Therapeutic Pulmonary Artery Catheterization

moglobin saturation) and its relationship to oxygen demand. For example, a high cardiac output, 8 Umin, will have less D0 2 than a low cardiac output, 4 Umin, when the hemoglobin concentrations are 8 and 15 w'dl and the Sa02 values are 90 percent and 100 percent, respectively But how much 002 is necessary? Does it depend on VOl? Does it depend on need~·5 Is gastric tonometry an answer? Perhaps by explicitly recording oxygen delivery instead of cardiac output, there would be a more proper emphasis on this more important variable. Previous studies have shown that physicians are poor predictors of central hemodynamics. &.7 However, does therapy based on central hemodynamics rather than on clinical status improve outcome? If based on central hemodynamics, what therapy should be used? Studies have shown that therapy aimed to achieve supranonnal values improves outeome.v" Rather than doing studies to show that pulmonary artery catheterization affects therapy, randomized studies, such as Guyatt et alIa are doing, comparing pulmonary artery catheterization with clinical judgment, different therapies, or different therapeutic goals should be conducted to see whether they affect outcome. Milo Engoren, M.D., F.C.C.f, Department ofAnesthesiology, St Vincent Medical Center,

Thiedo REFERENCES

1 Steingrub JS, Celona G, Vickers-Lahti M, Teres D, Bria \\Z Therapeutic impact of pulmonary artery catheterization in a medical/surgical ICU. Chest 1991; 99:1451-55 2 Shippy CR, Apple PL, Shoemaker WC. Reliability of clinical monitoring to assess blood volume in critically ill patients. Crit Care Med 1984; 12:107-12 3 Schuster D~ Haller J. A quantitative correlation of extravascular lung water accumulation with vascular permeability and hydrostatic pressure measurements: a positron emission tomography stud~ J erit Care 1990; 5:161-68 4 Kaufman BS, Rackow EC, Faile JL. The relationship between oxygen delivery and consumption during 8uid resuscitation of hypovolemic and septic shock. Chest 1984; 85:336-40 5 Schumacker PT, Cain SM. The concept of a critical oxygen delivery. Intensive Care Med 1987; 13:223-29 6 Connors AF, McCaffree DR, Gray BA. Evaluation of right heart catheterization in the critically ill patient without acute myocardial infarction. N Engl J Med 1983; 308:263-67 7 Celona G, Steingrub JS, Vickers-Lahti M, Teres D, Stein KL, Fink M, et ale Clinical assessment of hemodynamic values in two surgical intensive care units: effects on therapy. Arch Surg 1990; 125:1036-39 8 Shoemaker WC, Apple PL, Kram HB, Waxman K, Lee TS. Prospective trial of supranormal values of survivors as therapeutic goals in high-risk surgical patients. Chest 1988; 94:1176-86 9 Tuchschmidt J, Fried J, Astiz M, Rackow E, Mecher C. Supranormal oxygen delivery improves mortality in septic shock patients [abstract]. Crit Care Med 1991; 19:566 10 Guyatt G, Ontario Intensive Care Study Group. A randomized control trial of right-heart catheterization in critically ill patients. J Intensive Care Med 1991; 6:91-5

7b the Editor: We have reviewed the comments by Dr Engoren and share his thoughts regarding the need for prospective studies to compare different therapeutic goals. As to his remarks concerning suboptimal performance classification and associated lowest mortality observed in groups 1 and 2, the review panel of critical care physicians concluded that these cases did not follow any logical management pattern that fit with the initial pathophysiologic measurements obtained. 1 This may imply that pulmonary artery catheterization (PAC)information was ignored or distrusted, both of which are not 1478

necessarily unusual in patients with complicated conditions. Furthermore, this analysis was never intended to be an outcome study in a population whose mortality rates are high; we attempted only to determine how PAC data are interpreted and how information is used. The selected case-mix variables were chosen to eliminate other factors that may have affected the performance grade. Undoubtedly, PAChas clearly provided insight into the metabolic and hemodynamic disturbances of septic shock. Measurements of cardiac output, blood oxygen consumption, and lactate do play a role in managing sepsis syndrome. Furthermore, measurement of PAWPmay help to differentiate between hydrostatic and pulmonary edema of the lung and thus facilitate fluid management," It remains less clear, however, whether PAC should be performed in every patient with sepsis syndrome. The impact of invasive monitoring and its measurements of physiologic variables in sepsis syndrome are not well defined and perhaps only favorably affects survival if infection is eradicated. The prognostic significance of hemodynamic and metabolic disturbances in sepsis remains controversial. Which parameter should be monitored and treated in order to improve outcome? The prognostic value of changes in oxygen uptake and the response to oxygen delivery remains unclear in different clinical situations.v' Although several studies suggest that oxygen uptake is higher in survivors than in nonsurvivors, other studies do not support this view.l5,& We agree with Dr Engoren that catheterization is unlikely to in8uence prognosis until more effective therapy is available. A strict treatment protocol based on standardization of physician skills and hemodynamically derived data accumulation is critical in any study to assist in defining efficacy of technique. The question of how capable certain physicians are in planning therapy without catheterization remains to be answered. Are there some who can do it as well without invasive monitoring? Certainly, there are subgroups of patients in whom PAC reveals otherwise unobtainable information. Further work is needed in large samples of patients with emphasis on outcome of clinical importance. An additional study to distinguish those patients whose hemodynamic status can be reliably predicted noninvasively from those whose hemodynamic status is unpredictable is warranted, the latter patients being more likely to benefit from invasive hemodynamic monitoring. jay S. Steingrob, M.D., and

Daniellms, M.D.,

BaystateMedical Center; 'fufts University School of Medictne, Springfield, MtlS8QChusett8 Reprint requests: Dr Stei~rub, Critical Care Divi.rion, BayBtate Medical Center, Springfield, MA 01199. REFERENCES

1 Steingrub JS, Celoria G, Vickers-Lahti M, Teres D, Bria W Therapeutic impact of pulmonary artery catheterization in a medical/surgical ICU. Chest 1991; 99:1451-55 2 Fein AM, Goldberg SIC, Walkenstein MD, Dershaw B, Braitman L, Lippman ML. Is pulmonary artery catheterization necessary for the diagnosis of pulmonary edema? Am Rev Respir Dis 1984; 129:1006-09 3 Abraham E, Bland RD, Coho JC, Shoemaker WC. Sequential cardiorespiratory patterns associated with outcome in septic shock. Chest 1989; 85:75-80 4 Wolf VG, Cotev S, Perel A, Manny J. Dependence of oxygen consumption on cardiac output in sepsis. Crit Care Med 1981; 15:198-203 5 Groeneveld ABJ, Kester ADM, Nauta JJ~ Thijs LG. Relation of arterial blood lactate to oxygen delivery and hemodynamic variables in human shock states. Cire Shock 1987; 22:35-53 6 Bihari D, Smithies M, Gimson A, Tinker J. The effects of vasodilation with prostacyclin on oxygen delivery and uptake in critically ill patients. N Engl J Moo 1987; 317:397-403 Convnunications to the EcItor