The continuous femoral nerve block catheter for postoperative analgesia: bacterial colonization, infectious rate and adverse effects

We investigated the incidence of bacterial and vascular or neurological complications resulting from femoral nerve catheters used for postoperative analgesia. Patients requiring continuous femoral blockade were consecutively included. Using surgical aseptic procedure, 211 femoral nerve catheters were placed (short-beveled insulated needle, peripheral nerve stimulator). After 48 h, each catheter was removed and semiquantitative bacteriological cultures were performed on each distal catheter tip. Postoperative analgesia and antibiotics were standardized. All complications during the insertion of the catheters and postoperatively (after 48 h and 6 wk) were noted. Few initial complications with no immediate or delayed complications were noted (20 difficult insertions, 3 impossible injections, 3 ineffective catheters, and 12 vascular punctures). After 48 h, 208 catheters were analyzed; 57% had positive bacterial colonization (with a single organism in 53%). The most frequent organisms were Staphylococcus epidermidis (71%), Enterococcus (10%), and Klebsiella (4%). Neither cellulitis nor abscess occurred. Three transitory bacteremias likely related to the catheter occurred. After 6 wk, no septic complications were noted. One femoral paresthesia, partially recovered 1 yr later, was noted. We conclude that the risk of bacterial complications is small with femoral nerve catheters, although the rate of colonization is frequent.

IMPLICATIONS

In this prospective study, continuous femoral nerve catheters were effective for postoperative analgesia but had a frequent rate of bacterial catheter colonization. We found no serious infections after short-term (2-day) infusion. Side effects were few, but one nerve injury occurred.

Training is required to improve the reliability of esophageal Doppler to measure cardiac output in critically ill patients

OBJECTIVES

Assessment of and effect of training on reliability of esophageal Doppler (ED) versus thermodilution (TD) for cardiac output (CO) measurement.

DESIGN

Prospective study.

SETTING

Intensive care unit of a university hospital.

PATIENTS

64 consecutive critically ill patients requiring a pulmonary artery catheter, sedation, and mechanical ventilation.

INTERVENTIONS

Esophageal Doppler CO measurements were performed by the same operator, whereas TD CO measurements were carried out by other independent operators. A training period involving the first 12 patients made the operator self-confident. In the remaining patients, the reliability of ED was assessed (evaluation period), using correlation coefficients and the Bland and Altman diagram. Between training and evaluation periods, correlation coefficients, biases, and limits of agreement were compared.

MEASUREMENTS AND RESULTS

During training and evaluation periods, 107 and 320 CO measurements were performed in 11 out of 12 patients and in 49 out of 52 patients, respectively. Continuous CO monitoring was achieved in 6 out of 11 patients and in 38 out of 49 patients during training and evaluation periods, respectively. Between the two periods, correlation coefficients increased from 0.53 to 0.89 (p < 0.001), bias decreased from 1.2 to 0.1 l x min(-1) (p < 0.001), and limits of agreement decreased from 3.2 to 2.2 l x min(-1) (p < 0.001).

CONCLUSION

A period of training involving no more than 12 patients is probably required to ensure reliability of CO measurement by ED.

Brachial plexus block with bupivacaine: effects of added alpha-adrenergic agonists: comparison between clonidine and epinephrine

The effects of clonidine and epinephrine, administered into the brachial plexus sheath, were evaluated in 60 patients who underwent surgery of the upper limb. All patients received 40 to 50 ml of 0.25% bupivacaine, injected into the brachial plexus sheath, using the supraclavicular technique. The patients were randomly allocated to two groups so that 30 patients received 150 micrograms clonidine hydrochloride (Group I), and 30 received 200 micrograms epinephrine (Group II). The quality and the duration of analgesia were assessed as well as the possible side-effects. The block produced with the addition of clonidine was longer (994.2 +/- 34.2 vs 728.3 +/- 35.8 min) and superior to that with epinephrine (P less than 0.001). No major side-effects were recorded. We conclude that the injection of clonidine into the brachial plexus sheath is an attractive alternative to epinephrine to prolong the duration of analgesia following upper limb surgery under conduction anaesthesia.

Peribulbar versus retrobulbar anesthesia for ophthalmic surgery: an anatomical comparison of extraconal and intraconal injections

BACKGROUND

Peribulbar and retrobulbar anesthesia have long been opposed on the basis of the existence of an intermuscular membrane, which is supposed to separate the intraconal from the extraconal spaces in a water-tight fashion. A local anesthetic injected outside the cone should spread through this septum to reach the nerves to be blocked. The existence of this septum is questioned. The aim of this study was to compare the spread of a colored latex dye injected intraconally or extraconally to simulate both retrobulbar and peribulbar anesthesia.

METHODS

The authors used 10 heads from human cadavers. For each head, one eye was injected intraconally, and the other eye was injected extraconally. The heads were then frozen and sectioned into thin slices following various planes. They were then photographed and observed.

RESULTS

There was no evidence of the existence of an intermuscular septum separating the intraconal and extraconal spaces. Those two spaces appeared to be part of a common spreading space, the corpus adiposum of the orbit.

CONCLUSIONS

These results are in accord with the fact that clinical studies were not able to clearly demonstrate that retrobulbar anesthesia is more efficient than peribulbar anesthesia. On the basis of a similar clinical efficacy of the two techniques as a result of similar spreading of the local anesthetic injected, and a potentially higher risk of introducing the needle into the muscular cone, the authors recommend replacing retrobulbar anesthesia with peribulbar anesthesia.

Pulsed Doppler ultrasonography guidance for catheterization of the subclavian vein: a randomized study

BACKGROUND

Catheterization of the subclavian vein may lead to severe complications. The current randomized study compared a technique of pulsed Doppler ultrasonography guidance and the standard method for subclavian vein catheterization.

METHODS

Standard and Doppler ultrasonography guidance methods were performed by the same physician in 286 patients, 143 in each group. Primary end points were immediate complications (arterial puncture, pneumothorax, wrong position of catheter tip), failures, the number of subclavian vein catheterizations with immediate complication or failure, the number of skin punctures per catheterization, and the time to placement of the guide wire. The secondary end points were the determination of predicting factors of successful cannulation in each group.

RESULTS

Both groups were similar according to morphologic parameters of the patients. A greater number of subclavian vein catheterizations were performed on the right side using Doppler guidance (105 vs. 73, P < 0.01). Doppler guidance decreased complications (5.6% vs. 16.8%, P < 0.01), largely because of a smaller number of catheters for which the tip was defined to be in incorrect position (0.7% vs. 7.7%, P < 0.01). The time to catheterization was longer with Doppler guidance (300 vs. 27 s, P < 0.001). Failures, catheterizations of the subclavian vein with immediate complications or failure, and the total number of skin punctures per catheterization were similar in both groups. Using Doppler guidance, the presence of a good Doppler signal (124 of 143) was predictive of successful catheterization (123 successful cannulations, P < 0.001).

CONCLUSIONS

Doppler guidance reduces the incidence of inappropriately positioned subclavian catheters.

Clinical pharmacokinetics during continuous haemofiltration

Continuous haemofiltration is an extracorporeal technique that is increasingly used to remove fluid, electrolytes, and other waste products from the blood supply of critically ill patients with acute renal failure. Continuous arteriovenous haemofiltration (CAVH), where the blood exits the body from an artery and re-enters through a vein, is widely used. Continuous venovenous haemofiltration (CVVH), where blood both exits and enters through a vein by way of a mechanical pump, avoids problems that result from the variable ultrafiltration rate found during CAVH. Continuous arteriovenous or venovenous haemodiafiltration (CAVHD or CVVHD) combine continuous haemofiltration and haemodialysis. All methods involve ultrafiltration of the patient's blood through a filter that is highly permeable to water and small molecules. Drug elimination by haemofiltration depends mainly on the rate of ultrafiltration, the drug protein binding and the sieving coefficient of the membrane. Because patients undergoing continuous haemofiltration have impaired renal function, dosage reduction is often recommended so that adverse drug reactions are avoided. In contrast, if drug removal by haemofiltration is significant, dosage supplementation may be required to ensure therapeutic efficacy of the drug. Therefore, knowledge of the impact of continuous haemofiltration on drug elimination and the pharmacokinetic profile of drugs is essential to good clinical management. The currently available information on the clinical pharmacokinetic aspects of drug therapy during continuous haemofiltration are summarised. Drugs commonly associated with haemofiltration therapy are tabulated with updated pharmacokinetics and drug-monitoring information.

Increased risk of unintentional dural puncture in night-time obstetric epidural anesthesia

PURPOSE

To evaluate the experience of the operator and the time of epidural anesthesia as factors contributing to unintentional dural puncture (UDP).

METHODS

In a prospective analysis of recorded cases of UDP the following variables were recorded: maternal height, weight, and weight gain, type of personnel providing epidural analgesia, number of attempts, and hour of the epidural procedure. Work time was divided into day-time (8 AM to 7 PM) and night-time (7 PM to 8 AM), according to the change of coverage of the delivery suite. Night-time was divided into first (7 PM to midnight) and second parts (midnight to 8 AM). Relative risk was used to compare the incidence of UDP among different work-times.

RESULTS

A total of 1489 consecutive epidural procedures were considered. The incidence of dural puncture was 0.8% (12 cases). The relative risk was higher for night-time than day-time (risk ratio 6.33; 95% confidence interval, 1.39 to 28.80; P = 0.006). Seven cases were caused by three operators with poor expertise, and five by two skilled obstetric anesthesiologists.

CONCLUSION

Operator experience and hour of procedure appear to be two important risk factors of UDP The increased risk of UDP in night-work could result from human factors such as fatigue, sleep deprivation or interruption.

Ophthalmic regional anesthesia: medial canthus episcleral (sub-tenon) anesthesia is more efficient than peribulbar anesthesia: A double-blind randomized study

BACKGROUND

Regional anesthesia and especially peribulbar anesthesia commonly is used for cataract surgery. Failure rates and need for reinjection remains high, however, with peribulbar anesthesia. Single-injection high-volume medial canthus episcleral (sub-Tenon's) anesthesia has proven to be an efficient and safe alternative to peribulbar anesthesia.

METHODS

The authors, in a blind study, compared the effectiveness of both techniques in 66 patients randomly assigned to episcleral anesthesia or single-injection peribulbar anesthesia. Motor blockade (akinesia) was used as the main index of anesthesia effectiveness. It was assessed using an 18-point scale (0-3 for each of the four directions of the gaze, lid opening, and lid closing, the total being from 0 = normal mobility to 18 = no movement at all). This score was compared between the groups 1, 5, 10, and 15 min after injection and at the end of the surgical procedures. Time to onset of the blockade also was compared between the two groups, as was the incidence of incomplete blockade with a need for supplemental injection and the satisfaction of the surgeon, patient, and anesthesiologist.

RESULTS

Episcleral anesthesia provided a quicker onset of anesthesia, a better akinesia score, and a lower rate of incomplete blockade necessitating reinjection (0 vs. 39%; P < 0.0001) than peribulbar anesthesia. Even after supplemental injection, peribulbar anesthesia had a lower akinesia score than did episcleral anesthesia. Peribulbar anesthesia began to wear off during surgery, whereas episcleral anesthesia did not.

CONCLUSION

Medial canthus single-injection episcleral anesthesia is a suitable alternative to peribulbar anesthesia. It provides better akinesia, with a quicker onset and more constancy in effectiveness.

Endotracheal and aerosol administrations of ceftazidime in patients with nosocomial pneumonia: pharmacokinetics and absolute bioavailability

Pharmacokinetic studies on ceftazidime, an aminothiazole cephalosporin with a wide spectrum of antibacterial activity, including activity against Pseudomonas aeruginosa, were performed in patients with nosocomial pneumonia. The concentration-time profiles of ceftazidime in plasma, urine, and bronchial secretions of 12 patients were investigated after intravenous (i.v.) (n = 12), endotracheal (n = 10), and aerosol (n = 5) administrations. In all cases a 1-g dose was administered. Concentrations of drug in all samples were assayed by high-performance liquid chromatography with UV detection. The elimination of the drug from the blood followed a biexponential (i.v. administration) or a monoexponential (endotracheal and aerosol administrations) decay, with an elimination half-life of 6 h and a total body clearance of 4.2 liters/h. The apparent volume of distribution was 0.36 liter/kg of body weight. Renal clearance of the drug accounted for 58% of the total clearance; 66% +/- 17.7%, 33.5% +/- 17.3%, and 6.59% +/- 3.45% of the administered dose were eliminated in urine as parent drug after i.v., endotracheal, and aerosol administrations, respectively. The absolute bioavailabilities were 0.47 and 0.08 for endotracheal and aerosol administrations, respectively. Very high concentrations were found in bronchial secretions after local administration. The MICs for 90% of the most important pathogens responsible for nosocomial infections were exceeded by concentrations in bronchial secretion for up to 12 h after i.v. infusion and for up to 24 h after endotracheal and aerosol administrations.

Deep localized neodymium (Nd)-YAG laser photocoagulation in liver using a new water cooled and echoguided handpiece

Thirty-six deep hepatic lesions of localized photocoagulation were induced in 11 pigs by means of a neodymium-YAG laser. Laser applications of 80 W/10 sec (10.190 W/cm2) were transmitted through a handpiece coupled to a water-cooling circulation system to protect the quartz fiber and positioned through an echo-guided trocar. During irradiation, temperature was sufficient for vaporization up to 5 mm from the laser source and high enough for tumor cell kill at a 10-mm distance (54 degrees C/60 sec). Intraoperative ultrasound visualized increasing photocoagulation (12-18 mm), and further controls demonstrated an echo-free core of vaporization progressively covered by increasing fibrosis, well demarcated from normal parenchyma. Microscopy revealed central coagulative necrosis marginated from the third day by a growing fibrosis. By day 20 immunoblasts and mast cells were in profusion in the lesion border, and by day 120 a fibrotic network had invaded the scar and confirmed healing free of complication. This technique is proposed for deep vaporization of disseminated hepatic metastases.

Insertion time of the pulmonary artery catheter in critically ill patients

OBJECTIVES

Measurement of the time elapsed from the decision to use a pulmonary artery catheter to the onset of the adapted treatment.

DESIGN

Prospective study.

SETTING

Critical care unit of a university hospital.

PATIENTS

A total of 104 critically ill patients.

INTERVENTIONS

The time elapsed from the decision to use a pulmonary artery catheter to the onset of the adapted treatment. Five time intervals (availability, preparation, catheterization, data collection, and therapeutic intervals) were individualized according to the times of decision of pulmonary artery catheter insertion, operator's hand washing, venipuncture, postoperative dressing, data collection, and the effective onset of subsequent therapy.

MEASUREMENTS AND MAIN RESULTS

Among 120 used pulmonary artery catheters, seven could not be inserted. The time to use the pulmonary artery catheter was never shorter than 45 mins (median value = 120 mins). For availability, preparation, catheterization, data collection, and therapeutic intervals, the median values were 30, 20, 20, 20, and 10 mins, respectively. The availability and data collection intervals were shortened during the night period and the fourth quarter of the study, respectively.

CONCLUSIONS

The pulmonary artery catheter use is time consuming. However, the availability and data collection intervals could be shortened.

Cardiac output measurement in critically ill patients: comparison of continuous and conventional thermodilution techniques

The purpose of the study was to compare cardiac output (CO) measurement by continuous (CTD) with that by conventional thermodilution (TD) in critically ill patients. In 19 of 20 critically ill patients requiring a pulmonary artery catheterism, 105 paired CO measurements were performed by both CTD and TD. Regression analysis showed that: CTD CO = 1.18 TD CO - 0.47. Correlation coefficient was 0.96. Bias and limit of agreement were -0.8 and 2.4 L.min-1, respectively. When a Bland and Altman diagram was constructed according to cardiac index ranges, biases were -0.2 and -0.3 and -0.8 L.min-1.m-2 and limits of agreement were 0.3, 0.7 and 1.6 L.min-1.m-2 for low (< 2.5 L.min-1.m-2), normal (between 2.5 and 4.5 L.min-1.m-2) and high (> 4.5 L.min-1.m-2) cardiac indexes, respectively. It is concluded that CTD, compared with TD, is a reliable method of measuring CO, especially when cardiac index is < or = 4.5 L.min-1.m-2.

The comparative electrophysiologic and hemodynamic effects of a large dose of ropivacaine and bupivacaine in anesthetized and ventilated piglets

Ropivacaine is less potent and less toxic than bupivacaine. We administered these two local anesthetics in a cardiac electrophysiologic model of sodium thiopental-anesthetized and ventilated piglets. After assessing the stability of the model, bupivacaine (4 mg/kg) and ropivacaine (6 mg/kg) were given IV in two groups (n = 7) of piglets. No alteration in biological variables was reported throughout the study. Bupivacaine and ropivacaine similarly decreased mean aortic pressure from 99 +/- 22 to 49 +/- 31 mm Hg and from 87 +/- 17 to 58 +/- 28 mm Hg, respectively, and decreased the peak of the first derivative of left ventricular pressure from 1979 +/- 95 to 689 +/- 482 mm Hg/s and from 1963 +/- 92 to 744 +/- 403 mm Hg/s, respectively. Left ventricular end-diastolic pressure was similarly increased from 6 +/- 5 to 9 +/- 5 mm Hg and from 6 +/- 4 to 12 +/- 4 mm Hg, respectively. Bupivacaine and ropivacaine similarly lengthened the cardiac cycle length (R-R; from 479 +/- 139 to 706 +/- 228 ms and from 451 +/- 87 to 666 +/- 194 ms, respectively), atria His (from 71 +/- 15 to 113 +/- 53 ms and from 64 +/- 6 to 86 +/- 10 ms, respectively), and QTc (QTc = QT x R-R(-0.5), Bazett formula; from 380 +/- 71 to 502 +/- 86 ms and from 361 +/- 33 to 440 +/- 56 ms, respectively) intervals. Bupivacaine altered to a greater extent the PQ (the onset of the P wave to the Q wave of the QRS complex) (from 97 +/- 20 to 211 +/- 60 ms versus from 91 +/- 8 to 145 +/- 38 ms, P < 0.05), QRS (from 58 +/- 3 to 149 +/- 34 ms versus from 60 +/- 5 to 101 +/- 17 ms, P < 0.05), and His ventricle interval (from 25 +/- 4 to 105 +/- 30 ms vs from 25 +/- 4 to 60 +/- 30 ms, P < 0.05) than ropivacaine. A 6 mg/kg ropivacaine dose induced similar hemodynamic alterations as 4 mg/kg bupivacaine. However, bupivacaine altered the variables of ventricular conduction (QRS and His ventricle) to a greater extent.

IMPLICATIONS

A 6 mg/kg ropivacaine dose induced similar hemodynamic alterations as 4 mg/kg bupivacaine. However, bupivacaine altered the variables of ventricular conduction (QRS and His ventricle) to a greater extent.

Intravenous nicardipine for severe hypertension in pre-eclampsia--effects of an acute treatment on mother and foetus

OBJECTIVES

To assess the efficacy in lowering blood pressure, and the safety for mother and foetus of an acute nicardipine therapy in severe pre-eclampsia.

DESIGN

Prospective clinical study.

SETTING

One university hospital obstetric unit.

PATIENTS

Twenty consecutive adult pre-eclamptic patients with severe hypertension.

INTERVENTION

Nicardipine, 1 microgram/kg per min, was given intravenously to lower the mean arterial pressure (MAP) by at least 15%. Then, the dosage was reduced by 1/3, and the final dosage was determined to maintain MAP at 20-30% below the initial value, by increasing or decreasing the infusion rate by 0.5 mg/h.

MEASUREMENTS AND RESULTS

Maternal MAP and heart rate (HR) were assessed every 5 min for 1 h. Foetal HR (FHR) was recorded throughout the study period and assessed for Fischer score. Gestational age, Apgar scores, birth weight, capillary filling time and the duration of stay in the paediatric intensive care unit (ICU) were used to evaluate the short-term perinatal outcome. A 15-30% decrease in MAP occurred within 15-20 min in all patients. An increase in HR was noted, and two patients had severe tachycardia. Maternal side effects included flushing, headache, nausea and dizziness. FHR showed a transient decrease in acceleration episodes and occurrence of decelerations. No nicardipine-related foetal distress occurred. Four infants born during the study period did well at birth and had a good outcome.

CONCLUSIONS

Acute nicardipine therapy can induce severe maternal tachycardia. No severe foetal or neonatal adverse effects occurred. This dose scheme requires comparison with alternative therapeutic options.

Mechanisms of ventricular arrhythmias induced by myocardial contusion: a high-resolution mapping study in left ventricular rabbit heart

BACKGROUND

The aims of the Langendorff-perfused rabbit heart study were to evaluate the arrhythmogenic consequences of myocardial contusion and to determine the mechanism of arrhythmia.

METHODS

Six hearts were in the control group, and 24 hearts (intact heart protocol) were submitted to one of four different contusion kinetic energies (75, 100, 150, or 200 millijoules [mJ]; n = 6). Occurrence of arrhythmia, of an electrically silent area (i.e., area with no electrical activity), and of line of fixed conduction block were reported before and for 1 h after contusion. In 16 hearts (frozen hearts) submitted to cryoprocedure and contusion impact of 100 or 200 mJ, ventricular conduction velocities, anisotropic ratio, wavelengths, ventricular effective refractory period, and its dispersion were measured before and for 1 h after contusion. Using high-resolution mapping, arrhythmias were recorded and analyzed.

RESULTS

The intact heart study showed that the number and seriousness of contusion-induced arrhythmias increased with increasing contusion kinetic energy, as did the number of electrically silent areas (five of six ventricular fibrillations and five of six electrically silent areas at 200 mJ). In the frozen heart study, immediately after contusion ventricular effective refractory periods were shortened and dispersed, and wavelengths were also shortened. The arrhythmia analysis showed that all ventricular tachycardias but one were based on reentry developed around an electrically silent area or a line of fixed conduction block.

CONCLUSIONS

Myocardial contusion has direct arrhythmogenic effects, and the seriousness of arrhythmia increases with the level of contusion kinetic energy. The mechanism of arrhythmia was mainly based on reentrant circuit around a fixed obstacle.

[Mechanisms of the cardiac toxicity of bupivacaine]

Of all the amide local anaesthetics, bupivacaine is said to be the most cardiotoxic. This toxicity is seen mostly when there is a sudden increase in the plasma concentration of bupivacaine. It involves both, or either, electrical and mechanical structures within the heart. The main site of action on cardiac conduction tissue is the Vmax of phase 0 of the action potential of fast-reacting structures (INa current). Bupivacaine, like lidocaine and the other class I antiarrhythmic drugs, blocks the sodium channels, this block being more slowly reversible. The disturbance of sodium channels throughout the heart leads to a decreased conduction speed throughout the conduction system, thus explaining possible acute conduction disturbances originating below the bundle of His. The ventricular dysrhythmias described are due to a re-entry circuit secondary to a slowing in conduction speed. However, the sinus bradycardias and junctional disturbances seen in toxic accidents are probably due to an inhibition of the slow current of the atrial and atrio-ventricular nodes (Isi current). The experimental observation of an increase in the atrial monophase potential and the corrected QT interval suggests that repolarization currents are also involved (IK current ?). It would therefore seem that modifications in membrane permeabilities are the cause of the seriousness of the clinical picture. Bupivacaine, at toxic levels, has a direct effect on contractility. The negative inotropic effects seem to be due to a fall in the intracytoplasmic calcium concentration on which depends the excitation-contraction couple, as well as disturbed cellular energetic events dependent on the contraction.(ABSTRACT TRUNCATED AT 250 WORDS)

Preoperative nutritional evaluation of elderly patients: the Mini Nutritional Assessment as a practical tool

BACKGROUND AND GOAL

Age and malnutrition are each surgical risk factors. Because the Mini Nutritional Assessment (MNA) has been specifically designed for assessing the nutritional status of elderly patients, it can be used for preoperative nutritional evaluation. Therefore, the MNA was included in the preoperative clinical evaluation of patients over 60 years of age to describe their nutritional status.

METHODS

Every patient over 60 years of age, scheduled for elective surgery, was seen in anaesthesiology consultation and was submitted to the MNA. The MNA is a clinical score consisting of four additive items: 'Anthropometric assessment' based on BMI, mid-arm and calf circumferences, weight loss; global evaluation; dietetic assessment, and subjective assessment - these last three items being obtained through a specific questionnaire. It requires no biological marker. Awarding to the obtained score, the MNA stratifies patients in the following categories: well-nourished (24 </= MNA </= 30), at risk of malnutrition (17 </= MNA < 23.5), and undernutrition (MNA < 17). Also recorded were: age, gender, type of scheduled operation, and the American Society of Anesthesiologists (ASA) physical status score. Results are given as median (extremes).

RESULTS

Four hundred and nineteen patients (50.4% women) were seen between January and October 1996. The mean age was 72 years (range, 60-98 years); BMI: 25.2 (12.8-40.4) kg m(-2). The MNA score was recorded in 408 patients, ranging from 1.5 to 30 (median: 26). According to the score, the patients were stratified in: well-nourished, 276 patients (67.6%), at risk, 104 patients (25. 5%) and suffering from overt malnutrition, 28 patients (6.9%). According to the ASA score, 290 patients were found to be at low or mild risk for anaesthesia and surgery (ASA 1 and 2), and 72 patients (24.8%) were stratified as being at least at risk of malnutrition. One hundred and eighteen other patients were found to be at a higher risk (ASA 3 and 4), and 58 (49.2%) were not well-nourished (MNA < 24).

CONCLUSION

The MNA was found to be well-suited for the preoperative assessment during anaesthesia consultation because it required no biological marker. It showed that approximately one-third of all the examined patients, and half of the ASA 3-4 patients, were not well-nourished. The ASA score could not predict poor nutritional status. The results suggested that nutritional assessment should be routinely performed in ASA 3-4 patients over 60 years of age.

Dispersion-based reentry: mechanism of initiation of ventricular tachycardia in isolated rabbit hearts

The aim of the study was to determine whether facilitation of reentry by potassium-channel openers is related to dispersion of refractoriness and/or modification of anisotropic properties of ventricular myocardium. The dispersion of ventricular effective refractory period (VERP), longitudinal and transverse ventricular conduction velocities (thetaL and thetaT, respectively), and wavelength [lambda = VERP x theta(L or T)] were studied in Langendorff-perfused left ventricular epicardium in 20 rabbits during infusion of incremental doses of levcromakalim or nicorandil. Dispersion of refractoriness was assessed using standard deviation of VERP mean (SD-VERP), dispersion index (DI; SD-VERP/mean VERP), and maximum dispersion (Dmax = VERPmax - VERPmin). Ventricular conduction velocities and anisotropic ratio were not modified, whatever the dose used. VERP and lambda were significantly shortened at high concentrations of levcromakalim and nicorandil. At these doses, SD-VERP, DI, and Dmax were increased significantly. Analysis of ventricular tachycardia induction, performed using a high-resolution ventricular mapping system, confirmed that heterogeneity and shortening of VERP were factors inducing functional conduction block. Our data suggest that, in rabbit left ventricular epicardium, functional conduction block facilitating the occurrence of reentry could be initiated by shortening and, especially, by dispersion of refractoriness during infusion of potassium-channel openers.

Release kinetics of cardiac troponin I and cardiac troponin T in effluents from isolated perfused rabbit hearts after graded experimental myocardial contusion

BACKGROUND

Few experimental studies report effects of direct contusion on cardiac enzyme release. Cardiac troponins I (cTnI) and T (cTnT) have been shown to be highly sensitive and specific markers of myocardial cell injury. This investigation was designed to determine and compare the acute effects of quantified magnitudes of blunt cardiac trauma upon release of cTnI and cTnT in comparison with creatine kinase (CK) and lactate dehydrogenase (LD).

METHODS

In 24 rabbit hearts prepared on a standard Langendorff apparatus, myocardial contusion (MC) was produced by a single blow with a ball falling from a predefined height, delivered directly to the surface of the heart. Hearts were divided into control (n = 6) and various quantified impacts: 75 mJoules (mJ) (n = 6), 100 mJ (n = 6), 200 mJ (n = 6). Coronary effluent samples for cTnI, cTnT, CK, and LD were collected at baseline, immediately after MC and 5, 15, 30, 45, and 60 minutes after MC. At the end of experiment, histologic condition was evaluated.

RESULTS

The anti-cTnI and cTnT MAbs used in the cTnI (Access) and cTnT (Elecsys) assays cross-react with cTnI and cTnT of the rabbit. The time-courses of cTnI, cTnT, CK, and LD were monophasic in form. After MC, all parameters rose significantly compared with baseline and with control group. The maximal release occurred immediately after MC. The area under the cTnI curve and the maximal cTnI concentration were linked to the contusion energy when increased at 200 mJ. Maximal concentrations and areas under cTnT, CK, LD time activity curve were not linked to the contusion energy level and showed no between-energy group differences. The correlation found between maximal cTnI and maximal cTnT concentrations was 0.70 (p = 0.0001). Histologic examination showed cellular disruption and after the more severe impact, the extent of pathologic changes was more extensive.

CONCLUSION

After graded experimental MC, maximal cTnI concentration and area under cTnI curve increase with the power of impact kinetic energy. Levels of cTnI allow a much higher accuracy in detecting the extent of myocardial injury postMC in comparison with cTnT, CK, and LD in this experimental study. These results should be consistent with the more extensive cTnI release with more severe impact in patients with blunt chest trauma. Furthermore, because specificity and time-course of release, both cTnI and cTnT should have a role in the diagnosis and evaluation of such patients.

The Mini Nutritional Assessment-Short Form for preoperative nutritional evaluation of elderly patients

The Mini Nutritional Assessment (MNA) is a clinical tool designed for assessing nutritional status of elderly patients. Used in preoperative evaluation of ambulatory patients over 60 years of age seen on anesthesia consultation in a previous study, it identified 6.9% patients with overt malnutrition out of a group of 408. However, four-fifths of 291 ASA 1-2 patients were well nourished, and underwent needless, non-contributory and time-consuming test. The MNA-Short Form (MNA-SF) has recently been devised as the first step of a two-step process: if negative, there would be no need to complete "full" MNA. Therefore, the base data of 408 MNA forms completed during the above-mentioned study was used for the purpose of comparing the MNA-SF to the MNA, to test whether the MNA-SF could have been the first step of a two-step nutritional evaluation of anesthesia patients. Median (range) age, and BMI were 72 (60-98) years, and 25.2 (12.8-40.4) kg x m(-2), respectively. There were equal numbers of men and women. In 144 cases, the MNA-SF was found positive (35.3%) with a median MNA of 21.5 (1.5-27) points. The MNA-SF predicted absence of overt malnutrition revealed by the MNA, with 100% sensitivity and negative predictive value (NPV). It was found less efficient for predicting absence of "possible" nutritional problems detected by the MNA (sensitivity 85.6% and NPV 92.8%). However, none of the 19 borderline patients would have had overt malnutrition, being only found "at risk of malnutrition" by the MNA. On the studied sample, the MNA-SF would have correctly sorted out 69.5% of the patients without severe malnutrition. We believe the MNA-SF should be used as the first step of an efficient preoperative nutritional evaluation of ambulatory elderly patients.

Multiple-dose pharmacokinetics of amikacin and ceftazidime in critically ill patients with septic multiple-organ failure during intermittent hemofiltration

The pharmacokinetic parameters of amikacin and ceftazidime were assessed in four patients undergoing hemofiltration for septic shock. The parameters were assessed during hemofiltration and in the interim period. The concentration-time profiles of these two drugs in plasma, urine, and ultrafiltrate were investigated after intravenous perfusion (30 min). In all cases a 1-g dose of ceftazidime was administered; for amikacin, the dosage regimen was adjusted according to the patient's amikacin levels (250 to 750 mg). Concentrations of drug in all samples were assayed by high-performance liquid chromatography with UV detection for ceftazidime and by enzyme multiplied immunoassay for amikacin. The elimination half-life (t1/2) and the total clearance of amikacin ranged from 31.1 to 138.2 h and from 5.4 to 8.9 ml/min, respectively, during the interhemofiltration period in anuric patients. Hemofiltration substantially decreased the t1/2 (3.5 +/- 0.49 h) and increased the total clearance (89.5 +/- 11.8 ml/min). The hemofiltration clearance of amikacin represented 71% of the total clearance, and the hemofiltration process removed, on average, 60% of the dose. During hemofiltration, the elimination t1/2 of ceftazidime (2.8 +/- 0.69 h) was greatly reduced and the total clearance increased (74.2 +/- 11.2 ml/min) compared with those in the interhemofiltration period (9 to 43.7 h and 7.4 to 16.8 ml/min, respectively). About 55% of the administered dose was recovered in the filtrate, and the hemofiltration clearance of ceftazidime was 46 +/- 14.3 ml/min. A redistribution phenomenon (rebound) in the amikacin and ceftazidime concentrations in plasma (35 and 28%, respectively) was reported after hemofiltration in two patients. The MICs for 90% of the most important pathogens were exceeded by the concentrations of the two drugs in plasma during the whole treatment of these patients.

Ventilatory effects of active compression-decompression in dogs

STUDY OBJECTIVE

To determine the ventilatory effect of active compression-decompression CPR and to compare it with two other techniques, standard manual cardiac massage and mechanical cardiac massage.

DESIGN

Prospective, randomized laboratory investigation.

PARTICIPANTS

Mongrel dogs.

INTERVENTIONS

Nine adult mongrel dogs were anesthetized, intubated, and mechanically ventilated. They were instrumented to measure arterial pressure, esophageal pressure, airway pressure, end-tidal carbon dioxide concentration, and minute ventilation.

RESULTS

After induction of ventricular fibrillation, three sequences of cardiac massage were performed randomly during mechanical ventilation, standard cardiac massage, mechanical cardiac massage, and active compression-decompression technique. The animals then were disconnected from the ventilator, and the three sequences were performed again. Active compression-decompression created negative minimum esophageal pressures and significantly decreased the minimum airway pressure as compared with the other techniques. Whatever the ventilatory condition, minute ventilation was increased dramatically during active compression-decompression.

CONCLUSION

In this model of cardiac arrest, an important increase in minute ventilation was observed during active compression-decompression. This effect was significantly greater than the increases observed with other techniques of cardiac massage and was related to the negative pressure generated by active decompression.

Electrophysiologic and arrhythmogenic effects of the potassium channel agonist BRL 38227 in anesthetized dogs

Although potassium channel openers have been demonstrated to induce arterial vasodilation and shortening of the QT interval, the complete in vivo hemodynamic and electrophysiologic profile of these drugs has not been fully established. We evaluated the effects of BRL 38227, the active enantiomer of cromakalim, on the electrophysiologic and hemodynamic parameters in anesthetized dogs. Four intravenous (i.v.) doses (0.01, 0.03, 0.1, and 0.3 mg/kg) of BRL 38227 (lemakalim) were given to four different groups of 6 anesthetized and mechanically ventilated dogs. Electrophysiologic and hemodynamic parameters were measured with bipolar catheters positioned in the right atria and the right ventricle and double micromanometers placed in the left ventricle and the aorta. Nine dogs died of ventricular fibrillation (VF; 6 of 6 after 0.3 mg/kg, 2 of 8 dogs after 0.1 mg/kg, and 1 of 7 dogs after 0.03 mg/kg BRL 38227). Three dogs had atrial tachycardia (1 had atrial flutter and 1 had atrial fibrillation after 0.03 mg/kg, and 1 had atrial fibrillation after 0.01 mg/kg BRL 38227). BRL 38227 did not modify heart rate (HR), corrected sinus recovery time (CSRT), and atrial or atrio-ventricular (A-V) conduction times. In contrast, PR interval, Luciani-Wenckebach cycle length (LW), HV interval, QRS duration, ventricular effective refractory period (VERP), QT interval, and monophasic action potential (AP) were significantly shortened in a dose-dependent manner. Left ventricular end-diastolic pressure (LVEDP) was not modified, whereas LVdP/dtmax decreased significantly at 0.1 mg/kg BRL 38227. Finally, there was a significant dose-dependent decrease in systolic, diastolic, and mean aortic blood pressure (SBP, DBP, MAP). We conclude that BRL 38227 shortens the ventricular parameters of conduction velocity and of repolarization and decreases BP, both in a dose-dependent manner. All doses were arrhythmogenic, suggesting that BRL 38227 has a low safety margin.

Effects of ketamine on ventricular conduction, refractoriness, and wavelength: potential antiarrhythmic effects: a high-resolution epicardial mapping in rabbit hearts

BACKGROUND

The aims of the study were to verify the effects of ketamine on ventricular conduction velocity and on the ventricular effective refractory period, to determine its effects on anisotropy and on homogeneity of refractoriness, and to use wavelength to determine whether ketamine has antiarrhythmic or arrhythmogenic properties.

METHODS

A high-resolution epicardial mapping system was used to study the effects of 50, 100, 150, and 200 microM racemic ketamine in 15 isolated, Langendorff-perfused rabbit hearts. Five hearts were kept intact to study the effects of ketamine on spontaneous sinus cycle length (RR) interval and its putative arrhythmogenic effects. In 10 other hearts, a thin epicardial layer was obtained by an endocardial cryoprocedure (frozen hearts) to study ventricular conduction velocity, ventricular effective refractory periods (five sites), and ventricular wavelength.

RESULTS

Ketamine induced a concentration-dependent lengthening of the RR interval. Ketamine slowed longitudinal and transverse ventricular conduction velocity with no anisotropic change, and it prolonged the ventricular effective refractory period with no significant increase in dispersion. Ventricular longitudinal and transverse wavelengths tend to increase, but this was not statistically significant. Finally, no arrhythmia could be induced regardless of the ketamine concentration.

CONCLUSION

Ketamine slowed ventricular conduction and prolonged refractoriness without changing anisotropy or increasing dispersion of refractoriness. Although these effects should result in significant antiarrhythmic effects of ketamine, this should not be construed to suggest a protective effect in ischemic or other abnormal myocardium.

Medial canthus episcleral (sub-Tenon) anesthesia imaging

Medial canthus single injection periocular anesthesia is an alternative technique to classical regional anesthesia techniques for cataract surgery. The occurrence of a chemosis at the end of this injection has made us question ourselves about the real site of injection. The purpose of this anatomic study was to identify this site with precision, and to describe the spreading of the injected solution. Various volumes of colored liquid latex were injected when using this technique on 10 human orbits. They were deeply frozen and sectioned in thin slices. The site of injection is clearly the episceral (sub-Tenon) space. This is a gliding space through which pass the ciliary nerves supplying the globe sensitivity. This could explain the high quality of the analgesia of the globe. With the larger volumes injected, spreading of the latex was detected in the orbicularis palpebra. This probably explains the good akinesia of the lids obtained without any facial block. Spreading of the latex to the rectus muscles sheaths should explain the good akinesia of the globe, but was only partially proved in this study. We conclude that the medial canthus single injection periocular anesthesia is an episcleral (sub-Tenon) injection which may explain good anesthesia.