Focused cardiac ultrasound is feasible in parturients; a prospective observational study.

BACKGROUND: In pregnancy, the major causes of morbidity and mortality include diseases that affect circulation profoundly and restoration of normal circulation is a key objective. Focused cardiac ultrasound provides information on the individual determinants of circulation and has a significant impact on patient management. This study aimed to determine the feasibility of focused cardiac ultrasound in term parturients. METHODS: Forty parturients underwent focused cardiac ultrasound. Parasternal long-axis, parasternal short-axis, 4-chamber and subcostal views were performed in the left-lateral position and the supine position by a novice operator. All images were graded on the following scale: 1 = no image; 2 = poor and insufficient image; 3 = sufficient image quality; 4 = good image quality; 5 = perfect image quality. A cut-off grade of three signified images sufficient for clinical decision-making. RESULTS: Images sufficient for clinical decision-making were obtained in all patients when including all imaging views. 37/40 (93 %) patients presented images of grade ≥ 4, whereas 10/40 (25%) patients had images of grade 5. Image grades were higher in the left lateral position (all P < 0.001). Parturients with a body mass index ≤ 30 kg/m2 did not present different image grades than parturients with a higher body mass index (P = 0.753). Subcostal views could not be obtained. CONCLUSION: Focused cardiac ultrasound is feasible in the obstetric population and images of sufficient quality for clinical decision-making were obtained in all parturients by an operator with limited experience.

Ultrasound-guidance outperforms the palpation technique for peripheral venous catheterisation in anaesthetised toddlers: a randomised study.

BACKGROUND: Traditional palpation technique for peripheral venous catheter (PVC) placement can be challenging. We aimed to compare the Dynamic Needle Tip Positioning (DNTP) ultrasound technique with the palpation technique for PVC placement in anaesthetised toddlers undergoing elective, low-risk procedures. METHODS: The study was a randomised, controlled, crossover study. Five operators applied both techniques for PVC on 50 children < 4 years. The primary endpoint was first attempt success rate. The secondary endpoints were: (1) overall success rate, (2) number of skin perforations, (3) number of needle redirections, (4) number of catheters used, (5) total time, (6) needle manipulation time, (7) distance to the nearest flexion crease, (8) anatomical region of catheterisation, (9) size of the catheters and (10) the effects of visibility, and palpability of the veins. RESULTS: The first attempt success rate and the overall success rate were significantly higher in the DNTP group (42/50 vs. 30/50, P = 0.029), (50/50 vs. 42/50, P = 0.008). Furthermore, a lower number of skin perforations (60 vs. 84, P = 0.013) and needle redirections (14 vs. 131, P < 0.001) and increased distance to the nearest flexion crease (P < 0.001) were seen in the DNTP group. There were no significant differences in number of catheters used (60 vs. 75 P = 0.050) or total time (P = 0.073), however, the needle manipulation time was longer in the DNTP group (P = 0.011). The success rate decreased with less visible and palpable veins in the palpation group (p = 0.006). CONCLUSION: Ultrasound-guidance outperforms the traditional palpation technique for peripheral venous catheterisation in anaesthetised toddlers undergoing elective, low-risk procedures.

Asphyxia causes ultrasonographic D-shaping of the left ventricle--an experimental porcine study.

INTRODUCTION: In critical care, early diagnosis and correct treatment are of the utmost importance. Focused ultrasonography has gained acceptance as a pivotal tool for this by elucidating the underlying pathology. For example, massive pulmonary embolism is characterised by right ventricular dilatation. However, theoretically these characteristics might also be generated by asphyxia and the consequent hypoxia. We aimed to evaluate the ultrasonographic characteristics of asphyxia in a porcine model. METHODS: Nineteen (13 intervention, 6 control) piglets were subjected to asphyxia until cardiac arrest, by disconnecting the ventilator tube. Ultrasonographic short-axis cine loops of the left ventricle were obtained every 30 seconds. The left ventricular (LV) eccentricity index (index of LV D-shaping) was quantified along with LV end-diastolic/end-systolic areas. Invasive pressures were measured throughout. RESULTS: The LV eccentricity index increased from 1.14 (1.10-1.31) to 1.86 (1.48-2.38), (P = 0.002), after 1.5 min, receded thereafter to baseline levels followed by a second increase after 5.5 min. LV end-diastolic area decreased from 11.6 cm(2) (11.1-13.2) to 6.3 cm(2) (3.3 -11.0) after 2.0 min (P = 0.009). Subsequently, values returned to the baseline level. DISCUSSION: The early and transient acute dilatation of the RV, coinciding with D-shaping of the LV and decrease in LV end-diastolic area seen in our study represent a combination of ultrasonographic characteristics normally attributed to pulmonary embolism. Early changes in ventricular chamber sizes and shape with septal flattening related to asphyxia can occur, but appear to be transient and disappear as circulatory collapse progresses, in an animal model. Despite this, asphyxia may represent a cause of ultrasonographic misinterpretation.

Effects of levosimendan in patients with left ventricular hypertrophy undergoing aortic valve replacement.

BACKGROUND: Left ventricular hypertrophy is associated with adverse outcomes, including death, during cardiac surgery. This may be facilitated by an increased oxygen demand and diastolic dysfunction. Levosimendan augments haemodynamics without further oxygen consumption and improves echocardiographic indices of diastolic dysfunction. This study aimed to describe the haemodynamic effects of short-term pre- and intra-operative levosimendan infusion including advanced echocardiographic measures of diastolic and systolic heart function. METHODS: The study was randomised, double-blinded and placebo-controlled performed at a single-centre university hospital. Patients with left ventricular hypertrophy and ejection fraction > 45% scheduled for single procedure aortic valve replacement were included and randomised to infusion of either levosimendan 0.1 µg/kg/min or placebo from 4 h before anaesthesia to the end of surgery. Outcome measures were echocardiographic indices of left ventricular diastolic function: E/e' (primary endpoint), e', e'/a' and indices of systolic function: longitudinal strain, ejection fraction and s'. Patients were followed until 6 months after surgery. In addition, invasive haemodynamic measures were obtained perioperatively. RESULTS: The trial was prematurely terminated due to an overall high incidence of post-operative atrial fibrillation (15/20, P = 0.002) after inclusion of 20 patients. The relative decrease in perioperative cardiac index was lower (P = 0.016) in the levosimendan group. There was no difference in E/e', and similar results were found for all measures of systolic function. CONCLUSION: Short-term levosimendan caused a transient relative increase in cardiac index, but no effect was seen on the first post-operative day and up to 6 months post-operatively with indices of systolic and diastolic heart function.

Ultrasonography-guided radial artery catheterization is superior compared with the traditional palpation technique: a prospective, randomized, blinded, crossover study.

BACKGROUND: Radial artery catheterization is gaining popularity for diagnostic and interventional procedures. Palpation technique is widely used for the procedure, but ultrasonography has been shown to increase catheterization success. A recently described ultrasonography technique is termed 'dynamic needle tip positioning'. We aimed to compare the traditional palpation technique and dynamic needle tip positioning technique in regard to clinically relevant end points. METHODS: The study was conducted as a randomized, patient-blinded, crossover study. Patients underwent bilateral radial artery catheterization using both techniques. The primary end point of the study was needle manipulation time. Additional end points were (1) the number of skin perforations, (2) the number of attempts targeting the vessel, (3) the number of catheters placed in first attempt and (4) the number of catheters used. RESULTS: Forty patients were analyzed. There was no significant difference in median needle manipulation time [32 s (range 11-96 s) vs. 39 s (range 9-575 s), P = 0.525], although the variance was lower in the dynamic needle tip positioning group (P < 0.001). In the traditional palpation technique group, a higher number of skin perforations (57 vs. 40, P = 0.003), catheters (46 vs. 40, P = 0.025) and attempts targeting the vessel (104 vs. 43, P < 0.001) were necessary compared with the ultrasonography dynamic needle tip positioning group. First attempt success rate was significantly higher in the ultrasonography dynamic needle tip positioning group (23/40 vs. 38/40, P < 0.001). CONCLUSION: Ultrasonography guidance using the dynamic needle tip positioning technique for radial artery catheterization significantly improves clinically relevant aspects of the procedure.

Pleural effusion decreases left ventricular pre-load and causes haemodynamic compromise: an experimental porcine study.

BACKGROUND: Although pleural effusion is a common complication in critically ill patients, detailed knowledge is missing about the haemodynamic impact and the underlining mechanisms. The aim of this study was to evaluate the haemodynamic effect of incremental pleural effusion by means of invasive haemodynamic parameters and transthoracic echocardiography. METHODS: This experimental interventional study was conducted using 22 female piglets (17.5-21.5 kg) randomized for right-side (n = 9) and left-side (n = 9) pleural effusion, or sham operation (n = 4). Pleural effusion was induced by infusing incremental volumes of saline into the pleural cavity. Invasive haemodynamic measurements and echocardiographical images were obtained at baseline, a volume of 45 ml/kg, a volume of 75 ml/kg and 45 min after drainage. RESULTS: No difference (all P > 0.147) was found between right- and left-side pleural effusion, and the groups were thus pooled. At 45 ml/kg cardiac output, mean arterial pressure, stroke volume and mixed venous saturation decreased (all P < 0.003); central venous pressure and pulmonary arterial pressure increased (both P > 0.003) at this point. The changes accelerated at 75 ml/kg. At 45 ml/kg left ventricular pre-load in terms of end-diastolic area decreased significantly (P < 0.001). The effect on haemodynamics and cardiac dimensions changed dramatically at 75 ml/kg. Cardiac output, mean arterial pressure, central venous pressure and left ventricular end-diastolic area returned to normal during a recovery period of 45 min (all P > 0.061). CONCLUSION: Incremental volumes of unilateral pleural effusion induced a significant haemodynamic impact fully reversible after drainage. Pleural effusion causes a significant decrease of left ventricular pre-load in a diverse picture of haemodynamic compromise.

Agreement between cardiac outputs by four-dimensional echocardiography and thermodilution method is poor.

OBJECTIVE: The objective of the study was to determine the agreement of cardiac output (CO) measured by four-dimensional echocardiography (4D echo) to simultaneously obtain CO from pulmonary artery catheter (PAC) using thermodilution technique. MATERIALS AND METHODS: Sixty-three comparable readings from 27 patients scheduled for elective coronary artery bypass were included. All echocardiographic measurements were obtained by one experienced echocardiographer. All echo images were analyzed independently and blinded from PAC-obtained measurements. Analysis was primarily done by Bland and Altman plot. The collected data were further controlled for interobserver bias and image quality. RESULTS: Differences in CO measurements increased with higher CO, hence values were logarithmically transformed. On the logaritmic scale, the 4D echo underestimated CO by 0.37 l/min compared with PAC, indicating that PAC measurements were 1.45 times higher than the 4D echo (95% confidence interval 1.32-1.52) and limits of agreement 0.97-2.14). The interobserver bias of 4D echo measurement analysis was 0.29 l/min (95% confidence interval 0.16-0.42) and limits of agreement -0.8-1.38). No difference was seen in image quality between comparisons with good agreement compared with comparisons with poor agreement. CONCLUSION: The agreement between COs by 4D echo and standard PAC thermodilution technique was poor. 4D echo underestimates CO as compared with PAC. This is most likely caused by the analysis software or low frame rate inherent to the technique.

Ultrasound assessment of inferior vena cava collapsibility is not a valid measure of preload changes during triggered positive pressure ventilation: a controlled cross-over study.

PURPOSE: Respiratory changes in the diameter of the inferior vena cava (IVC) have been validated as a measure of volume status and preload responsiveness during spontaneous breathing and mechanical ventilation. However, many intensive care patients are ventilated with triggered positive pressure ventilation (PPV). In this setting, there is no evidence regarding IVC collapsibility (IVCc) as a surrogate for preload. We aimed to elucidate the effects of increasing levels of triggered PPV and of varying preload conditions on the IVCc. MATERIALS AND METHODS: 10 healthy volunteers were connected to a ventilator through a tight-fitting mask and exposed to 6 different levels of positive end-expiratory pressure (PEEP) and pressure support (PS) after a baseline reading. All ventilator settings were performed at neutral preload (horizontal position), low preload (reverse-Trendelenburg) and high preload (Trendelenburg position with an intravenous fluid bolus). At each ventilator setting, the IVC was imaged throughout at least 1 respiratory cycle using 3 commonly used ultrasound techniques including sagittal M-mode and 2-dimensional echocardiography in both sagittal and transverse views. RESULTS: Increasing PS diminished IVCc (p = 0.01) in the reverse-Trendelenburg position, and increasing PEEP caused a higher IVCc in the Trendelenburg position (p = 0.02). In the horizontal position, no significant effects of increasing PS, PEEP or a combination of the two were seen. Overall ANOVA analysis showed that IVCc was not independent of preload. During PPV, IVCc was highest at neutral preload at most ventilator settings, IVCc was lowest at low preload, while high preload generally facilitated an IVCc between neutral and high preload. In addition, sagittal M-mode and transverse 2-dimensional echocardiography overestimated IVCc as compared to sagittal 2-dimensional echocardiography. CONCLUSION: The compiled results of this study show that IVCc cannot be held as a valid measure of preload status during PPV. This may be explained by systematic alterations in other determinants for IVCc. Comparison of methods encourages the use of sagittal 2-dimensional echocardiography for dynamic imaging of the IVC. Sagittal M-mode and transverse 2-dimensional echocardiography overestimate IVCc as compared to sagittal 2-dimensional echocardiography.

Focus-assessed transthoracic echocardiography in the sitting position: two life-saving cases.

Focus-Assessed Transthoracic Echocardiography (FATE) is a point-of-care ultrasound protocol allowing the fast evaluation of the cardio-pulmonary status. It has been well established that patients with an exacerbation of chronic obstructive lung disease and lung oedema benefit from the sitting position. These and other medical emergency situations may prevent patients from attaining the supine position, thus precluding standard echocardiography. Portable ultrasound machines with a wide range of different probes are now available at limited costs. This allows the physician to bring point-of-care ultrasound to the patient in almost any location. We present two cases of severely ill patients where FATE was performed in the sitting position with decisive impact on subsequent therapy.

New pocket echocardiography device is interchangeable with high-end portable system when performed by experienced examiners.

BACKGROUND: Cardiovascular status is a crucial determinant in the pre-operative assessment of patients for surgery as well as for the handling of patients with acute illness. We hypothesized that focus-assessed transthoracic echocardiography (FATE) could be performed with the subject in the semi-recumbent position. The aim was also to test whether the image quality of Vscan is interchangeable with a conventional high-quality portable echocardiography system. Furthermore, we evaluated the time needed to achieve an interpretable four-chamber view and to complete a full FATE examination. METHODS: Sixty-one subjects were included. All subjects were examined in accordance with the FATE protocol in the semi-recumbent position on two different systems: the novel Vscan pocket device and the high-quality portable Vivid i system. Two evaluations were performed. In group A (n=30), the focus was on image quality. In group B (n=31), the focus was on the time consumed. RESULTS: Group A: All patients (100%) had at least one image suitable for interpretation and no significant difference in image quality (P=0.32) was found between the two different systems. Group B: The mean value for the total time consumed for a full FATE was 69.3 s (59.8-78.8) on the Vscan and 63.7s (56.7-70.8) on the Vivid i, with no significant difference among the scanners (P=0.08). CONCLUSION: The Vscan displays image quality interchangeable with larger and more expensive systems. The apparatus is well suited for performing a FATE examination in a 1-day surgery setting and could very well also be applicable in almost any situation involving patients with acute illness.