Augmentation of peripheral venous diameter for ultrasound-guided peripheral intravenous line insertion.

OBJECTIVES: Ultrasound-guided intravenous line placement is utilized often in the emergency department for venous access in patients whose veins are difficult to cannulate by traditional methods. This study aims to identify specific interventions that will augment venous cross-sectional area. METHODS: Residents and medical students volunteers each had their basilic vein identified using the linear array probe on an ultrasound. The area of the vein was measured with no intervention with the arm positioned parallel to the floor as well as approximately 45 degrees below the level of the bed. These two positions were repeated with the following interventions: one standard rubber tourniquet applied proximal to the vein measurement, an additional rubber tourniquet applied proximal to first tourniquet, blood pressure cuff inflated to between 160 and 200 mmHg applied proximal to the vein, CAT battle tourniquet application proximal to measurement site, and soaked warm towel applied to brachium for up to one minute. The primary outcome was to evaluate the increase in venous cross-sectional area from the baseline measurement after the interventions. RESULTS: We had 41 participants in this study. All interventions were statistically significant in increasing venous cross-sectional area as compared to no intervention, with the most significant augmentation being from the CAT battle tourniquet (mean change +7.32 mm2, 95% CI, 5.73-8.91 mm2) . The change in position of the arm, was not statistically significant for any intervention except for the CAT tourniquet (mean change -1.74 mm2, 95% CI, -0.54 to -2.93 mm2). There was no significant difference between two tourniquets and blood pressure cuff (mean change +0.58 mm2, 95% CI, -1.13 to +2.29 mm2), but there was a significant increase in cross-sectional area with CAT tourniquet use compared to blood pressure cuff (mean change +1.62 mm2, 95% CI, 0.29-2.95 mm2). Lastly, two tourniquets increased cross- sectional area compared to one tourniquet (mean change +2.20 mm2, 95% CI, 1.14 - +3.26 mm2). CONCLUSIONS: This study identified several potential interventions for maximizing venous cross-sectional area on ultrasound. All the tested interventions resulted in statistically significant increases in cross-sectional area. Arm positioning did not show significant changes in most interventions, with the exception of the CAT tourniquet. Further studies should be performed on how these maneuvers affect success in ultrasound-guided intravenous line placement.

Effect of a single free food presentation on extinction responding in a multiple schedule.

The present study was designed to assess the effect of a single, response-independent food presentation on responding during extinction. Using a two-component multiple schedule, we examined differences in pigeons' extinction responding resulting from a single response-independent food presentation occurring at the beginning of the experimental session (30-s prior to the beginning of the first component). One component presented reinforcement according to a variable interval 45-s schedule and the second presented reinforcement according to a variable interval 180-s schedule. After establishing stable baseline responding we extinguished responding. We systematically manipulated the presence or absence of a single 3-s free food presentation using the food hopper that occurred 30-s prior to the presentation of the first component. We found the single free food presentation increased persistence of responding in extinction. This finding is inconsistent with behavioral momentum theory inasmuch as it assigns a response disruptive role to food presentations occurring outside of the context of the target operant.

Application of impedance threshold devices during cardiopulmonary cerebral resuscitation.

OBJECTIVE: To review the use of impedance threshold devices (ITD) during CPCR, their proposed mechanism of action, and their application in veterinary medicine. DATA SOURCES: Data sources include scientific reviews and original research publications using the PubMed search engine with the following keywords: 'impedance threshold device' and 'resuscitation' and the Veterinary Information Network search function using the keywords 'impedance threshold device.' HUMAN DATA SYNTHESIS: Studies in human medicine have demonstrated that the use of an ITD during CPCR in patients during out-of-hospital cardiac arrest improves coronary perfusion pressure and cerebral perfusion pressure. This improvement in vital organ blood flow results in increased cardiac output and faster return of spontaneous circulation. The use of an ITD has been studied in people and currently holds a class IIb level of recommendation according to the 2010 American Heart Association Guidelines for CPR and Emergency Cardiovascular Care. This device is recommended as a way to improve hemodynamics during CPCR by enhancing venous return and avoiding hyperventilation, thereby increasing the likelihood of a successful resuscitation. VETERINARY DATA SYNTHESIS: Multiple controlled studies using pigs with ventricular fibrillation induced cardiopulmonary arrest have demonstrated increased myocardial and cerebral perfusion with the use of an ITD. These studies have emphasized the importance of decreasing intrathoracic pressures during the decompression phase of CPCR and avoiding hyperventilation in order to maximize vital organ blood flow. CONCLUSIONS: Use of an ITD during CPCR in human and animal studies has demonstrated improved vital organ perfusion and faster return of spontaneous circulation. However, the majority of these studies have been carried out in people during out-of-hospital cardiac arrest and ventricular fibrillation cardiopulmonary arrest pig models. Further studies evaluating the use of an ITD during CPCR in the veterinary hospital setting are warranted.

Beyond blood gases: making use of additional oxygenation parameters and plasma electrolytes in the emergency room.

When provided with an emergency blood gas or electrolyte readout, clinicians must identify the critical parameters that require immediate intervention. This article provides concepts in oxygenation and electrolyte evaluation to help fine-tune the initial treatment and monitoring orders for emergency patients.

Arterial and venous blood gases: indications, interpretations, and clinical applications.

Blood gas analysis is frequently requested as part of the point-of-care testing for emergency or critical care patients presenting with metabolic or respiratory abnormalities. With the advent of portable units, information regarding a patient's acid-base, ventilation, and oxygenation status can be rapidly obtained. This article provides essential information on arterial and venous blood gas analysis with the goal of helping clinicians integrate such data in their case management.