Validation of a new closed circuit indirect calorimetry method compared with the open Douglas bag method

New equipment designed for the routine measurement of oxygen uptake (VO₂) using a closed circuit method has been validated by comparing it with a standard Douglas bag method. The equipment (The Caloric Measurement Unit, CMU) has been tested in 10 critically ill patients during mechanical ventilation (MV) and in 10 spontaneously breathing healthy subjects. Determinations of VO₂ and of the resting energy expenditure (REE) were measured in duplicate with the standard method and once with the CMU. Six additional patients receiving MV were studied with the CMU to evaluate the reproducibility and the effect of FIO₂=1 vs FIO₂=0.43 on VO₂ measurements. Considering the whole group of 10 patients and 10 subjects, the mean difference of VO₂ between both methods was-2±21 ml/min (95% confidence interval,-11.8 to 7.8 ml/min, p=0.6) standard deviation. Both methods had a similar reproducibility and the mean difference of VO₂ measured at the two different FIO₂ with the CMU was-3.2±11 ml/min (95% confidence interval,-14.7 to 8.4 ml/min, p=0.5). No statistically significant difference was found between derived REE values obtained from either method. These data show a good correlation between the two methods suggesting that CMU may be used in place of the standard method with the same accuracy in measurement of VO₂ even at FIO₂=1.     

Evaluation of a mobile unit for indirect calorimetry during spontaneous ventilation

Summary The Mijnhardt Oxycon-4 (OX-4), designed for measurements of gas exchange during exercise using a mouth-piece, was adapted for use in recumbant patients by the introduction of a transparent canopy and a suction device. This system was evaluated in laboratory models and in patients.     

Assessment of gas flow waves for endotracheal tube placement in an ovine model of neonatal resuscitation

Aim

Clinical assessment and end-tidal CO₂ (ETCO₂) detectors are routinely used to verify correct endotracheal tube (ETT) placement. However, ETCO₂ detectors may mislead clinicians by failing to correctly identify placement of an ETT under a variety of circumstances. A flow sensor measures and displays gas flow in and out of an ETT. We compared endotracheal flow sensor recordings with a colorimetric CO₂-detector (Pedi-Cap^®) to detect endotracheal intubation in a preterm sheep model of neonatal resuscitation.

Methods

Six preterm lambs were intubated and ventilated immediately after delivery. At 5 min the oesophagus was also intubated with a similar tube. The endotracheal tube and oesophageal tubes were attached to a Pedi-Cap^® and flow sensor in random order. Two observers, blinded to the positions of the tubes, used a ETCO₂ detector and the flow sensor recording to determine whether the tube was in the trachea or oesophagus. The experiment was repeated 10 times for each animal. In the last three animals (30 recordings) the number of inflations required to correctly identify the tube placement was noted.

Results

The Pedi-Cap^® and the flow sensor correctly identified tube placement in all studies. Thus, the sensitivity, specificity, and positive and negative predictive values of both devices were 100%. At least three, and up to 10, inflations were required to identify tube location with the Pedi-Cap^® compared to one or two inflations with the flow sensor.

Conclusion

A flow sensor correctly identifies tube placement within the first two inflations. The Pedi-Cap^® required more inflations to correctly identify tube placement.     

O2−CO2-diagram and iso-shunt-lines for assessment of pulmonary gas exchange during artificial respiration

Diagnosis and management of disturbed pulmonary gas exchange can be simplified by application of a computer subroutine with detailed information presented in a four-coloured graphical-numerical plot. The fundamentals of this computer program are the O₂–CO₂-diagram, the iso-shunt-lines and the arterio-venous acid base state.     

Reflection of differential pulmonary perfusion in polytrauma patients on differential lung ventilation (DLV)

Seventeen polytrauma patients with asymmetric pulmonary contusion were treated with differential lung ventilation (DLV). The ratios of differential values of end-tidal CO₂ concentration (ETCO₂) and CO₂ excretion ml/min ( ) were compared as indirect parameters for differential pulmonary perfusion. Both CO₂-derived methods indicated asymmetry after starting DLV suggesting asymmetric pulmonary perfusion as a consequence of contusion. Prior to stopping DLV a significant improvement in asymmetry was indicated by the differential ratios of ETCO₂ and values. The ETCO₂ ratio increased from 0.74±0.17 to 0.88±0.10, the ratio from 0.57±0.23 to 0.86±0.11. In two patients with very severe contusion who underwent bilobectomies a marked difference between the ratios of ETCO₂ and was observed. It is concluded that differential measurement of CO₂-derived variables may be useful in indicating differential perfusion in clinical practice on DLV. In very severe asymmetric contusion ETCO₂ ratios may underestimate the differential perfusion ratio.     

Hydrogen peroxide ingestion associated with portal venousgas and treatment with hyperbaric oxygen: a case seriesand review of the literature

Introduction.?Ingestion of concentrated hydrogen peroxide (H₂O^₂) has been associated with venous and arterial gas embolic events, hemorrhagic gastritis, gastrointestinal bleeding, shock, and death. Although H^₂O^₂ is generally considered a benign ingestion in low concentrations, case reports have described serious toxicity following high concentration exposures. Hyperbaric oxygen (HBO) has been used with success in managing patients suffering from gas embolism with and without manifestations of ischemia.?Methods.?Poison center records were searched from July 1999 to January 2010 for patients with H^₂O^₂ exposure and HBO treatment. Cases were reviewed for the concentration of H₂O₂, symptoms, CT scan findings of portal gas embolism, HBO treatment, and outcome.?Results.?Eleven cases of portal gas embolism were found. Ages ranged from 4 to 89 years. All but one ingestion was accidental in nature. In 10 cases 35% H^₂O^₂ was ingested and in 1 case 12% H^₂O^₂ was ingested. All abdominal CT scans demonstrated portal venous gas embolism in all cases. Hyperbaric treatment was successful in completely resolving all portal venous gas bubbles in nine patients (80%) and nearly resolving them in two others. Ten patients were able to be discharged home within 1 day, and one patient had a 3.5-day length of stay.?Conclusions.?HBO was successful in resolving portal venous gas embolism from accidental concentrated H^₂O^₂ ingestions.     

3:1 Compression to ventilation ratio versus continuous chest compression with asynchronous ventilation in a porcine model of neonatal resuscitation

Objective

In contrast to the resuscitation guidelines of children and adults, guidelines on neonatal resuscitation recommend synchronized 90 chest compressions with 30 manual inflations (3:1) per minute in newborn infants. The study aimed to determine if chest compression with asynchronous ventilation improves the recovery of bradycardic asphyxiated newborn piglets compared to 3:1 Compression:Ventilation cardiopulmonary resuscitation (CPR).

Intervention and measurements

Term newborn piglets (n = 8/group) were anesthetized, intubated, instrumented and exposed to 45-min normocapnic hypoxia followed by asphyxia. Protocolized resuscitation was initiated when heart rate decreased to 25% of baseline. Piglets were randomized to receive resuscitation with either 3:1 compressions to ventilations (3:1 C:V CPR group) or chest compressions with asynchronous ventilations (CCaV) or sham. Continuous respiratory parameters (Respironics NM3^®), cardiac output, mean systemic and pulmonary artery pressures, and regional blood flows were measured.

Main results

Piglets in 3:1 C:V CPR and CCaV CPR groups had similar time to return of spontaneous circulation, survival rates, hemodynamic and respiratory parameters during CPR. The systemic and regional hemodynamic recovery in the subsequent 4 h was similar in both groups and significantly lower compared to sham-operated piglets.

Conclusion

Newborn piglets resuscitated by CCaV had similar return of spontaneous circulation, survival, and hemodynamic recovery compared to those piglets resuscitated by 3:1 Compression:Ventilation ratio.     

Autoregulation in a Simulator-Based Educational Model of Intracranial Physiology

Objective.To implement a realistic autoregulation mechanism toenhance an existing educational brain model that displays in real-time thecerebral metabolic rate (CMRO₂), cerebral blood flow (CBF),cerebral blood volume (CBV), intracranial pressure (ICP), and cerebralperfusion pressure (CPP). Methods.A dynamic cerebrovascular resistance(CVR) feedback loop adjusts automatically to maintain CBF within a range ofthe CPP and defines autoregulation. The model obtains physiologic parametersfrom a full-scale patient simulator. We assumed that oxygen demand andarterial partial pressure of carbon dioxide (CO₂ responsivity) arethe two major factors involved in determining CBF. In addition, our brainmodel increases oxygen extraction up to 70% once CBF becomes insufficient tosupport CMRO₂. The model was validated against data from theliterature. Results.The model's response varied less than 9%from the literature data. Similarly, based on correlation coefficients betweenthe brain model and experimental data, a good fit was obtained for curvesdescribing the relationship between CBF and PaCO₂ at a meanarterial blood pressure of 150 mm Hg (R² = 0.92) and 100 mm Hg(R² = 0.70). Discussion.The autoregulated brain model, withincorporated CO₂ responsivity and a variable oxygen extraction,automatically produces changes in CVR, CBF, CBV, and ICP consistent withliterature reports, when run concurrently with a METI full-scale patientsimulator (Medical Education Technologies, Inc., Sarasota, Florida). Once themodel is enhanced to include herniation, vasospasm, and drug effects, itsutility will be expanded beyond demonstrating only basic neuroanesthesiaconcepts.     

An experimental randomized study of six different ventilatory modes in a piglet model with normal lungs

A randomized study of 6 ventilatory modes was made in 7 piglets with normal lungs. Using a Servo HFV 970 (prototype system) and a Servo ventilator 900 C the ventilatory modes examined were as follows: SV-20V, i.e. volume-controlled intermittent positive-pressure ventilation (IPPV); SV-20VIosc, i.e. volume-controlled ventilation (IPPV) with superimposed inspiratory oscillations; and SV-20VEf, i.e. volume-controlled ventilation (IPPV) with expiratory flush of fresh gas; HFV-60 denotes low-compressive high-frequency positive-pressure ventilation (HFPPV) and HVF-20 denotes low-compressive volume-controlled intermittent positive-pressure ventilation; and SV-20P denotes pressure-controlled intermittent positive-pressure ventilation. With all modes of ventilation a PEEP of 7.5 cm H₂O was used. In the abbreviations used, the number denotes the ventilatory frequency in breaths per minute (bpm). HFV indicates that all gas was delivered via the HFV 970 unit. The ventilatory modes described above were applied randomly for at least 30 min, aiming for a normoventilatory steady state. The HFV-60 and the HFV-20 modes gave lower peak airway pressures, 12–13 cm H₂O compared to approximately 17 cm H₂O for the other ventilatory modes. Also the mean airway pressures were lower with the HFV modes 8–9 cm H₂O compared to 11–14 cm H₂O for the other modes. The gas distibution was evaluated by N₂ washout and a modified lung clearance index. All modes showed N₂ wash-out according to a two-compartment model. The SV-20P mode had the fastest wash-out, but the HFV-60 and HFV-20 ventilatory modes also showed a faster N₂ wash-out than the others. Regarding the lung clearance index, the SV-20P, HFV-60 and HFV-20 modes showed better indices than the other modes. No relationship was found between the ventilatory mode and extravascular lung water, and there were no differences in the hemodynamic variables.This study was supported by the Swedish Medical Research Council (project 4252), Sweden     

Complementary Roles for Scavenger Receptor A and CD36 of Human Monocyte–derived Macrophages in Adhesion to Surfaces Coated with Oxidized Low-Density Lipoproteins and in Secretion of H2O2

Oxidized low-density lipoprotein (oxLDL) is considered one of the principal effectors of atherogenesis. To explore mechanisms by which oxLDL affects human mononuclear phagocytes, we incubated these cells in medium containing oxLDL, acetylated LDL (acLDL), or native LDL, or on surfaces coated with these native and modified lipoproteins. The presence of soluble oxLDL, acLDL, or native LDL in the medium did not stimulate H₂O₂ secretion by macrophages. In contrast, macrophages adherent to surfaces coated with oxLDL secreted three- to fourfold more H₂O₂ than macrophages adherent to surfaces coated with acLDL or native LDL. Freshly isolated blood monocytes secreted little H₂O₂ regardless of the substrate on which they were plated. H₂O₂ secretion was maximal in cells maintained for 4–6 d in culture before plating on oxLDL-coated surfaces. Fucoidan, a known ligand of class A macrophage scavenger receptors (MSR-A), significantly reduced macrophage adhesion to surfaces coated with oxLDL or acLDL. Monoclonal antibody SMO, which blocks oxLDL binding to CD36, did not inhibit adhesion of macrophages to oxLDL-coated surfaces but markedly reduced H₂O₂ secretion by these cells. These studies show that MSR-A is primarily responsible for adhesion of macrophages to oxLDL-coated surfaces, that CD36 signals H₂O₂ secretion by macrophages adherent to these surfaces, and that substrate-bound, but not soluble, oxLDL stimulates H₂O₂ secretion by macrophages.     

Effects of recombinant-hemoglobin solutions rHb2.0 and rHb1.1 on blood pressure, intestinal blood flow, and gut oxygenation in a rat model of hemorrhagic shock

The vasoconstriction induced by hemoglobin-based oxygen carriers (HBOCs), mainly a result of nitric oxide (NO) scavenging, until now has limited the application of HBOCs as resuscitation fluids. In this study, we tested the hypothesis that the new modified recombinant-hemoglobin solution rHb2.0, with a 20 to 30 times lesser NO-scavenging rate, would minimize vasoconstriction without adverse effects on microvascular oxygenation. Responses were compared with those to rHb1.1, a recombinant-hemoglobin solution with a wild-type NO-scavenging rate, as well as an oncotically matched albumin solution. In a fixed-pressure (40 mm Hg) rat model of hemorrhagic shock and resuscitation, rHb2.0 and albumin both restored mean arterial pressure (MAP) to baseline values, whereas rHb1.1 increased MAP to 27% above the baseline value. Mesenteric vascular resistance after resuscitation with rHb2.0 was 57% less than that with rHb1.1. rHb2.0 was found to have 55% greater intestinal oxygen delivery (Do2int ) and resulted in a 27% lower oxygen-extraction rate than did rHb1.1 after resuscitation. Intestinal microvascular Po2 , determined on the basis of oxygen-dependent quenching of palladium-porphyrin phosphorescence, revealed no difference between rHb2.0 and rHb1.1. The findings of this study confirm that the well-known pressure effect of HBOCs is caused by their effect on the NO-scavenging rate; recombinant modification of this rate did not increase MAP during resuscitation compared with baseline values. Although systemic vasoconstriction was absent, intestinal vasoconstriction almost negligible, and Do2int greater after resuscitation with rHb2.0, the effect of rHb2.0 on pH, base-excess and microvascular Po2 levels after resuscitation were comparable to those achieved with the use of the albumin solution.     

Levosimendan improves postresuscitation outcomes in a rat model of CPR

In this study we sought to determine whether a calcium sensitizer, levosimendan, would have a more favorable effect on postresuscitation myocardial function and, consequently, postresuscitation survival than beta-adrenergic dobutamine. The extreme decrease in survival before hospital discharge of resuscitated victims is attributed, in part, to postresuscitation myocardial failure, and dobutamine has been recommended for the management of postresuscitation myocardial failure. We studied a total of 15 animals. Ventricular fibrillation was induced in Sprague-Dawley rats weighing 450 to 550 g. Cardiopulmonary resuscitation (CPR), including chest compressions and mechanical ventilation, was begun after 8 minutes of untreated cardiac arrest. Electrical defibrillation was attempted after 6 minutes of CPR. Each animal was resuscitated. Animals were randomized to undergo treatment with levosimendan, dobutamine, or saline-solution placebo. These agents were administered 10 minutes after the return of spontaneous circulation. Levosimendan was administered in a loading dose of 12 microg kg(-1) over a 10-minute period, followed by infusion of 0.3 microg kg(-1) min(-1) over the next 230 minutes. Dobutamine was continuously infused at a dosage of 3 microg kg(-1) min(-1). Saline-solution placebo was administered in the same volume and over the same amount of time as levosimendan. Levosimendan and dobutamine produced comparable increases in cardiac output and rate of left-ventricular pressure increase. However, administration of levosimendan resulted in lower heart rates and lesser increases in left ventricular diastolic pressure compared with both dobutamine and placebo. The duration of postresuscitation survival was significantly greater with levosimendan (16 +/- 2 hours), intermediate with dobutamine (11 +/- 2 hours) and least with saline-solution placebo (8 +/- 1 hour). Levosimendan and dobutamine both improved postresuscitation myocardial function. However, levosimendan produced more favorable postresuscitation myocardial function and increased the duration of postresuscitation survival.     

PLGA/chitosan composites from a combination of spray drying and supercritical fluid foaming techniques: New carriers for DNA delivery

The use of poly(_{D, L}-lactic-co-glycolic acid) for DNA delivery application is limited by its negative surface charge and acidic degradation products. The motivation of the present work was to study the effects of chitosan incorporation into PLGA foams on DNA delivery. PLGA/chitosan composite foams loaded with luciferase plasmid were fabricated by a combination of spray drying and supercritical CO₂ foaming techniques. The resultant composite foams showed good morphology and chitosan was found to be poorly crystallized in the PLGA matrixes. The composite foams exhibited a sustained release of DNA (5–9weeks) with decreasing release rate upon increasing content of chitosan. With this encapsulation technique, it was also observed that the integrity of plasmid was well maintained. Moreover, cell culture results proved that the bioactivity of plasmid released from all foams was well maintained and the incorporation of chitosan in foams helps increase cell adhesion and maintain high cell viability. Therefore, it can be concluded that PLGA/chitosan composite foams fabricated by combining spray drying and supercritical CO₂ foaming are promising in DNA delivery applications.     

Evaluation of dexmedetomidine therapy for sedation in patients with toxicological events at an academic medical center

Introduction. Although clinical use of dexmedetomidine (DEX), an alpha₂-adrenergic receptor agonist, has increased, its role in patients admitted to intensive care units secondary to toxicological sequelae has not been well established. Objectives. The primary objective of this study was to describe clinical and adverse effects observed in poisoned patients receiving DEX for sedation. Methods. This was an observational case series with retrospective chart review of poisoned patients who received DEX for sedation at an academic medical center. The primary endpoint was incidence of adverse effects of DEX therapy including bradycardia, hypotension, seizures, and arrhythmias. For comparison, vital signs were collected hourly for the 5 h preceding the DEX therapy and every hour during DEX therapy until the therapy ended. Additional endpoints included therapy duration; time within target Richmond Agitation Sedation Score (RASS); and concomitant sedation, analgesia, and vasopressor requirements. Results. Twenty-two patients were included. Median initial and median DEX infusion rates were similar to the commonly used rates for sedation. Median heart rate was lower during the therapy (82 vs. 93 beats/minute, p < 0.05). Median systolic blood pressure before and during therapy was similar (111 vs. 109 mmHg, p = 0.745). Five patients experienced an adverse effect per study definitions during therapy. No additional adverse effects were noted. Median time within target RASS and duration of therapy was 6.5 and 44.5 h, respectively. Seventeen patients (77%) had concomitant use of other sedation and/or analgesia with four (23%) of these patients requiring additional agents after DEX initiation. Seven patients (32%) had concomitant vasopressor support with four (57%) of these patients requiring vasopressor support after DEX initiation. Conclusion. Common adverse effects of DEX were noted in this study. The requirement for vasopressor support during therapy warrants further investigation into the safety of DEX in poisoned patients. Larger, comparative studies need to be performed before the use of DEX can be routinely recommended in poisoned patients.     

Evaluation of the diagnostic value of fluorescent in situ hybridization in a rat model of bacterial pneumonia

In severe nosocomial pneumonia, the pathogenic responsibility of bacteria isolated from airways is far from certain, and a lung biopsy is sometimes performed. However, detection and identification of pathogens are frequently unachieved. Here, we developed a protocol for direct visualization of bacteria within the lung tissue using fluorescent in situ hybridization (FISH) in a rat model of Acinetobacter baumannii pneumonia. The reference positive diagnosis of bacterial pneumonia was the presence of pathological signs of pneumonia associated with the proof of bacteria or bacterial PCR products into the parenchyma. By analysis of 122 sets of slices from 26 rats and using the eubacterial probe EUB-338, our results show that FISH reached a sensitivity and a diagnostic accuracy higher than that of optic microscopy (sensitivity: 96% versus 55.4% and diagnostic accuracy: 96.7% versus 66.4%), whereas both approaches had 100% specificity. FISH could be useful especially on negative biopsies from patients with suspected infectious pneumonia.     

Brain tissue oxygen pressure and cerebral metabolism in an animal model of cardiac arrest and cardiopulmonary resuscitation

OBJECTIVE: Direct measurement of brain tissue oxygenation (PbtO2) is established during spontaneous circulation, but values of PbtO2 during and after cardiopulmonary resuscitation (CPR) are unknown. The purpose of this study was to investigate: (1) the time-course of PbtO2 in an established model of CPR, and (2) the changes of cerebral venous lactate and S-100B. METHODS: In 12 pigs (12-16 weeks, 35-45 kg), ventricular fibrillation (VF) was induced electrically during general anaesthesia. After 4 min of untreated VF, all animals were subjected to CPR (chest compression rate 100/min, FiO2 1.0) with vasopressor therapy after 7, 12, and 17 min (vasopressin 0.4, 0.4, and 0.8 U/kg, respectively). Defibrillation was performed after 22 min of cardiac arrest. After return of spontaneous circulation (ROSC), the pigs were observed for 1h. RESULTS: After initiation of VF, PbtO2 decreased compared to baseline (mean +/- SEM; 22 +/- 6 versus 2 +/- 1 mmHg after 4 min of VF; P < 0.05). During CPR, PbtO2 increased, and reached maximum values 8 min after start of CPR (25 +/- 7 mmHg; P < 0.05 versus no-flow). No further changes were seen until ROSC. Lactate, and S-100B increased during CPR compared to baseline (16 +/- 2 versus 85 +/- 8 mg/dl, and 0.46 +/- 0.05 versus 2.12 +/- 0.40 microg/l after 13 min of CPR, respectively; P < 0.001); lactate remained elevated, while S-100B returned to baseline after ROSC. CONCLUSIONS: Though PbtO2 returned to pre-arrest values during CPR, PbtO2 and cerebral lactate were lower than during post-arrest reperfusion with 100% oxygen, which reflected the cerebral low-flow state during CPR. The transient increase of S-100B may indicate a disturbance of the blood-brain-barrier.     

Proposal of a computerized algorithm for continuous wave CO2 laser on-line control during orthopaedic surgery. Phase I: Theoretical introduction and firstin vitro trials

New data obtained from treating polymethylmethacrylate (PMMA) with a non-moving cw- 10 watt-CO₂ laserbeam focused at 2.5, 5, 7.5 and 15.75 are presented. The final equations R(t_c) and Z(t_c) for each focal length are proposed. A very interesting correlation between the focal lengths in use and the integrated values of R and Z between 0 and 2 sec has been identified and discussed. This result has been used as basis to define a convenient operative protocol to follow during the planning phase of critical osteotomier or bone cement removal operations using a continuous-wave CO₂ laserbeam set to any output power and focused by a set of most common, moving or non-moving focal lengths placed on the operating area. With a simple equation, it is possible to compare craters obtained with moving and non-moving laserbeams at different operative conditions between 0 and 2 sec, time interval which covers the majority of cases. A value of 2.3±0.1 between ablated volumes of PMMA and bone tissue has been identified. Several case studies regarding orthopaedic procedures from Literature are here reported and compared to the present LCA^* model. The computerized on-line flow of information for the laserbeam optimization and safety control is also described. Finally, a method for the simultaneous data collection from several operating rooms via a Local Area Network (LAN-Industry Standard IEEE) onto a central data base for later consultation is proposed in its general design.     

Assessment of a new prototype hydrogel CO<Subscript><Emphasis Type="Bold">2</Emphasis></Subscript> sensor; comparison with air tonometry

Objective

Gastrointestinal ischemia is always accompanied by an increased luminal CO₂. Currently, air tonometry is used to measure luminal CO₂. To improve the response time a new sensor was developed, enabling continuous CO₂ measurement. It consists of a pH-sensitive hydrogel which swells and shrinks in response to luminal CO₂, which is measured by the pressure sensor. We evaluated the potential clinical value of the sensor during an in vitro and in vivo study.

Methods

The response time to immediate, and stepwise change in pCO₂ was determined between 5 and 15 kPa, as well as temperature sensitivity between 25 and 40 °C at two pCO₂ levels. Three sensors were compared to air tonometry (Tonocap^®) in healthy volunteers using a stepwise incremental exercise test, followed by a period of hyperventilation and an artificial CO₂-peak.

Results

The in vitro response time to CO₂ increase and decrease was mean 5.9 and 6.6 min. The bias, precision and reproducibility were +5%, 3% and 2%, resp. Increase of 1 °C at constant pCO₂ decreased sensor signal by 8%. In vivo tests: The relation with the Tonocap was poor during the exercise test. The response time of the sensor was 3 min during hyperventilation and the CO₂ peak.

Conclusion

The hydrogel carbon dioxide sensor enabled fast and accurate pCO₂ measurement in a controlled environment but is very temperature dependent. The current prototype hydrogel sensor is still too unstable for clinical use, and should therefore be improved.

     

Quantitative evaluation of changes in binding potential with a simplified reference tissue model and multiple injections of [C]raclopride

Positron emission tomography (PET) with [¹¹C]raclopride is widely used to investigate temporal changes in the dopamine D₂ receptor system attributed to the dopamine release. The simplified reference tissue model (SRTM) can be used to determine the binding potential (BP_ND) value using the time–activity curve (TAC) of the reference region as input function. However, in assessing temporal changes in BP_ND using the SRTM, multiple [¹¹C]raclopride PET scans are required, and a second scan must be performed after the disappearance of the [¹¹C]raclopride administered in the first scan. In this study, we have developed an extended multiple-injection SRTM to estimate the BP_ND change, from a single PET scan with multiple injections of [¹¹C]raclopride, and we have validated this approach by performing numerous simulations and studies on monkeys. In the computer simulations, TACs were generated for dual injections of [¹¹C]raclopride, in which binding conditions changed during the scans, and the BP_ND values before, and after, the second injection were estimated by the proposed method. As a result, the reduction in BP_ND was correlated, either with the integral of released dopamine, or with the administered mass of raclopride. This method was applied to studies on monkeys, and was capable of determining two identical BP_ND values when there were no changes in binding conditions. The BP_ND after the second injection decreased when binding conditions changed due to an increase in administered raclopride. An advantage of the proposed method is the shortened scan period for the quantitative assessment of the BP_ND change for neurotransmitter competition studies.     

Effectiveness of sepsis bundle application in cirrhotic patients with septic shock: a single-center experience

Purpose

To evaluate the effect of adherence to evidence-based guidelines of the Surviving Sepsis Campaign (SSC) on the outcome of cirrhotic patients with septic shock admitted to the intensive care unit.

Methods

This prospective observational cohort study included 38 patients with documented liver cirrhosis and septic shock admitted to a multidisciplinary intensive care unit at a University Hospital from January 2005 to June 2009. In each patient, the compliance to 4 resuscitation (ie, 6-hour bundle) and to 3 management (i.e. 24-hour bundle) interventions recommended by the SSC guidelines and the 30-day mortality were measured.

Results

The 6-hour, 24-hour, and all bundles were completed in 50 %, 52%, and 39% of the patients, respectively. The characteristics at admission and the 30-day mortality of patients with all-bundle compliance (n = 15; mortality 86.6%) were similar to those of patients without bundle compliance (n = 23; mortality 78.2%), except for central venous O₂ saturation. Unadjusted and adjusted regression analysis showed that none of the single sepsis interventions and bundles were independently associated with 30-day mortality.

Conclusions

In our observational study, the adherence to the interventions recommended by the SSC evidence-based guidelines did not provide an improvement in the survival rate of cirrhotic patients with septic shock.