Journal of clinical monitoring
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We continuously monitored spontaneous respiration after extubation by end-tidal CO2 tension (PETCO2) in 19 patients aged 20 to 72 years who had undergone major operations. The respiratory gas was sampled from the nasopharynx via a special nasal catheter and analyzed by a side-stream analyzer. In each case, optimal placement of the nasal catheter was determined by CO2 waveform and the capnograms were recorded for waveform analysis and trend monitoring. ⋯ While the mean values for PETCO2 and PaCO2 were similar, several patients had large differences for PaCO2 to PETCO2. The differences of the individual patients did not differ significantly between the various times of measurement. We conclude that this form of capnometry is well suited for continuous, noninvasive monitoring of respiration in nonintubated, spontaneously breathing patients.
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We describe and evaluate a new apparatus that monitors end-tidal carbon dioxide (PETCO2) and augments the inspired oxygen concentration in awake, sedated patients. The unit was evaluated for its effectiveness as an oxygenation device and its accuracy as a predictor of PaCO2 through the correlation of PaCO2 with PETCO2. Twenty cardiac surgical patients, physical status ASA 2-4, participated in this study. ⋯ The ratios of PETCO2 compared with PaCO2 were 0.98, 0.94, and 0.85, with correlation coefficients of r = 0.81, 0.85, and 0.63, respectively. The PaO2 values were 114, 154, and 183 mm Hg for the corresponding nasal oxygen flow rates of 2, 4, and 6 L/min, respectively. This study indicates that this modified nasal cannula provides supplemental oxygen adequately and yields a satisfactory reflection of the PaCO2 depending on the oxygen flow rate delivered.
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Comparative Study
Comparative accuracies of a finger blood pressure monitor and an oscillometric blood pressure monitor.
A noninvasive blood pressure monitor (Finapres) that uses the methodology of Penaz to continuously display the arterial waveform from the finger has been introduced recently. The Finapres monitor overestimated systolic pressure by 5.8 +/- 11.9 mm Hg, while the Dinamap monitor underestimated systolic pressure by -6.9 +/- 9.2 mm Hg (P = 0.003). Dinamap mean and diastolic pressure biases were less than 2 mm Hg, while the Finapres biases for these variables were significantly greater (7.7 +/- 10.0 and 8.2 +/- 9.8 mm Hg, respectively). ⋯ Despite this bias, blood pressure changes were tracked closely in these 2 patients. We conclude that, in its current form, the Finapres monitor cannot be relied upon independently to accurately measure blood pressure in patients undergoing general anesthesia. Since the Dinamap monitor measures mean pressure reliably and accurately, we suggest that mean blood pressure values between the Finapres and Dinamap monitors be compared to guide one in interpreting Finapres data.
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This study was undertaken to determine whether the use of automated noninvasive blood pressure monitoring altered the frequency of detection of intraoperative hypotension. We retrospectively reviewed 1,861 anesthetic records from a period in 1987, when blood pressure was obtained manually by auscultation. ⋯ The data revealed that the incidence of detected hypotension increased from 2.4 to 5.2% with the use of automated blood pressure monitors (P less than 0.00002). We conclude that at our hospital the use of automated noninvasive blood pressure monitors increases the incidence of detection of intraoperative hypotension as compared with the use of manual blood pressure measurement.
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With the advent of automated anesthesia record keeping devices, concern has arisen that "abnormal" values will appear in the record and possibly lead to medicolegal compromise. A retrospective review of automated records from a series of anesthesia cases was undertaken to determine if abnormal values do occur, how frequent they are, and whether they cause problems. A total of 14,826 (4,942 each) noninvasive heart rate, systolic, and diastolic blood pressure readings from 118 case printouts generated by a Diatek Arkive Patient Information Management System (63 cases) or a Datascope Datatrac record keeper (55 cases) were recorded. ⋯ During the anesthetics, 3.6% of the systolic pressure readings, 13.25% of the diastolic readings, and 4.25% of the heart rate readings were recorded outside these ranges. No serious intraoperative or postoperative anesthesia complications were associated with these out-of-range readings, nor would they be expected in a sample of this size, since serious anesthetic complications are rare. This preliminary observation of one person's experience may help address the concern associated with allowing high and low blood pressure and heart rate readings to be automatically recorded "unsmoothed." In medicolegal situations, it should also begin to demonstrate that such fluctuations are neither uncommon nor abnormal, and that a true record of these readings should be neither a cause for concern nor an opportunity for medicolegal exploitation.