C.-A. Greim

A simplified Risk score for predicting postoperative nausea and vomiting : Conclusions from Cross-validations between two centers

BACKGROUND Recently, two centers have independently developed a risk score for predicting postoperative nausea and vomiting (PONV). This study investigated (1) whether risk scores are valid across centers and (2) whether risk scores based on logistic regression coefficients can be simplified without loss of discriminating power. METHODS Adult patients from two centers (Oulu, Finland: n = 520, and Wuerzburg, Germany: n = 2202) received inhalational anesthesia (without antiemetic prophylaxis) for various types of surgery. PONV was defined as nausea or vomiting within 24 h of surgery. Risk scores to estimate the probability of PONV were obtained by fitting logistic regression models. Simplified risk scores were constructed based on the number of risk factors that were found significant in the logistic regression analyses. Original and simplified scores were cross-validated. A combined data set was created to estimate a potential center effect and to construct a final risk score. The discriminating power of each score was assessed using the area under the receiver operating characteristic curves. RESULTS Risk scores derived from one center were able to predict PONV from the other center (area under the curve = 0.65-0.75). Simplification did not essentially weaken the discriminating power (area under the curve = 0.63-0.73). No center effect could be detected in a combined data set (odds ratio = 1.06, 95% confidence interval = 0.71-1.59). The final score consisted of four predictors: female gender, history of motion sickness (MS) or PONV, nonsmoking, and the use of postoperative opioids. If none, one, two, three, or four of these risk factors were present, the incidences of PONV were 10%, 21%, 39%, 61% and 79%. CONCLUSIONS The risk scores derived from one center proved valid in the other and could be simplified without significant loss of discriminating power. Therefore, it appears that this risk score has broad applicability in predicting PONV in adult patients undergoing inhalational anesthesia for various types of surgery. For patients with at least two out of these four identified predictors a prophylactic antiemetic strategy should be considered.

Bovine haemoglobin is more potent than autologous red blood cells in restoring muscular tissue oxygenation after profound isovolaemic haemodilution in dogs

PurposeThis study compares the effects of stored red cells, freshly donated blood and ultrapurified polymerized bovine haemoglobin (HBOC) on haemodynamic variables, oxygen transport capacity and muscular tissue oxygenation after acute and almost complete isovolaemic haemodilution in a canine model.MethodsFollowing randomization to one of three groups, 24 anaesthetized Foxhounds underwent isovolaemic haemodilution with 6% hetastarch to haematocrit levels of 20%, 15% and 10% before they received isovolaemic stepwise augmentation of 1 g · dl−1 haemoglobin. In Group 1, animals were given autologous stored red cells which they had donated three weeks before. In Group 2, animals received freshly donated blood harvested during haemodilution. In Group 3, animals were infused with HBOC. Skeletal muscle tissue oxygen tension was measured with a polarographic 12 μ needle probe.ResultsIn all groups, heart rate and cardiac index were increased with decreasing vascular resistance during haemodilution (P < 0.05). Haemodynamic variables showed a reversed trend during transfusion when compared to haemodilution but remained below baseline (P < 0.05). Arterial and venous oxygen content were changed in parallel to changes of haematocrit and haemoglobin concentrations but were lower in Group 3 than in Groups 1 and 2 (P < 0.05) during transfusion. In contrast, the oxygen extraction ratio was higher in Group 3 (59 ± 8%, P < 0.01) at the end of transfusion than in Group 1 (37 ± 13%) and 2 (32 ± 5%). In Group 3, mean tissue oxygen tension increased from 16 ± 5 mmHg after haemodilution to 56 ± 11 mmHg after transfusion (P < 0.01) and was higher than in Group 1 (41 ± 9, P < 0.01) and Group 2 (29 ± 11, P < 0.01). While in Group 3 an augmentation of 0.7 g · dl−1 haemoglobin resulted in restoring baseline tissue oxygenation, higher doses of 2.7 g · dl−1 and 2.1 g · dl−1 were needed in Groups 1 and 2 to reach this level (P < 0.01).ConclusionThe results show a higher oxygenation potential of HBOC than with autologous stored red cells because of a more pronounced oxygen extraction.RésuméObjectifCette étude compare les effets des hématies conservées, du sang fraîchement prélevé et de l’hémoglobine bovine polymérisée ultrapurifiée (HBOC) sur les variables hémodynamiques, la capacité de transport en oxygène et l’oxygénation du tissu musculaire après hémodilution isovolémique aiguë et presque complète sur un modèle canin.MéthodesAprès randomisation en trois groupes, 24 fox-hounds ont subi, une hémodilution isovolémique en paliers avec de l’hétastarch à 6% pour réaliser des hématocrites de 20%, 15% et 10% avant de recevoir une augmentation iso-volémique en paliers de 1 g · dl−1 d’hémoglobine. Dans le groupe 1, les chiens ont reçu les hématies autologues conservées prélevées trois semaines auparavant. Dans le groupe 2, les animaux ont reçu de sang frais recueilli au moment de l’hémodilution. Dans le groupe 3, les animaux ont été perfusés avec HBCO. La tension en oxygène du tissus musculaire a été mesurée avec une sonde polarographique.RésultatsDans tous les groupes, la fréquence et l’index cardiaques ont augmenté avec la baisse de la résistance vasculaire pendant l’hémodilution (P < 0,05). Pendant la transfusion, les variables hémodynamiques ont révélé une tendance inverse de celle de l’hémodilution mais sont demeurées sous la ligne de base (P < 0,05). Pendant la transfusion, les contenus artériels et veineux eh oxygène ont changé parallèlement aux changements de l’hématocrite et de la concentration de l’hémoglobine mais étaient plus bas dans le groupe 3 que dans les groupes 1 et 2 (P < 0,05). Par contre, à la fin de la transfusion, l’extraction de l’oxygène a été plus grande dans le groupe 3 (59 ± 8%, P < 0,01) que dans les groupes 1 (37 ±13%) et 2 (31 ± 5%). Dans le groupe 3, après la transfusion, la tension tissulaire moyenne en oxygène a augmenté de 16 ±5 mmHg à 56 ± 11 mmHg (P < 0,01) et était plus élevée que dans les groupes 1(41 ± 9, P < 0,01) et 2 (29 ± 11,P < 0,01). Alors que dans le groupe 3, une augmentation de 0,7 g · dl−1 a permis de ramener l’oxygénation tissulaire à la ligne de base, des quantités plus grandes (2,7 g · dl−1 et de 2,2 g · dl−1) ont été requises pour atteindre ce niveau dans les groupes 1 et 2.ConclusionCes résultats montrent un potentiel d’oxygénation plus élevé avec HBCO qu ’avec des hématies autologues conservées en raison d’une extraction plus prononcée de l’oxygène.

Continuous cardiac output monitoring during adult liver transplantation : Thermal filament technique versus bolus thermodilution

Continuous thermodilution (CT) using a pulmonary artery (PA) catheter with a thermal filament has the potential for intraoperative on-line monitoring of cardiac output. Liver transplantation frequently requires rapid fluid administration and often includes the use of an extracorporeal veno-venous bypass. To assess the agreement between CT and bolus thermodilution (BT) in such a setting, we conducted a prospective intraoperative study in 14 liver transplant patients. Throughout the operation, CT cardiac output was recorded and paired with BT measurements taken every 30 min and whenever indicated for clinical reason. Corresponding data were assigned to acquisition periods when patients were on or off veno-venous bypass (flow rate 2.5 +/- 0.2 L/min) and were discriminated by the various range of intravenous infusion rates (<150 mL/h, 150-1000 mL/h, 1000-2000 mL/h, and 2000-4000 mL/h) and the magnitude of cardiac output (<or=to7.5 L/min, 7.5-10.0 L/min, >10.0 L/min). A total of 270 data pairs was obtained and examined by analysis of agreement (mean difference +/- SD), variance, error, and weighted regression. Trend analysis was performed for significant CT and BT cardiac output changes, defined as changes greater than 15%. Agreement of both methods was best at peripheral intravenous fluid infusion rates <or=to1000 mL/h and BT cardiac output >10 L/min (0.0 +/- 0.6 L/min) and was unaffected by veno-venous bypass. Discrepancy was most evident at intravenous fluid infusion rates >2000 mL/h and BT cardiac output <or=to7.5 L/min (2.1 +/- 1.7 L/min). Correlation of CT and BT cardiac output was excellent (r = 0.95, P < 0.001) for combined data from all patients. Changes in CT cardiac output >15% (n = 116) correctly indicated the direction in 93% of BT cardiac output changes and were 74% sensitive and 75% specific for significant BT cardiac output changes. The thermal filament technique enhances the usefulness of PA catheterization during liver transplantation but reflects BT cardiac output with clinically acceptable error only at low peripheral intravenous fluid infusion rates. Implications: Cardiac output determines organ perfusion. In clinical practice, it is measured by intermittent thermodilution using right heart catheterization. This intraoperative study compared the intermittent method with a technique based on continuous thermodilution. The new technique provides logistical advantages and challenges the accuracy of the intermittent method during liver transplantation. (Anesth Analg 1997;85:483-8)

Relation of echocardiographic preload indices to stroke volume in critically ill patients with normal and low cardiac index

Objective: To examine the usefulness of preload indices obtained by transoesophageal echocardiography (TOE) for estimating stroke volume at various levels of cardiac index. Design: Prospective clinical study. Setting: Intensive care unit with surgical patients. Patients: 16 ventilated patients monitored via Swan-Ganz catheterization and TOE. Interventions: Echocardiographic images of left ventricular cross-sectional short-axis areas were analysed for the preload indices end-diastolic area (EDA), stroke area and end-diastolic wall stress. The relation between these indices and stroke volume, calculated from thermodilution cardiac output, was analysed in all patients and in nine patient groups discriminated by various ranges in heart rate (≤ 70 to > 110 beats/min), pulmonary artery occlusion pressure (≤ 8 to > 12 mm Hg) and cardiac index (≤ 3.0 to > 4.2 l/min per m2). Measurements and results: Overall stroke volume (n = 155) correlated significantly (p < 0.0001) with EDA (r = 0.89) and stroke area (r = 0.80). The correlation with end-diastolic wall stress was non-significant (r = 0.51). Linearity in the relation between stroke volume and EDA or stroke area was independent of variations in heart rate and pulmonary artery occlusion pressure. Stroke volume correlated well with EDA and stroke area, when cardiac index was normal or high, but the relation slightly deteriorated (r = 0.63 to ≤ 0.72) when the cardiac index was low. Changes in EDA and stroke area by more than 1, 2 or 3 cm2 were weak predictors for changes in stroke volume greater than 20 %. Conclusions: Stability of the relation between echocardiographic preload indices and stroke volume emphasize the potential of TOE for continuous preload monitoring in the critically ill.

Effects of intra‐abdominal CO2‐insufflation on normal and impaired myocardial function: an experimental study

Background:  Intra‐abdominal pressure (IAP) elevation during CO2‐pneumoperitoneum increases cardiac afterload and may enhance dysfunction of the already compromized heart. This study focused on the effects of acute IAP increases on left and right ventricular loadings and contractility in the heart with impaired global function.

The detection of interatrial flow patency in awake and anesthetized patients: a comparative study using transnasal transesophageal echocardiography.

The Valsalva maneuver in the awake patient and the ventilation maneuver in the tracheally intubated anesthetized patient are two provocation methods to detect a patent foramen ovale (PFO) by means of contrast transesophageal echocardiography. In 60 patients undergoing posterior fossa surgery, a contrast agent was administered via a peripheral vein during a Valsalva maneuver immediately before anesthesia induction, followed by central venous administration during a ventilation maneuver in the same patients when anesthetized and endotracheally intubated. We evaluated both maneuvers with a 32-element monoplane transnasal transesophageal echocardiography probe to trace the atrial flow of the contrast agent in a 90° bicaval view. A maneuver was rated positive when more than four bubbles appeared in the left atrium during the first three cardiac cycles after intrathoracic pressure release. The right atrial cross-sectional area before pressure release, and the peak septal excursion during atrial contrast opacification, were measured. McNemar’s test was used to assess a paired dichotomous response on the two maneuvers for a significant difference. In 56 patients, the ventilation maneuver was significantly (P < 0.037) more often positive for PFO (n = 14) than the Valsalva maneuver (n = 7). Although there was no difference in the methods regarding the peak septal excursion, the mean right atrial area before pressure release was significantly smaller during the ventilation maneuver than during the Valsalva maneuver (11.2 ± 3.1 cm2 vs 14.4 ± 3.3 cm2, n = 42, P < 0.05). In the patients with a positive ventilation, but a negative Valsalva maneuver, the discrepancy was even larger (10.9 ± 4.4 cm2 vs 16.3 ± 4.2 cm2, n = 7, P < 0.001). We conclude that the ventilation maneuver is superior to the Valsalva maneuver in detecting PFO. Our data suggest that a peak pressure of 30 cm H2O during the ventilation maneuver achieves a more pronounced reduction in right atrial load and allows right atrial pressure to exceed left atrial pressure when intrathoracic pressure is released.

Ultraschallgesteuerte zentralvenöse Punktion bei neuropädiatrischen Patienten unter Vermeidung von potentiell hirndrucksteigernden Maßnahmen

ZusammenfassungFragestellung. Bestimmte Maßnahmen wie die Lagerung in der Trendelenburg-Position oder die Erhöhung des intrathorakalen Druckes erhöhen die Chance einer erfolgreichen Punktion der V. jugularis interna (VJI) insbesondere bei pädiatrischen Patienten. Sie sind bei Patienten mit pathologisch erhöhtem Hirndruck aber kontraindiziert.Aus diesem Grund untersuchten wir bei anästhesierten und beatmeten neuropädiatrischen Patienten, ob die sonographisch gesteuerte Punktion und Kanülierung der VJI diese Maßnahmen erübrigt. Methodik. In die Untersuchung wurden prospektiv 8 Neugeborene, 46 Säuglinge und 66 Kleinkinder aufgenommen,bei denen die Querschnittsfläche der rechten VJI in Horizontallage und 15°-Trendelenburg-Position sowie mit und ohne PEEP 0, 5 oder 10 cm H2O sonographisch vermessen und die VJI anschließend unter einer definierten Kombination von Lagerung und PEEP-Niveau unter sonographischer Kontrolle punktiert wurde (5- bis 8-MHz-Schallkopf). Ergebnisse. Die Querschnittsfläche der VJI lag in Horizontallage ohne PEEP bei 0,3–1,6 cm2 (n=120). Sie wurde durch die Trendelenburg-Position durchschnittlich um 24% und durch die zusätzliche Einstellung von PEEP 10 cm H2O durchschnittlich um 63% erhöht. In 98 % der Fälle waren die ultraschallgesteuerten VJI-Punktionen beim ersten Versuch – unabhängig von Lagerung und PEEP – erfolgreich; nur bei 2 Kindern war ein zweiter Punktionsversuch erforderlich. Schlussfolgerung. Unter sonographischer Darstellung des VJI-Querschnittes lässt sich dieses Gefäß bei Kleinkindern, Säuglingen und Neugeborenen ohne venenfüllende Maßnahmen,wie Trendelenburg-Lagerung oder Einstellung eines PEEP, einfach und sicher zum Zweck der zentralvenösen Kanülierung punktieren.SummaryBackground. Certain measures such as the Trendelenburg position or an increase in intrathoracic pressure raise the chances for a successful puncture of the internal jugular vein (IJV) particularly in paediatric patients. However, these measures are contraindicated in patients with increased intracranial pressure. Therefore, in anaesthetised and ventilated neuropaediatric patients we investigated whether ultrasound-guided cannulation of the IJV can replace these measures. Methods. In this prospective study,8 newborns, 46 infants and 66 small children were included.The cross-sectional area of the right IJV was sonographically measured in horizontal and 15° Trendelenburg positions with or without PEEP 0, 5 or 10 cm H2O.The IJV was then punctured at the conditions of a predetermined position and PEEP combination under sonographic guidance (5–8 MHz). Results. The mean cross-sectional area of the IJV was 0.3–1.6 cm2 in the horizontal position without PEEP (n=120) and was enlarged due to the Trendelenburg position by 24% and by 63%, when PEEP 10 cm H2O was added. Independent of positioning and PEEP the ultrasound-guided puncture was successful at the first attempt in 98% of cases and a second attempt had to be made in only two children. Conclusions. Under sonographic visualisation of the cross-sectional area, the IJV can easily and safely be punctured for central venous cannulation in newborn, infants and small children without measures such as the Trendelenburg position or implementation of PEEP.

Transnasal transesophageal echocardiography : A modified application mode for cardiac examination in ventilated patients

UNLABELLED In 42 endotracheally intubated patients, we examined the utility of a miniaturized monoplane probe for transnasal transesophageal echocardiography (TEE). Transnasal TEE was prospectively evaluated in 26 deeply and 16 mildly sedated patients receiving topical anesthesia with lidocaine jelly 2%. The patients with deep sedation were additionally examined with transoral monoplane and multiplane TEE. Transnasal esophageal insertion of the TEE probe was successfully performed in 90% of patients. Endotracheal malpositioning was corrected in two patients. Nasal bleeding required treatment in another patient. Topical anesthesia was adequate in 82% of mildly sedated patients. Left ventricular short- and four-chamber long-axis views of good quality were obtained with transnasal (transoral) monoplane TEE in 76% (81%) and 92% (96%) of patients (differences not significant). Compared with conventional multiplane TEE, transnasal monoplane TEE missed diagnoses in 19% of patients. The relative error (mean +/- SEM) of quantification with transnasal TEE was <9% +/- 2% for ventricular diameters and <7% +/- 2% for cross-sectional area measurements, with a bias of 0.5 +/- 3.8 cm2 and 0.1 +/- 2.4 cm2 (mean +/- 2 SD) for left ventricular end-diastolic and end-systolic short-axis areas. The relative error in measuring intracardiac flow velocities was >40%, but systolic to diastolic peak velocity ratios at the valvular site were determined with an error <4% +/- 3%. Transnasal monoplane TEE can be performed even in mildly sedated patients with an endotracheal tube without further need for analgesia or sedation. The technique is as useful as conventional transoral TEE to image standard tomographic planes for quantification, but it is less suited for comprehensive echocardiographic diagnosing. IMPLICATIONS Transnasal insertion of a miniaturized monoplane transesophageal echocardiography (TEE) probe was studied in endotracheally intubated patients. Nasal passage was well tolerated even by patients with only mild sedation. Imaging quality was similar to conventional transoral monoplane TEE with larger transducers, but technical restraints cause a deficit in complete cardiac diagnosing obtained with multiplane TEE.

Ultrasound-guided cannulation of the internal jugular vein in critically ill patients positioned in 30° dorsal elevation

Background and objective: Catheterization of the internal jugular vein is traditionally performed with the patient lying flat or in the Trendelenburg position. This puts patients with elevated intracranial pressure at risk of cerebral herniation. The objective of this study was to assess the safety of real-time ultrasound-guided catheterization of the internal jugular vein in ventilated patients with the patient positioned in a 30° head-up position. Methods: This prospective, single-centre case series was performed in a 12-bed multi-disciplinary adult intensive care unit (ICU) in a 1500-bed university hospital. The cohort consisted of 64 ventilated ICU patients (14 female, 50 male) with a median age of 52 yr (range 18-85 yr), needing central venous cannulation for insertion of a central venous, haemodialysis or pulmonary artery catheter. The majority of patients presented with risk factors for a difficult cannulation. Catheterization was performed using real-time ultrasound guidance with all patients positioned in 30° dorsal elevation. Results: Ultrasound-guided cannulation of the internal jugular vein was successful in all patients. There was no evidence of air embolism. Despite a high incidence of anomalous anatomy (39%) no injury to the carotid artery occurred. Central venous access was established in less than 1 min in 75% of patients. Conclusion: Ultrasound-guided cannulation of the internal jugular vein in ventilated ICU patients can be performed successfully with the patient positioned in 30° dorsal elevation. Potentially deleterious position changes can thus be avoided in high-risk patients.

Abschätzung akuter linksventrikulärer Nachlaständerungen

ZusammenfassungBei 21 beatmeten Intensivpatienten wurden akute linksventrikuläre Nachlaständerungen unter Noradrenalin oder Nitroglyzerin mittels der transösophagealen Echokardiographie (TEE) überwacht. Mit der TEE wurde die linksventrikuläre endsystolische Myokardspannung (endsystolischer „wall stress``, WS) im zweidimensionalen Verfahren (2D) und im M-mode-Verfahren (M) bestimmt und diese beiden Nachlastparameter mit dem systemischen Gefäßwiderstand (SVR) verglichen. Änderungen der linksventrikulären Nachlast wurden von allen drei Kenngrößen in der Richtung übereinstimmend erfaßt, in Relation zur WS2D jedoch durch die WSM und den SVR um 15–30% geringer eingeschätzt. WS2D, WSM und SVR korrelierten untereinander nicht. Der berechnete geometrische Faktor der WS2D reflektierte die Größenveränderung des linken Ventrikels unter der Behandlung sowohl mit Noradrenalin als auch mit Nitroglyzerin, der geometrische Faktor der WSM dagegen nicht. Aus den Ergebnissen ist zu schließen, daß die WS2D ein besserer Parameter für die Abschätzung akuter linksventrikulärer Nachlaständerungen ist als die WSM. Die Abschätzung der linksventrikulären endsystolischen Myokardspannung mit dem SVR ist nicht möglich.AbstractLeft ventricular afterload is most accurately represented by left ventricular end-systolic wall stress, but in clinical practice is commonly estimated by the systemic vascular resistance (SVR). End-systolic wall stress can be derived from M-mode and two-dimensional (2D) echocardiograms in combination with systolic arterial pressure (SAP). We tested transoesophageal echocardiography for the assessment of acute left ventricular afterload alterations in ventilated patients requiring cardiovascular support with noradrenaline or nitroglycerine. Method. With approval from the local ethics committee, we studied afterload alterations in 11 hypotensive patients who were treated by increasing the dosage of IV noradrenaline by 2–5 μg/min in order to raise mean arterial pressure (MAP) by 20 mmHg. In another 10 patients with MAP over 95 mmHg, nitroglycerine was raised from 2 to 4 mg/h, aiming at a 20 mmHg MAP reduction. MAP and SAP were monitored via a radial artery cannula, cardiac output (CO) was measured with the thermodilution technique using a Swan-Ganz catheter, and SVR was calculated from CO, MAP, and right atrial pressure. M-mode and 2D echocardiograms were obtained from the cross-sectional short-axis view of the left ventricle and recorded shortly before and during treatment when MAP had changed by 20 mmHg. Left ventricular total area (TA) and cavity area (A) including the papillary muscles were obtained from end-systolic 2D echocardiograms, while end-systolic internal diameter (ID) and posterior wall thickness (HW) were measured in the M-mode. Wall stress was calculated in the M-mode as: WSM=0.33 · SAP · ID/(HW · (1+HW/ID)), and in the 2D mode as: WS2D=1.33 · SAP · A/(TA-A). Statistics: paired t-test (P<0.05), regression analysis. Results. Afterload alterations were reflected by significant changes of WS2D (―41%, +68%), WSM (―26%, +38%), and SVR (―15%, +50%). WSM and SVR underestimated changes of WS2D by 15%–30%. WSM changes due to SAP rather than to left-ventricular dimensional changes. No correlation was found between WS2D or WSM and SVR. Inter-observer variability for echocardiographic wall stress was reasonable (WS2D 4%, WSM 10%). Conclusions. Acute changes of left ventricular afterload and dimensions were clearly indicated by 2D measurements. As M-mode measures were not conclusive for left ventricular dimensional changes, WSM was not an appropriate parameter for acute afterload alterations. WS2D is an afterload index superior to WSM that cannot be estimated by SVR.