Invasive Cardiac Output Monitoring and Pulse Contour Analysis. Harshad B. Ranchod Paediatric Intensivist Chris Hani Baragwanath Hospital COPICON 2011

Transcription

1 Invasive Cardiac Output Monitoring and Pulse Contour Analysis Harshad B. Ranchod Paediatric Intensivist Chris Hani Baragwanath Hospital COPICON 2011

2 Introduction The primary goal of haemodynamic monitoring is to assess adequacy of systemic perfusion The assessment of intravascular volume is one of the most difficult tasks in clinical medicine. The question that confronts most intensive care providers on a daily basis is: will fluid increase perfusion to end organs, or will it worsen pulmonary or systemic oedema?

3 Introduction This can be especially true when treating septic patients, where volume expansion is often one of the cornerstones of early resuscitation. SSG 2008 However, clinical studies have demonstrated that only about 50% of unstable critically ill patients will actually respond to a fluid challenge Marik PE, Baram M,et al: Chest 2008; 134: Michard F, Teboul JL: Chest 2002; 121:

4 Introduction Volume overload can have dire consequences such as decreased gas exchange and increased myocardial dysfunction. Data suggests that a patient s cumulative fluid balance affects outcome. Wiedemann HP, et al: N Engl J Med 2006; 354: Vincent JL, et al:. Crit Care Med 2006; 34: Brandstrup B, et al: Ann Surg 2003; 238: Rivers EP: N Engl J Med 2006; 354:

5 Assessment of Volume Status Physical examination Should never be neglected There is no substitute for sequential physical examination to evaluate the effectiveness (or lack thereof) of our interventions and therapeutic decisions. Clinical signs are, however, not as reliable or helpful in assessing intravascular status.

6 Assessment of Volume Status Static measures The central venous pressure (CVP) and pulmonary artery occlusion pressure poorly predict the haemodynamic response to a fluid challenge. Other techniques for assessing intravascular volume have been evaluated: inferior vena caval diameter right ventricular end diastolic volume index global end-diastolic volume index (GEDVI), etc. However, the experience with these have been uniformly disappointing!!

7 Preload Responsiveness Preload of the heart defined as the wall stress at the end of diastole. Volume/ Preload responsiveness Predicts if volume administration (eg. for preload increase) will result in an cardiac output.

8 Preload Responsiveness SV SV Enomoto TM, et al; Crit Care Clin 26 (2010) If the ventricle is operating on the steep part of the curve increasing preload must induce an increase in SV (preload responsiveness). If the ventricle is operating on the flat part of the curve increasing preload will not induce any significant increase in stroke volume (preload unresponsiveness).

9 Preload Responsiveness Fundamentally, the only reason to give a patient a fluid challenge is to stroke volume (SV) and cardiac output (CO).

10 Preload From the example shown, it is clear that physical examination and static markers are not an accurate guide to therapy. Hence, this led to the investigation of dynamic indices for fluid assessment. Enomoto TM, et al; Crit Care Clin 26 (2010)

11 Preload Responsiveness PPV SVV Indices that have been shown to be predictive of fluid responsiveness, include: Systolic Pressure Variation (SPV) and the Pulse Pressure Variation (PPV) derived from analysis of the arterial waveform and Stroke Volume Variation (SVV) derived from pulse contour analysis (Michard F, Teboul JL: Chest 2002; 121: )

12 Preload Enomoto TM, et al; Crit Care Clin 26 (2010) To assess fluid responsiveness, heart-lung interactions during mechanical ventilation have been used (in a number of studies)

13 Haemodynamic Effects of Mechanical Ventilation Early Inspiration Intrathoracic pressure squeezing of pulmonary blood LV preload LV stroke volume systolic arterial blood pressure Late Inspiration Intrathoracic pressure VR to LV and RV LV preload LV stroke volume systolic arterial blood pressure Reuter et al., Anästhesist 2003;52:

14 Variation = Volume responsiveness This variation in pressures between the inspiratory phase and the expiratory phase can be used to identify hypovolaemia and volume responsiveness, and is the basis of indices, including stroke volume variation (SVV) and pulse pressure variation (PPV).

15 These phasic variations are increased in the setting of hypovolaemia for several reasons: 1. The underfilled vena cava and right atrium are more collapsible, and more susceptible to intrathoracic pressure. 2. Since venous return depends on the venous pressure gradient hypovolaemic patients have mean circulating filling pressure more marked venous return with positive pressure ventilation.

16 Reasons for these exaggerated phasic variations in hypovolaemia : 3. Patients who are functioning on the steep portion of the Frank-Starling curve Larger SV with venous return during each positive pressure breath.

17 Pulse Contour Analysis This method of measuring cardiac output is derived from variations in the pulse pressure/ arterial pressure waveform during mechanical ventilation. Is based on the principle that SV can be continuously estimated by analysing the arterial pressure waveform. Includes PPV, SVV and SPV

18 Parameters of Pulse Contour Analysis - SVV The Stroke Volume Variation is the variation in stroke volume over the ventilatory cycle. SV max SV min SV mean SVV = SV max SV min SV mean

19 SVV Difference between the SV during the inspiratory and expiratory phases of ventilation, and Requires a means to directly or indirectly assess SV

20 SVV SV is calculated on physiological relationship between SV and area under systolic portion of the curve. PiCCO, LiDCO and Flotrac monitors uses pulse contour analysis through a proprietary formula to measure cardiac output and SVV

21 Parameters of Pulse Contour Analysis - PPV The Pulse Pressure Variation is the variation in pulse pressure over the ventilatory cycle. PP max PP min PP mean PPV = PP max PP min PP mean

22 Pulse Pressure Variation Arterial pulse pressure is the difference between arterial systolic and diastolic pressure. PPV Based on the physiological relationship between Pulse Pressure and SV

23 Pulse Pressure Variation PPV Directly proportional to LV Stroke Volume. Inversely related to arterial compliance. Assuming that arterial compliance does not change during a mechanical breath respiratory changes in PPV should reflect respiratory changes in SV.

24 Use of PPV and SVV Dynamic indices have repeatedly been shown to be superior to static measures (for determining preload responsiveness in critically ill patients). In controlled mechanically ventilated adults with sepsis, PPV threshold value of 13% allowed to discriminate between : preload responders to volume (PPV > 13%) from Non-responders (PPV <13%). Similar values have been proposed for SVV. Michard F, et al; Am J Resp Crit Care Med 2000; 162: Marik PE, et al; Crit Care Med 2009; 37:

25 Use of PPV and SVV PPV/SVV may be helpful to monitor the haemodynamic effects of volume expansion normalization of PPV with fluid infusion. Lack of improvement of the dynamic markers of preload after fluid challenge may be viewed as promoting oedema (Michard F, Teboul JL: Chest 2002; 121: ) To date very little data on SVV and PPV in critically ill children (Proulx F, et al; Pediatr Crit Care Med 2011; 12: )

26 Use of PPV and SVV Recent meta-analysis revealed that the diagnostic accuracy of the PPV (directly measured) was significantly greater (p<.001) than that for SVV (calculated). These data suggest that the PPV may be the preferred arterial waveform-derived variable for assessment of volume status. Marik PE, et al: Crit Care Med 2009; 37:

27 Limitations of Pulse Contour Analysis 1. Require positive pressure, controlled ventilation Spontaneous Respiratory Efforts (even when supported by the ventilator) Alter the mechanics such that these numbers lose their reliability 2. Sinus rhythm is required. Arrhythmias or frequent extrasystoles result in altered SV unreliable PPV interpretation.

28 Limitations of Pulse Contour Analysis 3. Need Higher Tidal Volume (TV > 8ml/kg) Most of the early data came from patients ventilated with at least 8-10 ml/kg tidal volumes. In a limited series of various critical illnesses: PPV less predictive of volume responsiveness when TV < 8ml/kg than TV > 8ml/kg (De Backer D, et al: (2005) Intensive Care Med 31: ) Preisman S et al. Br J Anaesth. 2005

29 Limitations of Pulse Contour Analysis 4. Requires invasive arterial blood pressure monitoring with a catheter Complications of insertion (bleeding, thrombosis, etc) Catheter related infections. Prone to the same errors in measurement associated with invasive blood pressure monitoring : Requires accurate calibration Air bubbles in the catheter tubing, Excessive tubing length, Kinks in the tubing, Excessively compliant tubing, etc.

30 Limitations of Pulse Contour Analysis 5. A single value never should replace clinical judgment. Eg. A high PPV value in a normotensive patient with evidence of normal tissue perfusion does not mean that person requires volume expansion.

31 Limitations of Pulse Contour Analysis 6. Right Ventricular Dysfunction (or acute cor pulmonale) may have marked RV afterload during inspiration high PPV observed in cases of preload unresponsiveness (false positives).

32 Limitations of Pulse Contour Analysis 7. Other extremes of Ventilation MAY affect PPV 7.1 High PEEP intrathoracic and transpulmonary pressures PPV

33 Limitations of Pulse Contour Analysis 7.2 High Respiratory Rate Trial with 17 hypovolaemic patients ventilated with low (14-16 breaths/minute) and high (30-40 breaths/minute) respiratory rates The authors concluded that respiratory variation in SV and its derivates is affected by respiratory rate, and caution against using these indices as predictors of volume responsiveness at high respiratory rates. (De Backer D, et al. Anesthesiology 2009;100: ).

34 Limitations of Pulse Contour Analysis 7.3 Increase in heart rate (HR) PPV from 21% 4%, and respiratory variation in aortic flow from 23% 6%. (De Backer D, et al. Anesthesiology 2009;100: ).

35 Limitations of Pulse Contour 7.4 HFOV CPAP with wiggle Analysis No distinct inspiratory and expiratory phases. Therefore, only minimal changes in SV would occur during HFOV low PPV (even in fluid responsive patients) (Vincent JL (ed.) Annual Update in Intensive Care and Emergency Medicine 2011; pg )

36 <13% >13% or PPV?

37 3 Categories of Commercially Available Haemodynamic Monitoring Systems : 1) Calibration-dependent pulse contour analysis devices Pulse Contour Cardiac Output (PiCCO) and LiDCO 2) Non-calibrated pulse contour analysis devices FloTrac system Pressure Recording Analytical Method (PRAM) LiDCO rapid 3) Alternative techniques Doppler ultrasound methods Pulse dye densitometry Bioimpedance cardiography, and Partial CO2 rebreathing (NiCO)

38 Means of measuring cardiac output include: Pulmonary artery catheter (PAC) Transpulmonary thermodilution (TD) PiCCO monitor Lithium dilution LiDCO Pulse contour analysis Calibrated (PiCCO, PulseCO system, LiDCO) Non-calibrated (Flo-trac Vigileo system)

39 Pulmonary Artery Catheter (PAC) Used as a gold standard therefore all other methods are compared to this. Uses different methods for calculating CO Thermodilution has been most commonly used to measure cardiac output in the adult population.

40 Complications of PAC Catheter insertion is difficult in smaller patients (5-10kg) and those with aberrant cardiopulmonary anatomy Line-related complications pneumothorax, bleeding or infections Arrhythmias benign and life-threatening ventricular arrhythmias and right bundle branch block PA-related complications rupture, infarction, thrombi, haemorrhage, vegetations.

41 Transpulmonary Thermodilution (TPTD) Controversy surrounding PAC s safety and efficacy has prompted development of newer less invasive techniques. The PiCCO monitor is currently the only commercially available device that uses the TPTD method to measure cardiac output.

42 Transpulmonary Thermodilution (TPTD) The transpulmonary thermodilution technique (TPTD) allows assessment of various indices volumetric preload, cardiac output, and extravascular lung water. without the need to pass a catheter through the right heart.

43 TPTD and PiCCO Need a standard central venous catheter. CVP is usually placed above diaphragm (IJ or SCV) Can be performed using a femoral CVP. and A specialized femoral or axillary arterial catheter with a thermistor at its tip is also required. 3F or 4F arterial catheter is available for femoral artery cannulation in children

44 TPTD and PiCCO A known volume of thermal indicator (ice-cold saline) is injected via a central venous catheter. Depends on body weight (varies from 2mls 20mls) The resulting packet of cooler blood traverses the thorax and is sensed by a thermistor in the femoral or axillary position generating a TD dissipation curve. Cardiac output is then calculated from the curve using the modified Stewart-Hamilton equation for TD. The average result from three consecutive bolus injections is recorded.

45 TPTD and PiCCO Manual calibrations are necessary: To compensate for inter-individual differences in compliance and resistance of the arterial vessel system. Frequent recalibration is necessary during rapidly changing clinical conditions, haemorrhage, shock and vasodilation (Gazit AZ, et al; Ped Crit Care Med 2011;12[Suppl.]:S55 S61)

46 PiCCO PiCCO method may give incorrect thermodilution measurements in patients with intracardiac shunts, aortic aneurysm, aortic stenosis, pneumonectomy, macro lung embolism, and extracorporeal circulation (if blood is either extracted from or infused back into the cardiopulmonary circulation). (Gazit AZ, et al; Ped Crit Care Med 2011;12[Suppl.]:S55 S61)

47 PiCCO It is therefore of limited use in the peri-operative care of children with complex congenital heart defects. May be useful in children with normal cardiac anatomy who present with cardiogenic shock, or in the postoperative care of children after heart transplantation or biventricular repair (Gazit AZ, et al; Ped Crit Care Med 2011;12[Suppl.]:S55 S61)

48 PiCCO Use of this monitor in children is overall simple and requires minimal training. In haemodynamically unstable patients, it requires frequent recalibrations to obtain reasonable accuracy. Both the PiCCO-measured dynamic and static variables were shown to have good correlation with CI and fluid responsiveness. Gazit AZ, et al; Ped Crit Care Med 2011;12[Suppl.]:S55 S61 Wong HR, et al; (Pediatr Crit Care Med 2011; 12[Suppl.]:S66 S68

49 Lithium Dilution / LiDCO Instead of using cold injectate indicator dilution, methods using intravenous lithium have been developed to determine CO (LiDCO). Lithium can be injected via central or peripheral venous catheters Is detected in a standard radial arterial line Negates the need to place a catheter across heart valves (PAC) or to place a femoral or axillary arterial catheter (TPTD). A dye dissipation curve is generated

50 LiDCO The use of this system is problematic due to the complexity of its calibration. The available data support its use in patients with hyperdynamic circulation. However, its validity in patients with low CO has not been studied. Overall, it appears that more data is required before use of this system in critically ill children (Gazit AZ, et al; Ped Crit Care Med 2011;12[Suppl.]:S55 S61)

51 FloTrac Vigileo System Comprised of the FloTrac sensor and a processing display unit (Vigileo). Attempts to determine CO by pulse contour analysis without employing a second technique for calibration. Calibration allows a way to account for changes in vascular compliance, which cannot be easily measured clinically.

52 FloTrac Vigileo System The makers of the Flo-Trac device claim to have solved this calibration problem using continuous self-calibration through an automatic vascular tone adjustment involving complex algorithms based on mean arterial pressure, age, height, weight, and gender of patients.

53 FloTrac Vigileo The FloTrac system, comprised of the Flotrac sensor and a processing display unit (Vigileo). Attempts to determine CO by pulse contour analysis without employing a second technique for calibration. Calibration allows a way to account for changes in vascular compliance, which cannot be easily measured clinically.

54 What else can these monitors do? DO2 = CaO2 X Cardiac Output CO = HR x STROKE VOLUME (SV) PRELOAD CONTRACTILITY AFTERLOAD PPV/ SVV/ GEDVI GEF/CFI/dPmx SVRI

55 Contractility Contractility is a measure of the performance of the heart muscle Is a further important determinant of cardiac output. Some Contractility parameters include: CFI (Cardiac Function Index) GEF (Global Ejection Fraction) dpmx (maximum rate of the increase in pressure)

56 Afterload - SVRI Systemic Vascular Resistance (SVR) Important determinant of afterload. Is the resistance the blood encounters as it flows through the vascular system. SVR index (SVRI) SVR indexed to BSA. Normal = dyn.s.cm-5.m2 SVRI helps to guide catecholamine and volume therapies. Eg. High SVR Vasoconstriction consider : Decreasing vasopressors or adding vasodilator

57 Extravascular Lung Water (EVLW) Reflects the amount of fluid in the interstitium and in the alveolar space. Accepted normal value = < 8ml/kg Paeds : may be up to 20 ml/kg. EVLW > 10ml/kg pulmonary oedema (adults) Is useful for differentiating and quantifying lung oedema

58 EVLW May have prognostic value Reports that in adult patients, mortality increases with increasing volumes of EVLW Sakka SG, et al: (2002) Chest 122: Berkowitz DM, et al: (2008) Crit Care Med 36: EVLWi decreased significantly in survivors already at 24 hours and remained constant thereafter Sustained EVLW > 10ml/kg worse survival. Lubrano R, et al: Intensive Care Med (2011) 37:

59 Conclusion The quest for the holy grail of non-invasive cardiac output assessment continues. NO IDEAL MONITOR Tailor choice of monitor by matching your requirements to information offered by monitor Dynamic measures proving to be more useful modality Our job is to learn what variables to measure, to measure them correctly, to institute effective therapies where available, and to do this with minimum patient risk.

60 Conclusion We need to integrate all the interrelated information at the bedside and try to decide on the best course of management, based on the best available scientific information. Know the limitations of your monitor. Assess data in conjunction with clinical picture. MONITOR DATA IS ONLY AS GOOD AS THE PERSON INTERPRETING IT!!

61 Conclusion We need to integrate all the interrelated information at the bedside and try to decide on the best course of management, based on the best available scientific information. Know the limitations of your monitor Assess data in conjunction with clinical picture MONITOR DATA IS ONLY AS GOOD AS THE PERSON INTERPRETING IT!!

62 Thank you.