position r, Tperf(r,t) can be calculated from the unperfused temperature history Tunperf(r,t) and the time constant for perfusion, tau: [formula: see text] When the full nonperfused temperature history is not available, a simpler approximate method of estimating the perfused temperature is also suggested, requiring only a knowledge of the time constant for perfusion. Results are given showing the effects of perfusion after different exposure times for a range of beamwidths and perfusion time constants.

Algorithms↗
PubMed1996

The copper kettle: a historical perspective.

Until 1952, the administration of inhaled volatile anesthetics was inexact because vaporizers in general use were not calibrated for either concentration or volume of vapor produced. These devices diverted a variable portion of fresh gas flow either through or over the liquid to be vaporized, but they lacked vernier or fine control. Therefore, changes in the concentration of the anesthetic vapor were not easily controlled. Dr. Lucien E. Morris standardized the administration of volatile anesthetics with his invention of the Copper Kettle, which produced known volumes of saturated vapor, then diluted to calculated concentrations necessary for anesthesia. To achieve this, modifications had to be made in the liquid container, circuit design, and vaporizing surfaces in use at the time. Morris' design incorporated a separately metered flow of carrier gas through the vaporizer to produce known volumes of saturated vapor for introduction into the fresh gas flow delivery.

Anesthesiology↗
PubMed1996

A curious moment: the proposal to certify nurse anesthetists by the American Board of Anesthesiology.

During the 1930s, many different practitioners gave anesthetics to patients. Qualifications were not necessary, and economics often drove the choice of anesthetic administrator. Both physicians and nurse specialists in anesthesia understood the need for specialty certification. For individual physicians, the American Board of Anesthesiology (ABA) was created as a sub-board of the American Board of Surgery (ABS) with the sanction of the American Medical Association and the American Society of Anesthetists. The nurse anesthetists worked toward program rather than individual certification. For one curious moment, the ABS asked the ABA to certify nurse anesthetists. Neither the nurses nor the physician anesthetists were overwhelmingly in favor of the proposal. However, had the proposal succeeded, the face of American anesthesiology would have been quite different.

Anesthesiology↗