Anesthesia and analgesia
-
Anesthesia and analgesia · May 2003
Clinical Trial Controlled Clinical TrialChanges in respiratory mechanics during cardiac surgery.
We investigated the role of cardiopulmonary bypass (CPB) in compromised lung function associated with cardiac surgery. Low-frequency respiratory impedance (Zrs) was measured in patients undergoing cardiac surgery with (n = 30; CPB group) or without (n = 29; off-pump coronary artery bypass [OPCAB] group) CPB. Another group of CPB patients received dopamine (DA) (n = 12; CPB-DA group). Extravascular lung water was determined in five CPB subjects. Zrs was measured before skin incision and after chest closure. Airway resistance and inertance and tissue damping and elastance were determined from Zrs data. Airway resistance increased in the CPB group (74.9% +/- 20.8%; P < 0.05), whereas it did not change in the OPCAB group (11.8% +/- 7.9%; not significant) and even decreased in the CPB-DA patients (-40.6% +/- 9.2%; P < 0.05). Tissue damping increased in the CPB and OPCAB groups, whereas it remained constant in the CPB-DA patients. Significant increases in elastance were observed in all groups. There was no difference in extravascular lung water before and after CPB, suggesting that edema did not develop. These results indicate a significant and heterogeneous airway narrowing during CPB, which was counteracted by the administration of DA. The mild deterioration in tissue mechanics, reflecting partial closure of the airways, may be a consequence of the anesthesia itself. ⋯ We observed that cardiopulmonary bypass deteriorates lung function by inducing a heterogeneous airway constriction, whereas no such effects were observed in patients undergoing cardiac surgery without bypass. The impairment in parenchymal mechanics, which was obtained in both groups, may result from peripheral airway closure and/or be a consequence of mediator release.
-
Anesthesia and analgesia · May 2003
Clinical TrialEvaluating surrogate measures of renal dysfunction after cardiac surgery.
Renal insufficiency after cardiac surgery is associated with increased mortality, morbidity, and length of intensive care unit stay. A convenient surrogate measure would facilitate the evaluation of renal-protective therapies. We evaluated two measures: the 72-h change in serum creatinine (Cr) (DeltaCr(72h)) and the percentage 72-h change in calculated (Cockcroft-Gault equation) Cr clearance (%DeltaCrCl(72h)). We randomly selected 2000 individuals who underwent aortocoronary bypass, valve surgery, or both at the Toronto General Hospital between May 1999 and August 2000. The variables were analyzed with frequency histograms and normal probability plots. Their association with dialysis, mortality, and prolonged intensive care unit stay was determined by using receiver operating characteristic (ROC) curves. DeltaCr(72h) was skewed to the right, whereas %DeltaCrCl(72h) was normally distributed. ROC curve areas showed DeltaCr(72h) to be a good predictor of dialysis (0.98), death (0.83), and prolonged hospitalization (0.74). %DeltaCrCl(72h) had similar ROC curve areas for predicting dialysis (0.97), death (0.82), and prolonged hospitalization (0.74). ROC curve areas did not differ significantly with respect to mortality (P = 0.89), dialysis (P = 0.49), or prolonged hospitalization (P = 0.85). Both variables were correlated with patient-relevant outcomes. Mathematical transformation of DeltaCr(72h) to %DeltaCrCl(72h) results in a normal distribution that is amenable to parametric statistical tests. DeltaCr(72h) and %DeltaCrCl(72h) may be used as surrogate outcomes in future trials. ⋯ A convenient surrogate measure of renal function is needed for evaluating renal-protective therapies in cardiac surgery. We evaluated the performance of serum creatinine concentration and calculated creatinine clearance for predicting dialysis, mortality, and prolonged hospitalization. Both measures were correlated with clinical outcomes. Creatinine clearance had the advantage of a distribution suitable for parametric statistical tests.
-
Anesthesia and analgesia · May 2003
Case ReportsGuiding surgical cannulation of the inferior vena cava with transesophageal echocardiography.
We studied 150 adult cardiac surgery patients to assess visualization of the venous cannula and the venous system by intraoperative transesophageal echocardiography and to register the incidence of cannulation of hepatic veins. The quality of images, the dimensions of the venous system, the position of the venous cannula, and the adequacy of venous return were registered. Acceptable image quality of the inferior vena cava and the right hepatic vein (RHV) was obtained in 95% and 87% of cases, respectively. Considerable individual variations were found in the dimensions of the venous system. The cannula position could be determined in 99% of the cases. Ten percent of venous cannulae were primarily placed in the RHV. A short distance between the eustachian valve and the RHV possibly predisposes to cannulation of the RHV. No other patient-related factors were associated with cannula position. Placement of the cannula deep in the inferior vena cava was associated with reduced venous return and may be a more important cause of reduced return than a cannula positioned in a hepatic vein. ⋯ Correct positioning of the venous cannula draining blood to the cardiopulmonary bypass circuit is important. Intraoperative transesophageal echocardiography allows satisfactory determination of the cannula position in nearly all patients. Ten percent of venous cannulae are primarily positioned in the right hepatic vein and not in the inferior vena cava as intended.