Position of the catheter tip to the left of the zero point was defined as positive and to the right as negative. Distances were recorded in centimeters. After proper location of the catheter was confirmed, the SAT-2 oximetry system was calibrated to CO-oximetry (in vitro SvO,) and the current hematocrit (Hct) and hemoglobin (Hgb) values were entered into the saturation computer. The HEMOPRO, system also had the current Hct and Hgb values entered into its saturation computer as recommended by the manufacturer. The Oximetrix 3 system does not require entry of Hgb or Hct values into the saturation computer.
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A Comparison of Three Pulmonary Artery Oximetry Catheters in Intensive Care Unit Patients (6)
A Comparison of Three Pulmonary Artery Oximetry Catheters in Intensive Care Unit Patients (5)
Procedure
All of the study catheters were inserted percutaneously by one of the investigators (P.E.S.) using a modified Seldinger technique to place an 8.5-Fr introducer sheath. The catheters were calibrated according to manufacturers’ instructions. The Oximetrix 3 was calibrated in vitro as was the HEMOPRO*. The SAT-2 system was calibrated in vivo, as this was the method recommended by the manufacturer for assuring best agreement with CO-oximetry. Under continuous electrocardiographic and pressure waveform monitoring, the catheters were passed through the introducer sheath until intrathoracic location was confirmed by venous waveforms and respiratory fluctuation.
A Comparison of Three Pulmonary Artery Oximetry Catheters in Intensive Care Unit Patients (4)
Patients
A total of 30 patients were enrolled in the study, which was approved by die Clinical Research Practices Committee of the Bowman Gray School of Medicine/North Carolina Baptist Hospital. Informed consent was obtained from patients’ next of kin before study initiation. All patients enrolled in the study were admitted to the Multidisciplinary Intensive Care Unit of North Carolina Baptist Hospital. The primary admitting service of each potential study patient had previously determined that the patient would benefit from hemodynamic monitoring. Patients were divided equally into three groups corresponding to the three PA oximetry systems being evaluated. The three PA oximetry systems were evaluated sequentially based on availability of equipment from the manufacturers. The order of testing was Oximetrix 3, SAT-2, and HEMOPRO,. In addition to PA catheters, all patients had arterial lines placed for continuous blood pressure monitoring. All patients had PA occlusion pressures (PAOP) and thermodilution cardiac outputs measured.
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A Comparison of Three Pulmonary Artery Oximetry Catheters in Intensive Care Unit Patients (3)
Each manufacturer supplied the saturation computer, optical module, and oximetry PA catheters that were used in the study. Representatives from each company instructed two of the authors (P.E.S. and L.C.H.) in the proper use of the instruments. Several catheters from each manufacturer were placed in patients before initiation of the comparative study. Proper insertion technique and use of the equipment were confirmed by the company representatives during these prestudy trials.
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A Comparison of Three Pulmonary Artery Oximetry Catheters in Intensive Care Unit Patients (2)
Methods and Materials
Equipment
The most recent versions of the three commercially available, FDA-approved in vivo oximetry systems (catheter, optical module, and computer) were obtained from their respective manufacturers. Three oximetry PA catheters were studied: (1) Oximetrix 3 P7110-EP-H 7.5 Fr; (2) Edwards Critical Care SAT-2 93-A-770H 7.5 Fr; and (3) Viggo-Spectramed HEMOPRO 7.5 Fr. The Oximetrix 3 system (Abbott Critical Care Systems, Hospital Products Division, Abbott Laboratories, North Chicago, 111) uses a dual fiberoptic bundle in the PA catheter. Three reference wavelengths are produced by the optical module and transmitted down one fiberoptic bundle.
A Comparison of Three Pulmonary Artery Oximetry Catheters in Intensive Care Unit Patients (1)
Considerable controversy exists as to the clinical utility of pulmonary artery (PA) mixed venous oxygen saturation (SvOJ catheters as a continuous monitor for patient treatment. Significant impediments to the clinical use of Sv02 oximetry systems include both the reported inaccuracy of some systems and the absence of clinical data defining acceptable levels of agreement when compared with a criterion standard.
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Glucose Homeostasis (15)
The study by Kuntschen et al also compared two groups of patients undergoing either hypothermic or normothermic CPB with bubble oxygenators. The patients undergoing hypothermic CPB had slightly greater body dimensions and probably a different diet (Switzerland vs south of France). At induction of anesthesia, they were administered fentanyl, 12.5 \l%/ kg (vs 2.5 fig/kg), and then nitrous oxide and enflurane. Cardiac arrest was obtained without cardioplegia (vs cold cardioplegic solution). By contrast, the present study used membrane oxygenators and a different anesthesia with higher doses of fentanyl but no anesthetic gases.
Glucose Homeostasis (14)
Similar results were found by Sebel et al with hypothermic CPB. Yokota et al observed decreased plasma GH levels during hypothermic CPB but GH peaks preceded and followed CPB. Differences in anesthetic and perfusion techniques may account for these differences.
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Glucose Homeostasis (13)
After hypothermic CPB, glucagon levels were lower than in the normothermic group. Similar findings were observed by Kuntschen et al. Lower central temperature or a higher blood glucose level after hypothermic CPB may explain this difference. Moreover, it appears that glucagon is not responsible for the greater hyperglycemia observed after hypothermic CPB.
As reported previously, plasma cortisol concentrations were lower during hypothermic CPB than during normothermic CPB. This result was similar to that of other studies using different anesthetic agents in that plasma cortisol decreased 15 min after starting hypothermic CPB which was most likely because of hemodilution in the face of unchanged secretion. By contrast, cortisol secretion increased during normothermic CPB. After rewarming, cortisol was higher than in the normothermic group in the study of Kuntschen et al but the difference was not significant in the present study.
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Glucose Homeostasis (12)
During rewarming, plasma insulin increased twofold over preoperative values. Similar findings were reported by Baum et al. This rebound could be due to a hypersecretion of insulin after a reduced release during hypothermia. The concomitant increase in glycemia is explained by the action of hyperglycemic hormones, particularly glucagon which increased simultaneously and has a rapid effect.
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