Robotic versus Freehand Needle Positioning in CT-guided Ablation of Liver Tumors: A Randomized Controlled Trial.

Purpose To compare the accuracy of freehand versus robotic antenna placement in CT-guided microwave ablation (MWA) of liver tumors. Materials and Methods This study was conducted as a prospective single-center nonblinded randomized controlled trial (Netherlands Trial Registry, NTR6023). Eligible study participants had undergone clinically indicated CT-guided MWA of liver tumors and were able to receive a CT contrast agent. Randomization was performed per tumor after identification on contrast material-enhanced CT images. The primary outcome was the number of antenna repositionings, which was compared by using the Mann-Whitney U test. Secondary outcomes were lateral targeting error stratified by in-plane and out-of-plane targets and targeting time. Results Between February 14 and November 12, 2017, 31 participants with a mean age of 63 years (range, 25-88 years) were included: 17 women (mean age, 57 years; range, 25-77 years) and 14 men (mean age, 70 years; range, 52-88 years). The freehand study arm consisted of 19 participants, while the robotic study arm consisted of 18 participants; six participants with multiple tumors were included in both arms. Forty-seven tumors were assessed; five tumors were excluded from the analysis because of technical limitations. In the robotic arm, no antenna repositioning was required. In the freehand arm, a median of one repositioning was required (range, zero to seven repositionings; P < .001). For out-of-plane targets, lateral targeting error was 10.1 mm ± 4.0 and 5.9 mm ± 2.9 (P = .007) for freehand and robotic procedures, respectively, and for in-plane targets, lateral targeting error was 6.2 mm ± 2.7 and 7.7 mm ± 5.9, respectively (P = .51). Mean targeting time was 19 minutes (range, 8-55 minutes) and 36 minutes (range, 3-70 minutes; P = .001) for freehand and robotic procedures, respectively. Conclusion Robotic antenna guidance reduces the need for antenna repositioning in microwave ablation to accurately target liver tumors and increases accuracy for out-of-plane targets. However, targeting time was greater with robotic guidance than with freehand targeting. © RSNA, 2019.

Ventilator-induced pulse pressure variation in neonates.

During positive pressure ventilation, arterial pressure variations, like the pulse pressure variation (PPV), are observed in neonates. However, the frequency of the PPV does not always correspond with the respiratory rate. It is hypothesized that PPV is caused by cardiopulmonary interaction, but that this mismatch is related to the low respiratory rate/heart rate ratio. Therefore, the goal of this study is to investigate the relation between PPV and ventilation in neonates. A prospective observational cross-sectional study was carried out in a third-level neonatal intensive care unit in a university hospital. Neonates on synchronized intermittent mandatory ventilation (SIMV) or high-frequency ventilation (HFV) participated in the study. The arterial blood pressure was continuously monitored in 20 neonates on SIMV and 10 neonates on HFV. In neonates on SIMV the CO2 waveform and neonates on HFV the thorax impedance waveform were continuously monitored and defined as the respiratory signal. Correlation and coherence between the respiratory signal and pulse pressure were determined. The correlation between the respiratory signal and pulse pressure was -0.64 ± 0.18 and 0.55 ± 0.16 and coherence at the respiratory frequency was 0.95 ± 0.11 and 0.76 ± 0.4 for SIMV and HFV, respectively. The arterial pressure variations observed in neonates on SIMV or HFV are related to cardiopulmonary interaction. Despite this relation, it is not likely that PPV will reliably predict fluid responsiveness in neonates due to physiological aliasing.

Dynamic preload indicators decrease when the abdomen is opened.

BACKGROUND: Optimizing cardiac stroke volume during major surgery is of interest to many as a therapeutic target to decrease the incidence of postoperative complications. Because dynamic preload indicators are strongly correlated with stroke volume, it is suggested that these indices can be used for goal directed fluid therapy. However, threshold values of these indicators depend on many factors that are influenced by surgery, including opening of the abdomen. The aim of this study was therefore to assess the effect of opening the abdomen on arterial pressure variations in patients undergoing abdominal surgery. METHODS: Blood pressure and bladder pressure were continuously recorded just before and after opening of the abdomen in patients undergoing elective laparotomy. Based on waveform analysis of the non-invasively derived blood pressure, the stroke volume index, pulse pressure variation (PPV) and stroke volume variation (SVV) were calculated off-line. RESULTS: Thirteen patients were included. After opening the abdomen, PPV and SVV decreased from 11.5 ± 5.8% to 6.4 ± 2.9% (p < 0.005, a relative decrease of 40 ± 19%) and 12.7 ± 6.1% to 4.8 ± 1.6% (p < 0.05, a relative decrease of 53 ± 26%), respectively. Although mean arterial pressure and stroke volume index tended to increase (41 ± 6 versus 45 ± 4 ml/min/m2, p = 0.14 and 41 ± 6 versus 45 ± 4 ml/min/m2, p = 0.05), and heart rate tended to decrease (73 ± 15 versus 68 ± 11 1/min, p = 0.05), no significant change was found. No significant change was found in respiratory parameter (tidal volume, respiratory rate or inspiratory pressure; p = 0.36, 0.34 and 0.17, respectively) or bladder pressure (6.0 ± 3.7 versus 5.6 ± 2.7 mmHg, p = 0.6) either. CONCLUSIONS: Opening of the abdomen decreases PPV and SVV. During goal directed therapy, current thresholds for fluid responsiveness should be changed accordingly.

Mechanical ventilation-induced intrathoracic pressure distribution and heart-lung interactions*.

OBJECTIVE: Mechanical ventilation causes cyclic changes in the heart's preload and afterload, thereby influencing the circulation. However, our understanding of the exact physiology of this cardiopulmonary interaction is limited. We aimed to thoroughly determine airway pressure distribution, how this is influenced by tidal volume and chest compliance, and its interaction with the circulation in humans during mechanical ventilation. DESIGN: Intervention study. SETTING: ICU of a university hospital. PATIENTS: Twenty mechanically ventilated patients following coronary artery bypass grafting surgery. INTERVENTION: Patients were monitored during controlled mechanical ventilation at tidal volumes of 4, 6, 8, and 10 mL/kg with normal and decreased chest compliance (by elastic binding of the thorax). MEASUREMENTS AND MAIN RESULTS: Central venous pressure, airway pressure, pericardial pressure, and pleural pressure; pulse pressure variations, systolic pressure variations, and stroke volume variations; and cardiac output were obtained during controlled mechanical ventilation at tidal volume of 4, 6, 8, and 10 mL/kg with normal and decreased chest compliance. With increasing tidal volume (4, 6, 8, and 10 mL/kg), the change in intrathoracic pressures increased linearly with 0.9 ± 0.2, 0.5 ± 0.3, 0.3 ± 0.1, and 0.3 ± 0.1 mm Hg/mL/kg for airway pressure, pleural pressure, pericardial pressure, and central venous pressure, respectively. At 8 mL/kg, a decrease in chest compliance (from 0.12 ± 0.07 to 0.09 ± 0.03 L/cm H2O) resulted in an increase in change in airway pressure, change in pleural pressure, change in pericardial pressure, and change in central venous pressure of 1.1 ± 0.7, 1.1 ± 0.8, 0.7 ± 0.4, and 0.8 ± 0.4 mm Hg, respectively. Furthermore, increased tidal volume and decreased chest compliance decreased stroke volume and increased arterial pressure variations. Transmural pressure of the superior vena cava decreased during inspiration, whereas the transmural pressure of the right atrium did not change. CONCLUSIONS: Increased tidal volume and decreased chest wall compliance both increase the change in intrathoracic pressures and the value of the dynamic indices during mechanical ventilation. Additionally, the transmural pressure of the vena cava is decreased, whereas the transmural pressure of the right atrium is not changed.

Validation of noninvasive pulse contour cardiac output using finger arterial pressure in cardiac surgery patients requiring fluid therapy.

INTRODUCTION: Nexfin (Edwards Lifesciences, Irvine, CA) allows for noninvasive continuous monitoring of blood pressure (ABPNI) and cardiac output (CONI) by measuring finger arterial pressure (FAP). To evaluate the accuracy of FAP in measuring ABPNI and CONI as well as the adequacy of detecting changes in ABP and CO, we compared FAP to intra-arterially measured blood pressure (ABPIA) and transpulmonary thermodilution(COTD) in post cardiac surgery patients during a fluid challenge (FC). METHODS: Twenty sedated patients post cardiac surgery were included, and 28 FCs were performed. Measurements of ABP and CO were simultaneously collected before and after an FC, and we compared CO and blood pressure. RESULTS: Finger arterial pressure was obtainable in all patients.When comparing ABPNI with ABPIA, bias was2.7 mm Hg (limits of agreement [LOA], ± 22.2), 4.9 mm Hg (LOA, ± 13.6), and 4.2 mm Hg (LOA, ±13.7) for systolic,diastolic, and mean arterial pressure, respectively. Concordance between changes in ABPNI and ABPIA was 100%.Mean bias between CONI and COTD was -0.26 (LOA, ± 2.2), with a percentage error of 38.9%. Concordance between changes in CONI vs COTD and was 100%. CONCLUSION: Finger arterial pressure reliably measures ABP and adequately tracks changes in ABP. Although CONI is not interchangeable with COTD, it follows changes in CO closely.

Non-invasive blood pressure and cardiac index measurements using the Finapres Portapres in an emergency department triage setting.

UNLABELLED: Emergency department (ED) patients are triaged to determine the urgency of care. The Finapres Portapres (FP) measures blood pressure (BP) and cardiac output (CO) non-invasively, and may be of added value in early detection of patients at risk for hemodynamic compromise. OBJECTIVES: Compare non-invasive BP measurements using FP and standard automated sphygmomanometry. Compare FP cardiac index (CI), CO corrected for body surface area, of normotensive patients, to chart-based physician estimate of shock, to discover if there is additional value in CI measurements in triage. METHODS: ED Patients requiring BP measurement in triage were included. Systolic (SBP) and diastolic (DBP) BP were measured using both devices during a two minutes measurement. Two physicians independently judged probability of shock, defined as estimated CI ≤2.5 L min(-1) m(-2), based on chart review, three weeks after ED visit. RESULTS: Of a total of 112 patients 97 patients were included. Pearson's correlation coefficient was 0.50 for SBP, 0.53 for DBP, with a Blant-Altman mean bias of 11.3 (upper limit 65.3, lower limit -42.8) and 7.7 (39.2, -23.7) for SBP and DBP respectively. In normotensive patients, the group with low FP CI measurements had significantly more cases with physician-estimated shock, compared to the normal to high measurements (P = .036). CONCLUSIONS: When used as a triage device in the emergency department setting, non-invasive BP measurements using FP do not correlate well with automated sphygmomanometry. However, this study does indicate that use of the FP device in triage may aid physicians to recognize patients in early phases of shock.