Prescribing nonopioids in mechanically ventilated critically ill patients

PURPOSE

We searched for factors independently associated with the prescription of multimodal (balanced) analgesia in mechanically ventilated critically ill patients.

METHODS

In this post hoc analysis of a cohort study, 172 patients who received a combination of 1 opioid with nonopioids, that is, paracetamol and/or nefopam, (multimodal analgesia), were compared with 302 patients who received opioid only on day 2 of their stay in the intensive care unit.

RESULTS

Patients given multimodal analgesia were more likely to have fewer organ failures and received fewer hypnotics compared with patients who received opioid only. They self-reported more frequently their pain level. There were no differences in the daily dose of opioids between the 2 groups. A low illness severity score, no more than 1 organ failure on day 2, the ability to self-rate pain, and a moderate-to-severe pain rated on day 2 were factors independently associated with the prescription of multimodal analgesia on day 2 (all P < .01).

CONCLUSIONS

In mechanically ventilated patients, the addition of nonopioids to opioids is mostly prescribed for patients with lower illness severity scores and who are able to self-rate their pain intensity. These findings suggest that the concept of multimodal analgesia must be promoted in the intensive care unit.

Colistin in critically ill patients

Colistin is a re-emerging old antibiotic that is used as a salvage treatment against multidrug-resistant Gram-negative infections. Because it is administrated as an inactive prodrug, colistin methanesulfonate (CMS) that undergoes rapid hydrolyze to colistin, pharmacokinetic studies using biological assays are unreliable. With the recent development of new assays using high performance liquid chromatography (HPLC) accurate pharmacokinetic of CMS and formed colistin is now available in various populations. This article aims to update previous reports on pharmacodynamics, pharmacokinetics, safety and clinical use of colistin, with a special focus on data useful to treat critically ill patients.

Randomized controlled trial of chlorhexidine dressing and highly adhesive dressing for preventing catheter-related infections in critically ill adults

RATIONALE

Most vascular catheter-related infections (CRIs) occur extraluminally in patients in the intensive care unit (ICU). Chlorhexidine-impregnated and strongly adherent dressings may decrease catheter colonization and CRI rates.

OBJECTIVES

To determine if chlorhexidine-impregnated and strongly adherent dressings decrease catheter colonization and CRI rates.

METHODS

In a 2:1:1 assessor-masked randomized trial in patients with vascular catheters inserted for an expected duration of 48 hours or more in 12 French ICUs, we compared chlorhexidine dressings, highly adhesive dressings, and standard dressings from May 2010 to July 2011. Coprimary endpoints were major CRI with or without catheter-related bloodstream infection (CR-BSI) with chlorhexidine versus nonchlorhexidine dressings and catheter colonization rate with highly adhesive nonchlorhexidine versus standard nonchlorhexidine dressings. Catheter-colonization, CR-BSIs, and skin reactions were secondary endpoints.

MEASUREMENTS AND MAIN RESULTS

A total of 1,879 patients (4,163 catheters and 34,339 catheter-days) were evaluated. With chlorhexidine dressings, the major-CRI rate was 67% lower (0.7 per 1,000 vs. 2.1 per 1,000 catheter-days; hazard ratio [HR], 0.328; 95% confidence interval [CI], 0.174-0.619; P = 0.0006) and the CR-BSI rate 60% lower (0.5 per 1,000 vs. 1.3 per 1,000 catheter-days; HR, 0.402; 95% CI, 0.186-0.868; P = 0.02) than with nonchlorhexidine dressings; decreases were noted in catheter colonization and skin colonization rates at catheter removal. The contact dermatitis rate was 1.1% with and 0.29% without chlorhexidine. Highly adhesive dressings decreased the detachment rate to 64.3% versus 71.9% (P < 0.0001) and the number of dressings per catheter to two (one to four) versus three (one to five) (P < 0.0001) but increased skin colonization (P < 0.0001) and catheter colonization (HR, 1.650; 95% CI, 1.21-2.26; P = 0.0016) without influencing CRI or CR-BSI rates.

CONCLUSIONS

A large randomized trial demonstrated that chlorhexidine-gel-impregnated dressings decreased the CRI rate in patients in the ICU with intravascular catheters. Highly adhesive dressings decreased dressing detachment but increased skin and catheter colonization. Clinical trial registered with www.clinicaltrials.gov (NCT 01189682).

Benefits of an early cooling phase in continuous renal replacement therapy for ICU patients

Background

Lowering the temperature setting in the heating device during continuous venovenous hemofiltration (CVVH) is an option. The purpose of this study was to determine the effects on body temperature and hemodynamic tolerance of two different temperature settings in the warming device in patients treated with CVVH.

Methods

Thirty patients (mean age: 66.5 years; mean SAPS 2: 55) were enrolled in a prospective crossover randomized study. After a baseline of 2 h at 38°C, the heating device was randomly set to 38°C (group A) and 36°C (group B) for 6 h. Then, the temperatures were switched to 36°C in group A and to 38°C in group B for another 6 h. Hemodynamic parameters and therapeutic interventions to control the hemodynamics were recorded.

Results

There was no significant change in body temperature in either group. During the first 6 h, group B patients showed significantly increased arterial pressure (p = 0.01) while the dosage of catecholamine was significantly decreased (p = 0.04). The number of patients who required fluid infusion or increase in catecholamine dosage was similar. During the second period of the study, hemodynamic parameters were unchanged in both groups.

Conclusions

In patients undergoing CVVH, warming of the substitute over 36°C had no impact on body temperature. We showed that setting the fluid temperature at 36°C for a period of time early in the procedure is beneficial in terms of increased mean arterial pressure and decreased catecholamine infusion dosage.

Risk factors and outcomes for prolonged versus brief fever: a prospective cohort study

INTRODUCTION

Prolonged fever occurs with infectious and noninfectious diseases but is poorly studied in intensive care units. The aims of this prospective multicenter noninterventional study were to determine the incidence and etiologies of prolonged fever in critically ill patients and to compare outcomes for prolonged fever and short-lasting fever.

METHODS

The study involved two periods of 2 months each, with 507 patients hospitalized ≥ 24 hours. Fever was defined by at least one episode of temperature ≥ 38.3 °C, and prolonged fever, as lasting > 5 days. Backward stepwise logistic regression was performed to identify the independent factors associated with prolonged fever versus short-lasting fever.

RESULTS

Prolonged or short-lasting fever occurred in 87 (17%) and 278 (55%) patients, respectively. Infectious and noninfectious causes were found in 54 (62%) and 27 (31%) of 87 patients, respectively; in six patients (7%), prolonged fever remained unexplained. The two most common sites of infection were ventilator-associated pneumonia (n = 25) and intraabdominal infection (n = 13). Noninfectious fever (n = 27) was neurogenic in 19 (70%) patients and mainly associated with cerebral injury (84%). Independent risk factors for prolonged fever were cerebral injury at admission (OR = 5.03; 95% CI, 2.51 to 10.06), severe sepsis (OR = 2.79; 95% CI, 1.35 to 5.79), number of infections (OR = 2.35; 95% CI, 1.43 to 3.86), and mechanical-ventilation duration (OR = 1.05; 95% CI, 1.01 to 1.09). Older patients were less likely to develop prolonged fever. ICU mortality did not differ between the two groups.

CONCLUSIONS

Prolonged fever was common, mainly due to severe infections, particularly ventilator-associated pneumonia, and mixed infectious causes were frequent, warranting systematic and careful search for multiple causes. Neurogenic fever was also especially frequent.

Animal model methodology: immunocompetent or leucopenic rats, which is the best? Results from a model of experimental pneumonia due to derepressed cephalosporinase-producing Enterobacter cloacae

BACKGROUND

The aim of this study was to compare the bactericidal activity of cefepime plus amikacin against experimental pneumonia induced by a stably derepressed cephalosporinase-producing Enterobacter cloacae strain in immunocompetent and leucopenic rats.

METHODS

Sixty Wistar rats were used. Leucopenia was induced in half of them by a single intravenous administration of 30 mg/kg cyclophosphamide, while the remaining rats received the same volume of saline. All rats were infected 96 h later by tracheal instillation of 8 log(10) colony-forming units of E. cloacae. Twelve rats (6 immunocompetent and 6 leucopenic) were sacrificed 6 h later to assess the initial bacterial burden to the lungs. Then, the remaining 48 rats received a combination of 60 mg/kg cefepime twice a day and 25 mg/kg amikacin once a day given intraperitoneally or the same volume of saline. Six rats per group (leucopenic or not, treated or not) were sacrificed 12 and 30 h after therapy started.

RESULTS

Spontaneous bacterial clearance with time was observed only in immunocompetent rats. Compared to untreated animals, antibiotic administration induced a decrease in lung bacterial titres in immunocompetent and leucopenic rats. The difference was statistically significant only in leucopenic rats.

CONCLUSIONS

The use of leucopenic rats reduced spontaneous bacterial clearance in the lungs and increased the bactericidal effect of the antibiotic combination and ultimately the confidence in the reliability of the results.

Accuracy of respiratory rate monitoring using a non-invasive acoustic method after general anaesthesia

BACKGROUND

Respiratory rate should be monitored continuously in the post-anaesthesia care unit (PACU) to avoid any delay in the detection of respiratory depression. Capnometry is the standard of care but in extubated patients requires a nasal cannula or a face mask that may be poorly tolerated or can be dislodged, leading to errors in data acquisition and false alarms. The value of a new non-invasive acoustic monitor in this setting has not been fully investigated.

METHODS

Adult patients admitted to the PACU after general anaesthesia were included. After tracheal extubation, an adhesive sensor with an integrated acoustic transducer (RRa™) was placed on the patient's throat and connected to its monitor while the patient breathed through a face mask with a carbon dioxide sampling port (Capnomask™) connected to a capnometer. Both the acoustic monitor and the capnometer were connected to a computer to record one pair of data per second for up to 60 min.

RESULTS

Fifty-two patients, mean (range) age 54 (22-84) yr and BMI 26 (19-39) kg m(-2), were studied. Compared with capnometry, the bias and limits of agreement of the acoustic method were 0 (-1.4-1.4) bpm. The acoustic sensor was well tolerated while the face mask was removed by eight patients, leading to study discontinuation in two patients.

CONCLUSIONS

In extubated patients, continuous assessment of respiration rate with an acoustic monitor correlated well with capnometry.

How to solve the problem of spontaneous bacterial clearance when testing new antibiotic treatment: results on experimental pneumonia due to a derepressed cephalosporinase-producing Enterobacter cloacae

Because the magnitude of spontaneous bacterial clearance can be similar or even higher than treatment effect, depending upon experimental model and bacterial strain used, this work investigated the value of rendering rats immunosuppressed to facilitate bacterial implantation and reduce spontaneous bacterial clearance. In a first step, rats received a single intravenous cyclophosphamide dose 4 days before infection. Three different doses were tested: 10, 20, and 40 mg/kg. After modeling with NONMEM V, the cyclophosphamide dose required to maintain white blood cell count <1.0 × 10(3)/μL from day 4 to day 5 was 30 mg/kg. In a second step, influence of immunosuppression on lung bacterial titers was characterized. Rats were given one of the three intravenous cyclophosphamide doses (0, 10, 30 mg/kg), and after 4 days, they were infected by tracheal injection of 8.9 ± 0.1 log10 cfu Enterobacter cloacae before being sacrificed at different times. Bacteria in homogenized lungs were quantitatively cultured on Drigalski agar. Bacterial lung count was closely influenced by the grade of induced leukopenia. A single intravenous 30 mg/kg cyclophosphamide dose 4 days before infection suppressed the spontaneous clearance of E. cloacae for at least 30 h without significantly increasing animal mortality; this result seems to be linked to a white blood cell count maintained lower than 1.0 × 10(3)/μL for all the time. This modified animal model could be contributive in the evaluation of antibacterial agents, especially to simulate the behavior of intensive care unit immunocompromised patients.

Accuracy of respiratory rate monitoring by capnometry using the Capnomask(R) in extubated patients receiving supplemental oxygen after surgery

BACKGROUND

Respiratory monitoring is standard after anaesthesia and surgery. Abnormal respiratory rate is a sensitive indicator of respiratory problems, even in patients receiving supplemental oxygen, but the best method for its continuous measurement in spontaneously breathing patients is unclear. This study compared respiratory rate assessment by capnometry using a new oxygen mask with a carbon dioxide sampling port (Capnomask(®)) and thoracic impedance pneumography with clinical measurement (used as a reference method) in extubated patients receiving supplemental oxygen.

METHODS

Adult males admitted to the post-anaesthesia care unit after general anaesthesia were studied. Immediately after extubation, a Capnomask(®) connected to a capnometer was positioned appropriately. Respiratory rate was measured by visual inspection of chest movement for 1 min, by capnometry, and thoracic impedance pneumography. One set of measurements was obtained for every patient receiving supplemental oxygen at different flow rates.

RESULTS

Twenty men, mean (inter-quartile range) age 54 (23-66) yr and BMI 25 (21-31) kg m(-2), were studied. Compared with visual inspection, the bias and limits of agreement were 0.0 (1.0 to -1.0) bpm for the Capnomask(®) and -2.2 (2.0 to -6.5) bpm for the impedance pneumography. The accuracy of respiratory rate assessment using Capnomask(®) was not influenced by the supplemental oxygen flow rate.

CONCLUSIONS

In extubated patients, continuous assessment of respiratory rate with the Capnomask(®) is more accurate than by thoracic impedance pneumography even when supplemental oxygen is delivered at a high flow rate.

Reliability of the HemoCue® hemoglobinometer in critically ill patients: a prospective observational study

BACKGROUND

The aim of the study was to assess the reliability of hemoglobin measurements made with HemoCue®, compared with those made with the reference method in critically ill patients.

METHODS

A prospective observational study was conducted in three adult surgical intensive care units of a university hospital. One hundred and ninety-eight consecutive patients were included, and a total of 1166 hemoglobin concentrations were measured using arterial blood samples in the laboratory (HbLAB) and at bedside (HbHC.art) with a portable hemoglobinometer (HemoCue® Hb201+). Simultaneously, a capillary measurement (HbHC.cap) was performed at bedside using the same device.

RESULTS

The mean difference (bias) between HbHC.cap and HbLAB was 0.2 g/dL (95%CI, 0.1;0.3), and limits of agreement were -1.3 g/dL (95%CI, -1.4;-1.2) to 1.7 g/dL (95%CI, 1.6;1.9). The discrepancies between HbHC.cap and HbLAB were greater than 1 g/dL in 30.8% of cases. The bias between HbHC.art and HbLAB was -0.1 g/dL (95% CI, -0.2;0.2), and limits of agreement were slightly better at -1.1 g/dL (95% CI, -1.2;-1.0) and 1.0 g/dL (95% CI, 0.9;1.1). The HemoCue®'s accuracy was not affected by the hospital unit, the puncture site (finger or ear), norepinephrine administration or by hemoglobin levels below 10 g/dL or 8 g/dL.

CONCLUSION

Capillary HemoCue® is not sufficiently accurate to make a therapeutic decision such as whether a blood transfusion should be performed. The method's performance was moderately improved by the use of arterial blood.

Kinetics of imipenem distribution into the peritoneal fluid of patients with severe peritonitis studied by microdialysis

BACKGROUND AND OBJECTIVES

A microdialysis study of meropenem distribution in the peritoneal fluid of patients with peritonitis has suggested that there is significant peripheral drug degradation. The aims of the present study were to investigate the plasma and peritoneal fluid pharmacokinetics of imipenem, a relatively unstable antibacterial, in patients with severe peritonitis, and to relate measured unbound concentrations to the minimum inhibitory concentrations required for susceptible and intermediately susceptible bacteria.

METHODS

Microdialysis catheters were placed into the peritoneal cavity through peritoneal drains in nine critically patients. Imipenem concentrations in plasma and in peritoneal fluid were analysed using compartmental modelling.

RESULTS

A model that considered elimination from a peripheral compartment described the data and was used to simulate steady-state concentration profiles in plasma and peritoneal fluid during various dosing regimens. Using recommended dosing regimens (500 mg every 6 hours, 1000 mg every 8 hours and 1000 mg every 6 hours), simulated unbound peritoneal fluid concentrations of imipenem in patients with severe peritonitis reached values sufficient for antibacterial effects against susceptible bacteria. However, the adequacy of regimens in patients with severe peritonitis whose infections involve intermediately susceptible bacteria is questionable.

CONCLUSION

The results of this study are consistent with those previously observed with meropenem and confirm the usefulness of microdialysis for assessment of peritoneal fluid distribution of antibacterials.

Nefopam pharmacokinetics in patients with end-stage renal disease

BACKGROUND

Treatment of intense postoperative pain in patients with end-stage renal disease (ESRD) is a recurrent problem for anesthesiologists because of the risk of accumulation of numerous molecules and their metabolites. Nefopam is a potent analgesic metabolized by the liver and weakly eliminated intact in urine that may offer advantages for use in patients with ESRD because it lacks respiratory-depressive effects. However, the effects of renal failure on nefopam disposition have never been investigated.

METHODS

We studied 12 ESRD patients (creatinine clearance < 20 mL/min, mean age 57 ± 13 years) having surgery under general anesthesia to create or repair an arteriovenous fistula. Postoperatively, after complete recovery from anesthesia, each patient received a single 20-mg dose of nefopam IV over 30 minutes. Nefopam and desmethyl-nefopam concentrations in plasma samples obtained over 48 hours were determined by liquid chromatography-tandem mass spectrometry. The pharmacokinetic parameter values obtained were compared with those of 12 healthy 50- to 60-year-old volunteers who also received a single 20-mg nefopam infusion over 30 minutes using a population pharmacokinetic approach.

RESULTS

Healthy volunteers and ESRD patients had comparable demographic characteristics. In comparison with those volunteers, ESRD patients had a lower volume of central compartment (115 and 53 L vs. 264 L for patients not yet hemodialyzed and on chronic hemodialysis, respectively; P < 0.001) and lower mean nefopam clearance (37.0 and 27.3 L/h vs. 52.9 L/h, P < 0.001), resulting in higher mean nefopam peak concentration (121 and 223 ng/mL vs. 61 ng/mL, P < 0.001).

CONCLUSIONS

Nefopam distribution and elimination are altered in patients with ESRD, resulting in heightened exposure. To avoid too-high concentration peaks, it is suggested that the daily nefopam dose be reduced by 50%.

[Practice assessment of central venous lines care in surgical ICU of French university hospitals]

INTRODUCTION

Recommendations on insertion and maintenance of central venous catheters (CVC) in intensive care unit (ICU) patients were updated in 2002. The aim of this study was to estimate their knowledge and/or application by physicians in French university hospital ICUs.

METHODS

Two forms were sent to 124 professors of anaesthesia and intensive care encouraging them to participate to the survey. The first one was completed by the physician in charge of each unit and concerned the structure and activity of the unit in 2006. The second one was filled by each junior or senior physician working in the units and asked for experience, CVC insertion modalities and knowledge of CVC care protocols.

RESULTS

Forty-one (75 %) university hospitals with at least one adult surgical ICU took part to the study. A questionnaire was filled by 124 senior (75 % of the staff) and 53 junior (43 % of the staff) physicians inserting an average of 10 CVC per month (range, 1-35). A written protocol for CVC insertion was known by 127 (72 %) of them. CVC insertion was done while wearing sterile gown (97 %), cap (100 %) and surgical mask (100 %) and using large sterile drapes (96 %). The antiseptic solution used for cutaneous antisepsis was povidone iodine in aqueous (36 %) or alcoholic solution (40 %), or an alcoholic solution of chlorhexidine (24 %) applied one (9 %), two (64 %) or three (27 %) times before insertion. A 4-times disinfection sequence (washing, rinsing, drying and disinfection) was performed by 161 (91 %) physicians. Ultrasound-guided insertion was realized by only eight (5 %) operators. CVCs were made of polyurethane (84 %), usually multi-lumens (>96 %) and rarely tunnelised (14 %). Only two physicians (1 %) sometimes use catheters coated with antibiotics or antiseptics. The site for catheter insertion was mostly the sub-clavian (47 %) or internal jugular vein (34 %), and rarely the femoral vein (20 %). CVCs were secured with a thread (99 %) and covered with a semi-permeable dressing (76 %). Concerning CVCs maintenance, 91 % of physicians acknowledged the existence of a written protocol in the unit. Dressings were changed every day (10 %), every two days (49 %), every three days (29 %) or every four days or more (12 %) by using the same antiseptic solution and semi-permeable transparent dressing in 78 % of cases. Venous lines changes were done during dressing maintenance (48 %), every day in case of administration of lipids (32 %) or just after administration of blood products via the catheter (32 %). Routine change of CVC was rarely recommended (11 %).

CONCLUSION

The high number of answers allows setting of a precise state of CVCs insertion practices in adult surgical ICUs. Recommendations for central venous catheter insertion and maintenance are not still known and\or applied.

A physiological model to evaluate drug kinetics in patients with hemorrhagic shock followed by fluid resuscitation. Application to amoxicillin-clavulanate

PURPOSE

To build a physiologically based pharmacokinetic model describing drug kinetics in interstitial fluid in case of hemorrhagic shock, and to propose a simple method to determine the subset of influential parameters that may be estimated with the data at hand.

METHODS

The model, which accounts for alterations of regional blood flows and body water distribution, was fitted to amoxicillin and clavulanate kinetic data, assessed in 12 trauma patients with hemorrhagic shock by comparison with 12 healthy volunteers. The predictions were the free concentrations of amoxicillin and clavulanate in 14 organs.

RESULTS

In all tissues of trauma patients, the rate of distribution was lower, but the steady-state level was higher than those in healthy participants. Blood volume was reduced by 25% and blood flow in organs other than lung, brain, and heart were reduced by 18%. Compared with healthy subjects, the time that free amoxicillin concentration remained above 8 mg/L in the interstitial fluid of trauma patients was higher in blood and muscles, and lower in the tendon compartment.

CONCLUSIONS

The results and predictions were consistent with the knowledge in this field. The model may be useful to optimize clinical trial designs and drug dosing regimens.

Application of basic pharmacokinetic concepts to analysis of microdialysis data: illustration with imipenem muscle distribution

BACKGROUND

Microdialysis studies of antibacterial tissue distribution in critically ill patients have sometimes led to results that were spectacular but inconsistent with basic pharmacokinetic concepts.

OBJECTIVE

To conduct a study of imipenem distribution in the muscle of healthy volunteers and critical care patients in order to compare real-life data with theory.

METHODS

Microdialysis catheters were placed into the quadriceps, and probe recoveries were determined individually in vivo using a retrodialysis-by-drug method. Unbound imipenem concentrations were determined by high-performance liquid chromatography in plasma ultrafiltrates and muscle dialysates, and submitted to noncompartmental pharmacokinetic analysis.

RESULTS

Individual unbound imipenem concentrations in plasma and muscle extracellular fluid were virtually superimposed at any time, both in healthy volunteers and in critical care patients.

CONCLUSION

These new results are not consistent with previously published data obtained in similar conditions by another group, but they are in agreement with results previously obtained in rats, as well as being consistent with basic pharmacokinetic concepts.

Influence of renal function on trough serum concentrations of piperacillin in intensive care unit patients

OBJECTIVE

To explore the effects of renal function estimated by measured creatinine clearance (Cl(CR)) on trough serum concentration (C(min)) of piperacillin given to critically ill patients.

DESIGN

Prospective observational study.

SETTING

An intensive care unit and research ward in a university hospital.

PATIENTS

Seventy critically ill patients, including 22 with severe trauma.

INTERVENTIONS

All subjects received an intravenous infusion of piperacillin 4 g three times (n = 61) or four times (n = 9) per day. Piperacillin C(min) values were determined 24 h after treatment started and compared to the French breakpoint defining antibiotic susceptibility against Enterobacteriaceae (8 mg/l) or Pseudomonas sp. (16 mg/l).

RESULTS

Median (range) piperacillin C(min) was 11.9 (< 1-156.3) mg/l, with a great variability among patients. Although the median value was close to the breakpoints, sub-therapeutic plasma levels were frequently observed. Piperacillin C(min) was lower than the breakpoint for Enterobacteriaceae in 37% of patients, and lower than the breakpoint for P. aeruginosa in 67% of them. A strong relationship was observed between piperacillin C(min) and Cl(CR): the higher the Cl(CR,) the lower the piperacillin C(min )in serum. For patients with a Cl(CR) < 50 ml/min, enough piperacillin C(min) was achieved in most patients with 12 g piperacillin per day. For patients with higher Cl(CR) values, a piperacillin daily dose of 16 g or more may be warranted.

CONCLUSIONS

In critically ill patients, therapeutic monitoring must be part of the routine, and knowledge of Cl(CR) value may be useful for the choice of adequate initial piperacillin dosing.

Microdialysis study of imipenem distribution in skeletal muscle and lung extracellular fluids of Acinetobacter baumannii-infected rats

The aim of this study was to investigate imipenem distribution in muscle and lung interstitial fluids of rats with Acinetobacter baumannii pulmonary infection. By combining microdialysis in blood and tissues, it was possible to demonstrate that free imipenem concentrations were virtually identical in blood, muscle, and lung.

Microdialysis study of imipenem distribution in the intraperitoneal fluid of rats with or without experimental peritonitis

The purpose of this study was to extend the use of microdialysis to the investigation of antibiotic distribution into the intraperitoneal fluid of rats with or without peritonitis. Microdialysis probes were inserted into the jugular vein and peritoneal cavity of control rats or rats with intra-abdominal sepsis (n = 8 in each group) induced by cecal ligation and punctures. Imipenem (IPM) probe recoveries were determined in each rat by retrodialysis by drug. IPM was infused intravenously at a dose of 30 mg . kg(-1) over 30 min, microdialysis samples were collected for 120 min, and IPM concentrations were determined by high-performance liquid chromatography. Intraperitoneal infection had no statistically significant effect on IPM clearance (11.9 +/- 2.3 ml.min(-1).kg(-1) in control rats versus 10.9 +/- 2.1 ml.min(-1).kg(-1) in rats with peritonitis) or the volume of distribution (296 +/- 47 ml.kg(-1) in control rats versus 310 +/- 49 ml.kg(-1) in rats with peritonitis). IPM concentration profiles in intraperitoneal fluid and blood were virtually superimposed in control rats, whereas in infected animals, the mean intraperitoneal IPM concentrations were apparently slightly lower than corresponding blood levels. However, the areas under the concentration-versus-time curve estimated in intraperitoneal fluid and blood were not significantly different in both groups, with the corresponding ratios close to unity (1.01 +/- 0.19 and 0.89 +/- 0.28 in control rats and rats with peritonitis, respectively). In conclusion, IPM distribution in intraperitoneal fluid is rapid and complete both in control rats and in rats with peritonitis.

Steady-state trough serum and epithelial lining fluid concentrations of teicoplanin 12 mg/kg per day in patients with ventilator-associated pneumonia

OBJECTIVE

To determine the steady-state trough serum and epithelial lining fluid (ELF) concentrations of teicoplanin 12 mg/kg per day in critically ill patients with ventilator associated pneumonia.

DESIGN AND SETTING

Prospective, pharmacokinetic study in the surgical intensive care unit in a university hospital.

PATIENTS

Thirteen adult patients with nosocomial bacterial pneumonia on mechanical ventilation were enrolled.

INTERVENTIONS

All subjects received a 30-min intravenous infusion of 12 mg/kg teicoplanin every 12 h for 2 consecutive days followed by 12 mg/kg once daily. Teicoplanin concentrations in serum and ELF were determined simultaneously 4-6 days after antibiotic administration started.

MEASUREMENTS AND RESULTS

The median total and free concentrations of teicoplanin in serum at trough were 15.9 microg/ml (range 8.8-29.9) and 3.7 (2.0-5.4), respectively. The concentration in ELF was 4.9 (2.0-11.8).

CONCLUSIONS

In critically ill patients with ventilator-associated pneumonia the administration of high teicoplanin doses is required to reach sufficient trough antibiotic concentrations in lung tissues at steady state. At that time trough-free concentrations of teicoplanin in serum and ELF are comparable.

Lack of effect of experimental hypovolemia on imipenem muscle distribution in rats assessed by microdialysis

The aim of this study was to investigate the influence of hypovolemia on the distribution of imipenem in muscle extracellular fluid determined by microdialysis in awake rats. Microdialysis probes were inserted into the jugular vein and hind leg muscle. Imipenem recoveries in muscle and blood were determined in each rat by retrodialysis by drug before drug administration. Hypovolemia was induced by removing 40% of the initial blood volume over 30 min. Imipenem was infused intravenously at a dose of 70 mg . kg(-1) over 30 min, and microdialysis samples were collected for 120 min from hypovolemic (n = 8) and control (n = 8) rats. The decay of the free concentrations in blood and muscle with time were monoexponential, and the concentration profiles in muscle and blood were virtually superimposed in both groups. Accordingly, the ratios of the area under the concentration-time curve (AUC) for tissue (muscle) to the AUC for blood were always virtually equal to 1. Hypovolemia induced a 23% decrease in the clearance (P < 0.05) of imipenem, with no statistically significant alteration of its volume of distribution. This study showed that imipenem elimination was altered in hypovolemic rats, probably due to decreased renal blood flow, but its distribution characteristics were not. In particular, free imipenem concentrations in blood and muscle were always virtually identical.