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INTRODUCTION: An ideal ligature should tighten readily and remain tight. Ligature failure can be a critical complication of invasive procedures in human and veterinary surgical practice. Previous studies have tested various knots but not the constrictor knot. METHODS: A new test bench was employed to compare six ligatures using four suture materials. As tension in a ligature is not readily measured, the study employed a surrogate measurement: the force required to slide a ligature along a rod. Benchmark values tested each suture material wrapped around the rod to establish the ratio between this force and the ligature tension for each material. Each ligature was tested first during tightening and then again afterwards. The benchmark ratios were employed to calculate the tensions to evaluate which ligature and which suture material retained tension best. RESULTS: The model provided consistent linear relationships between the tension in the suture and the force required to pull the ligature along the rod. The constrictor knot retained tension in the ligature best (55-107% better than the next best ligature). Among the suture materials, polydioxanone had the greatest ability to retain the tension in a ligature and polyglactin the least. CONCLUSIONS: The constrictor knot showed superior characteristics for use as a ligature, and should be introduced into teaching and clinical practice for human and veterinary surgery. The new test bench is recommended for future testing of ligatures as well as objective comparison of suture materials.

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OBJECTIVES: Renal and respiratory acid-base regulation systems interact with each other, one compensating (partially) for a primary defect of the other. Most investigators striving to typify compensations for abnormal acid-base balance have reported their findings in terms of arterial pH, PaCO2, and/or HCO3-. However, pH and HCO3- are both altered by both respiratory and metabolic changes. We sought to simplify these relations by expressing them in terms of standard base excess (SBE in mM), which quantifies the metabolic balance and is independent of PaCO2. DESIGN: Meta-analysis. SETTING: Historical synthesis developed via the Internet. PATIENTS: Arterial pH, PaCO2, and/or HCO3- data sets were obtained from 21 published reports of patients considered to have purely acute or chronic metabolic or respiratory acid-base problems. INTERVENTIONS: We used the same data to compute the typical compensatory responses to imbalances of SBE and PaCO2. Relations were expressed as difference (delta) from normal values for PaCO2 (40 torr [5.3 kPa]) and SBE (0 mM). MEASUREMENTS AND MAIN RESULTS: The data of patient compensatory changes conformed to the following equations, as well as to the traditional PaCO2 vs. HCO3- or H+ vs. PaCO2 equations: Metabolic change responding to change in PaCO2: Acute deltaSBE = 0 x deltaPaCO2, hence: SBE = 0, Chronic deltaSBE = 0.4 x deltaPaCO2. Respiratory change responding to change in SBE: Acidosis deltaPaCO2 = 1.0 x deltaSBE, Alkalosis deltaPaCO2 = 0.6 x deltaSBE. CONCLUSION: Data reported by many investigators over the past 35 yrs on typical, expected, or "normal" human compensation for acid-base imbalance may be expressed in terms of the independent variables: PaCO2 (respiratory) and SBE (metabolic).

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The development of informative design principles is necessary to permit logical, informative and understandable computer-aided imaging of the flood of measured parameters the practising anesthesiologist is currently confronted with. The computer-assisted workplace, furthermore, can use the computer to close the loop from sensor to therapy through software directed feed back control mechanisms. The general principles of information design should be based on the rule of three derived from the limited visual integration capacity of the human brain. Thus multiple parameters should be logically grouped in blocks of three strictly distinct from each other in the visual display output. Alarm signalisations have to include two senses: visual and audible and should use the large range of variability that is possible to make them distinct from each other. The operational keyboard should be logically designed with grouping in three parts: 1. a group of buttons for activation of operational screen information that appear with never more than three at the same time; 2. buttons for presetting of wanted parameter values, of alarm limits and for introduction of patient data with adjoint but strictly separated OK-mode necessity to alert that change is being made. 3. a row of buttons separated from the normal operational keyboard area for emergency changes and computer feed back mode bypass, for example. The most illogical, unoverseeable and confusing computeraided workplace can be organized to a fully assisting anesthesia workplace if proper design is applied. The use of a users' manual should be rendered unnecessary even to a computer-naive user. This can be achieved through adequate informative design and operational information flow.(ABSTRACT TRUNCATED AT 250 WORDS)

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The Renal Transplant Team at Tulane University Medical Center has been involved in training a multispecialty group of Guatemalan physicians to perform renal transplantations in Guatemala. The purpose is to train the physicians in their own country, using available equipment and personnel so that they can perform successful operations in our absence. This paper is a review of the considerations involved in the initial renal transplantation done in Guatemala by the Tulane Renal Transplant Team. The need for a preliminary site visit was paramount. Personnel, facilities, and both surgical and anesthesia equipment and supplies were carefully evaluated. The recipient was a 22-year-old man with end-stage renal disease due to chronic glomerulonephritis. The donor was a healthy 33-year-old brother. This article is not intended to review renal transplantation in the United States, but to show what is feasible in a developing country where many drugs and equipment are not available.

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Gastric fluid pH and volume were studied on induction of anesthesia, during maintenance and at the end of the anesthesia in 50 elective surgical patients. All the patients were premedicated with meperidine, 1 mg/kg, and atropine 0.006 mg/kg, administered intramuscularly 45 minutes before induction of anesthesia. Half of the patients had incremental doses of meperidine; the other half had enflurane 1% to 2%; all had 70% nitrous oxide in oxygen during anesthesia maintenance. The incidence of a gastric fluid pH below 2.5 was 68% at the time of induction of anesthesia, 30% after 1 hour anesthesia, and 60% at the end of anesthesia. The incidence of a combination of pH below 2.5 and a volume above 25 ml was 30% on induction and 50% at the end of the anesthetic. There was no difference between the results in the two groups. It was concluded that although there was a decrease of gastric acidity during the anesthetic, the incidence of risk factors for aspiration pneumonitis at the end of the operation is at least as great as that on induction. Emptying the stomach before extubation may decrease this risk.

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