Continuous Pressure Monitoring Research Articles

Efficacy and Safety of Bosentan Treatment for Portopulmonary Hypertension Associated With Syncope

Pulmonary arterial hypertension (PAH) in patients with portal hypertension is also referred to as portopulmonary hypertension (PPHTN). Here, we report a case of PPHTN caused by alcoholic liver cirrhosis in a 43-year-old male who experienced repetitive syncope on exertion. The continuous monitoring of pulmonary artery pressure and radial artery pressure revealed that his PAH was aggravated with a drop in systemic arterial pressure during an exercise test. Bosentan, an endothelin A/B receptor antagonist, improved the patient's hemodynamic parameters and abolished his syncope without adverse effects. This is the first report that bosentan may be effective and safe for PPHTN associated with syncope.

Recovery of Absolute Gas Absorption Line Shapes Using Tuneable Diode Laser Spectroscopy with Wavelength Modulation ¿ Part I: Theoretical Analysis

Tunable diode laser spectroscopy is extremely important for gas detection in a wide variety of industrial, safety and environmental monitoring applications. Of particular interest is the development of calibration-free, stand-alone systems and instrumentation which can operate in high-temperature or high-pressure environments (such as in fuel cells, or gas turbine engines) where continuous and simultaneous monitoring of pressure, temperature and concentration of gases may be required. Here, in Part 1 of this two-part paper, we present the full theoretical basis and range of techniques for calibration-free line-shape recovery to allow simultaneous measurements of concentration and pressure/temperature for a wide range of potential applications. Firstly, on the basis of Fourier analysis, we present the general signal components that arise with both intensity and frequency modulation of diode lasers and identify the issues and difficulties associated with accurate line-shape recovery in conventional wavelength modulation spectroscopy (WMS). We then show how line-shape recovery may be effectively performed using first harmonic signals and, by use of a general correction function from Fourier coefficients, we extend the techniques previously reported to include arbitrary large modulation indices, different line-shape profiles and high gas concentration with non-linear absorption. Previous approximate techniques based on Taylor series expansions are included as a special case of the Fourier analysis for low modulation indices. We also show that the signal amplitudes obtained in this way can be comparable to, or even exceed, that of conventional WMS by appropriate choice of the modulation index and frequency.

Balloon occlusion of the right main bronchus in an ovine model provides sufficient time for emergent interventions in massive pulmonary embolism

Massive pulmonary embolism (PE) causes hemodynamic compromise and is associated with a high rate of mortality. We sought to create a model of massive PE and to determine whether occlusion of the right main bronchus could mitigate the physiological effects of massive PE in this model. We used 27 female sheep to generate a model of massive PE by either autologous blood clot injection (n=18) or detachable balloon release (n=9) into the right main pulmonary artery. Four sheep were excluded after blood clot injection, as they did not exhibit adequate declines in blood oxygen saturation (SaO(2)). Nine of the sheep that received autologous blood clot and nine that received detachable balloons went on to treatment with right main bronchus occlusion. The control group (n=5) received the autologous blood clot, but no occlusion of the right main bronchus. All sheep underwent continuous monitoring of pulmonary arterial mean pressure (PAMP), SaO(2), arterial partial pressure of oxygen (PaO(2)), and arterial partial pressure of carbon dioxide. Twenty-three sheep (85%) subjected to PE demonstrated immediate tachycardia, tachypnea, and decline in SaO(2) of at least 25% within 30 min. After right main bronchus occlusion, 18 sheep (100%) survived for the length of the experiment and exhibited persistently higher SaO(2) and PaO(2) levels, as well as decreased PAMP compared with the controls. In the control group, two out of five sheep died within 30 min, and the three surviving subjects demonstrated significantly decreased SaO(2) and PaO(2) levels. Occlusion of the right main bronchus in an ovine model of massive PE effectively extends life and provides favorable physiological parameters to allow emergent interventions.

Continuous Intraocular Pressure Monitoring by Means of the Sensimed Triggerfish® System

Intraocular pressure (IOP), like other biological parameters, has a 24-hour rhythm with physiological oscillations around 5mmHg. Recently, it has been demonstrated that IOP fluctuations represent an independent parameter for progression of glaucoma. The most common clinical methods able to detect the diurnal state of IOP are the tonometric curve (with IOP measurements taken from 9:00 am to 20:00 pm) or two provocative tests, such as the water drinking test (WDT) and the ibopamine test. Recently introduced in clinical practice, the Sensimed Triggerfish® is a system enabling continuous IOP monitoring based on a disposable contact lens with a sensor linked to a telemetric microprocessor. The purpose of this project was to investigate the clinical applicability of the system as an additional tool, providing useful information for the management of glaucoma patients. Of eight evaluated patients, two cases are presented in detail in this report. The monitoring system that provides 24-hour continuous data appears to be very promising, as it captures clinically useful, real-life IOP fluctuations day and night while patients maintain normal activities, including undisturbed sleep.

Implantable Sensors for Heart Failure

Heart failure (HF) affects more than 5 million Americans, and acute decompensated heart failure (ADHF) has emerged as the leading cause of hospitalization among people over the age of 65 years.1 Importantly, HF is a leading public health concern, and hospitalization expenses related to management of ADHF impose a substantial financial burden on the health care system. Additionally, readmission rates after hospitalization for ADHF may be as high as 50% at 6 months,2 and insights from the ADHERE registry suggest that a majority of patients admitted with ADHF have a history of heart failure.1 These data demonstrate that the majority of patients admitted with ADHF are known to the medical system and to medical providers, thereby creating an opportunity for upstream strategies that may be capable of detecting early HF destabilization and implementing therapies to restabilize the patient and avert hospitalization. The anticipated changes in the health care system—with a focus on bundled payments for disease management—will necessitate robust disease management programs to optimize therapy and minimize recurrent admissions once patients have been diagnosed with HF. Perhaps even more importantly, averting repeat episodes of ADHF is likely to have a stabilizing effect on the progression of HF and may improve long-term morbidity and mortality. The transition from chronic HF to ADHF involves perturbations in multiple intersecting processes including neurohormonal circuits, inflammatory mediators, cardiorenal interactions, and myocardial performance. Concurrently, derangements in comorbid illnesses such as coronary disease, atrial and ventricular arrhythmias, and hypertension also contribute to the pathophysiology of ADHF.3 Ultimately, these multiple pathways lead to an elevation in ventricular filling pressures and signs of vascular congestion, which, in concert with symptoms from impaired cardiac output, lead to the clinical constellation of ADHF. This pathophysiologic paradigm highlights multiple opportunities for detecting early changes in the processes that …

Four-limb compartment syndrome associated with the systemic capillary leak syndrome

Systemic capillary leak syndrome, or the Clarkson syndrome, is an extremely rare condition in which increased capillary permeability results in a massive shift of fluid into the extravascular space. This is followed rapidly by hypotensive shock, haemoconcentration, and, potentially, substantial oedema of the limbs resulting in an acute compartment syndrome. It is important for orthopaedic surgeons to be aware of this syndrome as our medical colleagues, who initially care for these patients, are less familiar with the diagnosis and the need for emergency management of the associated compartment syndrome should it develop. There have been fewer than 100 cases of this entity reported. This case report is the first to describe the subsequent development of a compartment syndrome in all four limbs. Clinical vigilance and continuous monitoring of intracompartmental pressure is necessary in these patients in order to help reduce limb-threatening complications.

Heart Rate and Pulse Pressure Variability are Associated With Intractable Intracranial Hypertension After Severe Traumatic Brain Injury

Calculation of integer heart rate variability (HRVi) permits monitoring over extended periods. We asked whether continuous monitoring of HRVi or integer pulse pressure (PP) variability (PPVi) could predict intracranial hypertension, defined as ICP >20 mm Hg, cerebral hypoperfusion, defined as CPP<60 mm Hg, mortality or functional outcome after severe traumatic brain injury. Dense integer data collected during continuous intensive care unit monitoring for periods of 1 to 11 days on 25 patients admitted to our Level I trauma center with Glasgow Coma Scale <9 provided 1,715,000 data points over a mean 106±62 hours. PP, HRVi, and PPVi increased in response to increasing ICP when CPP >60 mm Hg (P<0.001), but HRVi and PPVi decreased when CPP <60 mm Hg and P<50 mm Hg, even with ICP <20 mm Hg (P<0.001). ICP up to 40 mm Hg still evoked an increase in HRVi and PPVi (P<0.001), but both were suppressed with CPP <50 mm Hg and ICP >40 mm Hg (actual or impending brain death). Mean HRVi and PPVi predicted in-hospital mortality (sensitivity, 67%; specificity, 91% to 100%). Combining HRVi and PPVi as an "autonomic index" (AI) best predicted long-term functional outcome [Area Under the Curve: 0.84±0.08 for AI <0.5]. Our data show that HRVi and PPVi can be monitored and calculated automatically and can provide useful prognostic information in patients with severe traumatic brain injury, particularly when combined into a single index.

Continuous non-invasive finger arterial pressure monitoring reflects intra-arterial pressure changes in children undergoing cardiac surgery

BackgroundContinuous non-invasive measurement of finger arterial pressure (FAP) is a reliable technology in adults. FAP is measured with an inflatable cuff around the finger and simultaneously converted to a reconstructed brachial artery pressure waveform (reBAP) by the Nexfin™ device. We assessed the adequacy of a prototype device (Nexfin-paediatric), designed for a paediatric population, for detecting rapid arterial pressure changes in children during cardiac surgery. MethodsThirteen anaesthetized children with a median age of 11 months (2 months–7 yr) undergoing congenital cardiac surgery were included in the study. reBAP and intra-arterial pressure (IAP) were recorded simultaneously during the surgical procedure. To assess the accuracy of reBAP in tracking arterial pressure changes, the four largest IAP variations within a 5 min time interval were identified from each procedure. These variations were compared offline with reBAP during a 10 s control period before and a 10 s period after an arterial pressure change had occurred. ResultsIn 10 out of 13 children, a non-invasive arterial pressure recording could be obtained. Therefore, recordings from these 10 children were eligible for further analysis, resulting in 40 data points. The correlation coefficient between reBAP and IAP in tracking mean arterial pressure (MAP) changes was 0.98. reBAP followed changes in IAP with a mean bias for systolic, diastolic arterial pressure, and MAP of 0.0 mm Hg (sd 5.8), 0.1 (sd 2.8), and 0.19 (sd 2.7), respectively. ConclusionsThe prototype device closely follows arterial pressure changes in children. However, in a considerable number of attempts, obtaining a signal was time-consuming or unsuccessful. This technique seems promising but requires further technical development.

Precision and accuracy of a new device (CNAP™) for continuous non-invasive arterial pressure monitoring: assessment during general anaesthesia

BackgroundContinuous non-invasive arterial pressure measured with CNAP™ (CNAP) has been shown to be superior to intermittent oscillometric measurements during procedural sedation and spinal anaesthesia. We assessed the performance of CNAP during general anaesthesia by analysis of agreement with invasive measurements of arterial pressure (AP). MethodsEighty-eight patients undergoing elective abdominal surgery, cardio-, or neurosurgery were included in the study. Systolic, diastolic, and mean AP measured by an intra-arterial catheter in the radial artery (IAP) were compared with those obtained by CNAP from the same arm. Data were analysed to determine the precision (i.e. measurement error) and accuracy (i.e. systematic error) of beat-to-beat CNAP values with respect to IAP. Also, we compared the frequency of fast changes in AP (FCAP) and hypotension (IOH) by both methods. ResultsCNAP precision of 4.5, 3.1, and 3.2 mm Hg (systolic, diastolic, and mean AP, respectively) was not significantly different from IAP precision, and CNAP accuracy was +6.7, −5.6, and −1.6 mm Hg. The frequency of AP pairs having a difference within the calculated limits of agreement was 81%, 64%, and 76% for systolic, diastolic, and mean AP, respectively. The calculated limits of agreement were ±17.6, ±11.4, and ±12.0 mm, Hg, respectively. CNAP and IAP detected simultaneously to 82.1% FCAP and to 84.6% IOH. ConclusionsCNAP provides real-time estimates of arterial pressure comparable with those generated by an invasive intra-arterial catheter system during general anaesthesia.

Investigating shunt function using continuous intracranial pressure monitoring in adults: single center experience

Managing symptomatic ventriculoperitoneal shunts with no clear evidence of shunt malfunction either clinically or radiologically can be a difficult task. The aim of this study was to assess intracranial pressure (ICP) monitoring as a method of investigating shunt function. The authors performed a retrospective analysis of 38 continuous ICP monitoring procedures done in patients with ventriculoperitoneal shunts and suspected shunt malfunction. Thirty-eight procedures were performed in 31 patients between January 2005 and October 2008. Sixteen recordings were normal, 6 revealed overdrainage or low pressure, 11 indicated underdrainage or high pressure, and 5 showed variable shunt function. Based on the findings after 20 procedures (53%), patients were treated conservatively: 4 by readjusting the valve setting and 16 by referral to the headache neurologist for medical treatment. Forty-five percent of the conservatively treated patients improved. Surgical exploration was undertaken following 18 procedures (47%); 72% of the surgically treated patients improved. Continuous ICP monitoring using an intraparenchymal probe is a safe and effective method of investigating adult hydrocephalus.

Acute Lung Injury Is an Independent Risk Factor for Brain Hypoxia After Severe Traumatic Brain Injury

Pulmonary complications are frequently observed after severe traumatic brain injury (TBI), but little is known about the consequences of lung injury on brain tissue oxygenation and metabolism. We examined the association between lung function and brain tissue oxygen tension (PbtO2) in patients with severe TBI. We analyzed data from 78 patients with severe, nonpenetrating TBI who underwent continuous PbtO2 and intracranial pressure monitoring. Acute lung injury was defined by the presence of pulmonary infiltrates with a PaO2/FiO2 (PF) ratio less than 300 and the absence of left ventricular failure. A total of 587 simultaneous measurements of PbtO2 and PF ratio were examined using longitudinal data analysis. PbtO2 correlated strongly with PaO2 and PF ratio (P < .05) independent of PaCO2, brain temperature, cerebral perfusion pressure, and hemoglobin. Acute lung injury was associated with lower PbtO2 (34.6 +/- 13.8 mm Hg at PF ratio >300 vs 30.2 +/- 10.8 mm Hg [PF ratio 200-300], 28.9 +/- 9.8 mm Hg [PF ratio 100-199], and 21.1 +/- 7.4 mm Hg [PF ratio <100], all P values <.01). After adjusting for intracranial pressure, Marshall computed tomography score, and APACHE II (Acute Physiology and Chronic Health Evaluation) score, acute lung injury was an independent risk factor for compromised PbtO2 (PbtO2 <20 mm Hg; adjusted odds ratio: 2.13, 95% confidence interval: 1.21-3.77; P < .01). After severe TBI, PbtO2 correlates with PF ratio. Acute lung injury is associated with an increased risk of compromised PbtO2, independent from intracerebral and systemic injuries. Our findings support the use of lung-protective strategies to prevent brain hypoxia in TBI patients.

Wireless Intraocular Pressure Sensing Using Microfabricated Minimally Invasive Flexible-Coiled LC Sensor Implant

This paper presents an implant-based wireless pressure sensing paradigm for long-range continuous intraocular pressure (IOP) monitoring of glaucoma patients. An implantable parylene-based pressure sensor has been developed, featuring an electrical LC-tank resonant circuit for passive wireless sensing without power consumption on the implanted site. The sensor is microfabricated with the use of parylene C (poly-chloro-p-xylylene) to create a flexible coil substrate that can be folded for smaller physical form factor so as to achieve minimally invasive implantation, while stretched back without damage for enhanced inductive sensor-reader coil coupling so as to achieve strong sensing signal. A data-processed external readout method has also been developed to support pressure measurements. By incorporating the LC sensor and the readout method, wireless pressure sensing with 1-mmHg resolution in longer than 2-cm distance is successfully demonstrated. Other than extensive on-bench characterization, device testing through six-month chronic in vivo and acute ex vivo animal studies has verified the feasibility and efficacy of the sensor implant in the surgical aspect, including robust fixation and long-term biocompatibility in the intraocular environment. With meeting specifications of practical wireless pressure sensing and further reader development, this sensing methodology is promising for continuous, convenient, direct, and faithful IOP monitoring.

Hemodynamic Stability During Biventricular Pacing After Cardiopulmonary Bypass

To assess the stability of cardiac output, mean arterial pressure, and systemic vascular resistance during biventricular pacing (BiVP) optimization. Substudy analysis of data collected as part of a randomized controlled study examining the effects of optimized temporary BiVP after cardiopulmonary bypass (CPB). A single-center study at a university-affiliated tertiary care hospital. Cardiac surgery patients at risk of left ventricular failure after CPB. BiVP was optimized immediately after CPB. Atrioventricular delay (7 unique settings) was optimized first, followed by the left ventricular pacing site (3 unique settings) and then the interventricular delay (9 unique settings). Each setting was tested twice for 10 seconds each time. Vasoactive medication and fluid infusion rates were held constant. Aortic flow velocity and radial artery pressure were digitized, recorded, and averaged over single respiratory cycles. Least squares and linear regression/Wilcoxon analyses were applied to the first 7 patients studied. Subsequently, curvilinear analysis was applied to 15 patients. Changes in mean arterial pressure and systemic vascular resistance were statistically insignificant or too small to be meaningful by least squares analysis. During interventricular synchrony optimization, cardiac output and mean arterial pressure decreased (mean changes -5.7% and -2.5%, respectively; with standard errors 2.3% and 1.5%, respectively), whereas SVR increased (mean change 3.1% with standard error 3.4%). Only the change in cardiac output was statistically significant (p = 0.043). Curvilinear fits to data for 15 patients demonstrated progressive hemodynamic stability over the total testing period. BiVP optimization may be done safely in patients after CPB. With continuous monitoring of mean arterial pressure and cardiac output, the procedure results in no harmful hemodynamic perturbation.

Continuous intracranial pressure monitoring in pseudotumour cerebri: Single centre experience

Objective. Investigating pseudotumour cerebri (PTC) patients who do not fulfil the diagnostic criteria, or those presenting post-shunt insertion with recurrent symptoms and signs, with no clear evidence of shunt malfunction, present a diagnostic challenge. PTC patients who underwent continuous intracranial pressure (ICP) monitoring in our unit were reviewed retrospectively.Results. Twenty-six ICP monitoring procedures were done on 20 patients. Eleven patients had normal pressure, 2 overdrainage/low pressure, 11 underdrainage/high pressure and 2 variable pressures. On the basis of these results 12 patients were managed conservatively: 11 patients were referred to headache team and 1 patient had readjustment of an adjustable valve shunt setting; of those 3 patients had improved symptoms on their first post-operative clinic review. On the other hand, 14 patients had surgery: 5 had shunt revision and 9 had shunt insertion; of those 5 patients improved.Conclusion. ICP monitoring using an intraparenchymal probe is a safe and effective diagnostic technique in investigating PTC when indicated. A multidisciplinary approach achieves best results in terms of successful management and follow-up.

De Motu Cerebri: The History of the Study of Brain Pulsations

Pulsations of the brain were observed and noted since antiquity. Galenic concepts that the brain pulsations pro- pel psychic pneuma to the nerves were challenged during the Renaissance and replaced by other theories. During the age of the Enlightenment, scientists began to study by observation and experiment whether these pulsations were generated by the dura mater, the respiratory movements or the beating of the heart through the arteries and the veins. The research ef- forts then moved to find out whether the pulsations were an innate physiological phenomenon or whether they appeared only when the skull was opened. The devices developed during the first half of the nineteenth century, enabled observing the brain while preserving the conditions of an unopened skull. They are the prototypes of nowadays instruments in clini- cal use. The invention of the kymograph transformed the naked eye impressions into records that were open to objective analysis, and established the close relation between the arterial pulse and its components to the waveform of the cerebral move- ments. By the end of the nineteenth century, the study of the brain movements was coupled with the extensive research of the cerebral circulation, emotional conditions and the physiology of intracranial pressure; however, this endeavor was abandoned for many decades. As continuous monitoring of intracranial pressure in the late 1970s became a routine clinical practice, the three-centuries- old research of brain pulsations was resumed with the not yet fulfilled aspiration to employ wave-form analysis of the pulsations as a means for non-invasive assessment of intracranial pressure.

A Wireless Embedded Sensor based on Magnetic Higher-order Harmonic Fields: Application to Liquid Pressure Monitoring.

A wireless sensor based on the magnetoelastic, magnetically soft ferromagnetic alloy was constructed for remote measurement of pressure in flowing fluids. The pressure sensor was a rectangular strip of ferromagnetic alloy Fe(40)Ni(38)Mo(4)B(18) adhered on a solid polycarbonate substrate and protected by a thin polycarbonate film. Upon excitation of a time-varying magnetic field through an excitation coil, the magnetically soft sensor magnetized and produced higher-order harmonic fields, which were detected through a detection coil. Under varying pressures, the sensor's magnetoelastic property caused a change in its magnetization, altering the amplitudes of the higher-order harmonic fields. A theoretical model was developed to describe the effect of pressure on the sensor's higher order harmonic fields. Experimental observations showed the 2(nd) order harmonic field generated by the pressure sensor was correlated to the surrounding fluid pressure, consistent with the theoretical results. Furthermore, it was demonstrated that the sensor exhibited good repeatability and stability with minimal drift. Sensors with smaller dimensions were shown to have greater sensitivity but lower pressure range as compared to their larger counterparts. Since the sensor signal was also dependent on the location of the sensor with respect to the excitation/detection coil, a calibration algorithm was developed to eliminate signal variations due to the changing sensor location. Because of its wireless and passive nature, this sensor is useful for continuous and long-term monitoring of pressure at inaccessible areas. For example, sensors with these capabilities are suitable to be used in biomedical applications where permanent implantation and long-term monitoring are needed.

Intracranial hypertension, headache and obesity: Insights from magnetic resonance venography

Idiopathic intracranial hypertension without papilloedema (IIHWOP) is uncommon, accounting for, at most, 5% of patients with IIH evaluated by neuroophthalmologists (1). In contrast to patients with IIH and papilloedema, patients with IIHWOP are less obese, have lower cerebrospinal fluid pressures, and are more likely to have non-organic visual loss (1). This entity is perhaps more readily diagnosed among headache specialists than neuro-ophthalmologists and is suspected in obese women with intractable or chronic daily headaches (2). The integral relationship between the central venous system and intracranial pressure has been emphasised over the past several years with the discovery of venous sinus abnormalities in patients with IIH (3). Morphological irregularities and abnormal pressure gradients within the transverse sinuses are well described. In most cases, transverse venous sinus stenosis appears to be a result of high intracranial pressure rather than its cause (4). The transverse sinuses are asymmetric in most individuals and a unilateral hypoplastic sinus is considered a normal variant. However, bilateral transverse sinus stenosis (BTSS) may be associated with intracranial hypertension. In this issue of Cephalalgia, Bono and colleagues studied 98 patients with chronic migraine and chronic tension type headache using magnetic resonance venography and 1-h continuous lumbar CSF pressure monitoring (5). Their findings are notable in several respects. Strikingly, their patients were obese, regardless of CSF pressure status. Patients with normal CSF pressure (Group 1) were less overweight than in the groups with either intermittently (Group 2) or consistently (Group 3) elevated CSF pressure, and some patients in Group 1 had a normal body mass index (BMI), but overall this cohort was overweight. There was no different in BMI between subjects in Groups 2 and 3. Obesity is a risk factor for both IIH and the development of chronic daily headache (6). Although there was a statistically significant difference in both mean CSF pressure and opening pressure between the three groups, only some of the patients in Group 3 met criteria for the diagnosis of IIH by current standards (7). Pressures between 201–249mm CSF are non-diagnostic (8). BTSS has been noted in a majority of patients with IIH by various investigators. It is less commonly encountered in a typical practice setting, even in patients with papilloedema. The high prevalence of BTSS in this cohort is perhaps attributable to the imaging technique used, which the investigators previously found to have a very high detection rate of transverse sinus stenosis (three dimensional phase contrast images with 15 cm/s velocity encoding). Conventional MR venography is often performed using two dimensional time of flight, and the images are likely subjected to less scrutiny in the practice setting than the research setting. All subjects in Groups 2 and 3 had BTSS, whereas only four of 54 patients in group 1 had BTSS. As previously noted, unilateral transverse sinus stenosis was not associated with abnormal intracranial pressure. One-hour monitoring showed mean pressures that were consistently higher than the opening pressure in all groups. The importance of this finding cannot be overemphasised. An isolated CSF pressure measurement is but a ‘snapshot in time’ and may be spuriously high or low, depending on the situation and technique employed. Prolonged monitoring also revealed B-waves in Groups 2 and 3; B-waves are frequently recorded with increased intracranial pressure of various aetiologies, although there is far greater experience defining pressure wave abnormalities with intracranial pressure monitoring systems than with lumbar recording methods. Digre and colleagues (1) found that treatment of patients with IIHWOP with agents conventionally

Successful use of the HeartWare HVAD rotary blood pump for biventricular support

Left ventricular assist devices (LVADs) using rotary blood pump technology led to significant improvement of results in left ventricular failure. 1 However, patients with concomitant right ventricular failure have not benefited from this new technology so far. We report on the first successful use of 2 HeartWare HVAD centrifugal pumps (HeartWare International, Inc, Framingham, Mass) in biventricular support. CLINICAL SUMMARY A 56-year-old man was referred to our institution after massive myocardial infarction owing to occlusion of the left anterior descending coronary artery (LAD) (maximum creatine kinase MB 1300 units). He had been treated with grafts to the LAD, the first diagonal, and the right coronary artery (RCA) and was in cardiogenic shock. An intra-aortic balloon pump (IABP) and a femorofemoral extracorporeal membrane oxygenator (ECMO) were implanted after weaning from extracorporeal circulation failed. The patient was transported to our center after 2 days in an extubated stable state. An LVAD was implanted using a standard approach under ECMO support. All bypass grafts were intact; however, right ventricular dysfunction led to the decision not to explant the ECMO or the IABP at this time. The IABP was removed the following day, and the ECMO was explanted on postoperative day 4 when renal and liver parameters remained normal. The patient was treated with phosphodiesterase inhibitor and nitric oxide. Sedation was instituted for another 3 days, and then weaning from ventilatory support was started. At this time the compensated right ventricular insufficiency turned into refractory right ventricular failure inducing renal insufficiency and impairment of liver function. A new ECMO was inserted on postoperative day 11. Again, end-organ function recovered, but right heart failure persisted as indicated by echocardiographic findings for another 10 days, and the decision was made to implant a second HVAD device to support the right ventricle. With the patient still supported by ECMO, the anterior wall of the right ventricle was chosen for implantion of the inflow of the device. The sewing ring was placed epicardially. Care was taken not to insert the whole length of the inflow cannula, but only about 1 cm into the cavity of the ventricle. The location of the device was stabilized by the epicardial sewing ring. The bend relief was removed and after partial clamping the outflow graft was sewn end to side to the main pulmonary artery (Figure 1). For continuous pressure monitoring, a catheter was inserted into the left atrium (LA). The LVAD was set to relativey high speed (3600 rpm) and the right ventricular assist device (RVAD) was started at a pump speed of 2000 rpm. TheECMOcouldbestoppedandremoved.Therewerestable circulatory conditions with a pump flow of 4.5 to 5.5 L/min on the LVAD and an LA pressure between 3 and 9 mm Hg. After the start of spontaneous breathing, the pump flow on the RVAD changed by the breathing pattern, with very high

New Issues and Controversies in the Prevention of Ventilator-associated Pneumonia

In the past 2 years, American, Canadian, and European scientific societies have published their new evidence-based guidelines for ventilator-associated pneumonia (VAP) prevention. However, these guidelines did not review some potentially useful strategies, such as the use of an endotracheal tube with an ultrathin cuff membrane, an endotracheal tube with a low-volume/low-pressure cuff, a device for continuous monitoring of the endotracheal tube cuff pressure, a device to remove biofilm from the inner site of the endotracheal tube, and saline instillation before tracheal suctioning. Only a few guidelines analyze the time of tracheostomy, and so no firm recommendations can be made regarding its importance. In addition, the guidelines diverge on the use of heat and moisture exchangers or heated humidifiers and on the use of an endotracheal tube coated with antimicrobial agents. The current review focuses on measures of VAP prevention for which there is no clear recommendation, or the use of which is controversial. A review of the literature suggests that the use of an endotracheal tube with an ultrathin and tapered-shape cuff membrane and coated in antimicrobial agents may reduce the risk of VAP. These features offer an attractive way to optimize the VAP prevention capacity of endotracheal tubes with a lumen for subglottic secretion drainage. We believe that early tracheostomy should be considered, based on the length reduction of mechanical ventilation and intensive care unit stay, reduction of mortality, and on patient comfort, although early tracheostomy has not yet been shown to favorably impact the incidence of VAP. We believed that heat and moisture exchangers should be considered based on the benefits in terms of cost savings. More research is necessary to clarify the role of continuous cuff pressure monitoring, removal of biofilm formation in the endotracheal tubes, and routine saline instillation before tracheal suctioning.

Perioperative Continuous Cerebrospinal Fluid Pressure Monitoring in Patients with Spontaneous Cerebrospinal Fluid Leaks: Presentation of a Novel Technique

A few studies have used direct measurements of cerebral spinal fluid pressure (CSFP) using either lumbar punctures or pressure transducers to evaluate CSFP elevations as a potential etiology in patients with spontaneous CSF leaks. Limitations of these techniques include positional variation, inadequate duration of measurement, and insufficient analysis of waveforms. We propose a novel technique for more accurate measurement of CSFP in patients with spontaneous CSF leaks. Patients with spontaneous CSF rhinorrhea had a lumbar catheter placed for 24-hour CSFP recording before and 72 hours after their endoscopic surgical repair. Heart rate, electrocardiogram, respirations, and oxygen saturation are recorded in addition to CSFP. Mean CSFP as well as the pulse waveform amplitude were calculated. Twelve patients with spontaneous CSF rhinorrhea underwent continuous CSFP monitoring. Seven patients had elevations in their CSFP of >25 cm H(2)O for at least 4% of their recording time during their continuous monitoring. Nine patients had significant oxygen desaturations associated with elevated CSFP. Pulse waveform amplitudes could average 20 cm H(2)O over several minutes in patients with mean CSFP of <10 cm H(2)O. Perioperative CSFP monitoring provides continuous data including mean and transient elevations in CSFP that can be correlated to other measurements such as oxygen saturation. This data may more accurately identify those CSF leak patients with elevated CSFP as well as correlate these elevations to prognostic clinical information that may improve treatment and outcome after their surgical repair.