Feasibility of closed-loop co-administration of propofol and remifentanil guided by the bispectral index in obese patients: a prospective cohort comparison.

BACKGROUND: We used an automated bispectral index (BIS)-guided dual-loop controller to determine propofol and remifentanil requirements during general anaesthesia in obese and lean surgical patients. METHODS: Obese patients, BMI>35 kg m(-2), and lean patients (<25 kg m(-2)) having laparoscopic procedures were prospectively evaluated in this multicentre single-blind study. The automated controller targeted BIS between 40 and 60 by adjusting propofol and remifentanil administration. Propofol and remifentanil consumptions were calculated using both total body weight (TBW) and ideal body weight (IBW). Results are expressed as medians (inter-quartile range). RESULTS: Thirty obese [BMI=43 (40-49) kg m(-2)] and 29 lean [BMI=23 (21-25) kg m(-2)] patients completed the study. BIS was between 40 and 60 during 84 (69-91)% vs 85 (78-92)% of the anaesthetic time, P=0.46. The amount of propofol given during induction [1.2 (1.1-1.6) vs 1.3 (1.0-1.7) mg kg(-1), P=0.47] and maintenance [5.2 (4.1-6) vs 5.3 (4.7-6.4) mg kg(-1) h(-1), P=0.39] calculated using TBW was similar between the two groups. The dual-loop controller delivered half as much remifentanil to the obese patients during induction [1.0 (0.8-1.6) vs 2.2 (1.5-2.7) µg kg(-1), P<0.001] and maintenance [0.12 (0.07-0.16) vs 0.25 (0.17-0.29) µg kg(-1) min(-1), P<0.001] calculated using TBW. But when remifentanil consumption was calculated using IBW, the amounts were similar during induction at 2.2 (1.6-3.5) vs 2.0 (1.6-3.0) µg kg(-1) IBW, P=0.48, and during maintenance at 0.26 (0.16-0.34) vs 0.27 (0.18-0.33 ) µg kg(-1) min(-1), P=0.50. CONCLUSIONS: The amount of propofol-remifentanil administered by the controller is consistent with current knowledge, propofol is best dosed using TBW whereas remifentanil is best dosed using IBW. CLINICAL TRIAL REGISTRATION: NCT00779844.

Pressure-controlled ventilation improves oxygenation during laparoscopic obesity surgery compared with volume-controlled ventilation.

BACKGROUND: We compared pressure and volume-controlled ventilation (PCV and VCV) in morbidly obese patients undergoing laparoscopic gastric banding surgery. METHODS: Thirty-six patients, BMI>35 kg m(-2), no major obstructive or restrictive respiratory disorder, and Pa(CO(2))<6.0 kPa, were randomized to receive either VCV or PCV during the surgery. Ventilation settings followed two distinct algorithms aiming to maintain end-tidal CO(2) (E'(CO(2))) between 4.40 and 4.66 kPa and plateau pressure (P(plateau)) as low as possible. Primary outcome variable was peroperative P(plateau). Secondary outcomes were Pa(O(2)) (Fi(O(2)) at 0.6 in each group) and Pa(CO(2)) during surgery and 2 h after extubation. Pressure, flow, and volume time curves were recorded. RESULTS: There were no significant differences in patient characteristics and co-morbidity in the two groups. Mean pH, Pa(O(2)), Sa(O(2)), and the Pa(O(2))/Fi(O(2)) ratio were higher in the PCV group, whereas Pa(CO(2)) and the E'(CO(2))-Pa(CO(2)) gradient were lower (all P<0.05). Ventilation variables, including plateau and mean airway pressures, anaesthesia-related variables, and postoperative cardiovascular variables, blood gases, and morphine requirements after the operation were similar. CONCLUSIONS: The changes in oxygenation can only be explained by an improvement in the lungs ventilation/perfusion ratio. The decelerating inspiratory flow used in PCV generates higher instantaneous flow peaks and may allow a better alveolar recruitment. PCV improves oxygenation without any side-effects.

[European normative recommendations for medical gas pipeline systems]. / Normalisation européenne et systèmes de distribution de gaz médicaux.

Several recent decisions have been made in order to increase the security of medical gases delivery in French hospitals. These different changes affect: 1) the hospital itself with the creation of working groups in charge of both monitoring and maintenance of gases networks; 2) the pharmaceutical regulation with promotion of several gases to the status of drugs or need of CE marking for the whole gas network. European rules onset required to give up French former norms (NF) to the profit of "NF EN" rules. Nevertheless, the new norm NF EN 737-3 which concerns medical gases distribution systems does not affect principal clauses of the previous NF S 90-155. It introduces new elements allowing to deploy two types of medical gases networks: the double pressure level used in France and the single pressure level used in the rest of Europe. This new norm, which attempts to harmonize alarm control systems in both types of networks, suffers from important limitations describing the double pressure level systems. Lastly, the final checking proposed by this new norm is very different from the previous one, and is likely to be problematic for the final users within the hospital.

Adult overwhelming meningococcal purpura. A study of 35 cases, 1977-1989.

The study objective was to describe the clinical, biologic, and hemodynamic features of adult overwhelming meningococcal purpura and to examine the prognostic factors by multivariate analysis at the time of admission to the intensive care unit. Thirty-five patients (greater than or equal to 13 years of age) with meningococcal infection, circulatory shock, and generalized purpuric lesions of abrupt onset were recorded in eight intensive care units from 1977 to 1989. The patients were young (mean age, 26.6 years; range, 13 to 68 years) and had been previously healthy. The female-to-male ratio was 3:1. Mortality was 54.3%, with most deaths occurring within the first 48 hours, usually secondary to irreversible shock with multiple organ failure. Ischemic complications (eight cases), prolonged heart failure (seven cases), and secondary septicemia (five cases) were the chief complications among survivors. Initial hemodynamic study after volume loading showed low stroke volume index (mean +/- SD, 29.4 +/- 13 mL/m2) and tachycardia (mean +/- SD, 138 +/- 16 beats per minute), a profile suggesting a greater myocardial depression than usually observed in gram-negative bacillary septic shock. Univariate prognostic analysis showed that four variables at the time of admission were associated with fatal outcome: a plasma fibrinogen level of 1.5 g/L or less, a factor V concentration of 0.20 or less, a platelet count lower than 80 x 10(9)/L, and a cerebrospinal fluid leukocyte count of 20 x 10(6)/L or less. Stepwise regression analysis showed that low fibrinogen level (less than or equal to 1.5 g/L) was the sole adverse prognostic variable (odds ratio = 2, 95% confidence interval, 1.5 to 2.7). Adult overwhelming meningococcal purpura is still associated with high mortality and morbidity. Low fibrinogen level at time of admission may permit early recognition of the most severely ill patients.

Extracorporeal life support (ECLS) for refractory cardiac arrest after drowning: an 11-year experience.

AIM: Neuroprotective effects of hypothermia may explain surprisingly high survival rates reported after drowning in cold water despite prolonged submersion. We described a cohort of refractory hypothermic cardiac arrests (CA) due to drowning treated by extracorporeal life support (ECLS) and aimed to identify criteria associated with 24-h survival. METHODS: Eleven-year period (2002-2012) retrospective study in the surgical intensive care unit (ICU) of a tertiary hospital (European Hospital Georges Pompidou, Paris, France). All consecutive hypothermic patients admitted for refractory CA after drowning in the Seine River were included. Patients with core temperature below 30°C and submersion duration of less than 1h were potentially eligible for ECLS resuscitation. RESULTS: Forty-three patients were admitted directly to the ICU during the study period. ECLS was initiated in 20 patients (47%). Among these 20 patients, only four (9%) survived more than 24h. A first hospital core temperature ≤26°C and a potassium serum level between 4.2 and 6mM at hospital admission have a sensitivity of 100% [95%CI: 28-100%] and a specificity of 100% [95%CI: 71-100%] to discriminate patients who survived more than 24h. Overall survival at ICU discharge and at 6-months was 5% [95%CI: 1-16%] (two patients). CONCLUSIONS: Despite patient hypothermia and aggressive resuscitation with ECLS, the observed survival rate is low in the present cohort. Like existing algorithms for ECLS management in avalanche victims, we recommend to use first core temperature and potassium serum level to indicate ECLS for refractory CA due to drowning.

Incidence and predictors of major hemorrhagic complications from thrombolytic therapy in patients with massive pulmonary embolism.

PURPOSE: The risk factors for bleeding in patients receiving recombinant tissue-type plasminogen activator for massive pulmonary embolism are not known. PATIENTS AND METHODS: The hospital records of 132 consecutive patients who received recombinant tissue-type plasminogen activator for massive pulmonary embolism were retrospectively reviewed. Bleeding was estimated by using the bleeding severity index, a method previously validated in patients receiving anticoagulants. Multivariate stepwise logistic regression was used to identify independent risk factors for bleeding. Four other definitions of bleeding in large pulmonary embolism thrombolytic trials were also used, and the agreement among these criteria was assessed. RESULTS: According to the bleeding severity index, 33 patients (25%) had one or more major bleeding complications. Hemorrhage at the venous puncture site for angiography was the most frequent complication (15 patients, 11%). Major bleeding at the catheterization site was more common at the femoral site (14 of 63 patients = 22%) than at the brachial site (1 of 63 patients = 2%; P = 0.0004). The use of the five different bleeding definitions resulted in a variation in the major bleeding rate from 3% to 43%. The kappa coefficient varied from 0.07 to 0.84, indicating poor agreement between most of the classifications. CONCLUSION: The use of the femoral vein for pulmonary angiography was the only variable significantly associated with major bleeding. Most of the differences observed in the pulmonary embolism thrombolytic trials are likely related to the differences in the definition of bleeding rather than to the thrombolytic regimen.

Elastic energy as an index of right ventricular filling.

BACKGROUND: Right ventricle (RV) preload assessment remains controversial because the complexity of RV geometry is an obstacle to wall stress modeling. We developed a method to evaluate end-diastolic RV elastic energy (EL), a variable that integrates all the stretching effects of venous return and that can be easily estimated at the bedside from the area under the diastolic RV pressure-volume curve. The purpose of this study was to compare the clinical utility of EL and of the two conventional variables used to assess RV filling, ie, right atrial pressure (Pra) and RV end-diastolic volume (EDV). METHOD: We studied 26 postoperative patients who required a rapid fluid challenge. Energetics were evaluated by constructing the RV pressure-volume loop at the bedside using right heart catheterization with RV ejection fraction (EF) derivation. Correlations between RV filling and RV performance (ejection and mechanical efficiency) were studied. RV filling indexes were Pra, EDV, and EL. Indexes of RV ejection were stroke volume (SV), RV stroke work (RVSW), mechanical energy expenditure during ejection (EM), and total energy expenditure of contraction (ET). Indexes of RV mechanical efficiency were EF and the EM/ET ratio. RESULTS: Three important results were obtained. First, among RV ejection indexes, those that correlated best with RV filling indexes were EM and ET. Second, we found significant linear relationships between improved RV filling, as assessed by changes in EDV and EL, and improved RV ejection, as assessed by changes in SV, RVSW, EM, or ET. Third, changes in EDV and EL also predicted improved mechanical efficiency, as assessed by changes in EF and EM/ET. In, all situations, changes in EL yielded the strongest correlations. CONCLUSIONS: Derivation of EL is simple and appears to be the best clinical means of assessing Starling's law of the heart for the RV.

Ten-year experience with surgical treatment of partial atrioventricular septal defect: risk factors in the early postoperative period.

Partial atrioventricular septal defects are electively repaired with good results. However, recent reports suggest that such repair is potentially a high-risk surgical procedure. Our aim was to determine the risk factors of adverse outcome early after surgical treatment of atrioventricular septal defects in our hospital. A retrospective study was done in 100 consecutive patients from 2 months to 50.6 years old (median 3.6 years) who underwent surgical correction between January 1984 and December 1993. An intermediate form of the lesion was noted in 31% of cases. Congestive heart failure occurred in 50% of cases. Preoperative left atrioventricular valve incompetence (moderate to severe) was present in 63% of patients. Severe abnormalities of left subvalvular apparatus were noted in 28% of patients. The cleft of the left atrioventricular valve was closed in 76% of cases. The study was done to determine risk factors associated with hospital mortality (13%), postoperative residual left atrioventricular valve incompetence (23%), and early reoperation (14%) within the first 30 postoperative days. Univariate analysis showed that age at the date of operation and cleft closure were not related to an early adverse outcome. A stepwise logistic regression with variables selected by univariate analysis identified infections and severe abnormalities of left subvalvular apparatus as predictive factors of early death (odds ratio, 28.07 and 6.18, respectively), preoperative left atrioventricular valve regurgitation as a predictive factor of residual postoperative left atrioventricular valve regurgitation (odds ratio, 5.34), and severe abnormalities of left subvalvular apparatus as a predictive factor of early reoperation (odds ratio, 5.27). These results emphasize the importance of the severity of the morphologic features of the left subvalvular apparatus, the occurrence of early postoperative infections, and the presence of residual left atrioventricular valve regurgitation as risk factors in the early period after surgical correction of partial atrioventricular septal defects.

Inhaled nitric oxide as a therapy for pulmonary hypertension after operations for congenital heart defects.

Seventeen infants were treated with inhaled nitric oxide for critical pulmonary artery hypertension after operations for congenital heart defects. In all 17 patients conventional medical therapy consisting of hyperventilation, deep sedation/analgesia, and correction of metabolic acidosis had failed. All children were monitored with a transthoracic pulmonary artery catheter inserted at operation. Pulmonary artery hypertension was defined as an acute rise in pulmonary pressure associated with a decrease in oxygen arterial or venous saturation. After failure of conventional medical therapy, 20 ppm of inhaled nitric oxide was administered to the patient. In all patients the pulmonary pressures decreased (mean pulmonary arterial pressure decreased by -34% +/- 21%) without significant change in systemic arterial pressure, whereas the oxygen arterial saturation and oxygen venous saturation increased by 9.7% +/- 12% and 37% +/- 28%, respectively. Fifteen children were discharged from the intensive care unit at 10 +/- 6 days (range 3 to 26 days) and two died. This study demonstrates that inhaled nitric oxide exerts a selective pulmonary vasodilation without decreasing systemic arterial pressure in children with congenital heart disease. The increased values of mixed venous oxygen saturation and urinary output suggest that this selective lowering of pulmonary vascular resistance improved the overall hemodynamics. The potential toxic effects of nitric oxide and nitrogen dioxide necessitate careful consideration of the risks and benefits of inhaled nitric oxide therapy.

Effects of calcium concentration, lactobionate content, and sodium/ potassium ratio of preservation solutions on resting left ventricular pressure and postreperfusion function of rabbit heterotopic heart transplants.

BACKGROUND: We tested the hypothesis that the University of Wisconsin solution has a ionic composition (i.e., intracellular, calcium-free, lactobionate-enriched) that may be beneficial for cold heart graft preservation independently from any additives. METHODS: St. Thomas' Hospital and University of Wisconsin solutions were compared with the following: (1) C solution, a simplified University of Wisconsin-like solution (i.e., intracellular, calcium-free, lactobionate-enriched); (2) A solution, an St. Thomas' Hospital-like solution (extracellular, calcium [Ca2+] = 1.2 mmol/L) in which chloride was replaced by lactobionate; (3) B solution, an intracellular, lactobionate-enriched, calcium-containing solution ([Ca2+] = 1.2 mmol/L). Rabbit hearts were transplanted heterotopically in the abdomen of recipient animals either immediately or after 6 hours of storage. Hemodynamic parameters were recorded 60 minutes after unclamping. RESULTS: After a 6-hour storage, University of Wisconsin and C solutions provided better preservation than B and St. Thomas' Hospital solutions: diastolic pressures were lower; developed pressure and rate of pressure rise were higher. C solution was superior to University of Wisconsin solution only for rate of pressure rise. A solution was intermediary. A significant alteration of resting pressure and hemodynamic parameters was generally observed during the 6-hour storage. Nonsignificant changes of developed pressure and rate of pressure rise were only observed in C and B solutions: This is explained by systolic alteration after immediate reimplantation for the B group and good preservation for the C group. Resting pressure was unchanged over a 6-hour storage only for the C group, but this measure was not determined for University of Wisconsin. A correlation exists for various left ventricular volumes between resting pressure and postreperfusion hemodynamic data. Replacement of chloride by lactobionate (A versus St. Thomas' Hospital) may have improved resting and diastolic pressures by other mechanisms than limitation of net water gain during storage.

High-volume haemofiltration in human septic shock.

OBJECTIVE: To evaluate whether high volume haemofiltration improves haemodynamics and affects serum cytokine and complement concentrations in human septic shock. DESIGN AND SETTING: Randomized cross-over clinical trial in a tertiary intensive care unit. PATIENTS: Eleven patients with septic shock and multi-organ failure. INTERVENTIONS: Patients were assigned to either 8 h of high-volume haemofiltration (HVHF; 6 l/h) or 8 h of standard continuous veno-venous haemofiltration (CVVH; 1 l/h) in random order. MEASUREMENTS AND MAIN RESULTS: We measured changes in haemodynamic variables, dose of norepinephrine required to maintain a mean arterial pressure greater than 70 mmHg and plasma concentrations of complement anaphylatoxins and several cytokines. An 8-h period of HVHF was associated with a greater reduction in norepinephrine requirements than a similar period of CVVH (median reduction: 10.5 vs. 1.0 microg/min; p = 0.01; median percentage reduction: 68 vs. 7%; p = 0.02). Both therapies were associated with a temporary reduction (p < 0.01) in the plasma concentration of C3a, C5a, and interleukin 10 within 2 h of initiation. HVHF was associated with a greater reduction in the area under the curve for C3a and C5a (p < 0.01). The concentration of the measured soluble mediators in the ultrafiltrate was negligible. CONCLUSIONS: HVHF decreases vasopressor requirements in human septic shock and affects anaphylatoxin levels differently than standard CVVH.

Hemofiltration during cardiopulmonary bypass.

Several factors combine to facilitate the evolution towards heart and multi-organ failure following cardiac surgery. Some of these factors are related to pure cardiac aspects, for example, the existence of a preoperative heart disease, the use of aortic cross clamping or performance of cardiotomy. Cardiopulmonary bypass (CPB) also plays an important role in the occurrence of postoperative organ dysfunctions by two principal means. It induces a profound hemodilution, which impairs oxygen transport through tissues. This phenomenon becomes obvious in the postoperative period by the existence of increased transpulmonary O2 gradients, extravascular lung water volume and subsequent impairments of O2 transport. (2) Cardiopulmonary bypass is deleterious by triggering an important inflammatory reaction. This reaction is largely related to the ratio of the circuit area to the patient's body surface area and is therefore maximal in children. It has been widely demonstrated that the very early paths of this reaction imply several humoral factors including kinins, coagulation factor XII and complement fragments. The activation of these factors is self-amplified and triggers both expression and release of numerous mediators by endothelial cells and leukocytes. Finally, these mediators are responsible for the well described "post-bypass syndrome," which is, from a clinical viewpoint, very close to hyperkinetic septic shock. Several methods have been proposed to reduce the deleterious effects of both cardiac surgery and CPB. The older one is hypothermia that considerably reduces the triggering of the inflammatory mediator network. Heparin-coated circuits may also reduce this reaction to some extent. Hemofiltration has been introduced in the 1990s in CPB management. Because of its very high tolerance in patients with compromised circulatory status this technique was already used in the postoperative period to treat patients with acute renal failure. Initially hemofiltration was intended to correct the accumulation of extravascular water during or immediately following the surgical procedure. Nevertheless, several of its side-effects appeared to be useful, such as the reduction of postoperative blood loss and immediate improvement in hemodynamics. Several studies attempted to point out the mechanism of action of hemofiltration and although removal of inflammatory mediator occurs, there is currently no proof that this removal is the actual mechanism by which this technique acts.

Value of elementary, combined, and modeled hemodynamic variables.

PURPOSE: It has been well recognized that the usefulness of the clinical examination and simple hemodynamic variables in the critically ill is limited. Modelization for hemodynamic analysis may improve the diagnostic performance by a systematic and multivariate analysis. This requires a rigorous formalization that may otherwise expand the usefulness of hemodynamic data, both as predictors and as therapeutic targets. Our study was designed to test the value of a model for assessing the pathophysiology of circulatory disorders and for establishing the diagnosis. METHODS: We tested all available variables using survival as the end point. A population of 223 patients (652 measurements) with compromised circulatory status was studied. We evaluated traditional variables: (1) morphological and physical data, (2) elementary right heart catheterization data, and (3) usually calculated variables, versus (4) new modeled variables. These new modeled variables were derived from a previously validated computer program for hemodynamic evaluation. They expressed differences between observed hemodynamic performance and estimated needs. RESULTS: Among traditional variables, major prognostic factors were: (1) in all patients, lactate level elevation, physical signs of hypoperfusion, and a decreased systemic arterial pressure; (2) in septic patients, a high PaO2/SaO2 ratio; (3) in nonseptic patients, low left ventricle work indices. In all cases, modeled hemodynamic variables assessing performance-needs adequacy enhanced the prognostic value of hemodynamic monitoring. CONCLUSIONS: Compared with traditional variables, modeled variables were found of greater interest to quantify pathophysiology of shock. These results enabled us to validate the initial step of the hemodynamic reasonning formalization and to develop "new" diagnostic criteria that more closely fit the interrelationship between pathophysiology, diagnosis, and prognosis.

[Enoximone and pediatric heart surgery]. / Enoximone et chirurgie cardiaque pédiatrique.

The double mode of action of enoximone, inotropic and vasodilator, makes it a valuable drug in adult cardiac surgery. There have been no reports of its use in paediatric cardiac surgery. We studied its effects in 15 children with a right heart malformation, 5 with cardiac transplants and 5 with various malformations of different complexity. Enoximone was administered as an IV bolus of 1 mg/kg over 10 minutes, relayed by a continuous infusion of 7.5 gamma/kg/mn. This drug was used alone in 15 patients and in association with dobutamine or dopamine in the others. Enoximone was associated with an improved haemodynamic status after repair of right heart malformations related to better left ventricular contractility, a moderate but statistically significant elevation of mean blood pressure without tachycardia, and stable right heart filling pressures. Improved systemic perfusion was also observed in children awaiting cardiac transplantation. This treatment provided a bridge to cardiac transplantation which was attained in good condition, given the difficulties of using mechanical circulatory assistance in children and the scarcity of donors. When associated with other pulmonary vasodilators, enoximone was effective in the treatment of right heart failure with pulmonary hypertension. When used alone or in association with catecholamines, enoximone is a treatment of choice in per and postoperative paediatric intensive care, especially as the synergist effect obtained enables a reduction in the quantity of classical inotropic agents used, thereby contributing to an attenuation of the phenomenon of exhaustion observed with catecholergic drugs.

[Continuous monitoring of mixed venous blood oxygen saturation]. / Monitorage continu de la saturation du sang veineux mêlé en oxygène.

Mixed venous oxygen saturation (SvO2), measured on pulmonary artery blood, is a convenient indicator of matching between O2 transport (TaO2) and O2 body consumption (VO2). The measurement technique is based on the haemoglobin reflection spectrophotometry principle using two or three wave lengths. The Fick principle points out that SvO2 depends on five parameters: SvO2 = SaO2 - (VO2/CI x Hb x PO) where SaO2, CI and PO respectively represent arterial O2 saturation, cardiac index and O2 affinity. SvO2 does not always reflect tissue O2 tension: when considering a given value of SvO2, PvO2 will depend upon the position of the oxyhaemoglobin dissociation curve. It is impossible to establish in the absolute a "normal" value of SvO2. However, in most clinical circumstances, an SvO2 ranging from 60 to 80% attests that O2 tissue delivery is appropriate. Under certain conditions a continuous monitoring of SvO2 allows to assess another index such as ventilation-perfusion index or the O2 tissue extraction index. Usually SvO2 variations are more informative than the absolute SvO2 value. However, their interpretation should be cautious. First and foremost, the ability of each of the four main SvO2 determinants to influence the SvO2 is unequal as the numerical ranges of variation of these determinants are very different. Moreover, the attribution of a variation of SvO2 to one of its determinants implies that each of them is independent from the others, a feature which is very rarely seen in clinical practice. Finally as the mathematical relationship between SvO2 and its determinants is linear (SaO2 and VO2), or hyperbolic (CI and Hb), the weight of SaO2 or VO2 is independent of their absolute value, whereas CI or Hb weights will depend on their value. The limits of SvO2 monitoring are linked first to the occurrence of an anaerobic metabolism state when TaO2 becomes too low; SvO2 then just provides informations on the aerobic part of the metabolism. Moreover, SvO2 is just a global indicator for tissue O2 oxygenation status which does not give any indication about regional flow distribution. Therefore, SvO2 enables systemic imbalance supervision only. Finally, the existence of a right-to-left shunt will modify the SvO2 values through various mechanisms. However the SvO2 measured, in the pulmonary artery, remains reliable, whereas the presence of a left-to-right shunt will highly alter SvO2 basal value, only its time course remaining significant. SvO2 monitoring, element of diagnosis and monitoring, as well as a warning signal, has a priori specific indications poorly assessed, so far. (ABSTRACT TRUNCATED AT 400 WORDS)

[Continuous hemofiltration: an extrarenal filtration method used in intensive care]. / L'hémofiltration continue: méthode d'épuration extrarénale en réanimation.

Continuous haemofiltration (CHF) mimics physiological glomerular filtration. Blood flows through a haemofilter, which is permeable to water and to all those substances not bound to plasma proteins, of up to about 6,000 d molecular weight. Ten to twenty liters of ultrafiltrate (UF) can be filtered daily. Solute concentration in this UF is very similar to that in plasma water. Because of the large volumes involved, the UF must be replaced continuously with an electrolyte solution. Electrolyte and acid-base disturbances can thus be easily and rapidly corrected. There are different techniques of CHF. Continuous arteriovenous haemofiltration (CAVH) avoids the use of an external blood pump, as the patient's own arterial pressure is used to drive the blood through the filter via a large-bore arterial catheter. On the other hand, continuous venovenous haemofiltration (CVVH) requires the use of a blood pump with a pressure alarm and an air bubble detector. Supplementary diffusive transport [CAVH(D),CVVH(D)] can improve the clearance of low molecular weight toxins, such as urea. In these techniques, there is a continuous flow of dialysate in the UF compartment of the haemofilter. One of the major problems with CHF is the anticoagulation of patients who are at risk of developing haemorrhagic complications. Unfractionated heparin is used most often, but other drugs have been used: low molecular weight heparin, prostacyclin, nafamostat, or sodium citrate. The neutralization of heparin has also been suggested. Because the fluid balance can be easily managed by CHF, patients in acute renal failure can be given standard intravenous feeding. Many small endogenous molecules, such as gastrin, are probably removed by CHF. However, most drugs have a molecular weight less than 6,000 d, and are not totally protein-bound. They are therefore likely to be ultrafiltered, and so, become inefficient. As a result, the drugs used should be adapted to the haemofilter, and vice versa. More than any extracorporeal circulation, CHF increases the incidence of bacterial blood contamination, because of its continuous use. Routine blood cultures should be carried out. Moreover, blood is cooled during its passage in the extracorporeal circuit, leading to hypothermia. There are some devices which prevent this. Renal function can be completely replaced with the production of 12 to 15 l UF a day. CHF must be started early on in the course of the renal failure. When the concentration of blood urea is greater than 40 mmol.l-1 diffuse transport must also be used.(ABSTRACT TRUNCATED AT 400 WORDS)

[Comparison of two measurement methods: the Bland and Altman assessment]. / Comparaison de deux méthodes de mesure d'une même grandeur: méthode de Bland et Altman.

Bland-Altman analysis for comparison of two methods of clinical measurement is frequently used in scientific publications. This article is more appropriate than the conventional linear regression analysis. This paper gives an overview of the principles for the use of Bland-Altman analysis as well as the specific terminology attached to it. The Bland-Altman comparison analysis is mainly a tool for clinical interpretation. The bias and the agreement limits provide the variation of the values of the technique compared to the other. The difference between the two methods of measurement is plotted against the average obtained with each of the two techniques. Bland-Altman analysis can also be used to check the repeatability of a measurement technique within the same subject and to determine a repeatability coefficient. With an adaptation of the calculation of the agreement limits, the average of multiple measurements for each subject with two measurement techniques can be used for the Bland-Altman analysis.

[Abdominal aorta lesion during surgical treatment of a foraminal disk hernia]. / Plaie de l'aorte abdominale au cours d'une cure de hernie discale.

We report a case of an abdominal aorta lesion on a 54-year-old woman, who underwent surgery for the treatment of a foraminal disk hernia. At the end of the hernia repair, a sudden hypovolaemic collapse occurred. A computed tomography revealed an abdominal aorta disruption and a retroperitoneal haematoma. An endovascular treatment was preferred to a surgical reintervention and an endoluminal stent-graft was inserted; the postoperative course was uneventful. This case report describes an example of vascular complications of disk hernia surgery which are rare but potentially serious. It emphasizes the increasing development of endovascular procedures and their utility in the treatment of acute contained aortic disruption.

[Control of the ratio of the flow rate of the substitution fluid to the blood removal rate during preoperative normovolemic hemodilution]. / Asservissement du débit d'administration du soluté de substitution à celui du prélèvement sanguin au cours de l'hémodilution normovolémique préopératoire.

Twenty-one patients (mean age 46 +/- 13 years) due to undergo abdominal or ENT surgery, presumed to give rise to an important blood loss were included in this study. None had any contra-indication to the use of normovolaemic haemodilution (NH). Mean initial haematocrit was 40.3 +/- 1.8%. Their estimated total blood volume was 4,867 +/- 857 ml. The patients were anaesthetized with thiopentone, fentanyl, vecuronium or atracurium. Maintenance was carried out with isoflurane (0.5% during NH). Usual haemodynamic monitoring was used throughout. The required haematocrit was decided on before starting NH. The amount of blood to be removed was calculated with usual mathematical formulae. A radial artery cannula (n = 7), or a subclavian or femoral venous cannula (n = 14) was used to remove blood, which was collected within a bag containing CPC-adenine. Six % hydroxyethyl starch (Elohes) was given through a short venous cannula some distance from the first one. An antiparallel double line set in a roller pump was used to carry out the NH. A mean 1,341 +/- 405 ml of blood were withdrawn so as to reach a mean haematocrit of 30.6 +/- 2.4%. NH was completed within 17 +/- 6 min. No major haemodynamic changes occurred during the procedure. No significant differences were observed between expected and observed final haematocrits. There was no effect of the volume of blood withdrawn on the error of haematocrit prediction (0.5 +/- 0.3%). However, a higher rate of blood removal could increase this error. This easy-to-use device seems to provide fast and identical rates of blood removal and replacement. The expected haematocrit may thus be reached reliably, even if this must be checked for the sake of safety.

[Comparison of the antithrombotic effects of heparin, enoxaparin and prostacycline in continuous hemofiltration]. / Comparaison des effets antithrombotiques de l'héparine, l'énoxaparine et la prostacycline au cours de l'hémofiltration continue.

Continuous anticoagulation is required during haemofiltration to prevent the deposition of fibrin and the formation of thrombus which would lead to early clotting of the haemofilter. This study aimed to compare the efficiencies of 3 different anticoagulation protocol: 150 IU.kg-1.day-1 heparin (group HEP), 1.2 mg.kg-1.day-1 enoxaparin (group ENX), and a combination of 0.8 mg.kg-1.day-1 enoxaparin with 5 ng.kg-1.min-1 prostaglandin I2 (group ENX and PGI2). A flat ANS69S (Hospal) haemofilter was used for continuous venovenous haemofiltration. Antithrombotic efficiency was assessed with a haemofilter permeability index (HPI) including the transmembraneous pressure gradient and the rate of production of ultrafiltrate. The time required for HPI to decrease to 1/3 of its initial value (HPI1/3) was used to compare the 3 protocols. Treatment tolerance was judged by monitoring the usual haemodynamic and haemostatic parameters. No adverse effects (bleeding, thrombosis, hypotension) were observed. HPI1/3 was 15.1 +/- 2.4 h, 18.3 +/- 3.1 h and 28.2 +/- 4.2 h in groups HEP, ENX and ENX and PGI2 respectively. High dose enoxaparin reached antithrombotic efficiency without increasing the risk of haemorrhage. The use of low doses of prostaglandin I2 greatly increased HPI1/3, without any deleterious haemodynamic effects. However, the high cost of prostaglandin I2 needs to be put in the balance with the increase in duration of haemofilter life. Therefore, further investigations are required to evaluate the possible synergy between heparin and prostaglandin I2, as well as the biological parameters which need to be monitored.