Current concepts in preoperative anemia management in obstetrics.

PURPOSE OF REVIEW: The purpose of this article is to provide an overview of currently recommended treatment approaches for anemia during pregnancy, with a special focus on iron deficiency and iron deficiency anemia (IDA). RECENT FINDINGS: As consistent patient blood management (PBM) guidelines in obstetrics are still lacking, recommendations regarding the timing of anemia screening and the treatment recommendations for iron deficiency and IDA during pregnancy are still controversial. Based on increasing evidence, early screening for anemia and iron deficiency should be recommended at the beginning of each pregnancy. To reduce maternal and fetal burden, any iron deficiency, even without anemia, should be treated as early as possible during pregnancy. While oral iron supplements administered every other day are the standard treatment in the first trimester, the use of intravenous iron supplements is increasingly suggested from the second trimester onwards. SUMMARY: The treatment of anemia, and more specifically iron deficiency anemia during pregnancy, holds many possibilities for improvement. The fact that the period of risk is known well in advance and thus there is a long optimization phase is per se an ideal prerequisite for the best possible therapy of treatable causes of anemia. Standardization of recommendations and guidelines for screening and treatment of IDA in obstetrics is required for the future. In any case, a multidisciplinary consent is the precondition for a successfully implementation of anemia management in obstetrics to establish an approved algorithm easily enabling detection and treatment of IDA during pregnancy.

Association of anaemia, co-morbidities and red blood cell transfusion according to age groups: multicentre sub-analysis of the German Patient Blood Management Network Registry.

BACKGROUND: Blood transfusions are common medical procedures and every age group requires detailed insights and treatment bundles. The aim of this study was to examine the association of anaemia, co-morbidities, complications, in-hospital mortality, and transfusion according to age groups to identify patient groups who are particularly at risk when undergoing surgery. METHODS: Data from 21 Hospitals of the Patient Blood Management Network Registry were analysed. Patients were divided into age subgroups. The incidence of preoperative anaemia, co-morbidities, surgical disciplines, hospital length of stay, complications, in-hospital mortality rate, and transfusions were analysed by descriptive and multivariate regression analysis. RESULTS: A total of 1 117 919 patients aged 18-108 years were included. With increasing age, the number of co-morbidities and incidence of preoperative anaemia increased. Complications, hospital length of stay, and in-hospital mortality increased with age and were higher in patients with preoperative anaemia. The mean number of transfused red blood cells (RBCs) peaked, whereas the transfusion rate increased continuously. Multivariate regression analysis showed that increasing age, co-morbidities, and preoperative anaemia were independent risk factors for complications, longer hospital length of stay, in-hospital mortality, and the need for RBC transfusion. CONCLUSION: Increasing age, co-morbidities, and preoperative anaemia are independent risk factors for complications, longer hospital length of stay, in-hospital mortality, and the need for RBC transfusion. Anaemia diagnosis and treatment should be established in all patients.

Preoperative anaemia and red blood cell transfusion in patients with aneurysmal subarachnoid and intracerebral haemorrhage - a multicentre subanalysis of the German PBM Network Registry.

PURPOSE: Anaemia is common in patients presenting with aneurysmal subarachnoid (aSAH) and intracerebral haemorrhage (ICH). In surgical patients, anaemia was identified as an idenpendent risk factor for postoperative mortality, prolonged hospital length of stay (LOS) and increased risk of red blood cell (RBC) transfusion. This multicentre cohort observation study describes the incidence and effects of preoperative anaemia in this critical patient collective for a 10-year period. METHODS: This multicentre observational study included adult in-hospital surgical patients diagnosed with aSAH or ICH of 21 German hospitals (discharged from 1 January 2010 to 30 September 2020). Descriptive, univariate and multivariate analyses were performed to investigate the incidence and association of preoperative anaemia with RBC transfusion, in-hospital mortality and postoperative complications in patients with aSAH and ICH. RESULTS: A total of n = 9081 patients were analysed (aSAH n = 5008; ICH n = 4073). Preoperative anaemia was present at 28.3% in aSAH and 40.9% in ICH. RBC transfusion rates were 29.9% in aSAH and 29.3% in ICH. Multivariate analysis revealed that preoperative anaemia is associated with a higher risk for RBC transfusion (OR = 3.25 in aSAH, OR = 4.16 in ICH, p < 0.001), for in-hospital mortality (OR = 1.48 in aSAH, OR = 1.53 in ICH, p < 0.001) and for several postoperative complications. CONCLUSIONS: Preoperative anaemia is associated with increased RBC transfusion rates, in-hospital mortality and postoperative complications in patients with aSAH and ICH. TRIAL REGISTRATION: ClinicalTrials.gov , NCT02147795, https://clinicaltrials.gov/ct2/show/NCT02147795.

Goal-directed intraoperative fluid therapy guided by stroke volume and its variation in high-risk surgical patients: a prospective randomized multicentre study.

Perioperative hemodynamic optimisation improves postoperative outcome for patients undergoing high-risk surgery (HRS). In this prospective randomized multicentre study we studied the effects of an individualized, goal-directed fluid management based on continuous stroke volume variation (SVV) and stroke volume (SV) monitoring on postoperative outcomes. 64 patients undergoing HRS were randomized either to a control group (CON, n = 32) or a goal-directed group (GDT, n = 32). In GDT, SVV and SV were continuously monitored (FloTrac/Vigileo) and patients were brought to and maintained on the plateau of the Frank-Starling curve (SVV <10 % and SV increase <10 % in response to fluid loading). Organ dysfunction was assessed using the SOFA score and resource utilization using the TISS score. Patients were followed up to 28 days for postoperative complications. Main outcome measures were the number of complications (infectious, cardiac, respiratory, renal, hematologic and abdominal post-operative complications), maximum SOFA score and cumulative TISS score during ICU stay, duration of mechanical ventilation, length of ICU stay, and time until fit for discharge. 12 patients had to be excluded from final analysis (6 in each group). During surgery, GDT received more colloids than CON (1,589 vs. 927 ml, P < 0.05) and SVV decreased in GDT (from 9.0 to 8.0 %, P < 0.05) but not in CON. The number of postoperative wound infections was lower in GDT (0 vs. 7, P < 0.01). Although not statistically significant, the proportion of patients with at least one complication (46 vs. 62 %), the number of postoperative complications per patient (0.65 vs. 1.40), the maximum sofa score (5.9 vs. 7.2), and the cumulative TISS score (69 vs. 83) tended to be lower. This multicentre study shows that fluid management based on a SVV and SV optimisation protocol is feasible and decreases postoperative wound infections. Our findings also suggest that a goal-directed strategy might decrease postoperative organ dysfunction.

Increased electrical nerve stimulation threshold of the sciatic nerve in patients with diabetic foot gangrene: a prospective parallel cohort study.

CONTEXT: Peripheral neuropathy may affect nerve conduction in patients with diabetes mellitus. OBJECTIVE: This study was designed to test the hypothesis that the electrical stimulation threshold for a motor response of the sciatic nerve is increased in patients suffering from diabetic foot gangrene compared to non-diabetic patients. DESIGN: Prospective non-randomised trial with two parallel groups. SETTING: Two university-affiliated hospitals. PARTICIPANTS: Patients scheduled for surgical treatment of diabetic foot gangrene (n = 30) and non-diabetic patients (n = 30) displaying no risk factors for neuropathy undergoing orthopaedic foot or ankle surgery. MAIN OUTCOME MEASURE: The minimum current intensity required to elicit a typical motor response (dorsiflexion or eversion of the foot) at a pulse width of 0.1 ms and a stimulation frequency of 1 Hz when the needle tip was positioned under ultrasound control directly adjacent to the peroneal component of the sciatic nerve. RESULTS: The non-diabetic patients were younger [64 (SD 12) vs. 74 (SD 7) years] and predominantly female (23 vs. 8). The geometric mean of the motor stimulation threshold was 0.26 [95% confidence interval (95% CI) 0.24 to 0.28] mA in non-diabetic and 1.9 (95% CI 1.6 to 2.2) mA in diabetic patients. The geometric mean of the electrical stimulation threshold was significantly (P < 0.001) increased by a factor of 7.2 (95% CI 6.1 to 8.4) in diabetic compared to non-diabetic patients. CONCLUSION: The electrical stimulation threshold for a motor response of the sciatic nerve is increased by a factor of 7.2 in patients with diabetic foot gangrene, which might hamper nerve identification.

Pulmonary artery vs. transpulmonary thermodilution for the assessment of cardiac output in mitral regurgitation: a prospective observational study.

CONTEXT: With increasing prevalence of mitral regurgitation, even noncardiac anaesthesiologists will be confronted by this disorder and will need to be familiar with the extended haemodynamic monitoring required. The assessment of cardiac output (CO) measured by transpulmonary thermodilution (COTP) has become an accepted alternative to the CO measured by thermodilution via pulmonary artery catheter (COPAC). However, the integrity of COTP in severe mitral regurgitation requires systematic evaluation. OBJECTIVE: This study was designed to test the hypothesis that transpulmonary thermodilution is compromised by severe mitral regurgitation. DESIGN: Prospective method comparison study. SETTING: Single university-affiliated hospital. PARTICIPANTS: Thirty patients with mitral regurgitation undergoing elective mitral valve repair. MAIN OUTCOME MEASURE: COTP and COPAC were determined in triplicate after induction of anaesthesia, and at the end of surgery after closure of the chest. The methods were compared using bias and precision statistics. RESULTS: Echocardiography revealed severe mitral regurgitation in most patients (n  =  27) after induction of anaesthesia. The least significant change in COTP (the minimum change in COTP required to detect a real change with a probability of 95%) was increased under the condition of mitral regurgitation (15.4  ±  10.2% after anaesthesia induction vs. 9.3  ±  5.9% after valve repair, P = 0.008), whereas it remained constant in COPAC (9.6  ±  5.4 vs. 8.5  ±  7.2%, P = 0.55). There was no significant bias between COTP and COPAC after anaesthesia induction [mean CO, 4.03 ±â€Š0.92 l  min; bias 0.12 l  min (95% confidence interval, CI, -0.073 to 0.311)], and after valve repair [mean CO 7.47  ±â€Š 1.44 l  min; bias 0.045 l  min (95% CI, -0.147 to 0.237)]. The percentage error was 28.4 and 13.6%, respectively. CONCLUSION: The results suggest that even severe mitral regurgitation has no significant impact on the accuracy of COTP. The precision of COTP was reduced under the condition of mitral regurgitation.

Anesthetic management in patients undergoing hyperthermic chemotherapy.

PURPOSE OF REVIEW: Cytoreductive surgery combined with hyperthermic intraperitoneal chemotherapy (HIPEC) has become an important therapeutic option for selected patients with peritoneal surface malignancies. This aggressive multimodality treatment is complex, not only regarding surgical technique, but also regarding anesthesia. The present review represents our experience in anesthetic care. RECENT FINDINGS: Improved prognosis compared with systemic chemotherapy alone has recently been demonstrated for cytoreductive surgery when combined with intraoperative intracavitary hyperthermic chemotherapy. Anesthetic management of HIPEC is further impacted by these developments. In addition to the ambitious, long-lasting surgery, HIPEC causes significant fluid, blood and protein losses, increased intra-abdominal pressure, systemic hyperthermia, and increased metabolic rate, leading to relevant pathophysiological alterations, and therefore represents a challenge for anesthetist and critical care physicians. SUMMARY: Anesthetic management importantly contributes to the containment of the perioperative complications of HIPEC. An appreciation of the technical aspects and physiologic disruptions associated with intra-abdominal HIPEC is critical to ensure effective anesthetic management. Although data on this specialized surgical procedure are scarce, some referral centers have accumulated extensive experience. This article reviews the current knowledge about the anesthesiological and intensive care management of patients undergoing HIPEC. It pinpoints strategies for perioperative monitoring as well as illustrates alterations in hemodynamic, hematopoetic, and fluid hemostasis.

High-dose tranexamic acid is related to increased risk of generalized seizures after aortic valve replacement.

OBJECTIVE: To investigate the incidence of postoperative generalized seizures in patients undergoing aortic valve replacement (AVR) under extracorporeal circulation, who received either high-dose tranexamic acid (TXA) or epsilon aminocaproic acid (EACA) as an antifibrinolytic agent. METHODS: This retrospective analysis comprised 682 consecutive patients undergoing AVR with or without simultaneous coronary artery bypass surgery. Patients operated on before March 2008 were treated intra-operatively with TXA (100 mg kg⁻¹; n = 341), patients operated on after March 2008 received EACA (50 mg kg⁻¹ loading dose, followed by 25 mg kg⁻¹ h⁻¹, and an additional 5 g in the extracorporeal circuit; n = 341). RESULTS: Clinically diagnosed generalized seizures were observed within the first 24h postoperatively, more frequently in patients receiving TXA compared with EACA (6.4% vs 0.6%, p < 0.001, difference = 5.8%, 95% confidence interval 3.1-8.5%). Besides the antifibrinolytic agent, three other variables differed significantly between patients with and without postoperative seizures: age (mean (SD), 77.0 (5.9) years vs 73.2 (9.0) years, p = 0.039), preoperative creatinine clearance (55.4 (16.5)ml min⁻¹ vs 72.6 (28.5)ml min⁻¹, p = 0.002), and administration of recombinant activated factor VIIa (3 out of 24 patients (12.5%) vs 8 out of 658 patients (1.2%), p = 0.005). Logistic regression analysis demonstrated a significant impact of the antifibrinolytic drug, creatinine clearance, and the application of recombinant activated factor VIIa on the occurrence of generalized seizures. CONCLUSIONS: Our results indicate that high-dose TXA is associated with an increased incidence of postoperative generalized seizures in patients undergoing AVR compared with EACA, especially when suffering from renal impairment. A possible association between recombinant activated factor VIIa and the occurrence of postoperative seizures needs further investigation.

Neuromonitoring in carotid surgery: are the results obtained in awake patients transferable to patients under sevoflurane/fentanyl anesthesia?

BACKGROUND: Diagnostic accuracy studies of neuromonitoring devices during carotid endarterectomy in awake patients are limited by the question of the transferability to anesthetized patients. This study was designed to compare the different neuromonitoring parameters in patients under regional and general anesthesia with stump pressure as the primary endpoint and the courses of cerebral blood flow velocity (Vmca) measured by transcranial Doppler sonography, regional cerebral oxygen saturation (rSO2) measured by near-infrared spectroscopy, and the amplitude of somatosensory evoked potentials (SEP) as the secondary endpoints. MATERIALS AND METHODS: Ninety-six patients undergoing carotid endarterectomy were randomized to regional (n=48) or sevoflurane/fentanyl anesthesia (n=48) group. Absolute and relative changes of Vmca and rSO2 and the SEP amplitude were recorded at baseline, during carotid artery clamping, and after declamping. Intergroup differences (ß) were calculated by generalized estimation equations and linear regression analysis. RESULTS: Mean arterial pressure (P<0.001) and heart rate (P<0.001) were significantly higher in the regional anesthesia group. SP did not differ between both the groups (ß=-1.6; P=0.71). Vmca (ß=9.2; P<0.01) and rSO2 (ß=4.1; P<0.01) values were higher in the awake patients. After adjustment for mean arterial pressure, the differences of Vmca remained consistent (ß=9.3; P<0.01) whereas these of rSO2 during clamping (ß=2.9; P=0.105) and during reperfusion (ß=2.7; P=0.095) disappeared. No significant differences were found for Vmca(%) (ß=-1.0; P=0.80), rSO2(%) (ß=-1.4; P=1.8) and SEP (ß=-2.6; P=0.29). CONCLUSION: Carotid artery clamping leads to similar results of stump pressure and similar relative changes of transcranial Doppler sonography, near-infrared spectroscopy, and SEP monitoring in patients under regional and sevoflurane/fentanyl anesthesia.

Circulatory arrest and deep hypothermia for the treatment of complex intracranial aneurysms--results from a single European center.

BACKGROUND: Vascular neurosurgery faces the controversial discussion about the need for deep hypothermia and circulatory arrest (dh/ca) for the treatment of complex cerebral aneurysms. In this retrospective analysis, we present our experience in the treatment of 26 giant and large cerebral aneurysms under profound hypothermia and circulatory arrest. METHODS: All patients were treated surgically under dh/ca. Seventeen patients had aneurysms of the anterior circulation, and nine patients had aneurysms of the posterior circulation. Thrombosis or calcification was found in ten patients. Eleven patients presented with subarachnoid hemorrhage. The seven patients with the longest circulation arrest time were analyzed in detail. RESULTS: Subarachnoid hemorrhage led to hospital admission in 42% (n = 11) of cases. The overall mortality was 11.5%, and the overall morbidity was 15%. Ten patients deteriorated transiently but fully recovered. The mean age, Glasgow Coma Score, Fisher, and Hunt and Hess Score correlated significantly with the long-term outcome. Circulation arrest time correlated significantly to the neurological outcome on discharge. All patients with prolonged circulation arrest times had wide aneurysmal necks, and four had adjacent vessels to the dome or the parent vessel included in the neck. We observed a significant increase of neurological deficits immediately postoperatively, but this neurological deterioration resolved over time. CONCLUSIONS: We observed neurological deterioration immediately postoperatively in 13 patients, but all patients fully recovered within 6 months except for four patients. A long cardiac arrest time reflected complex pathoanatomical conditions. We conclude that the clipping procedure under deep hypothermia and circulatory arrest remains a pivotal armament in complex vascular neurosurgery.

Accuracy of stroke volume variation compared with pleth variability index to predict fluid responsiveness in mechanically ventilated patients undergoing major surgery.

BACKGROUND AND OBJECTIVE: Accurate assessment of a patient's volume status is an important goal for an anaesthetist. However, most variables assessing fluid responsiveness are either invasive or technically challenging. This study was designed to compare the accuracy of arterial pressure-based stroke volume variation (SVV) and variations in the pulse oximeter plethysmographic waveform amplitude as evaluated with the noninvasive calculated pleth variability index (PVI) with central venous pressure to predict the response of stroke volume index (SVI) to volume replacement in patients undergoing major surgery. METHODS: We studied 20 patients scheduled for elective major abdominal surgery. After induction of anaesthesia, all haemodynamic variables were recorded immediately before (T1) and subsequent to volume replacement (T2) by infusion of 6% hydroxy-ethyl starch (HES) 130/0.4 (7 ml kg) at a rate of 1 ml kg min. RESULTS: The volume-induced increase in SVI was at least 15% in 15 patients (responders) and less than 15% in five patients (nonresponders). Baseline SVV correlated significantly with changes in SVI (DeltaSVI; r = 0.80; P < 0.001) as did baseline PVI (r = 0.61; P < 0.004), whereas baseline values of central venous pressure showed no correlation to DeltaSVI. There was no significant difference between the area under the receiver operating characteristic curve for SVV (0.993) and PVI (0.973). The best threshold values to predict fluid responsiveness were more than 11% for SVV and more than 9.5% for PVI. CONCLUSION: Although arterial pressure-derived SVV revealed the best correlation to volume-induced changes in SVI, the results of our study suggest that both variables, SVV and PVI, can serve as valid indicators of fluid responsiveness in mechanically ventilated patients undergoing major surgery.

Predicted and measured plasma propofol concentration and bispectral index during deep sedation in patients with impaired left ventricular function.

OBJECTIVE: To evaluate the ability of the Schnider pharmacokinetic model to predict plasma propofol concentration during target-controlled propofol infusion in patients with impaired left ventricular function and to investigate the predictive value of the bispectral index (BIS) to indicate deep sedation in this patient group. DESIGN: Prospective, observational study. PARTICIPANTS: Thirty-four patients (mean left ventricular ejection fraction 31% +/- 9%) undergoing the implantation of a cardioverter-defibrillator during deep sedation. INTERVENTIONS: None. MEASUREMENTS AND MAIN RESULTS: Predicted and measured propofol plasma concentrations and BIS were assessed during steady-state conditions with the propofol infusion rate constant for at least 20 minutes. The plasma propofol concentration was significantly underestimated by the pharmacokinetic model used (mean percentage prediction error 37% +/- 49%). The 50% probability of deep sedation was calculated at a predicted propofol concentration of 2.09 (95% confidence interval [CI], 2.04-2.14) mug/mL and at a measured propofol concentration of 2.70 (95% CI, 2.62-2.78) mug/mL. BIS values showed a marked variability among individuals during deep sedation (5th-95th percentiles: 25-81). CONCLUSIONS: The pharmacokinetic model used markedly underestimated propofol plasma levels in the patient group studied. The large variability among patients suggests that BIS monitoring is not suitable for indicating an exact endpoint corresponding to deep sedation.

[Cardiac output determination by thermodilution and arterial pulse waveform analysis in patients undergoing aortic valve replacement].

PURPOSE: To compare the accuracy of cardiac output (CO) measurement by arterial pulse waveform analysis (CO(PW)) to thermodilution assessments in patients with aortic stenosis, a high-risk patient group who may benefit from extended hemodynamic monitoring. METHODS: In 30 patients with aortic stenosis, CO was assessed in triplicate by thermodilution via pulmonary artery catheterization (CO(PAC)), and by arterial pulse waveform analysis (CO(PW)), before and after valve replacement. The techniques were compared by assessing the repeatability coefficient of each method and by calculating the percentage error, bias, and the limits of agreement between methods. RESULTS: The repeatability coefficients of CO(PAC) and CO(PW) were 0.89 L.min(-1) and 1.04 L.min(-1) respectively after induction of anesthesia, which corresponded to 24% of CO(PAC) and 26% of CO(PW), and increased to 33% of CO(PAC) and 32% of CO(PW) immediately after extracorporeal circulation. A systematic error between methods was not observed. The limits of agreement were bias +/- 1.42 L.min(-1) after anesthesia induction, corresponding to a 36% percentage error. The scattering of differences between methods increased markedly after termination of extracorporeal circulation (percentage error 56%). CONCLUSION: The repeatability of CO(PAC), as well as of CO(PW), is reduced in patients with aortic stenosis. The repeatability of both methods, as well as the agreement between methods, decreased markedly immediately after termination of cardiopulmonary bypass.

Evaluation of a new arterial pressure-based cardiac output device requiring no external calibration.

BACKGROUND: Several techniques have been discussed as alternatives to the intermittent bolus thermodilution cardiac output (COPAC) measurement by the pulmonary artery catheter (PAC). However, these techniques usually require a central venous line, an additional catheter, or a special calibration procedure. A new arterial pressure-based cardiac output (COAP) device (FloTractrade mark, Vigileotrade mark; Edwards Lifesciences, Irvine, CA, USA) only requires access to the radial or femoral artery using a standard arterial catheter and does not need an external calibration. We validated this technique in critically ill patients in the intensive care unit (ICU) using COPAC as the method of reference. METHODS: We studied 20 critically ill patients, aged 16 to 74 years (mean, 55.5 +/- 18.8 years), who required both arterial and pulmonary artery pressure monitoring. COPAC measurements were performed at least every 4 hours and calculated as the average of 3 measurements, while COAP values were taken immediately at the end of bolus determinations. Accuracy of measurements was assessed by calculating the bias and limits of agreement using the method described by Bland and Altman. RESULTS: A total of 164 coupled measurements were obtained. Absolute values of COPAC ranged from 2.80 to 10.80 l/min (mean 5.93 +/- 1.55 l/min). The bias and limits of agreement between COPAC and COAP for unequal numbers of replicates was 0.02 +/- 2.92 l/min. The percentage error between COPAC and COAP was 49.3%. The bias between percentage changes in COPAC (DeltaCOPAC) and percentage changes in COAP (DeltaCOAP) for consecutive measurements was -0.70% +/- 32.28%. COPAC and COAP showed a Pearson correlation coefficient of 0.58 (p < 0.01), while the correlation coefficient between DeltaCOPAC and DeltaCOAP was 0.46 (p < 0.01). CONCLUSION: Although the COAP algorithm shows a minimal bias with COPAC over a wide range of values in an inhomogeneous group of critically ill patients, the scattering of the data remains relative wide. Therefore, the used algorithm (V 1.03) failed to demonstrate an acceptable accuracy in comparison to the clinical standard of cardiac output determination.

Changes in pulse pressure variability during cardiac resynchronization therapy in mechanically ventilated patients.

INTRODUCTION: The respiratory variation in pulse pressure (PP) has been established as a dynamic variable of cardiac preload which indicates fluid responsiveness in mechanically ventilated patients. The impact of acute changes in cardiac performance on respiratory fluctuations in PP has not been evaluated until now. We used cardiac resynchronization therapy as a model to assess the acute effects of changes in left ventricular performance on respiratory PP variability without the need of pharmacological intervention. METHODS: In 19 patients undergoing the implantation of a biventricular pacing/defibrillator device under general anesthesia, dynamic blood pressure regulation was assessed during right ventricular and biventricular pacing in the frequency domain (power spectral analysis) and in the time domain (PP variation: difference between the maximal and minimal PP values, normalized by the mean value). RESULTS: PP increased slightly during biventricular pacing but without statistical significance (right ventricular pacing, 33 +/- 10 mm Hg; biventricular pacing, 35 +/- 11 mm Hg). Respiratory PP fluctuations increased significantly (logarithmically transformed PP variability -1.27 +/- 1.74 ln mm Hg2 versus -0.66 +/- 1.48 ln mm Hg2; p < 0.01); the geometric mean of respiratory PP variability increased 1.8-fold during cardiac resynchronization. PP variation, assessed in the time domain and expressed as a percentage, showed comparable changes, increasing from 5.3% (3.1%; 12.3%) during right ventricular pacing to 6.9% (4.7%; 16.4%) during biventricular pacing (median [25th percentile; 75th percentile]; p < 0.01). CONCLUSION: Changes in cardiac performance have a significant impact on respiratory hemodynamic fluctuations in ventilated patients. This influence should be taken into consideration when interpreting PP variation.

Effect of a miniaturized extracorporeal circulation (MECC System) on liver function.

OBJECTIVE: To evaluate the effect of a miniaturized extracorporeal circulation system (MECC System) compared to conventional extracorporeal circulation (ECC) regarding liver function in cardiac surgical patients. METHODS: Double indicator dilution measurements were achieved by bolus injection of indocyanine green (ICG) for assessment of cardiac index (CI) and plasma disappearance rate of ICG (PDRig). Measurements were simultaneously performed preoperatively after induction of anaesthesia (T1), following admission on the ICU (T2) and 6 h postoperatively (T3). RESULTS: CI and PDRig were markedly increased after cardiac surgery without significant differences between groups. The percentage increase in CI was significantly correlated to the percentage increase in PDRig in both groups. CONCLUSION: Liver function improved after cardiac surgery in both groups of patients, which may partly be explained by an increase in CI under mild inotrope support. Differences between the extracorporeal circuits with respect to PDRig appear to be minimal in a group of patients without pre-existing liver injury.

Implantation and testing of subretinal film electrodes in domestic pigs.

By definition, an electronic subretinal visual prosthesis requires the implantation of stimulation electrodes in the subretinal space of the eye. Polyimide film electrodes with flat contacts were implanted subretinally and used for electrical stimulation in acute experiments in anaesthetised domestic pigs. In two pigs, the film electrode was inserted through a sclerostomy into the vitreous cavity and, subsequently, via a retinotomy into the subretinal space around the posterior pole (ab interno approach). In three other pigs the sclera and pigment epithelium were opened for combined ab interno and transscleral positioning of the subretinal electrode. In all cases, perfluorocarbon liquid (PFCL) was used to establish a close contact between the film electrode and the outer retina. After cranial preparations of three pigs for epidural recording of visual cortex responses, retinal stimulation was performed in one pig with a film electrode implanted ab interno and in two pigs with film electrodes implanted by the ab interno and transscleral procedure. The five subretinal implantations were carried out successfully and each polyimide film electrode tip was positioned beneath the outer retina of the posterior pole. The retina was attached to the stimulation electrode in all cases. Epidural cortical responses to light and electrical stimulation were recorded in three experiments. Initial cortical responses to Ganzfeld light and to electrical stimuli occurred about 40 and 20 ms, respectively, after stimulation onset. The stimulation threshold was approximately 100 microA and, like the cortical response amplitudes, depended both on the correspondence between retinal stimulation and cortical recording sites and on the number of stimulation electrodes used simultaneously. Our results in a domestic pig model demonstrate that polyimide film electrodes can be implanted subretinally and tested by recording cortical responses to electrical stimulation. These findings suggest that the domestic pig could be an appropriate animal model for basic testing of subretinal implants.

Continuously assessed right ventricular end-diastolic volume as a marker of cardiac preload and fluid responsiveness in mechanically ventilated cardiac surgical patients.

INTRODUCTION: Assessing cardiac preload and fluid responsiveness accurately is important when attempting to avoid unnecessary volume replacement in the critically ill patient, which is associated with increased morbidity and mortality. The present clinical trial was designed to compare the reliability of continuous right ventricular end-diastolic volume (CEDV) index assessment based on rapid response thermistor technique, cardiac filling pressures (central venous pressure [CVP] and pulmonary capillary wedge pressure [PCWP]), and transesophageal echocardiographically derived evaluation of left ventricular end-diastolic area (LVEDA) index in predicting the hemodynamic response to volume replacement. METHODS: We studied 21 patients undergoing elective coronary artery bypass grafting. After induction of anesthesia, hemodynamic parameters were measured simultaneously before (T1) and 12 min after volume replacement (T2) by infusion of 6% hydroxyethyl starch 200/0.5 (7 ml/kg) at a rate of 1 ml/kg per min. RESULTS: The volume-induced increase in thermodilution-derived stroke volume index (SVITD) was 10% or greater in 19 patients and under 10% in two. There was a significant correlation between changes in CEDV index and changes in SVITD (r2 = 0.55; P < 0.01), but there were no significant correlations between changes in CVP, PCWP and LVEDA index, and changes in SVITD. The only variable apparently indicating fluid responsiveness was LVEDA index, the baseline value of which was weakly correlated with percentage change in SVITD (r2 = 0.38; P < 0.01). CONCLUSION: An increased cardiac preload is more reliably reflected by CEDV index than by CVP, PCWP, or LVEDA index in this setting of preoperative cardiac surgery, but CEDV index did not reflect fluid responsiveness. The response of SVITD following fluid administration was better predicted by LVEDA index than by CEDV index, CVP, or PCWP.

Transscleral implantation and neurophysiological testing of subretinal polyimide film electrodes in the domestic pig in visual prosthesis development.

Loss of photoreceptor function is responsible for a variety of blinding diseases, including retinitis pigmentosa. Advances in microtechnology have led to the development of electronic visual prostheses which are currently under investigation for the treatment of human blindness. The design of a subretinal prosthesis requires that the stimulation device should be implantable in the subretinal space of the eye. Current limitations in eye surgery have to be overcome to demonstrate the feasibility of this approach and to determine basic stimulation parameters. Therefore, polyimide film-bound electrodes were implanted in the subretinal space in anaesthetized domestic pigs as a prelude to electrical stimulation in acute experiments. Eight eyes underwent surgery to demonstrate the transscleral implantability of the device. Four of the eight eyes were stimulated electrically. In these four animals the cranium was prepared for epidural recording of evoked visual cortex responses, and stimulation was performed with sequences of current impulses. All eight subretinal implantation procedures were carried out successfully with polyimide film electrodes and each electrode was implanted beneath the outer retina of the posterior pole of the operated eyes. Four eyes were used for neurophysiological testing, involving recordings of epidural cortical responses to light and electrical stimulation. A light stimulus response, which occurred 40 ms after stimulation, proved the integrity of the operated eye. The electrical stimuli occurred about 20 ms after the onset of stimulation. The stimulation threshold was approximately 100 microA. Both the threshold and the cortical responses depended on the correspondence between retinal stimulation and cortical recording sites and on the number of stimulation electrodes used simultaneously. The subretinal implantation of complex stimulation devices using the transscleral procedure with consecutive subretinal stimulation is feasible in acute experiments in an animal model approximating to the situation in humans. The domestic pig is an appropriate animal model for basic testing of subretinal implants. Animal experiments with chronically implanted devices and long-term stimulation are advisable to prepare the field for successful human experiments.