Application of methods for hemodynamic monitoring in critical cardiac pathology. Experimental model for assessment of hemodynamics

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1 835 Application of methods for hemodynamic monitoring in critical cardiac pathology. Experimental model for assessment of hemodynamics Julija Braždžionytė, Andrius Macas 1, Edmundas Širvinskas 1 Clinic of Cardiology, 1 Institute for Biomedical Research, Kaunas University of Medicine, Lihuania Key words: hemodynamics, intensive cardiology, non-invasive methods for hemodynamic assessment. Summary. Hemodynamic assessment of critically compromised patients with cardiac pathology is one of the goals of recent diagnostics and treatment strategies. Different methods for assessment of hemodynamics are applied in clinical practice. However, applied methods (invasive and noninvasive) have specific advantages and disadvantages. These are discussed in the article. First experience of experimental model for assessment of hemodynamics in laboratory conditions is analyzed in the article. In the year 2002 it was explored a possibility to use standard procedure to evaluate hemodynamics for laboratory animals in Kaunas University of Medicine. It were selected 6 laboratory animals of different weight and sex. 7 measurements of hemodynamics were performed. Standard methodics were successfully applied in the experimental model. Results, method limitations and recommendations for further studies are presented in the article. Introduction Assessment of central hemodynamics (CH) in cardiac emergencies is important for selection of optimal diagnostic and treatment tactics, evaluation of treatment efficacy and patient condition changes. Assessment of CH is an inseparable part of patient monitoring during extent surgery (26) and postoperative period. Opportune evaluation of hemodynamics for patients with acute cardiac pathology allows starting of adequate treatment and monitor efficacy of treatment, cardiovascular function and its changes, as well as status of homeostasis (1,6,10-13,24). Invasive methods remain as gold standard for evaluation of CH. Noninvasive methods are kept as an alternative (1). Standard and recently introduced to clinical practice methods of CH assessment are discussed in the article, as well as their application in intensive cardiac care. First experience of experimental CH assessment for laboratory animals is presented in the article as well as methodics of experimental model, results and their interpretation. Methods for assessment of central hemodynamics and their application in intensive cardiology There are two principle methods to assess CH in clinical practice: 1. Invasive (direct), 2. Noninvasive (blood flowmetry in main vessels central flowmetry) (8). Both methods might be applied in intensive cardiac care, but each of them has specific advantages and disadvantages in case of different cardiac or accompanying pathology. Invasive methods for assessment of central hemodynamics Invasive method for assessment of CH (IACH) remains as basic method to compare all CH assessment ones (1,6). IACH allows obtain following data (directly): a) Pressures of right parts of the heart (pressure of right atrium, systolic and diastolic pressures of the right ventricle), b) Systolic and diastolic pressures of the pulmonary artery and pulmonary capillary wedge pressure, c) Stroke volume, cardiac output (CO). Other parameters (systemic vascular resistance, preload and afterload, myocardial contractility and fluid electrolyte disbalance are estimated indirectly, according to above mentioned measurements and additional data. IACH isn t a united method and CO measurements reflect these differences. Most precise method for Correspondence to J.Braždžionytė, Clinic of Cardiology, Kaunas University of Medicine, Eivenių 2, 3007 Kaunas, Lithuania

2 836 Julija Braždžionytė, Andrius Macas, Edmundas Širvinskas evaluation of CO is searched up to now, but recently are used following methods: 1. Fick, 2. Dye dilution, 3. Intermittent thermodilution, 4. Continuous thermodilution. Fick s method is based on estimation of arterial and mixed venous saturation evaluation. This method is recommended for patients with low CO. This method isn t precise and gives method errors when CO is high. It is indicated direct correlation between Fick and intermittent thermodilution methods (r = 0.961) (2). Dye method is used as well, but its application is less common in clinical practice. This was the main method for CO estimation before thermodilution one was introduced into clinical practice. Indocyanine green is injected to central vein and dye dilution is evaluated in the artery after the certain period. Catheterization of central vein and artery is required for investigation. Intermittent thermodilution is most widely spread method. Cold fluid is injected through proximal lumen of the pulmonary artery catheter (ex. Swan - Ganz catheter, PAC) with speed of 2.5 ml/s. Thermistor in the distal end of the catheter registers temperature differences. Continuous thermodilution method includes couple modifications. Some authors method of continuous thermodilution describe lasting interval CO monitoring by the help of intermittent thermodilution. Catheter remains in the pulmonary artery for a long time. The method introduced to clinical practice allowing performance of lasting uninterrupted CH assessment is following: specific PAC are used (two thermistors T1, T2, placed with 10 cm distance form each other. T1 registers the basic temperature in the pulmonary artery and is placed upstream from the tip of PAC, closer to pulmonary artery valve. Coil (heating element) is placed under the T1 and increases the temperature of the blood. Distal T2 thermistor registers changes of temperature. Aim to evaluate required energy amount in order to increase blood temperature in pulmonary artery for 1 C. This method allows performing continuous measurements of CH, is accurate, as well as facilitates work of investigator. Cold solution isn t used this way excluding possible cardiac arrhythmias. Noninvasive methods for assessment of central hemodynamics Three methods of noninvasive methods for assessment of central hemodynamics are applied in the clinical practice: 1. Flowmeters (central flowmetry) blood flow is measured in the aorta. Method is based on transesophageal ultrasonography of the heart combination of M and Doppler modes: M mode to assess diameter of aorta, Doppler signal to assess blood flow (1,3,9,15,17,20). 2. Thoracic electrical impedance measurement (impedance cardiography). 3. CO measurement by monitoring CO2 in the expiratory gas mixture ( rebreathing methodics) (19,29). Latter two methods are devoted for measurement of CO. Central flowmeters, devices measuring blood flow by the help of transesophageal ultrasonography, are used most commonly. CH is evaluated by measurement of blood flow in the descending aorta. (16,23). Data obtained by the help of central flowmetry (CF) are following: a) Aortic blood flow in the descending aorta, b) Stroke volume in the descending aorta, c) Left ventricular ejection time, d) Acceleration, e) Peak velocity, f) Aortic diameter, Other indices are derived or calculated: systemic vascular resistance and cardiac index. CO and stroke volume are delivered based on precondition that stroke volume in the descending aorta makes 70% of total stroke volume (4,5,18,21,22,28). First flowmeters didn t have M-mode and measurements were unacceptable due to reliability reasons (Table 1) (3). Comparison of methods for assessment of central hemodynamics Choice of CH assessment methods for patients with acute cardiac pathology is still discussed. As it was mentioned, IACH remains gold standard for investigation of CH. IACH as invasive method gives risk of complications (14,25). In this aspect noninvasive methods have superiority. Noninvasive methods do not raise complications conditioned by IACH. But even popular CF has limitations. This method is easily applied during anesthesia. On the other hand, additional sedation is needed to apply CF for patients in coronary care units, where patients aren t intubated and consciousness isn t deranged. This makes some difficulties, especially when continuous lasting monitoring is expected (22). In this case care of PAC is more convenient. Disadvantages of IACH method are conditioned by two reasons:

3 Application of methods for hemodynamic monitoring in critical cardiac pathology 837 Table 1. Parameters obtained by the help of different methodics Rodiklis IACH Impedance CO 2 Transesophageal cardiography rebreathing ultrasonography methodics Continous CO** Stroke volume** Contractility of left ventricle** + + Ejection time of left ventricle* + Flow parameters * + Lung fluid status* + Intrathoracic blood volume** + Assessment of pressures* + ETCO 2, alveolar ventilatition, lung + compliace, airway resistance* * measured, ** estimated indirectly. ETCO 2 end-tidal CO 2 partial pressure. 1. Of importance, IACH complications are commonly mentioned, but relatively rare and are not conditioned by catheter itself, but technique of central vein catheterization (pneumothorax, hemothorax, infection). Some complications are related to PAC (arrhythmias, damage of pulmonary artery, tricuspid/pulmonic valves. Some complications were eliminated after the improvement of PAC technology: probability of clot occlusion of the catheter and pulmonary embolism was reduced after implementation of heparin - covered PAC (25). 2. Other disadvantages are conditioned by method itself (27,30): a) Self-wedging of the PAC. Thermistor occlusion by the walls give erroneous CO results; b) Incorrect positioning of the transducers, correct height is critical to accurate pressure measurement; c) Air in the system, this results in damping of the waveform and erroneous pressure values; d) Calibration errors; e) Timing of injection with the respiratory cycle is essential and can result in an error up to a 10%; f) Infusions running in a high rate dilute the indicator and result in false readings; g) Inaccurate estimation of certain variables of CO formula (temperature of injectate and body, injectate volume and etc.); h) Anatomical abnormalities affect the readings (such as tricuspid regurgitation); i) Cold injectate sometimes cause the slowing of the heart rate, this phenomenon also brings into question the CO result. Of importance, various methods for assessment of CH allow to estimate spectrum of derivative parameters (systemic vascular resistance, cardiac index, etc.). It is important to notice, that IACH allows monitoring pressures in the cava vein, right atrium, ventricle and pulmonary capillary wedge pressure. This feature allows monitoring fluid balance. Equivalent parameters might be estimated by the help of CF. It is acknowledged that reliability of measurements of IACH has superiority over other methods. In different studies IACH was used as a reading measurement for estimation of noninvasive methods precision. Correlation coefficient between IACH and CF methods in CO measurements was in different studies (17). Some indicate smaller reliability of noninvasive methods and depends on investigator experience, skills and technique (8). CF isn t accurate in case of atrial fibrillation, presence of air in the mediastinum and pathology of aortic valve. Application of other noninvasive methods (thoracic electrical impedance measurement, CO measurement by monitoring CO2 in the expiratory gas stream) is limited due to method s trustworthiness and inconvenience of method application (tracheal intubation is needed for CO2 rebreathing methodics).

4 838 Julija Braždžionytė, Andrius Macas, Edmundas Širvinskas There are no united recommendations for CH assessment methods application in intensive care units for patients with acute cardiac pathology. Analysis of experimental model for assessment of hemodynamics Experimental research study with laboratory animals was performed in the year 2002 in order to ascertain possibility of CH assessment in experimental model. Research study was handled following requirements of good laboratory practice (Guide for the Care and Use of Laboratory Animals. NIH Publication No ). Aim of study The aim of the study was investigation of possibility to apply standard IACH methodics and instruments (PAC) for laboratory animals in experimental model. Analysis of breathing cycles influence to CH parameters was task of study as well. Methods and study material Six adult dogs of different weight and sex were selected (4 males and 2 females). Mean weight of the laboratory animal was 13.5±3.8 kg. Seven investigations of CH carried out (investigation was performed three times for one patient, with time interval of 2 hours between measurements; investigation wasn t performed for one patient, due to anatomical peculiarities, id est small weight of the patient). Experimental protocol and data acquisition Anesthesia was started at the beginning of the experiment by administration of intramuscular diazepam (1 mg/kg) and ketamine injection (10 mg/kg). During the experiment anesthesia was maintained with continuous infusion of ketamine (5-10 mg/kg/h) and sodium thiopental (up to 4mg/kg/h). Muscle relaxants (pancuronium) were administered by intermittent regimen. Cannulation of femoral vein with 2.7 mm diameter valvular introducer was made at the beginning of the experiment. Assessment of hemodynamics was carried out applying 2.3 mm (7F) diameter standard PAC of 110 cm length. Hemodynamic data were registered with Helige device for hemodynamic monitoring together with esophageal ECG. Pressure waveforms were analyzed in the inferior cava vein, right atrium (systolic and diastolic), right ventricle (systolic and diastolic), pulmonary artery (systolic and diastolic), pulmonary capillary wedge (PCW) during the experiment (Fig. 1 a, b). Main reasons affecting accuracy and errors were analyzed in the experimental model. Standard clinical measurement of hemodynamics was modulated for non-relaxed and relaxed investigative. Results During the study, it was established that application of the standard PAC is optimal for laboratory studies with laboratory animals. PAC of 2.3 mm diameter (7F) is suitable for investigation of laboratory animal over 12 kg of weight. Introduction (leading-in) of PAC for animal of less weight is complicated due to anatomical reasons (attempts to introduce PAC in order to investigate laboratory animal of 8 kg of weight have failed). Standard clinical investigation of hemodynamics was modulated for non-relaxed patient (laboratory animals were adequately anaesthetized, without administration of muscle relaxants). Periodic pressure fluctuations were registered, when PAC reaches thoracic region (inferior cava vein, right atrium and ventricle, pulmonary artery, as well as pulmonary capillary wedge pressure), related to breathing cycles. Pressure changes were registered in the background of spontaneous breathing (Fig. 2a), for relaxed laboratory animals during artificial ventilation with large volumes (Fig. 2b), and during spontaneous breathing recovery with remnant action of muscle relaxants (Fig. 2c). Fluctuation of pressures might be eliminated by administration of the muscle relaxants or disconnecting ventilator (for short time), as well as this is achieved after the opening of the pleura (sternotomy or lateral thoracotomy). Fluctuation of pressures of lower amplitude starts after the discontinuation of muscle relaxants administration (total analgesia is continued), when cycles of spontaneous breathing appear, in comparison with the fluctuation, which appears during artificial ventilation. Breathing cycles influence measurements of patients CO in the clinical practice as well and this is one of the reasons of measurement errors. Digital processing of the signal might eliminate these errors. Discussion Investigation of CH might be successfully performed using invasive and noninvasive methods. Reliability of IACH and CF is acknowledged (17). Choice of proper method for CH assessment for intensive care patients, with acute cardiac pathology remains an urgent problem (1). Some authors indicate successful application of noninvasive methods for assessment of CH, but IACH

5 Application of methods for hemodynamic monitoring in critical cardiac pathology 839 PA PCW (1 cm 10 mmhg) PA pulmonary artery waveform. PCW pulmonary capillary wedge waveform. Fig. 1a. Pulmonary arterial and pulmonary capillary wedge waveforms encountered during the flotation of a pulmonary artery catheter RV PA PA PA P PCW PA pulmonary artery waveform. PCW pulmonary capillary wedge waveform. RV right ventricle waveform. PCW PCW (1 cm 10 mmhg) Fig. 1b. Right ventricle, pulmonary arterial and pulmonary capillary wedge waveforms encountered during the insertion of a pulmonary artery catheter still remains as protocol one (1,4). It is observed tendency to introduce noninvasive methods for hemodynamics assessment for patients with acute cardiac pathology, especially when hemodynamics is stabile. Invasive methods for assessment of CH are recommended to be applied if cardiac pathology is severe, hemodynamics is unstable, or during the preparation patients for surgery. Noninvasive methods for assessment of CH induce fewer complications, but have relatively smaller accuracy and depend on practical skills of the investigator. CF, most spread method among noninvasive ones, should be applied for sedated patient in order to reduce uncomfortable feelings during the procedure (3). Recently a possibility to combine different methods for CH assessment and set of individual indications is discussed. Implementation of experimental model, using standard methodics, gives an opportunity to modulate different clinical conditions. This helps to evaluate and clarify possible errors and their reasons. Monitoring of central hemodynamics might be carried out by the help of other methods (echo, analysis of breathing gas) as well, but this requires additional skills of the investigator and means (7). Conclusions Application of invasive and noninvasive methods for assessment of hemodynamics for patients of intensive care unit is acceptable. Main advantage of noninvasive methods for assessment of hemodynamics is their safety, while that of invasive ones being sensitiveness and peculiarity. Application and reliability of noninvasive methods for assessment of central hemodynamics should be further investigated, seeking for co-application of invasive and noninvasive methods for assessment of central hemodynamics Application of standard PAC and introduction technique is acceptable for investigation of laboratory animals, permitting further experimental investigations of central hemodynamics.

6 840 Julija Braždžionytė, Andrius Macas, Edmundas Širvinskas Insp. Exp. Insp. inspiration. Exp. expiration. (1 cm 5 mmhg) Fig. 2a. Pressure changes in the right ventricle induced by spontaneous breaths, conditioning changes of intrathoracic pressure Exp. Insp. Insp. inspiration. Exp. expiration. Insp. (1 cm 10 mmhg) Fig. 2b. Pressure changes in the right ventricle induced by lung ventilation DPV ALV SA SR ALV lung ventilation cycles. SR cycles of spontaneous breathing. (1 cm 5 mmhg) Fig. 2c. Pressure changes in the right atrium induced by lung ventilation and spontaneous breaths

7 Application of methods for hemodynamic monitoring in critical cardiac pathology 841 Hemodinamikos tyrimo metodai, naudojami ūminei kardialinei patologijai tirti (hemodinamikos tyrimo eksperimentinis modelis) Julija Braždžionytė, Andrius Macas, Edmundas Širvinskas Kauno medicinos universiteto Kardiologijos klinika, Biomedicininių tyrimų institutas Raktažodžiai: hemodinamika, intensyvioji kardiologija, neinvazinis hemodinamikos tyrimas. Santrauka. Hemodinamikos tyrimai ūminės kardialinės patologijos atvejais padeda stebėti ir įvertinti ligonio būklę, monitoruoti gydymo efektyvumą, palyginti gydymo metodus. Hemodinamika tiriama įvairiais metodais. Šiame straipsnyje apibendrinami šiuo metu vartojami invaziniai ir neinvaziniai hemodinamikos tyrimo metodai. Straipsnyje analizuojama pirmoji patirtis naudojant eksperimentinį hemodinamikos tyrimo modelį metais Kauno medicinos universitete eksperimente tirta standartinių invazinių hemodinamikos tyrimo metodų panaudojimo galimybė laboratoriniams gyvūnams. Tyrimams atrinkti šeši įvairaus svorio laboratoriniai gyvūnai, atlikti septyni hemodinamikos tyrimai. Tyrimo metu invaziniai hemodinamikos tyrimai sėkmingai atlikti naudojant standartinę metodiką. Straipsnyje aprašomi tyrimo duomenys, metodo panaudojimo apribojimai bei rekomendacijos tolesnėms studijoms. Adresas susirašinėjimui: J.Braždžionytė, KMU Kardiologijos klinika, Eivenių 2, 3007 Kaunas References 1. Bernardin G, Tiger F, Fouche R, Mattei M. Continuous noninvasive measurement of aortic blood flow in critically ill patients with a new esophageal echo-doppler system. J Crit Care 1998;13(4): Beyer ME, Hoffmeister HM, Seipel L. Hemodynamic and inotropic effects of antiarrhythmic drugs used to treat paroxysmal supraventricular arrhthmias. Int J Angiol 1998;7: Boulnois J, Pechoux T. Non-Invasive Cardiac Output Monitoring by Aortic Blood Flow Measurement with the Dynemo JCMC 2000;16: Cariou A, Monchi M, Joly LM, Bellenfant F, Claessens YE, Thebert D, et al. Non-invasive cardiac output monitoring by aortic blood flow determination; evaluation of the Sometec DYNEMO 3000 system. Crit Care Med 1998;26(12): Cariou A, Monchi M, Thebert D, Joly LM, Brunet F, Dhainaut JF. Evaluation of a new non-invasive hemodynamic monitoring system by aortic blood flow determination. Intensive Care Med 1997;23(1):A Connors AF, Speroff T, Dawson NV, Thomas C, Harrell FE, Wagner D, et al. The effectiveness of right heart catheterization in the initial care of critically ill patients. JAMA 1996;276: Doi M, Koji M, Ikeda K. Frequently repeated cardiac output measurements during anesthesia. J Clin Monit 1990;6: Estagnasie P, Djedaini K, Mier L, et al. Measurement of cardiac output by transesophagial echocardiography in mechanically ventilated patients: Comparison with thyermodilution. Intensive Care Med 1997;23:753:9. 9. Galimberti G, Rinaldi A, Iscra F, Berlot G, Gullo A. Kneechest position: Cardiovascular effects evaluated with transesophageal echodoppler. Brit J Anesth 1997;78(1):A Gueugniaud PY, Abisseror M, Moussa M, Godard J, Petit P, Dodat H. The hemodynamic effects of pneumoperitoneum during laparoscopic surgery in healthy infants: assessment by continuous esophageal aortic blood flow echo-doppler. Anesth Analg 1998;86: Gueugniaud PY, Muchada R, Bertin-Maghit M, Griffit N, Petit P. Non-invasive continuous hemodynamic and Pet CO 2 monitoring during preoperative cardiac arrest. Can J Anesthesiol 1995;42(10): Gueugniaud PY, Vaudelin G, Bertin-Maghit M, et al. Comparison of the myocardial effects of desflurane and isofulurane in health patients: assessment by continuous esophageal aortic blood flow echo-doppler. Brit J Anesth 1998;81: Hensley FA, Martin DE. The practice of cardiac anesthesia. Little, Brown and Company, Iberti TJ, Fischer EP, Leibowitz AB, Schecter CB, Fischer EP, Sliverstein JH. A multicenter study of physicians knowledge of the pulmonary artery catheter. Pulmonary Artery Catheter Study Group. JAMA 1990;264: Klein G, Emmerich M, Maisch O, Dummler R. Clinical evaluation of non-invasive monitoring Aortic Blood Flow (ABF) by a transesophageal echo-doppler device. Anesthesiology 1998;89(3A):A Lavandier B, Cathignol D, Muchada R, et al. Non-invasive aortic blood flow measurement using an intraesophageal probe. Ultrasound in Med and Biol 1985;1,3: Lavandier B, Muchada R, Chignier E, Fady JF, Birer A, Cathignol D. Assessment of a potentially non-invasive method for monitoring aortic blood flow in children. Ultrasound in Med and Biol 1991;17: Muchada R. Continuous measurement of the systolic time intervals integrated on a hemodynamic profile. Successful method to monitor left ventricular function. Recent Advances in Anesthesia, Pain, Intensive Care and Emergency. Edit. A.P.I.C.E. Trieste 1996; Muchada R. Relationship between the PET CO 2 and the hemodynamic parameter. Recent Advances in Anesthesia, Pain,

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