Determination of the minimum alveolar concentration for halothane, isoflurane and sevoflurane in the gerbil

The present work determined the minimum alveolar concentrations (MAC) of halothane, isoflurane and sevoflurane in adult female gerbils (n=24). Animals were placed in a chamber for anaesthetic induction before performing tracheal intubation. The tracheal tube was connected to a non-rebreathing circuit with minimal dead space. Body temperature, blood pressure, heart and respiratory rates and end-tidal volatile anaesthetic levels were measured continuously. MAC was determined using a standard noxious stimulus (tail-clamp). All experiments were performed at the same time of the day, body temperature was maintained constant and blood-gas analysis was performed to confirm that values were within normal limits. The mean+/-SD MAC values were 1.06+/-0.11% halothane (n=8), 1.55+/-0.08% isoflurane (n=8) and 2.90+/-0.12% sevoflurane (n=7). Cardiovascular parameters at 1xMAC did not differ significantly among anaesthetics but the respiratory rate was significantly higher in the halothane group than in the isoflurane and sevoflurane groups. The SpO2 values recorded throughout anaesthesia and the pH and partial oxygen pressure values determined at the end of the study did not differ among the studied anaesthetics at 1xMAC. These data suggest that the MAC for halogenated inhalant anaesthetics in gerbils is lower than the average MAC values obtained in rats and mice.

[Sedation in surgical procedures using regional anesthesia in adult patients: results of a survey of Spanish anesthesiologists]

OBJECTIVE

To analyze the frequency and methods of sedation used in the context of regional anesthesia in adults by means of a national survey.

MATERIAL AND METHODS

We carried out a survey of participants at the courses of an anesthesiology training organization (Fundación Europea de Enseñanza en Anestesiología), held in Spain in 2006. The survey questionnaires asked about indications for sedation used during surgery under regional anesthesia as well as the form of administration, follow-up, and complications.

RESULTS

A total of 375 questionnaires were sent out and 185 responses were received (49.3%). Sedation is always used to accompany regional anesthesia by 69.2% of the respondents; 13.5% of them discuss the technique to be used with the patient and come to an agreement. The same type of sedation, regardless of the regional block performed, is used by 49.2% of respondents, and 64.3% use a scale to evaluate the level of sedation. The most favored sedation technique is continuous infusion, followed by target controlled infusion and boluses on demand. The most commonly used technique is sedation with bolus injections. Sixty percent use a single agent and 38.9% use combinations. The most commonly reported adverse effects are variability of patient response (53.5%) and respiratory complications (27%). In cases of ineffective regional blockade, 49.2% of those surveyed switch to general anesthesia.

CONCLUSIONS

Sedation is very often used to complement regional anesthesia in adult patients. Even though continuous infusion is considered to be the most appropriate form of administration, the most commonly used form is injection of boluses. Sedation with a single drug is used more frequently than drug combinations. Variability of individual response is the complication most commonly reported by the respondents.

[Hemodynamic variability caused by pressure-volume plotting and alveolar recruitment maneuvers in patients with adult respiratory distress syndrome]

OBJECTIVES

The plotting of pressure-volume curves and the performance of alveolar recruitment maneuvers are common practices in the care of patients with adult respiratory distress syndrome (ARDS), even though potentially harmful hemodynamic effects are associated with sustaining a high intrathoracic pressure. Our aim was to analyze hemodynamic and ventilatory changes related to these 2 maneuvers and to assess the short-term effectiveness of recruitment.

PATIENTS AND METHODS

The patients had ARDS and were being monitored with a catheter connected to a PiCCO system. All measurements were taken in sinus rhythm and with adequate vascular filling. Values recorded during plotting of the quasistatic pressure-volume curve and the recruitment maneuver (sustained airway pressure of 40 cm H2O) were the cardiac index, mean arterial pressure, heart rate, systolic volume index, and oxygen saturation (SpO2). Blood gas measurements were recorded before the maneuvers and 15 minutes afterwards.

RESULTS

All parameters decreased significantly in the 14 patients studied. The mean (SD) maximum decreases, from which all patients recovered within 2 minutes, were as follows: cardiac index, 26% (16%); mean arterial pressure, 6% (6%); heart rate, 4% (5%), systolic volume index, 21% (15%); and SpO2, 3% (3%). Significant increases in PaO2 (7% [6%]) and the ratio of PaO2 to the fraction of inspired oxygen were recorded after the recruitment maneuver (P=.016 and P=.014, respectively), but the changes were not clinically significant.

CONCLUSIONS

The hemodynamic disturbances associated with the alveolar recruitment maneuver based on sustaining a high end-expiratory pressure and the minor improvement in oxygenation achieved as a result suggest that the routine use of that maneuver in ARDS patients is of questionable value.

[Bispectral index monitoring during intrahospital transport]

BACKGROUND AND OBJECTIVE

Risk of morbidity and mortality increases for critically ill patients during transfers within the hospital. Such patients often require sedation, and suboptimal sedation is associated with hypertension, tachycardia, and ventilator dyssynchrony. The aim of this study was to assess level of sedation as indicated by monitoring of the bispectral (BIS) index during intrahospital transport of critical patients.

PATIENTS AND METHODS

Thirty patients who required transport to the critical care unit within the hospital were studied prospectively. We recorded time in transport, the agent used for sedation and the dosage, the BIS index, mean arterial pressure (MAP), and heart rate before starting transport and upon arrival at the critical care unit. The data were recorded by an observer who was not assigned to patient care.

RESULTS

The mean (SD) transport time was 13.9 (4.2) minutes. Midazolam was used in 26 patients and propofol in 4. Ten patients were given a bolus dose of cisatracurium before transfer started. Significant increases were observed in the BIS index (from 47 to 78, (P < .001), MAP (from 73 to 91 mmHg, P < .001), and heart rate (from 72 to 97 beats/min, P < .001) between the moment of starting transport and arrival at the critical care unit. Changes in the BIS index correlated significantly with changes in heart rate (r = 0.418, P = .024) but not with changes in MAP (r = 0.249, P = .19).

CONCLUSIONS

Monitoring the BIS index during intrahospital transport of sedated, mechanically ventilated patients may be useful for detecting inadequate sedation.

New data on epizootiology and genetics of piroplasms based on sequences of small ribosomal subunit and cytochrome b genes

As a continuation of our studies on molecular epizootiology of piroplasmosis in Spain and other countries, we present in this contribution the finding of new hosts for some piroplasms, as well as information on their 18S rRNA gene sequences. Genetic data were complemented with sequences of apocytochrome b gene (whenever possible). The following conclusions were drawn from these molecular studies: Theileria annulata is capable of infecting dogs, since it was diagnosed in a symptomatic animal. According to cytochrome b sequences, isolates from cows and dog present slight differences. The same isolates showed, however, identical sequence in the 18S rRNA gene. This exemplifies well the usefulness of the mitochondrial gene for examining infra-specific variation. Babesia bovis is an occasional parasite of equines, since it was detected in two symptomatic horses. We found evidence of genetic polymorphism occurring in the 18S rRNA gene of Spanish T. equi-like and B. ovis isolates. B. bennetti from Spanish seagull is loosely related to B. ovis, and might represent a genetically distinct branch of babesids. A partial sequence of a cytochrome b pseudogene was obtained for the first time in Babesia canis rossi from South Africa. The pseudogene is distantly related to B. bigemina cytochrome b gene. These new findings confirm the ability of some piroplasms to infect multiple hosts, as well as the existence of a relatively wide genetic polymorphisms with respect to the cytochrome b gene. On the other hand, the existence of mtDNA-like pseudogenes of possible nuclear location in piroplasms is interesting due to their possible impact on molecular phylogeny studies.

Monitoring sedation in critically ill patients

BACKGROUND AND OBJECTIVE

Sedation is commonly required by critically ill patients and inadequate sedation may be hazardous. Traditionally, subjective scales have been used for monitoring sedation. Bispectral index has been proposed, although its utility in the intensive care unit is debated. Our aim was to evaluate the depth of sedation in intubated surgical critically ill patients by means of two sedation scales (Ramsay and Observer's Assessment of Alertness and Sedation) and bispectral index.

METHODS

Sedation was assessed prospectively in 50 postoperative intubated patients requiring at least 24 h of sedation (35 propofol, 15 midazolam/fentanyl), every 8 h for a 24 -h period. The bispectral index value recorded was the mean value obtained during a 10-min observation period, whenever the quality signal index was above 75% and the electromyographic signal was below 25%.

RESULTS

Most of the patients (78%) were oversedated (bispectral index < 60). The three sedation scores (global data) correlated significantly (P < 0.001). This correlation was lost in the midazolam group in which the patients were also significantly more sedated than the propofol group (P = 0.001). The correlation between the bispectral index and the scales in the midazolam group reappeared when the measurements with a Ramsay = 6 or an Observer's Assessment of Alertness and Sedation = 1 were excluded.

CONCLUSIONS

Sedation should be monitored routinely in intensive care units. The Ramsay and the Observer's Assessment of Alertness and Sedation scales showed equal efficacy. Bispectral index might prove useful for discriminating between deeper levels of sedation.

Crystal structure of potassium rubidium bis(L-malate) L-malic acid, K(K0.67Rb0.33)(C4H5O5)2 · C4H6O5

C12H16K1.67O15Rb0.33, orthorhombic, P212121 (no. 19), a = 7.721(1) Å, b = 7.895(2) Å, c = 29.914(3) Å, V = 1823.6Å3, Z = 4, Rgt(F) = 0.061, wRref(F2) = 0.147, T = 293 K.

[Hafnia alvei in a rare case of severe pneumonia in a postanesthesia recovery unit]

An 85-year-old man with a history of moderate chronic obstructive pulmonary disease in treatment with anticholinergic drugs was admitted to the recovery unit for postoperative monitoring after right inguinal herniorrhaphy surgery and removal of a strangulated intestinal section. On the third day after surgery the patient developed radiographic signs consistent with pneumonia and required mechanical ventilation. Two blood cultures and a respiratory secretion sample grew a microorganism identified as Hafnia alvei. H. alvei is a gram-negative bacillus that colonizes the digestive tract of humans and animals and in immunodepressed patients it can colonize the mouth and pharynx. Isolation of H. alvei is described in the literature on pediatric patients and those with a history of immune deficiency or chronic disease. Infection has a severe impact on general health. We report a rare and interesting case of pneumonia and bacteremia from H. alvei infection acquired by an immunocompetent patient soon after arrival in the postoperative recovery unit. The patient died of the infection.

Pressure-volume curve variations after a recruitment manoeuvre in acute lung injury/ARDS patients: implications for the understanding of the inflection points of the curve

BACKGROUND AND OBJECTIVE

Although the pressure-volume (P-V) curve has been proposed in the management of mechanically ventilated patients, its interpretation remains unclear. Our aim has been to study the variations of the P-V curve after a recruitment manoeuvre (RM). Our hypothesis was that the lower inflection point (LIP) represents the presence of compressive atelectases, so it should not change after lung recruitment, while the upper inflection point (UIP) reflects reabsorptive atelectases, and an effective recruitment should result in changes at this level.

METHODS

Two P-V curves (quasi-static method) separated by an RM (40 cmH2O, two consecutive manoeuvres) were plotted in 35 postoperative patients with criteria of acute lung injury/acute respiratory distress syndrome (ARDS). LIP, UIP and expiratory inflection point (EIP) were defined as the first point where the curve consistently starts to separate from the line.

RESULTS

One to six measurements were obtained per patient (73 procedures). Neither the lower nor the EIPs varied significantly after the RM (P = 0.11 and 0.35, respectively). An UIP was observed in 18 curves (25%) before the RM and disappeared on nine occasions after the recruitment. Similar results were obtained when first measurements only were analysed, and when the cause (pulmonary vs. extrapulmonary), severity of lung injury or duration of mechanical ventilation at first measurement were studied.

CONCLUSIONS

An RM does not modify the LIP significantly, but induces the disappearance of the UIP in 50% of the cases in which this point is found.

Direct automatic screening of soils for polycyclic aromatic hydrocarbons based on microwave-assisted extraction/fluorescence detection and on-line liquid chromatographic confirmation

An integrated screening-confirmation system for PAHs in soils is presented. The sample screening configuration comprises on-line microwave-assisted extraction of the selected pollutants, followed by continuous preconcentration and sample clean-up on RP-C18. Those samples for which the total concentration is close to or above the threshold limit established (10 microg/g) are subjected to liquid chromatographic separation for confirmation. An evaluation of the qualitative data obtained was also carried out, by calculating the unreliability zone as well as the false positive and false negative rates. The whole method (extraction/determination/confirmation) was validated using industrial soil and harbour sediment certified reference materials (IRMM, European Commission CRM 524 and CRM 535). Application to the screening of solid environmental samples with subsequent confirmation of the results is also presented.

Adjusting positive end-expiratory pressure and tidal volume in acute respiratory distress syndrome according to the pressure-volume curve

BACKGROUND

Management of acute respiratory distress syndrome (ARDS) patients implies the selection of the adequate ventilatory parameters, essentially PEEP and tidal volume (Vt), to prevent ventilator-induced lung injury. These parameters should be reset as the lung injury evolves. Among the different methods proposed for the adjustment of the ventilator, the measurement of the P-V curve has emerged as a useful, although debated, tool. Our aim has been to study the relationship between the different inflection points of the P-V curve in ARDS patients, and to assess the changes in the empiric PEEP and Vt (PEEP(emp), V(temp) following its use.

METHODS

P-V curves were measured in 27 patients (lung injury score [LIS] >or= 2, 69 measurements) by means of the low-flow continuous inflation method.

RESULTS

A lower inflection point (LIP) was found in all patients and, although it correlated with the PEEP(emp), there was only a fair concordance, so the PEEP was modified in 80% of the cases. The expiratory inflection point (EIP) was significantly lower than the LIP (6.3 +/- 1.7 vs. 8.1 +/- 3.2, P = 0.008). An upper inflection point was observed in 16 measurements (23%) and the Vt was reset in 20% of the cases. Both PEEP and Vt were readjusted on 10 occasions (14%). Only the EIP was significantly higher on the first 3 days of mechanical ventilation. The LIS was correlated with all the inflection points. There were no differences for any parameter independent of the cause of the ARDS (pulmonary/extrapulmonary).

CONCLUSIONS

The quasi-static measurement of the P-V curve is a simple method, easy to interpret, for objective adjustment of the ventilatory parameters in ARDS patients as the lung injury evolves. The implementation of this strategy may vary the empiric clinical practice. The role of the EIP for the evaluation of the severity of lung injury deserves further investigation.

Chemical isomerism as a key to explore free-energy landscapes in disordered matter

The effects of a minor chemical modification on the microscopic structure of a material in its glass and crystal phases are investigated by the concurrent use of neutron diffraction and computer simulation. Significant changes in short-, intermediate-, and long-range order are found, resulting from the change in molecular structure. These differences are explainable by a shift in the balance between directional and excluded-volume interactions.

Rifampin and isoniazid resistance associated mutations in Mycobacterium tuberculosis clinical isolates in Seville, Spain

The susceptibility phenotypes of 964 clinical isolates of Mycobacterium tuberculosis were studied over a 7-year period in Seville, Spain. Thirty-eight (3.9%) strains were rifampin (RMP) resistant, 79 (8.2%) were isoniazid (INH) resistant and 22 (2.3%) were resistant to at least both antimicrobials (multidrug-resistant, MDR). We studied the mechanisms of resistance to these drugs in 94 resistant clinical isolates of M. tuberculosis using three molecular methods: 1) PCR-single strand conformation polymorphism (SSCP) analysis, 2) RFLP analysis using B1/B2 primers, and 3) sequence analysis. Five different mutations were detected in the rpoB gene: Ser531-->Leu (72.3%), His526-->Asp (12.8%), Asn518-->Ser (2.1%), Gln513-->Leu (2.1%) and a nine-nucleotide deletion (2.1%). In the case of resistance to INH, four different mutations in the katG gene were detected, Ser315-->Thr (58.0%), Ser315-->Leu (2.9%), partial deletion (5.8%) and Ile304-->Val (1.4%), while in the inhA regulatory region the only mutation was the nucleotide substitution C209T (4.3%). No mutation was found in the ahpC promoter.

[Anesthesia in a case of Holt-Oram syndrome]

A 19-year-old man with Holt-Oram syndrome (HOS) underwent emergency surgical treatment of an occipital abscess. He presented total aplasia of the radius and first and second finger of the left hand, asymmetric thorax and complex cyanotic cardiopathy with double output of the right ventricle that had been treated on several occasions, malpositioning of the large vessels and interventricular conduction. He had been treated with digoxin for episodes of supraventricular tachycardia. After premedication with 0.4 mg of atropine, balanced general anesthesia was induced with etomidate and remifentanil and maintained with O2/air/desflurane and infused remifentanil. The patient remained hemodynamically stable during surgery and tubes were removed in the operating room with no complications. HOS, a hereditary disease characterized by congenital malformations of the upper extremities and the heart, is often associated with rhythm disorders. Problems that may develop in such patients during anesthesia include difficulty catheterizing vessels, difficult orotracheal intubation and ventilation, hemodynamic instability, and the presentation of arrhythmias and cardiac arrest.

[Prolonged muscle weakness associated with the administration of non-depolarizing neuromuscular blocking agents in critically ill patients]

Generalized muscle weakness is a common disorder in patients undergoing mechanical ventilation. The cause is unknown but is attributed to the administration of non-depolarizing neuromuscular blocking and other drugs, mainly steroids, or to the presence of sepsis or multiorgan failure. Specific clinical pictures (polyneuropathy, myopathy and prolonged muscle weakness) develop in function of the underlying cause, although etiological factors may sometimes interact. Differential diagnosis is carried out with the aid of electromyography and pathology of the peripheral muscle. Costs are high and prognosis is uncertain. Completeness of neuromuscular blockade must be monitored in these patients to guide the administration of drugs, to avoid overdoses, to maintain muscle activity and to detect a chain of reactions among concomitant medications or pathophysiologic changes.

Use of real-time PCR and fluorimetry for rapid detection of rifampin and isoniazid resistance-associated mutations in Mycobacterium tuberculosis

Very fast amplification of DNA in small volumes can be continuously monitored with a rapid cycler that incorporates fluorimetric detection. Primers were designed to amplify a 157-bp fragment of the rpoB gene spanning codons 526 and 531 and a 209-bp fragment of the katG gene spanning codon 315 of Mycobacterium tuberculosis. Most mutations associated with resistance to rifampin (RMP) and isoniazid (INH) in clinical isolates occur in these codons. Two pairs of hybridization probes were synthesized; one in each pair was 3' labeled with fluorescein and hybridized upstream of the codon with the mutation; the other two probes were 5' labeled with LightCycler-Red 640. Each pair of probes recognized adjacent sequences in the amplicon. After DNA amplification was finished by using a LightCycler, the temperature at which the Red 640 probe melted from the product was determined in a 3-min melt program. Twenty M. tuberculosis clinical isolates susceptible to streptomycin, INH, RMP, and ethambutol and 36 antibiotic-resistant clinical M. tuberculosis isolates (16 resistant to RMP, 16 to INH, and 4 to both antimicrobial agents) were amplified, and the presence of mutations was determined using single-strand conformation polymorphism analysis, the LiQor automated sequencer, and the LightCycler system. Concordant results were obtained in all cases. Within 30 min, the LightCycler method correctly genotyped all the strains without the need of any post-PCR sample manipulation. Overall, this pilot study demonstrated that real-time PCR coupled to fluorescence detection is the fastest available method for the detection of RMP and INH resistance-associated mutations in M. tuberculosis clinical isolates.