Robert Jones

ULTRASOUND DOES NOT DETECT EARLY BLOOD LOSS IN HEALTHY VOLUNTEERS DONATING BLOOD

BACKGROUNDnUltrasound has been suggested as a useful non-invasive tool for the detection of early blood loss. Two possible sonographic markers for hypovolemia are the diameter of the inferior vena cava (IVC) and the thickness of the left ventricle (LV).nnnSTUDY OBJECTIVESnThe goal of the study was to evaluate the utility of ultrasound to detect signs of early hemorrhagic shock in healthy volunteers, compared with changes in vital signs.nnnMETHODSnIn the current study, healthy volunteers from blood donation drives were used as models for early hemorrhage. Changes in vital signs, IVC diameter, and LV wall thickness were recorded after approximately 500 cc of blood loss.nnnRESULTSnThirty-eight subjects were enrolled and completed the study. After blood donation, there was a 7-mm Hg (8%) decrease in mean arterial pressure without a significant change in heart rate. There was a decrease in maximum IVC diameter (IVCmax) (12% decrease [95% confidence interval (CI) -6 to -19] in short axis and 20% decrease [95% CI -12 to -27] in long axis), but no change was seen in the respiratory caval index ((IVCmax - IVCmin)/IVCmax) × 100). There was no change in LV wall thickness.nnnCONCLUSIONnIn this study, serial changes in vital signs, IVC diameter, and LV wall thickness were clinically insignificant after approximately 500 cc of blood loss in healthy volunteers.

Evaluating Infant Positioning for Lumbar Puncture Using Sonographic Measurements

OBJECTIVESnHypoxia has been observed when infants undergo lumbar puncture in a tight flexed lateral recumbent position. This study used sonographic measurements of lumbar interspinous spaces to investigate the anatomic necessity and advantage derived from this tight flexed positioning in infants.nnnMETHODSnThis was a brief, prospective, observational study of a convenience sample of patients. Twenty-one healthy infants under 1 month of age were scanned in two positions: prone in a spine-neutral position and lateral recumbent with their knees bent into their chest and their neck flexed. In each position, a 5- to 10-MHz linear array transducer was used to scan midline along the lumbar spinous processes in the sagittal plane. The distances between the spinous processes were measured near the ligamentum flavum using the ultrasound machines calipers. Pulse oximetry was monitored on all infants during flexed positioning.nnnRESULTSnIn the spine-neutral position, all studied interspinous spaces were much wider than a 22-gauge spinal needle (diameter 0.072 cm). The mean (±SD) interspinous spaces for L3-4, L4-5, and L5-S1 in a spine-neutral position were 0.42 (±0.07), 0.37 (±0.06), and 0.36 (±0.11) cm, respectively. Flexing the infants increased the mean lumbar interspinous spaces at L3-4, L4-5, and L5-S1 by 31, 51, and 44%, respectively.nnnCONCLUSIONSnThis study verified that tight, lateral flexed positioning substantially enhances the space between the lumbar spinous processes and that a spine-neutral position also allows for a large enough anatomic interspinous space to perform lumbar puncture. However, further clinical research is required to establish the feasibility of lumbar puncture in a spine-neutral position.

Credentialing and Privileging

Credentialing and privileging are often the last and most difficult processes in an US program that require significant understanding, review, implementation, and strategy to legitimize ultrasound in clinical practice. Definition of the key processes with commentary and suggested steps in regard to credentialing and privileging.

High-frequency linear transducer improves detection of an intrauterine pregnancy in first-trimester ultrasonography

OBJECTIVEnThe objective was to determine if the need for transvaginal ultrasonographic examination can be decreased by the addition of the transabdominal high-frequency, 12-4-MHz linear transducer after a failed examination with the 6-2-mHz curvilinear transducer when evaluating for an intrauterine pregnancy (IUP).nnnMETHODSnThis is a prospective pilot study of women in their first trimester of pregnancy presenting to the emergency department with abdominal pain and/or vaginal bleeding. If no IUP was identified using the curvilinear transducer via the transabdominal approach, they were subsequently scanned using the linear transducer. Patients without evidence of an IUP transabdominally were scanned via the transvaginal approach.nnnRESULTSnEighty-one patients were evaluated; no IUP was visualized in 27 using the standard curvilinear transducer approach, and these then had an ultrasonography performed with the linear transducer. Of these, 9 patients (33.3%; 0.95 confidence interval [CO], 15.5%-51.1%) were found to have an IUP with the linear transducer. For the 18 patients who received a transvaginal scan, 15 patients (83.3%; 0.95 CI, 66.1%-100%) had no IUP identified with the transvaginal transducer, and 3 (16.7%; 0.95 CI, 0%-33.9%) had an IUP identified.nnnCONCLUSIONSnThe transabdominal use of a high-frequency linear transducer in the evaluation of patients in the first trimester after failed curvilinear transducer results in a clinically significant reduction in the need for transvaginal ultrasonography to confirm the presence of an IUP.