Doppler Monitoring Research Articles

Transcranial doppler monitoring and clinical decision-making after subarachnoid hemorrhage

Our objective was to examine the impact of transcranial Doppler ultrasound (TCD) vasospasm monitoring on clinical decision-making following subarachnoid hemorrhage (SAH). The records of 50 randomly selected patients undergoing serial TCD monitoring following SAH were reviewed. Dates and results of TCDs and cerebral angiograms, the use of hypertensive hemodilution (HH) therapy, and the development of new neurological deficits were recorded. The independent effects of TCD-defined vasospasm and new neurological deficits on patient management were determined with multiple logistical regression. Results were validated in a second randomly selected, 50 patient cohort. Mild or moderate TCD-defined vasospasm developed in 76% of patients 5.8 ± 0.5 days after SAH; 38% developed severe TCD-defined vasospasm after 7.9 ± 0.7 days. Focal neurological deficits occurred in 50% after 5.7 ± 0.6 days with TCD abnormalities preceding the deficit by 2.5 ± 0.7 days in 64%. TCD-defined vasospasm or a new neurological deficit explained 60% of the variance in the use of HH therapy (P =.005). New neurological deficits increased the odds of HH therapy 33-fold (P =.004) whereas there was no independent effect of TCD-defined vasospasm. These variables explained 64% of the variance in the performance of angiography (P =.0002). An abnormal TCD did not increase the odds of angiography whereas its use increased 28-fold (P =.01) after a neurological deficit developed. These results were confirmed in an independent cohort. We concluded that TCD-defined vasospasm did not independently influence the use of HH therapy or angiography with both decisions associated with the development of new neurological deficits. As TCD-defined vasospasm preceded the neurological deficit in 64%, earlier intervention might reduce the incidence of vasospasm-related stroke in institutions with similar practice patterns. Copyright © 2003 by National Stroke Association

Usefulness of ultrasonologic examinations on microemboli and hemodynamics for the prevention of complications associated with carotid endarterectomy

The purpose of this study was to investigate the correlation between plaque characteristics and microembolic signals using transcranial Doppler during endarterectomy. We also investigated successive changes of the pulsality index and average flow velocity in the ipsilateral middle cerebral artery. The subjects of the study were 28 patients who underwent carotid endarterectomy. Transcranial Doppler monitoring was performed before, during, and after carotid endarterectomy. Plaques were classified into 3 types by the brightness on B-mode ultrasonogram. In addition, extracted specimens were macroscopically examined to observe the presence of plaque ulcerations and intraplaque hemorrhages. The blood flow of the internal carotid artery in all cases was measured intraoperatively using an electromagnetic flow meter. The patients who had plaque ulcerations showed significantly more microembolic signals preoperatively than those who had intraplaque hemorrhage during an endarterectomy. Flow velocity in the ipsilateral middle cerebral artery increased immediately after the operation and reached its peak on the day after the operation. The pulsality index reached its peak on the day of the operation, and remained at this point until 2 days after the operation. We conclude that (1) the patients who had intraplaque hemorrhage had a high risk for embolization of manipulation during dissection and carotid endarterectomy, and (2) systemic management, including that of blood pressure under transcranial Doppler monitoring, was necessary for at least 3 postoperative days in order to prevent hyperperfusion. Copyright © 2003 by National Stroke Association

Provision of training in carotid surgery does not compromise patient safety.

Vascular surgeons perceive that carotid endarterectomy carries a higher risk of stroke if performed by a surgical trainee. Accordingly, some trainees consider that they receive a less than adequate training in carotid surgery before taking up a consultant position. The aim of this study was to establish whether the stroke rate was adversely affected if carotid endarterectomy was performed by a surgical trainee under consultant supervision. This was a prospective study of 151 consecutive patients undergoing carotid endarterectomy between 1 January and 31 December 1996 using a standardized technique including intraoperative and postoperative transcranial Doppler monitoring and completion angioscopy. The overall mortality and/or disabling stroke rate was 0.7 per cent (one of 151 patients), whereas the mortality and/or any stroke rate was 1.3 per cent (two of 151). Surgical trainees performed 82 of 151 carotid endarterectomies, with a mortality rate of 1 per cent and a mortality and/or any stroke rate of 2 per cent. There was no significant difference in the incidence of retained thrombus or intimal flaps between trainees and consultants as detected by angioscopy. Vascular surgical trainees can receive a comprehensive training in carotid artery surgery without incurring an unacceptable increase in operative risk.

Cerebral and Systemic Hemodynamics Changes During Upright Tilt in Chronic Fatigue Syndrome

During head-up tilt (HUT), patients with chronic fatigue syndrome (CFS) have higher rates of neurally mediated hypotension (NMH) and postural tachycardia syndrome (POTS) than healthy controls. The authors studied whether patients with CFS were also more likely to have abnormal cerebral blood flow velocity (CBFV) compared with controls in response to orthostatic stress. Transcranial Doppler monitoring of middle cerebral artery (MCA) CBFV was performed during 3-stage HUT prospectively in 26 patients with CFS and 23 healthy controls. At the same time, continuous monitoring of arterial blood pressure (BP), heart rate (HR), endtidal CO2 (ET-CO2) were performed. Results are reported as mean +/- SD. NMH developed in 21 patients with CFS and in 14 controls (P = .22). POTS was present in 9 CFS patients and 7 controls (P = .76). Supine HR was higher in CFS patients, but all other hemodynamics and CBFV measures were similar at baseline. The median time to hypotension did not differ, but the median time to onset of orthostatic symptoms was shorter in those with CFS (P < .001). The CBFV did not differ between groups in the supine posture, at 1 or 5 minutes after upright tilt, at 5 or 1 minute before the end of the test, or at termination of the test. Mean CBFV fell at termination of tilt testing in those with CFS and controls. ET-CO2 was lower at termination of the test in those with CFS versus controls (P = .002). The results of this study are not consistent with the hypothesis that patients with CFS have a distinctive pattern of MCA CBFV changes in response to orthostatic stress.

2P-0525 In vivo realtime hemodynamic changes caused by microembolism detected by transcranial Doppler monitoring of the middle cerebral artery stenosis

2P-0525 In vivo realtime hemodynamic changes caused by microembolism detected by transcranial Doppler monitoring of the middle cerebral artery stenosis

Endosonographic Doppler-Guided Manometry of Esophageal Varices: Experimental Validation and Clinical Feasibility

The risk of variceal bleeding cannot be accurately predicted using endoscopy alone. Although variceal pressure has been demonstrated to be a major determinant for the rupture of esophageal varices, direct determination by needle puncture is unsuitable for routine clinical use. Due to their operator-dependency, current noninvasive endoscopic methods for determination of variceal pressure have not gained wide acceptance. We have developed a new method of measuring variceal pressure, using endoscopic power Doppler imaging to monitor the manometry of esophageal varices. The aims of this study were to test in vitro the accuracy of Doppler-guided manometry and to assess the clinical feasibility of this method. Experimental validation of this technique was performed using an in vitro model of artificial varices of different sizes. A linear-array endosonography (EUS) probe with power Doppler capability was used to assess flow in the varices and a balloon for manometry of esophageal varices was attached to the tip of the probe. Pressure readings were made at the time of disappearance of the Doppler signal during variceal compression by the balloon. Linear regression analysis was used to compare the results of Doppler-guided and direct intraluminal pressure measurement in the artificial varices. Variceal pressure was then measured with this technique in 28 patients with portal hypertension and esophageal varices without previous bleeding, and the results were compared with portal pressure assessed according to the hepatic vein pressure gradient (HVPG). In vitro studies demonstrated a good correlation between the pressure measured with Doppler monitoring and the actual intravariceal pressure (r > or = 0.922; P < 0.001). The determination of variceal pressure with this method was technically successful in 26/28 patients (93 %). The intraoperator variance was 9.3 +/- 8.6 %. Overall, the mean variceal pressure was significantly lower than the mean HVPG (21.2 +/- 5.3 mmHg vs. 24.3 +/- 7.8 mmHg; P < 0.01). Variceal pressure and portal pressure (as assessed by the HVPG) correlated significantly (r = 0.64; P < 0.001). Our preliminary results indicate that EUS Doppler-guided manometry of esophageal varices is feasible and accurate. This technique may become a more reliable method for noninvasive measurement of variceal pressure and warrants further investigation.

DERMAL OBJECTIVE PHARMACODYNAMIC PROFILE OF CETIRIZINE AND EPINASTINE: TWO CONTROLLED, RANDOMISED, DOUBLE‐BLIND, CROSSOVER STUDIES

SUMMARYTwo double‐blind clinical pharmacology studies were performed in healthy volunteers to compare the dermal pharmacodynamic profile of epinastine with cetirizine, a well‐documented anti‐H1 antagonist, after oral administration at the usual recommended dosage, i.e. 10 mg cetirizine and 20 mg epinastine (versus placebo). Histamine skin challenges (prick test) were evaluated before and at 1, 2, 4, 8 and 24 hr after drug intake by measuring the wheal and flare area (studies 1 and 2) along with laser Doppler monitoring of the microvascular responses (study 2). A decrease in wheal and flare areas was observed following intake of both drugs compared with placebo controls. With the notable exception of 1 hr post dose wheal values, which were consistently smaller after epinastine, cetirizine was superior to epinastine for both wheal and flare at all other times. At the prick test site, treatment with epinastine and cetirizine accentuated the increase in blood flow induced by histamine. This reflects the decrease of the whealing but there was no significant difference between the two active test compounds. At 1 cm from the prick test site, the administration of both active treatments inhibited the increase of blood flow, and cetirizine showed a more potent inhibitory effect from 8 hr post dose. This reflects the reduction of the flare induced after histamine‐receptor activation of the axon reflex. In conclusion, epinastine shows a rapidly greater (within 1 hr post dose on the wheal only) but vanishing effect than cetirizine. At all other time points, cetirizine was generally more effective than epinastine.

Intensive Care for Patients with Subarachnoid Haemorrhage

The intensive care treatment in patients with subarachnoid haemorrhage (SAH) is aimed at maintenance of adequate cerebral perfusion and oxygenation. SAH is charged in 40% of cases with at least one life-threatening event and 20 to 30% of deaths are related to extracerebral complications. So the main task in Neurointensive Care is to keep the physiological parameters under control. That is why we need accurate monitoring. Currently used systemic and cerebral monitoring is thus presented. Even basic cardiovascular monitoring (ECG, blood pressure, pulse oxymetry, central venous pressure, urine output) need a great workload in managing the quality of signals and raw data. SAH is often associated with cardiovascular impairment; haemodynamic monitoring is then necessary to graduate hynotropic (stroke volume, cardiac index, systemic and pulmonary resistances) and volemic support (central venous pressure, wedge pressure): a Swan-Ganz catheter is then indicated. Then ventilation is considered: non only a “cerebral” oriented ventilation but a strategy aimed at pulmonary protection too. The ultimate result of ventilation is still adequate oxygenation and acid-base balance that are to be verified. Cerebral monitoring is then resumed starting from cerebral perfusion pressure. The O2 delivery is monitored by a global estimation like jugular venous oxygen saturation, that has a low sensitivity in SAH patients, and by tissue O2 tension which measure O2 delivered near the injured area. Lastly, Transcranial Doppler Monitoring is presented with its limits and indications. Three clinical examples are presented on a multimodal approach in TCD, PtO2 and cerebral perfusion pressure monitoring.

Procedures and Monitoring for the Critically Ill

Procedures and Monitoring for the Critically Ill is a multi-authored manual, detailing 29 procedures and monitoring techniques used in intensive care. This is an expedient, introductory critical care reference, particularly for physicians in training. The topics are pragmatic, describing common procedural topics for intensive care. Typically, each area has an effective description of the methods and illustrations of the techniques. A bibliography of key references accompanies each chapter. Succinct descriptions of step by step methods as well as the required supplies are included for 1) hemodynamic monitoring (e.g., central venous pressure, pulmonary artery catheterization, arterial catheterization); 2) neurologic monitoring (e.g., intra-cranial pressure monitoring, jugular bulb oximetry); 3) trauma related areas (e.g., spinal immobilization, intra-abdominal pressure monitoring, abdominal paracentesis; 4) emergency airway support (e.g., endotracheal intubation, cricothryrotomy, bronchoscopy, and tracheostomy); as well as 5) other areas including transesophageal Doppler monitoring, epidural analgesia, renal support, and inferior vena cava filter placement. For greater detail in ICU monitoring procedures, interested readers are recommended to more encyclopedic texts, such as Principles and Practices of Intensive Care Medicine, edited by M.Tobin. In summary, this text is a useful reference during the preliminary years of training for critical care or rapid review of methodologies of ICU procedures and monitoring techniques.

Possible determinants of early microembolism after carotid endarterectomy.

High numbers of microembolic signals (MES) have been associated with increased risk of postoperative stroke after carotid endarterectomy (CEA). We sought to identify factors predictive of postoperative MES. Transcranial Doppler monitoring of the ipsilateral middle cerebral artery for MES was performed for 30 minutes during the first postoperative hour in sequential patients undergoing CEA. Stepwise binomial logistic regression analysis was performed to identify preoperative and intraoperative variables that predicted the occurrence of postoperative MES. We studied 141 patients (mean age, 69 years); 102 (72%) were male, and 69 (49%) had at least 1 MES (range, 1 to 118) detected in the first postoperative hour. The risk of postoperative MES was greater in women (P=0.027), patients not receiving antiplatelet therapy (P=0.033), and patients undergoing left-sided CEA (P=0.049). Other variables such as residual stenosis seen on completion angiography and operative technique were not associated with postoperative MES. Postoperative MES were most likely in women, patients not receiving preoperative antiplatelet therapy, and patients who had a left CEA. Microembolism might explain why these same factors are associated with higher rates of perioperative stroke.

Prognostic significance of left ventricular diastolic dysfunction in essential hypertension

ObjectivesWe sought to assess the prognostic value of alterations in left ventricular (LV) diastolic function in patients with essential hypertension. BackgroundAlterations in LV diastolic function are frequent in patients with hypertension, even in the absence of LV hypertrophy, but their prognostic significance has never been investigated. MethodsIn the setting of the Progetto Ipertensione Umbria Monitoraggio Ambulatoriale (PIUMA) study, we followed, for up to 11 years (mean: 4.4 years), 1,839 Caucasian hypertensive patients (50 ± 12 years, 53% men, blood pressure (BP) 156/98 mm Hg) without previous cardiovascular events, who underwent Doppler echocardiography and 24-h BP monitoring before therapy. The early/atrial (E/A) mitral flow velocity ratio was calculated and corrected for age and heart rate (HR). ResultsDuring follow-up, there were 164 major cardiovascular events (2.04 per 100 patient-years). The incidence of cardiovascular events was 2.47 and 1.65 per 100 patient-years in patients with an age- and HR-adjusted E/A ratio below (n = 919) and above (n = 920) the median value, respectively (p < 0.005 by the log-rank test). In Cox analysis, controlling for age, gender, diabetes, cholesterol, smoking, LV mass and 24-h systolic BP (all p < 0.05), a low age- and HR-adjusted E/A ratio conferred an increased risk of cardiovascular events (odds ratio 1.57, 95% confidence interval [CI] 1.11 to 2.18, p < 0.01). A 21% excess risk was found for each 0.3 decrease of the adjusted E/A ratio (95% CI from +2% to +43%; p = 0.03). ConclusionsImpaired LV early diastolic relaxation, detected by pulsed Doppler echocardiography, identifies hypertensive patients at increased cardiovascular risk. Such association is independent of LV mass and ambulatory BP.

Transcranial Doppler ultrasound: a new method of monitoring hemispheric anesthetization during the intracarotid amobarbital procedure.

Electroencephalography (EEG) is traditionally used to assess the duration of hemispheric anesthetization and to monitor return of function in the anesthetized hemisphere during the intracarotid amobarbital procedure (IAP), but EEG changes are not consistently seen. The authors evaluated the role of continuous transcranial Doppler (TCD) monitoring as an alternative to EEG. The authors performed both continuous TCD monitoring and EEG during the IAP in 10 patients with medically intractable partial epilepsy. Mean velocities were monitored continuously in both middle cerebral arteries (MCAs), and changes in MCA velocities on continuous TCD monitoring were time locked with the EEG changes. The average mean MCA velocities were within normal limits bilaterally (50-85 cm/s) in all patients at baseline. Mean MCA velocites increased in all patients to 95-115 cm/s at the start of the test when the patients were asked to raise their hands and start counting. After injection of sodium amobarbital, mean MCA velocities in all patients dropped dramatically on the ipsilateral side to values of 12-39 cm/s and returned to the baseline average value when the hemiparesis recovered. In 8 patients, the duration of delta activity on EEG coincided with the time interval during which the mean MCA velocities were low on TCD monitoring. In 2 patients, despite the presence of hemiparesis clinically and a drop in mean MCA velocities on the ipsilateral side on continuous TCD monitoring, EEG remained normal on the ipsilateral side. Continuous TCD monitoring may be a more sensitive method than EEG in determining the duration of hemispheric anesthetization during IAP. Because the items for assessment of memory are presented during the period of hemispheric anesthetization, TCD may be useful in more precisely defining the time window for memory testing.

Transcranial Doppler during suspected brain death in children: Potential limitation in patients with cardiac "shunt"

OBJECTIVES: We report a potential limitation of transcranial Doppler for assessing cerebral circulation during suspected brain death in children. DESIGN: Review of two case series identified during our clinical practice. PATIENTS: Eight children with suspected brain death and seven with intact-brain and cardiovascular anomalies. MEASUREMENTS AND MAIN RESULTS: Brain-death criteria included lack of cerebral-brainstem reactivity, electrocortical silence and absent blood flow by brain scintigraphy ((99m)Tc-hexamethylpropylenamine oxime). Five intracranial Doppler patterns were found in eight cases of suspected brain death: A) orthograde continuous flow; B) reduced systolic flow velocity with absence of diastolic flow; C) reduced systolic flow velocity with retrograde diastolic flow, sometimes with antegrade late diastolic flow; D) systolic spikes of very low flow velocity; and E) absence of Doppler signals. Only patterns "C," "D," and "E" were associated with the absence of supra- and infratentorial brain perfusion. The most common Doppler alterations in patients with intact-brain and cardiovascular anomalies were the absence of diastolic flow (pattern "B") or the presence of retrograde flow during diastole (pattern "C"). CONCLUSION: Transcranial Doppler monitoring of pediatric patients may have value in identifying patients who have severe cerebral compromise, who may progress to brain death. However, key Doppler alterations, such as absent or retrograde flow during diastole, are not uniquely associated with the diagnosis of brain death, particularly in the setting of congential heart disease. The use of conventional methodology for the diagnosis of brain death in infants and children remains the "gold standard."

Neurologic Monitoring During Cardiac Surgery

Strategies for basic and advanced neuromonitoring techniques are reviewed. Cerebral hyperthermia during rewarming and unrecognized jugular venous obstruction are associated with cerebral compromise and can be readily detected and avoided. The strengths and limitations of transcranial Doppler and electroencephalographic monitoring are reviewed, as is use of noninvasive cerebral optical spectroscopy and jugular venous oximetry. The potential for reduction in perioperative stroke by using epiaortic scanning to detect and avoid otherwise nonpalpable atherosclerotic plaque, is also reviewed.

Cardiac output determination during experimental hemorrhage and resuscitation using a transesophageal Doppler monitor

Transesophageal Doppler (TED) has been considered a noninvasive and accurate alternative to pulmonary artery catheter for volume replacement and cardiac output measurement in patients undergoing major surgeries.

Detection of Microembolic Signals in Patients with Neuropsychiatric Lupus erythematosus

The pathogenesis of central nervous system involvement in systemic lupus erythematosus (SLE) is not completely understood. In this study, we investigated the association of microembolic signals (MES) with a variety of neuropsychiatric SLE manifestations and compared our results with those from SLE patients without neuropsychiatric lupus and normal controls. Fifty-three patients with SLE (45 females and 8 males), all fulfilling the revised classification criteria for SLE, and 50 control subjects (44 females and 6 males) were enrolled in this study. All SLE patients were assessed by neuropsychological examination, including various neuropsychiatric tests. Twenty-five patients with SLE were found to have at least one of the neuropsychiatric syndromes defined by The American College of Rheumatology. The mean MES count in patients with neuropsychiatric lupus was significantly higher than those without (5.4 ± 1.1 vs. 0.3 ± 0.8/h; p < 0.005). We found a positive correlation between higher mean MES counts and the presence of neuropsychiatric syndromes in SLE. The mean MES count in the whole group of SLE patients was also significantly higher than that in healthy controls. The mean MES count of SLE patients with antiphospholipid (aPL) antibody positivity was significantly higher than those without aPL antibodies (3.6 ± 1.6 vs. 0.8 ± 0.1/h; p < 0.005). In conclusion, the association of MES with neuropsychiatric lupus may support the possible contribution of MES to the complex pathophysiology of this syndrome. More importantly, detection of MES on transcranial Doppler monitoring might suggest a high risk of involvement of the central nervous system in SLE, and could be used as a diagnostic tool.

Cessation of embolic signals after antithrombotic prevention is related to reduced risk of recurrent arterioembolic transient ischaemic attack and stroke

Objectives: To evaluate the reduction of embolic signals after the initiation of an antithrombotic secondary prevention in patients with recent arterioembolic stroke and to determine the predictive value of decreased...

Comparison of Transesophageal Doppler Monitor vs. Pulmonary Artery Catheter in the Hemodynamic Indices of Major Burn Patients Undergoing an Extensive Escharectomy

Background: In major burn patients, many invasive monitors including a pulmonary artery catheter (PAC) are often required to assess hemodynamic status. An esophageal Doppler monitor (EDM), as a noninvasive method of measuring hemodynamic parameters, may be a substitute for a PAC in this clinical circumstance. This study was conducted to evaluate the validity of Doppler derived hemodynamic indices in comparison to that of a PAC. Methods: A total of 20 critically ill, severe burn patients, scheduled for an elective escharectomy and application of artificial dermis, were enrolled for the placement of a PAC and EDM. Simultaneous data was collected in regular intervals and the various parameters were compared between the two methods. Results: A total of 158 pairs of data in 20 patients were gathered. Among all the parameters, cardiac output (CO) and stroke volume (SV) showed consistently 20% less in EDM. Correlation coefficients of heart rate (HR), CO, SV and systemic vascular resistance (SVR) were 0.97, 0.54, 0.62, and 0.68 respectively. Corrected flow time (FTc) had poor correlations with central venous pressure (CVP) and pulmonary capillary wedge pressure (PCWP). In the mean time, significant, but very weak correlations with FTc vs. CO and SV were demonstrated. Conclusions: EDM may be a substitute for a thermodilution (TD) PAC technique, it can be used with usefulness for hemodynamic and preload assessment in major burn patients.

けい動脈狭窄合併患者の心拍動下冠動脈バイパス術および腹部大動脈りゅう人工血管置換術同時手術の麻酔経験

けい動脈狭窄合併患者の心拍動下冠動脈バイパス術および腹部大動脈りゅう人工血管置換術同時手術の麻酔経験

Can the Esophageal Doppler Monitor Be Used to Clinically Evaluate Peak Left Ventricle dP/dt?

The esophageal Doppler monitor (EDM) is minimally invasive and allows for rapid and continuous cardiovascular measurements which are based upon aortic blood flow characteristics. Using a model derived from the modified Bernoulli equation, a measure of peak left ventricle (PLV) dP/dt has been developed which utilizes EDM-based parameters: PLV \(\frac{{dP}}{{2t}}\alpha \frac{{V_P^2 \cdot \sqrt {HR} }}{{T_{FC} }}\); where Vp represents peak velocity of aortic blood flow, TFC is corrected flow time, and HR is heart rate. Additional clinical research is necessary to provide a correlation of this formula with invasive measurements. A wave transmission model of PLV dP/dt has also been examined. This model requires simultaneous measurement of aortic pulse wave velocity, or aortic flow wave velocity, in order to calculate PLV dP/dt. Current echocardiographic analyses of PLV dP/dt show that the wave transmission model provides better correlation with in vivo catheterization results when compared with the modified Bernoulli equation. The EDM remains a useful tool for rapid and continuous evaluation of cardiovascular indices. Further research and development, of this monitor for PLV dP/dt assessment, is warranted.