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1.
Schummer W  Schummer C  Bredle D  Fröber R 《Anesthesia and analgesia》2004,99(6):1625-9, table of contents
The anterior jugular venous system, with its interconnections to the subclavian and deep jugular veins, provides a collateral venous network across the midline of the neck area, which is especially important in unilateral occlusion of an innominate vein. We illustrate the variability of this system and its clinical impact on catheterization by three cases of landmark-guided central venous cannulation. Case 1: Cannulation of the left internal jugular vein with a central venous catheter and of the left innominate vein (LIV) with a pulmonary artery catheter resulted in correctly positioned catheter tips. However, these catheters were actually not placed in the innominate vein but coursed through the jugular venous arch. Case 2: Cannulation of the left subclavian vein was complicated by resistance of guidewire advancement at 13 cm. Occlusion of the LIV and enlargement of the jugular venous arch were present. Case 3: Insertion of a pulmonary artery catheter and a central venous catheter through the LIV. The pulmonary artery catheter was correctly placed. The tip of the central venous catheter was mistakenly positioned in the left anterior jugular vein. We describe the normal anatomy of the anterior jugular venous system and its role as a major collateral. Correct placement of central venous catheters may be possible via the anterior jugular venous system. Conversely, central venous catheters malpositioned in the anterior jugular vein can increase the risk for complications and should be removed.  相似文献   

2.
目的 探讨应用超声引导定位在经锁骨下静脉人路置入植入式输液港的效果.方法 选择乳腺癌患者60例,年龄28~63岁,体重41~70 kg,身高150~168 cm,ASA Ⅰ或Ⅱ级,拟经锁骨下静脉穿刺置入植入式输液港行长期输液及化疗,输液港导管尖端位置应在上腔静脉和右心房交界处.随机分为2组(n=30):对照组(C组)经锁骨下静脉穿刺,采用脉冲注射冰盐水实验的方法引导定位植入式输液港导管尖端位置.超声组(U组)经锁骨下静脉穿刺,采用超声引导定位植入式输液港导管尖端位置.所有患者术后均经过X线摄片进行导管定位.计算两组患者首次置入成功率.结果 U组患者术后X线摄片显示输液港导管尖端均在上腔静脉和右心房交界处,未发生导管偏离进入颈内静脉的现象,首次置入成功率100%.C组术后X线摄片显示有6例患者的输液港导管发生了偏离,进入颈内静脉,需回手术室在超声引导定位下重新穿刺置管,首次置入成功率80%.U组首次置入成功率高于C组(P<0.05).结论 超声引导定位是经锁骨下静脉正确放置植入式输液港的有效手段.  相似文献   

3.
目的 探讨应用超声引导定位在经锁骨下静脉人路置入植入式输液港的效果.方法 选择乳腺癌患者60例,年龄28~63岁,体重41~70 kg,身高150~168 cm,ASA Ⅰ或Ⅱ级,拟经锁骨下静脉穿刺置入植入式输液港行长期输液及化疗,输液港导管尖端位置应在上腔静脉和右心房交界处.随机分为2组(n=30):对照组(C组)经锁骨下静脉穿刺,采用脉冲注射冰盐水实验的方法引导定位植入式输液港导管尖端位置.超声组(U组)经锁骨下静脉穿刺,采用超声引导定位植入式输液港导管尖端位置.所有患者术后均经过X线摄片进行导管定位.计算两组患者首次置入成功率.结果 U组患者术后X线摄片显示输液港导管尖端均在上腔静脉和右心房交界处,未发生导管偏离进入颈内静脉的现象,首次置入成功率100%.C组术后X线摄片显示有6例患者的输液港导管发生了偏离,进入颈内静脉,需回手术室在超声引导定位下重新穿刺置管,首次置入成功率80%.U组首次置入成功率高于C组(P<0.05).结论 超声引导定位是经锁骨下静脉正确放置植入式输液港的有效手段.  相似文献   

4.
目的 探讨应用超声引导定位在经锁骨下静脉人路置入植入式输液港的效果.方法 选择乳腺癌患者60例,年龄28~63岁,体重41~70 kg,身高150~168 cm,ASA Ⅰ或Ⅱ级,拟经锁骨下静脉穿刺置入植入式输液港行长期输液及化疗,输液港导管尖端位置应在上腔静脉和右心房交界处.随机分为2组(n=30):对照组(C组)经锁骨下静脉穿刺,采用脉冲注射冰盐水实验的方法引导定位植入式输液港导管尖端位置.超声组(U组)经锁骨下静脉穿刺,采用超声引导定位植入式输液港导管尖端位置.所有患者术后均经过X线摄片进行导管定位.计算两组患者首次置入成功率.结果 U组患者术后X线摄片显示输液港导管尖端均在上腔静脉和右心房交界处,未发生导管偏离进入颈内静脉的现象,首次置入成功率100%.C组术后X线摄片显示有6例患者的输液港导管发生了偏离,进入颈内静脉,需回手术室在超声引导定位下重新穿刺置管,首次置入成功率80%.U组首次置入成功率高于C组(P<0.05).结论 超声引导定位是经锁骨下静脉正确放置植入式输液港的有效手段.  相似文献   

5.
目的 观察四种不同带涤纶套中央静脉导管置入方法并行临床分析.方法 132例患者行带涤纶套中央静脉导管置入术,分为A组(36例)经撕脱鞘置入涤纶套中心静脉导管;B组(36例)颈外静脉切开置入导管;C组(32例)通过引导钢丝并逐层扩张后直接置入导管;D组(28例)采用颈内静脉切开置入导管.结果 A、B、C、D四组透析前后肌酐、尿素氮水平变化存在统计学差异,且尿素清除指数均达标,A、B、D三组透析中血流量、回血静脉压、尿素清除指数以及导管留存时间相关指标比较无统计学差异.A、C组中上述指标比较均存在统计学差异,与未非随机分组相关.四组手术后未出现大出血及感染相关并发症,B、C两组各出现1例导管异位情况.结论 带涤纶套中央静脉导管置入方法推荐首选经典撕脱鞘置管,该方法安全成功率高,术后并发症少.其次是颈内静脉切开置管,通过引导钢丝逐层扩张后置管适用于皮下组织疏松、脂肪层少的患者.而颈内静脉切开方法置管是在没有超声学指引下临床穿刺失败后的补救方法,但该方法技术要求高,手术风险大,故临床不作为首选.  相似文献   

6.
Internal jugular vein cannulation has become a routine and clinically important aspect of medical care in hemodialysis patients. Mismanagement in the location of a central venous catheter may occur in up to 20% of cases. The aim of the study was to evaluate the utility of endocavitary electrocardiography in right internal jugu-lar vein placement of central venous catheters. We examined 327 central venous catheterizations performed in two Dialysis Units; all catheters were positioned using intra-atrial ECG monitoring by guide-wire and after, by catheter filled with NaCl solution. EC-ECG via guide-wire was successful on 321 occasions (98.1%). Correct placement of the catheter was confirmed by EC-ECG via catheter in each case, and by plain chest-X-ray only in the first hundred cases. In 314 patients (98.1%), insertion of the catheter was successful at the first attempt. In 6 catheterizations, no atrial trace was obtained due to atrial fibrillation in 4 cases, and in 2 cases technical error and guide-wire looping into a right jugular vein. Complications as a direct result of guide-wire or catheter placement were not observed. In our opinion this method can be used safely and makes radiological control usually unnecessary. (The Journal of Vascular Access 2001; 2: 45-50).  相似文献   

7.
Purpose: The aim of this study was to determine in a pediatric population whether a routine chest x-ray after central venous access is necessary when the central venous catheter is placed with intraoperative fluoroscopy.Methods: This was a retrospective review of the charts of all patients at Children’s Hospital in Denver, Colorado who underwent subclavian or internal jugular central venous catheter placement from January 1, 1998 through December 31, 2001. Age, sex, primary reason for access, access site, number of venipuncture attempts, type of catheter, intraoperative fluoroscopy results, chest x-ray results, location of the tip of the catheter, and complications were analyzed.Results: There were 1,039 central venous catheters placed in 824 patients, 92.6% in the subclavian vein and 7.4% in the internal jugular vein. There were 604 (58.1%) children who had both fluoroscopy and a postprocedure chest x-ray, there were 308 (29.6%) who had only fluoroscopy, there were 117 (11.3%) who had only a postprocedure chest x-ray, and there were 10 (1.0%) who had neither fluoroscopy nor chest x-ray. On completion of the procedure, there were 12 (1.1%) children with misplaced central venous catheters, only 1 (0.1%) when intraoperative fluoroscopy was used. There were 17 (1.6%) complications; 9 (0.9%) were pulmonary (pneumothorax, hemothorax, or an effusion). All children with pulmonary complications experienced clinical signs and symptoms suggestive of the complication after their central venous catheter insertion but before their postprocedure chest x-ray.Conclusions: The number of complications encountered in children who had central venous access of the subclavian vein or internal jugular central vein with intraoperative fluoroscopy was infrequent, the number of misplaced catheters was minimized with intraoperative fluoroscopy, and all children with pulmonary complications showed clinical signs suggestive of pulmonary complications before postoperative chest x-ray. Therefore, children who have had central venous access of the subclavian and internal jugular vein with intraoperative fluoroscopy do not appear to require a routine chest x-ray after catheter placement unless clinical suspicion of a complication exists.  相似文献   

8.
Complications in the placement of central venous catheter (CVC) may occur in up to 20% of cases. The catheter can be misplaced in the contralateral brachiocephalic vein, the ipsi or controlateral internal jugular vein, and usually a chest X-ray is necessary to evaluate its location. We believe that the best technique, first described by Serafini et al, to establish the position of a CVC is the endocavitary electrocardiography (EC-ECG) and its employment is recommended in all uraemic patients requiring haemodialysis. This technique uses the tip of the CVC as reference lead in a standard electrocardiograph. The best use of this technique has been obtained by echotomographic visualization of the internal jugular vein executed just before transcutaneous puncture of the vessel. From 1991 to December 1999 we have successfully applied this technique in CVC placement in 612 patients requiring haemodialysis. In our opinion, this method is a safe and simple technique that avoids the need for thoracic X-ray controls and time lost waiting for radiographs that prolong the start of the haemodialysis session. According to our experience, we believe that the EC-ECG technique is a method in compliance with Food and Drug Administration guidelines regarding catheter tip location in uraemic patients.  相似文献   

9.
For successful catheter placement, central venous cannulation (CVC) through internal jugular vein and subclavian vein has been recommended in both adult and pediatric patients. But it carries a risk of serious complications, such as pneumothorax, carotid, or subclavian artery puncture, which can be life-threatening, particularly in critically ill children. So a prospective study was carried out to determine the success rate of correct catheter tip placement during CVC through antecubital veins in pediatric neurosurgical patients. A total of 200 pediatric patients (age 1-15 years) of either sex were studied. Basilic or cephalic veins of either arm were selected. All the patients were cannulated in the operation room under general anesthesia. Single lumen, proper size catheters (with stillete) were used for cannulation. The catheter was inserted in supine position with the arm abducted at right angle to the body and neck turned ipsilaterally. The length of insertion was determined from cubital fossa to the right second intercostal space. The exact position of the tip of the catheter was confirmed radiologically in ICU. Correct catheter tip placement was achieved in 98 (49%) patients. Multivariate logistic regression analysis of data shows that there was no statistically significant difference among correct and incorrect catheter tip placement in relation to factors including sex, side of cannulation (left or right), and type of vein (basilic or cephalic). The analysis of correct catheter tip placement in relation to age showed that the highest success rate was achieved in children of age group 6 to 10 years (60.2%) followed by 30.6% in the 11 to 15 year group. The lowest success rate of tip placement of only 9.2% was observed in younger children of age 1 to 5 years, which is statistically significant (P = 0.001). Of 102 incorrect placements reported, 37% were in 1 to 5 year age group versus 9.2% correct tip placements. The most common unsatisfactory placements were either in the ipsilateral internal jugular vein (N = 38, 37.2%) or in the ipsilateral subclavian vein (N = 27, 26.4%). In 10 patients the catheter crossed over to the opposite subclavian vein, in 16 patients the catheter tips were found in the axillary vein, and in 10 patients each the catheter tip was observed in right atrium and right ventricle. No major complication during and following CVC was observed. To conclude, CVC using single orifice catheter through arm veins in pediatric patients is easy to perform, but the proper catheter tip placement is highly unreliable, particularly in younger children 1 to 5 years of age.  相似文献   

10.
The NKF-DOQI guidelines recommend performing chest-X-ray(CXR) after subclavian and internal jugular vein insertion prior to catheter use. This is to exclude complications such as a pneumothorax before starting hemodialysis. Indication of a central venous dialysis catheter was based on the historic use of the subclavian vein for placement of these catheters and upon the reported incidence of pneumothorax after this approach of between 1% to 12.4%. In contrast, the incidence of these complications using the internal jugular vein (IJV) is much lower (< 1%). We report our experience in ultrasound-guided cannulation of the right IJV for dialysis vascular access in 527 uremic patients and central catheter placement by endocavitary electrocardiography (EC-ECG). Fluoroscopy was not utilized. In the first hundred cases, all patients underwent CXR. Subsequently, because of total absence of complications and catheter tip malpositioning, the CXR control was carried out only in selected cases (repeated cannulation of the jugular vein or absence of P wave). We believe that only in selected cases should a pCXR be performed before starting hemodialysis sessions, and that our method using the right IJV, ultrasound-guided puncture of the vessel, and catheter placement by EC-ECG is a safe and simple technique that avoids the need for CXR control.  相似文献   

11.
Mismanagement in the placement of central venous catheter (CVC)may occur in up to 20% of cases. The catheter can be inadvertentlyplaced in the contralateral brachiocephalic vein, the ipsi orcontralateral internal jugular vein, and usually a thoracicradiograph is necessary to evaluate its location. We proposea technique first described by Serafini et al. to establishthe position of a CVC by endocavitary electrocardiography (EC-ECG)and its employment in a large number of uraemic patients requiringhaemodialysis. This technique uses the tip of the CVC as referencelead in a standard electrocardiograph. The best employment ofthis technique has been obtained by echotomographic visualizationof the internal jugular vein executed just before transcutaneouspuncture of the vessel. For 13 months we have successfully appliedthis technique in CVC placement in 81 patients requiring haemodialysis.In our opinion this method is a safe and simple technique thatavoids the need for thoracic radiographs and time lost waitingfor radiographs that prolong the start of the haemodialysissession. According to our experience, we confirm that the EC-ECGtechnique provides a method for ensuring compliance with Foodand Drug Administration guidelines regarding catheter tip locationin uraemic patients.  相似文献   

12.
Mismanagement in the placement of central venous catheter (CVC)may occur in up to 20% of cases. The catheter can be inadvertentlyplaced in the contralateral brachiocephalic vein, the ipsi orcontralateral internal jugular vein, and usually a thoracicradiograph is necessary to evaluate its location. We proposea technique first described by Serafini et al. to establishthe position of a CVC by endocavitary electrocardiography (EC-ECG)and its employment in a large number of uraemic patients requiringhaemodialysis. This technique uses the tip of the CVC as referencelead in a standard electrocardiograph. The best employment ofthis technique has been obtained by echotomographic visualizationof the internal jugular vein executed just before transcutaneouspuncture of the vessel. For 13 months we have successfully appliedthis technique in CVC placement in 81 patients requiring haemodialysis.In our opinion this method is a safe and simple technique thatavoids the need for thoracic radiographs and time lost waitingfor radiographs that prolong the start of the haemodialysissession. According to our experience, we confirm that the EC-ECGtechnique provides a method for ensuring compliance with Foodand Drug Administration guidelines regarding catheter tip locationin uraemic patients.  相似文献   

13.
Central venous catheter misplacement is common (approximately 7%) after right subclavian vein catheterisation. To avoid it, ultrasound-guided tip navigation may be used during the catheterisation procedure to help direct the guidewire towards the lower superior vena cava. We aimed to determine the number of central venous catheter misplacements when using the right supraclavicular fossa ultrasound view to aid guidewire positioning in right infraclavicular subclavian vein catheterisation. We hypothesised that the incidence of catheter misplacements could be reduced to 1% when using this ultrasound technique. One -hundred and three adult patients were prospectively included. After vein puncture and guidewire insertion, we used the right supraclavicular fossa ultrasound view to confirm correct guidewire J-tip position in the lower superior vena cava and corrected the position of misplaced guidewires using real-time ultrasound guidance. Successful catheterisation of the right subclavian vein was achieved in all patients. The guidewire J-tip was initially misplaced in 15 patients, either in the ipsilateral internal jugular vein (n = 8) or in the left brachiocephalic vein (n = 7). In 12 patients it was possible to adjust the guidewire J-tip to a correct position in the lower superior vena cava. All ultrasound-determined final guidewire J-tip positions were consistent with the central venous catheter tip positions on chest X-ray. Three out of 103 catheters were misplaced, corresponding to an incidence (95%CI) of 2.9 (0.6–8.3) %. Although the hypothesis could not be confirmed, this study demonstrated the usefulness of the right supraclavicular fossa ultrasound view for real-time confirmation and correction of the guidewire position in right infraclavicular subclavian vein catheterisation.  相似文献   

14.
The position of the tip of a central venous catheter inserted through an arm vein is not influenced by the arm or by the vein chosen. There may be some advantage in inserting the catheter with the arm at the patient's side, although there seems to be no benefit from turning the patient's head towards the side of insertion. Because the most common malposition from an apparently uneventful insertion is due to the catheter tip entering the internal jugular vein, neck compression has been established as a useful test. If the catheter tip is well into the internal jugular vein, compression on that side of the neck should cause a rise in the recorded pressure of 10 or more cm H20. This rise should not occur on compression of the other side of the neck. We wish to emphasize that it is important to confirm radiographically the position of the catheter tip.  相似文献   

15.
Isolated cases of delayed complications associated with prolonged use of percutaneous central venous lines have been reported. We report four patients who developed hydrothorax more than 24 h after central venous cannulation due to perforation of an intrathoracic vein wall by the catheter tip. The patients were all adults of average body habitus. Left-sided catheters were placed in the operating room after anesthetic induction by experienced personnel using the Seldinger technique and secured in position with a dressing and tape. Chest x-rays taken in the recovery room showed all catheter tips terminated in the central vein and no evidence of hydrothorax. Hydrothorax was manifested in the post-operative period and occurred 1–7 days postcannulation. We are left with the conclusion that the delayed hydrothorax resulted from gradual penetration of the vein wall by the catheter tip. We feel a combination of factors probably contributed to the vein wall erosion. First, the insecure fixation of the catheter combined with head, neck, and cardiopulmonary motion has been shown to result in the back-and-forth movement of the catheter tip. Second, the stiff catheters in the left jugular system take a curved course to the superior vena cava bringing the catheter tip into close proximity to the wall of the superior vena cava. We therefore conclude that late developing hydrothorax can be minimized by using a soft, pliable catheter, sutured firmly in place. Right-sided line placement is preferable to left-sided placement because of the anatomic relationships.  相似文献   

16.
The aim of this study was to compare incidence rates of mechanical and infectious complications associated with central venous catheterization via the internal jugular vein (IJV) versus the subclavian vein (SV) among 45 consecutive patients undergoing orthotopic liver transplantation (OLT) between January 2000 and June 2004. The subjects were divided into two groups according to the site of central venous catheterization (IJV or SV). We recorded each patient's physical characteristics, international normalized ratio (INR), partial thromboplastin time, platelet levels, number of puncture attempts, success/failure of central venous catheterization, duration of catheter placement, occurrence of catheter tip misplacement, arterial puncture, incidence of hematoma or pneumothorax, catheter-related infection, or bacterial colonization of the catheter. Senior staff anesthesiologists performed 22 SV and 23 IJV catheterizations for the 45 OLT procedures. The SV and IVJ groups both had minor coagulation abnormalities with slightly increased INR values at the time of catheterization. There were no significant differences between the groups with respect to success of central venous catheterization (100% for both), numbers of attempted punctures, duration of catheter placement, and incidence rates of mechanical and infectious complications. Both groups showed high frequencies of catheter tip misplacement, with right atrium as the site of misplacement in all cases. Two patients in the IJV group (8.7%) developed hematomas after accidental carotid artery puncture. The results suggest that, when performed by experienced anesthesiologists, central venous catheterization via the SV is an acceptable alternative to IJV catheterization for patients undergoing OLT.  相似文献   

17.
Background : During subclavian vein catheterization, the most common misplacement of the catheter is cephalad, into the ipsilateral internal jugular vein (IJV). This can be detected by chest radiography. However, after any repositioning of the catheter, subsequent chest radiography is required. In an effort to simplify the detection of a misplaced subclavian vein catheter, the authors assessed a previously published detection method.

Methods : One hundred adult patients scheduled for subclavian vein cannulation were included in this study. After placement of subclavian vein catheter, chest radiography was performed. While the x-ray film was being processed, the authors performed an IJV occlusion test by applying external pressure on the IJV for approximately 10 s in the supraclavicular area and observed the change in central venous pressure and its waveform pattern. The observations thus obtained were compared with the position of catheter in chest radiographs, and the sensitivity and specificity of this method were evaluated using a 2 x 2 table.

Results : In 96 patients, subclavian vein cannulation was successfully performed. In four patients, cannulation was unsuccessful; therefore, these patients were excluded from the study. There were six misplacements of venous catheters as detected by radiography. In five (5.2%) patients, the catheter tip was located in the ipsilateral IJV, and in one (1.02%), the catheter tip was located in the contralateral subclavian vein. In the patients who had a misplaced catheter into the IJV, IJV occlusion test results were positive, with an increase of 3-5 mmHg in central venous pressure, whereas the test results were negative in patients who had normally placed catheters or misplacement of a catheter other than in the IJV. There were no false-positive or false-negative test results.  相似文献   


18.
Central venous catheter (CVC)-induced hydrothorax is a delayed complication after the placement of an indwelling subclavian or internal jugular central venous catheter. The catheter tips may cause long-lasting mechanical damages that lead to a slow erosion of the wall of the superior vena cava (SVC), thereby resulting in hydrothorax. The damage may stem from the catheter tips being positioned inappropriately or from the relocation of the catheter tip that was initially ideally positioned. We describe an 80-year-old woman with CVC-induced hydrothorax. She presented with spinal subdural hematoma and preoperatively underwent a multiple-lumen CVC insertion through her left subclavian vein. Her recovery course was uneventful after surgical hematoma removal and spinal cord decompression. However, thirty hours after the CVC placement, the patient began to suffer from an increasing dyspnea. The chest X-ray showed right-sided, massive pleural effusion and a widened mediastinum, requiring the removal of the CVC and the drainage of the pleural fluid. After these procedures, the respiratory status improved rapidly. The present case report suggests that the complication of a hydrothorax may occur after a patient's position changes, and it usually occurs in cases where the catheter tip was initially placed in the ideal position. Operators responsible for CVC placement have to be aware of this delayed complication and have the catheter tips remain in a consistently appropriate position.  相似文献   

19.
Abstract:  A central venous catheter (CVC) is commonly used for intraoperative management by anesthetists and surgeons during major operations, including donor operations for living donor liver transplantation (LDLT), in which donor safety is of utmost importance. Reasons for use of CVC for donors include measurement of central venous pressure and drug infusion when necessary. A potentially serious complication of a major operation is pulmonary thromboembolism. We report two cases of LDLT donors complicated by catheter related thrombosis (CRT) of the jugular vein, who were eventually discharged without long-term complications. To the best of our knowledge, there has been no report of CRT among LDLT donor population. In this report, in order to minimize the risks related to CRT in LDLT donors, we propose thorough screening for thrombophilic disorders, use of a silicone or polyurethane double-lumen CVC as thin as possible, placement of the tip of the CVC at the superior vena cava via the right jugular vein using ultrasonography as a guide for puncture, and removal of the catheter at the end of the operation based on our experience of CRT among LDLT donors.  相似文献   

20.
Precise placement of central venous catheters is necessary to prevent complications and assure proper functioning. Chest X-ray is the current standard method of locating the catheter tip. This is usually not feasible in the operating room setting, particularly after the induction of anesthesia. Intravascular ECG registration using the catheter as a lead and identification of intra-atrial P-waves has been suggested as an alternative. In the present study we evaluated the use of Doppler sonography as a noninvasive method of locating the catheter tip and detecting faulty placement. Two hundred patients scheduled for insertion of a central venous catheter took part in this study. The catheters were inserted via standard routes (internal or external jugular vein, basilar or cephalic vein). A Doppler sonographic device with a 2 mHz probe was used (Parke Electronics 915L). The probe was applied to the right sternal border and affixed at the position where the characteristic venous flow sound was most distinct. The signals were displayed visually, subjected to spectral analysis, and also recorded for later evaluation. A rapid injection of 2-5 ml isotonic saline causes turbulences which can readily be heard and recognized without special training. The position of every catheter was later confirmed by radiography, and in 159 patients the intraatrial ECG method was subjected to direct comparison with the sonographic method. The turbulences due to the injected fluid were found to cause an increased amplitude at frequencies above 350 Hz. If the catheter tip was positioned correctly there was no discernable time lag between the start of the injection and perception of turbulences.(ABSTRACT TRUNCATED AT 250 WORDS)  相似文献   

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