Limitations of the ARDS criteria during high-flow oxygen or non-invasive ventilation: evidence from critically ill COVID-19 patients.

BACKGROUND: The ratio of partial pressure of arterial oxygen to inspired oxygen fraction (PaO2/FIO2) during invasive mechanical ventilation (MV) is used as criteria to grade the severity of respiratory failure in acute respiratory distress syndrome (ARDS). During the SARS-CoV2 pandemic, the use of PaO2/FIO2 ratio has been increasingly used in non-invasive respiratory support such as high-flow nasal cannula (HFNC) and non-invasive ventilation (NIV). The grading of hypoxemia in non-invasively ventilated patients is uncertain. The main hypothesis, investigated in this study, was that the PaO2/FIO2 ratio does not change when switching between MV, NIV and HFNC. METHODS: We investigated respiratory function in critically ill patients with COVID-19 included in a single-center prospective observational study of patients admitted to the intensive care unit (ICU) at Uppsala University Hospital in Sweden. In a steady state condition, the PaO2/FIO2 ratio was recorded before and after any change between two of the studied respiratory support techniques (i.e., HFNC, NIV and MV). RESULTS: A total of 148 patients were included in the present analysis. We find that any change in respiratory support from or to HFNC caused a significant change in PaO2/FIO2 ratio. Changes in respiratory support between NIV and MV did not show consistent change in PaO2/FIO2 ratio. In patients classified as mild to moderate ARDS during MV, the change from HFNC to MV showed a variable increase in PaO2/FIO2 ratio ranging between 52 and 140 mmHg (median of 127 mmHg). This made prediction of ARDS severity during MV from the apparent ARDS grade during HFNC impossible. CONCLUSIONS: HFNC is associated with lower PaO2/FIO2 ratio than either NIV or MV in the same patient, while NIV and MV provided similar PaO2/FIO2 and thus ARDS grade by Berlin definition. The large variation of PaO2/FIO2 ratio indicates that great caution should be used when estimating ARDS grade as a measure of pulmonary damage during HFNC.

Human brain MR spectroscopy thermometry using metabolite aqueous-solution calibrations.

PURPOSE: To estimate absolute brain temperature using proton MR spectroscopy ((1)H-MRS) and mean brain-body temperature difference of healthy human volunteers. MATERIALS AND METHODS: Chemical shift difference between temperature-dependent water spectral line position and temperature-stable metabolite spectral reference was used for the estimations of absolute brain temperature. Temperature calibrations constants were obtained from the spectra of the N-acetyl aspartate (NAA line at approximately 2.0 ppm), glycero-phosphocholine (GPC line at approximately 3.2 ppm), and creatine (Cr line at approximately 3.0 ppm) aqueous solutions with pH values within physiologically pertinent ranges. Single-voxel PRESS sequence (TR/TE 2000/80 ms) was used for this purpose. Brain temperature was determined by averaging the temperatures computed from water-Cho, water-Cr, and water-NAA chemical shift differences. RESULTS: The mean brain temperature of 18 healthy volunteers was 38.1 +/- 0.4 degrees C and mean brain-body (rectal) temperature difference was 1.3 +/- 0.4 degrees C. CONCLUSION: Improved accuracy of the temperature constants and averaging the temperatures computed from water-Cho, water-Cr, and water-NAA chemical shift differences increased the reliability of the brain temperature estimations.

Bilateral forearm intravenous regional anesthesia with prilocaine for botulinum toxin treatment of palmar hyperhidrosis.

BACKGROUND: Treatment of palmar hyperhidrosis with botulinum toxin (BTX) requires effective anesthesia, but previous methods have not provided enough pain relief or have resulted in a prolonged impaired hand function. OBJECTIVE: This is a study of bilateral forearm intravenous regional anesthesia using prilocaine for BTX treatment of palmar hyperhidrosis. METHODS: In all, 166 patients (100 female and 66 male) were treated bilaterally with intracutaneous BTX type A injections using intravenous regional anesthesia with prilocaine (5 mg/mL). In a subgroup of patients, forearm nerves were studied with neurophysiologic methods and blood concentrations of prilocaine were measured. Pain evaluation with a visual analog scale was accompanied with a questionnaire about the treatment. RESULTS: In all, 95% of the patients answering the questionnaire (response rate 89%) were satisfied with the anesthetic effect. No serious adverse events occurred. There was a fast recovery of motor function (in median 6 minutes) and sensory function (in median 20 minutes). No subclinical signs of sensory nerve damage were found. LIMITATIONS: Recall and reporting bias are potential sources of limitations in this study. CONCLUSION: Bilateral forearm intravenous regional anesthesia provides an effective and well-tolerated anesthesia during BTX treatment of palmar hyperhidrosis.

Gender differences in utilization of coronary angiography and angiographic findings after out-of-hospital cardiac arrest: A registry study.

INTRODUCTION: We investigated the impact of gender in performance and findings of early coronary angiography (CAG) and percutaneous coronary intervention (PCI), comorbidity and outcome in a large population of out-of-hospital cardiac arrest (OHCA) patients with an initially shockable rhythm. METHODS: Retrospective cohort study. Data retrieved 2008-2013 from the Swedish Register for Cardio-Pulmonary Resuscitation, Swedeheart Registry and National Patient Register. RESULTS: We identified 1498 patients of whom 78% were men. Men and women had the same pathology on the first registered electrocardiogram (ECG): 30% vs. 29% had ST-elevation and 10% vs. 9% had left bundle branch block (LBBB) (P = 0.97). Proportions of performed CAG did not differ between genders. Among patients without ST-elevation/LBBB men more often had at least one significant stenosis, 78% vs. 54% (P = 0.001), more multi-vessel disease (P = 0.01), had normal coronary angiography less often, 22% vs. 46% and PCI more often, 59% vs. 42% (P = 0.03). Among patients without ST-elevation/LBBB on the initial ECG, more men had previously known ischaemic heart disease, 27% vs. 19% (P = 0.02) and a presumed cardiac origin of the cardiac arrest, 86% vs. 72% (P < 0.001). Multivariable analysis showed no association between gender and evaluation by early CAG. In men and women, 1-year survival was 56% vs. 50% (P = 0.22) in patients with ST-elevation/LBBB and 48% vs. 51% (P = 0.50) in patients without. CONCLUSION: Despite no gender differences in ECG findings indicating an early CAG, men had more severe coronary artery disease while women more frequently had normal coronary angiography. However, this did not influence 1-year survival.

Phase-difference and spectroscopic imaging for monitoring of human brain temperature during cooling.

Decrease of the human brain temperature was induced by intranasal cooling. The main purpose of this study was to compare the two magnetic resonance methods for monitoring brain temperature changes during cooling: phase-difference and magnetic resonance spectroscopic imaging (MRSI) with high spatial resolution. Ten healthy volunteers were measured. Selective brain cooling was performed through nasal cavities using saline-cooled balloon catheters. MRSI was based on a radiofrequency spoiled gradient echo sequence. The spectral information was encoded by incrementing the echo time of the subsequent eight image records. Reconstructed voxel size was 1×1×5 mm(3). Relative brain temperature was computed from the positions of water spectral lines. Phase maps were obtained from the first image record of the MRSI sequence. Mild hypothermia was achieved in 15-20 min. Mean brain temperature reduction varied in the interval <-3.0; -0.6>°C and <-2.7; -0.7>°C as measured by the MRSI and phase-difference methods, respectively. Very good correlation was found in all locations between the temperatures measured by both techniques except in the frontal lobe. Measurements in the transversal slices were more robust to the movement artifacts than those in the sagittal planes. Good agreement was found between the MRSI and phase-difference techniques.

Noninvasive monitoring of brain temperature during mild hypothermia.

The main purpose of this study was to verify the feasibility of brain temperature mapping with high-spatial- and reduced-spectral-resolution magnetic resonance spectroscopic imaging (MRSI). A secondary goal was to determine the temperature coefficient of water chemical shift in the brain with and without internal spectral reference. The accuracy of the proposed MRSI method was verified using a water and vegetable oil phantom. Selective decrease of the brain temperature of pigs was induced by intranasal cooling. Temperature reductions between 2 degrees C and 4 degrees C were achieved within 20 min. The relative changes in temperature during the cooling process were monitored using MRSI. The reference temperature was measured with MR-compatible fiber-optic probes. Single-voxel (1)H MRS was used for measurement of absolute brain temperature at baseline and at the end of cooling. The temperature coefficient of the water chemical shift of brain tissue measured by MRSI without internal reference was -0.0192+/-0.0019 ppm/degrees C. The temperature coefficients of the water chemical shift relative to N-acetylaspartate, choline-containing compounds and creatine were -0.0096+/-0.0009, -0.0083+/-0.0007 and -0.0091+/-0.0011 ppm/degrees C, respectively. The results of this study indicate that MRSI with high spatial and reduced spectral resolutions is a reliable tool for monitoring long-term temperature changes in the brain.

Assessment of intravascular volume by transthoracic echocardiography during therapeutic hypothermia and rewarming in cardiac arrest survivors.

AIM: To study haemodynamic effects and changes in intravascular volume during hypothermia treatment, induced by ice-cold fluids and maintained by ice-packs followed by rewarming in patients after resuscitation from cardiac arrest. MATERIALS AND METHODS: In 24 patients following successful restoration of spontaneous circulation (ROSC), hypothermia was induced with infusion of 4 degrees C normal saline and maintained with ice-packs for 26 h after ROSC. This was followed by passive rewarming. Transthoracic echocardiography was performed at 12, 24 and 48 h after ROSC to evaluate ejection fraction and intravascular volume status. Central venous pressure (CVP), central venous oxygen saturation (ScvO(2)) and serum lactate were measured. Fluid balance was calculated. RESULTS: Twelve hours after ROSC, two separate raters independently estimated that 10 and 13 out of 23 patients had a decreased intravascular volume using transthoracic echocardiography. After 24 and 48 h this number had increased further to 14 and 13 out of 19 patients and 13 and 12 out of 21 patients. Calculated fluid balance was positive (4000 ml the day 1 and 2500 ml day 2). There was no difference in ejection fraction between the recording time points. Serum lactate and ScvO(2) were in the normal range when echocardiography exams were performed. CVP did not alter over time. CONCLUSIONS: Our results support the hypothesis that inducing hypothermia following cardiac arrest, using cold intravenous fluid infusion does not cause serious haemodynamic side effects. Serial transthoracic echocardiographic estimation of intravascular volume suggests that many patients are hypovolaemic during therapeutic hypothermia and rewarming in spite of a positive fluid balance.