title: Is bacteriostatic saline superior to normal saline as an echocardiographic contrast agent?
abstract: Objective data on the performance characteristics and physical properties of commercially available saline formulations [normal saline (NS) vs. bacteriostatic normal saline (bNS)] are sparse. This study sought to compare the in vitro physical properties and in vivo characteristics of two commonly employed echocardiographic saline contrast agents in an attempt to assess superiority. Nineteen patients undergoing transesophageal echocardiograms were each administered agitated regular NS and bNS injections in random order and in a blinded manner according to a standardized protocol. Video time-intensity (TI) curves were constructed from a representative region of interest, placed paraseptally within the right atrium, in the bicaval view. TI curves were analyzed for maximal plateau acoustic intensity (Vmax, dB) and dwell time (DT, s), defined as time duration between onset of Vmax and decay of video intensity below clinically useful levels, reflecting the duration of homogenous opacification of the right atrium. To further characterize the physical properties of the bubbles in vitro, fixed aliquots of similarly agitated saline were injected into a glass well slide-cover slip assembly and examined using an optical microscope to determine bubble diameter in microns (µm) and concentration [bubble count/high power field (hpf)]. A higher acoustic intensity (a less negative dB level), higher bubble concentration and longer DT were considered properties of a superior contrast agent. For statistical analysis, a paired t test was conducted to evaluate the differences in means of Vmax and DT. Compared to NS, bNS administration was associated with superior opacification (video intensity -8.69 ± 4.7 vs. -10.46 ± 4.1 dB, P = 0.002), longer DT (17.3 ± 6.1 vs. 10.2 ± 3.7 s) in vivo and smaller mean bubble size (43.4 vs. 58.6 μm) and higher bubble concentration (1,002 vs. 298 bubble/hpf) in vitro. bNS provides higher intensity and more sustained opacification of the right atrium compared to NS. Higher bubble concentration and stability appear to be additional desirable rheological characteristics favoring bNS as a contrast agent.
authors.affiliation: Division of Cardiology, Department of Internal Medicine, Detroit Medical Center, Harper University Hospital, Wayne State University, 3990 John R, 8 Brush, Detroit, MI, 48201, USA.
authors.forename: Shaun
authors.initials: S
authors.lastname: Cardozo
authors.forename: Prasad
authors.initials: P
authors.lastname: Gunasekaran
authors.forename: Hena
authors.initials: H
authors.lastname: Patel
authors.forename: Timothy
authors.initials: T
authors.lastname: McGorisk
authors.forename: Mehrdad
authors.initials: M
authors.lastname: Toosi
authors.forename: Haroon
authors.initials: H
authors.lastname: Faraz
authors.forename: Sandip
authors.initials: S
authors.lastname: Zalawadiya
authors.forename: Issa
authors.initials: I
authors.lastname: Alesh
authors.forename: Anupama
authors.initials: A
authors.lastname: Kottam
authors.forename: Luis
authors.initials: L
authors.lastname: Afonso
mesh_terms: D000900:Anti-Bacterial Agents / Q000737:chemistry / Q000494:pharmacology*; D019905:Benzyl Alcohol / Q000737:chemistry / Q000494:pharmacology*; D003287:Contrast Media / Q000737:chemistry; D004340:Drug Contamination / Q000517:prevention & control*; D017548:Echocardiography, Transesophageal / Q000379:methods*; D006801:Humans; D008824:Michigan; D045423:Microbubbles; D011237:Predictive Value of Tests; D011310:Preservatives, Pharmaceutical / Q000737:chemistry / Q000494:pharmacology*; D012212:Rheology; D012965:Sodium Chloride / Q000737:chemistry; D013997:Time Factors; D014741:Video Recording
chemical_list: D000900:Anti-Bacterial Agents; D003287:Contrast Media; D011310:Preservatives, Pharmaceutical; D012965:Sodium Chloride; D019905:Benzyl Alcohol