Effets de l’halothane sur les gaz du sang et l’équilibre acido-basique artériels chez le rat intact et chez le rat chémodénervé

L’halothane diminue la réponse ventilatoire à l’hypoxie et l’activité des chémorécepteurs artériels périphériques, réalisant une «chémodénervation chimique». Afin d’évaluer le rôle de cette «chémodénervation chimique» dans les modifications de l’équilibre acido-basique et des gaz du sang artériel provoquées par l’halothane, ces paramètres ont été mesurés chez des rats intacts éveillés, puis anesthésiés, et chez des rats chémodénervés, éveillés puis anesthésiés. Le niveau de l’anesthésie pouvant être modifié par la chémodénervation anatomique, l’ED₅₀ inspirée d’halothane a été mesurée chez six rats avant et après chémodénervation anatomique. D’éventuelles modifications hémodynamiques dues à l’halothane et /ou à la chémodénervation anatomique pouvant interférer avec les résultats, la pression artérielle systémique et la fréquence cardiaque ont été mesurées chez six rats intacts éveillés, puis anesthésiés, et chez les six mêmes rats chémodénervés, éveillés puis anesthésiés. Chez neuf rats intacts et chez 19 rats chémodénervés, le pH artériel, la concentration artérielle de bicarbonates, et les gaz du sang artériel (PaO₂ et PaCO₂) ont été mesurés avant et après administration d’halothane. La chémodénervation anatomique ne modifia ni l’ED₅₀ inspirée (1,1%), ni la pression artérielle moyenne et la fréquence cardiaque. Les effets hémodynamiques de l’halothane furent comparables chez les rats intacts et chez les rats chémodénervés. Les modifications des gaz du sang et de l’équilibre acido-basique provoquees par l’halothane chez les rats intacts, et par la chémodénervation anatomique chez les rats éveillés, ne furent pas significativement différentes: diminution significative de PaO₂ et de pHa, augmentation significative de PaCO₂ Chez les rats chémodénervés, l’halothane provoqua une diminution supplémental de PaO₂ et une augmentation supplémentaire de PaCO₂. Le fait que l’halothane et que la chémodénervation anatomique modifient de la même manière les gaz du sang et l’équilibre acido-basique est en faveur de l’action «chémodénervatrice chimique» de l’halothane. Mais les effets additionnels de l’halothane chez l’animal chémodénervé anatomiquement confirment que les effets de l’halothane sur les gaz du sang et l’équilibre acido-basique résultent de multiples points d’impact sur le système respiratoire.     

Effets hémodynamiques comparatifs du sévoflurane et de l'halothane à la concentration télé-expiratoire d'intubation chez le nourrisson

ObjectiveTo compare the cardiovascular changes at the end-tidal concentrations of sevoflurane versus halothane required for tracheal intubation in infants (intubation MAC).Study designProspective randomized study.PatientsThirty-two infants, ASA physical status 1 or 2, scheduled for elective surgery, randomized to receive either halothane or sevoflurane for anaesthetic induction by inhalation.MethodsCardiovascular and echocardiographic data were recorded in both groups at baseline, and at the endtidal concentrations needed for intubation.ResultsIntubation MAC was significantly less with sevoflurane than with halothane in infants. Sevoflurane did not change heart rate (HR) and cardiac index (CI) compared to values when awake. Sevoflurane significantly decreased blood pressure, systemic vascular resistance (SVR) and shortening fraction (SF). Myocardial contractility assessed by stressvelocity index (SVI) and stress-shortening index (SSI) decreased significantly at the intubation MAC, but did not fall into the abnormal range. Halothane caused a greater decrease in HR, SF, SSI, and CI than sevoflurane.ConclusionsSevoflurane decreases cardiac output less than halothane in infants at the intubation MAC, due to a lower end-tidal concentration at intubation MAC and to less effects on haemodynamic variables.     

Effets de la ventilation mécanique avec PEP sur le shunt intracardiaque droit-gauche par un foramen ovale perméable

• Objective :To assess the presence of a patent foramen ovale (PFO) using colloid contrast transoesophageal echocardiography in mechanically ventilated patient with and without PEEP and it repercussion on PaO₂.• Study design :Prospective open before-after trial.• Patients :Forty-nine mechanically ventilated patients with respiratory failure (PaO₂/FiO₂ < 250).• Methods :PEEP assessment before and after adding a PEEP = 10 cmH₂O. At each level of PEEP, semi-quantification of PFO was performed and arterial blood gases were withdrawn at FiO₂ = 1, with 15 min at each level. Semiquantification of the right-to-left intra cardiac shunt through a patent foramen ovale was obtained using the quantity of microbubbles in the left atrium on a basal short axis view.• Results :A PFO was detected in 11 out of 49 patients (22 %). A right-to-left shunt developed in one and worsen in three patients when PEEP was added. In patients without a PFO, PaO₂ increased significantly (from 119 ± 10 mmHg to 145 ± 10 mmHg, P < 0.001). In patients with a PFO, non significant changes occurred (118 ± 15 mmHg to 120 ± 17 mmHg). After adding PEEP, the difference between the two groups was significant (ANOVA, P < 0.05). Moreover, a PFO was present during the whole respiratory cycle in two out of 11 patients. These 2 patients exhibited a PaO₂ < 100 mmHg with or without PEEP.• Conclusion :This study suggests that mechanical ventilation with PEEP enhances an intracardiac right-to-left shunt through a PFO. This condition is responsible for the lack of improvement in blood oxygenation when PEEP is added. When a PFO is present all over the respiratory cycle, or when the oxygenation is worsened with PEEP, this positive pressure ventilation should be avoided. The deleterious consequences of mechanical ventilation on venous return may be minimized by partial ventilation and weaning from ventilator.     

Ostéotomie en roseau du radius chez l’enfant dans la paralysie de la pronation du plexus brachial obstétrical

We report our experience and results in the use of reed pronating osteotomy in supination deformities secondary to obstetrical brachial plexus injury. This retrospective study involved 11 patients with paralytic supination of the forearm due to a brachial plexus injury. Other causes of paralytic supination were excluded. The surgical technique consisted of a proximal osteotomy of the ulna fixed by an intramedullary nail and a stable elastic reed osteotomy of the radius. The minimum postoperative follow-up was 2 years. Four boys and seven girls mean aged 8 years (5–12) were operated on between 2000 and 2010. The mean preoperative supination was measured at 63°. The final position average pronation was 37°. Loss of pronation was measured at 15°. No complication was observed. With a mean follow-up of 4 years (2–12), the reed osteotomy of radius associated with a proximal transverse osteotomy of ulna has proven itself effective for correction of paralytic supination of the forearm without complication or reoperation.     

Actualités sur la prise en charge de l’anémie et de la carence martiale du dialysé

The Kidney Disease Improving Global Outcomes (KDIGO)-2012 on the treatment of anemia emit suggestions (which differ from recommendations) based on a scientific evidence of low level. The first rule is no harm; physicians must take into account the profile of the patient and its associated morbidities and remember on the potential risks to begin a treatment by erythropoiesis stimulating agents (ESA) (thrombosis of arteriovenous fistula, hypertension, stroke). All correctable causes of anemia other than erythropoietin deficiency should be actively sought. It is necessary to individualize the treatment by ESA and assess the clinical improvement expected. The ESA will be used in the following way: initiate at 10 g/dL of hemoglobin level with the aim of 11.5 g/dL, without exceeding 13 g/dL. In case of ESA resistance, it seems suitable to assess the risks and benefits of ESA versus blood transfusion. The ERBP-2013 have endorsed the KDIGO-2012 except the proposals dealing with the treatment by IV iron. The use of intravenous iron must be more cautious in the future taking into account the results of a recent French study published in the American Journal of Medicine showing the high frequency of iron overload at quantitative hepatic MRI among haemodialysis patients receiving iron IV following the current guidelines. It is appropriate to use oral iron in first intention as recommended by the ANSM (French Drug Agency) in a recent information note and respect the dosage regimen of the label. The realization of a quantitative hepatic MRI to evaluate iron overload and monitor the treatment by iron IV must also be considered on a case by case basis.     

Cathétérisme artériel et mesure invasive de la pression artérielle en anesthésie-réanimation chez l'adulte

A group of 13 experts appointed by the French Society of Anaesthesia and Intensive Care has produced the following guidelines for arterial catheterisation and invasive measurement of systemic arterial blood pressure in adults. Teflon ® or polyurethane catheters are recommended with a maximal size of 18 gauge for femoral and axillary arteries and 20 gauge for the others. For small arteries (radial and pedious arteries) a maximal length of 3–5 cm should be preferred. The benefit of heparin-coating is not documented. Incorporation of salts for radiopacity is useless and increases thrombogenicity.Use of a flush device with a constant flow of 2 mL·h⁻¹ and a fast flush valve connected to normal saline under pressure is recommended. Manual intermittent flushing with a syringe is contra-indicated. Addition of heparin (2500 IU·500 mL⁻¹ of flush solution) increases the duration of catheter patency and is recommended for catheterisations of more than 24 h duration.Ready for use devices are to be preferred. Distortion of pressure wave may be minimized by employing low volume, low compliance, low resistance devices. The number of connections should be as low as possible and all of Luer-lock type. The stopcocks should be clearly indentified to minimize the risk of accidental intra-arterial injection. The device should be transparent for disclosure of bubbles, which lead to waveform distortion.For catheter placement the operator should follow the usual preparation as for any aseptic surgical procedure with cap, mask, gloves and sterile towel. The insertion site is prepped either with chlorhexidine or povidone-iodine. In the conscious patient, local anaesthesia by injection and/or topical application (EMLA ®) is recommended. Direct arterial puncture should be preferred rather than transfixion. Catheterisation of deep vessels is facilitated by Seldinger technique, which is recommended whatever the site of placement when long term monitoring and/or difficulties of insertion are foreseen.The radial artery is the site of choice for elective cases. The non-dominant hand should be preferred. Puncture must be preceded by assessment of adequacy of the collateral flow by the Allen test.The femoral artery is a valuable site for emergency situations. Before catheterisation, the artery should be auscultated for a murmur. Puncture of a vascular prosthesis is contra-indicated.The dressing should be changed every four days only. Sites of blood withdrawal should be manipulated with compresses soaked with chlorhexidine or povidone-iodine.The arterial catheter is only changed in case of evidence of local infection or ischaemia.The catheter removal should be considered as an aseptic surgical procedure. The catheter completeness has to be checked. A systematic culture of the catheter is not required.     

Effets du propofol sur la courbe de dissociation de l'oxyhémoglobine in vivo et in vitro

This study assessed in vivo and in vitro the effects of propofol on the affinity of hemoglobin for oxygen in seven ASA 1 adults. For the in vivo study, venous blood samples were withdrawn before and after premedication, after the injection of 2.5 mg · kg⁻¹ of propofol and after 15 minutes of maintenance at an infusion rate of 0.2 mg · kg⁻¹ · min⁻¹. For the in vitro study, propofol was added to the blood withdrawn before premedication in order to obtain two samples at a concentration of 1 μg · mL⁻¹ and 2 μg · mL⁻¹ respectively. Propofol changed neither in vivo, nor in vitro, the P50 and the number of Hill indicating the angle of the slope of the dissociation curve, nor in vivo the concentration of 2,3-DPG.