No abstract

Isoflurane, but not mechanical ventilation, decreased urinary excretion and increased interstitial fluid volume. Volume kinetic analysis indicated "third-space" losses due to isoflurane. Perioperative fluid retention may be associated not only with surgical tissue manipulation, but with anesthesia per se.

Hypotensive resuscitation has been advocated as a better means to perform field resuscitation of penetrating trauma. Our hypothesis is that hypotensive resuscitation using either crystalloid or colloid provides equivalent or improved metabolic function while reducing the overall fluid requirement for resuscitation of hemorrhage. We compared hypotensive and normotensive resuscitation of hemorrhage using lactated Ringer's (LR) with hypotensive resuscitation using Hextend (Hex), 6% hetastarch in isotonic buffered saline. Instrumented conscious sheep were hemorrhaged in three separate bleeds, 25 mL/kg at T0 and 5 mL/kg at both T50 and T70. Resuscitation was started at T30 and continued until T180. Hypotensive resuscitation to a mean arterial pressure (MAP) of 65 mmHg was performed with LR or Hex using a closed-loop resuscitation (CLR) system for a LR-65 and Hex-65 treatment protocol. A control treatment protocol was resuscitation with LR to a MAP target of 90 mmHg, LR-90. All treatment protocols were successfully resuscitated to near target levels. Two animals in the hypotensive treatment protocols died during the second and third bleedings, one in the LR-65 and one in the Hex-65 treatment protocol. Mean infused volumes were 61.4 +/- 11.3, 18.0 +/- 5.9, and 11.6 +/- 1.9 mL/kg in the LR-90, LR-65, and Hex-65 treatments, respectively (*P < 0.05 versus LR-90). Mean minimum base excess (BE) values were +1.9 +/- 1.4, -5.8 +/- 4.3, and -5.9 +/- 4.0 mEq/L in the LR-90, LR-65, and Hex-65 treatments, respectively. Hypotensive resuscitation with LR greatly reduced volume requirements as compared with normotensive resuscitation, and Hex achieved additional volume sparing. However, trends toward lower BE values and the occurrence of deaths only in the hypotensive treatment protocols suggest that resuscitation to a target MAP of 65 mmHg may be too low for optimal outcomes.

Purpose To study the feasibility of a myocardial infarct (MI) quantification method (Signal Intensity-based Percent Infarct Mapping, SI-PIM) that is able to evaluate not only the size, but also the density distribution of the MI. Methods In 14 male swine, MI was generated by 90 minutes of closed-chest balloon occlusion followed by reperfusion. Seven (n=7) or 56 (n=7) days after reperfusion, Gd-DTPA-bolus and continuous-infusion enhanced Late Gadolinium Enhancement (LGE) MRI, and R1-mapping were carried out and post mortem triphenyl-tetrazolium-chloride (TTC) staining was performed. MI was quantified using binary (2 or 5 standard deviations, SD), SI-PIM and R1-PIM methods. Infarct Fraction (IF), and Infarct-Involved Voxel Fraction (IIVF) were determined by each MRI method. Bias of each method was compared to the TTC technique. Results The accuracy of MI quantification did not depend on the method of contrast administration or the age of the MI. IFs obtained by either of the two PIM methods were statistically not different from the IFs derived from the TTC measurements at either MI age. IFs obtained from the binary 2SD method overestimated IF obtained from TTC. IIVF among the three different PIM methods did not vary, but with the binary methods the IIVF gradually decreased with increasing the threshold limit. Conclusions The advantage of SI-PIM over the conventional binary method is the ability to represent not only IF but also the density distribution of the MI. Since the SI-PIM methods are based on a single LGE acquisition, the bolus-data-based SI-PIM method can effortlessly be incorporated into the clinical image post-processing procedure.

Isoflurane-anesthetized sheep were transfused with packed red blood cells (pRBCs) or diaspirin cross-linked hemoglobin (DCLHb) for treatment of intraoperative hemorrhage. A rapid 15-min hemorrhage with lactated Ringer (LR) infusion maintained filling pressure at baseline and reduced blood hemoglobin (Hb) to ~5 g/dl. Sheep received 2 g/kg Hb, DCLHb (n = 6), or pRBCs (n = 7); control group received LR alone (n = 6). After 2 h, anesthesia was discontinued; sheep were monitored in the animal intensive care unit for 48 h. DCLHb expanded blood volume more, but increased total blood Hb less, than pRBCs. Lower Hb and increased methemoglobin resulted in lower arterial oxygen content compared with the pRBCs. DCLHb caused pulmonary hypertension (from 13 to 30 mmHg) and elevated filling pressure (from 6 to 15 mmHg). Cardiac outputs (CO) were similar for all groups during anesthesia; however, during recovery CO increased only in the LR and packed pRBCs groups. DCLHb may limit the reflex ability to increase CO after volume expansion. Hemodynamic effects of DCLHb may be exaggerated when infused after large-volume LR.