J AM Call CARDIOl 1031983;1: I03- 13

Hemodynamic Measurements in Clinical Practice: A Decade in Review

H. J. C. SWAN, MD, PhD, FACC, WILLIAM GANZ, MD, CSc. FACC

Los Angeles. California

Hemodynamic measurement is now an important andfeasible adjunct to clinical practice. Its successful ap­plication to alleviate illness in human beings is evidentin its contribution to an understanding of the patho­physiology of disease and the efficacy of various inter­ventions to alter the course of a variety of diseases. Itsapplication is widespread in the high risk patient

Observation and common clinical skills alone have not provedadequate to determine many important aspects of cardio­vascular function, or to monitor circulatory changes in atime frame that permits intervention. For this reason. thepast decade has been characterized by a virtual explosionin a variety of invasive and noninvasive techniques to pro­vide information on the mechanical function of the heartand the factors that affect it. It is reasonable in this age ofcomputers and communications and microwaves and mi­crosensors to anticipate still further advances in the tech­niques and application of measurement and monitoring.

This review examines the "invasive" measurement ofcardiac output and intravascular pressures and resistancesas an accepted part of modem cardiology and its role in thecare of the critically ill patient. Acceptance of the clinicalvalue of invasive hemodynamic measurements and moni­toring is not based on structured clinical trials, althoughthese have been advocated in the past (l). Indeed, it isobvious to all that morbidity and mortality are many timesgreater in monitored than in nonmonitored patients. How­ever, the logic that decisions concerning prognosis and ther­apy are made more readily, more rapidly and with greaterconfidence when based on quantitative measurements ofsignificant variables of cardiovascular function appears tobe persuasive in the minds of many physicians and healthcare personnel. For example, this facility in decision mak­ing allows for the acceptance of high risk patients for needed

From the Division of Cardiology, Department of Medicine, Cedars­Sinai Medical Center. and UCLA School of Medicine, Los Angeles.California.

Address forreprints: H.J.C. Swan, MD, PhD, Division of Cardiology.Cedars-Sinai Medical Center, 8700 Beverly Boulevard. Los Angeles. Cal­ifornia 90048.

©1983 by the American College of Cardiology

undergoingsurgery and the criticallyill medically treatedpatient. Hemodynamic measurement permits accuratedetermination of the state and, if necessary, of the con­tinuously changing function of the heart as related todisease process and guides treatment and interventionson a rational physiologic basis.

surgical procedures who would have been rejected 10 ormore years ago on the basis of unsuitability for operation.

A colleague* has written. "Over the years I have beena part of progress in intraoperative cardiovascular monitor­ing. In the 70's we had sometimes heated discussions overwhether or not an indwelling arterial catheter should beinserted! Then. we "progressed" to question the value offlow-directed pulmonary artery catheters. But, after we be­gan to use the more advanced technology, we discoveredso much benefit that we continue to still further expand theuse of invasive monitoring first to the obviously criticalpatient and then to less critical but at risk individuals ...the subsequent explosion of knowledge of how to effectivelyintervene to preserve and improve impaired heart functionin coronary disease patients undergoing cardiac surgery hasbeen truly spectacular and personally rewarding." Underthese circumstances of developing knowledge and changingtechniques and clinical indications, elaborate randomizedtrials to "prove" effectiveness are impractical and wouldprobably fail to provide the desired guidelines even if broughtto completion.

In broad review. the question "Has hemodynamic mon­itoring been of significant value in the management of car­diovascular derangements?" may be answered with an un­equivocal "Yes," qualified in certain specifics. In the fieldof clinical investigation, which encompasses the under­standing of the mechanisms of the differing disease entitiesand clinical syndromes and the development and evaluationof different treatment forms, the ability to make relatively

*Dr. J, Tinker, Chief of Department of Cardiac Anesthesia, MayoClinic, Rochester, Minnesota, Correspondence quoted with permission.

0735-1097/83/010103-11$03,00

104 J AM COLL CARDIOL1983; I: 103-13

SWAN AND GANZ

simple but accurate and quantifiable measurements of im­portant variables has proved to be of the utmost value.Equally, the value in specified circumstances of predictablehazards, such as a complex surgical procedure or a surgicalprocedure in a seriously ill patient (2), would be stronglysupported by a high proportion of cardiac and other specialtysurgeons. However, in the management of the acute syn­dromes of ischemic heart disease, congestive heart failureand other diseases of the heart, a variety of opinions exist(3). Such issues characterize virtually all frontiers of car­diovascular medicine today. The principles of invasivehemodynamic measurement are reasonably established; theapplications-who, when, where, and so forth-remam tobe completely defined.

PrinciplesCardiac catheterization. The measurement of cardiac

output and its determinants and the effect of drugs on bloodvessels were already known in the early part of this centurybecause of the work of the giants of cardiovascular physi­ology-Frank (4), Starling (5), Dale (6) and their colleaguesand students. These fundamentals were not applied in car­diology or medicine, or even considered remotely relevant,until the late 1940s when Cournand (7), Bing (8), Dexter(9) and their co-workers in this country and McMichael andSharpey-Schafer ( 10) in England applied the novel personalexperiment (or experience) of Forssman ( 11) to obtain mea­surements of the oxygen saturation of central venous bloodand concomitantly measure pressure in the right side of thecirculation in human subjects. Right heart catheterizationand pulmonary artery blood sampling allowed the mea­surement of cardiac output by application of Fick 's prin­ciple; measurement of right and left atrial (pulmonary wedge)pressures allowed estimation of the preload of each ventri­cle; and a knowledge of pulmonary and systemic arterialpressures permitted calculation of vascular resistances withacceptable accuracy. The Fick method for cardiac outputdetermination was laborious, time consuming and of limitedrepeatability. The catheterization techniques then availabledepended on the manipulation of semi-stiff catheters (bor­rowed in part from the urologic disciplines) using radiologicimaging of low efficiency. Right heart catheterization inev­itably resulted in atrial and ventricular ectopic rhythms andwas attended by a significant complication rate (12), evenin patients who were not critically ill.

Swan-Ganz balloon flotation catheter. Concerned bythe lack of understanding of the pathophysiologic processesunderlying acute myocardial infarction and other clinicalischemic cardiac syndromes, we believed that the applica­tion of catheterization techniques was essential to a mean­ingful investigation of many aspects of these conditions.This required a rethinking of the principles of cardiac cath­eterization so as to make them compatible with the envi-

ronment in which they were to be applied (13). We won­dered whether a highly flexible catheter could be made toenter the pulmonary artery consistently and safely withoutthe use of fluoroscopy. Bailon-tipped catheters had beenused in many circulatory investigations (14,15) and pro­cedures (16,17). Within a few months of the developmentof the pressure-monitoring, flexible, flow-guided, balloon­tipped, 1.5 mm (5F) catheter, 100 consecutive patients hadbeen studied in the cardiac care unit at Cedars of LebanonHospital in Los Angeles. The findings were reported in theNew England Journal of Medicine in 1970 (18) and dem­

onstrated the following critical points: bedside catheteriza­tion of the pulmonary artery was possible without the useof fluoroscopy in a very high proportion of patients in whomthe procedure was attempted. More importantly, successfulcatheterization could be achieved even in the sickest pa­tients, and failures were usually associated with difficultyin transvenous manipulation from the arm or with the pres­ence of a large right atrium and tricuspid regurgitation.Catheterization of the heart by this method could be achieved

by physicians not necessarily possessing the manipulativeskills acquired in a cardiac catheterization laboratory. Com­plications, in particular significant arrhythmias, were un­common. Most importantly, the application of these tech­niques was feasible within the environment where they wererequired. Furthermore, after appropriate educational pro­grams, the then emerging discipline of critical care nursingproved to be highly accepting of the application of physi­ologic monitoring and demonstrated major growth and ex­pertise in the discipline (19,20).

Role of measurements of ventricular filling pres­sure. The most important initial consequence of these de­velopments was the ability to measure right and left ven­tricular filling pressures. A relation between these valueshad been demonstrated in normal subjects (21), and theassumption was made that this relation also pertained topatients with a variety of diseases. In fact, nothing wasfurther from the truth. Ischemic heart disease-a commonovert or covert component of Western civilization and theprocess of aging-characteristically affects one ventricle toa greater extent than the other. Pulmonary disease affectsthe right ventricle to a greater degree than the left. There­fore, it is of little surprise that an understanding of thefundamentals of circulatory dynamics in the diseased staterequires, at a very minimum, an adequate description of thepreload of both right and left ventricles (22). It is of someinterest that a short decade ago considerable debate anddiscussion were addressed to the issue of whether centralvenous pressure measurements allowed an assessment ofcirculatory dynamics adequate for most clinical purposes.Because a measurement is obtained readily does not meanthat it is necessarily useful. It was concluded that, undermany circumstances, measurement of central venous pres-

HEMODYNAMIC MEASUREMENTS IN CLINICAL PRACTICE J AM COLL CARDIOL1983:1:103-13

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sure was more likely to mislead than to provide effectiveguidance in the treatment of cardiopulmonary diseases (23) .

Measurement of Cardiac OutputAlthough indocyanine green indicator-dilution curves wereused extensively in catheterization laboratories for the mea­surement of cardiac output (24), the applicationof this tech­nique at the bedside or in the operating room was beset bymajorpractical difficulties. The useof densitometricdevicesor even the spectrophotometric analysis of the dye concen­tration of individual blood samples was required. Thesetechniques were time consuming, required a relatively skilledlaboratory staff and. hence, were unsuitable for practicalclinical application. Because cardiac output was difficult tomeasure a decade ago, clinicians believed that a knowledgeof its magnitude and its directional changes could not con­tribute to patient management!

Thermodilution measurement technique. The provi­sion of a pulmonary artery thermistor and the addition of acatheter for injectionof cold indicator (25,26) permitted thepracticalmeasurement of cardiacoutput in a widepopulationof critically ill patients and in a variety of clinical environ­ments. Incorporation of the thermistor in the catheter shaftandan additionallumen for rightatrial injection(27) allowedthe application of simple computational devices for the im­mediate calculation of cardiac output. Measurement of car­diac output by thermodilution technique with injection ofcold indicator into the right atrium and definition of thetemperature change in the pulmonary artery is now simpleand feasible. It is a bedside procedure, usually performedby nursingpersonnel, that is both precise and accuratewhenperformed correctly (27-29). Previously, the measurementof cardiac output was unusual in a clinical setting, consid­ered irrelevant by most physicians, and rarely, if ever, ob­tained with the thermodilution method. Today, millions ofestimations of cardiac output are carried out annually in aclinical setting; probably 95% of these are made bythermodilution.

In the normothermic nonanemic patient suffering from avariety of illnesses, the cardiac index usually exceeds 2.2liters/min per rrr'. From the cardiovascularstandpoint. suchpatients have a favorable prognosis. Moderate depressionof cardiac index (less than 2.2 but greater than 1.8 liters/min per rrr') represents a borderline cardiac output that isbarelyadequate to meet ordinary metabolic needs. A cardiacindex substantially less than 1.7 liters/min per rrr' is usuallyassociated with a poor to extremely poor prognosis unlessa reversible cause such as hypovolemia is identified andpromptly treated (Fig. I).

Clinical significance of measurement of cardiac in­dex. An isolated and accurate measurement of cardiac in­dex is of major prognostic significance, and can alert thephysician to the need for appropriate therapeutic response.

This is in contrast to endocrinedisorders, neoplastic diseasesand infectionsthat may be regardedby physiciansas' 'slow"processes. In many aspects of cardiovascular disease, out­come is determined by " fast" phenomena, the fundamentalfrequency of cardiovascular events being one cardiac cycle.These events include arrhythmias, pulmonary edema. pul­monary embolism. cardiac tamponade and ischemic necro­sis. Initial clinical findings may fail to distinguish a patientwith impending circulatory collapse from one who mayexperience a relatively benign outcome. For example. asevere reduction of cardiacoutput does not necessarily resultin a corresponding decrease in arterial blood pressure. butcan be masked by vasoconstriction in the peripheral arterialand venous beds. Also, severe pulmonary congestion mayprecede symptoms of acute pulmonary edema by severalhours. However, effective intervention is frequently with­held because of the inherent "optimism" (or fatalism) ofmedical care personnel who fail to search for critical in­formation in a timely manner. Although we are in no wayadvocating unnecessary prolongation of a life not worthliving, we believe that effective action in situations thatpermit satisfactory restoration of human capabilities is themoral. ethical and social basis of medicine and a first lineresponsibility of its practitioners. The penalty for errors ofserious omission may be great-it is paid for by the patient.

Control of Cardiac OutputThe determinants of myocardial oxygen consumption arealso principal factors in the control of cardiac output (30).In depression of myocardial contractility due to disease orthe effects of pharmacologic agents, the heart is criticallyafterload-dependent. In contrast to the behavior of the nor­mal heart or the heart in systemic hypertension, substantialincreases in cardiac output accompany a reduction in leftventricular outflow impedance. Such interventions. readilyachieved in modern critical care units, can increase cardiacoutput by as much as 50%. restore organ perfusion, reversemetabolicacidosisand significantly improveshort-term and,hence, the potential long-term prognosis. Effective appli­cation of impedance reduction by systemic arterial vaso­dilator drugs is dependent on a knowledge that the cardiacoutput is, in fact, substantiallyreducedand that the reductionis associated with a high systemic vascular resistance-amajor component of aortic impedance (31). Similarly, the"sick" ventricle is preload-dependent in several clinicalcircumstances. For this reason, we have recommendedmaintenance of left ventricular filling pressure (wedge pres­sure) at 15 to 18 mm Hg. The normal left ventricular fillingpressure is 6 to 12 mm Hg (32) and the normal right ven­tricular filling pressure is 2 to 5 mm Hg. Modest deviationsfrom these levels may be associated with adverse cardiacand pulmonary changes. The implications of manipulation

106 J AM COLL CARDIOL1983 : I :103-13

SWAi\ A"iD GAN Z

Figure 1. Schematic representation of the relation of car­diac index to prognosis in cri ticall y ill patients. The leftpanel indicate s the probab ility of surviv al based on areasonably accurate determination of cardiac index andthe assumpti on that cardiac index does not substantivelyimprove in a reasonably short time . For patients whosecardiac index is 2.0 or greater . the likelih ood of survivalis not likely to be related to depression of cardiac perfor­mance; for those with a card iac index of 1.0. the proba­bility of survival is small and mortality i, due to inadequatetissue perfusion . In the right panel. the likely time todeath in hours is also related to cardiac inde x. A cardiacindex of 1.5 or less will result in a high mortality rate anda relatively short dur ation of survival unle ss the card iacindex increa ses spontaneously or can be increased by ther ­apeutic intervent ions; this adverse prognosis does not nec­essarily pertain in altered metabolic state, such as hy­pothermia and post-anesthesia .

2.01.5

TIME TO DEATH

4

16

32

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1.5 2.0 .5 1.0CARDIAC INDEX (I/min/m 2 )

PROBABILITY OF SURVIVAL1.0

.75

.25

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of afterload and preload are represented diagrammaticallyin Figure 2.

A decade ago, the cardiologist 's therapeutic mainstayconsi sted of digitalis, diuretic drugs and vasopressors . Ma­nipulation of preload and afterload was not regarded asfeasible or relevant in " heart failure ," although some car­diac surgeons favored maintenance of high left atrial fillingpressures in the postoperative patient. Recognition and man­agement of hypovolemia, frequentl y caused by overenthu­siastic use of diuretic drugs. characterized the mid 1970s;by the end of the decade , a variety of short- and long-actingvasodilator drugs were applied with benefit in patient s withacute or chronic heart failure. In each of these instances,application relied heavily on hemodynamic measurement.

Hemodynamic Measurementsand Monitoring in Clinical Practice Today

The specifics of medical practice are determined by atti­tudes. resources , skills and the perception of the possibilityto alter the outcome of disease process favorabl y and sub­stantively. Thus, hemodynamic monitoring is indicated whenthere is a significant likelihood that the information derivedfrom the monitoring procedures will affect decisions con­cerning prognosis and therapy (33). The potential adver seevents ("complications") associated with such proceduresmust approach an irreducible minimum. From these state­ments of principle, it follow s that if no significant inter­vention is contemplated or possible , then hemodynamicmeasurement cannot benefit the patient and should not beperformed. Likewise, if the appropriate levels of under­standing of pathophysiology and cardiovascular therapy andthe technical skills of medical and paramedical personnel

responsible for procedures are lacking, deficient or unavail­able , hemod ynamic measurements should not be carried out.

Potential complicationsand limitations. Complicationsassociated with the use of balloon flotation catheters havebeen well described (34 ,35). The most serious of these isrupture of the pulmonary artery (36,37) associated eitherwith migration of a catheter tip into a distal vessel. or withinjudicious inflation of a balloon in a fragile pulmonaryartery branch of a diameter not substantially greater thanthat of the catheter shaft.

In addition to the complications related to insertion. ad­vancement and mainten ance, important human " compli­cations" of application still exist. The acquisition of skillto insert and position a flotation catheter safely is only thefirst, and certainly not the last. responsibility of the phy­sician who employs hemodynamic measurements in clinicalpractice . Regrettably, the inherent simplicity and safety ofthe insertion technique have fostered a cavalier attitude amongmany physicians and paraprofe ssional personnel. so thatestablished procedures are allowed to deteriorate . Manyphysicians (including cardiologists) do not sufficiently com­prehend the physical principle s underlying the measurementof pressure (38) or blood flow (39). Because of preoccu­pation with the technical aspects of catheter insertion andfailure to provide adequate supervision for physicians intraining. sloppy habits and inferior techniques have beenallowed to proliferate. Owin g to inexperience or ignorance .many physicians fail to recognize artifacts in pressure sig­nals that commonly occur during record ings of pressuresutilizing fluid-filled catheters. Of even greater significanceis the failure of many treating physicians to understand themeaning of physiologic data, its relat ion to the clinical stateand the associated issues of progno sis and optimal therapy.In our opinion. this represent s a retrogressive step from the

HEMODYNAMIC MEASUREMENTS IN CLINICAL PRACTICE J AM Call CARDIal1983;1:103-13

107

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situation a decade ago, when hemodynamic measurementwas the interest and the responsibility of investigative phy­sicians. Widespread and relatively intensive training in therelevant aspects of cardiopulmonary physiology and car­diovascular pharmacology characterize the subspecialties ofanesthesia and critical care. We believe that it is essentialthat physicians responsible for hemodynamic measurementsbe trained in these fundamentals, have appropriate knowl­edge of the principles of measurement of blood flow andintravascular pressures, be skilled in the insertion of cath­eters and be capable of committing both time and effort tothe management of critically ill patients.

Indications. The indications for hemodynamic moni­toring in clinical practice are extremely diverse and areincreasing, but the fundamental requirements stated earlierremain. The broad indication for invasive measurements canproperly be restated, that is, when the availability of hemo­dynamic descriptors can complement the etiologic and func­tional diagnosis, define the likely temporal progression ofthe changing pathophysiology and modify, or possibly mod­ify, the therapeutic approach to management.

Applications

The following commentary relates to application by disci­pline. in contrast to disease, and presupposes the existenceof conditions that permit successful application of theprocedures.

Diagnostic cardiac catheterization. The flexible f1ow­guided balloon-tipped cardiac catheter has greatly reducedthe time, skill levels and complications involved in an ef­fective right heart catheterization (40). As a general ap­proximation, manipulative and fluoroscopic times may bereduced by half for right heart catheterization in patientsstudied under fluoroscopy in the cardiac laboratory. It isunusual for catheterization of the pulmonary artery with theballoon flotation catheter to require more than 30 seconds.

Figure 2. The relation of preload and afterload to cardiac index in normalsubjects and patients with heart failure. The term heart failure as used hererelates to depressed cardiac function and not to the clinical manifestationsof congestion and low forward flow. In the left panel. the relation topreload as defined by left ventricular filling pressure (L.V.F.P) is shown.Cardiac index in the patient with heart failure is highly preload-dependent;at even "normal" levels of left ventricular filling pressure, the cardiacoutput may be inadequate to satisfy metabolic demands. In the normalheart, not only is the cardiac performance substantially greater at all levelsof filling pressure, but also even at low filling pressures the resultingmagnitude of cardiac index exceeds that necessary for metabolic survival.

In the right panel, the relation of systemic vascular resistance (S.V.R.)to cardiac index is shown. Not only is the normal heart less directlyembarrassed by the magnitude of systemic vascular resistance (as an im­portant component of aortic impedance), but also the absolute level ofcardiac index in the patient with heart failure is depressed to levels ofmetabolic inadequacy. Reduction of systemic vascular resistance in bothnormal subjects and patients with heart failure resulted in an increase incardiac index, but only in the patient with heart failure is the absolutevalue moved from a critically reduced to an adequate range.

Indeed, a colleague once remarked that he did not see howphysicians could be trained in manipulative catheterizationskills if the balloon flotation catheter was routinely used incatheterization laboratories-a somewhat irrational objec­tion to its application.

In complex congenital malformations of the heart, it isfrequently difficult, if not impossible, to manipulate semi­stiff cardiac catheters into a ventricular chamber or greatartery. The application of a flexible balloon flotation catheterunder these circumstances almost always permits entry to aventricle and great vessel, whose definition is then greatlyfacilitated (41).The ability to establish an anatomic diag­nosis with minimal delay or intracardiac trauma is of greatimportance in the management of newborns and infants withcongenital heart disease. Application of the balloon flotationcatheter, together with consequent angiography, has enor­mously facilitated effective and safe diagnostic proceduresin such patients.

Anesthesia in cardiac surgery. Maintenance of the car­diopulmonary integrity of patients during surgical interven-

108 J AM COLL CARDIOL1983: 1. 103~ 13

tion is essential. Although the benefits of management underconditions of hemodynam ic monit oring have been appre­ciated and extensively applied by the discipline of anesthe­siology, some senior surgeons have doubted and continueto doubt that the benefit of improved management outweighsthe inherent risks and, perhaps more importantly, the logisticincon veni ences associated with measurement and monitor­ing procedures. Difficulties increase when the contemplatedprocedure is major, complex and of long duration. In ad­dition, morbidity and mortality are importantly related tothe pat ient' s condition before operation . Hence , the indi­cations for hemodynamic mea surements and monitoring inoperative patients are related both to the contemplated sur­gical procedure and to the underlying cardiovascular healthof the subject (2,42).

In anesthesia, the most rapid acceptance and applicationof hemodynamic measurement have been in the field of car­diovascular surgery (43) . In the transition from surgical

procedures on essentially healthy myocardium (congenitalmalformations) to operations on patients with inherentlydiseased myocardium (ischemic heart disease), the contem­porary cardiovascular surgeon has accepted a patient groupwhose inherent survival characteristics are less than favor­able. Such patients have many of the criteria that definesurgica l " high risk ," including relat ively advanced age,prior myocardial infarction , angina pectori s , hypertension ,aortic aneurysm, carotid artery disease and stroke in thepresence of a variet y of other general conditions , such asdiabetes, peripheral atherosclerosis, renal disease and im­muno suppressive state s. To this galaxy of surgical deter­rent s . pat ient s with valvular heart disease who previouslypresented clinical manifestations early in life are now seenin the fifth , sixth and seventh decades.

This, therefore, is the current matrix of patients pre­senting f or potential relief by means of cardiac surgery.The intrinsic risk of mortality and morbidity is great. Thisrisk may be enhanced by the occurrence of significant myo­card ial ischemia during premedication , induction. intuba­tion and general support until cardi opulmonary bypass issuccess fully initiated . In such patients. hemodynamic mon­itoring is used to reco gnize reflex vasomotor changes , hy­poxia and adverse effects on ventricular myocardium (44) .

To be more specific, the preoperative states that parti c­ularly fa vor appli cation ofhemodynamic monitorin g includeprior evidence of myocardial infarcti on. reoperation in pa­tient s previou sly subjected to coronary artery bypass graft­ing (45). left main (46 ) or complex coronary artery disease.valvul ar heart disease associ ated with significant coronaryatherosclerosis. mitral stenosis in the elderl y , mitral stenos iswith severe pulmonary hypertension and multi valvular dis­ease. To the contemplative physician responsible for thecare of patients undergoing cardi ac surgery. the uncompli­cated course that is usually followed is almost miraculous.Nevertheless. it is logical to believe that patients with even

more severe limitations-and, therefore. with more to gain­will continue to present as surgica l ca ndidates . Preservationof the currently satisfactory outcome of surgery for the va­riety of cardiac disorders is no longer dependent only onthe exce llence of surgical technique. but also on the detailsof intra- and postoperative management by the anesthe­siologist and his physician colleagues (47). A recent study(48) demon strated that more than 60% of adverse event swere not recognized by ex perienced ca rdiovascular anes­thesiologists " blinded" from concurrent hemodynamicmeasurements.

Application in general surgery. The increased mort al­ity and morbidity of patients more than 65 years of ageundergoing general surgi cal procedures (two to five time sgreater than mortality and morbidity in younger patients)presents a contemporary challenge of both moral and sci­enti fic import . This unsatisfactory situation pertains becauseelderly patients have . by the ir very nature. a signifi cantprevalence of intrinsic coron ary artery disease and an in­cidence of previous cardiovasc ular disease. Hence . opera­tion in such patient s. without careful regard for the con­sequences of myocard ial ischemia, will result in anunsatisfactory outcome in a relatively large proportion ofpatient s (49) .

An increasing number of vascular procedures (50) . andin particular resection of intrathoracic aneurysms . are nowconducted under conditions of hem odynamic monitorin g(5 1,52) . Similar considerations apply to prostatectomy, anoperation common in the elderly coronary prone male . Inpatient s undergoing this procedure . the prevalence rate ofintrinsic coronary disease is high . and the stres ses on thecirculation by alteration in intravascular volumes (and os­molarity) during the operation may be great (53). For the sereasons the anesthesiologist responsible for the ongoing careof the elderly patient with a significant surgical . 'problem"must test for the presence of coro nary artery disease andmeasure and monitor such patient s before and during thecourse of their operation (54). Although the majority ofelderly patients may not prove to have important cardiac orvascular disorders. a proport ion must be treated with greatskill durin g and after their operation to avoid significantischemic epi sode s and the potent ial of a disastrou s cardiacevent. Thi s is particularly true in patients who require op­erations of long duration . such as complete hip replacementor extensive resection for cancer (55). In such patients it ismandat ory that ischemic event s due to the presence of sub­critical coronary atherosclerosis be avoided or at leastmin imized.

A recent report (56) concerned the application of hemo­dynamic monitoring in patients with prior myocard ial in­farction undergoing noncard iac surgery . Compared withnonmonitored patients. the monit ored patients demonstrateda reduction in perioperative infarct ion rate from 7.7 to 2.3%overall and from 28 to 5% in those in whom infarction was

HEMODYNAMIC MEASUREMENTS IN CLINICAL PRACTICE J AM cou, CARDlOl1983;I:103-13

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more recent than 6 months. The mortality associated withperioperative infarction was high. Although the series re­ported was not concurrent, their characteristics and opera­tions were closely similar, and the reponed differences inoutcome are striking.

Cardiac intensive and coronary care units. Hemody­namic measurement as defined in this review has been inthe forefront of the development and application of knowl­edge in cardiac care, particularly in ischemic states (57­61). However, a significant concern about the appropriate­ness of application of hemodynamic measurement in theindividual patient still exists. In our opinion, this is due toa misconception on the part of cardiologists regarding isch­emic cardiac syndromes. Conventional authorities suggestthat hemodynamic monitoring is relevant only in the com­plicated patient with severe heart failure or established car­diogenic shock.

This wisdom ignores the fa ct that myocardial damage inacute myocardial infarction is a temporarily rapid process(62) and outcome is determined largely during the first hoursafter the onset of symptoms. Hemodynamic measurements(including noninvasive testing for abnormalities of regionalwall motion and global function) will identify those patientsin whom the territory at risk is large and in whom inter­ventions, such as thrombolysis (63 ) or prompt myocardialrevascularization (64) , may significantly limit necrosis orbe lifesaving. The applications of hemodynamic measure­ments in patients relatively late in the course of complica­tions of acute myocardial infarction, although generally ac­cepted, are restricted to fine tuning of a fundamental medicaldisaster.

As a general recommendation, we believe that earlyhemodynamic measurements are appropriate in patients withthe greatest vulnerability. These include the young and thosewith a first infarct, no prior ischemic events and early evi­dence of circulatory collapse or serious arrhythmias. Forongoing therapy, management based on hemodynamic prin­ciples should be employed (65) . Demonstration of elevatedleft ventricular filling pressures and low cardiac output withan elevated peripheral vascular resistance indicates a poorprognosis; the time scale for a definitive decision is minutesto hours, not days or weeks.

The presence ofsignificant cardiac arrhythmias suggestsa specific application of the balloon flotation catheter . Min­iature extrusion and wiring technology has now permittedthe development of multipurpose balloon flotation catheters(66 ,67) that bear electrodes for sensing right ventricular andright atrial electrical activity; they also provide a site forstimulation of either the atrium or the ventricle. Differentialstiffening of the more proximal portion of the balloon flo­tation catheter allows for appropriate contact of the elec­trodes with the inflow tract to the right ventricle and thejunction of right atrium and superior vena cava. The use ofthese catheters permits the accurate identification of a wide

variety of cardiac arrhythmias that cannot be diagnosed withconfidence from surface electrocardiographic tracings alone.Certainty of diagnosis is essential to the appropriateness ofthe treatment selected. The application of the multielectrodecatheter systems allows for the evaluation or temporary (usu­ally emergent) application of atrial, atrioventricular or ven­tricularpacing. Quantitative measures of cardiac performanceare possible from the same catheter device. Such an acuteevaluation may define the optimal " long-term" pacemakerstrategy for a given patient with arrhythmic or conductiondisease.

Patients with chronic heart failure present a great man­agement challenge to the physician. not only in terms ofprolongation of existence, but also in the quality of lifewhile existence continues. Measured hemodynamic im­provement (increase in cardiac index, decrease in cardiacfilling pressures) caused by judicious application of vaso­dilator drugs (68,69) may be complemented by an appro­priate program of physical conditioning to improve the con­tentment and physical and emotional capacity of patientswith chronic heart failure. Notwithstanding adverse inter­mediate and long-term prognosis in these patients, the im­provement in activity levels and life acceptance under suchcircumstances has been remarkable in certain instances.

In summary, hemodynamic measurements Can be appliedin a variety of patients with primary cardiac disease to eval­uate acute cardiac dysfunction and to identify deficienciesin cardiac performance and the associated physiolo~ic fac­tors. They allow a rational application of pharmacologic andother interventions, as well as a prompt judgment concern­ing the efficacy of such interventions. In patients with chroniccardiac dysfunction, an effective and accurate evaluation ofthe functional status and the acute response to therapy canbe determined; ultimately this affects the patient's long-termoutcome.

Medical intensive care units. Appreciating the logisticreality that patients with cardiovascular disease (just con­sidered) are frequently admitted to medical intensive careunits, certain important subgroups of patients without car­diac disease also require hemodynamic monitoring (70 ) .

Principally, these include patients with preshock syndromesor features of noncardiogenic shock. Although cardiogenicshock is frequently related to irreversible destruction ofmyocardium and associated with a poor prognosis, the po­tential salvage of patients suffering from noncardiogenicshock remains substantial. Of particular significance arepatients with sepsis. combined pulmonary and cardiovas­cular disease and mild to moderate disease insults associatedwith serious immunosuppressive disorders. In such circum­stances, it is helpful to identify the contribution of changesin systemic vascular resistance, filling pressures for the leftand right ventricles and alterations in pulmonary resistancesas well as acid-base balance and gas transfer in order toevaluate such patients effectively. Only then can an appro-

110 J AM COLL CARDIOL19R3:I: 103-13

SWAN ""D C""Z

priate therapeutic plan be devised in complex multisystemdisease. The role of intrinsic depression of myocardial func­tion in morbid situations of primary noncardiac origin hasseldom been conceptually considered and has rarely beensubjected to analytical investigation.

Pulmonary intensive care. Investigation continues inthe cardiac component of the pathophysiology of primarypulmonary disorders. Measurement of pulmonary artery di­astolic and capillary wedge pressures allows differentiationbetween left heart failure, pulmonary embolus or chronicpulmonary disease with relative ease and a high degree ofcertainty. The presence or absence of right ventricular hy­pertrophy is a principal determinant of the response of theright ventricle to significant increases in afterload. Failureof the right ventricle may prove to be the real ,. Achilles'heel" in patients with acute or chronic pulmonary disorders.

The accuracy ofmeasurements ofpulmonary. ventricularor atrial pressure in patients supported by mechanical ven­tilators has also been questioned. The measurements them­selves remain simple and intrinsically correct; the interpre­tation becomes more difficult. The circulatory transmuralpressure is the difference between intravascular and extra­vascular pressure. Appropriate correction for ventilator-gen­erated pressures allows interpretation of the physiologic state.Also with use of the thermodilution technique, cardiac out­put and index may be effectively measured with reasonableaccuracy consistent with the physiologic environment. Car­diac output decreases during the positive phase of assistedmechanical ventilation and increases during passive expi­ration. Therefore, the true variability in intravascular pres­sures and in measured cardiac output must be consideredwith relation to the phases of supported ventilation.

Trauma. Management of the injured patient presents aseries of widely different logistic situations. Such patientsconstitute an important cohort of persons with gross dis­turbances in the function of the heart and lungs. In 1977,vehicular injuries alone resulted in 50,000 deaths with 1.9million subjects suffering from disabling injury (71). Traumaremains the leading cause of death in subjects under 40years of age who otherwise would have the best prognosisin terms of survival expectancy and life satisfaction. Al­though morbidity and mortality related to trauma and bumsare primarily related to severity of injury and to delays inthe initiation of definitive care, important changes in pul­monary vascular resistance from a variety of causes alsodevelop in such patients. These causes range from fat or airembolus to right ventricular contusion, hemopericardiumand neurogenic pulmonary edema. Although hemodynamicmeasurement is clearly inappropriate during field stabili­zation or transportation to a primary medical facility. itremains (or will become) appropriate to the functions ofregional trauma-burn-sepsis centers (72). Hemodynamic datanot only are relevant to operative risk, but also permit op­timal preoperative preparation and maintenance of intra-

operative fluid and electrolyte balance. A significant pro­portion of the victims of traumatic or burn injury are alsoelderly. Hence. after stabilization, the victim of trauma orsevere burns who is at risk for survival may benefit fromhemodynamic measurement and monitoring in the recog­nition of occult ischemic heart disease.

Patients presenting with acute' 'surgical emergencies."trauma. burns or sepsis may develop acute respiratory dis­tress syndrome and right ventricular failure (73,74!. Thesecondary (late) mortality rate in such patients is related tothese phenomena. The use of interventions conceptuallydesigned to rectify abnormalities of pulmonary and rightventricular function may help reduce the excessive late mor­tality and morbidity associated with chest and general trauma.With the exception of trauma centers, routine hemodynamicmeasurement in the care of such patients is in its infancy.However, pressure measurements alone will define the pres­ence and magnitude of hypovolemia. Fluid transfers in burnvictims are of such magnitude and rapidity that hemody­namic measurements appear to be a rational adjunct to care­fully programmed and effective treatment. Similar concernsrelate (uncommonly) to the critically ill pregnant patient(75).

Impact of Hemodynamic MeasurementThe fundamental role of the heart is to deliver blood to theorgans and tissues of the body in sufficient quantity to meetthe changing requirements of tissue metabolism. Blood isreturned from the tissues of the body for effective disposalof the products of metabolic activity through the liver, lungsand kidneys. Modern hemodynamic measurement permitsestimation of the magnitude of cardiac output with a highdegree of precision and with acceptable accuracy in themajority of clinical circumstances, so that the significanceof apparently small changes in the magnitude of cardiacoutput can be interpreted. Currently available hemodynamicmeasurements also provide direct information concerningthe determinants of cardiac output and the distributive be­havior of the pulmonary and systemic vascular systems.Over the past decade, the availability of such measurementsin virtually all subdisciplines of medicine has importantlyand positively affected both understanding and clinicalpractice.

Pathophysiology of disease states. Primary disease ofthe heart and lungs is a frequent and important componentof illness in human beings. Cardiac and pulmonary func­tional changes also characterize many noncardiac condi­tions. Hemodynamic measurements have provided im­proved understanding of the dynamics of cardiogenic andnoncardiogenic shock, the various anginal syndromes, andthe changing dynamics of evolving myocardial infarctionand cardiac arrhythmias. In the context of acute cardiacdisease, such measurements have importantly demonstrated

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the lag time between clinical findings and symptoms. inrelation to hemodynamic derangement and to the dynamicnature of such changes. Thus, hemodynamic measurementsserve as a reference point for the relation of symptoms.clinical findings and the responses of other noninvasive mea­sures of cardiovascular function. It is on the basis of suchmeasurements that the natural history of primary and sec­ondary cardiac and pulmonary disorders may be adequatelydescribed as a basis for successful intervention.

Clinical research. Hemodynamic measurement repre­sents a principal tool of clinical research on pharmaceutical.electrical and mechanical interventions . It has permitted theevaluation of vasoconstrictor. vasodilator and contractilitymodifiers , as well as the effect of agents believed to havesolely nonvascular actions (for example. antiarrhythmicagent s). These techniques further allow for an accurate eval­uation of the direction. magnitude and rate of change ofcardiac output and its determinants as a consequence oftherapeutic interventions . These methods have been used inthe evaluation of virtually all new cardiovascular drugs in­troduced over the past decade .

Patient care. In situations where risk can be predictedwith reasonable certainty. hemodynamic measurement andmonitoring continue to gain increasing acceptance. Debatestill exists concerning which patients (or conditions) notbeing treated surgically would benefit from invasive mea­surements . This debate is natural. If the probability of anadver se risk cannot be predicted with a reasonable degreeof certainty. then procedures that may be associated withintrinsic stress and hazard for an unknown benefit are justl yquestioned. In contrast , operative procedures are defined inadvance and the preoperative health of the patient also isknown . Therefore, a risk-benefit ratio of the use of hemo­dynamic measurement can be determined more readily inthe surgical than in the medical patient.

Surgical patient. Growing acceptance of hemodynamicmonitoring as a routine but selective part of patient care isevident in the discipline of anesthesiology and certain othersurgical subspecialties. The high risk patient group undergo­ing cardiovascular surgery includes patients of more ad­vanced age. patients with complex coronary artery disea se(including left main obstruction). associated valve diseaseor an ejection fraction of less than 0.35 and candidates forcardiac reoperation. Patients undergoing multivalve surgeryor elderly patients undergoing single valve surgery are alsobenefited. Hemodynamic measurement may be of less ben­efit in younger patients-those with unimpaired resting ven­tricular function. no primary myocardial infarction and agood hemodynamic profile . Patients unde rgoing treatmentof thoracic aneurysm or aortic dissection can experienceprofound alteration in left ventricular afterload and in bloodvolume . Fewer patients with vascular procedures on theabdominal aorta and iliofemoral system will necessarily benefitfrom hemodynamic monitoring . High risk may be associated

with prostatectomy, becau se a substantial number of patientsundergoing this procedure have overt or covert coronaryartery disease . Major surgery . particularly in the elderly,involving large shifts in blood volume (for example. inexten sive resection of malignancies) necessitates carefulcon sideration of the possible benefit s of hemodynamic mon­itoring . Trauma. sepsis and burn surgery are increasing theapplication of hemodynamic monitoring techniques. CertainSUbdisciplines. including obstetrics and gynecology. eye ,ear , nose , throat and plastic surgery. only occasionally re­quire hemodynamic measurements .

Nonsurgical patient. Medically designated diseases haveless well defined indications and contraindications for in­vasive hemodynamic measurements . Another decade willelapse before the role of hemodynamic measurements isclearly established. One important issue is to determine thelimits of sensitivity and errors of secondary noninvasivemeasurements of cardiovascular performance . If and whenthese can be defined . then substitution for invasive mea­surement techniques can be undertaken . However. as withthe earlier attempts at appl ication of hemodynamic mea­surement using the semi- stiff catheter systems in the clinicalenvironment. technologic characteristics will preclude manyof these methods becau se of environment . cost and non­continuity of application .

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