Distribution of pleural injectate. Effect of volume of injectate and animal rotation.

It is controversial whether rotation is necessary for patients undergoing pleurodesis. In addition, the optimal volume of the injectate remains to be determined. The purpose of this study was to determine the importance of rotation and the volume of the agent on the intrapleural dispersion of agents injected into the pleural space of rabbits. Technetium 99m pertechnetate (99mTc) in 0.5, 1.0, or 2.0 ml of saline solution was injected into ten lightly anesthetized rabbits, half of whom were rotated for 1 min after the injection. Static images were obtained in the anterior projection 1 and 5 min after the injection. After the second scan, the limits of the lung were defined by obtaining a perfusion scan immediately after the intravenous injection of macroaggregates of 99mTc-labeled serum albumin. The degree of dispersion was significantly greater in the nonrotated groups both at 1 min (F = 8.11, p = 0.0085) and at 5 min (F = 5.89, p = 0.0274). In addition, the homogeneity of the distribution of the injectate was not improved with rotation. From this study, we conclude that rotation of the animal for 1 min after the intrapleural injection does not improve the distribution of the injectate throughout the pleural space. Furthermore, a volume of 0.5 ml is sufficient for all pleural surfaces to be exposed.

A quantitative analysis of transcapillary refill in severe hemorrhagic hypotension in dogs.

In pressure-driven hemorrhage (PDH), where the rate of bleeding is a function of prevailing arterial pressure, survival time, arterial pressure, cardiac output, oxygen consumption, and base excess are functions of initial bleeding rate. The quantitative rate of transcapillary refill (TR) throughout PDH leading to death was determined in splenectomized dogs, through serial analysis of Cr51-tagged red cell dilution. Mild, moderate, and severe levels of PDH were produced by varying initial bleeding rate (10, 25, and 50 ml/min, respectively). The rate of TR is a function of the severity of PDH, but does not correlate with arterial pressure, cardiac output, or systemic resistance. The volume of transferred fluid represents an ever increasing fraction of total plasma volume, and accounts for more than 75% of plasma volume in preterminal stages of shock. TR sustains a relatively fixed level of plasma volume, equivalent to two-third of the initial plasma volume, irrespective of the rate of bleeding. Hypertonic NaCl (7.5%) enhances TR, while isotonic NaCl reverses it.

Isochloremic hypertonic solutions for severe hemorrhage.

Two different hypertonic (2400 mOsm/L) isochloremic dextran solutions (sodium acetate, HAD; and sodium lactate, HLD; in 0.9% NaCl + 6% dextran 70) were compared with HSD (2400 mOsm/L NaCl + 6% dextran 70) as initial treatment for severe uninterrupted arterial bleeding. The substitution of dextran 70 for lactated Ringer's solution as the maintenance isotonic infusion fluid was also analyzed. Experiments were performed in pentobarbital-anesthetized dogs. A recently developed model, pressure-driven hemorrhage (PDH), which mimics uninterrupted arterial bleeding, was employed. It was found that (1) the substitution of dextran 70 for lactated Ringer's as isotonic fluid makes no difference in hemodynamic terms; (2) isochloremic hypertonic solutions are similar in their hemodynamic resuscitative effect, representing an improvement over hypertonic NaCl in terms of cardiac output, O2 delivery and O2 consumption; (3) HAD proved superior to HLD in terms of O2 consumption and correction of pH/base excess.

Physical and physiological characteristics of pressure-driven hemorrhage.

Research on hemorrhage has concentrated on its effects rather than the manner of occurrence. A new experimental method in which the rate of bleeding is a function of prevailing arterial pressure is proposed and described. The effects of standard crystalloid volume expansion and of small volume hypertonic treatment on this protocol are demonstrated. In pressure-driven hemorrhage, survival time and the decay of arterial pressure, cardiac output, oxygen consumption, and base excess are functions of the bleeding rate, but plasma proteins and hematocrits are independent. The decay of arterial pressure is also a complex function of blood volume deficit, but this relation is not dependent on the rate of blood removal. Volume expansion induces a recovery of circulatory function despite enhanced blood loss. A comparison between equiosmolar solutions of hypertonic sodium chloride and acetate shows that acetate produces a smaller pressor (hence less blood loss) but larger blood flow (hence higher O2 availability) effect. The possible importance of the isochloremic nature of the response to acetate is highlighted.

Thermographic study of laser on arteries.

We analyzed the different effects of CO2, Nd-YAG, and argon lasers on aorta by using a Thermovision infrared system that registered the laser interaction with mongrel dog aorta. The images (thermograms) obtained were processed by a computer, which associated each area of the same temperature with a determined color. These thermograms were compared to histological analysis of the respective samples and the following results were obtained: (1) After the application of each laser there is very little propagation of heat in tissue. (2) The CO2 laser makes tissue reach 100 degrees C in less than 0.05 seconds. (3) The heat dissipation time was higher with the Nd-YAG laser due to higher scattering on tissue. Based on this research we conclude that the CO2 laser was best absorbed, the Nd-YAG laser penetrated human tissue with the best results, and the argon laser had the most significant backscattering.