Rafael Rehwald

Systemic air embolism causing acute stroke and myocardial infarction after percutaneous transthoracic lung biopsy - a case report.

The air embolism in this case was likely to have been caused by positioning the patient in a prone position, which was associated with the lesion to be biopsied being at a maximum height over the left atrium. Due to the resulting negative pressure, air entered through a fistula that formed between the airspace and the pulmonary vein. The air could have been trapped in the left atrium by positioning the patient in left lateral position. The event itself could have been prevented by positioning the patient in an ipsilateral dependent position during the biopsy. In addition to hyperbaric oxygen therapy, the preferred treatment options are positioning maneuvers, administration of pure oxygen, and heparinization.

Measures to Prevent Air Embolism in Transthoracic Biopsy of the Lung

OBJECTIVE Systemic air embolism (AE) is a rare but feared complication of transthoracic biopsy with potentially fatal consequences. The aim of the study was to assess the effect of patient positioning during transthoracic biopsy on preventing systemic AE. MATERIALS AND METHODS We compared a historical control group of 610 patients (group 1) who underwent transthoracic biopsy before the implementation of measures to prevent systemic AE during transthoracic biopsy and a group of 1268 patients (group 2) who underwent biopsy after the measures were implemented. The patients in group 2 were placed in the ipsilateral-dependent position so that the lesion being biopsied was located below the level of the left atrium. RESULTS The rate of systemic AE was reduced from 3.77% to 0.16% (odds ratio [OR], 0.040; 95% CI, 0.010-0.177; p < 0.001). Logistic regression analyses identified needle penetration depth, prone position of the patient during biopsy, location above the level of the left atrium, needle path through ventilated lung, and intubation anesthesia as independent risk factors for systemic AE (p < 0.05). Propensity score-matched analyses identified the number of biopsy samples obtained as an additional risk factor (p = 0.003). The rate of pneumothorax was reduced from 15.41% in group 1 to 5.99% in group 2 (OR, 0.374; 95% CI, 0.307-0.546; p < 0.001). CONCLUSION Performing transthoracic biopsy with the patient in an ipsilateral-dependent position so that the lesion is located below the level of the left atrium is an effective measure for preventing systemic AE. Needle path through ventilated lung and intubation anesthesia should be avoided whenever possible.

Residual Thromboembolic Material in Cerebral Arteries after Endovascular Stroke Therapy Can Be Identified by Dual-Energy CT

BACKGROUND AND PURPOSE: Dual-energy CT features the opportunity to differentiate among up to 3 different materials because the absorption of x-rays depends on the applied tube voltage and the atomic number of the material. For example, it is possible to distinguish between blood-brain barrier disruption and an intracerebral hemorrhage following treatment for a stroke. The aim of this study was to evaluate whether dual-energy CT is capable of distinguishing intra-arterial contrast agent from residually clotted vessels immediately after endovascular stroke therapy. MATERIALS AND METHODS: Sixteen patients (9 women, 7 men; mean age, 63.6 ± 13.09 years) were examined. Measurements were made on the postinterventional dual-energy CT virtual noncontrast, iodine map, and “weighted” brain window (weighted dual-energy) series. Postinterventional conventional angiography was used as the criterion standard method. RESULTS: A residual clot was found in 10 patients. On the virtual noncontrast series, the Hounsfield attenuation of the clotted arteries was higher than that in the corresponding perfused contralateral arteries (53.72 ± 9.42 HU versus 41.64 ± 7.87 HU; P < .05). The latter had higher absorption values on the weighted dual-energy series than on the virtual noncontrast series (49.37 ± 7.44 HU versus 41.64 ± 7.87 HU; P < .05). The sensitivity for the detection of a residual clot was 90%; the specificity was 83.3%, and the accuracy was 87.5%. Interrater agreement was good (κ = 0.733). CONCLUSIONS: Dual-energy CT may be valuable in the detection of clot persistence or early re-thrombosis without the necessity of additional contrast administration. However, its relevance for the prediction of outcomes remains to be determined in further studies.

Prognostic Significance of Hepatic Arterial Collaterals in Liver Transplant Recipients with Biliary Strictures.

The aim of this study was to determine the prevalence of hepatic artery stenosis (HAS) and the prognostic implications of hepatic arterial collaterals in liver transplant (LT) recipients with biliary strictures.

Reply to “Prevention of Air Embolism During Transthoracic Biopsy of the Lung”

Reply to “Prevention of Air Embolism During Transthoracic Biopsy of the Lung” It was with great interest that we read the remarks by Fintelmann et al. [1] concerning our analysis [2]. We fully support the measure proposed by our colleagues regarding closing the introducer needle. However, an open needle could not be identified as a risk factor for a systemic air embolism (AE) in our analysis because we also always close the needle [3]. We recommend closing the needle completely, not just with a saline lock, because the saline can be drawn in as well if the tip of the needle is located in a pulmonary vein above the atrial level. Of course, the route through the needle is not the only possible way for air to enter a pulmonary vein and the left atrium during transthoracic lung biopsy [2]. We do not have a high incidence of systemic AE. In fact, no instance of clinically manifested systemic AE has been noted since 2010. Since that time, we have found only two very small intracardiac air accumulations, although we performed a systematic postinterventional search of the entire chest with the use of low-dose CT, and we described the reasons for this reduction in our article [2]. We also found no instance of systemic AE until 2007. The reason is simple: to this day, we, like our colleagues, have not been looking for them. Searching does not cost much and has benefits because inadequate repositioning of the patient after biopsy can lead to the release of trapped air [4]. To avoid this complication, we recommend suggestions in two excellent articles by Kok et al. [5] and Rott and Boecker [6]. Naturally, before repositioning, air that has penetrated the vascular system and been trapped there must be searched for, and we urgently recommend that this be done. We believe that a sensitivity and specificity of 100% will never be achievable, even if our colleagues report such values. In most institutions, a pathologist is not present during the procedure, and the specimens have to be taken to the pathology department after the biopsy. The specimens will therefore sometimes have too little material, unsatisfactory material, or both. Expert opinions about rare events can be helpful, but vanity is not. Since the publication of our article [2], more cases of systemic AEs in patients undergoing biopsy of the lung have been published, some of which resulted in serious clinical consequences for the patients. We all need to make an attempt to understand why this has happened and continues to happen: because of an injury to a pulmonary vein and unfavorable local pressure conditions [2], which frequently occur when the patient is placed in a prone position. Retrospective analyses are only one level above expert opinions, but they provide the best information we have at this time. Until we have better information, biopsies should be performed with the patient in the ipsilateral dependent position [6], to ensure that the lesions to be biopsied are located below the atrial level. This means that the prone patient position usually is not suitable during biopsy of posterior lesions. Endotracheal anesthesia and a needle path through the ventilated lung should be avoided, if possible [2]. The number of biopsy samples should be limited, and the coaxial needle should be closed securely at all times. Rafael Rehwald University College London, London, United Kingdom

Factors influencing intracranial vessel densities on unenhanced computed tomography: differences between hemispheres.

The aim was to identify the factors influencing intracranial vessel density (VD). The Hounsfield units of the dense vessel and the contralateral side were measured in 34 patients with arterial clots, 20 with venous clots, and 196 without clots and correlated with skull thickness, density and dimensions, gender, age, red blood cell count (RBC), hemoglobin (HB), hematocrit (HT), creatinine, and sodium. Positive correlations were found between VD and HT, RBC, HB, creatinine, and occipital bone density. Density differences between the right and left intracranial vessels were more accurate (sensitivity/specificity/accuracy=0.91/0.93/0.93 and 0.75/0.87/0.85, respectively) for detecting clots than VD alone. HT, RBC, and HB are the main factors that correlate with VD.

Retrospective angiographic study to determine the effect of atherosclerotic stenoses of upstream arteries on the degree of atherosclerosis in distal vascular territories.

Objective Experimental coarctation of the aorta prevents the development of downstream atherosclerosis. The aim of this study was to find out whether or not atherosclerotic stenoses protect distal vascular territories from developing atherosclerosis in humans. Design and setting A total of 2125 vascular segments from angiographies of 101 patients were evaluated by calculating the maximum degree of stenosis (NASCET criteria), the degree of calcification, the degree of collaterals and the Friesinger score. Results Stenosis ≥30–49% was found in 685 vascular segments (32.2%), ≥50–69% in 490 (23.1%), ≥70–89% in 373 (17.6%) and ≥90% in 265 (12.5%). If a stenosis of at least ≥70–89% was present in the common iliac, the external iliac or the common femoral artery, the degrees of stenosis distal to it were lower than those on the contralateral side (19.8±22.3% (CI 11.7 to 28.0) vs 25.2±20.7% (CI 21.2 to 29.1); Friesinger scores 1.1±1.2 (CI 0.6 to 1.5) vs 1.4±1.1 (CI 1.2 to 1.6); degrees of calcification 0.8±1.0 (CI 0.4 to 1.1) vs 1.2±1.1 (CI 1.2 to 1.6); p<0.05 each). This effect depended on the degree of proximal stenosis, but not on collaterals, and was most pronounced distal to stenoses of the common iliac, the superficial femoral and the popliteal artery. In regression models, stenoses of the pelvic arteries were shown to be an independent protective factor for the distal vascular territories. Conclusions Atherosclerotic stenoses seem to protect distal vascular territories from developing atherosclerosis. The underlying pathophysiological mechanism of this phenomenon remains to be determined. It could be based on pulse pressure reduction.