Partial Carbon Dioxide Rebreathing Research Articles

Correlations between Mean Arterial Blood Pressure, Cardiac Index, and Systemic Vascular Resistance Index in Laparoscopically-assisted Vaginal Hysterectomy (LAVH)

Background: The purpose of this study was to evaluate the correlations between mean blood pressure (MBP), cardiac index (CI), and systemic vascular resistance index (SVRI) in patients undergoing laparoscopically-assisted vaginal hysterectomy (LAVH). Methods: The authors enrolled 47-female patients prior to a LAVH. Hemodynamic parameters were measured before anesthetic induction, just after tracheal intubation, before skin incision, and 2, 5, 10, 20, and 30 min after pneumoperitoneum with by noninvasive cardiac output measurement using the partial carbon dioxide rebreathing method. Results: CI was significantly reduced 2 and 5 min after pneumoperitoneum (2.6 0.7 L/min/, and 2.5 0.7 L/min/, respectively), and then returned to the pre-skin incision level. SVRI increased significantly after pneumoperitoneum and was then restored to that measured pre-skin incision at 20 min after pneumoperitoneum. MBP before anesthetic induction was found to be correlated with CI at 20 and 30 min after pneumoperitoneum (R = 0.37, P = 0.022, R = 0.37, P = 0.036, respectively). A moderate correlation was observed between MBP before anesthetic induction and SVRI at 2, 5, 10, 20, and 30 min after pneumoperitoneum (R = 0.39 0.60, P

Comparison between cardiac output values measured by thermodilution and partial carbon dioxide rebreathing in patients with acute lung injury

Thermodilution, which is considered to be a standard technique for measuring the cardiac output in critically ill patients, is not free from relevant risks. There is a need to find alternative, noninvasive, automatic, simple and accurate methods for monitoring cardiac output at the bedside. To compare cardiac output measurements by thermodilution and partial carbon dioxide rebreathing in patients with acute lung injury at two levels of severity (lung injury score, LIS: below 2.5, group A; and above 2.5, group B). Comparative, prospective and controlled study. Intensive Care Units of two university hospitals. Cardiac output was measured by thermodilution and partial carbon dioxide rebreathing. Twenty patients with acute lung failure (PaO2/FiO2 < 300) who were under mechanical ventilation and from whom 294 measurements were taken: 164 measurements in group A (n = 11) and 130 in group B (n = 9), ranging from 14 to 15 determinations per patient. There was a poor positive correlation between the methods studied for the patients from groups A (r = 0.52, p < 0.001) and B (r = 0.47, p < 0.001). The application of the Bland-Altman test made it possible to expose the lack of agreement between the methods (group A: -0.9 +/- 2.71 l/min; 95% CI = -1.14 to -0.48; and group B: -1.75 +/- 2.05 l/min; 95% CI = -2.11 to -1.4). The comparison of the results (Student t and Mann-Whitney tests) within each group and between the groups showed significant difference (p = 0.000, p < 0.05). Errors in estimating CaCO2 (arterial CO2 content) from ETCO2 (end-tidal CO2) and situations of hyperdynamic circulation associated with dead space and/or increased shunt possibly explain our results. Under the conditions of this study, the results obtained allow us to conclude that, in patients with acute lung injury, the cardiac output determined by partial rebreathing of CO2 differs from the measurements obtained by thermodilution. This difference becomes greater, the more critical the lung injury is.

A noninvasive partial carbon dioxide rebreathing technique for measurement of pulmonary capillary blood flow is also a useful oxygenation monitor during one-lung ventilation

Study objectives To test the hypothesis that effective pulmonary capillary blood flow can be a useful indicator for estimating appropriate oxygenation and ventilation during one-lung ventilation in lung surgery. Design Prospective data analysis. Setting A 770-bed general teaching hospital. Patients 15 ASA physical status II and III patients undergoing elective lung surgery. Interventions Patients received general and thoracic epidural anesthesia and underwent lung operation with one-lung ventilation. Measurements We measured effective pulmonary capillary blood flow by a partial CO 2 rebreathing method and oxygenation parameters during two-lung ventilation before surgery, during one-lung ventilation, and during two-lung ventilation after lung surgery. Main results The effective pulmonary capillary blood flow index significantly decreased by 31.6%, which was associated with a significant decrease in arterial oxygen tension (PaO 2). The pulmonary shunt fraction increased to 46.3% during one-lung ventilation. During two-lung ventilation, after chest closure, effective pulmonary capillary blood flow index divided by heart rate (i.e., effective pulmonary blood stroke flow index) was still significantly lower than that seen during two-lung ventilation before thoracotomy. There were significant correlations between effective pulmonary capillary blood flow, pulmonary blood stroke flow index, and PaO 2. Conclusions Effective pulmonary capillary blood flow index and effective pulmonary blood stroke flow index are useful indicators for determining appropriate oxygenation therapy during one-lung ventilation.

THIS MONTH IN ANESTHESIOLOGY

THIS MONTH IN ANESTHESIOLOGY

Noninvasive cardiac output assessment during heart surgery.

To evaluate the reliability of a new noninvasive method for the assessment of cardiac output with the partial carbon dioxide rebreathing technique. This technique was applied to patients undergoing heart surgery. Values of cardiac index obtained with this equipment were compared with the artero-venous CO2 gradient, a reliable index of cardiovascular status. Positive and negative predictive values of the test were assessed. A total of 21 simultaneous measurement of the cardiac index and of the artero-venous CO2 gradient were obtained. The positive predictive value of the test was 67% while the negative predictive value was 100%, indicating that a normal value of cardiac index recorded with the rebreathing technique predicts with a good reliability a normal cardiovascular state. Working through a series of mathematical algorithms, accuracy in the computation of cardiac output can be decreased with this equipment; however, this limitation seems to be outweighed by the simplicity and noninvasive nature of the methods.

Measurement of cardiac output by thermal dilution in man.

Measurement of cardiac output by thermal dilution in man.