Hauke Paarmann

Preoperative regional cerebral oxygen saturation is a predictor of postoperative delirium in on-pump cardiac surgery patients: a prospective observational trial

IntroductionPostoperative delirium is an important problem in patients undergoing major surgery. Cerebral oximetry is a non-invasive method to detect imbalances in the cerebral oxygen supply/demand-ratio. Low preoperative cerebral oxygen saturation (ScO2) levels have been associated with postoperative delirium in non-cardiac surgery patients. The present prospective observational study determines the relationship between pre- and intra-operative ScO2 levels and postoperative delirium in patients undergoing on-pump cardiac surgery.MethodsAfter approval of the local ethical committee and written informed consent, N = 231 patients scheduled for elective/urgent cardiac surgery were enrolled. Delirium was assessed by the confusion-assessment-method for the intensive care unit (CAM-ICU) on the first three days after surgery. ScO2 was obtained on the day before surgery, immediately before surgery and throughout the surgical procedure. Preoperative cognitive function, demographic, surgery related, and intra- and post-operative physiological data were registered.ResultsPatients with delirium had lower pre- and intra-operative ScO2 readings, were older, had lower mini-mental-status-examination(MMSE) scores, higher additive EuroScore and lower preoperative haemoglobin-levels. The binary logistic regression identified older age, lower MMSE, neurological or psychiatric disease and lower preoperative ScO2 as independent predictors of postoperative delirium.ConclusionsThe presented study shows that a low preoperative ScO2 is associated with postoperative delirium after on-pump cardiac surgery.

Lack of agreement between pulmonary arterial thermodilution cardiac output and the pressure recording analytical method in postoperative cardiac surgery patients

BACKGROUND Pulse-contour analysis method (PCM) cardiac output (CO) monitors are increasingly used for CO monitoring during anaesthesia and in the critically ill. Very recently, several systems have been introduced that do not need calibration; among them the pressure recording analytical method (PRAM). Sparse data comparing the accuracy of the PRAM-CO with conventional thermodilution CO (ThD-CO) in cardiac surgery patients are available. METHODS In this prospective comparison study, paired CO measurements with a pulmonary artery catheter and a PRAM monitoring set were obtained 20-30 min apart (t1, t2) in 23 extubated patients on the first postoperative day after cardiac surgery. Data were analysed by the Bland-Altman method. RESULTS A total of 46 paired CO measurements (23 for each interval) were collected. The Bland-Altman analysis showed a mean difference (bias) of 0.0 litre min(-1) and limits of agreement (1.96 sd) of 4.53 to -4.54 litre min(-1) [upper 95% confidence interval (CI), 3.26-5.80; lower 95% CI, -5.8 to -3.27]. The percentage error (1.96 sd/mean of the reference method) was 87%. CONCLUSIONS These results question the reliability of the PRAM technology for the determination of CO in postoperative cardiac surgery patients.

Growth differentiation factor 15: a novel risk marker adjunct to the EuroSCORE for risk stratification in cardiac surgery patients.

OBJECTIVES This study sought to determine the usefulness of plasma growth differentiation factor 15 (GDF-15) for risk stratification in patients undergoing cardiac surgery in comparison with the additive European System of Cardiac Operative Risk Evaluation (EuroSCORE), N-terminal pro-B-type natriuretic peptide (NTproBNP), and high-sensitive troponin T (hsTNT). BACKGROUND GDF-15 is emerging as a humoral marker for risk stratification in cardiovascular disease. No data are available if this marker may also be used for risk stratification in cardiac surgery. METHODS In total, 1,458 consecutive patients were prospectively studied. Pre-operative plasma GDF-15, NTproBNP, hsTNT, clinical outcomes, and 30-day and 1-year mortality were recorded. GDF-15 was determined with a pre-commercial electrochemiluminescence immunoassay. RESULTS Median additive EuroSCORE (addES) was 5 (interquartile range: 3 to 8); 30-day and 1-year mortality were 3.4% and 7.6%, respectively. Median GDF-15 levels were 1.04 ng/ml (95% confidence interval [CI]: 1.0 to 1.07 ng/ml) in 30-day survivors and 2.62 ng/ml (95% CI: 1.88 to 3.88) in 30-day nonsurvivors (p < 0.0001). C-statistics showed that the area under the curve of a combined model of GDF-15 and addES for 30-day mortality was significantly greater (0.85 vs. 0.81; p = 0.0091) than of the addES alone. For the EuroSCORE categories (0 to 2, 3 to 5, 6 to 10, >10) the presence of GDF-15 ≥1.8 ng/ml resulted in a significant 41.4% (95% CI: 19.2 to 63.7%; p < 0.001) net reclassification improvement and an integrated discrimination improvement of 0.038 (95% CI: 0.022 to 0.0547; p < 0.0001) compared to the model including only the addES, whereas the presence of NTproBNP (cutoff ≥2,000 pg/ml) or hsTNT (cutoff 14 pg/ml) did not result in significant reclassification. CONCLUSIONS The pre-operative plasma GDF-15 level is an independent predictor of post-operative mortality and morbidity in cardiac surgery patients, can further stratify beyond established risk scores and cardiovascular markers, and thus adds important additional information for risk stratification in these patients. (The Usefulness of Growth Differentiation Factor 15 [GDF-15] for Risk Stratification in Cardiac Surgery; NCT01166360).

A perioperative infusion of sodium bicarbonate does not improve renal function in cardiac surgery patients: a prospective observational cohort study

IntroductionCardiac-surgery-associated-acute-kidney-injury (CSA-AKI) is associated with increased morbidity and mortality. Recent data from patients undergoing on-pump coronary artery bypass grafting suggest that a perioperative infusion of sodium-bicarbonate may decrease the incidence of CSA-AKI. The present study aims to analyze the renoprotective effects of a 24h infusion of sodium-bicarbonate in a large, heterogeneous group of cardiac surgical patientsMethodsStarting in 4/2009, all patients undergoing cardiac surgery at our institution were enrolled in a prospective trial analyzing the relationship between preoperative cerebral oxygen saturation and postoperative organ dysfunction. We used this prospectively sampled data set to perform a cohort analysis of the renoprotective efficiency of a 24h continuous perioperative infusion of sodium-bicarbonate on the incidence of CSA-AKI that was routinely introduced in 7/2009. After exclusion of patients with endstage chronic kidney disease, off-pump procedures, and emergency cases, perioperative changes in renal function were assessed in 280 patients treated with a perioperative infusion of 4 mmol sodium-bicarbonate / kg body weight in comparison with a control cohort of 304 patients enrolled from April to June in this prospective cohort study.Postoperative changes in urine flow, plasma creatinine, estimated creatinine clearance, and the need for renal replacement therapy were determined according to AKI injury network criteria. Concomitantly, hemodynamics, treatments, complications, and clinical outcomes were recorded. Univariate statistical analyses were performed para- and nonparametrically, as appropriate.ResultsWith the exception of a lower prevalence of a history of myocardial infarction and a lower preoperative use of intravenous heparin in the bicarbonate-group, no significant between group differences in patient demographics, surgical risk, type, and duration of surgery were observed. Patients in the bicarbonate group had a lower mean arterial blood pressure after induction of anesthesia, needed more fluids, more vasopressors, and a longer treatment time in the high dependency unit. Despite a higher postoperative diuresis, no differences in the incidence of AKI grade 1 to 3 and the need for renal replacement were observed.ConclusionsRoutine perioperative administration of sodium bicarbonate failed to improve postoperative renal function in a large population of cardiac surgical patients.

Haemodynamic performance of a new pericardial aortic bioprosthesis during exercise and recovery: comparison with pulmonary autograft, stentless aortic bioprosthesis and healthy control groups

OBJECTIVES Since blood flow impairment by aortic valve prosthesis is characteristically dynamic, this dynamic component is best and thoroughly appreciated by exercise Doppler echocardiography. We sought to determine the haemodynamics of a new pericardial aortic bioprosthesis [Trifecta™-aortic valve bioprosthesis (T-AVB), St Jude Medical, MN, USA] at rest and during exercise and a 10-min recovery period in comparison with alternative aortic valve prostheses, e.g. Ross operation (RO), stentless aortic valve [Medtronic freestyle-aortic valve bioprosthesis (MF-AVB)] and a healthy control group (CO). METHODS Haemodynamics at rest and during supine exercise stress testing and a 10-min recovery period were evaluated in 32 patients (mean age: 70.8 ± 6.7 years) with T-AVB (mean follow-up: 5 ± 2 months), 49 with RO (mean age: 43.5 ± 13.7 years), 39 with an MF-AVB (mean age: 64.6 ± 9.4 years) and 26 healthy patients (mean age: 39 ± 9 years). Measurements included mean outflow tract gradient (δp mean, mmHg), effective orifice area index (EOAI, cm(2)/m(2)) and valvular resistance (vR, dyn s cm(-5)). RESULTS Mean body surface area for T-AVB was 1.93 ± 0.24 m(2) (median 1.97 m(2)). Mean δp mean at rest was 7.2 ± 3.4 mmHg, mean EOAI 0.86 ± 0.23 cm(2)/m(2) and mean vR 50.7 ± 23.2 dyn s cm(-5). Supine stress testing did increase the mean EOAI to 0.98 ± 0.27 cm(2)/m(2), the mean vR to 62.6 ± 25.3 dyn s cm(-5) and the mean δp mean to 10.21 ± 4.7 mmHg, respectively (P < 0.05 for all comparisons). During the post-exercise recovery period, δp mean, EOAI and vR showed a prompt normalization within 5 min of cessation of exercise. At all the three measurement points, T-AVB and MF-AVB revealed low gradients, satisfactory EOAI and low vR. Compared with the RO and a healthy control group, both groups showed significantly inferior performance throughout the exercise and post-exercise study protocol (P < 0.05). In comparison with T-AVB, patients with an MF-AVB only showed significant inferior performance throughout series with respect to a higher vR, indicating a smaller increase in the EOAI during exercise. During the 10-min post-exercise period, T-AVB recovered significantly earlier than MF-AVB. CONCLUSIONS When comparing two different types of aortic valve bioprostheses with a gold standard group (RO) and a healthy population, both aortic valve bioprostheses perform inferior but reveal promising haemodynamics during exercise. During post-exercise haemodynamic recovery, only the T-AVB revealed a nearly physiological recovery pattern compared with the RO and a healthy control group.

The association of non-invasive cerebral and mixed venous oxygen saturation during cardiopulmonary resuscitation

Mixed venous oxygen saturation (SvO(2)) is an accepted surrogate parameter for the ratio between oxygen delivery and demand and may thus be used to determine the adequacy of the function of the cardiopulmonary system. Cerebral oxygen saturation monitoring by near infrared spectroscopy is a non-invasive method for the determination of the cerebral oxygen delivery to demand ratio that is applicable outside the operating room or the intensive care unit and does not require calibration. The present case highlights the agreement of non-invasive cerebral and SvO(2) in an 87-year-old female cardiac surgery patient with severe aortic stenosis scheduled for transapical aortic valve replacement during prolonged cardiopulmonary resuscitation.

Positive end‐expiratory pressure titration at bedside using electrical impedance tomography in post‐operative cardiac surgery patients

Post‐operative positive end‐expiratory pressure (PEEP) setting to minimize the risk of ventilator‐associated lung injury is still controversial. Assessment of regional ventilation distribution by electrical impedance tomography (EIT) might be superior as compared with global parameters. The aim of this prospective observational study was to compare global dynamic compliance (CRS) with different EIT indices during a short clinical applicable descending PEEP trial.

Postoperative intubation time is associated with acute kidney injury in cardiac surgical patients

IntroductionAcute kidney injury (AKI) is a frequent complication after cardiac surgery and is associated with a poor prognosis. Mechanical ventilation is an important risk factor for developing AKI in critically ill patients. Ventilation with high tidal volumes has been associated with postoperative organ dysfunction in cardiac surgical patients. No data are available about the effects of the duration of postoperative respiratory support in the immediate postoperative period on the incidence of AKI in patients after cardiac surgery.MethodWe performed a secondary analysis of 584 elective cardiac surgical patients enrolled in an observational trial on the association between preoperative cerebral oxygen saturation and postoperative organ dysfunction and analyzed the incidence of AKI in patients with different times to extubation. The latter variable was graded in 4 h intervals (if below 16 h) or equal to or greater than 16 h. AKI was staged according to the AKI Network criteria.ResultsOverall, 165 (28.3%) patients developed AKI (any stage), 43 (7.4%) patients needed renal replacement therapy. Patients developing AKI had a significantly (P <0.001) lower renal perfusion pressure (RPP) in the first 8 hours after surgery (57.4 mmHg (95% CI: 56.0 to 59.0 mmHg)) than patients with a postoperatively preserved renal function (60.5 mmHg ((95% CI: 59.9 to 61.4 mmHg). The rate of AKI increased from 17.0% in patients extubated within 4 h postoperatively to 62.3% in patients ventilated for more than 16 h (P <0.001). Multivariate logistic regression analysis of variables significantly associated with AKI in the univariate analysis revealed that the time to the first extubation (OR: 1.024/hour, 95% CI: 1.011 to 1.044/hour; P <0.001) and RPP (OR: 0.963/mmHg; 95% CI: 0.934 to 0.992; P <0.001) were independently associated with AKI.ConclusionWithout taking into account potentially unmeasured confounders, these findings are suggestive that the duration of postoperative positive pressure ventilation is an important and previously unrecognized risk factor for AKI in cardiac surgical patients, independent from low RPP as an established AKI trigger, and that even a moderate delay of extubation increases AKI risk. If replicated independently, these findings may have relevant implications for clinical care and for further studies aiming at the prevention of cardiac surgery associated AKI.

Urodilatin and Pentoxifylline Prevent the Early Onset of Escherichia coli-Induced Acute Renal Failure in a Model of Isolated Perfused Rat Kidney

Background/Aims: Raised cytokine levels and a hypoperfusion-associated decrease in glomerular filtration rate (GFR) are hallmarks of the genesis of septic acute renal failure (ARF). Therefore, anti-inflammatory as well as renal vasodilating therapeutic strategies may afford renal protection during septic ARF. The present study was designed to determine the effects of administration of urodilatin, pentoxifylline and theophylline to improve renal function in an ex-vivo model of ‘septic renal injury’. Methods: Eight series of experiments were performed: no intervention, perfusion with a suspension containing Escherichia coli bacteria (strain 536/21); E. coli + 10 μg/l urodilatin, E. coli + 20 μg/l urodilatin, E. coli + 100 μM theophylline, E. coli + 100 μM pentoxifylline and E. coli + URO 20 μg/l given 90 min after start of perfusion. Renal vascular and glomerular functional parameters as well as TNF-α release were analyzed up to 180 min. Results: Perfusion with E. coli caused an acute deterioration of renal vascular and glomerular function. URO 20 μg/l and PTX decreased renal vascular resistance (RVR) from 83.7 ± 18.4 to 9.2 ± 1.1 and 8.6 ± 2.2 mm Hg/ml/min/g kidney and increased renal perfusion flow rate (PFR) from 8.2 ± 1.5 to 14.6 ± 0.8 and 14.1 ± 2.2 ml/min/g kidney. As a result, GFR improved from 102.1 ± 15.6 to 442 ± 48.3 and 525.8 ± 57 μl/min/g kidney during treatment with URO 20 μg/l and PTX, respectively. Renal TNF-α release was significantly reduced by URO 20 μg/l (from 178 ± 23 to 45.2 ± 2 and 47 ± 3 pg/ml) in the E. coli + URO 20 μg/l and by PTX in the E. coli + PTX group if added to the perfusion medium upon start of perfusion. Interestingly, URO 20 μg/l also decreased RVR significantly from 62.2 ± 6.1 to 35.9 ± 6.0 mm Hg/ml/min/g kidney, improved PFR from 5.4 ± 1.0 to 8.7 ± 1.0 ml/min/g kidney, increased GFR from 160 ± 43.3 to 280.7 ± 27.9 μl/min/g kidney, and decreased TNF-α release to 122 ± 18 pg/ml if applied 90 min after induction of septic ARF. In contrast, URO 10 μg/l did not significantly increase urine flow and did not appear to significantly improve renal perfusion. Theophylline showed no beneficial effects at all. Conclusion: This suggests that urodilatin and pentoxifylline might be useful to protect renal function if given before a septic renal insult. Additionally, treatment with urodilatin is capable of restoring renal function in early Gram-negative sepsis-induced ARF even if given after the septic insult.

The suitability of EIT to estimate EELV in a clinical trial compared to oxygen wash-in/wash-out technique.

Abstract Introduction: Open endotracheal suctioning procedure (OSP) and recruitment manoeuvre (RM) are known to induce severe alterations of end-expiratory lung volume (EELV). We hypothesised that EIT lung volumes lack clinical validity. We studied the suitability of EIT to estimate EELV compared to oxygen wash-in/wash-out technique. Methods: Fifty-four postoperative cardiac surgery patients were enrolled and received standardized ventilation and OSP. Patients were randomized into two groups receiving either RM after suctioning (group RM) or no RM (group NRM). Measurements were conducted at the following time points: Baseline (T1), after suctioning (T2), after RM or NRM (T3), and 15 and 30 min after T3 (T4 and T5). We measured EELV using the oxygen wash-in/wash-out technique (EELVO2) and computed EELV from EIT (EELVEIT) by the following formula: EELVEITTx,y…=EELVO2+ΔEELI×VT/ΔZ. EELVEIT values were compared with EELVO2 using Bland-Altman analysis and Pearson correlation. Results: Limits of agreement ranged from -0.83 to 1.31 l. Pearson correlation revealed significant results. There was no significant impact of RM or NRM on EELVO2-EELVEIT relationship (p=0.21; p=0.23). Discussion: During typical routine respiratory manoeuvres like endotracheal suctioning or alveolar recruitment, EELV cannot be estimated by EIT with reasonable accuracy.