Gildas Gueret

Acute renal dysfunction after cardiac surgery with cardiopulmonary bypass is associated with plasmatic IL6 increase.

BACKGROUND Acute renal dysfunction (ARD) is common after cardiac surgery with cardiopulmonary bypass (CPB). CPB results in a sudden systemic inflammatory response. Systemic and local pro-inflammatory cytokines synthesis has been linked with sub-clinical renal injury, especially tubular lesions. Therefore, we sought to assess the systemic synthesis pro-inflammatory cytokines and its association with perioperative ARD after cardiac surgery with CPB. METHODS Sixty-two patients undergoing cardiac surgery with CPB were prospectively included. Four groups of patients were defined according to blood creatinine increase: no ARD (less than 25% increase), faint ARD (25-50% increase), moderate ARD (50-100% increase), severe ARD (more than 100% increase). RESULTS Within the 48 post-operative hours was ARD observed as no dysfunction (41.9%), faint (32.2%), moderate (16.1%), severe (9.6%). One patient had to undergo a dialysis. Pre-operative characteristics were homogenous between the four groups excepted the left ventricle ejection fraction. ARD was associated with a low urinary output with high sodium excretion fraction. Significant increase of IL-6 level occurred when patients underwent a severe ARD despite no significant differences for the CRP and TNF-alpha concentrations. CONCLUSION Severe acute renal dysfunction after cardiac surgery with CPB is associated with a significant increased IL-6 systemic production.

Tumor necrosis factor-α downregulates sodium current in skeletal muscle by protein kinase C activation: involvement in critical illness polyneuromyopathy

Sepsis is involved in the decrease of membrane excitability of skeletal muscle, leading to polyneuromyopathy. This effect is mediated by alterations of the properties of voltage-gated sodium channels (Na(V)), but the exact mechanism is still unknown. The aim of the present study was to check whether tumor necrosis factor (TNF-α), a cytokine released during sepsis, exerts a rapid effect on Na(V). Sodium current (I(Na)) was recorded by macropatch clamp in skeletal muscle fibers isolated from rat peroneus longus muscle, in control conditions and after TNF-α addition. Analyses of dose-effect and time-effect relationships were carried out. Effect of chelerythrine, a PKC inhibitor, was also studied to determine the way of action of TNF-α. TNF-α induced a reversible dose- and time-dependent inhibition of I(Na). A maximum inhibition of 75% of the control current was observed. A shift toward more negative potentials of activation and inactivation curves of I(Na) was also noticed. These effects were prevented by chelerythrine pretreatment. TNF-α is a cytokine released in the early stages of sepsis. Besides a possible transcriptional role, i.e., modification of the channel type and/or number, we demonstrated the existence of a rapid, posttranscriptional inhibition of Na(V) by TNF-α. The downregulation of the sodium current could be mediated by a PKC-induced phosphorylation of the sodium channel, thus leading to a significant decrease in muscle excitability.

Management of cardiac arrest caused by coronary artery spasm: Epinephrine/adrenaline versus nitrates

BACKGROUND Cardiopulmonary resuscitation guidelines imply the use of epinephrine/adrenaline during cardiopulmonary arrest. However, in cardiac arrest situations resulting from coronary artery spasm (CAS), the use of epinephrine/adrenaline could be deleterious. METHODS AND RESULTS A 49-year-old patient underwent an emergency coronarography with an attempt to stent the coronary arteries. Radiologic imaging revealed a positive methylergonovine maleate (Methergine, Novartis Pharmaceuticals, East Hanover, NJ) test, with subocclusive CAS in several coronary vessels leading to electromechanical dissociation. Cardiopulmonary resuscitation was performed, and intracoronary boluses of isosorbide dinitrate were given to treat CAS. Epinephrine/adrenaline was not administered during resuscitation. Spontaneous circulation was obtained after cardioversion for ventricular fibrillation, and the patient progressively regained consciousness. CONCLUSION Resuscitation guidelines do not specify the use of trinitrate derivatives in cardiac arrest situations caused by CAS. The pros and cons of the use of nitrates and epinephrine/adrenaline during cardiac arrest caused by CAS are analyzed in this case report.

Sudden Death after Neck Dissection for Cancer

The goal of this study was to analyze the mortality data following neck dissection and determine the risk factors of early death. The hospital mortality records were analyzed from 3,015 consecutive patients who underwent neck dissection. A case control study analyzed risk factors of death during the first 3 postoperative days. The mortality incidences were 0.50% and 1.33%, respectively, during the first 3 and the first 30 postoperative days. Eleven of the 12 unexplained deaths occurred during the first 3 postoperative days, and most of these patients died suddenly. They were more likely to be alcoholic and to have undergone nerve section. In most of the patients who died after the third postoperative day, death was related to a postoperative complication. Although the mechanisms of sudden death remain unclear, careful follow-up of these patients during the early postoperative days should be performed to reduce the mortality risk by shortening the delay of care.

Sudden death after major head and neck surgery.

Purpose of reviewThis review will discuss the mortality after major ear, nose and throat surgery, particularly sudden death. It will also discuss the postoperative follow-up of patients. Recent findingsSudden death is a rare event after major ear, nose and throat surgery, and occurs mainly during the first three postoperative days. SummaryIn more recent studies, the mortality rate after neck dissection was below 4%, which is at a lower value than reported in previous studies. Sudden deaths have been described, however, mainly during the first three postoperative days. Alcoholism and perioperative hypotension are two predictive factors for cardiac complications. Careful follow-up of these patients during the early postoperative period should be performed to reduce the mortality by shortening the delay of care.

Étude d'un respirateur de jet ventilation, le Mistral®, sur banc d'essai

OBJECTIVE To test a high-frequency jet ventilator, the Mistral (Acutronic Laboratory) on a lung model. METHODS The jet ventilator Mistral was tested with two connectors (7 and 20 ml) and four catheters. Pressure and flow measurements were performed by varying the driving pressure (1 to 3 bars), the I/T ratio (0.25, 0.35, 0.45) and the frequency (1 to 5 Hz). Recorded data were: the volume delivered by the ventilator, the pressure measured in the connecting line between the ventilator and the injector and the difference between the end expiratory pressure measured by the ventilator through the injector and the tracheal pressure. RESULTS An increase in driving pressure induced a proportional increase in minute volume whatever the injection catheter used. After insufflation, when a Seldicath catheter was used, the pressure decrease was the slowest and the time constant the longest. Increase in frequency or I/T ratio, particularly beyond 0.35, was associated with an increase of the end expiratory pressure measured by the respirator. The gradient of pressure measured by the respirator and by an external sensor was lower with the 7 ml connector whatever the catheter used, and was larger with the Seldicath catheter. CONCLUSION The use of a low volume connector should be preferred, because it allows the measurement of the end expiratory pressure for a larger range of driving pressure, expiratory time and catheters. The performances of the Seldicath catheter are below those of the other catheters studied.

Comparaison de la mesure de la PETCO2 obtenue avec le Smart Capnoline™ avec la PaCO2 en postopératoire de chirurgie cardiaque chez des patients intubés puis extubés

OBJECTIVE To compare the PaCO(2) with the ETCO(2) obtained with the Smart Capnoline™ in the postoperative setting of cardiac surgery during ventilation and after extubation TYPE OF STUDY Prospective, observational. PATIENTS Twenty patients after cardiac surgery. METHODS In the intensive care unit, arterial blood gases were measured concomitantly with ETCO(2), and difference between PaCO(2) and ETCO(2) were calculated. Three CO(2) sensors were utilized: Filterline H set for intubated patients, Smart Capnoline HO(2) (nasal version) and Smart Capnoline O(2) (bucconasal version) after extubation. Data were compared with Wilconson test and the intraclass correlation coefficient was calculated. RESULTS The difference PaCO(2) - ETCO(2) was significantly larger in extubated patients compared to intubated patients, which is also confirmed for the bucconasal sensor (intubated patients: 6.6 ± 4.3 mmHg, nasal sensor: 9.3 ± 3.5 mmHg, bucconasal sensor: 15,4 ± 12.9 mmHg). CONCLUSION In the postoperative setting of cardiac surgery, ETCO(2) measurements allow a reliable estimation of PaCO(2) in intubated patients in contrast to measurements in extubated patients. The bucconasal CO(2) sensor does not show more reliable measurements compared to nasal sensors in the postoperative setting of cardiac surgery.

Metabolic acidosis in septic shock: is the Stewart theory the magic bullet?

We read with a great attention the article entitled “Defining metabolic acidosis in patients with septic shock using Stewart approach” [1]. We have some remarks about it. The authors used the Stewart approach to diagnose acid-base disturbances in patients having septic shock. Their reference for metabolic acidosis diagnosis seems to be the calculated standard base excess (SBE). It is interesting to note the lack of correlation between SBE and the strong ion gap (SIG) that represents unmeasured anions. The method used for albumin concentration measurement was different from the 2 methods that we previously compared and that have quite different results [2,3]. They calculated the corrected chloride to diagnose hyperchloremic acidosis. Using our previously published data [3], Fig. 1 shows the reproducibility for chloride and corrected chloride between 2 laboratory analyzers. As expected, the reproducibility between both analyzers was better for chloride (r2 = 0.87; mean difference, 1.7 ± 1.7 mEq/L) rather than for corrected chloride (r2 = 0.68; mean difference, 0.6 ± 2.1 mEq/L). The authors defined an interesting group in which all biologic values were normal except an increased SIG. They stated that SBE missed the presence of unmeasured anions. This increased SIG may also represent the expanded uncertainty of measurement of a calculated parameter that increases with the number of the independent parameters on which it depends (9 for SIG) [3]. We previously discussed the poor value of SIG, particularly its lack of reproducibility [2], a point that was unfortunately not discussed by the authors. What were the clinical characteristics of these patients? Were they different from the other patients besides the lower normal saline administered volume, and what was their prognosis? When using the Stewart approach, the main problem remains the poor reproducibility between analyzers, particularly for calculated parameters. This fact complicates comparisons between studies and may induce a different treatment according to the center. Even if we have to accept a cumulative error in measurement in our clinical practice [4], the used parameters should have a clinical relevant reproducibility to avoid center-dependent patient treatment.

[Benchmark of a high-frequency jet ventilator, the Monsoon™].

OBJECTIVE To test a high-frequency jet ventilator, the Monsoon™ (Acutronic laboratory) on a lung model with regard to delivered tidal volume and tracheal pressure measured through the injector. STUDY DESIGN Benchmark study. MATERIAL AND METHODS The jet ventilator was tested with seven commercially available catheters associated with their connecting line. Recorded data were: the injected volume per minute, the pressure measured in the connecting line between the ventilator and the injector and the difference between the end expiratory pressures (EEP) measured by the ventilator through the injector and the tracheal pressure. Measurements were performed by varying the driving pressure (P(w): 1 to 3 bar), inspiratory time/ventilatory cycle duration ratio (I/T: 0.25 to 0.35 %) and respiratory rate (RR 60 to 300 c/min). RESULTS Whatever the injection catheter used, minute volume increased proportionally with P(w). For each injector and for a given P(w) and I/T, it was possible to determine a RR threshold upon tracheal pressure and EPP gradient largely increased: RR less than 3Hz for I/T less than 0.35 % and P(w) of 3 bar with adult catheters except for Leadercath(®) (RR 2Hz). All the paediatric catheters could be used at a P(w) less than 2 bar, a RR 120 c/min and I/T less than 0.35 %. CONCLUSION Use of a dedicated injector line and a range of settings (RR and I/T rapport) are required to measure an actual EPP through the injector.

Alteration of muscle membrane excitability in sepsis: Possible involvement of ciliary nervous trophic factor (CNTF)

One of the main factor involved neuromyopathy acquired in intensive care unit (ICU) appears to be sepsis. It induces the release of many pro- and anti-inflammatory factors which can directly modulate the muscle excitability. We have studied the effects of one of them: the ciliary nervous trophic factor (CNTF) which is a cytokine released in the early phase of sepsis. CNTF induces a decrease in the sodium current and an increase in resting potential as in sodium inversion potential. These effects could participate to the hypo-excitability observed during sepsis and could be involved in the ICU acquired neuromyopathy. As for TNFα, this early effect is mainly mediated by protein kinase C (PKC) activation and appears to be a reversible post-transcriptional effect.