Postoperative Cardiac Surgery Patients Research Articles

Postoperative confusion assessed with the Short Portable Mental Status Questionnaire.

Confusion is a common occurrence after cardiac surgery. However, there is great variability in the reported incidence of confusion in patients following cardiac surgery, mainly due to the diagnostic methods and instruments employed in assessing confusion. Forty-eight cardiac surgery patients were assessed for postoperative confusion by a non-structured physician interview, and by the short portable mental status questionnaire (SPMSQ) administered by a medical student. The non-structured ward interviews detected confusion in one of the 48 patients (2%), whereas the SPMSQ diagnosed confusion in 15 of the 48 patients (31%). Unlike a subjective ward interview, the SPMSQ is a brief and objective diagnostic tool that can be used to measure accurately both the presence and severity of confusion in postoperative cardiac surgery patients.

Decreased cardiac output: validation with postoperative heart surgery patients.

This study was done to analyze the association between defining characteristics of decreased cardiac output (DCO) identified by noninvasive methods and the cardiac index (CI) estimated by thermodilution. Two defining characteristics were associated with DCO: decreased peripheral pulse and decreased peripheral perfusion. This study points out the relevance of peripheral circulation assessment in postoperative cardiac surgery patients.

Lactic acidosis after cardiac surgery is associated with polymorphisms in tumor necrosis factor and interleukin 10 genes

Background. Lactic acidosis after cardiac surgery is a manifestation of excess cytokine production. Cytokine-related genetic polymorphisms account for variability in cytokine response and may predispose to the development of lactic acidosis after cardiac surgery. Methods. Routine postoperative cardiac surgery patients were studied. Lactic acid levels were greater than 4 mmol/L in study patients and less than 4 mmol/L in controls. Polymerase chain reaction-based techniques were used to examine carriage of tumor necrosis factor β (TNF-β), TNF G-308A, and interleukin 10 (IL-10) G-1082A alleles. Results. Demographic characteristics and details of surgery were similar for 30 control and 21 study patients. Lactic acid levels after intensive care admission changed over time and were related to both TNF-β and IL-10 G-1082A polymorphisms. All 4 study patients homozygous for TNF-β1 and carrying an IL-10–1082A allele developed lactic acidosis ( p = 0.02). There was no relation between the rate of epinephrine infusion or duration of cardiopulmonary bypass and lactic acid levels. Conclusions. Genetic factors have a role in the development of lactic acidosis after cardiac surgery.

Equivalence of bioimpedance and thermodilution in measuring cardiac index after cardiac surgery

Objective: To compare thoracic electrical bioimpedance (TEB) cardiography versus pulmonary artery thermodilution (TD) derived cardiac index in patients after cardiopulmonary bypass. Design: Prospective, blinded electronic data collection. Setting: Intensive care unit of a military hospital. Participants: Post–cardiopulmonary bypass patients for primary comparison between technologies (n = 20) and patients for comparison of variability within each technology (n = 20). Interventions: None. Measurements and Main Results: Cardiac index values by TEB or TD were collected simultaneously. Linear regression, Lin's concordance correlation coefficient, bias, and precision measures within the large data set group and within each patient over time were calculated. Linearity in regression and Lin's concordance correlation coefficient of 0.99 were shown. A bias of 0.07 L/min/m2 and precision of 0.40 L/min/m2 were within acceptable clinical limits, as were equivalence test results. Conclusions: TEB is equivalent to TD-derived cardiac index in postoperative cardiac surgery patients. Copyright 2002, Elsevier Science (USA). All rights reserved.

Setting a New Gold Standard

Setting a New Gold Standard

Early metabolic and splanchnic responses to enteral nutrition in postoperative cardiac surgery patients with circulatory compromise

To assess the hemodynamic and metabolic adaptations to enteral nutrition (EN) in patients with hemodynamic compromise. Prospective study in a university hospital surgical ICU, comparing baseline (fasted) with continuous EN condition. Nine patients requiring hemodynamic support by catecholamines (dobutamine and/or norepinephrine) 1 day after cardiac surgery under cardiopulmonary bypass. Isoenergetic EN via a postpyloric tube while catecholamine treatment remained constant. Baseline (fasted) condition was compared to continuous EN condition. Cardiac index (CI), mean arterial pressure (MAP), pulmonary and wedge pressures, indocyanine green (ICG) clearance, gastric tonometry, plasma glucose and insulin, and glucose turnover (6,62H2-glucose infusion) were determined repetitively every 60 min during 2 h of baseline fasting condition and 3 h of EN. During EN CI increased (from 2.9 +/- 0.5 to 3.3 +/- 0.5 l min-1 m-2), MAP decreased transiently (from 78 +/- 7 to 70 +/- 11 mmHg), ICG clearance increased (from 527 +/- 396 to 690 +/- 548 ml/min), and gastric tonometry remained unchanged, while there were increases in glucose (158 +/- 23 to 216 +/- 62 mg/dl), insulin (29 +/- 23 to 181 +/- 200 mU/l), and glucose rate of appearance (2.4 +/- 0.2 to 3.3 +/- 0.2 mg min-1 kg-1). The introduction of EN in these postoperative patients increased CI and splanchnic blood flow, while the metabolic response indicated that nutrients were utilized. These preliminary results suggest that the hemodynamic response to early EN may be adequate after cardiac surgery even in patients requiring inotropes.

Jejunal and gastric mucosal perfusion versus splanchnic blood flow and metabolism: an observational study on postcardiac surgical patients.

To evaluate the association between changes in total splanchnic and mucosal perfusion, assessed either by gastric tonometry or jejunal laser Doppler flowmetry in postcardiac surgical patients. A prospective, observational study. A general intensive care unit in a tertiary care center. Twelve, postoperative cardiac surgery patients were studied. Patients were treated according to clinical routine. Total splanchnic blood flow (indocyanine green extraction), jejunal mucosal perfusion (laser Doppler flowmetry), gastric mucosal-arterial PCO2 gradients, and splanchnic lactate uptake were studied during four 30-min measurements periods, each separated by a period of 1 hr. There was no consistent association between either total splanchnic and local mucosal perfusion or between gastric and jejunal perfusion as assessed by two different techniques. The PCO2 gradient increased from 0.73+/-0.21 kPa to 1.15+/-0.30 kPa (p < .05), and splanchnic oxygen extraction increased from 40%+/-9% to 49%+/-14% (p < .01). In this observational study on postcardiac surgical patients, local mucosal perfusion did not reflect total splanchnic blood flow and vice versa. Either changes in gastric and jejunal mucosal perfusion were different or increasing tissue metabolism was responsible for the observed lack of association between tonometry, laser Doppler flowmetry, and total splanchnic blood flow. Increasing mucosal arterial PCO2 gradient and splanchnic oxygen extraction may reflect a mismatch between splanchnic perfusion and metabolic demands.

Detection of artifacts in monitored trends in intensive care

In intensive care, decision-making is often based on trend analysis of physiological parameters. Artifact detection is a pre-requisite for interpretation of trends both for clinical and research purposes. In this study, we developed and tested three methods of artifact detection in physiological data (systolic, mean and diastolic artery and pulmonary artery pressures, central venous pressure, and peripheral temperature) using pre-filtered physiological signals (2-min median filtering) from 41 patients after cardiac surgery. These methods were: (1) the Rosner statistic; (2) slope detection with rules; and (3) comparison with a running median (median detection). After tuning the methods using data from 20 randomly chosen patients, the methods were tested using the data from the remaining patients. The results were compared with those obtained by manual identification of artifacts by three senior intensive care unit physicians. Out of an average of 22 480 data points for each variable, the three observers labelled 0.98% (220 data points) as artifacts. The inter-observer agreement was good. The average (range) sensitivity for artifact detection in all variables in the test database was 66% (33–92%) for the Rosner statistic, 64% (24–98%) for slope detection and 72% (41–98%) for median detection. All methods had a high specificity (≥94%). Slope detection had the highest mean positive prediction rate (53%; 21–85%). When the performance was measured by the cost function, slope detection and running median performed equally well and were superior to Rosner statistics for systemic arterial and central venous pressure and peripheral temperature. None of the methods produced acceptable results for pulmonary artery pressures. We conclude that median filtering of physiological variables is effective in removing artifacts. In post-operative cardiac surgery patients, the remaining artifacts are difficult to detect among physiological and pathophysiological changes. This makes large databases for tuning artifact algorithms mandatory. Despite these limitations, the performance of running median and slope detection were good in selected physiological variables.

Effect of ambient temperature and cardiac stability on two methods of cardiac output measurement.

The dependence of cardiac output measurement precision on ambient temperature and cardiac output stability was assessed by concurrent continuous and bolus thermodilution methods in postoperative cardiac surgery patients. The degree of agreement between the two methods was depended on room temperature (0.1 L/min for each degree below 25 degrees C). The agreement was also closer in trials where cardiac output was stable (< 10% variation). The continuous thermodilution method shows sufficient agreement with the bolus method for use in critical care; however, improved precision of cardiac output thermodilution measurements can be achieved by use of correction factors for cardiac instability and for ambient temperature.

VENOARTERIAL CO2 GRADIENT AFTER CARDIAC SURGERY

The difference in CO2 tension between venous and arterial blood (delta PCO2) increases in low-flow states. Therefore, delta PCO2 has been suggested as an additional variable in the monitoring of perfusion. We measured CO2 tensions in arterial, mixed venous, hepatic venous, and femoral venous blood in 42 postoperative cardiac surgery patients. Splanchnic and leg blood flow was measured with dye dilution. Forty-three preoperative abdominal surgery patients served as controls. Systemic and femoral delta PCO2 was increased in cardiac patients, whereas there was no difference in splanchnic delta PCO2 between the groups. In cardiac patients, systemic delta PCO2 correlated well with both splanchnic and femoral delta PCO2 (r2 = .74 and r2 = .56, respectively). Femoral delta PCO2 was higher than splanchnic delta PCO2 (1.27 +/- .44 kPa versus .66 +/- .41; p < .001) after cardiac surgery, but not in the control group. The correlation between delta PCO2 and respective blood flow was weak in the whole body, the splanchnic region, and the leg. When splanchnic blood flow was low, systemic and splanchnic delta PCO2 varied widely. In the cardiac patients with an increased systemic delta PCO2 (> .93 kPa), systemic and regional blood flow was low, but there were no differences in systemic or regional oxygen consumption or lactate levels. After cardiac surgery, high systemic delta PCO2 is associated with marginal systemic and regional perfusion. The adequacy of regional blood flow cannot be assessed on the basis of the systemic delta PCO2.

Positive pressure inspiration differentially affects right and left ventricular outputs in postoperative cardiac surgery patients

Purpose : The purpose of this study was to determine the dynamic changes in right ventricular (RV) and left ventricular (LV) output during positive airway pressure inspiratory hold maneuvers so as to characterize the interaction of processes in creating steady-state cardiac output during positive pressure ventilation. Materials and Methods : We examined the disparity of RV and LV outputs at 5 seconds (early) and 20 seconds (late) into a 25-second inspiratory hold maneuver in 14 subjects in the intensive care unit immediately following coronary artery bypass surgery. RV output was measured by the thermodilution technique, whereas LV output was measured by the arterial pulse contour method. RV and LV volumes were also measured by thermal and radionuclide ejection fraction techniques, respectively. Results : As P aw was progressively increased from 0 to 20 cm H 2O in sequential inspiratory hold maneuvers, both RV and LV outputs changed differently both at 5 seconds and 20 seconds into the inspiratory hold maneuvers. When expressed as change in cardiac output (L/min) for every cm H 2O Paw increase relative to end-expiratory values, RV output increased at 5 seconds (0.05 ± 0.15 L/min) then decreased at 20 seconds (−0.08 ± 0.21, P < .05). LV output decreased slightly at 5 seconds (−0.14 ± 0.22) and did not change from this minimal depressed level at 20 seconds ( P < .05). Changes in RV and LV output were paralleled by changes in RV and LV end-diastolic volumes, respectively. Conclusion : Positive pressure inspiration induces time-dependent changes in central hemodynamics, which are dissimilar between RV and LV function. Initially, inspiration increases RV output but decreases LV output, such that intrathoracic blood volume increases. However, sustained inspiratory pressures induce proportionally similar decreases in both RV and LV outputs. Thus, the hemodynamic effects of positive pressure ventilation will depend on the degree of lung inflation, the inspiratory time, and when measurements are made within the ventilatory cycle. These data also suggest that positive pressure ventilation with up to 20 cm H 2O P aw does not significantly impair ventricular performance in humans.

Effect of lateral position on arterial and venous blood gases in postoperative cardiac surgery patients

Investigators have suggested that lateral position may have clinically significant effects on oxygenation in cardiac surgery patients. Presence of lung disease and type of cardiac surgery may be important considerations. To determine the effect of position (left, right, supine) on blood gases in patients who have had coronary artery bypass or cardiac valvular surgery and to compare the effect of position on blood gases in cardiac surgery patients having preoperatively diagnosed lung disease with those having no lung disease. A repeated measures design was used to study 120 mechanically ventilated, postoperative cardiac surgery patients. Subjects were randomly assigned a sequence of three positions (supine, and 45; right and left lateral) after cardiac surgery. Heart rate, respiratory rate, and arterial blood gas values were collected in each position. Venous blood gas values were collected from a subset of 40 subjects. A statistically significant effect of position on PaO2 was found in the group as a whole. The mean PaO2 in the left lateral position was lower than the value in the right or supine positions. No significant effects for position and pH, PaCO2, or bicarbonate were detected. No significant effects were found for type of surgery or the presence of absence of preoperative lung disease. A significant effect of position on venous pH was detected. No significant position effects were found for PvO2, PvCO2, bicarbonate, or venous saturation. No significant position effects were found for the calculated arterial-venous oxygen difference. The results of this study support those of previous research, which reported lower PaO2 in postoperative coronary artery bypass graft patients in the left lateral position. Mean differences in PaO2 were small, suggesting that the known benefits of lateral positioning in the early postoperative period outweigh the potential risks.

Effects of Peep in postoperative cardiac surgery patients

We conclude that low levels of PEEP have no particular advantage over zero PEEP in improving arterial and tissue oxygenation, during the early postoperative period, following open heart surgery.

Usefulness of measures of Svo 2, Spo 2, vital signs, and derived dual oximetry parameters as indicators of arterial blood gas variables during weaning of cardiac surgery patients from mechanical ventilation

To determine whether combined use of the parameters of mixed venous oxygen saturation, arterial oxygen saturation obtained by pulse oximetry (Spo2), and vital signs correlated with arterial blood gas variables (ABGs) better than each individual variable during weaning of postoperative cardiac surgery patients from mechanical ventilation; and to evaluate the relationship of derived parameters: oxygen extraction index and ventilation/perfusion index (VQI), and ABGs. Secondary analysis of previous correlational study. The cardiac care unit in a large medical center in central Florida. Thirty postoperative coronary artery bypass graft patients being weaned from mechanical ventilation. After a change in ventilator settings during systematic weaning towards extubation, measurements of variables were taken during a 30-minute period. At 30 minutes, an ABG was drawn for comparison. Data were collected after two ventilator changes. A total of 57 data sets were used for analysis. By use of multiple regression analyses, statistically significant (p < 0.01) independent variables predicting pH and partial pressure of carbon dioxide were Spo2 and respiratory rate. The independent variable contributing to the model versus partial pressure of oxygen was Spo2. The oxygen extraction index did not correlate with ABGs; however, the VQI correlated significantly with all ABG variables except bicarbonate. The use of multiple parameters was no more useful in predicting ABGs than individual variables of Spo2 and respiratory rate. The derived VQI parameter correlated with ABGs. The use of VQI in conjunction with Spo2 and respiratory rate may assist in patient monitoring during weaning and reduce the number of ABGs needed.

Lack of Association Between Atelectasis and Fever

Postoperative fever occurs in many patients. If no infection is found, atelectasis, if present, may be blamed. This study of 100 postoperative cardiac surgery patients followed up from day of surgery through the second postoperative day with daily portable chest radiographs and continuous bladder thermometry was designed to look for an association between atelectasis and fever. The daily incidence of atelectasis increased from 43 to 69 to 79%. However, the incidence of fever, defined as temperature > or = 38.0 degrees C fell from 37 to 21 to 17%. When defined as temperature > or = 38.5 degrees C, the daily incidence of fever fell daily from 14 to 3 to 1%. Using chi 2 analysis, no association could be found between fever and amount of atelectasis. This contradicts common textbook dogma but agrees with previous human study and animal experiments.

Effect of position on selected hemodynamic parameters in postoperative cardiac surgery patients

Indirect/noninvasive blood pressure, heart rate and central venous pressure are frequently monitored hemodynamic parameters in postoperative cardiac surgery patients. No previous studies have explored the effect of lateral position on these variables in this population. To determine differences in (1) blood pressure, central venous pressure, or heart rate measurements among postoperative cardiac surgery patients due to position (supine, 45 degrees right lateral, and 45 degrees left lateral), (2) responses to position between patients having cardiac surgery in which the myocardium was opened (valvular replacement) and those in which it was not (coronary artery bypass graft), and (3) responses to position between cardiac surgery patients having preoperatively diagnosed lung disease and those without lung disease. Phlebostatic axis in lateral positions was determined by echocardiography and geometric diagrams prior to the initiation of data collection. Postoperative cardiac surgery patients (N = 120) were studied in the three positions in random sequences. In each position, simultaneous blood pressure measurements were obtained from each arm, and central venous pressure and heart rate were recorded. Statistically significant differences were found in response to position in systolic and diastolic blood pressure, central venous pressure, and heart rate. Certain positions produced greater changes in selected variables, both in the total group and within specific subgroups. No differences were found between coronary artery bypass graft and valve (closed or opened myocardium) subgroups or between subgroups with and without lung disease. Lateral positioning of postoperative cardiac surgery patients appears to cause no detrimental effects on indirect/noninvasive blood pressure or heart rate measurements. However, significant differences in central venous pressure may occur and supine positioning for determination of central venous pressure is recommended.

Timing and predictors of death in pediatric patients with multiple organ system failure.

To describe the timing of onset of organ system failure, multiple organ system failure diagnosis, and the subsequent death in children admitted to a pediatric intensive care unit (ICU). Second, to identify independent risk markers of death in pediatric patients with multiple organ system failure. Review of a database. Pediatric ICU within a tertiary care center. We analyzed the pediatric ICU course of 777 consecutive patients aged < 18 yrs. Eighty-five (10.9%) of 777 children had multiple organ system failure, defined as the simultaneous occurrence of at least two organ system failures. Of 85 children, 37 (43.5%) were postoperative cardiac surgery patients and 48 (56.5%) patients were in the ICU for other reasons. The diagnostic criteria for multiple organ system failure were met on the day of admission by 73 (86%) of 85 patients. The maximum number of organ system failures occurred within 72 hrs in 74 (87%) children. The mortality rate for all patients with multiple organ system failure was 50.6%. Thirty-eight (88.4%) of deaths occurred within 7 days after the diagnosis of multiple organ system failure. Survival analysis was comparable for both postoperative cardiac surgery patients and patients with other diagnoses. Multivariate analysis identified three factors as independent risk markers of death in pediatric patients with multiple organ system failure: maximum number of simultaneous organ system failures during the pediatric ICU stay: odds ratio, 55.9 (95% confidence interval, 7.9 to 396.1); age < or = 12 months: odds ratio, 17.1 (95% confidence interval, 1.8 to 158.7); and the Pediatric Risk of Mortality (PRISM) score on the day of admission: odds ratio, 1.25 (95% confidence interval, 1.1 to 1.5). The mortality rate associated with multiple organ system failure in pediatric patients is high. The maximum number of simultaneous organ system failures during pediatric ICU stay, age < or = 12 months, and the PRISM score on the day of admission are independent risk markers of death. Diagnosis of multiple organ system failures, development of maximum number of organ system failures, and deaths occur remarkably early after pediatric ICU admission; the rationale for using prophylactic therapy under such circumstances is unclear.

Intraoperative and Postoperative Effects of Vancomycin Administration in Cardiac Surgery Patients

ROMANELLI, V. A.; HOWIE, M. B.; MYEROWITZ, P. D.; ZVARA, D. A.; REZAEI, A.; JACKMAN, D. L.; SINCLAIR, D. S.; MCSWEENEY, T. D. Author Information

Rewarming Cardiac Surgery Patients

This study compared time required to rewarm, incidence of shivering, and nurses' preferences in hypothermic postoperative cardiac surgery patients treated with a forced air warmer (Bair Hugger) or a noninfrared radiant heater (Thermal Ceiling). Data were collected on 38 subjects and 6 nonsubjects treated with warm blankets. Average minutes to rewarm were: forced air, 100.3; radiant heat, 99.3; and warm blankets, 188.2. The warm air subjects had significantly higher skin temperatures, lower incidence of shivering, and less severe afterdrop, suggesting that rewarming in these patients resulted from heat gained from the environment. Nurses preferred the forced air warmer to the noninfrared radiant heater.

Analgesics for cardiac surgery patients in critical care: describing current practice

In the last 10 years, the American Association of Critical-Care Nurses has twice ranked pain management as a priority issue for research and practice. Recent research findings suggest that undermedication of patients continues both in and out of critical care. Postoperative cardiac surgery patients have reported detailed recollections of pain experiences while in critical care, yet little is known about management of postoperative cardiac surgery pain. The purpose of this study was to describe current practice related to analgesic prescription and administration for postoperative cardiac surgery patients in critical care. Medical records of 80 adults undergoing cardiac surgery in two hospitals were randomly selected for review. Data pertaining to pain medications prescribed and doses administered for the day of surgery, first and second postoperative days were recorded for 66 eligible subjects. All but one patient had a prescription for intravenous morphine, hourly as needed. In addition, all patients had prescriptions for one or more oral analgesics as needed. Gender and age effects were noted for analgesic prescriptions. The average total amount of intravenous morphine given over the 3 days was 13.9 +/- 13.5 mg in an average of 4 +/- 3.7 doses. The average total number of acetaminophen with oxycodone tablets given over the 3 days was 5.8 +/- 5.4 tablets in an average of 3.6 +/- 3.0 doses. Age and hospital effects were noted in the administration of analgesics. The finding of small and infrequent analgesic doses is consistent with other studies conducted in and out of critical care. Important inconsistencies, or variations in practice, exist in both the prescription and administration of analgesics for postoperative cardiac surgery patients in the critical care setting.