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The Use of Hemodynamic Monitoring in Vascular Patients

C. O. Brantigan MD

A randomized prospective study is not required to prove that well informed surgeons who are clinical physiologists will do better for their patients than those who lack full respect for data available for the asking in most modern hospitals ......Benfield, 1981 .

Patient Population Requiring Invasive Monitoring:

Patients with vascular disease that will benefit from hemodynamic monitoring in the perioperative period are those who are critically ill or who have metastable problems with their cardiac, cerebral or renal circulations. Patients with aortic disease with comorbid conditions and limb salvage patients are candidates because of the high incidence of coronary disease and the high incidence of other major medical problems.

Although these patients have a high incidence of diabetes, hypertension, renal disease, chronic obstructive pulmonary disease from smoking, pulmonary hypertension and polypharmacy, the impact of coronary disease is the most studied of the comorbid conditions.

Coronary Artery Disease

Hertzer (1984) reported a series of 1000 patients with vascular disease who underwent coronary arteriography. These were elective vascular patients--neither those presenting significant coronary symptoms nor those presenting as limb salvage candidates were included. The procedures required were generally aortic or femoropopliteal reconstructions.

Findings of Coronary Arteriography

Normal 8%
Mild/moderate

32%

Diseased/compensated

29%

Severe/correctable

25%

Severe/inoperable

6%

Thus 92% of these patients had coronary disease. Limb salvage patients have not been studied so systematically, but when they have been studied, the incidence of severe coronary disease is even higher. The prudent surgeon assumes that all of the limb salvage patients and complex aortic reconstruction patients have significant coronary artery disease. Hertzer believed that coronary revascularization should precede vascular reconstruction, but the mortality of the coronary therapy was greater than the vascular procedure, and the only subgroup of coronary surgical survivors had any long term benefit were non-diabetic men. All other groups showed no increase in survival .

Peripheral vascular disease is a marker for increased mortality independent of the coronary disease. The Coronary Artery Surgery Study (CASS 1994) noted that markers of peripheral vascular disease predicted a 25% increase in death rate for all groups (surgery or not) at any point in time after controlling for other factors. Most of these patients did not have vascular disease severe enough to consider surgery, and were thus a healthier group than limb salvage patients. Peripheral vascular disease is also an independent predictor of death after coronary bypass. Patients with clinical and subclinical markers of vascular disease in the data from the Northern New England Cardiovascular disease Study Group experienced a 2.4 fold increase in mortality and had a 73% higher chance of dying during a hospitalization for coronary artery bypass (CABG) than those without such markers. Survivors of the coronary artery surgery died at an increased rate as well. Vascular patients experienced a 20% mortality compared of 8% at 5 years. As a result the authors questioned the role of CABG in these patients. Again, this was not a group of patients with severe PVD, and thus underestimates the problems faced by patients requiring surgery for complex aortic disease or limb salvage.

As peripheral vascular disease patients go, those treated in our practice are sicker than those seen by most vascular surgeons because of the high incidence of limb salvage surgery in our patients. This was strikingly demonstrated in the multi-institutional study of Cryoveins that was reported at the Society for Vascular Surgery in 1999 with Brantigan as the principal investigator .

Physiologic Problems in Vascular Patients.

The importance of adequate intravascular volume, cardiac function and appropriate vascular tone in vascular surgical patients has been known for many years, and was discussed by Grow and colleagues in the 1960's . Vascular surgeons have based their operations on physiologic studies and have conceived of their perioperative management in physiologic terms since vascular surgery became a specialty. The most successful surgeons have always prepared their patients well and have based their management decisions on physiologic parameters. How is a patients cardiopulmonary physiology best understood? Can it be accurately determined based on physical examination and lab tests with the missing pieces assumed, or must it be measured in some other way?

Brantigan (1980, 1982) studied the incidence of hemodynamic abnormalities in the perioperative period, and characterized the incidence and impact in 52 consecutive patients, predominately with vascular reconstructions. There was no significant catheter associated morbidity. The following abnormalities were observed:

PAWP/CVP Discrepancies

33%

Cardiac Performance Problems

11.5%

SVR Problems

30.8%

Along the way he noted that vasoconstriction led to a decreased flow in the bypass grafts and an increased incidence of perioperative thrombosis. The importance of flow in keeping bypasses open is a well known phenomenon. During that time period hypothermia and common use of vasoconstricting antihypertensives such as thiazide diuretics and beta blockers were important contributing factors that have been ameliorated by having temperature control in the operating room and by the newer antihypertensives. Brantigan characterized the impact of invasive monitoring on these patients as follows:

Detrimental

0%

No benefit

17%

Helpful (less worry for physician, less calls at night etc)

19%

Therapy change mandated by measurements

37%

Potentially life saving change in therapy

27%

Del Guercio reported similar studies on 75 routine vascular patients with the similar results in 1982 . Unlike Brantigan, he included preload problems predictable using just a CVP, but found the following abnormalities:

Normal Hemodynamics

33.3%

Preload problems

26.7%

Poor LV function

17.3%

High afterload

13.3%

Combination of above

9.3%

While certainly some physicians are more skilled in the intuitive assessment of their patients, and some anesthesiologists are more able to tune patients hemodynamics during the early stages of an operation, many studies over time have documented that in high risk patients details of their physiology can not be accurately estimated without direct measurements. It is not possible to distinguish patients who are volume depleted from those who need inotropic support of vasodilation for optimization on clinical grounds alone. The question "does it matter," strikes at the very core of the theoretical underpinning of what we do as vascular surgeons.

Hemodynamic Tuning Algorythm

Based on these data, Brantigan began to admit patients to the ICU for preoperative tuning if they were sick aortic patients or were limb salvage patients. They were tuned using the following algorithm:

Preload was adjusted first using volume loading or diuresis and vasodilators. Attention was then turned to the LVSW and SVR and these were adjusted. On the diagram above the high LVSW is included to balance the diagram--the only time this is seen is in delirium tremens, thyroid storm and occasionally in acute myocardial infarctions. It is acknowledged that balancing these factors is like balancing the legs of a three legged stool, and that repeated modifications are needed as the adjustment of one parameter affects the other.

The goal is to send a patient to the operating room with a cardiac index of >2, a SVR of about 1000 and a PAWP optimized based on urine output and cardiac output. Patients commonly are taken to the operating room on a nitroprusside drip or a nitroglycerin drip. Inotropes are not unusual, and even patients with bad ejection fractions can be well managed if their cardiac index can be easily kept above 2 with a combination of inotropic support and vasodilation. The strategy is to achieve cardiopulmonary function sufficient to tolerate the operation. The strategy of maximizing cardiac function has been proven detrimental.

Most anesthetics vasodilate particularly epidurals, which are particularly advantageous for vascular patients, as they maximize flow thru the grafts during the perioperative period. As the anesthetic is dialed in preoperative nitroglycerine or nitroprusside are dialed down. As the patient recovers from anesthesia the process is reversed. Distal bypass patients are then switched to oral medications to maintain the same parameters in much the way that cardiologists use what Braunwald characterized as "tailored therapy" for heart failure patients. In patients with significant third space losses and compromised cardiac function, patients are kept in the ICU until they demonstrate their ability to handle fluid as they mobilize it.

Results

Compared with published series, our patients have comparable success rates, but the incidence of unfavorable anatomy is higher and the patients are sicker, as judged by their higher long term mortality.

Brantigan discussed this strategy at Wound Care Center National meetings and David Knighton then studied the effect of this treatment strategy on distal bypass patients. His was a randomized trial of the effect of preoperative tuning on the outcome of limb salvage surgery in 89 patients and was published in 1991 . Excluded were patients who:

  • Had a MI within the last 3 months
  • Had a CABG within the last 6 weeks
  • Had clinical congestive heart failure
  • Had unstable angina

All patients were operated upon by the same surgeon and all had anesthesia administered using identical techniques. End points for tuning were:
   PAWP 8-15 mm Hg
   CI >2.8
   SVR <1100

Of the patients tuned:
   36.8% met criteria without intervention
   26.4% required volume loading alone
   36.8% required inotropes and or vasodilators with or without
       fluid loading

The patients tuned before surgery had fewer adverse events during surgery, less cardiac morbidity, less early graft thrombosis and a lower mortality (1.5% vs. 9.5%) (All p<.05). There was no increase in ICU LOS, hospital LOS, hospital costs compared to controls. The per cent of hospital costs attributed to complications was higher in the control group. Note that this is a study not of Swan Ganz catheters, which would be inappropriate, but rather is a study of a management strategy based on hemodynamic parameters.

Preoperative Tuning or the Importance of Early Intervention

The importance of preoperative hemodynamic tuning or at least early intervention in high risk patients has been emphasized repeatedly. This is particularly true in aortic reconstructions.

Shoemaker, in a widely quoted randomized study , established physiologic goals for management of high risk patients and then studied the effect of achieving these goals during the perioperative period. The goals were achieved in 68% of patients by volume adjustment, 25% by adding dobutamine and 7% by adding nitroprusside in a strategy similar to the algorithm above.

Although the control patients with a pulmonary artery catheter experienced a 25% decrease in mortality the other variables were the same between patients managed using the CVP catheters and pulmonary artery catheters. Clearly the therapeutic strategy made the difference. Insertion of a catheter is not therapy.

Shoemaker concluded, "...most surgical patients do rather well. Overall mortalities of less than 2% in major surgery are usually considered acceptable in most hospitals. Hence, most surgeons are unwilling to depart from their well-organized routines until it is obvious that something has seriously gone wrong. By this time, lethal postoperative complications may already have begun, and it is too late for early, much less prophylactic, therapy. Preoperative identification of high risk patients and the use of prophylactic monitoring to optimize circulatory function generally have not been accepted. Moreover, the concept has been only slowly appreciated that the high risk patient could be identified before surgery by clinical criteria [read hemodynamic criteria] and that the majority of surgical deaths and organ failures could be prevented by prophylactic therapy that augmented compensatory responses to tissue hypoxia." At one point during his series of studies, an institutional decision was made to ban preoperative inserting of Swan-Ganz catheters. The death rate returned to control levels and the same number of Swan-Ganz catheters were used in the end, but to treat problems rather than to anticipate them. Boyd and Hayes also emphasized the importance of early intervention. In a meta analysis of six randomized studies of hemodynamic paramater driven therapy they found significant outcome improvement in high-risk patients with early therapy directed to achieving optimal goals .

Many studies have emphasized the importance of volume loading in preparation for aortic surgery . This is best accomplished preoperatively using hemodynamic monitoring. With monitor guided volume loading the incidence of hypotensive episodes is decreased, renal dysfunction is decreased and mortality decreases as well (Hesdorfer et al 1987) . None of the other strategies of renal protection, such as administration of mannitol, lasix or ACE inhibitors has been as effective. Bertolissi (1998) in discussion prevention of renal failure in major vascular surgery emphasized that "Optimal management of the cardiovascular function by means of invasive hemodynamic monitoring is the main tool to protect the kidneys and prevent renal failure" in vascular patients. Preoperative preparation is better than catch up during surgery. Amin and Iberti described why that would be in 1990 and the principles are true to the present:

  • "Despite what is frequently published, every medication, especially the inotropes, may have markedly different effects in different patients."
  • "Commonly the initial hemodynamic profile does not reflect the patient's true baseline due to anxiety and stress, and a longer period of time may be required" for an adequate understanding of the patients physiology and response to interventions.
  • "Contrary to the maximization philosophy (attempting to achieve the highest possible cardiac output), it is a better approach to have the patient meet his/her oxygen requirement using the least possible cardiac work." and this takes time.

In recent years there has been an increasing call for a randomized control trial of the Swan Ganz catheter. Some investigators have insisted that there be a moratorium on the use of these catheters until their use is validated by such a trial. Insertion of a Swan Ganz Catheter allows acquisition of data. Acquisition of data, per se does not change outcome unless either there is morbidity associated with the acquisition of the data or the data is used to direct therapy. Morbidity associated with insertion and maintenance of the catheter should be minimal assuming competent intensivists and nursing staff. Most of the morbidity of hemodynamic monitoring results from either a lack of understanding of the data or its misapplication. Attempts to determine the competence of physicians using hemodynamic monitoring have been disappointing. When standardized testing of basic knowledge have been given, one third to one half of the questions have been answered incorrectly . That level of misunderstanding is a credentialing problem that is nationwide. Studies noted above validate the management strategies described above.

Conclusions

The importance of preoperative preparation of a patient for major surgery has been known for many years. The concept is taught in medical school. The concepts were discussed in the American College of Surgeons Manual of Preoperative and Postoperative care in the 1960's . Invasive monitoring allows us to measure and quantify the physiology that we are trying to modify. Used accurately and thoughtfully in the appropriate patient, this strategy decreases mortality and morbidity and increases graft patency.

Dr Brantigan wrote this article in December 2001.

References:

1 This quote is from a reliable source--my slides. I cant for the life of me find the original source. It has to be from a discussion of monitoring in aortic surgery.

2 Hertzer, N et al, Coronary artery disease in peripheral vascular patients, Ann Surg (1984) 199:223-233.

3 Hertzer, N, discussion in Cutler, BS, Leppo, JA, Dipyridamole thallium 201 scintigraphy to detect coronary artery disease before abdominal aortic surgery, J Vasc Surg (1987) 5:91-100.

4 Eagle, K, Rihal, CS, Foster, ED et al, Long-term survival in patients with coronary artery disease: Importance of peripheral vascular disease, J Am Coll Cardiol (1994) 23:1091-5.

5 Birkmeyer, JD et al, The effect of peripheral vascular disease on in-hospital mortality rates with coronary artery bypass surgery. Northern New England Cardiovascular Disease Study Group. J Vasc Surg (1995) 21:445-52.

6i Brantigan, CO et al, Revascularization of the Lower Extremity with Cryopreserved Saphenous Vein: a Multicenter Clinical Experience, Poster Session, International Society for Cardiovascular Surgery, Washington, DC, June 1999.

7 Wilson, J.N., Grow, J.B., Sr., Demong, C.V., Prevedel, A.E., Owens, J.C.: Central Venous Pressure in Optimal Blood Volume Maintenance. Arch Surg 5:55, 1962.

8 Symposium on Hemodynamic Monitoring, Denver CO, March 28, 1980.

9 Brantigan CO, Hemodynamic monitoring: A technique for critical care nurses. Am J Nurs 82:86-89, 1982.

10 Babu, S, Sharma, P, Raciti, A, Mayr, CH, Elrabie, NA, Clauss, RH, Stahl, WM, DelGuercio, LM, Monitor-Guided responses; operability with safety is increased in patients with peripheral vascular diseases, Arch Surg (1980) 115:1384-86.

11 Braunwald, E, Heart Disease, WB Saunders, Philadelphia 1997 p 508.

12 Berlauk, JF, Abrams, JH, Gilmour, IJ, O'Connor, SR, Knighton, DR, Cerra, FB, Preoperative optimization of cardiovascular hemodynamics improves outcome in peripheral vascular surgery, Ann Surg (1991) 214:289-299.

13 Shoemaker, WC, Kram, HB, Appel, PL, Fleming, The efficacy of central venous and pulmonary artery catheters and therapy based upon them in reducing mortality and morbidity, Arch Surg (1990) 125:1332-8.

14 Boyd, O, Hayes, M, The Oxygen trail: the goal Br Med Bull 1999;55:125-139.

15 Grindlinger, GQ, Vegas, AM, Manny, J, Bush, HL, Mannick, JA, Hechtman, HB, Volume loading and vasodilators in abdominal aortic aneurysmectomy, Am J Surg (1980) 139:480-6.

16 Whittemore, AD, Clowes, AW, Hechtman, HB, Mannick, JA, Aortic aneurysm repair; reduced operative mortality associated with maintenance of optimal cardiac performance, Ann Surg (1980) 192: 414-21.

17 Hesdorfer, CS, Milne, JF, Meyers, AM, Clinton, C, Botha, R, The value of Sawn-Ganz catheterization and volume loading in preventing renal failure in patients undergoing abdominal aneurysmectomy, Clinical Nephrology (1987) 28:272-6.

18 Bertolissi, M, Prevention of acute renal failure in major vascular surgery, Minerva Anesthesiol (1998) 65: 867-877.

19 Amin, D, Iberti, TJ, Use of the surgical intensive care unit in the preoperative preparation of the high risk patient, J Cardiothoracic Anesthesia (1990) 4: Suppl1, 13-18.

20 Iberti, TJ, Fischer, EP, Leibowitz, AB, Panacek, EA, Silverstein, JH, Albertson, TE, and the Pulmonary Artery Catheter Study Group, A multicenter study of physician's knowledge of the pulmonary artery catheter, JAMA (1990) 264:2928-32.

21 Randall, HT, Hardy, JD, Moore, FD, Manual of preoperative and postoperative care, American College of Surgeons, WB Saunders, 1967.


2003-2004 Dr. Charles Brantigan,  Vascular Surgery Practice
2253 Downing Street, Denver, CO 80205
303.830.8822 fax: 303.830.7068 or 800.992.4676  inquiries@drbrantigan.com

Last Updated: 07/15/2004