Hemodynamic monitoring in the critically ill patient: overview of symposium PAUL W. ARMSTRONG,* MD; RONALD S. BAIGRIE,f MD (EDITORS)
Hemodynamic monitoring as an adjunct to the care of the critically ill patient is but one of a number of technologic advances made available to the practising physician in the past decade. It is an invasive technique characterized by the placement and maintenance of intracardiac and intravascular catheters for the continuous recording of pressure and the intermittent determination of flow. The information provided by this technique has had a major impact on therapeutic
This symposium will be published in the fall of 1980 by Harper and Row Publishers, Inc., Hagerstown, Maryland. For this reason reprints of the entire symposium will not be avail. able. However, reprints of the Individual papers will be available from the authors.
The material included in this issue of the Journal has been divided into two parts. The first provides the historical and physiological background of hemodynamic monitoring and a discussion of the equipment and techniques used, and concludes with a discussion of how this approach complements conventional clinical methods. The second part describes how this technique applies to specific categories of critically ill patients. Like other new and specialized techniques, hemodynamic monitoring requires the development of a certain expertise, followed by an adequate frequency of use to ensure maintenance of initially developed skills. We estimate that an institution should not undertake this technique unless it would be used at least once per week. Outfitting a hemodynamic monitoring operation is expensive, and considerations of durability, portability and available servicing are important. Unlike many procedures that provide diagnostic insights, hemodynamic monitoring involves sampling over time and, as such, implies a commitment and the availability of specially trained physicians and nurses. Furthermore, technical sup-
port should be available to ensure that the information being gathered is both accurate and reproducible. The availability of such information on the critically ill patient permits the study of the pathophysiology of disease at the bedside; clinical skills are aided by immediate feedback, which allows correlation of noninvasive and invasive assessment. It is important to ensure that the technology involved does not obscure the fundamental purpose - better care of the critically ill. Since there is considerable effort and expense involved in initiating and maintaining hemodynamic monitoring, and some inevitable risk and discomfort for the patient, the indications for the application of this technique should be carefully established prior to its use. Fundamental to the understanding of hemodynamic monitoring is an appreciation of certain physiological concepts and measurements. To aid in this appreciation we have prepared a glossary of terms and abbreviations that are used throughout the symposium. For clarity and consistency we have indicated the synonyms that exist for certain terms and have then selected one of these for subsequent use. Fur-
thermore, the first time an abbreviation i. used in each of the papers it is again defined. In summary, this symposium outlines the requirements, problems and potential of hemodynamic monitoring and relates them to the types of critically ill patients for whom the technique is most useful. Hemodynamic monitoring generates a continuous flow of information that demands rapid and frequent therapeutic decisions. These decisions may lead to the administration of potent drugs such as vasodilators and catecholamines; thus, a thorough knowledge of their pharmacology is mandatory. Hemodynamic monitoring is no substitute for common sense and careful clinical reasoning. Even with the additional information it provides, the wisest and most difficult therapeutic decision may be only to observe. In general, however, hemodynamic monitoring enables greater diagnostic precision, permits a wiser selection of therapeutic measures and provides a safer means of assessing the results of therapy. It is a pleasure to acknowledge the capable secretarial assistance of Mrs. Lucy Rapp, Mrs. Anne Baron and Mrs. Christine Rider.fl
Glossary of tenns and abbreviations PRELOAD: end-diastolic fibre length; approximated in humans by end-diastolic volume or pressure. AFTERLOAD: reflects left ventricular wall tension during systole; approximated by product of left ventricular systolic pressure and radius. CONTRACTILITY: force with which left ventricular ejection occurs Independent of effects of preload and afterload. VENTRICULAR COMPLIANCE: distensibility or stiffness of relaxed ventricle; reciprocal of Instantaneous slope of diastolic pressure-volume curve. IMPEDANCE: complex function determined by peripheral vascular resistance and compliance of large arteries; its determinants include physical properties of blood (viscosity and density) and of vascular wall (diameter and viscoelasticity); Instantaneous ratio of pressure to flow. CO: cardiac output; amount of
blood pumped per unit of time. CI:" cardiac index; expression of cardiac output adjusted for body surface area. SI':" stroke volume; amount of blood pumped per heart beat. EF:" ejection fraction; percentage of emptying in ventricle. SIP: systolic blood pressure. MAP: mean arterial pressure. DIP: diastolic blood pressure. RVEDP: right ventricular enddiastolic pressure. RAP: mean right atrial pressure. CVP: central venous pressure. RVFP: right ventricular fling pressure; determined from RVEDP, RAP and CVP. LVEDP: left ventricular enddiastolic pressure. LAP: mean left atrial pressure. PCW: mean pulmonary capillary wedge pressure = pulmonary artery occlusion pressure; approximated by pulmonary artery diastoic pressure, PCW, LVEDP and LAP may be referred to as left ventricular filling pressure (LVFP).
866 CMA JOURNAL/OCTOBER 6, 1979/VOL. 121
SVR
total systemic vascular
resistance; expression of
resistance to ventricular ejection. TTIC' tension-time index; indfrect estimate of myocardial oxygen consumption (Mtoj. RPP" rate-pressure product;
modification of TTL $PTI:" systolic pressure-time index; is related to area under left ventricular systolic pressure curve and reflects MVo. DPTI:" diastolic pressure-time index; Is related to area in diastole between arterial diastolic and left ventricular diastolic pressures and reflects coronary perfusion. DPTI/SPTh" supply-demand relation of ventricle. EVRt endocardial viability ratio. TMG:' trausmyocardlal gradient; reflects pressure gradient determining coronary blood flow (C119. "Derived indices, the formula and units for which appear In the appendix to Gilbert ad Hew's paper.
Hemodynamic monitoring as an adjunct to the care of the critically ill patient is but one of a number of technologic advances made available to the practising physician in the past decade. It is an invasive technique characterized by the placement and maintenance of intracardiac and intravascular catheters for the continuous recording of pressure and the intermittent determination of flow. The information provided by this technique has had a major impact on therapeutic
This symposium will be published in the fall of 1980 by Harper and Row Publishers, Inc., Hagerstown, Maryland. For this reason reprints of the entire symposium will not be avail. able. However, reprints of the Individual papers will be available from the authors.
The material included in this issue of the Journal has been divided into two parts. The first provides the historical and physiological background of hemodynamic monitoring and a discussion of the equipment and techniques used, and concludes with a discussion of how this approach complements conventional clinical methods. The second part describes how this technique applies to specific categories of critically ill patients. Like other new and specialized techniques, hemodynamic monitoring requires the development of a certain expertise, followed by an adequate frequency of use to ensure maintenance of initially developed skills. We estimate that an institution should not undertake this technique unless it would be used at least once per week. Outfitting a hemodynamic monitoring operation is expensive, and considerations of durability, portability and available servicing are important. Unlike many procedures that provide diagnostic insights, hemodynamic monitoring involves sampling over time and, as such, implies a commitment and the availability of specially trained physicians and nurses. Furthermore, technical sup-
port should be available to ensure that the information being gathered is both accurate and reproducible. The availability of such information on the critically ill patient permits the study of the pathophysiology of disease at the bedside; clinical skills are aided by immediate feedback, which allows correlation of noninvasive and invasive assessment. It is important to ensure that the technology involved does not obscure the fundamental purpose - better care of the critically ill. Since there is considerable effort and expense involved in initiating and maintaining hemodynamic monitoring, and some inevitable risk and discomfort for the patient, the indications for the application of this technique should be carefully established prior to its use. Fundamental to the understanding of hemodynamic monitoring is an appreciation of certain physiological concepts and measurements. To aid in this appreciation we have prepared a glossary of terms and abbreviations that are used throughout the symposium. For clarity and consistency we have indicated the synonyms that exist for certain terms and have then selected one of these for subsequent use. Fur-
thermore, the first time an abbreviation i. used in each of the papers it is again defined. In summary, this symposium outlines the requirements, problems and potential of hemodynamic monitoring and relates them to the types of critically ill patients for whom the technique is most useful. Hemodynamic monitoring generates a continuous flow of information that demands rapid and frequent therapeutic decisions. These decisions may lead to the administration of potent drugs such as vasodilators and catecholamines; thus, a thorough knowledge of their pharmacology is mandatory. Hemodynamic monitoring is no substitute for common sense and careful clinical reasoning. Even with the additional information it provides, the wisest and most difficult therapeutic decision may be only to observe. In general, however, hemodynamic monitoring enables greater diagnostic precision, permits a wiser selection of therapeutic measures and provides a safer means of assessing the results of therapy. It is a pleasure to acknowledge the capable secretarial assistance of Mrs. Lucy Rapp, Mrs. Anne Baron and Mrs. Christine Rider.fl
Glossary of tenns and abbreviations PRELOAD: end-diastolic fibre length; approximated in humans by end-diastolic volume or pressure. AFTERLOAD: reflects left ventricular wall tension during systole; approximated by product of left ventricular systolic pressure and radius. CONTRACTILITY: force with which left ventricular ejection occurs Independent of effects of preload and afterload. VENTRICULAR COMPLIANCE: distensibility or stiffness of relaxed ventricle; reciprocal of Instantaneous slope of diastolic pressure-volume curve. IMPEDANCE: complex function determined by peripheral vascular resistance and compliance of large arteries; its determinants include physical properties of blood (viscosity and density) and of vascular wall (diameter and viscoelasticity); Instantaneous ratio of pressure to flow. CO: cardiac output; amount of
blood pumped per unit of time. CI:" cardiac index; expression of cardiac output adjusted for body surface area. SI':" stroke volume; amount of blood pumped per heart beat. EF:" ejection fraction; percentage of emptying in ventricle. SIP: systolic blood pressure. MAP: mean arterial pressure. DIP: diastolic blood pressure. RVEDP: right ventricular enddiastolic pressure. RAP: mean right atrial pressure. CVP: central venous pressure. RVFP: right ventricular fling pressure; determined from RVEDP, RAP and CVP. LVEDP: left ventricular enddiastolic pressure. LAP: mean left atrial pressure. PCW: mean pulmonary capillary wedge pressure = pulmonary artery occlusion pressure; approximated by pulmonary artery diastoic pressure, PCW, LVEDP and LAP may be referred to as left ventricular filling pressure (LVFP).
866 CMA JOURNAL/OCTOBER 6, 1979/VOL. 121
SVR
total systemic vascular
resistance; expression of
resistance to ventricular ejection. TTIC' tension-time index; indfrect estimate of myocardial oxygen consumption (Mtoj. RPP" rate-pressure product;
modification of TTL $PTI:" systolic pressure-time index; is related to area under left ventricular systolic pressure curve and reflects MVo. DPTI:" diastolic pressure-time index; Is related to area in diastole between arterial diastolic and left ventricular diastolic pressures and reflects coronary perfusion. DPTI/SPTh" supply-demand relation of ventricle. EVRt endocardial viability ratio. TMG:' trausmyocardlal gradient; reflects pressure gradient determining coronary blood flow (C119. "Derived indices, the formula and units for which appear In the appendix to Gilbert ad Hew's paper.
