Impact of balanced tetrastarch raw material on perioperative blood loss: a randomized double blind controlled trial

BACKGROUND

As 6% hydroxyethyl starch (HES) 130/0.40 or 130/0.42 can originate from different vegetable sources, they might have different clinical effects. The purpose of this prospective, randomized, double-blind controlled trial was to compare two balanced tetrastarch solutions, one maize-derived and one potato-derived, on perioperative blood loss in patients undergoing cardiac surgery with cardiopulmonary bypass (CPB).

METHODS

We randomly assigned 118 patients undergoing elective cardiac surgery into two groups, to receive either a maize- or a potato-derived HES solution. Study fluids were administered perioperatively (including priming of CPB) until the second postoperative day (POD#2) using a goal directed algorithm. The primary outcome was calculated postoperative blood loss up to POD#2. Secondary outcomes included short-term incidence of acute kidney injury (AKI), and long-term effect (up to one yr) on renal function.

RESULTS

Preoperative and intraoperative characteristics of the subjects were similar between groups. Similar volumes of HES were administered (1950 ml [1250-2325] for maize-HES and 2000 ml [1500-2700] for potato-HES; P=0.204). Calculated blood loss (504 ml [413-672] for maize-HES vs 530 ml [468-705] for potato-HES; P=0.107) and the need for blood components were not different between groups. The incidence of AKI was similar in both groups (P=0.111). Plasma creatinine concentration and glomerular filtration rates did vary over time, although changes were minimal.

CONCLUSIONS

Under our study conditions, HES 130/0.4 or 130/0.42 raw material did not have a significant influence on perioperative blood loss. Moreover, we did not find any effect of tetrastarch raw material composition on short and long-term renal function.

CLINICAL TRIAL REGISTRATION

EudraCT number: 2011-005920-16.

Spinal fentanyl vs. sufentanil for post-operative analgesia after C-section: a double-blinded randomised trial

BACKGROUND

Fentanyl and sufentanil are the most commonly administered intrathecal lipophilic opioids worldwide, although their relative efficacy when given by this route is not well characterised. The primary endpoint of this prospective, randomised, double-blind study was to compare effective analgesia duration of intrathecal administered fentanyl 25 μg and sufentanil 2.5 or 5 μg, Second endpoints were to compare post-operative morphine consumption and incidence of side effects between these opioids dosages.

METHODS

After IRB approval, 180 full-term parturients undergoing elective Caesarean section were randomly allocated into three groups, according to the opioid added to 10 mg intrathecal hyperbaric bupivacaine: fentanyl 25 μg, sufentanil 2.5 μg or sufentanil 5 μg. Total effective analgesia was defined as time from spinal injection (T0) to first IV morphine requirement (T1) administered with a patient controlled intravenous pump. Statistical data analysis included non-parametric tests and chi-squared. A P value < 0.05 was considered statistically significant. Data are presented as median [interquartile ranges 25-75].

RESULTS

Duration of analgesia was significantly longer with sufentanil 2.5 μg (214 min [189-251]) and 5 μg (236 min [190-372]) compared to fentanyl 25 μg (187 min [151-230]) (P < 0.01). Morphine consumption at T1 + 4 h was lower in the sufentanil groups (6 mg [3-9] and 6 mg [2-10]) than in the fentanyl group (9 mg [5-13]) (P < 0.01). Incidence of adverse effects was not different between groups.

CONCLUSION

In the conditions of our study, sufentanil 5 μg was the opioid of choice, associated with the best quality of anaesthesia without increased incidence of side effects.

Effect of dexamethasone on nausea, vomiting, and pain in paediatric tonsillectomy

BACKGROUND

The efficacy of dexamethasone (DEX) to reduce morbidity after paediatric tonsillectomy remains controversial. We evaluated the effect of 0.15 and 0.5 mg kg(-1) DEX on the incidence of postoperative nausea and vomiting (PONV) and on pain intensity after paediatric tonsillectomy.

METHODS

A total of 147 children aged 2-8 yr undergoing elective tonsillectomy were included in this prospective randomized double-blind study. At the induction of anaesthesia, subjects received 0.15 mg kg(-1) (DEX 0.15), 0.5 mg kg(-1) (DEX 0.5) DEX, or an equivalent volume of saline solution (placebo). Anaesthetic and surgical techniques were standardized. The incidence of PONV and the need for anti-emetic drugs and additional analgesia (tramadol and/or morphine) were recorded. Postoperative pain was assessed using the Children's Hospital of Eastern Ontario Pain Scale, the visual analogue scale, and the postoperative pain measure for parents.

RESULTS

The incidence of early PONV (primary outcome variable) was lower in both DEX groups (DEX 0.15: 21%; DEX 0.5: 22%; placebo: 49%; P=0.001). The incidence of severe pain was reduced in the DEX groups on the second postoperative day (DEX 0.15: 20%; DEX 0.5: 5%; placebo: 47%; P<0.001). The study was not powered to assess a difference between the two DEX dose groups.

CONCLUSIONS

A single i.v. injection of DEX at the induction of anaesthesia was effective in reducing the incidence of early and late PONV and the level of pain on the second postoperative day. A 0.15 mg kg(-1) DEX dose appeared to be as effective as a 0.5 mg kg(-1) dose to reduce the incidence of PONV.

Recommendations in the event of a suspected transfusion-related acute lung injury (TRALI)

The following recommendations, which aim at improving the clinical diagnosis ofTRALI and the laboratory investigations that can support it, were drawn up by a working group of the Superior Health Council. TRALI is a complication of blood transfusion that is both serious and underreported. Systematic reporting may help to develop preventive actions. Therefore, the Superior Health Council recommends that there should be a more stringent surveillance of patients who receive a blood component transfusion. The clinician should pay very close attention to any change in the patient's respiratory status (cf. dyspnoea and arterial desaturation), which should be notified systematically to the haemovigilance contact person in the hospital.

Sedation in digestive endoscopy: the Athens international position statements

BACKGROUND

Guidelines and practice standards for sedation in endoscopy have been developed by various national professional societies. No attempt has been made to assess consensus among internationally recognized experts in this field.

AIM

To identify areas of consensus and dissent among international experts on a broad range of issues pertaining to the practice of sedation in digestive endoscopy.

METHODS

Thirty-two position statements were reviewed during a 1 (1/2)-day meeting. Thirty-two individuals from 12 countries and four continents, representing the fields of gastroenterology, anaesthesiology and medical jurisprudence heard evidence-based presentations on each statement. Level of agreement among the experts for each statement was determined by an open poll.

RESULTS

The principle recommendations included the following: (i) sedation improves patient tolerance and compliance for endoscopy, (ii) whenever possible, patients undergoing endoscopy should be offered the option of having the procedure either with or without sedation, (iii) monitoring of vital signs as well as the levels of consciousness and pain/discomfort should be performed routinely during endoscopy, and (iv) endoscopists and nurses with appropriate training can safely and effectively administer propofol to low-risk patients undergoing endoscopic procedures.

CONCLUSIONS

While the standards of practice vary from country to country, there was broad agreement among participants regarding most issues pertaining to sedation during endoscopy.

Nuclear forward scattering of synchrotron radiation in pulsed high magnetic fields

We report the demonstration of nuclear forward scattering of synchrotron radiation from 57Fe in ferromagnetic alpha iron in pulsed high magnetic fields up to 30 T. The observed magnetic hyperfine field follows the calculated high field bulk magnetization within 1%, establishing the technique as a precise tool for the study of magnetic solids in very high magnetic fields. To perform these experiments in pulsed fields, we have developed a detection scheme for fully time resolved nuclear forward scattering applicable to other pump probe experiments.

Guidelines for the use of fresh frozen plasma

Recommendations, which aim at standardising and rationalising clinical indications for the transfusion of fresh frozen plasma (FFP) in Belgium, were drawn up by a working group of the Superior Health Council. For this purpose the Superior Health Council organised an expert meeting devoted to "Transfusion Guidelines: Pathogen reduction, products and indications for the transfusion of plasma" in collaboration with the Belgian Haematological Society.The experts discussed the indications for the transfusion of FFP, pathogen reduction for FFP and the practical issues of administering FFP and plasma-derived concentrates. The recommendations formulated by the experts were validated by the working group with the purpose of harmonising FFP transfusion in Belgian hospitals.

Guidelines for the transfusion of red cells

The following recommendations, which aim at standardising and rationalising clinical indications for the transfusion of red cells in Belgium, were drawn up by a working group of the Superior Health Council. To this end, the Superior Health Council organised an expert meeting devoted to "Guidelines for the transfusion of red cells" in collaboration with the Belgian Hematological Society. The experts discussed the indications for red cell transfusions, the ideal red cell concentrate, the practical issues of administering red cells, and red cell transfusions in patients in a critical condition. The recommendations formulated by the experts were validated by the working group with the purpose of harmonising red cell transfusion in Belgian hospitals.

[Postoperative pain management in ambulatory pediatric surgery]

Over the last fifteen years, child's pain has become one of our major concerns. In spite of this evolution, it remains one of the most frequent complications after ambulatory surgery. It is thus essential to implement all the resources we have at our disposal in order to optimize pain management. This can be obtained by basing our strategy on the concept of multimode analgesia. It is consequently essential that each team can achieve its own quality program; the corollary will be the development of clear recommendations for the parents with a systematic analgesics regulation at home and the possibility to resort to the family doctor or to the ambulatory centre in the event of persistence of pain.

Oral clonidine vs midazolam in the prevention of sevoflurane-induced agitation in children. A prospective, randomized, controlled trial †

BACKGROUND

This randomized, double-blind study tested the hypothesis that, in comparison with midazolam, premedication with oral clonidine reduces the incidence of emergence agitation in preschool children anaesthetized with sevoflurane.

METHODS

Sixty-eight ASA I-II children undergoing circumcision were randomized into three groups to receive different oral premedication given 30 min before anaesthesia: midazolam 0.5 mg kg-1, clonidine 2 microg kg-1, and clonidine 4 microg kg-1. Sevoflurane anaesthesia was administered via a facemask (O2/N2O: 40/60). Analgesia was with penile block (bupivacaine 0.5% 0.3 ml kg-1) and rectal paracetamol (30 mg kg-1). During the first postoperative hour, children were evaluated using a modified 'objective pain scale'.

RESULTS

Only the 4 microg kg-1 dose of clonidine was associated with a significant reduction in emergence agitation. Fewer children in the clonidine 4 microg kg-1 group displayed agitation (25%) than in the midazolam group (60%) (P=0.025). Incidence of hypotension and bradycardia, time to first micturition and first drink did not differ among groups.

CONCLUSIONS

In comparison with midazolam, clonidine 4 microg kg-1 reduced sevoflurane-induced emergence agitation without increasing postoperative side-effects.

Blood conservation strategies in cardiac surgery

Despite the continuous efforts to increase the safety of blood components, red blood cell transfusions remain associated with some risks and side effects. Therefore, numerous techniques have been developed to decrease blood use, but they also carry risks and bear costs. Most of them are frequently used in cardiac surgery, which still consumes a large part of the available blood supply. Among western countries the use of alternative techniques, but also transfusion practice, has been shown to vary markedly. 'Blood conservation' is a global concept engulfing all possible strategies aimed at reducing patients' exposure to allogeneic blood components. The development of the 'best strategy' consists of the selection of those techniques that are most appropriate to the local specific situation. It implies the establishment of a reliable system, collecting data both at the surgical team and at the medical level.

Volume optimization in surgical patients: wet or dry?

Perioperative fluid therapy remains the subject of active controversy. Indeed, clinical trials investigating the effects of fluid administration on outcome in surgical patients report controversial results. Critical review of these trials reveals that current standard fluid therapy is not at all evidence-based. Although it is evident that fluid overload should be avoided, replacement of fluid lost clearly improves outcome. The debate "Wet or Dry" is not a real one. Fluids should be administered in the perioperative period through a goal-directed approach taking into account patients characteristics and surgical-related events, and not through a "recipe book" approach. The type of fluid to be administered should depend on the specific space that needs to be restored (intracellular, extracellular or intravascular) and on the pharmacokinetic properties of the different solutions.

A standardized multidisciplinary approach reduces the use of allogeneic blood products in patients undergoing cardiac surgery

PURPOSE

Individual and institutional practices remain an independent predictor factor for allogeneic blood transfusion. Application of a standardized multidisciplinary transfusion strategy should reduce the use of allogeneic blood transfusion in major surgical patients.

METHODS

This prospective non randomized observational study evaluated the effects of a standardized multidisciplinary transfusion strategy on allogeneic blood products exposure in patients undergoing non-emergent cardiac surgery. The developed strategy involved a standardized blood conservation program and a multidisciplinary allogeneic blood transfusion policy based mainly on clinical judgement, not only on a specific hemoglobin concentration. Data obtained in a first group including patients operated from September 1997 to August 1998 (Group pre: n=321), when the transfusion strategy was progressively developed, were compared to those obtained in a second group, including patients operated from September 1998 to August 1999 (Group post: n=315) when the transfusion strategy was applied uniformly.

RESULTS

Patient populations and surgical procedures were similar. Patients in Group post underwent acute normovolemic hemodilution more frequently, had a higher core temperature at arrival in the intensive care unit and presented lower postoperative blood losses at day one. Three hundred forty units of packed red blood cells were transfused in 33% of the patients in Group pre whereas 161 units were transfused in 18% of the patients in Group post (P <0.001). Pre- and postoperative hemoglobin concentrations, mortality and morbidity were not different among groups.

CONCLUSION

Development of a standardized multidisciplinary transfusion strategy markedly reduced the exposure of cardiac surgery patients to allogeneic blood.

Comparative effects of red blood cell transfusion and increasing blood flow on tissue oxygenation in oxygen supply-dependent conditions

Red blood cell (RBC) transfusion is usually administered to improve oxygen delivery (DO(2)) in order to sustain tissue oxygen demand. However, this practice is not supported by firm clinical or experimental data. Using a randomized two-period crossover design, this study compared the efficacy of "fresh" RBC transfusion and increased blood flow to restore tissue oxygenation in oxygen supply-dependent conditions. In 12 ketamine-anesthetized mongrel dogs submitted to nonpulsatile normothermic cardiopulmonary bypass, DO(2) was reduced by a progressive decrease in pump flow. DO(2) dependency was defined as an O(2) uptake (V O(2)) decrease by more than 15% from baseline value. Then, intervention consisted of a 40% increase in DO(2) obtained either by transfusion of "fresh" dog's RBC (stored < 3 d) or by increase in pump flow. Animals received both interventions sequentially in a random order, while O(2) saturation was maintained constant. In O(2) supply-dependent conditions, rising pump flow from 1.6 +/- 0.4 to 2.7 +/- 0.7 L/ min increased DO(2) from 5.4 +/- 1.1 to 9.0 +/- 1.3 ml/kg/min (p < 0.01) and V O(2) from 3.5 +/- 0.4 to 4.1 +/- 0.5 ml/kg/min (p = 0.02). "Fresh" RBC transfusion, which increased the hemoglobin concentration from 6.4 +/- 0.9 to 11.1 +/- 1.3 g/dl, increased DO(2) from 5.4 +/- 1.2 to 9.0 +/- 1.4 ml/kg/min (p < 0.01) and V O(2) from 3.6 +/- 0.4 to 4.1 +/- 0.5 ml/kg/min (p = 0.02). There was no difference in V O(2) resulting from both interventions. In oxygen supply-dependent conditions, "fresh" RBC transfusion and increased blood flow are equally effective in restoring tissue oxygenation.

Effects of propofol, etomidate, and pentobarbital on critical oxygen delivery

OBJECTIVE

To test the hypothesis that propofol, etomidate, and pentobarbital increase critical oxygen delivery in a dose-dependent manner during progressive hemorrhage.

DESIGN

Prospective, randomized laboratory investigation.

SETTING

University laboratory.

SUBJECTS

A total of 40 anesthetized, paralyzed, and mechanically ventilated dogs weighing 29.2+/-4.6 kg.

INTERVENTIONS

Dogs were randomly assigned to be anesthetized with propofol (n = 13), etomidate (n = 13), or pentobarbital (n = 14) at either low or high dosages. At 30 mins after splenectomy, the dogs underwent progressive hemorrhage by successive withdrawals of 3-5 mL/kg arterial blood.

MEASUREMENTS AND MAIN RESULTS

At each step of hemorrhage, oxygen consumption and oxygen delivery were determined. Oxygen consumption was obtained from expired gas analysis, and oxygen delivery was determined from thermodilution cardiac output and calculated arterial oxygen content. In each animal, critical oxygen delivery and critical oxygen consumption were obtained from a plot of oxygen consumption vs. oxygen delivery as the point of intersection of the two best-fit regression lines determined by a least sum of squares method. Critical oxygen extraction was obtained by dividing critical oxygen consumption by critical oxygen delivery. In the three groups, animals receiving the higher anesthetic infusion had a significantly higher critical oxygen delivery (propofol: 10.5+/-0.8 vs. 13.9+/-2.5 mL/min/m2, p < .05; etomidate: 10.1+/-0.7 vs. 13.4+/-3.0 mL/min/m2, p < .05; pentobarbital: 7.8+/-1.0 vs. 12.3+/-2.5 mL/min/m2, p < .01) attributable to a lower critical oxygen extraction ratio (propofol: 41.1+/-6.4% vs. 54.2+/-2.5%, p < .01; etomidate: 42.7+/-10.2% vs. 60.6+/-7.1%, p < .01; pentobarbital: 42.2+/-7.2% vs. 64.3+/-8.8%, p < .01).

CONCLUSIONS

This study indicates that propofol, etomidate, and pentobarbital increased critical oxygen delivery in a dose-dependent manner. This effect was mainly related to a decrease in tissue oxygen extraction capabilities.

Critical haemoglobin concentration in anaesthetized dogs: comparison of two plasma substitutes

We have explored systemic and regional tolerance to haemodilution during anaesthesia with two different synthetic colloids. Eighteen dogs undergoing mechanical ventilation during anaesthesia with ketamine were submitted to progressive normovolaemic haemodilution with either gelatin (GEL; n = 9) or hydroxyethylstarch (HES; n = 9) administered on a 1:1 ratio. Systemic oxygen delivery was calculated from measurement of thermodilution cardiac output and arterial oxygen content, while systemic oxygen consumption was determined from expired gas analysis. Mesenteric oxygen delivery and consumption were determined using ultrasonic flow measurements, and arterial and mesenteric venous oxygen contents. The critical haemoglobin concentration (i.e. the haemoglobin value below which oxygen consumption becomes oxygen delivery dependent) was mean 3.6 (SD 0.8) g dl-1 in the GEL and 3.5 (1.5) g dl-1 in the HES group. The mesenteric critical oxygen extraction ratio (O2ER) (GEL 50.1 (12.1)%; HES 48.5 (13.4)%) was significant lower than the systemic critical O2ER (GEL 66.1 (8.4)%; HES 67.7 (7.1)%). There were no significant differences between the GEL and HES groups for any of these variables, or in the amount of colloid administered. During the study, oxygen delivery decreased almost linearly with reduction in haemoglobin, indicating a lack of cardiac output response to anaemia during ketamine anaesthesia.

Antiallergic and antitussive medications: extent of use and relationship to asthma exacerbations

BACKGROUND

Asthma patients are frequently exposed to antiallergic and antitussive medications, in addition to their respiratory treatment. These medications interfere with inflammatory pathways common to all atopic diseases and could affect asthma.

OBJECTIVES

To investigate associations between antiallergic and antitussive medications and the occurrence of asthma exacerbations and to assess the extent of use of these medications in asthma.

METHODS

Regular users of anti-asthma medications were identified in a drug dispensing database. A base-cohort of asthma patients was identified using age and exposure criteria. A nested case-control study was performed within the base-cohort: the outcome was defined as a new dispensing of oral corticosteroids and matched cases and controls were compared regarding exposure to antiallergic medications. Odds ratios (OR) were computed by conditional logistic regression and adjustment incorporated markers for asthma severity.

RESULTS

680 asthma patients were followed in the base-cohort for an average duration of 1390 days. Antitussives, antihistamines and nasal corticosteroids were used by respectively 40, 30 and 13 per cent of the asthma population. Among the patients, 134 cases were pair matched with controls. In these pairs, antitussives showed a significant association with asthma exacerbations, with an OR of 3.1. The association had borderline significance for antihistamines and was not significant for nasal corticosteroids. The results were not modified by adjustment for disease severity.

CONCLUSIONS

This study confirms that antitussives and antihistamines are commonly used by asthmatics and indicates that both classes are associated with increased occurrence of asthma exacerbations; assessing causality from present data is, however, difficult. Nasal corticosteroids are used less often and are not associated with the outcome. Antihistamine and antitussive medications should be more thoroughly investigated in asthma patients.

Pulmonary hypertension after transjugular intrahepatic portosystemic shunt: effects on right ventricular function

The short- and mid-term hemodynamic effects of transjugular intrahepatic portosystemic shunt (TIPS) were studied in 16 sedated cirrhotic patients. Indications included relapsing variceal bleeding (n = 10) and refractory ascites (n = 6). The decrease of porto-atrial pressure gradient (from 20.4 +/- 4.2 mm Hg to 10.1 +/- 2.4 mmHg; P < .05) was associated with an increase of mean pulmonary artery pressure (MPAP) (from 12.3 +/- 3.0 mm Hg to 20.3 +/- 5.3 mm Hg; P < .05) and of right atrial pressure (RAP) from 3.4 +/- 2.6 mm Hg to 8.3 +/- 3.7 mm Hg; P < .05), whereas right ventricular end-diastolic volume (RVEDVI) remained unchanged. The significant increase of cardiac index (CI) (from 4.5 +/- 1.2 L/min/m2 to 5.0 +/- 1.1 L/min/m2; P < .05) was essentially attributable to an increase of heart rate (HR) (from 81 +/- 11 to 88 +/- 10 beats/min; P < .05). Systemic vascular resistance (SVR) decreased (from 812 +/- 281 to 666 +/- 191 dynes/sec/cm5; P < .05), whereas pulmonary vascular resistance (PVR) increased (from 60.6 +/- 29.6 to 82.0 +/- 34.6 dynes/sec/cm5; P < .05). After transient shunt occlusion with a balloon catheter, all of the hemodynamic parameters returned to baseline values, except pulmonary artery pressure, which also decreased but remained significantly increased. One month after TIPS, pulmonary pressure remained elevated, and CI further increased. It is concluded that increased PVR is the major hemodynamic alteration occurring after TIPS placement. It correlates with the decrease of porto-atrial gradient and is probably mediated by both mechanical and neurohumoral factors.

Pulmonary hypertension after transjugular intrahepatic portosystemic shunt: effects on right ventricular function

The short- and mid-term hemodynamic effects of transjugular intrahepatic portosystemic shunt (TIPS) were studied in 16 sedated cirrhotic patients. Indications included relapsing variceal bleeding (n = 10) and refractory ascites (n = 6). The decrease of porto-atrial pressure gradient (from 20.4 +/- 4.2 mm Hg to 10.1 +/- 2.4 mmHg; P < .05) was associated with an increase of mean pulmonary artery pressure (MPAP) (from 12.3 +/- 3.0 mm Hg to 20.3 +/- 5.3 mm Hg; P < .05) and of right atrial pressure (RAP) from 3.4 +/- 2.6 mm Hg to 8.3 +/- 3.7 mm Hg; P < .05), whereas right ventricular end-diastolic volume (RVEDVI) remained unchanged. The significant increase of cardiac index (CI) (from 4.5 +/- 1.2 L/min/m2 to 5.0 +/- 1.1 L/min/m2; P < .05) was essentially attributable to an increase of heart rate (HR) (from 81 +/- 11 to 88 +/- 10 beats/min; P < .05). Systemic vascular resistance (SVR) decreased (from 812 +/- 281 to 666 +/- 191 dynes/sec/cm5; P < .05), whereas pulmonary vascular resistance (PVR) increased (from 60.6 +/- 29.6 to 82.0 +/- 34.6 dynes/sec/cm5; P < .05). After transient shunt occlusion with a balloon catheter, all of the hemodynamic parameters returned to baseline values, except pulmonary artery pressure, which also decreased but remained significantly increased. One month after TIPS, pulmonary pressure remained elevated, and CI further increased. It is concluded that increased PVR is the major hemodynamic alteration occurring after TIPS placement. It correlates with the decrease of porto-atrial gradient and is probably mediated by both mechanical and neurohumoral factors.

[Clinical practice interpretation of oncotic pressure, serum albumin and protein determination and their ability for guiding therapeutics in cases of disturbances of capillary exchanges]

The osmotic pressure of the serum proteins, the colloid osmotic pressure (COP) or oncotic pressure, is one of the four Starling forces determining fluid movements across a capillary. Theoretical and empirical formulas considering plasma protein or albumin concentration have been used. However, such calculations are only approximations, being inadequate especially when protein fractionation pattern is abnormal or when artificial colloids are used. It is preferable to measure COP directly. In healthy standing adults COP is around 25 mmHg. It is influenced by age, position, blood pressure and pH. The interpretation of the COP must take into account, on the one hand the possible variations of the other factors involved in the Starling's equilibrium and, on the other hand the structural and functional differences between systemic and pulmonary circulations. When capillary permeability is not altered, a decreased COP is associated with an increased filtration rate across the capillaries, resulting in oedema in skeletal muscle, skin, subcutaneous tissue, intestine and heart. The lung is relatively insensitive to extravascular fluid shifts caused by lowering of the COP, due to the efficacy of the pulmonary lymph drainage and the high pulmonary interstitial protein concentration. The main determinant of fluid exchange in the lung is then the hydrostatic force, reflected by the pulmonary artery wedge pressure. When capillary permeability is altered, the decreased reflectance coefficient results in a smaller effect of the COP on interstitial oedema formation. Several studies demonstrated that oedema formation in the injured tissues seems unaffected by changes in COP. During fluid resuscitation, COP measurement is useful for assessing the risks of peripheral oedema formation and additional measurements of pulmonary artery wedge pressure for assessing the risks of pulmonary oedema. Therefore COP measurement can serve as a useful guide for selection of colloids or crystalloids in critically ill patients, avoiding expensive albumin administrations.

Detection of tissue hypoxia by arteriovenous gradient for PCO2 and pH in anesthetized dogs during progressive hemorrhage

The present study tested the hypothesis that, during acute bleeding, the development of tissue hypoxia might be reflected by an abrupt widening in arteriovenous gradient for PCO2 (AV PCO2) and for pH (AV pH) as accurately as by an increase in blood lactate levels. Twenty-four anesthetized (isoflurane 1.4% end-tidal), paralyzed, and mechanically ventilated dogs submitted to progressive hemorrhage were studied. Oxygen uptake (VO2) was derived from expired gas analysis and oxygen delivery (DO2) was calculated by the product of the thermodilution cardiac index and the arterial O2 content. During the first part of the protocol, VO2 remained stable as the progressive reduction in DO2 was associated with a corresponding increase in O2 extraction (O2ER). Blood lactate increased slightly but not significantly. AV PCO2 and AV pH increased significantly, essentially related to venous respiratory acidosis. The critical value of DO2 below which VO2 decreased was 8.95 +/- 1.60 mL.min-1.kg-1. Below this value, there was a marked increase in blood lactate and an abrupt widening in AV PCO2 and AV pH gradients. The critical value of DO2 obtained from blood lactate, AV PCO2 and AV pH were similar to those obtained from VO2 (8.60 +/- 1.12; 8.73 +/- 1.40; 8.78 +/- 1.37, respectively; P = not significant). A significant correlation was found, during the hemorrhage protocol, between blood lactate and AV PCO2 (r = 0.84; P < 0.001) or AV pH (r = 0.78; P < 0.001). Therefore, AV PCO2 and AV pH represent simple but reliable indicators of tissue hypoxia during hemorrhagic shock.

Cardiovascular effects of moderate normovolaemic haemodilution during enflurane-nitrous oxide anaesthesia in man

The cardiovascular effects of mild normovolaemic haemodilution during enflurane-nitrous oxide anaesthesia were studied in 20 patients with normal cardiac function before, during and after total hip replacement. After induction of anaesthesia, patients were randomly allocated to one control group (C), or one haemodiluted group (H) where Hct was decreased to 30% by replacement of blood volume by an identical volume of hydroxyethyl starch 200/05. Each patient was monitored with a pulmonary artery catheter allowing the measurement of right ventricular ejection fraction. During haemodilution, stroke index and right ventricular end-diastolic volume index increased from 33.1 +/- 7.9 to 39.3 +/- 7.1 ml.M-2 and from 73.8 +/- 20.3 to 94.9 +/- 18.5 ml.M-2 respectively (mean +/- s.d., both P < 0.05). However, heart rate decreased so that cardiac index did not change. O2 delivery decreased significantly (from 389 +/- 70 to 311 +/- 63 ml.min-1.m-2; P < 0.05), but was not different to the control group. O2 consumption was maintained by an increase in O2 extraction. During the surgical procedure, cardiac index was higher in the haemodiluted group than in the control group, so that O2 delivery was similar in the two groups. O2 consumption tended to be greater in the haemodiluted group. In patients with normal cardiac function, enflurane-nitrous oxide anesthesia could alter the normal physiologic response to mild normovolaemic haemodilution.

Influence of hematocrit on tissue O2 extraction capabilities during acute hemorrhage

This study was performed to test the hypothesis that tissue O2 extraction capabilities during hemorrhage may be greater when hematocrit (Hct) is initially reduced. Twenty-four anesthetized and splenectomized dogs were randomly assigned in three groups of eight dogs each: group 1 (Hct 40), 40-45% Hct; group 2 (Hct 30), 30-35% Hct; and group 3 (Hct 20), 20-25% Hct. In each animal, the desired Hct was obtained by normovolemic hemodilution using hydroxyethyl starch 450/0.7 and maintained throughout the experiment. O2 delivery (DO2) was progressively reduced by hemorrhage. At each step, DO2 and O2 consumption (VO2) were measured separately. Critical DO2 obtained from a plot of VO2 vs. DO2 was lower in the Hct 30 and Hct 20 groups than in the Hct 40 group [(in ml.min-1.kg-1) Hct 30, 7.9 +/- 2.2; Hct 20, 7.8 +/- 1.0; Hct 40, 10.4 +/- 1.1; P < 0.05]. Critical DO2 obtained from blood lactate levels was also significantly lower in the Hct 30 and Hct20 groups than in the Hct 40 group. Critical O2 extraction ratio was also greater in the Hct 30 and Hct 20 groups than in the Hct 40 group (Hct 30, 73.0 +/- 13.9%; Hct 20, 70.1 +/- 9.6%; Hct 40, 57.1 +/- 11.5%; P < 0.05). In the conditions of our study, moderate hemodilution was associated with an improvement of the O2 extraction capabilities of the body, probably related to the reduction in blood viscosity.

Effects of anesthetic agents on systemic critical O2 delivery

The present study tested the hypothesis that anesthetic agents can alter tissue O2 extraction capabilities in a dog model of progressive hemorrhage. After administration of pentobarbital sodium (25 mg/kg iv) and endotracheal intubation, the dogs were paralyzed with pancuronium bromide, ventilated with room air, and splenectomized. A total of 60 dogs were randomized in 10 groups of 6 dogs each. The first group served as control (C). A second group (P) received a continuous infusion of pentobarbital (4 mg.kg-2.h-2), which was started immediately after the bolus dose. Three groups received enflurane (E), halothane (HL), or isoflurane (I) at the end-tidal concentration of 0.7 minimum alveolar concentration (MAC). The sixth group received halothane at the end-tidal concentration of 1 MAC (HH). Two groups received intravenous alfentanil at relatively low dose (AL) or high dose (AH). The last two groups received intravenous ketamine at either relatively low dose (KL) or high dose (KH). In each group, O2 delivery (Do2) was progressively reduced by hemorrhage. At each step, systemic Do2 and O2 consumption (VO2) were measured separately and the critical point was determined from a plot of Vo2 vs. Do2. The critical O2 extraction ratio (OER) in the control group was 65.0 +/- 7.8%. OER was lower in all anesthetized groups (P, 44.3 +/- 11.8%; E, 47.0 +/- 7.7%; HL, 45.7 +/- 11.2%; I, 44.3 +/- 7.1%; HH, 33.7 +/- 6.0%; AL, 56.5 +/- 9.6%; AH, 43.5 +/- 5.9%; KH, 57.7 +/- 7.1%), except in the KL group (78.3 +/- 10.0%). The effects of halothane and alfentanil on critical OER were dose dependent (P less than 0.05), whereas critical OER was significantly lower in the KH than in the KL group. Moreover, the effects of anesthetic agents on critical Do2 appeared related to their effects on systemic vascular resistance. Anesthetic agents therefore alter O2 extraction by their peripheral vascular effects. However, ketamine, with its unique sympathetic stimulant properties, had a lesser effect on OER than the other anesthetic agents. It could therefore be the anesthetic agent of choice in clinical situations when O2 availability is reduced.

Adrenergic support during anesthesia in experimental endotoxin shock: norepinephrine versus dobutamine

The effects of norepinephrine and dobutamine were compared during endotoxin shock in dogs anesthetized either with enflurane (E: 1.5%, N = 12) or with i.v. ketamine (K: 5 mg.kg-1 + 0.2 mg.kg-1.min-1, N = 12). An i.v. bolus of 1.5 mg.kg-1 E. coli endotoxin was followed by saline infusion to restore left-sided filling pressures at baseline. With E, heart rate, mean arterial pressure and stroke index decreased (P less than 0.01). The decrease in oxygen delivery (DO2) and in oxygen consumption (VO2) was associated with an increase in blood lactate. In contrast, K anesthesia was associated with remarkable hemodynamic stability. DO2 was well maintained, VO2 decreased (P less than 0.01) and blood lactate did not change. Under E anesthesia, mean arterial pressure increased more with norepinephrine and heart rate increased more with dobutamine. Under K anesthesia, cardiac index, stroke index and left ventricular stroke work index increased similarly with both agents. In both groups DO2 and VO2 increased markedly. The amount of fluid infused was higher with dobutamine than with norepinephrine. Thus, enflurane but not ketamine had depressant cardiovascular effects at the doses used in this model. With both anesthetics, norepinephrine and dobutamine could effectively improve cardiac function. Dobutamine could therefore represent a valuable alternative to norepinephrine for cardiovascular support during anesthesia in septic shock.

Interleukin-6 administration has no acute hemodynamic or hematologic effect in the dog

To investigate the possible hemodynamic effects of interleukin-6 (IL-6), a single dose of 15 mcg/kg of recombinant IL-6 isolated from Escherichia coli was injected intravenously in six pentobarbital-anesthetized dogs. After 30 min, saline infusion was performed to maintain the pulmonary artery balloon-occluded pressure at baseline level. The animals were observed for up to 5 hours. No other hemodynamic alteration was observed than a gradual decline in cardiac output attributed to anesthesia. Hematologic variables, blood glucose, and total serum proteins were also constant. IL-6 levels were markedly elevated in the blood, but no tumor necrosis factor activity was detected. Thus a primary role for IL-6 in the early cardiovascular alterations associated with septic shock seems unlikely.

Comparison of halothane, isoflurane, alfentanil, and ketamine in experimental septic shock

The effects of four commonly used anesthetic agents, halothane, isoflurane, alfentanil, and ketamine, on cardiovascular function and oxygen balance were studied in a dog model of septic shock. After initial pentobarbital administration, the dogs were given Escherichia coli endotoxin (3 mg/kg) and, after 30 min, fluids to restore cardiac filling pressures to baseline levels. This resulted in a low resistance shock in all animals. Dogs were then given for 2 h either halothane (n = 9, 0.5 MAC), isoflurane (n = 9, 0.5 MAC), or alfentanil (n = 9, 150 micrograms/kg IV plus 2 micrograms.kg-1.min-1) or ketamine (n = 9, 2 mg/kg IV plus 0.2 mg.kg-1.min-1) or no anesthetic (control: n = 9). Mean arterial pressure increased in the control group (+11 +/- 18 mm Hg) and with ketamine (+10 +/- 20 mm Hg), remained unchanged with isoflurane (-2 +/- 11 mm Hg), and decreased with halothane (-22 +/- 23 mm Hg) and alfentanil (-9 +/- 23 mm Hg). Heart rate tended to increase in the control group but decreased with the four anesthetic agents, especially with alfentanil and halothane. Cardiac index and left ventricular stroke work index increased in the control group and in each anesthetic group except the halothane group. Systemic vascular resistance decreased in all groups except in the ketamine group. In the control group, the increase in cardiac index was associated with significant increases in oxygen delivery and consumption, and with a significant decrease in blood lactate levels. There was a dramatic decrease in oxygen consumption in all anesthetic groups, whereas oxygen delivery failed to increase only with halothane. Blood lactate increased significantly with halothane (5.0 +/- 1.5 to 6.3 +/- 1.4 mM/L) and isoflurane (4.8 +/- 1.1 to 5.3 +/- 1.2 mM/L), remained unchanged with alfentanil (4.5 +/- 1.5 and 4.6 +/- 0.8 mM/L), and tended to decrease with ketamine (4.9 +/- 1.4 to 4.5 +/- 1.4 mM/L). In conclusion, among the four anesthetic agents tested, halothane had the least desirable effects. Ketamine best preserved cardiovascular function and appeared to have the least deleterious effects on the hypoxic tissues. Thus, ketamine could be the anesthetic agent of choice in septic shock.

Septic shock: particular type of acute circulatory failure

Reduced cardiac output is a crucial determinant in hypovolemic, cardiogenic and obstructive types of acute circulatory failure, but cardiac output is considered less meaningful in septic shock where the primary defect is thought to be peripheral. In septic states, oxygen transport values are typically elevated, and the altered oxygen extraction (ratio of oxygen uptake over oxygen supply) limits the ability of the tissues to increase their oxygen uptake in relation to high oxygen needs. To correct tissue hypoxia, oxygen consumption should be increased to a level where oxygen uptake equals oxygen demand and lactic acidosis resolves. For a given level of oxygen demand, the best option is to improve oxygen extraction so that oxygen consumption will be higher for the same level of oxygen transport. This, however, is very difficult. Another approach can consist of further increasing oxygen transport to meet the elevated oxygen demand. Whenever possible, the metabolic needs of the tissues should be restrained.

Effects of clonidine on anesthetic drug requirements and hemodynamic response during aortic surgery

The authors studied in a double-blind placebo-controlled study the effects of oral preoperative administration of 5 micrograms/kg clonidine upon the alfentanil and droperidol requirements, hemodynamic lability, distribution of the values of heart rate and blood pressure, and plasma noradrenaline levels, in two groups of ten normotensive patients undergoing infrarenal aortic surgery. The amounts of alfentanil supplementing a standardized continuous infusion, injected to maintain hemodynamic stability, were statistically identical between the groups (P = 0.23). The amount of droperidol, however, was significantly less (P = 0.004) in the group of patients that received clonidine. The norepinephrine plasma concentrations, during the entire procedure, were lower (P = 0.001) in the clonidine group. The variability of the heart rate, systolic (SBP) and diastolic (DBP) blood pressure recorded every 5 s, and assessed by the calculation of the coefficients of variation for each patient, showed no difference between the clonidine and the placebo group. However, when the values recorded were compared to the preoperative baseline values, and divided into three categories (baseline +/- 20%--greater than 20% decrease vs. baseline--greater than 20% increase vs. baseline), the clonidine group showed a higher frequency of low heart rate and fewer episodes of tachycardia. The frequency of SBP hypertension was lower and of SBP hypotension higher in the clonidine group. After induction of anesthesia, but before surgery, there were more episodes of DBP hypotension in the clonidine group, but during dissection and vascular sutures the placebo group experienced more episodes of DBP hypotension, owing probably to the greater amount of droperidol injected. The authors conclude that the preoperative administration of clonidine decreased the need to supplement anesthetic, and modifies the profile of distribution of heart rate and blood pressure.

Determination of right ventricular volumes during aortic surgery

The aim of the present study was to evaluate right ventricular (RV) preload by measurements of right ventricular volumes during aortic clamping and unclamping. Nine patients (aged 67 +/- 9 years) undergoing infrarenal aortic aneurysmectomy were monitored with a pulmonary artery catheter equipped with a fast-response thermistor, allowing determination of RV volumes by the thermodilution technique. Anesthesia consisted of a continuous infusion of alfentanil and 50% N2O. Aortic clamping resulted in a significant decrease in cardiac index (CI) and a significant increase in systemic vascular resistance (SVR). There was no significant change in right ventricular ejection fraction (RVEF) (from 35% +/- 6% to 33% +/- 8%) in the presence of a significant decrease in stroke index (from 37.2 +/- 9.8 to 31.1 +/- 10.0 mL/beat/m2, P less than 0.05), indicating a significant decrease in RV end-diastolic volume (from 106 +/- 17 to 92 +/- 19 mL, P less than 0.01). There were no significant changes in cardiac filling pressures. Aortic unclamping was associated with a significant increase in CI and a significant decrease in SVR. There were no significant changes in cardiac filling pressures, RVEF, or RV volumes. Measurements of RV volumes indicated that aortic clamping resulted in a decrease in RV preload, which is usually not demonstrated by measurements of right atrial pressure alone.

Amrinone administration in endotoxin shock

This study explored the hemodynamic effects of amrinone, a phosphodiesterase inhibitor, in association with intravenous fluids, in the treatment of endotoxin shock. Mongrel dogs were anesthetized with pentobarbital and mechanically ventilated with room air. Treatment was started 30 min after slow intravenous administration of 3 mg/kg of E. coli endotoxin. In the first part of the study, ten dogs were resuscitated for 30 min with intravenous saline alone (10 ml/kg) and for the next 3 h by saline (10 ml/kg/h) and amrinone 40 micrograms/kg/min. During this latter period, arterial pressure remained stable while cardiac output significantly increased from 3.1 +/- 0.5 to 5.2 +/- 0.7 l/min (P less than 0.01), and oxygen delivery increased from 616 +/- 92 to 983 +/- 156 ml/min (P less than 0.01). Comparison with control animals revealed that amrinone infusion prevented the decrease in left ventricular stroke work and markedly increased oxygen delivery. In the second part of the study, 18 dogs were treated by saline infusion titrated to maintain pulmonary artery balloon-occluded pressure at baseline level. In ten dogs, amrinone was added 60 min after endotoxin administration at a dose of 40 micrograms/kg/min. Total amount of fluids infused averaged 87 +/- 14 ml in the amrinone-treated dogs and 64 +/- 15 ml in the control dogs (differences nonsignificant). Oxygen delivery and oxygen consumption increased significantly in the amrinone-treated dogs (from 541 +/- 36 to 1063 +/- 176 ml/min, P less than 0.01, and from 145 +/- 23 to 202 +/- 38 ml/min, P less than 0.01, respectively) but not in the control dogs. The amrinone-treated dogs had lower PaO2 and higher venous admixture than the control dogs.(ABSTRACT TRUNCATED AT 250 WORDS)

Dopamine compared with dobutamine in experimental septic shock: relevance to fluid administration

The hemodynamic effects of dopamine and dobutamine (at doses of 6 micrograms X kg-1 X min-1) were compared during fluid resuscitation from septic shock induced by endotoxin (3 mg/kg) in the dog. In the first part of the study, when a standard amount of saline solution was infused (in 24 dogs), dopamine infusion resulted in higher cardiac filling pressures than did dobutamine infusion, whereas dobutamine infusion resulted in higher cardiac output. In the second part of the study, when fluid infusion was titrated to maintain pulmonary artery balloon-occluded pressure at constant level (in 24 dogs), the total amount of fluids was significantly greater with dobutamine than when dopamine was used (109 +/- 13 vs 71 +/- 10 ml/kg). The combination of dobutamine with fluids resulted in significantly greater stroke volume (39.6 +/- 3.8 vs 21.0 +/- 4.0 ml, P less than 0.05) and oxygen consumption (194 +/- 18 vs 144 +/- 8 ml/min, P less than 0.05). The different effects of dopamine and dobutamine on cardiac filling pressures can be due to differences in effects on myocardial contractility, ventricular afterload, and cardiac compliance. This experimental study indicates that when fluid therapy is combined with adrenergic agents in resuscitation from septic shock, dobutamine can be associated with higher cardiac output and oxygen transport and can result in higher tissue oxygen consumption than dopamine.