心电图和中心静脉置管

ELECTROCARDIOGRAPHY&CENTRAL VENOUS CATHETERIZATION,钟静,ELECTROCARDIOGRAPHY,lead IIthe largest P wave voltages of any surface lead approximately 60 from the right arm to the left leg, which is parallel to the electrical axis of the atriaenhances the diagnosis of arrhythmias and the detection of inferior wall ischemia,ELECTROCARDIOGRAPHY,Lead V5 lies over the fifth intercostal space at the anterior axillary linea good compromise for detecting anterior and lateral wall ischemiaa true V5 lead is possible only on operating room ECGs with at least five lead wiresa modified V5 can be monitored by rearranging the standard three-limb lead placement,ELECTROCARDIOGRAPHY,Leads II and V5 should be monitored simultaneouslyThe preferred lead for monitoring depends on the location of any prior infarction or ischemia Esophageal leads are even better than lead II for arrhythmia diagnosis but have not yet gained general acceptance in the operating room,Esophageal leads,食管导联心电图：通过食管电极导管从心脏背部描记到的心电图食管电极位于食管中段，高度在房室沟水平，相当于左房后壁后方约0.5cm距离，探测到P波的高度大约比体表心电图P波增大35倍 1906年Cremer首先成功地在食管内记录到心电活动,Esophageal leads,Numerous studies have confirmed the usefulness of this techniqueThe unipolar E-ECG was first only used for detecting T-waves as well as premature systolic beats In the 70-ies, probes with bipolar electrodes were used for the first time to analyze atrial arrhythmias,1 心房上部2 心房中部3 心房下部4 心室上部,Esophageal leads,ELECTROCARDIOGRAPHY,How to lower the skins electrical resistance?conductive gelcleansing the site with alcohola degreasing agentmechanically exfoliating the superficial skin layer,Clinical Application,arrhythmiasmyocardial ischemiaconduction abnormalitiespacemaker malfunction,Clinical Consideration,Simulate arrhythmias patient or lead-wire movementuse of electrocautery60-cycle interferencealso called electrical interference, AC interference, is caused by electrical power leakageand faulty electrodes,Clinical Consideration,Digital readout of heart rate may be misleading because of monitor misinterpretation of artifacts or large T wavesoften seen in pediatric patientsas QRS complexes Monitoring filters incorporated into the amplifier may lessen artifacts,How to diagnose myocardial ischemia?,Lead to distortion of the ST segment and impede the diagnosis of ischemiaTo interpret ST-segment changes properly, the ECG must be standardized so that a 1-mV signal results in a deflection of 10 mm on a standard strip monitor Automated ST-segment analysis increases the sensitivity of ischemia detection Unfortunately, the efficacy has not been documented,How to diagnose myocardial ischemia?,A flat or downsloping ST-segment depression exceeding 1 mm, 60 or 80 ms after the J point (the end of the QRS complex)Particularly in conjunction with T wave inversion ST-segment elevation with peaked T wavesWolffParkinsonWhite syndrome, bundle branch blocks, extrinsic pacemaker capture, and digoxin therapy may preclude the use of ST-segment information,Attention,The audible beep associated with each QRS complex should be loud enough to detect rate and rhythm changes when the anesthesiologists visual attention is directed elsewhere,CENTRAL VENOUS CATHETERIZATION,Indications,monitoring central venous pressure (CVP)administration of fluid to treat hypovolemia and shockinfusion of caustic drugs and total parenteral nutritionaspiration of air emboliinsertion of transcutaneous pacing leadsgaining venous access in patients with poor peripheral veins,Contraindications,Renal cell tumor extension into the right atrium or fungating tricuspid valve vegetationsInternal jugular vein cannulation is relatively contraindicated in patients who are receiving anticoagulants or who have had an ipsilateral carotid endarterectomybecause of the possibility of unintentional carotid artery puncture,Techniques & Complications,The catheters tip lies just above or at the junction of the superior vena cava and the right atrium Inspiration will increase or decrease CVPbecause this location exposes the catheter tip to intrathoracic pressuredepending on whether ventilation is controlled or spontaneous CVP should be measured during end expiration,Techniques & Complications,Catheterization of the subclavian vein is associated with a significant risk of pneumothorax during insertion line-related infection the longer the catheter stays in place The right internal jugular vein provides a combination of accessibility and safety Left-sided catheterization increases the risk of vascular erosion, pleural effusion, and chylothorax,Cannulation techniques,a catheter over a needle (similar to peripheral catheterization)a catheter through a needle (requiring a large-bore needle stick)a catheter over a guidewire (Seldingers technique),Right internal jugular cannulation,Patient position: trendelenburg positionto decrease the risk of air embolism and to distend the internal jugular vein Full aseptic techniqueincluding sterile gloves, mask, bactericidal skin preparation, and sterile drapes,Right internal jugular cannulation,The two heads of the sternocleidomastoid muscle and the clavicle form the three sides of a triangle A 25-gauge needle is used to infiltrate the apex of the triangle with local anesthetic The internal jugular vein is found along the medial border of the lateral head of the sternocleidomastoidToward the ipsilateral breast nipple at an angle of 30 to the skin Aspiration of venous blood confirms the veins location,Right internal jugular cannulation with seldingers technique,Right internal jugular cannulation,The possibility into the carotid artery can be decreased by transducing the vessels pressure waveformcomparing the bloods color or PaO2 with an arterial sample An 18-gauge thin-wall needle is advanced along the same path as the locator needle When free blood flow is achieved, a J-wire with a 3-mm-radius curvature is introduced The needle is removed, and a pliable silastic catheter is advanced over the wire,Right internal jugular cannulation,The guidewire is removed, with a thumb placed over the catheter hub to prevent aspiration of air until the intravenous catheter tubing is connected to it The catheter is then secured and a sterile dressing is applied Correct location is confirmed with a chest radiograph The catheters tip should not be allowed to migrate into the heart chambers Fluid-administration sets should be changed every 72 h,Complications,InfectionAir or thrombus embolismArrhythmias (indicating that the catheter tip is in the right atrium or ventricle)HematomaPneumothorax, hemothorax, hydrothorax, chylothoraxCardiac perforation, cardiac tamponadeTrauma to nearby nerves and arteriesThrombosisSome of these complications can be attributed to poor technique,CVP,CVP appro