CDU Contributing Writer

SAN DIEGO, California – The 31st annual congress of the Society of Critical Care Medicine (SCCM; Des Plaines, Illinois), held here in late January, provided a forum for the introduction of a number of new products for use in the critical care setting, as well as a window on the future of patient management in intensive care.

One area of continuing development in critical care medicine is patient monitoring technologies, including technology for cardiac and hemodynamic monitoring. Edwards Lifesciences (Irvine, California) has developed volumetric technology for continuous cardiac output monitoring that allows direct measurement of the right ventricular end diastolic volume index (RVEDVI). As discussed by R.P. Dellinger, MD, of Rush Presbyterian-St. Luke's Medical Center (Chicago, Illinois) at the SCCM meeting, the index in conjunction with right ventricular ejection fraction is proving superior to traditional parameters such as pulmonary artery wedge pressure and central venous pressure in predicting a patient's response to resuscitation therapy in the ICU. Such monitoring is proving useful in the management of patients with sepsis and acute respiratory distress syndrome (ARDS). Studies using the index also have elucidated some of the issues surrounding use of PAW and CVP in the ICU, including concerns raised in prior studies about excess mortality in patients receiving pulmonary artery catheters. Michael Cheatham, MD, of Orlando, Florida, said the problems encountered in the past with pulmonary artery catheter use probably were the result of relying only on pressure measurements to interpret hemodynamic function, rather than including volume information as well. The consensus is that using only PAW or CVP is no longer the standard of care in the ICU and that inclusion of a volume index is essential in order to properly evaluate hemodynamics.

Cardiodynamics International (San Diego, California) continues to increase its penetration in the hemodynamic monitoring segment with its BioZ noninvasive cardiac output system. The BioZ system uses impedance cardiography technology to measure cardiac output, systemic vascular resistance, contractility and fluid level. Reimbursement for Medicare patients is now offered for a number of indications, including monitoring of suspected cardiovascular disease, fluid management in cardiac patients, determination of the need for IV inotropic therapy and monitoring of heart-transplant patients after myocardial biopsy. The system is marketed through a partnership with GE Medical Systems (Waukesha, Wisconsin), and modules also have been developed for the GE Solar series monitors that connect to the BioZ leads. For 2001, Cardiodynamics reported sales of $19.6 million, an increase of 50% vs. 2000. The BioZ installed base exceeds 1,650 worldwide, up 50% from a year ago. The company reported a profit in each of the past two quarters.

A new cardiac output monitor was introduced by LidCO Ltd. (Cambridge, UK) at the SCCM meeting. LidCO's PulseCO System uses arterial pressure wave analysis to derive a beat-to-beat cardiac output reading, which is calibrated using a unique new lithium dilution technique. The PulseCO analyzes the signal from a radial artery pressure sensor to derive cardiac output. At the start of monitoring, a subtherapeutic dose of lithium chloride is injected in the venous circulation, and an ion-selective electrode sensor in the arterial line is used to measure the dilution curve and calibrate the system. The lithium dose is 240-fold lower than the standard dose given for manic depression. According to LidCO, the lithium dilution method is three times more accurate than thermodilution, providing a highly precise calibration that is maintained for eight to 12 hours. The system has been on the market for less than one year, and 128 have been placed worldwide, including 65 in the U.S. Sales have reached about $1.6 million. The PulseCO is priced at $12,000, with a disposable price of $109.

Additional systems for monitoring cardiac output were exhibited at SCCM by Pulsion AG (Munich, Germany) and Deltex Medical (Branford, Connecticut). The Pulsion PiCCO system incorporates a less-invasive monitoring technique using a femoral artery catheter and performs pulse contour analysis on thermodilution waveforms to generate a beat-to-beat cardiac output. Cost is about $150 per application. The Deltex CardioQ uses esophageal Doppler ultrasound measurements to derive a less-invasive cardiac output reading. The CardioQ monitor is priced at $8,000, and the probes are priced at $99 if the monitor is purchased, or $119 if the monitor is placed at no charge. The U.S. market for cardiac output monitoring products (Table 1) is substantial, with most of the growth in the noninvasive segment at present. The noninvasive segment is expected to continue to exhibit rapid growth for the next few years as additional new market segments develop. Cardiodynamics estimates that the total market opportunity, which includes applications in a variety of alternate-site settings such as physician offices, clinics and, ultimately, home monitoring, represents an annual procedure volume of almost 30 times the existing market, indicating a large potential for market expansion.

Interest also is growing in monitoring of metabolic parameters in critical care. Lactate is being used by an increasing number of critical care physicians to monitor metabolism and as an early indicator of conditions such acidosis or bacterial meningitis. Nova Biomedical (Waltham, Massachusetts) now offers a lactate assay on its compact pHOx analyzer for use in point-of-care testing. The pHOx is the company's best-selling product. Datex-Ohmeda (Madison, Wisconsin) has introduced a new multi-disciplinary monitor, the S15 Critical Care Monitor, that provides pulmonary, cardiovascular, electroencephalography, gastric perfusion and nutrition monitoring in a single integrated system. New technologies to monitor tissue metabolism and microvascular blood flow, including measurement of tissue pH and pO₂ as well as oxygen saturation patterns, are being evaluated by researchers for use in assessing patients in surgery as well as in patients in the ICU with sepsis, ARDS and other critical conditions. As described by D. DeBacker of Erasme University Hospital (Brussels, Belgium) at the SCCM conference, measurements of microvascular flow patterns have shown that changes are correlated with outcome in sepsis. Cytometrics (Philadelphia, Pennsylvania) has developed the Hemoscan system for noninvasive measurement of tissue perfusion patterns, with applications in monitoring of shock in intensive care. The Cytometrics system uses a technique called orthogonal polarization spectral imaging, or microvideoscopy, to measurement heterogeneity of tissue oxygenation. Measurements in patients with cardiogenic and septic shock demonstrate considerable heterogeneity in tissue flow, with some vessels having high flow while others have almost none.

Another new development in monitoring was unveiled by Metracor Technologies (San Diego, California). The company has developed the RODA Monitor, which combines the blood gas/electrolyte monitoring technology developed by the former VIA Medical with hemodynamic monitoring technology developed by TNO Biomedical (Amsterdam, the Netherlands), with additional involvement and funding from Alliance Pharmaceutical (San Diego, California). TNO Biomedical's continuous cardiac output (CCO) measurement technology employs arterial pressure pulse wave analysis, a technique that can be used in place of thermodilution after a calibration has been performed. The RODA adds ionized calcium to the VIA sensor cartridge in addition to the integration of CCO capability and other derived hemodynamic parameters. New hardware/software allows the sensor cartridge and arterial line to travel with the patient and plug into monitors at multiple locations, along with a sophisticated graphical user interface that allows the clinician or nurse to rapidly interpret patient status.

The system recently received FDA 510(k) approval, and availability is projected for this summer. The added features of the RODA system should help Metracor expand beyond the 60 institutions now using the monitor developed by VIA Medical. The existing sensor for measurement of blood gases and chemistry parameters is priced at $200 ($300 for the neonatal version) and can be used for three days. The new RODA sensor will be priced at $250. In order to calibrate the RODA hemodynamic monitor, the user inputs patient height, weight and age, and parameters are computed that relate the arterial pressure wave measurements to thermodilution cardiac output. For blood gas and chemistry measurements, including measurement of pO₂ , pCO₂ , pH, sodium, potassium and hematocrit, the system intermittently pulls between 1.5 ml and 2.5 ml of blood from the radial artery into its sensor compartment, performs a measurement and then returns the blood to the patient, along with an additional one cc of fluid. About one minute is required to perform the analysis, and a measurement can be performed every 10 minutes. Monitors typically are placed free of charge in return for use of a certain minimum number of sensors.