Peter Lamm

Continuous cardiac output by femoral arterial thermodilution calibrated pulse contour analysis: comparison with pulmonary arterial thermodilution.

OBJECTIVE To compare two thermodilution methods for the determination of cardiac output (CO)-thermodilution in the pulmonary artery (COpa) and thermodilution in the femoral artery (COa)-with each other and with CO determined by continuous pulse contour analysis (COpc) in terms of reproducibility, bias, and correlation among the different methods. Good agreement between the methods would indicate the potential of pulse contour analysis to monitor CO continuously and at reduced invasiveness. DESIGN Prospective criterion standard study. SETTING Cardiac surgical intensive care unit in a university hospital. PATIENTS Twenty-four postoperative cardiac surgery patients. INTERVENTIONS Without interfering with standard hospital cardiac recovery procedures, changes in CO as a result of the postsurgical course, administration of vasoactive substances, and/or fluid administration were recorded. CO was first recorded after a 1-hr stabilization period in the intensive care unit and hourly thereafter for 6 hrs, and by subsequent determinations at 9, 12, and 24 hrs. MEASUREMENTS AND MAIN RESULTS There were 216 simultaneous determinations of COpa, COa, and COpc. COpc was initially calibrated using COa, and no further recalibration of COpc was performed. COpa ranged from 3.0 to 11.8 L/min, and systemic vascular resistance ranged from 252 to 2434 dyne x sec/cm5. The mean difference (bias) +/-2 SD of differences (limits of agreement) was -0.29+/-1.31 L/min for COpa vs. COa, 0.07+/-1.4 L/min for COpc vs. COpa, and -0.22+/-1.58 L/min for COpc vs. COa. In all but four patients COpc correlated with COa after the initial calibration. Correlation and precision of COpc vs. COa was stable for 24 hrs. CONCLUSIONS Femoral artery pulse contour CO correlates well with both COpa and COa even during substantial variations in vascular tone and hemodynamics. Additionally, CO determined by arterial thermodilution correlates well with COpa. Thus, COa can be used to calibrate COpc.

Usefulness of left ventricular stroke volume variation to assess fluid responsiveness in patients with reduced cardiac function.

ObjectiveStroke volume variation as measured by the analysis of the arterial pressure waveform enables prediction of volume responsiveness in ventilated patients with normal cardiac function. The aim of this study was to investigate the ability of monitoring stroke volume variation to predict volume responsiveness and to assess changes in preload in patients with reduced left ventricular function after cardiac surgery. DesignProspective study. SettingUniversity hospital. PatientsFifteen mechanically ventilated patients with a left ventricular ejection fraction <0.35 (study group) and 15 patients with an ejection fraction >0.50 (control group) after coronary artery bypass grafting following admission to the intensive care unit. InterventionsVolume loading with 10 mL of hetastarch 6% times body mass index. If stroke volume index increased >5%, successive volume loading was performed until no further increase in stroke volume index was reached. Measurements and Main ResultsStroke volume variation, central venous pressure, pulmonary artery occlusion pressure (PAOP), and left ventricular end-diastolic area index (LVEDAI) were measured at baseline and immediately after each volume loading step. In both groups, stroke volume variation at baseline correlated significantly with changes in stroke volume index caused by volume loading (p < .01). Further, changes in stroke volume variation as a result of volume loading correlated significantly with the concomitant changes in stroke volume index in both groups (p < .01). Using receiver operating characteristic analysis, in the study group areas under the curve for stroke volume variation, PAOP, central venous pressure, and LVEDAI did not differ significantly. In the control group, the area under the curve for stroke volume variation was statistically larger than for PAOP, central venous pressure, and LVEDAI. ConclusionsContinuous and real-time monitoring of stroke volume variation by pulse contour analysis can predict volume responsiveness and allows real-time assessment of the hemodynamic effect of volume expansion in patients with reduced left ventricular function after cardiac surgery.

Central venous pressure, pulmonary capillary wedge pressure and intrathoracic blood volumes as preload indicators in cardiac surgery patients

OBJECTIVE Monitoring of cardiac preload is mainly performed by measurement of central venous and pulmonary capillary wedge pressure in combination with assessment of cardiac output, applying the pulmonary arterial thermal dilution technique. However, the filling pressures are negatively influenced by mechanical ventilation and the pulmonary artery catheter is criticized because of its inherent risks. Measurement of right atria, right ventricular, global end diastolic and intrathoracic blood volume index by arterial thermal dye dilution utilizing the COLD-system may represent an alternative. METHODS In 30 CABG patients with an uncomplicated postoperative course the mentioned parameters were measured 1, 3, 6, 12 and 24 h postoperatively to prove their qualification as preload indicators: As patients received no inotropic support, changes of cardiac index and stroke volume index must correlate to changes of presumably preload indicating parameters. RESULTS When arterial and pulmonary arterial thermal dilution were compared, no differences were found; the correlation coefficient being 0.96, the bias 0.16 l/min per m2 (2.4%) and coefficients of variation did not exceed 7%. Changes of central venous pressure, capillary wedge pressure, right atrial end diastolic volume index and right ventricular end diastolic volume index did not correlate at all to changes of cardiac and stroke volume index (coefficients ranged from -0.01 to 0.28). In contrast, intrathoracic and global end diastolic blood volume indices with coefficients from 0.76 to 0.87, did show a good correlation to cardiac and stroke volume index. CONCLUSION Central venous pressure, capillary wedge pressure, right atrial and right ventricular end diastolic volumes are no suitable preload parameters in cardiac surgery intensive care, compared to intrathoracic and global end diastolic blood volumes. The latter show a higher clinical value and can be obtained by less invasive methods, as no pulmonary artery catheter is required.

Stress doses of hydrocortisone reduce severe systemic inflammatory response syndrome and improve early outcome in a risk group of patients after cardiac surgery.

ObjectiveSevere systemic inflammation with a vasodilatory syndrome occurs in about one third of all patients after cardiac surgery with cardiopulmonary bypass. Hydrocortisone has been used successfully to reverse vasodilation in septic patients. We evaluated if stress doses of hydrocortisone attenuate severe systemic inflammatory response syndrome in a predefined risk group of patients after cardiac surgery with cardiopulmonary bypass. DesignRandomized, nonblinded, controlled trial. SettingAnesthesiologic intensive care unit for cardiac surgical patients of an university hospital. PatientsAfter a risk analysis, we enrolled 91 patients into a prospective randomized trial. Patients were included according to the evaluated criteria (preoperative ejection fraction, duration of cardiopulmonary bypass, type of surgery). InterventionsThe treatment group received stress doses of hydrocortisone perioperatively: 100 mg before induction of anesthesia, then 10 mg/hr for 24 hrs, 5 mg/hr for 24 hrs, 3 × 20 mg/day, and 3 × 10 mg/day. Measurements and Main ResultsWe measured various laboratory (e.g., lactate) and clinical variables (e.g., duration of ventilation and length of stay in the intensive care unit), characterizing the patients’ outcome. The two study groups did not differ regarding age, preoperative medication, duration of the cardiopulmonary bypass, and type of surgery. The patients in the treatment group had significantly lower concentrations of IL-6 and lactate, higher antithrombin III concentration, lower need for circulatory and ventilatory support and for transfusions, lower Therapeutic Intervention Scoring System values, and shorter length of stay in the intensive care unit and in the hospital. The mortality rate did not differ significantly between the groups. ConclusionsAlthough we acknowledge the limitations of a nonblinded interventional trial, stress doses of hydrocortisone seem to attenuate systemic inflammation in a predefined risk group of patients after cardiac surgery with cardiopulmonary bypass and improve early outcome.

Beat-to-beat measurement of cardiac output by intravascular pulse contour analysis: A prospective criterion standard study in patients after cardiac surgery

OBJECTIVE To evaluate the accuracy of a new pulse contour method of measuring cardiac output in critically ill patients. DESIGN A prospective criterion standard study. SETTING Cardiac surgery intensive care unit in a university hospital. PARTICIPANTS Nineteen cardiac surgery patients requiring intensive care treatment with pulmonary artery catheters after surgery. INTERVENTIONS None. MEASUREMENTS AND MAIN RESULTS The pulse contour cardiac output monitor uses transpulmonary bolus thermodilution measurements to calibrate the system. In each patient, the pulse contour cardiac output values were compared with conventional thermodilution. The method described by Bland and Altman and linear regression analysis were used for comparison. The mean difference (bias) +/- standard deviation of differences (precision) was 0.31 +/- 1.25 L/min for pulmonary bolus thermodilution cardiac output versus pulse contour cardiac output and 0.21 +/- 0.73 L/min for pulmonary bolus thermodilution cardiac output versus transpulmonary bolus thermodilution cardiac output. Linear regression (correlation) analyses were pulse contour cardiac output = 0.97 thermodilution + 0.53 (r = 0.88), and transpulmonary cardiac output = 0.87 thermodilution + 1.09 (r = 0.96). There was a small increase 60 minutes after recalibration but not a statistically significant difference between pulse contour cardiac output and pulmonary bolus thermodilution cardiac output (p = 0.52). CONCLUSIONS Bias and precision are acceptable, and the system provides results that agree with conventional thermodilution. This study demonstrates the clinical applicability of the pulse contour cardiac output monitoring system.

Less invasive, continuous hemodynamic monitoring during minimally invasive coronary surgery

BACKGROUND Minimally invasive coronary surgery has gained more and more clinical acceptance. A clear contrast to the minimally invasive idea is the highly invasive pulmonary artery catheter used for hemodynamic monitoring during the operation. We evaluated a less invasive device which calculates cardiac output (CO) and hemodynamics based on arterial pulse-contour analysis. METHODS In 20 patients revascularized by the off-pump technique with the octopus system, agreement of CO by pulse-contour was compared to pulmonary arterial and femoral arterial thermodilution and hemodynamic alterations during the operation were recorded. Pulse-contour CO is computed by measuring the area under the arterial pressure waveform and dividing it by aortic impedance. Aortic impedance is determined by an arterial thermodilution at the onset of the system. RESULTS Correlation of pulmonary arterial and arterial thermodilution CO to pulse-contour CO was 0.91 and 0.90 respectively (both p<0.01). Coefficients of variations were 6.2% and 6.7%. The bias was 0.1 L per minute and standard deviations were 0.42 L per minute and 0.55 L per minute. Hemodynamic changes during the operations were seen mainly during the distal anastomosis of the first diagonal branch; only slight changes occurred during the anastomosis of the left anterior descending coronary artery. CONCLUSIONS Arterial pulse-contour analysis is easy to use and minimally invasive, thus qualifies as a reliable routine monitoring tool during minimally invasive coronary surgery with tissue stabilizers.

Stress doses of hydrocortisone in high-risk patients undergoing cardiac surgery: effects on interleukin-6 to interleukin-10 ratio and early outcome.

Background:Severe systemic inflammation (systemic inflammatory response syndrome) associated with cardiac surgery often leads to a worse short-term and long-term outcome. Stress doses of hydrocortisone have been successfully used to improve outcome of CS. The interleukin (IL)-6 to IL-10 ratio is associated with outcome after trauma and major surgery. Objective:To evaluate immunologic effects (especially IL-6 to IL-10 ratio) of stress doses of hydrocortisone in a high-risk group of patients after cardiac surgery with cardiopulmonary bypass. Design:Prospective, randomized, double-blinded, placebo-controlled trial. Setting:Cardiovascular intensive care unit of a university hospital. Patients:High-risk patients (n = 36) undergoing CS. Intervention:Stress doses of hydrocortisone or placebo. Main Outcome Measures:IL-6 to IL-10 ratio and other markers of systemic inflammation at predefined time points; short-term clinical outcome. Results:The two study groups did not differ with regard to demographic data. The patients from the hydrocortisone group (n = 19) had significantly lower levels of IL-6 and higher levels of IL-10, resulting in an attenuated change in IL-6/IL-10 ratio (28.7 [6.4/128.7] vs. 292.8 [6.5/534.6] 4 hours after cardiopulmonary bypass; p < 0.001). Patients in the hydrocortisone group had a shorter duration of catecholamine support (1 [1/2] vs. 4 [2/4.5] days; p = 0.02), a shorter length of stay in the intensive care unit (2 [2/3] vs. 6 [4/8] days; p = 0.001), and a lower incidence of postoperative atrial fibrillation (26% vs. 59%; p = 0.04). Conclusions:Stress doses of hydrocortisone attenuate the evolution of IL-6/IL-10 ratio in patients with systemic inflammatory response syndrome after CS, which seems to be associated with an improved outcome. The immunologic effects of hydrocortisone may thus be both, inhibitory (IL-6) and permissive (IL-10), regarding the immune response.

Markers of myocardial ischemia after minimally invasive and conventional coronary operation

BACKGROUND The purpose of this study was to evaluate the course of serum markers of myocardial tissue damage after two different types of minimally invasive coronary surgical procedures (MICS) as compared with conventional coronary artery bypass grafting (CABG). METHODS We enrolled 87 patients with one- or two-vessel disease scheduled for one of the three procedures: minimally invasive direct coronary artery bypass grafting (MIDCABG) by lateral thoracotomy (n = 29), the OCTOPUS method by median sternotomy (n = 27), and CABG (n = 31). Creatine kinase activity (CK), creatine kinase MB activity (CK-MB act), creatine kinase MB mass concentration (CK-MB mass), myoglobin concentration (MG), and cardiac troponin I concentration (cTnI) were measured perioperatively until the second postoperative day. RESULTS Creatine kinase-MB, CK-MB mass, and cTnI were significantly higher after CABG and were nearly maintained within the normal range in MICS. Creatine kinase and MG were significantly lower in the OCTOPUS group than in the MIDCABG or CABG groups. CONCLUSIONS Minimally invasive coronary surgical procedures cause less myocardial injury than CABG as indicated by specific serum markers. However, higher CK and MG reflect more substantial skeletal muscle trauma during MIDCABG operation compared with OCTOPUS procedures.

Continuous cardiac output measurements do not agree with conventional bolus thermodilution cardiac output determination

PurposeTo evaluate the performance of two different continuous cardiac output monitoring systems based on the thermodilution principle in critically ill patients.MethodsNineteen cardiac surgical patients were randomly assigned to continuous cardiac output monitoring using one of the two systems under study (group I, IntelliCath™ catheter, n=9; group II, Opti-Q™ catheter,n = 10). Each patient was studied over a period of three hours. Conventional bolus thermodilution cardiac output measurements were carried out every 15 min leading to 13 measurements in each patient. The continuous cardiac output values were compared with the bolus thermodilution measurements. Bias (mean difference between continuous and bolus thermodilution) and precision (SD of differences) were calculated as a measure of agreement between the respective continuous method and conventional bolus thermodilution.ResultsThe range of measured cardiac outputs was 3.8–15.4 L·min−1 (IntelliCath™) and 3.5–8.3 L·min−1 (OptiQ™). Bias and precision was 0.06 ± 0.76 L·min−1 (IntelliCath™) and −0.04 ± 0.74 L·min−1 (OptiQ™), respectively. There was no difference in bias between the two systems (P=0.38). ± 2 SD of the differences (i.e., 95% of the differences) did not fall within the predetermined limits of agreement of ± 0.5 L·min−1.ConclusionsThere was no difference between the two systems regarding the agreement with conventional bolus thermodilution as the standard. A discrepancy between bolus and continuous thermodilution cardiac output measurement techniques above the clinically acceptable limits suggest that they are not interchangeable.RésuméObjectifÉvaluer, chez des patients gravement malades, la performance de deux systèmes de monitorage continu du débit cardiaque fondés sur le principe de la thermodilution.MéthodeDixneuf patients de cardiochirurgie ont été répartis de façon aléatoire en deux groupes de monltorage continu du débit cardiaque: le groupe I, avec une sonde IntelliCath™, n = 9; le groupe II, avec une sonde Opti- Q™, n = 10). Chaque patient a été observé pendant trois heures. Les mesures traditionnelles du débit cardiaque par thermodilution d’un bolus ont été faites toutes les 15 min, pour un total de 13 mesures par patient. Les valeurs continues du débit cardiaque ont été comparées aux mesures par thermodilution d’un bolus. Le biais (différence moyenne entre la thermodilution continue et celle d’un bolus) et la précision (écart type des différences) ont été calculés comme mesure de concordance entre la méthode continue et la thermodilution traditionnelle d’un bolus.RésultatsLes limites des débits cardiaques mesurés ont été de 3,8 – 15,4 L·min− 1 (IntelliCath™ et de 3,5 – 8,3 L·min− 1 (OptiQ™). Le biais et la précision ont été de 0,06 ± 0,76 L·min− 1 (IntelliCath™) et de − 0,04 ± 0,74 L·min− 1 (OptiQ™), respectivement. Le biais a été comparable entre les deux sondes (P = 0,38); et ± 2 écarts types des différences (95 % des différences) n’étaient pas compris dans les limites de concordance prédéterminées de ± 0,5 L·min− 1.ConclusionLes deux systèmes n’ont pas présenté de différence entre eux quant à la concordance avec la norme traditionnelle de la thermodilution d’un bolus. Une divergence entre les mesures du débit cardiaque par themodilution d’un bolus et thermodilution continue au delà des limites acceptables en pratique permet d’affirmer que ces deux techniques ne sont pas interchangeables.

The harmonic scalpel: optimizing the quality of mammary artery bypass grafts.

BACKGROUND The damage done to the endothelium during the preparation of a graft used in an aortocoronary procedure is a risk factor for early graft failure. We compared the effect on the endothelium of the mammary arteries when the harvest was done either by the harmonic scalpel (HS) or the high-frequency electrocauter (HF). METHODS Twenty-four mammary arteries were harvested and divided into two groups depending on the use of the HS or the HF. The endothelial damage was analyzed with a scanning electron microscope. The groups were compared in regard to the size of the internal mammary artery (IMA) pedicle. RESULTS The endothelial damage of the IMAs taken down with the HS was significantly less than when taken down with the HF if the IMA pedicle size was less than 0.5 cm. CONCLUSIONS The HS has a positive effect on the endothelial preservation, especially when the preparation is done closely to the IMA. The HS is profitable in minimally invasive procedures, particularly when it is difficult to keep a wide enough distance from the IMA.