Prognostic value of postoperative high-sensitivity troponin T in patients with different stages of kidney disease undergoing noncardiac surgery.

BACKGROUND: Emerging evidence suggests that postoperative troponin release is a strong and independent predictor of short-term mortality. However, evaluating elevated troponins in patients with chronic kidney disease (CKD) is still controversial and is often disregarded. This study examines morbidity along with short- and long-term mortality risk associated with elevated high-sensitivity troponin T (hsTnT) in patients with different stages CKD undergoing noncardiac surgery. METHODS: This observational cohort comprised 3262 patients aged ≥60 yr who underwent noncardiac surgery. Postoperative hsTnT concentrations were divided into normal [<14 ng l-1 (reference)], low (14-49 ng l-1), moderate (50-149 ng l-1), and high (≥150 ng l-1) groups. A threshold of 50 ng l-1 was used to dichotomize hsTnT. The study endpoints were 30-day and long-term all-cause mortality, and postoperative myocardial infarction. RESULTS: Postoperative hsTnT was associated with a stepwise increase in 30-day and long-term mortality risk: low hsTnT adjusted hazard ratio (HR) 1.4 [95% confidence interval (CI): 1.1-1.7], moderate hsTnT adjusted HR 3.1 (95% CI: 2.3-4.3), high hsTnT adjusted HR 5.5 (95% CI: 3.6-8.4). Postoperative hsTnT ≥50 ng l-1 was associated with 30-day and long-term mortality risk for each stage of CKD. Elevated troponin concentrations in severe CKD (estimated glomerular filtration rate <30 mL min-1 1.73 m-2), however, did not predict short-term death. CONCLUSIONS: Elevated postoperative hsTnT is associated with a dose-dependent increase in 30-day and long-term mortality risk in each stage of CKD with an estimated glomerular filtration rate ≥30 ml min-1 1.73 m-2.

Association between postoperative mean arterial blood pressure and myocardial injury after noncardiac surgery.

BACKGROUND: Myocardial injury after noncardiac surgery is common, although the exact pathophysiology is unknown. It is plausible that hypotension after surgery is relevant for the development of myocardial injury. The authors evaluated whether low mean arterial pressures (MAPs) after surgery are related to an increased incidence in postoperative cardiac-troponin elevation. METHODS: A prospective cohort of 2211 patients aged ≥60 yr, undergoing major or moderate noncardiac surgery in The Netherlands, was retrospectively analysed for the occurrence of postoperative cardiac-troponin elevation [high-sensitive troponin T (hsTnT) >14 ng L-1]. Blood pressures after surgery were recorded and divided into quartiles based on the lowest MAP prior to peak troponin recording. The association between MAP and extent of postoperative cardiac-troponin elevation was analysed. RESULTS: The patients were divided into quartiles based on their lowest MAP in the period preceding the peak hsTnT, ranging from a median of 62 in the lowest quartile to 94 in the highest quartile. Postoperative hsTnT elevation was present in 53.2% of the population. An association between MAP quartile and postoperative peak hsTnT was predominantly observed in the lowest quartile (P<0.001): median hsTnT 17.6 (10.3-37.3), 14.9 (9.4-24.6), 13.8 (9.1-22.5), and 14.0 (9.2-22.4). The multivariable logistic-regression analysis showed an increased risk for postoperative cardiac-troponin elevation with decreasing MAP thresholds. CONCLUSIONS: Lower postoperative blood pressure is associated with an increased incidence of postoperative cardiac hsTnT elevation, irrespective of pre- and intraoperative variables.

The value of arterial pressure waveform cardiac output measurements in the radial and femoral artery in major cardiac surgery patients.

BACKGROUND: A relatively new uncalibrated arterial pressure waveform cardiac output (CO) measurement technique is the Pulsioflex-ProAQT® system. Aim of this study was to validate this system in cardiac surgery patients with a specific focus on the evaluation of a difference in the radial versus the femoral arterial access, the value of the auto-calibration modus and the ability to show fluid-induced changes. METHODS: In twenty-five patients scheduled for ascending aorta, aortic arch replacement, or both we measured CO simultaneously by transpulmonary thermodilution (COtd) and by using the ProAQT® system connected to the radial (COpR), as well as the femoral artery catheter (COpF). Hemodynamic data were assessed at predefined time points; from incision until 16 h after ICU admission. RESULTS: In total 175 (radial) and 179 (femoral) pairs of CO measurement were collected. The accuracy of COpR/COpF was evaluated showing a mean bias of -0.31 L/min (±2.9 L/min) and -0.57 L/min (± 2.8 L/min) with percentage errors of 49 and 46% respectively. Trending ability of the ProAQT® device was evaluated; the four quadrant concordance rates in the radial and femoral artery were 74 and 75% and improved to 77 and 85% after auto-calibration. The mean angular biases in the radial and femoral artery were 6.4° and 6.0° and improved to 5° and 3.3° after auto-calibration. The polar concordance rates in the radial and femoral artery were 65 and 70% and improved to 76 and 84% after auto-calibration. Considering the fluid-induced changes in stroke volume(SV), the coefficient of correlation between the changes in SVtd and SVp was 0.57 (p < 0.01) in the radial artery and 0.60 (p < 0.01) in the femoral artery. CONCLUSIONS: The ProAQT® system can be of additional value if the clinician wants to determine fluid responsiveness in cardiac surgery patients. However, the ProAQT® system provided inaccurate CO measurements compared to transpulmonary thermodilution. The trending ability was poor for COpR but moderate for COpF. Auto-calibration of the system did not improve accuracy of CO measurements nor did it improve the prediction of fluid responsiveness. However, the trending ability was improved by auto-calibration, possibly by correcting a drift over a longer time period.

[Organ donation after circulatory death]. / Organspende nach Herz- und Kreislauftod.

Approximately 17 million inhabitants live in the Netherlands. The number of potential organ donors in 1999 was the lowest in Europe with only 10 donors per million inhabitants. Medical associations, public health services, health insurance companies and the government had to find common solutions in order to improve organ allocation, logistics of donations and to increase the number of transplantations. After a prolonged debate on medical ethical issues of organ transplantation, all participants were able to agree on socio-medico-legal regulations for organ donation and transplantation. In addition to improving the procedure for organ donation after brain death (DBD) the most important step was the introduction of organ donation after circulatory death (DCD). Measures such as the introduction of a national organ donor database, improved information to the public, further education on intensive care units (ICU), guidelines for end of life care on the ICU, establishment of transplantation coordinators on site, introduction of autonomous explantation teams and strict procedures on the course of organ donations, answered many practical issues about logistics and responsibilities for DBD and DCD. In 2014 the number of postmortem organ donations rose to 16.4 per million inhabitants. Meanwhile, up to 60 % of organ donations in the Netherlands originate from a DCD procedure compared to approximately 10 % in the USA. This overview article discusses the developments and processes of deceased donation in the Netherlands after 15 years of experience with DCD.

[Cardiac preload and central venous pressure]. / Kardiale Vorlast und zentraler Venendruck.

The force of cardiac contraction is strongly influenced by myocardial fibre length at the beginning of systole. Because the length of cardiac sarcomers and muscle fibres primarily depends on the end-diastolic ventricular volume, filling pressures a priori can only act as indirect parameters of cardiac preload. Central venous pressure (CVP) gives information on right ventricular end-diastolic pressure, which parallels changes in left ventricular end-diastolic pressure as long as ventricular function is not impaired. Since the pressure-volume relationship of cardiac ventricles is not linear and shows great variability, filling of the ventricles cannot be directly derived from end-diastolic pressure. Further limitations of CVP as a surrogate variable of preload are caused by the influence of intrathoracic and intra-abdominal pressures. A valid parameter of preload should describe the relationship between preload and stroke volume as given by the Frank-Starling law. Furthermore, estimates of cardiac preload should enable prediction of fluid responsiveness. Many studies have demonstrated that under clinical conditions CVP cannot meet these demands and thus does not appear to be a useful predictor of cardiac preload. Variables which more directly represent end-diastolic ventricular volume (e.g. intrathoracic blood volume or end-diastolic ventricular area) offer a higher validity as estimates of cardiac preload. Furthermore, dynamic parameters of ventricular preload, such as pulse pressure variation or stroke volume variation, seem to be more predictive of volume responsiveness in ventilated patients than CVP. These limitations, however, do not impair the importance of CVP as the downstream pressure of the systemic venous system.

Phlebitis rate and time kinetics of short peripheral intravenous catheters.

BACKGROUND: An observational prospective cohort study was carried out on complication rates and time kinetics of phlebitis caused by short peripheral intravenous catheters (PIVCs) in inpatients on 15 hospital wards in four hospitals in Cologne, Germany. PATIENTS AND METHODS: We observed 1,582 patients with 2,495 PIVCs daily using standardized questionnaires. Phlebitis was defined using modified Centers for Disease Control and Prevention (CDC) criteria. RESULTS: Average phlebitis rates were 27 per 100 patients and 104 per 1,000 catheter days. Median duration of PIVC was 2 days (25 percentile = 2 days; 75 percentile 3 days). Time kinetics (Kaplan-Meier) were linear. CONCLUSION: Linear time kinetics of PIVC phlebitis do not support CDC recommendations for an elective PIVC change after 72 hours, provided daily monitoring of the insertion site occurs.

[Color duplex sonographic findings in an iatrogenic arteriovenous fistula of the vertebral artery]. / Farbduplexsonographische Befunde bei iatrogener arteriovenöser Fistel der A. vertebralis.

The report describes a rare case of an iatrogenic arteriovenous fistula of the vertebral artery to the vertebral vein which arose after insertion of a central venous catheter via the jugular vein. We give special attention to the role of colour duplex sonography in the primary diagnosis of such fistulas. As can be seen from published reports with this non-invasive examination, the diagnosis of fistulas could not be established in all cases, where an abnormal communication between the vessels was later revealed by angiography. The most probable reason is the particular feature of the anatomical course of the vertebral artery which in its middle third is protected in a bony canal through the foramina transversaria of the cervical vertebrae and can be only partially visualised by sonography. Consequently only fistulas in the visible parts of the artery can be detected by sonography. In our case the most important criteria of duplex sonography for an arteriovenous fistula were fulfilled and the diagnosis was confirmed by angiography. This procedure with primary use of colour duplex sonography and additional clarification of uncertain findings by angiography, seems to be reasonable if the symptoms are compatible with the diagnosis of an arteriovenous fistula of the neck vessels.

[The Cologne Guidelines Conference: computer-assisted clinical practice guidelines in clinical diagnosis]. / Die Kölner Leitlinien-Konferenz: Computergestützte Leitlinien zur klinischen Diagnostik.

Eighteen clinical practice guidelines on interdisciplinary diagnostic issues were developed at the University Hospital of Cologne, Germany. The guideline committee is organized and directed by the quality control program, which also includes the local Cochrane initiative and a wide range of organizational topics. During guideline development, questions of differential diagnosis were addressed to the same extent as the organizational and financial realization. Broad consideration was given to medicolegal implications, but need for interspecialty cooperation was judged to be more critical and even more relevant in this regard. Guidelines were primarily developed as algorithms and translated to text versions secondarily. Critical steps in the decision tree were supported by rated literature and recommendations weighte by criteria as used in evidence-based medicine. For implementation, guidelines were presented to colleagues in a series of short lectures, as print versions containing all literature used in the developing process, and in hypertext format, which is accessible via intranet. Three levels of presentation were chosen in the html-version: algorithm, decision, and information. The former is due to orientation in the guideline, the second displays the binary question, and the latter makes the scientific background available, together with literature and links for more information. Efforts to check effectiveness are currently been made, questions of efficiency will be addressed in future.

The effects of increased doses of bovine hemoglobin on hemodynamics and oxygen transport in patients undergoing preoperative hemodilution for elective abdominal aortic surgery.

UNLABELLED: In two consecutive studies (Study A and Study B), we evaluated the effects of increasing doses of HBOC-201, a bovine hemoglobin-based oxygen carrier, on hemodynamics and oxygen transport in patients undergoing preoperative hemodilution for elective abdominal aortic surgery. After the induction of anesthesia and the exchange of 1 L of blood for 1 L of lactated Ringer's solution, 24 patients (12 in each study) were randomly assigned to receive, within 30 min, a predetermined volume of either HBOC-201 or 6% hydroxyethyl starch (Study A 6.9 mL/kg; Study B 9.2 mL/kg). Monitored variables included systemic and pulmonary arterial pressures, arterial and mixed venous blood gases, and calculations of cardiac index (CI), systemic (SVRI) and pulmonary (PVRI) vascular resistance indices, oxygen delivery index (DO2I), oxygen consumption index (VO2I), and oxygen extraction ratio (O2ER). In both studies, the infusion of HBOC-201 was associated with increases in SVRI (Study A 121%; Study B 71%) and PVRI (Study A 70%; Study B 53%) and with a decrease in CI (29% both studies). Hemodilution with HBOC-201 maintained the arterial oxygen content at levels higher than hemodilution with hydroxyethyl starch, but the advantage of a greater oxygen-carrying capacity was offset by the increase in SVRI, with a resulting net decrease in both CI and DO2I (Study A 30%; Study B 28%); VO2I was maintained by increased O2ER. In terms of hemodynamics and oxygen transport, hemodilution with bovine hemoglobin in these doses provided no apparent benefit over hemodilution with hydroxyethyl starch. IMPLICATIONS: Bovine hemoglobin in doses ranging between 55 and 97 g of hemoglobin increased vascular resistance and decreased cardiac output in anesthetized surgical patients. In terms of hemodynamics and oxygen transport, hemodilution with bovine hemoglobin in these doses provided no apparent benefit over hemodilution with hydroxyethyl starch.

Influence of arterial carbon dioxide tension on systemic vascular resistance in patients undergoing cardiopulmonary bypass.

BACKGROUND: The effects of induced hypothermia in cardiac surgical patients are not yet fully understood. Despite numerous studies on the effects of acid-base management on organ blood flow, only little information is available on the effects of alpha-stat versus pH-stat management on systemic haemodynamics. We therefore compared the effect of alpha-stat and pH-stat acid-base management on systemic haemodynamics in a prospective, controlled, cross-over study. METHODS: Twenty patients undergoing coronary artery bypass surgery were included in the study. Cardiac output was measured by thermodilution. Cardiac index and systemic vascular resistance were calculated according to standard formulae. Measurements were performed under hypo- and hypercapnia after induction of anaesthesia. Measurements were repeated at the end of two 30-min periods of pH-stat and alpha-stat acid-base management, respectively. RESULTS: Systemic vascular resistance at the lower PaCO2-levels (hypocapnia and alpha-stat, respectively) was significantly higher than those at the higher level (hypercania and pH-stat, respectively). The periods of different PaCO2-levels were comparable with respect to haematocrit, blood viscosity and temperature. Systemic vascular resistance was not significantly different from the control period. CONCLUSIONS: This study demonstrates that during hypothermic cardiopulmonary bypass, systemic vascular resistance under alpha-stat acid-base management is higher than under pH-stat management. As obvious from measurements during the control period, this finding can be completely explained by the difference in PaCO2.

[The effect of nitroglycerin on cerebrovascular circulation, cerebrovascular CO2-reactivity and blood flow rate in basal cerebral arteries]. / Einfluss von Nitroglyzerin auf Hirndurchblutung, zerebrovaskuläre CO2-Reaktivität und Blutflussgeschwindigkeit in basalen Hirnarterien.

UNLABELLED: The cerebral haemodynamic effects of vasodilators are of clinical interest because a decrease in mean arterial pressure (MAP) might alter global cerebral blood flow (CBF). Luxury perfusion of the brain, contrast, might be unfavourable in patients with reduced intracranial compliance. Despite the widespread use of nitroglycerine (NTG), little is known about the cerebral haemodynamic consequence of NTG infusions in humans. This prospective, controlled study was designed: (1) to investigate the effects of NTG on CBF and cerebrovascular CO2 reactivity and (2) to compare reference measurements of global CBF with transcranial Doppler monitoring (TCD) of middle cerebral artery flow velocity (VMCA). METHODS: With ethical committee approval and informed patient consent, we investigated ten patients undergoing coronary artery bypass surgery. Measurements were performed under fentanyl/midazolam anaesthesia prior to the start of the operation. First, during a baseline period, ventilation was changed in a random sequence to achieve two different levels of arterial PCO2 (30 and 50 mmHg, respectively). Consequently, measurements were repeated during i.v. infusion of 1.5.micrograms.kg-1.min-1 NTG at identifical PCO2 levels. Measurements of CBF were performed by the Kety-Schmidt technique with argon as an indicator. Simultaneously, VMCA was recorded by use of a 2-Mhz transcranial Doppler system. Cerebral perfusion pressure (CPP) was calculated from the difference between MAP and jugular bulb pressure. Statistical analysis was performed by two-way analysis of variance using a repeated-measures design to assess the effects of NTG application and respiratory changes, respectively. RESULTS: During NTG infusion, CPP decreased slightly by 15-17%. Because of a reduction in cerebrovascular resistance, CBF increased at both levels of PaCO2 by 96 and 69%, respectively. However, VMCA decreased concomitantly. Cerebrovascular CO2 reactivity did not change. CONCLUSIONS: This study demonstrates that during fentanyl/midazolam anaesthesia NTG may cause a major increase in CBF as long as CPP does not decrease considerably. Our results further suggest that NTG causes vasodilation of basal cerebral arteries, inducing a discrepancy between relative changes in CBF and VMCA. Consequently, TCD measurements during infusion of NTG should not be directly compared with preceding measurements of MCA flow velocity.

Effects of a hemoglobin-based oxygen carrier (HBOC-201) on hemodynamics and oxygen transport in patients undergoing preoperative hemodilution for elective abdominal aortic surgery.

We conducted a pilot study to evaluate the effects of HBOC-201, a bovine hemoglobin-based oxygen carrier, on hemodynamics and oxygen transport in patients undergoing preoperative hemodilution for elective abdominal aortic surgery. After induction of anesthesia and isovolemic hemodilution with 1 L of lactated Ringer's solution, 13 patients were randomly assigned to receive, within 30 min, 3 mL/kg of either HBOC-201 or 6% hydroxyethyl starch (HES). Monitored variables included invasive arterial and pulmonary artery pressures, arterial and mixed venous blood gases, and calculations of cardiac index (CI), systemic and pulmonary vascular resistance indices, oxygen delivery index (DO2I), oxygen consumption index (VO2I), and oxygen extraction ratio (O2ER). Thirty minutes after HBOC-201 infusion, mean arterial pressure, systemic vascular resistance index, and CI were 149% (P = 0.028), 169% (P = 0.046), and 75% (P = 0.46) of the preinfusion values, respectively. No significant changes were noticed in heart rate and pulmonary vascular resistance index. DO2I and VO2I, 30 min after the infusion of HBOC-201, were 79% (P = 0.046) and 76% (P = 0.028) of the preinfusion values, respectively, whereas CaO2 and O2ER remained unaffected. We conclude that HBOC-201, at a dose of 3 mL/kg, impairs oxygen delivery because of adverse effects on cardiac output.

Effect of ketanserin on global cerebral blood flow and middle cerebral artery flow velocity.

The aim of this study was to examine the influence of ketanserin, a 5-hydroxytryptamine antagonist antihypertensive agent, on the relationship between cerebral blood flow (CBF) and middle cerebral artery flow velocity (Vmean MCA) and to compare Doppler-sonographic indices of downstream resistance (pulsatility index, PI; resistance index, RI) with calculations of cerebrovascular resistance (CVR) in 17 male patients under fentanyl/midazolam anesthesia. CBF was measured with the Kety-Schmidt technique using argon as a tracer. Cerebral perfusion pressure (CPP) was calculated as the difference between mean arterial pressure (MAP) and jugular bulb pressure. Measurements of Vmean MCA and determinations of PI and RI were performed by use of a 2-MHz transcranial Doppler ultrasound device. All variables were measured at normo- and moderate hypocapnia before and after intravenous (i.v.) bolus administration of 0.3 mg/kg ketanserin followed by an infusion of 0.06 mg.kg-1.h-1. Ketanserin changed neither average CBF nor Vmean MCA. The CO2 reactivity of Vmean MCA was significantly lower than the CO2 reactivity of CBF (P < 0.01); however, ketanserin did not change the relationship between CBF and Vmean MCA. During hypocapnia, CVR as well as PI and RI significantly increased (P < or = 0.01), indicating consistent directional changes in arteriolar resistance and flow velocity pulsatility. In contrast, after i.v. administration of ketanserin, CVR decreased (P < 0.05), whereas both Doppler-derived indices increased (P < 0.01). These results suggest that ketanserin in a clinically relevant dose does not alter the validity of serial Vmean MCA measurements as an index of global CBF and that ketanserin does not change the diameter of middle cerebral arteries (MCAs). Doppler-derived indices of pulsatility and resistance, which are supposed to estimate changes in downstream resistance, reflect changes, after administration of ketanserin, in systemic hemodynamics rather than changes in CVR.

Flow velocity measurements as an index of cerebral blood flow. Validity of transcranial Doppler sonographic monitoring during cardiac surgery.

BACKGROUND: Transcranial Doppler sonography is increasingly used to monitor changes in cerebral perfusion intraoperatively. However, little information is available about the validity of velocity measurements as an index of cerebral blood flow (CBF). The purpose of this study was to compare invasive and Doppler-derived measurements of cerebral hemodynamic variables during coronary artery bypass graft surgery. METHODS: In 15 male patients, measurements of CBF and middle cerebral artery flow velocity (VMCA) were performed before and after induction of fentanyl-midazolam anesthesia, during hypothermic cardiopulmonary bypass (CPB), and at the end of the surgical procedure. Transcranial Doppler sonography recordings of systolic, diastolic, and mean VMCA, and derived parameters such as pulsatility (PI) and resistance (RI) indexes were recorded from the proximal segment of the right middle cerebral artery. CBF was measured by the Kety-Schmidt inert gas saturation method with argon as a tracer. To facilitate comparisons of CBF and VMCA measurements, changes between consecutive measurements were expressed as percentage values. Calculations of cerebral perfusion pressure and cerebral vascular resistance (CVR) were based on jugular bulb pressure. The cerebral metabolic rate for oxygen was calculated from CBF and the arterial-cerebral venous oxygen content difference. RESULTS: Changes in mean VMCA paralleled changes in mean CBF except for hemodynamic changes associated with hypothermic CPB. At this stage of surgery, mean VMCA increased while actual CBF decreased. Separate analysis of the periods before and after CPB revealed a poor association between percentage changes in CBF and VMCA (r = 0.26, P = 0.36; r = 0.51, P = 0.06, respectively). Mean values of CVR, PI, and RI showed consistent changes after induction of anesthesia. After termination of CPB, mean CVR significantly decreased, whereas mean PI and RI remained virtually unchanged. Neither before nor after CPB was a clinically useful correlation found between percentage changes in PI, RI, and CVR (PI r = 0.28, P = 0.34; r = -0.47, P = 0.09, respectively; RI r = 0.16, P = 0.59; r = -0.53, P = 0.06, respectively). CONCLUSIONS: Hypothermic CPB seems to alter the relation between global CBF and flow velocity in basal cerebral arteries. Inconsistency in directional changes in CBF and VMCA at this stage of surgery might be attributable to changes in middle cerebral artery diameter, red blood cell velocity spectra, and regional flow distribution. Although changes in mean VMCA before and after CPB appear to parallel changes in mean CBF, individual responses of VMCA cannot reliably predict percentage changes in CBF. Furthermore, Doppler sonographic PI and RI cannot provide an approximation of changes in CVR during cardiac surgery.