Lars Knudsen

Using Thoracic Ultrasonography to Accurately Assess Pneumothorax Progression During Positive Pressure Ventilation: A Comparison With CT Scanning

BACKGROUND Although thoracic ultrasonography accurately determines the size and extent of occult pneumothoraces (PTXs) in spontaneously breathing patients, there is uncertainty about patients receiving positive pressure ventilation. We compared the lung point (ie, the area where the collapsed lung still adheres to the inside of the chest wall) using the two modalities ultrasonography and CT scanning to determine whether ultrasonography can be used reliably to assess PTX progression in a positive-pressure-ventilated porcine model. METHODS Air was introduced in incremental steps into fi ve hemithoraces in three intubated porcine models. The lung point was identified on ultrasound imaging and referenced against the lateral limit of the intrapleural air space identified on the CT scans. The distance from the sternum to the lung point (S-LP) was measured on the CT scans and correlated to the insufflated air volume. RESULTS The mean total difference between the 131 ultrasound and CT scan lung points was 6.8 mm (SD, 7.1 mm; range, 0.0-29.3 mm). A mixed-model regression analysis showed a linear relationship between the S-LP distances and the PTX volume ( P , .001). CONCLUSIONS In an experimental porcine model, we found a linear relation between the PTX size and the lateral position of the lung point. The accuracy of thoracic ultrasonography for identifying the lung point (and, thus, the PTX extent) was comparable to that of CT imaging. These clinically relevant results suggest that ultrasonography may be safe and accurate in monitoring PTX progression during positive pressure ventilation.

The North Jutland County Diabetic Retinopathy Study. Population characteristics

Background: Several population-based studies have reported blood glucose levels and blood pressure to be risk factors for the development of diabetic retinopathy. These studies were initiated more than two decades ago and may therefore reflect the treatment and population composition of a previous era, suggesting new studies of the present population with diabetes. Aim and methods: This cross-section study included 656 people with type 1 diabetes and 328 with type 2 diabetes. Crude prevalence rates of proliferative diabetic retinopathy, clinically significant macular oedema and several specific retinal lesions were assessed, together with their association to a simplified and internationally approved retinal grading. Results: The point prevalence of proliferative retinopathy was found to be 0.8% and 0.3% for type 1 and type 2 diabetes. Equivalent prevalence rates of clinically significant macular oedema were 7.9% and 12.8%, respectively. The most frequently occurring retinal manifestations increased in number until retinopathy level 3, and then decreased. Conclusion: The point prevalence of proliferative retinopathy is lower than that found in previous studies, whereas it is increased for clinically significant macular oedema. These data suggest different risk factors for these clinical entities.

Monitoring thrombin generation with prothrombin fragment 1.2 assay during cardiopulmonary bypass surgery.

UNLABELLED Despite high plasma levels of heparin during cardiopulmonary bypass surgery, activation of the coagulation system has been reported. We hypothesize that the coagulation system activity most appropriately could be assessed by molecular markers of thrombin generation. The aim of the present study was to describe the changes in thrombin generation during CPB, using prothrombin fragment F1 + 2 (F1.2) as an indicator and evaluate different blood sampling regimens for interpretation of the F1.2 measurements. Twenty patients, operated under extracorporeal circulation with coronary artery bypass grafting (CABG), comprised the study material. The heparin levels were maintained above 2.5 IU/ml throughout the bypass procedure and the functional AT-III level was kept above 0.5 U/ml. Despite of this anticipated inactivation of the coagulation system, the concentrations of F1.2 and FpA increased throughout CPB, particularly after release of the aortic crossclamp. F1.2 and FpA correlated significantly (R = 0.69). No statistically significant correlation was found between F1.2 formation rate and age, bodyweight, baseline ACT, ACT after 200 IU heparin/kg, average heparin concentration during CPB or average AT-III level during CPB. CONCLUSIONS Thrombin formation seems to be a continuous process during CPB despite adequate heparinization. The pattern of thrombin generation can be assessed most appropriately in terms of F1.2 generation rate. Extraordinary high levels of F1.2 were seen after release of the aortic crossclamp, indicating that the periods before and after aortic crossclamping should be evaluated separately.

Quality of cardiopulmonary resuscitation in out-of-hospital cardiac arrest before and after introduction of a mechanical chest compression device, LUCAS-2; a prospective, observational study.

BackgroundMechanical chest compressions have been proposed to provide high-quality cardiopulmonary resuscitation (CPR), but despite the growing use of mechanical chest compression devices, only few studies have addressed their impact on CPR quality. This study aims to evaluate mechanical chest compressions provided by LUCAS-2 (Lund University Cardiac Assist System) compared with manual chest compression in a cohort of out-of-hospital cardiac arrest (OHCA) cases.MethodsIn this prospective study conducted in the Central Denmark Region, Denmark, the emergency medical service attempted resuscitation and reported data on 696 non-traumatic OHCA patients between April 2011 and February 2013. Of these, 155 were treated with LUCAS CPR after an episode with manual CPR. The CPR quality was evaluated using transthoracic impedance measurements collected from the LIFEPAK 12 defibrillator, and the effect was assessed in terms of chest compression rate, no-flow time and no-flow fraction; the fraction of time during resuscitation in which the patient is without spontaneous circulation receiving no chest compression.ResultsThe median total episode duration was 21 minutes, and the episode with LUCAS CPR was significantly longer than the manual CPR episode, 13 minutes vs. 5 minutes, p < 0.001. The no-flow fraction was significantly lower during LUCAS CPR (16%) than during manual CPR (35%); difference 19% (95% CI: 16% to 21%; p < 0.001). No differences were found in pre- and post-shock no-flow time throughout manual CPR and LUCAS CPR.Contrary to the manual CPR, the average compression rate during LUCAS CPR was in conformity with the current Guidelines for Resuscitation, 102/minute vs. 124/minute, p < 0.001.ConclusionMechanical chest compressions provided by the LUCAS device improve CPR quality by significantly reducing the NFF and by improving the quality of chest compression compared with manual CPR during OHCA resuscitation. However, data on end-tidal Co2 and chest compression depth surrogate parameters of CPR quality could not be reported.

Dynamic needle tip positioning - ultrasound guidance for peripheral vascular access. A randomized, controlled and blinded study in phantoms performed by ultrasound novices.

PURPOSE The application of ultrasound-guidance for peripheral venous access is gaining popularity. It is possible to produce a short axis or a long axis sonographic view of the target vessel and apply an out-of-plane or in-plane needle tip approach. Our aim was to present the dynamic needle tip positioning technique and to estimate which approach is the most accurate for inserting the needle tip into the center of the target vessel. MATERIALS AND METHODS Fiftynine novices in ultrasound-guided peripheral vascular access participated. (A) a short axis view combined with an out-of-plane needle tip approach using dynamic needle tip positioning was compared to (B) a long axis view combined with an in-plane needle tip approach to a target vessel embedded in a gelatine phantom. RESULTS The success rate of method (A) was significantly higher than method (B) (97 % versus 81 %). The distance between the center of the target vessel and the final needle tip position was significantly shorter for method (A) compared to method (B). CONCLUSION The combined short axis and out-of-plane technique using dynamic needle tip positioning had a higher success rate and a shorter distance between the center of the target vessel and the needle tip compared to the combined long axis and in-plane technique.

The North Jutland County Diabetic Retinopathy Study (NCDRS). 2 Non-ophthalmic parameters and clinically significant macular oedema.

Background: The influence of non-ophthalmic parameters on the prevalence of clinically significant macular oedema has not been unambiguously established. The present study was initiated with the aim of clarification. Methods: This cross-sectional study comprised 656 type 1 and 328 type 2 diabetic subjects undergoing retinopathy screening in the county of North Jutland. The association between the presence of clinically significant macular oedema and blood pressure, HbA1c, BMI, age, onset of diabetes, duration of diabetes, blood-pressure-reducing medication, lipid-lowering medication, neuropathy and urinary albumin excretion was explored using multiple logistic regression analysis. Results: We found no significant association between the presence of clinically significant macular oedema and any of the examined parameters in type 1 diabetic subjects. In type 2 diabetic subjects, the duration of diabetes, HbA1c, neuropathy and increased urinary albumin excretion was significantly associated with the presence of clinically significant macular oedema. Conclusions: The risk factors for clinically significant macular oedema differ in type 1 and type 2 diabetic subjects and can account only in part for this manifestation.

Earlier reperfusion in patients with ST-elevation Myocardial infarction by use of helicopter

BackgroundIn patients with ST-elevation myocardial infarction (STEMI) reperfusion therapy should be initiated as soon as possible. This study evaluated whether use of a helicopter for transportation of patients is associated with earlier initiation of reperfusion therapy.Material and methodsA prospective study was conducted, including patients with STEMI and symptom duration less than 12 hours, who had primary percutaneous coronary intervention (PPCI) performed at Aarhus University Hospital in Skejby. Patients with a health care system delay (time from emergency call to first coronary intervention) of more than 360 minutes were excluded. The study period ran from 1.1.2011 until 31.12.2011. A Western Denmark Helicopter Emergency Medical Service (HEMS) project was initiated 1.6.2011 for transportation of patients with time-critical illnesses, including STEMI.ResultsThe study population comprised 398 patients, of whom 376 were transported by ambulance Emergency Medical Service (EMS) and 22 by HEMS. Field-triage directly to the PCI-center was used in 338 of patients. The median system delay was 94 minutes among those field-triaged, and 168 minutes among those initially admitted to a local hospital. Patients transported by EMS and field-triaged were stratified into four groups according to transport distance from the scene of event to the PCI-center: ≤25 km., 26–50 km., 51–75 km. and > 75 km. For these groups, the median system delay was 78, 89, 99, and 141 minutes. Among patients transported by HEMS and field-triaged the estimated median transport distance by ground transportation was 115 km, and the observed system delay was 107 minutes. Based on second order polynomial regression, it was estimated that patients with a transport distance of >60 km to the PCI-center may benefit from helicopter transportation, and that transportation by helicopter is associated with a system delay of less than 120 minutes even at a transport distance up to 150 km.ConclusionThe present study indicates that use of a helicopter should be considered for field-triage of patients with STEMI to the PCI-center in case of long transportation. Such a strategy may ensure that patients living up to 150 km. from the PCI-center can be treated within 120 minutes of emergency call.

FLUORESCEIN AND FLUORESCEIN GLUCURONIDE IN PLASMA

Abstract The evaluation of the blood‐ocular barrier for fluorescein requires the measurement of free and unconjugated fluorescein in plasma. This study introduces a new and simple method for the determination of free fluorescein in plasma on the basis of determined total free plasma fluorescense and the free fraction of fluorescence. An excellent good correlation between differential spectrofluorophotometry and this new method is demonstrated. After intravenous administration of sodium fluorescein, the contribution of fluorescein glucuronide to total free plasma fluorescence was evaluated on basis of the areas under the plasma concentration/time curves for fluorescein and fluorescein glucuronide, respectively. After 1 h 8.2% of total free fluorescence in plasma was found to originate from fluorescein glucuronide and after 24 h 18.3% originated from this metabolite. It was concluded that although plasma fluorescein glucuronide measurements are important in the exact evaluation of the blood‐ocular barrier, the contribution of fluorescein glucuronide to vitreous fluorescence after intravenous fluorescein administration seems to be of minor magnitude.

Candidaemia and risk of intraocular infection: a Danish hospital-based cohort study.

Intraocular infection is a feared complication in patients with candidaemia. We therefore assessed the current risk and prognosis in Danish candidaemia patients. Candidaemia patients at a Danish university hospital were identified prospectively during a 10-y period, 1995–2004, and ophthalmologic records were retrieved retrospectively. Among 203 incident cases of candidaemia, 86 (42%) were examined at least once by an ophthalmologist. Nine patients had retinitis and 1 patient had endophthalmitis; eye involvement was bilateral in 8 and monocular in 2 patients. Lesions were generally mild and progression was observed in only 1 patient. Surgical treatment was not indicated and the median duration of systemic antifungal therapy was 19 d. The median survival time was 77 d for candidaemia patients with eye involvement, 480 d in candidaemia patients without such an involvement, and only 9 d in candidaemia patients without an ophthalmologic examination. In conclusion, the cumulative rate of intraocular infection was 11.6%, but we suspect an underestimation due to the circumstances of the eye examinations and the rapid death of many patients. We continue to recommend eye examinations for candidaemia patients, but timing seems not to be critical if overt signs of infection are absent, thereby facilitating the use of improved diagnostic methods.

Long‐term kinetic vitreous fluorophotometry

Abstract Fluorophotometric measurements of vitreous and plasma fluorescence were performed in 14 normal subjects up to 24 h after injection of a single intravenous dose of sodium fluorescein. The data were subjected to a kinetic two‐compartmental analysis, including the determination of the transfer rate constants between the central and the peripheral compartment (K12 and K21) as well as between the central and the vitreous compartment (Kin and Kout). In the central compartment (plasma) a mean terminal disposition rate constant (β) of free fluorescein of 0.23 h‐1 was found, corresponding to a half‐life of 3.01 h. The vitreous fluorescence reached a maximum 2–5 h after the injection and then declined monoexponentially and very slowly (t1/2 = 9.6 h). The rate constant of permeation into the eye (Kin) was found to be 0.66 h‐1, while the rate constant of elimination of fluorescein from the vitreous was 0.072 h‐1 (Kout). Kin was found to be significantly higher than K12, presumably indicating an active transport mechanism for fluorescein located at the blood‐ocular barrier. Kout was significantly lower than K21, reflecting a slow vitreous elimination of fluorescein. A permeability index defined as the percentage ratio between the areas under the vitreous and the plasma concentration curves was found to be 3.5%, illustrating the poor penetration of fluorescein into the vitrous. Kinetic long‐term fluorophotometry appears to be a promising new tool in the study of the blood‐ocular barrier.