The effect of tidal volume and intravascular volume state on systolic pressure variation in ventilated dogs

Both tidal volume and effective blood volume may affect the variation in the arterial pressure waveform during mechanical ventilation. The systolic pressure variation (SPV), which is the difference between the maximal and minimal systolic pressure values following one positive pressure breath was analyzed in 10 anesthetized and ventilated dogs, during ventilation with tidal volumes of 15 and 25 ml/kg. The dogs were studied during normovolemia, hypovolemia (after bleeding of 30% of estimated blood volume) and hypervolemia (after retransfusion of shed blood with additional 50 ml/kg of plasma expander). The SPV reflected hemodynamic changes and was maximal during hypovolemia and minimal during hypervolemia. Unlike all other hemodynamic parameters it was also affected by the tidal volume and significantly increased at higher tidal volumes during each volume state. We conclude that the SPV and its components are useful parameters in evaluating the intravascular volume state. They also reflect the magnitude of the tidal volume employed.Supported by the Ministry of Industry — Hadassah Foundation for Applied Research, and partly by the MJF foundation     

End-of-life intensive care unit decisions,communication, and documentation: an evaluation of physician training

PURPOSE: The majority of patients dying in intensive care units (ICUs) do so after the forgoing of life-sustaining therapies (FLST). Communication between physicians, patients, and their families regarding the decision to FLST has not been evaluated in Israel. MATERIALS AND METHODS: All patients who had FLST in a general ICU were enrolled in the study. We evaluated whether physicians communicated and documented the FLST decisions with patients or the patients' families. We also assessed the effect of the physician's geographic place of training on communication behavior. RESULTS: Over a period of 8.5 months, 385 patients were admitted to a general ICU in Israel. Fifty-seven patients died or had FLST. Twelve of these 57 were excluded from the study. Thus, 45 (79%) patients had FLST and were enrolled in the study. All patients were deemed medically incompetent to make FLST decisions. In 24 (53%) patients, FLST was discussed with the family before the decision to forgo therapy. Discussion occurred later with 6 other families, who were unavailable at the time the FLST decision was made. In 15 patients, there were no discussions with families. American-trained physicians discussed FLST with 22 of 29 families initially and 5 other families later (93%), whereas the Eastern European-trained physicians discussed FLST with only 3 of 16 (19%) families (P <.001). Documentation of FLST was present in 26 (90%) patients of American-trained physicians and 8 (50%) patients of Eastern European-trained physicians (P <.001). CONCLUSIONS: FLST is common in an Israeli ICU. Patients are not medically competent to make FLST decisions. American-trained physicians discuss and document FLST more often than Eastern European-trained physicians.     

From a radial operating theatre to a self-contained operating table

Equipment congestion and a disarray of wires, tubes and lines (the spaghetti syndrome) is a common scenario in operating theatres. The radial arrangement of input and output signals and their interconnecting lines has been identified as the main source of clutter and congestion in this environment. Our aim was to present a comprehensive design concept for reducing electrical and physical clutter in the operating theatre. Data were collected from different operating theatres, including identification and sorting of equipment, cables, tubes and lines according to the direction and the features of the transmitted information and materials. We suggest a concept of a self-contained, 'built-in' operating table as a design solution for avoiding the clutter and congestion caused by the radial configuration. The operating table will function as a central integrated unit for management of the entire process of patient flow and control of supply systems and environmental conditions.     

Systolic pressure variation is greater during hemorrhage than during sodium nitroprusside-induced hypotension in ventilated dogs

The systolic pressure variation (SPV), which is the difference between the maximal and minimal values of the systolic blood pressure (SBP) after one positive-pressure breath, was studied in ventilated dogs subjected to hypotension. Mean arterial pressure was decreased to 50 mm Hg for 30 minutes either by hemorrhage (HEM, n = 7) or by continuous infusion of sodium nitroprusside (SNP, n = 7). During HEM-induced hypotension the cardiac output was significantly lower and systemic vascular resistance higher compared with that in the SNP group. The systemic, central venous, pulmonary capillary wedge pressures, and heart rates, were similar in the two groups. Analysis of the respiratory changes in the arterial pressure waveform enabled differentiation between the two groups. The SPV during hypotension was 15.7 +/- 6.7 mm Hg in the HEM group, compared with 9.1 +/- 2.0 mm Hg in the SNP group (P less than 0.02). The delta down, which is the measure of decrease of SBP after a mechanical breath, was 20.3 +/- 8.4 and 10.1 +/- 3.8 mm Hg in the HEM and SNP groups, respectively, during hypotension (P less than 0.02). It is concluded that increases in the SPV and the delta down are characteristic of a hypotensive state due to a predominant decrease in preload. They are thus more important during absolute hypovolemia than during deliberate hypotension.     

Systolic blood pressure variation is a sensitive indicator of hypovolemia in ventilated dogs subjected to graded hemorrhage

Systolic pressure variation (SPV) is defined as the difference between the maximum and minimum values of systolic blood pressure following a single positive pressure breath. An increase in the SPV is known to occur clinically during hypovolemia. This study aims to quantify SPV during graded hemorrhage in ventilated dogs, and to compare its reliability relative to other hemodynamic indicators of hypovolemia. Ten anesthetized dogs were mechanically ventilated with a fixed tidal volume. A continuously inflated vest was applied around the chest to maintain the ratio of lung to chest wall compliance similar to that of humans (0.83 +/- 0.12). SPV was further divided into delta up and delta down components relative to apneic (5 s) systolic blood pressure. Dogs were bled 5, 10, 20, and 30% of their estimated blood volume. The measured parameters best correlated to the amount of bleeding were SPV (rs = 0.993), delta down (rs = 0.981), and cardiac output (rs = 0.976). The SPV and its delta down component correlated to the degree of hemorrhage as well as the CO and the pulmonary capillary wedge pressure, and significantly better than the central venous pressure and the mean systemic blood pressure. Thus, SPV and its delta down component are accurate indicators of hypovolemia in ventilated dogs subjected to hemorrhage.     

Nesidiodysplasia--a histologic entity?

Five cases of persistent neonatal hyperinsulinemic hypoglycemia (PNHH) were studied by a combined immunofluorescent and Feulgen technique under a computerized microscope which was used to measure the area and absorbance of beta cell nuclei. An increase of 16% was found in the nuclear area and absorbance of the beta cells in PNHH cases, in comparison with age-matched control cases. A smaller increase (9%) was found in nuclear area and absorbance of non-endocrine ductal cells in PNHH cases. In all PNHH and control cases, higher values of nuclear area and absorbance were found for beta cells in the islets of Langerhans than for nesidioblasts. The increase in average size of beta cell nuclei in PNHH can be used as a morphologic criterion for diagnosis in these cases. The increased absorbance of the nuclei stained with the Feulgen reaction is the morphologic expression of polyploidy, and has a correlation to the metabolic activity of beta cells in this disorder. We conclude that, in contrast to the normal postnatal developmental process of nesidioblastosis, nesidiodysplasia is a well-defined histologic entity, manifested by an increase of beta cell nuclear size and its DNA content.