Romolo J. Gaspari

Identification of congestive heart failure via respiratory variation of inferior vena cava diameter

INTRODUCTION Rapid diagnosis of volume overload in patients with suspected congestive heart failure (CHF) is necessary for the timely administration of therapeutic agents. We sought to use the measurement of respiratory variation of inferior vena cava (IVC) diameter as a diagnostic tool for identification of CHF in patients presenting with acute dyspnea. METHODS The IVC was measured sonographically during a complete respiratory cycle of 46 patients meeting study criteria. Percentage of respiratory variation of IVC diameter was compared to the diagnosis of CHF or alternative diagnosis. RESULTS Respiratory variation of IVC was smaller in patients with CHF (9.6%) than without CHF (46%) and showed good diagnostic accuracy with area under the receiver operating characteristic curve of 0.96. Receiver operating characteristic curve analysis showed optimum cutoff of 15% variation or less of IVC diameter with 92% sensitivity and 84% specificity for the diagnosis of CHF. CONCLUSION Inferior vena cava ultrasound is a rapid, reliable means for identification of CHF in the acutely dyspneic patient.

LEARNING CURVE OF BEDSIDE ULTRASOUND OF THE GALLBLADDER

Existing guidelines for the number of ultrasounds required before clinical competency are based not on scientific study but on consensus opinion. The objective of this study was to describe the learning curve of limited right upper quadrant ultrasound. This was a prospective descriptive study. Ultrasounds collected over 1 year were reviewed for interpretive and technical errors. Possible errors during bedside ultrasound of the gallbladder include incorrect interpretation, incomplete image acquisition, and improper or poor imaging techniques resulting in poor image quality. The ultrasound image quality was rated on a 4-point scale, with 1 = barely interpretable and 4 = excellent image quality. Required images were rated on an additional 4-point scale, with 4 = all required images were included and 1 = minimal images were recorded. There were 352 patients enrolled by 42 emergency physicians (35 residents and 7 attendings). Gallstones were identified in 13.9% of the patients, and 4.3% of the ultrasounds were indeterminate. Interpretive and technical error rates decreased as the clinician gained experience. The number of poor quality ultrasounds decreased after an average of seven ultrasounds. Inclusion of all required images increased after 25 ultrasounds. Sonographers who had performed over 25 ultrasounds showed excellent agreement with the expert over-read, with only two disagreements, both from a single individual. It was concluded that clinicians are clinically competent after performing 25 ultrasounds of the gallbladder.

Inferior vena cava displacement during respirophasic ultrasound imaging

BackgroundUltrasound measurement of dynamic changes in inferior vena cava (IVC) diameter can be used to assess intravascular volume status in critically ill patients, but published studies vary in accuracy as well as recommended diagnostic cutoffs. Part of this variability may be related to movements of the vessel relative to the transducer during the respiratory cycle which results in unintended comparison of different points of the IVC at end expiration and inspiration, possibly introducing error related to variations in normal anatomy. The objective of this study was to quantify both craniocaudal and mediolateral movements of the IVC as well as the vessels axis of collapse during respirophasic ultrasound imaging.MethodsPatients were enrolled from a single urban academic emergency department with ultrasound examinations performed by sonographers experienced in IVC ultrasound. The IVC was imaged from the level of the diaphragm along its entire course to its bifurcation with diameter measurements and respiratory collapse measured at a single point inferior to the confluence of the hepatic veins. While imaging the vessel in its long axis, movement in a craniocaudal direction during respiration was measured by tracking the movement of a fixed point across the field of view. Likewise, imaging the short axis of the IVC allowed for measurement of mediolateral displacement as well as the vessels angle of collapse relative to vertical.ResultsSeventy patients were enrolled over a 6-month period. The average diameter of the IVC was 13.8 mm (95% CI 8.41 to 19.2 mm), with a mean respiratory collapse of 34.8% (95% CI 19.5% to 50.2%). Movement of the vessel relative to the transducer occurred in both mediolateral and craniocaudal directions. Movement was greater in the craniocaudal direction at 21.7 mm compared to the mediolateral movement at 3.9 mm (p < 0.001). Angle of collapse assessed in the transverse plane averaged 115° (95% CI 112° to 118°).ConclusionsMovement of the IVC occurs in both mediolateral and craniocaudal directions during respirophasic ultrasound imaging. Further, collapse of the vessel occurs not at true vertical (90°) but 25° off this axis. Technical approach to IVC assessment needs to be tailored to account for these factors.

A Randomized Controlled Trial of Incision and Drainage Versus Ultrasonographically Guided Needle Aspiration for Skin Abscesses and the Effect of Methicillin-Resistant Staphylococcus aureus

STUDY OBJECTIVE The incidence of skin and soft tissue infections has increased dramatically during the last decade, in part because of increased prevalence of community-acquired methicillin-resistant Staphylococcus aureus (CA-MRSA). Incision and drainage is considered the primary intervention; however, some clinicians prefer ultrasonographically guided needle aspiration because it represents a less invasive alternative. Our hypothesis is that ultrasonographically guided needle aspiration is equivalent to incision and drainage in treating simple skin and soft tissue abscesses. METHODS This study was a nonblinded randomized controlled trial. Patients with uncomplicated superficial abscesses were randomized to incision and drainage with packing or ultrasonographically guided needle aspiration. Purulence obtained from the abscess was cultured to identify the causative organism. Bedside ultrasonography was performed pre- and postintervention to confirm the presence or absence of an abscess cavity. Patients were followed up at 48 hours (in person by a clinician) and on day 7 (telephone follow-up by research staff). The primary outcome was a combination of sonographic resolution and clinical resolution of the signs and symptoms of ongoing infection at day 7. The signs and symptoms of ongoing infection include increasing pain, erythema, and the presence of pus. Resolution was assessed with both sonographic resolution (day 0 and day 2) and improvement of clinical symptoms (day 2) and resolution of clinical symptoms (day 7) without further intervention. RESULTS A total of 101 patients were enrolled, 54 incision and drainage and 47 ultrasonographically guided needle aspiration patients. At initial presentation, 60% (95% confidence interval [CI] 45% to 70%) of needle aspirations yielded little or no purulence, despite sonographic visualization of an abscess cavity and sonographic guidance during the procedure. The overall success of ultrasonographically guided needle aspiration was 26% (95% CI 18% to 44%) compared with 80% (95% CI 66% to 89%) success in patients randomized to incision and drainage. The difference between groups was 54% (95% CI 35% to 69%). Overall success of both incision and drainage and ultrasonographically guided needle aspiration was lower in patients with CA-MRSA. Patients with CA-MRSA (n=33) were less likely to receive successful drainage with needle aspiration (8% versus 55%) or incision and drainage (61% versus 89%). The difference for needle aspiration and incision and drainage was 47% (95% CI 15% to 57%) and 28% (95% CI 4% to 45%), respectively. CONCLUSION Ultrasonographically guided needle aspiration is insufficient therapy for skin abscesses. The presence of CA-MRSA decreases the success of both incision and drainage and ultrasonographically guided needle aspiration.

Diazepam Inhibits Organophosphate‐induced Central Respiratory Depression

OBJECTIVES Current evidence suggests that mortality from acute organophosphate (OP) poisoning is partially mediated through central nervous system (CNS) respiratory center depression (CRD). However, the exact mechanism of OP-induced CRD is unknown. In these studies, the authors investigated the hypothesis that OP-induced CRD is the result of overstimulation of CNS respiratory centers. METHODS Wistar rats received prophylaxis with either normal saline (controls), atropine, the peripherally acting anticholinergics glycopyrrolate (GLYC), ipratropium bromide (IB), or the CNS respiratory center attenuator diazepam. To determine if a dual CNS/peripheral cholinergic mechanism is responsible for animal death, two additional groups received combination treatment with diazepam plus either IB or GLYC. All treatments were completed 5 minutes before OP with subcutaneous dichlorvos. Differences in 10-minute and 24-hour mortality were assessed by the Fisher exact test. RESULTS Dichlorvos poisoning resulted in profound fasciculations without obvious seizure in all cohorts. In controls and animals treated with peripherally acting anticholinergics, fasciculations were followed by sedation and respiratory arrest (0% 10-minute survival in all cohorts). In contrast, pretreatment with either atropine or diazepam significantly improved 10-minute survival (100% and 44%, respectively). Although GLYC or IB afforded no protection when given alone, when delivered in conjunction with diazepam, the combination significantly improved survival (both groups 88% at 24 hours), suggesting a dual CNS/pulmonary muscarinic mechanism of lethality. CONCLUSIONS The central respiratory depressant diazepam paradoxically attenuates organophosphate-induced respiratory depression, and when combined with peripherally acting anticholinergic agents, reduces mortality in a rat model of severe acute OP poisoning.

Central respiratory failure during acute organophosphate poisoning

Organophosphate (OP) pesticide poisoning is a global health problem with over 250,000 deaths per year. OPs affect neuronal signaling through acetylcholine (Ach) neurotransmission via inhibition of acetylcholinesterase (AChE), leading to accumulation of Ach at the synaptic cleft and excessive stimulation at post-synaptic receptors. Mortality due to OP agents is attributed to respiratory dysfunction, including central apnea. Cholinergic circuits are integral to many aspects of the central control of respiration, however it is unclear which mechanisms predominate during acute OP intoxication. A more complete understanding of the cholinergic aspects of both respiratory control as well as neural modification of pulmonary function is needed to better understand OP-induced respiratory dysfunction. In this article, we review the physiologic mechanisms of acute OP exposure in the context of the known cholinergic contributions to the central control of respiration. We also discuss the potential central cholinergic contributions to the known peripheral physiologic effects of OP intoxication.

Emergency department point-of-care ultrasound in out-of-hospital and in-ED cardiac arrest

BACKGROUND Point-of-care ultrasound has been suggested to improve outcomes from advanced cardiac life support (ACLS), but no large studies have explored how it should be incorporated into ACLS. Our aim was to determine whether cardiac activity on ultrasound during ACLS is associated with improved survival. METHODS We conducted a non-randomized, prospective, protocol-driven observational study at 20 hospitals across United States and Canada. Patients presenting with out-of-hospital arrest or in-ED arrest with pulseless electrical activity or asystole were included. An ultrasound was performed at the beginning and end of ACLS. The primary outcome was survival to hospital admission. Secondary outcomes included survival to hospital discharge and return of spontaneous circulation. FINDINGS 793 patients were enrolled, 208 (26.2%) survived the initial resuscitation, 114 (14.4%) survived to hospital admission, and 13 (1.6%) survived to hospital discharge. Cardiac activity on US was the variable most associated with survival at all time points. On multivariate regression modeling, cardiac activity was associated with increased survival to hospital admission (OR 3.6, 2.2-5.9) and hospital discharge (OR 5.7, 1.5-21.9). No cardiac activity on US was associated with non-survival, but 0.6% (95% CI 0.3-2.3) survived to discharge. Ultrasound identified findings that responded to non-ACLS interventions. Patients with pericardial effusion and pericardiocentesis demonstrated higher survival rates (15.4%) compared to all others (1.3%). CONCLUSION Cardiac activity on ultrasound was the variable most associated with survival following cardiac arrest. Ultrasound during cardiac arrest identifies interventions outside of the standard ACLS algorithm.

Correlation of Visual Axis and Coronal Axis Measurements of the Optic Nerve Sheath Diameter

Objective. There are several approaches to sonographic imaging and measurement of the optic nerve sheath diameter (ONSD). In this study, we sought to compare visual axis measurements of the optic nerve sheath (ONS) with traditional coronal axis measurements to assess for correlation. Methods. The ONS was visualized in 2 views on both eyes of healthy volunteers using an 8.5‐MHz probe. Coronal axis views were obtained with the probe placed at the lateral canthus directed nasally posterior to the globe. Subsequent imaging was made along the midline visual axis. The diameter in this view was measured at several points posterior to the sclera (2, 3, 6, 9, 12, and 15 mm). Results. Twenty‐seven subjects were enrolled (54 scans). There was a significant difference between ONSDs measured in each axis, with a coronal axis mean diameter of 3.4 mm and visual axis mean diameters at 2, 3, 6, 9, 12, and 15 mm of 4.28, 4.32, 5.15, 5.74, 6.39, and 7.42 mm, respectively (P < .05). The Pearson coefficient showed no correlation between coronal axis and visual axis measurements, with R values ranging from 0.51 to 0.69. There was a statistically significant increase in the ONSD as the nerve coursed posteriorly when measured in the visual axis. Conclusions. Visual axis measurements do not reliably correlate with coronal axis measurements. The consistently larger diameter measured in the visual axis as well as the gradually increasing diameter posteriorly suggests measurement of an artifactual shadow rather than the true ONS.

Diphenhydramine as a protective agent in a rat model of acute, lethal organophosphate poisoning

OBJECTIVE To evaluate the effects of diphenhydramine chloride (DPH) on mortality in a rat model of acute, severe organophosphate poisoning (OP). METHODS Wistar rats (n = 40) were randomized to pretreatment with either normal saline (controls), 5 mg/kg atropine, 3 mg/kg DPH, 15 mg/kg DPH, or 30 mg/kg DPH given as a single intramuscular injection 5 minutes prior to a subcutaneous injection of 25 mg/kg dichlorvos (n = 8 per group). The primary endpoint was 10-minute survival. Survival at 24 hours was a secondary endpoint. Comparison of survival rates between groups was carried out by ANOVA and the Student-Newman-Keuls test. RESULTS Dichlorvos exposure resulted in profound fasciculations within 2 minutes of injection in all cohorts. In controls, fasciculations were followed by respiratory arrest within 10 minutes (0% survival). The rats receiving atropine pre-treatment exhibited similar fasciculations (nicotinic effects) without subsequent respiratory arrest, resulting in a significant improvement in survival (88%, p < 0.001). The DPH-treated rats exhibited a significant dose-dependent reduction in mortality, with the 3 mg/kg, 15 mg/kg, and 30 mg/kg groups demonstrating 0%, 25%, and 100% survival, respectively. There was no additional mortality between 10 minutes and 24 hours in any group. There was no significant difference in survival between the high-dose DPH and the atropine groups. CONCLUSIONS Diphenhydramine chloride significantly reduced mortality in rats with acute, severe dichlorvos exposure.

Use of Ultrasound Elastography for Skin and Subcutaneous Abscesses

Objective. Elastography is a new adjunct to real‐time ultrasound imaging that overlays traditional B‐mode imaging with a color graphic representation of tissue elasticity. Soft tissue infections are common presenting conditions in the emergency department, and elastography has the potential to help in diagnosis and treatment of evolving soft tissue infections as they progress from induration to fluctuant abscesses, but to our knowledge, no studies of elastography in superficial soft tissue have been published. We hypothesized that elastography would provide increased information regarding skin abscesses. Methods. This was a prospective study of patients with suspected skin abscesses requiring surgical drainage in the emergency department of an urban tertiary care center. Abscesses were imaged with B‐mode imaging and elastography in orthogonal planes. Ultrasound images were analyzed for characteristics of the elastographic images. Results. A total of 50 patients with suspected skin abscesses underwent B‐mode imaging and elastography. Elastography accurately differentiated the induration surrounding the abscess from the surrounding healthy tissue, a differentiation that was not visible on B‐mode imaging. The elastographic properties of the abscess cavity were variable and not always seen, even with purulence identified during incision and drainage. In some cases, elastography identified abscess cavities not seen on B‐mode imaging. When seen, the abscess cavity could be characterized by elastographic color and speckle patterns. Conclusions. Elastography identified the tissue induration and some abscess cavities not seen on B‐mode imaging. It offers a way to characterize abscesses that may be useful clinically, but more research is needed.