Evaluation of Miniature Dynamic Light Scattering Technology for the Assessment of Hemodynamic Status During Graded Hemorrhage and Retransfusion in Pigs.

BACKGROUND: Hemorrhagic shock with occult hypoperfusion is a key challenge to prehospital staff during triage and transfer of patients, especially during mass casualty incidents. Recent advances in Dynamic Light Scattering (DLS), and miniaturization of this technology, has resulted in noninvasive sensors capable of continuously monitoring tissue perfusion. This study evaluated the ability of miniature DLS (mDLS) sensors to assess hemodynamic status in a porcine model of hemorrhage. METHODS: Following ethics committee approval, anesthetized and ventilated pigs underwent graded hemorrhage and then retransfusion. Standard vital signs were monitored in conjunction with a thermodilution cardiac output (CO), central venous pressure (CVP), and arterial blood gases. The mDLS sensor was attached to each animal's leg and all monitoring measurements were taken 5 minutes after completion of each period of hemorrhage and retransfusion to allow equilibration. RESULTS: All measured parameters changed during bleeding and retransfusion. During bleeding; p value were 0.011 for heart rate, 0.07 for CVP, <0.001 for both mean arterial pressure, and mDLS. During retransfusion; p values were 0.023 for heart rate, 0.008 for CVP, and <0.001 for both mean arterial pressure and mDLS. Pearson correlation between changes in mDLS and CO demonstrated r value of 0.917 during hemorrhage and 0.965 during retransfusion. Changes in hemoglobin were not statistically significant during bleeding (p = 0.331) but were during retransfusion (p = 0.0001). Changes of bicarbonate, base excess, and lactate were found to be statistically significant during both phases of the experiment (p = 0.001). CONCLUSIONS: In an animal model of hemorrhagic shock, the mDLS sensor strongly correlates with traditional measures of CO. This initial assessment supports further investigation of this technology in human studies.

Accuracy of transpulmonary thermodilution versus gravimetric measurement of extravascular lung water.

OBJECTIVE: Pulmonary edema is a severe and often life-threatening condition. The diagnosis of pulmonary edema and its quantification have great clinical significance and yet can be difficult. A new technique based on thermodilution measurement using a single indicator has recently been developed (PiCCO, Pulsion Medical Systems, AG Germany). This method allows the measurement of extravascular lung water and thus can quantify degree of pulmonary edema. The technique has not been compared with a gold standard, gravimetric measurement of extravascular lung water. Therefore, the objective of this study was to determine the ability of extravascular lung water measurement with the PiCCO to reflect the extravascular lung water as measured with a gravimetric technique in a dog model of pulmonary edema. DESIGN: Prospective, randomized animal study. SETTING: A university animal research laboratory. SUBJECTS: Fifteen mongrel dogs (n = 5/group) weighing 20-30 kg. INTERVENTIONS: The dogs were anesthetized and mechanically ventilated. Five dogs served as controls; in five dogs hydrostatic pulmonary edema was induced using inflation of a left atrial balloon combined with fluid administration to maintain a high pulmonary artery occlusion pressure; and in five dogs pulmonary edema was induced by intravenous injection of oleic acid. After a period of stabilization in a state of pulmonary edema, extravascular lung water was measured with the PiCCO monitor. The animals were then killed, and extravascular lung water was measured using a gravimetric technique. MEASUREMENTS AND MAIN RESULTS: There was a very close (r =.967, p <.001) relationship between transpulmonary thermodilution and gravimetric measurements. The measurement with the PiCCO was consistently higher, by 3.01 +/- 1.34 mL/kg, than the gravimetric measurement. CONCLUSIONS: Measurement of extravascular lung water using transpulmonary thermodilution with a single indicator is very closely correlated with gravimetric measurement of lung water in both increased permeability and hydrostatic pulmonary edema.

A comparison of lactated ringer's solution to hydroxyethyl starch 6% in a model of severe hemorrhagic shock and continuous bleeding in dogs.

UNLABELLED: In this randomized, controlled study in dogs, we examined the short-term effects of blood pressure targeted fluid resuscitation with colloids or crystalloids solutions on systemic oxygen delivery, and lactate blood concentration. Fluid resuscitation using hydroxyethyl starch (HES) 6% to a mean arterial blood pressure (MAP) of 60 mm Hg was compared with lactated Ringer's solution (LR) to a MAP of 60 or 80 mm Hg (LR60 and LR80, respectively). The model was one of withdrawal of blood to a MAP of 40 mm Hg through an arterial catheter that was then connected to a system allowing bleeding to occur throughout the study whenever MAP exceeded 40 mm Hg. Target MAP was maintained for 60 min with a continuous infusion of the designated fluid replacement. All 15 dogs (5 in each group) survived until the last measurement. Blood loss in the LR80 group (2980 +/- 503 mL) (all values mean +/- SD) was larger than in the LR60 and HES60 groups (1800 +/- 389 mL, and 1820 +/- 219 mL, respectively) (P < 0.001). Whereas 840 +/- 219 mL of HES60 was needed to maintain target MAP, 1880 +/- 425 mL of LR was needed in the LR60 group, and 4590 +/- 930 mL in the LR80 group (P < 0.001). Lactate blood concentrations were smaller and delivered O(2) higher in the HES60 group (35 +/- 17 mg/dL and 239 +/- 61 mL/min, respectively) in comparison to the LR60 group (89 +/- 18 mg/dL and 140 +/- 48 mL/min, respectively) and the LR80 group (75 +/- 23 mg/dL and 153 +/- 17 mL/min, respectively) (P = 0.02 and P = 0.026). In conclusion, fluid resuscitation during uncontrolled bleeding, to a target MAP of 60 mm Hg, using HES60 resulted in larger oxygen delivery and smaller systemic lactate A resuscitation to a target MAP of 60 or 80 mm Hg using LR. IMPLICATIONS: Fluid resuscitation to a target mean arterial blood pressure of 60 mm Hg during uncontrolled bleeding resulted in larger oxygen delivery and smaller systemic lactate concentrations when hydroxyethyl starch 6% was used, in comparison to lactated Ringer's solution resuscitation to a target mean arterial blood pressure of 60 or 80 mm Hg.