Microperfusion pump-systems and development

Summary. Transluminal coronary angioplasty has become an established form of treatment for coronary artery disease. The dilatation time is normally restricted by the ischaemic tolerance. Until today passive perfusion catheters have been used to maintain coronary blood flow to the distal segment. However, such continuous perfusion has often been insufficient to retain myocardial function. Active perfusion catheters, instead, have not been introduced so far for technical reasons. Active coronary perfusion via dilatation catheters with an intracorporal rotary micropump was the objective of investigations by Fraunhofer-IPA and the University of Essen. The result of the development activities was an internal geared pump with an outer diameter of 2.5 mm. Several design studies were undertaken to integrate the micropump in a PTCA catheter. The most important aspect of the integrated micropump is that the dilatation time can be prolonged. First in vitro tests with whole-blood showed acceptable mechanical haemolysis of the pump system. Further in vitro tests will lead to an optimized pump design with low mechanical haemolysis and a high flow rate.     

Effect of cold pressor test and awareness of hypertension on platelet function in normotensive and hypertensive women

Mundal HH, Nordby G, Lande K, Gjesdal K, Kjeldsen SE, Os I. Effect of cold pressor test and awareness of hypertension on platelet function in normotensive and hypertensive women. Scand J Clin Lab Invest 1993; 53: 585-591.

Plasma β-thromboglobulin (J3-TG) concentration, reflecting platelet function in vivo was compared in fertile women with untreated essential hypertension and age-matched normotensives, in two separate studies. In the first study, hypertensives and normotensives were aware of their blood pressure status. Blood was sampled through arterial and venous indwelling catheters, and no difference in β-TG was found between the groups. Arterial /3-TG was significantly lower than venous concentration (p ≤ 0.05). Cold pressor test increased arterial β-TG significantly in both groups (p ≤ 0.05).

In the second study, both women and investigator were unaware of blood pressure status, and /3-TG concentration, platelet count, and mean platelet volume obtained by venipunctures were similar in the hypertensive and normotensive group.

Thus, platelet function in vivo seems to be normal in fertile hypertensive women, in contrast to the platelet dysfunction previously reported in hypertensive men. In women, as in men, platelet release occurred during venous catheter blood sampling and during cold pressor test. However, at variance from men, platelet function was not influenced by awareness of blood pressure status in the hypertensive females.     

Improved bronchial cleansing in intensive care patients with a new double-lumen catheter

Objectives A new double lumen catheter with a small channel for application of rinsing solution in deeper parts of the endobronchial tree was developed and its efficiency was tested in two trials.Design Comparison of the new catheter in 2 controlled studies with the traditional way of suctioning and with conventional endotracheal lavage in a randomized block design.Setting Intensive care unit of a university hospital.Patients In the first study, endobronchial cleansing with the new catheter was compared to the traditional way of suctioning in 12 longtime ventilated patients. In the second study, 28 ventilated patients received either conventional lavage or lavage with the new catheter.Interventions In the first trial the bronchial system of each patient was suctioned 25 times with a conventional technique or cleansed by using the new catheter. In the second study, patients alternatively received conventional lavage 88 times or lavage 88 times with the new catheter.Measurements and results Drained sectetions averaged 0.84±0.28 ml using conventional cleaning as compared to 11.02±0.84 ml with the new catheter. This was accompanied by a significant (p<0.001) increase in PaO₂ of 24.20±7.90 mmHg after 10 min compared to nearly unchanged PaO₂ after normal suctioning. In the second study, suctioned volume was 2.48±0.21 ml using conventional endotracheal lavage and 10.55±0.47 ml using the new catheter. Use of the double-lumen catheter induced a significant increase in PaO₂ by 30.90±3.90 mmHg within 10 min. The changes in PaO₂ correlated with the drained volume.Conclusion Both studies show that suctioning with the new double lumen catheter allows drainage of a larger volume of secretions and results in a greater improvement of oxygenation.     

The influence of different levels of PEEP on peripheral tissue perfusion measured by subcutaneous and transcutaneous oxygen tension

Objective To compare subcutaneous (PscO₂) and transcutaneous (PtcO₂) oxygen tension measurements in relation to hemodynamic variables at different levels of PEEP, and to evaluate the usefulness of these measurements as monitors of peripheral tissue perfusion.Design Prospective trial.Setting Intensive care unit in a university hospital.Patients Seven patients with gastric cancer who where undergoing total gastrectomy.Interventions Silicone catheter was placed in the upper arm and transcutaneous oxygen monitor was placed on the upper part of the chest. A pulmonary artery catheter was placed in the right pulmonary artery.Measurements and results PscO₂ and PtcO₂ together with hemodynamic variables were measured at different levels of PEEP. Progressive increase of PEEP reduced cardiac index (CI) (p<0.05) with a concomitant decrease of PscO₂ (p<0.05) and oxygen delivery (DO₂) (p<0.05). Changes in PtcO₂ parallelled changes in arterial oxygen tension (PaO₂), but no correlation was found between PtcO₂, CI and DO₂.Conclusion PscO₂ is a sensitive indicator of subcutaneous tissue perfusion, which can be used to identify the PEEP level, with optimum peripheral perfusion. PscO₂ seems to be a more reliable indicafor of tissue perfusion than PtcO₂.This study was supported by Tore Nilsons Fund for Medical Research. Lundgrens Stiftelse, Medical Faculty, University of Lund and by the Swedish Medical Research Council Projecr no. B88-17x-00640-24B     

Perfusion pressure of a new cannulating fenestrated pedicle screw during cement augmentation

BackgroundCannulating fenestrated pedicle screws are effective for fixating osteoporotic vertebrae. However, a major limitation is the excessive pressure required to inject a sufficient amount of cement into the vertebral body through the narrow hole of a pedicle screw. We have recently proposed a new cannulating fenestrated pedicle screw with a large hole diameter and a matched inner pin for screw-strength maintenance. Our purpose was to determine whether the new screw can significantly reduce bone-cement perfusion pressure during cement augmentation,MethodsTwo different methods were used to examine perfusion pressure. Hagen–Poisseuille's flow model in a tube was used to calculate pressure drop in the bone-cement channel. Experimentally, both Newtonian silicone oil and bone-cement (polymethyl methacrylate) were tested using a cement pusher through the cannulating screw at a constant rate of 2 ml/min.FindingsThe internal hollow portion of the screw was the bottleneck of the perfusion, and the new design significantly reduced the perfusion pressure. Specifically, perfusion pressure dropped by 59% (P < 0.05) when diameter size was doubled.InterpretationThe new design effectively improved the application of bone-cement augmentation with the ease of bone-cement perfusion, thereby enhancing operational safety.     

Implantable sensor for blood flow monitoring after transplant surgery

A limited number of techniques are employed in clinical medicine for regional tissue perfusion assessment. These methods are marginally effective and are not well suited for implantation due to the inability to miniaturize the associated technologies. Consequently, no standardized techniques exist for real-time, continuous monitoring of organ perfusion following transplantation. In this paper, a brief overview of the relevant clinical techniques employed for regional tissue perfusion assessment is given with particular emphasis on post-surgical monitoring of transplanted organs. The ideal characteristics for a perfusion monitoring system are discussed and the development of a new, completely implanted local tissue monitoring system is summarized. In vivo and in vitro data are presented that establish the efficacy of this new technology, which is a photonics-based sensor system uniquely suited for continuous tissue monitoring and real-time data reporting. The suitablity of this sensor technology for miniaturization, which enables implantation for monitoring localized tissue perfusion, is discussed.     

Pressure measurement evaluation and accuracy validation: the Gabarith test

Objective: The dynamic distortion introduced by manometric systems has been known for many years, with several methods developed to describe and quantify the degree of distortion. We developed the Gabarith as a technique to describe more accurately, and yet more simply, the dynamic accuracy of the chain of monitoring. Setting: A pressure monitoring system transforms some input signal, i. e. the actual pressure waveform present in the artery, into some other shape of waveform, i. e. the waveform displayed on the patient monitor. This transformation is characterized by the transfer function of the total system. A complete technique to define the transfer function is to measure the response directly at many different frequencies and combine them to produce the dynamic response plot. Method: We described the dynamic response of a monitoring chain and we simplified the communication of this dynamic response to users by developing the Gabarith, as a tolerance envelope based on the frequency content of typical pressure waveforms. If a given monitoring chain's dynamic response (including a catheter, a pressure kit and a monitor) can be shown to fall within that tolerance envelope, the chain will provide adequate dynamic accuracy. Conclusion:“Gabarith tested” means that a pressure kit, in combination with a catheter and a monitor, has had its frequency response function measured and that the function falls within a tolerance band for dynamic accuracy. Passing a Gabarith means that a given level of accuracy will be reached when using the sets which have passed the corresponding test. Received: 18 November 1997 Accepted: 5 October 1998     

Menopause-associated changes in plasma lipids, insulin-like growth factor I and blood pressure: a longitudinal study

We examined the effects of the menopause transition on plasma lipids, insulin-like growth factor I (IGF-I) and blood pressure. An initial cohort of 38, non-smoking, healthy premenopausal women (44–48 years) were examined at baseline and after a 6-year follow-up period. At follow-up, 18 women had spontaneously stopped menstruating, whereas 17 women remained premenopausal. Women who experienced natural menopause showed a greater decline in high-density lipoproteins (?5 ± 4 mg dL^?1 vs. ?1 ± 3 mg dL^?1; P < 0.01) and a greater increase in low-density lipoproteins (13 ± 12 vs. 5 ± 10 mg dL^?1; P < 0.05) and fasting triglycerides (14 ± 15 vs. 5 ± 11 mg dL^?1; P < 0.05) than women who remained premenopausal. No menopause effect was noted for total cholesterol. We noted a greater decline in IGF-I levels in women who experienced a natural menopause (?21 ± 11 ng mL^?1) than women who remained postmenopausal (?4 ± 10 ng mL^?1). Systolic blood pressure increased in postmenopausal (13 ± 10 mmHg) compared with premenopausal women (5 ± 4 mmHg; P < 0.01), whereas no menopause effect was noted for diastolic blood pressure. The increase in the waist-to-hip ratio was related to a decrease in high-density lipoprotein (r = ?0.49; P ? 0.05) and increase in low-density lipoproteins (r = 0.48; P < 0.05). The decline in IGF-I was related to the decline in reported leisure time physical activity (0.44; P < 0.05). We conclude that the natural menopause transition is associated with a worsening of the lipid profile and decline in IGF-I, which might be mitigated by deleterious changes in body fat distribution and physical activity.     

Computed tomographic evaluation and guided correction of malpositioned nephrostomy catheters

Background: To determine the utility of computed tomography (CT) in the detection and correction of malpositioned nephrostomy catheters after contrast spillage during nephrostograms. Methods: CT was performed in nine patients after an abnormal (contrast spillage) tube nephrostogram performed during or after nephrostomy tube placement. CT was used to locate the nephrostomy catheter position in relation to the renal collecting system. If possible, CT was also used for guidance and repositioning of the nephrostomy catheters into the intrarenal collecting system. Results: In all nine cases, CT was successful in detecting the position of the suspected malpositioned catheter. In seven of nine cases, CT demonstrated the catheter outside the renal collecting system and effectively helped reposition the catheters into the intrarenal collecting system. In one case, the malpositioned nephrostomy catheter was within the intraperitoneal cavity and required surgical correction. Another case required fluoroscopic-guided repositioning for the initial nephrostomy catheter, which was partly posterior to the kidney and partly within the kidney. The catheter in this latter case was successfully advanced over a guidewire into the collecting system. Conclusions: CT may be used to detect possible catheter malposition associated with nephrostomy tube placement. CT may also be used to successfully guide catheter repositioning in the renal collecting system. Received: 29 May 1998/Accepted: 20 July 1998     

Aortic reservoir function, estimated myocardial demand and coronary perfusion pressure following steady-state and interval exercise

Aortic reservoir function is a measure of the aorta's ability to distribute blood during diastole, attenuating the pulsatility of blood flow, and is important in balancing cardiac flow. Effects of acute high versus moderate exercise intensity on reservoir function and cardiac energetics is unknown. Eighteen athletes completed a interval (INT) and steady‐state (SS) cycling bout at 60% of VO₂ peak. Reservoir function was calculated as the ratio of diastolic run‐off to stroke volume and expressed as a percentage. Coronary perfusion pressure was derived from tissue Doppler imaging and echocardiography. Systolic tension–time integral (TTI) from the aortic pressure waveform served as a measure of myocardial oxygen consumption. All measures were made at rest, 30‐min postexercise and 60‐min postexercise. Average reservoir function before SS was 76%, which was reduced to 62% 30‐min post‐SS and 67% 60‐min post‐SS (P<0.05). Significantly greater reductions in reservoir function were seen following INT (from 71% pre‐INT to 45% 30‐min post‐INT and 53% 60‐min INT, P<0.05). Estimated coronary perfusion pressure was reduced 30 min following INT but not SS; both bouts reduced coronary perfusion pressure at 60‐min postexercise (P<0.05). TTI increased following both INT and SS at 30‐ and 60‐min postexercise with greater increases following INT (P<0.05). Following exercise, reservoir function was associated with TTI (P<0.05), but not coronary perfusion pressure (P>0.05). We conclude that reservoir function is attenuated following acute SS and INT, but these reductions were greater post‐INT, suggesting that exercise intensity affects reservoir function. Reduction of reservoir function following exercise is related to TTI, a reflection of myocardial oxygen consumption but apparently not associated with coronary perfusion pressure.     

Myocardial perfusion defects and coronary risk factors in symptomatic and asymptomatic elderly women

Background We investigated the relation between risk factors of coronary artery disease (CAD) and myocardial ischemia detected by ²⁰¹Tl SPECT in elderly women. Methods 306 women aged ≥75 yr (79.1 ± 3.6 yr) who underwent pharmacologic ²⁰¹Tl SPECT for suspected CAD based on symptoms or CAD risk factors were included. Coronary risk factors were evaluated by medical records, and included diabetes mellitus (DM), hypertension, hypercholesterolemia, cigarette smoking, greater age (≥80 yr), and obesity. Summed stress score (SSS), summed rest score (SRS), and summed difference score (SDS) were calculated based on stress and redistribution SPECT images for semiquantification. Results The symptomatic group (n = 110) had a 34.5% perfusion defect rate. The asymptomatic group (n = 196) had a significantly lower perfusion defect rate of 16.8%. However, this significantly increased to 29.4% and 22.0% in the presence of diabetes mellitus (DM) and hypertension, respectively. In addition, the summed stress score of asymptomatic patients (12.4 ± 6.0) was not lower but comparable to that of symptomatic patients (10.0 ± 6.0). Conclusions In elderly women suspected of CAD, pharmacologic perfusion imaging can be used to identify myocardial ischemia in patients with angina as well as asymptomatic subjects with concurrent DM or hypertension.     

Endoscopic placement of a tracheal oxygen catheter: a new technique

Objective: In patients with chronic obstructive pulmonary disease (COPD), intratracheal oxygen insufflation (ITO) is an established therapeutic approach. We developed a new endoscopic technique of intratracheal catheter placement. The aim of this pilot study was to demonstrate its short-term feasibility in acutely extubated patients with moderate to severe COPD who require oxygen therapy. Design: A guide wire was inserted through a nasally passed bronchoscope and was positioned such that its tip was placed intratracheally. Using a “Seldinger technique“, the tracheal catheter was then inserted over the wire to a point 2–3 cm proximal to the carina and positioned under direct vision from the bronchoscope inserted through the contralateral nose. After catheter insertion, the guide wire was removed. The patients scored catheter-associated local discomfort using a visual analogue scale. In a randomly assigned, crossover design, the effectiveness of the endoscopically (e) inserted ITO catheter was assessed by measuring the capillary blood gases, respiratory rate (RR), tidal volume (V_t) and minute ventilation (MV) after 1 h breathing room air without eITO and 1 h after eITO (flow: 3 l/min). Measurements and results: The eITO catheter was placed in all patients without complications and with only minimal discomfort in two patients (spontaneously reversible cough). Compared to breathing room air, capillary O₂ pressure increased (from 54.7 ± 9.4 to 82.8 ± 21.8 mmHg) whereas V_t (from 458.7 ± 86.8 to 358.3 ± 75.1 ml) and MV (from 7.7 ± 1.5 to 5.5 ± 1.1 l/min) decreased significantly (each p < 0.0001) with eITO in all patients. The capillary CO₂ pressure and RR did not change. Conclusions: Acutely extubated patients in whom oxygen therapy is indicated may profit from eITO. This new technique works immediately and is thus an effective short-term intervention of potential value in the intensive care unit. Received: 6 September 1996 Accepted: 2 January 1997     

下尿路超声尿动力学研究:女性压力性尿失禁尿道膀胱连接部移动度和压力传导比关系的同步观察

目的 探讨超声尿动力学技术应用于女性压力性尿失禁诊断的初步结果。方法 对３０例压力性尿失禁患者和２２例正常人作超声尿动力学检查,测量连接部移动度和尿道膀胱压,计算压力传导比,并作统计学处理。结果 尿失禁组和正常组之间解剖参量连接部移动度和功能参量压力传导比存在显著的差异。尿失禁组阅移动度明显大于正常组。尿失禁组压力传导比明显低于正常组。连接部移动度和压力传导比存在负相关关系（ｒ＝－０．５８,Ｐ＝０     

Clinical value of hepatic vein catheterization

Techniques of hepatic vein catheterization, hepatic venous pressure measurement, and occlusion phlebography using a balloon catheter are described.Hepatic venous pressure measurements (n=95) and hepatic occlusion phlebography were combined in 32 cases.In patients with liver cirrhosis (n-63) a significant elevation of hepatic venous pressure gradients was found. A decrease of the pressure gradient was seen after portacaval and splenorenal shunt operations.Hepatic occlusion phlebography showed alterations of hepatic veins only in patients with cirrhosis. A rough correlation between pressure gradients and the extent of changes in the liver veins was found. Hepatic occlusion phlebography, in patients who had undergone shunt procedure, demonstrated various collaterals.Combined hepatic vein pressure measurements and hepatic occlusion phlebography using a balloon catheter are proposed as a very suitable method for the evaluation of chronic liver disease and portal hypertension.     

Myocardial perfusion imaging using a non-contrast agent MR imaging technique

Introduction: A MR imaging (MRI) method has been developed to determine quantitatively myocardial perfusion (P) in the rat heart in vivo. This method has the potential to non-invasively measure cardiac perfusion without the use of a contrast agent by exploiting the endogenous contrast from flowing blood itself. Method and Results: Principle of the technique is the arterial spin labeling of endogenous water protons within the short axis imaging slice. Arterial spin labeling techniques are based on a model that uses inflow effects to relate intrinsic changes in longitudinal relaxation (T ₁) to tissue perfusion. Perfusion is determined from the difference between a slice selective and a global inversion recovery experiment. Perfusion was determined at rest and during hyperemia induced by intravenous adenosine (3 mg/(kgmin)). The MR perfusion values were compared with perfusion data obtained in the same animal using the colored microspheres (MS) technique as the gold standard. The MR perfusion (mean ± SEM) was 3.3 ± 0.2 ml/min/g at rest and 4.6 ± 0.6 ml/min/g during adenosine. Perfusion values obtained by colored MS were 3.4 ± 0.2 and 4.7 ± 0.8 ml/min/g at rest and during vasodilation, respectively. Adenosine decreased mean arterial pressure (MAP) from 120 to 65 mmHg which implies a reduction of coronary resistance (CR) to about 50% of baseline. Conclusion: Our study shows that quantitative mapping of perfusion may be performed non-invasively by MRI. The MR perfusion data are in excellent correlation with data obtained by the well-established colored MS technique. Determination of perfusion reserve confirms that coronary perfusion is highly dependent on blood pressure due to changes in CR.     

Development and evaluation of a self-regulating alternating pressure air cushion

Purpose: To investigate the effect of alternating air cells of a newly developed dynamic cushion on interface pressure and tissue oxygenation levels. Method: This cross-over experimental study included 19 healthy volunteers. The dynamic cushion used has an automatic self-regulating alternating pressure air-cell system with 35 small and four large air cells for maintaining posture while seated. This cushion also has 17 bottoming-out detectors that automatically inflate the air cells to release a high interface pressure. To assess the effect of this alternating system, participants sat on the new cushion with an alternating system or static system for 30?min and then performed push-ups. The interface pressure was monitored by pressure-sensitive and conductive ink film sensors and tissue oxygenation levels were monitored by near-infrared spectroscopy. A reactive hyperaemia indicator was calculated using tissue oxygenation levels as an outcome measure. Results: The peak interface pressure was not significantly different between the groups. The reactive hyperaemia indicator was significantly higher in the static group than in the alternating group. Conclusions: An alternating system has beneficial effects on blood oxygenation levels without increasing interface pressure. Therefore, our new cushion is promising for preventing pressure ulcers with patients with limited ability to perform push-ups.

• Implications for Rehabilitation

• A dynamic cushion was developed, which consists of a uniquely-designed air-cell layout, detectors for bottoming out, and an alternating system with multiple air-cell lines.

• The alternating system did not increase interface pressure and it significantly reduced reactive hyperaemia after 30?min of sitting in healthy volunteers.

• This cushion is a new option for individuals who require stable posture but have limitations in performing scheduled push-ups for prevention of pressure ulcers.

     

Evaluation of a regional oxygen saturation catheter for monitoring SJVO2 in head injured patients

Objectives. Monitoring jugular venous oxygen saturation (SjvO₂) has been useful for the early identification and treatment of cerebral ischemia in patients with severe head injury. However, the catheters that have been used for this purpose have not performed optimally. The purpose of this study was to evaluate the performance of a new regional oxygen saturation catheter for monitoring SjvO₂.Methods. Eighteen regional oxygen saturation catheters, 4-Fr in diameter (Baxter Healthcare Corporation, Edward Critical Care), were used in this study. Each catheter was inserted percutaneously into the dominant jugular vein and the catheter's tip position in the jugular bulb was verified by radiograph. The catheter was calibratedin vitro prior to insertion using the optic calibrator provided by the manufacturer. The catheter was recalibrated every 8 to 12 hours by comparing the oxygen saturation value from the catheter with that measured by a cooximeter in a blood sample drawn through the catheter.Results. In vitro calibration using the optic calibrator was not always successful. Five catheters could not be calibrated. The remaining 13 catheters could all be calibrated, but only 9 provided a value that was within 4% of the oxygen saturation derived from the blond sample. After the firstin vivo calibration, the correlation between the catheter and the blond sample values was improved. A total of 196 comparisons were made. The median, 25th, and 75th quartile differences between the catheter and the blond sample measurement of SjvO₂ were 0.00, −1.15, and 1.25%, respectively. Using longitudinal data regression, the overall slope of the regression between the catheter and blood values was 0.997 (p = 0.001).Conclusions. The new regional oxygen saturation catheter provided reliable measurement of SjvO₂ 83% of the time when the signal quality index was ≤3, and may be useful for continuous monitoring of SjvO₂. This work was supported by NIH grant #PO1-NS26716.     

Transcranial Doppler monitoring compared with invasive monitoring of intracranial pressure during acute intracranial hypertension

Objective. To determine whether a simple transcranial Doppler waveform variable–pulsatility difference (systolic - diastolic blood flow velocity) can serve as a measure of critical changes in cerebral perfusion. Methods. Thirteen pigs were anesthetized (anesthesia maintained with halothane) and ventilated to maintain normoxia and normocarbia. To measure mean arterial pressure, hemoglobin, and blood gases, the right carotid artery was cannulated. The right intracranial lateral ventricle was cannulated to measure and increase intracranial pressure; the right internal jugular vein was cannulated in 8 of 13 pigs to measure jugular venous oxygen saturation and to calculate cerebral arteriovenous oxygen content difference. Intracranial pressure was also monitored continuously with a subdural bolt in the contralateral frontal region, and blood flow velocity in the middle cerebral artery was measured with a transcranial Doppler probe on the right orbital region. Intracranial pressure was increased in increments of 10 to 20 mmHg by infusing saline through the ventriculostomy catheter until the transcranial Doppler indicated that blood flow velocity had ceased, at which point all variables were allowed to return to baseline. If mean arterial pressure failed to return to baseline, epinephrine, 0.01 to 0.1 µg/kg/min, was infused. Useful data were obtained from 8 pigs and were analyzed separately for pigs that received epinephrine (n = 4) and those that did not (n = 4). Results. Transcranial Doppler measurements correlated more closely with cerebral perfusion pressure = (mean arterial pressure – intracranial pressure) than with intracranial pressure. In the range of 30 to 60 mmHg, cerebral perfusion pressure correlated linearly with the pulsatility difference. The closest nonlinear correlation (third order polynomial relationship) was noted between cerebral perfusion pressure and pulsatility difference (r = 0.8, P < 0.001, n = 217), for the animals that did not receive epinephrine. When a cerebral perfusion pressure <60 mmHg and a cerebral arteriovenous oxygen content difference >6.5 vol% were used to define limits of abnormal, pulsatility difference was a sensitive and specific indicator of abnormality in either variable. Pulsatility difference of >70 cm/sec had >77.1% and 86.7% positive accuracy rate, and <0% and 14.3% negative accuracy rate for abnormal cerebral perfusion pressure (CPP) and cerebral arterio-venous O₂ (C[a-v]O₂), respectively. Conclusions. In pigs with induced diffuse intracranial hypertension, noninvasive transcranial Doppler waveform monitoring of pulsatility difference can identify increased cerebral oxygen extraction and dangerously decreased cerebral perfusion pressure.     

Non-invasive estimation of cardiac output in critical care patients

Objective.This study was carried out to compare cardiac output measurements determined by thermodilution and by Portapres, a non-invasive system. Design, patients and setting.Eighty-seven non-invasive blood pressure measurements were performed in 46 patients in our critical care unit utilising the new, non-invasive Portapres system. Cardiac output values were obtained from these blood pressure values using an aortic impendance model and compared to cardiac output values estimated by the thermodilution technique.Measurements and main results.Statistically significant (p< 0.01) differences (2.3 l/min; limits of agreement ± 5l/min) were noted between invasive and non-invasive cardiac output measurements. Differences in measured cardiac outputs increased for patients receiving catecholamine therapy, in patients with hemodynamic instability(e.g., sepsis and cardiac insufficiency), in patients with artificial ventilation, in patients with long duration of intensive care, in younger(<60 yr) patients and in women. We found no influence of the body mass index (BMI) on the accuracy of Portapres results. In only one single subgroup,10 patients with pulmonary diseases, Portapres measurements were not statistically significant different from reference results. Conclusions.To date, Portapres measurements cannot replace thermodilution cardiac output estimations. Fluctuations of finger arterial perfusion due to hemodynamic instability, hypothermia and catecholamines may be responsible for problems of Portapres use in critically ill patients. This revised version was published online in July 2006 with corrections to the Cover Date.     

Sonorectovaginography: A New Sonographic Technique for Imaging of the Posterior Compartment of the Pelvis

Objective. We describe the use of a new sonographic technique for imaging of the posterior compartment of the pelvis: sonorectovaginography. Methods. Sonorectovaginography uses instillation of fluids (saline solution and ultrasound gel) in the vagina, pouch of Douglas, and rectum for the purpose of creating acoustic interfaces between the vagina, cervix, rectum, and pouch of Douglas. We performed sonorectovaginography in a woman with chronic pelvic pain during laparoscopy. Urinary catheters were introduced into the rectum and vagina. Sterile saline solution was introduced into the abdominal cavity through a laparoscopic trocar and in the rectum via a rectal catheter. The transvaginal probe was then inserted, and sterile ultrasound gel was introduced into the vagina through the vaginal catheter under sonographic guidance. Results. Sonorectovaginography has helped us create acoustic interfaces and enhanced simultaneous visualization of the vaginal walls, posterior vaginal fornix, retrocervical area, rectovaginal septum, rectal wall, and pouch of Douglas. Conclusions. Imaging of the posterior compartment of the pelvis is of paramount importance for identification of potentially difficult endometriosis cases, such as those complicated by obliteration of the pouch of Douglas or infiltration of the retrocervical area, rectovaginal septum, or vaginal or rectal wall. Sonorectovaginography may prove helpful in evaluating this compartment of the pelvis in women with suspected deep endometriosis. Its reproducibility, tolerability, and accuracy, however, need to be validated prospectively, and normative data for the rectovaginal septum also need to be established.