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Anesth Analg 2002;95:273-277
© 2002 International Anesthesia Research Society

CARDIOVASCULAR ANESTHESIA

Intraoperative Tachycardia and Hypertension Are Independently Associated with Adverse Outcome in Noncardiac Surgery of Long Duration

David L. Reich, MD, Elliott Bennett-Guerrero, MD, Carol A. Bodian, DrPH, Sabera Hossain, MSc, Wanda Winfree, RN, and Marina Krol, PhD

Department of Anesthesiology, Mount Sinai School of Medicine, New York, New York

Address correspondence and reprint requests to David L. Reich, MD, Professor of Anesthesiology, Mount Sinai School of Medicine, One Gustave L. Levy Place, Box 1010, New York, NY 10029-6574. Address e-mail to david.reich{at}mssm.edu


   Abstract
Top
 Abstract
Introduction
 Methods
 Results
 Discussion
 References
 
Relatively little is known about the influence of intraoperative hemodynamic variables on surgical outcomes. We drew subjects (n = 797) from a study of patients undergoing major noncardiac surgery. The physiological component of the POSSUM (Physiological and Operative Se- verity Score for the enUmeration of Mortality) operative risk stratification index was determined, and intraoperative measurements of heart rate (HR), mean arterial blood pressure, and systolic arterial blood pressure (SAP) were retrieved from computerized anesthesia records. For every 5-min epoch during the surgery, HR, mean arterial blood pressure, and SAP were each classified as low, normal, or high. Negative surgical outcome (NSO) was defined as a hospital stay of >10 days with a morbid condition or death during the hospital stay. Statistical analyses included Mantel-Haenszel tests and multiple logistic regression. There was no significant association between hemodynamic variables and NSO with short operations. In 388 patients with operations longer than the median time of 220 min, NSO occurred in 15.6%. Controlling for POSSUM score and operation time beyond 220 min, both high HR (odds ratio, 2.704; P = 0.01) and high SAP (odds ratio, 2.095; P = 0.009) were associated with NSO in longer operations. Thus, intraoperative tachycardia and hypertension were associated independently with adverse outcomes after major noncardiac surgery of long duration, over and above the risk imparted by underlying medical conditions.

IMPLICATIONS: Intraoperative tachycardia and hypertension were associated with negative postoperative outcomes after major noncardiac surgery of long duration. These results imply that intraoperative tachycardia and hypertension may have independent effects on outcome over and above the risk imparted by underlying medical conditions.


   Introduction
Top
 Abstract
 Introduction
Methods
 Results
 Discussion
 References
 
Although blood pressure and heart rate (HR) are closely monitored during surgery, relatively little is known about the associations of abnormalities of HR and blood pressure with outcome indicators, such as morbidity and mortality. Although numerous studies have examined the relationship between preoperative risk factors and adverse outcomes, the effect of intraoperative hemodynamic abnormalities on adverse outcomes has been less well defined (1–3). In many studies, measurements of intraoperative hemodynamics have been limited to intraoperative blood pressure nadir, steady-state pre- and postoperative measurements, and blood pressure above and below defined limits of normality for specified time intervals (1–4).

The results of some previous studies (1–3) have been difficult to interpret because they limited their statistical analyses to univariate tests. Statistical methods that assess the independent effects of the intraoperative hemodynamic aberrations on the risk of morbidity and mortality after adjusting for the effects of underlying medical conditions are required. For example, intraoperative hypertension may be a marker for essential hypertension, such that intraoperative blood pressure deviations may or may not add additional risk beyond that of the underlying condition of essential hypertension.

The advent of computerized anesthesia information systems provides the opportunity to record and store intraoperative hemodynamic data with great accuracy (5–8). By use of such systems, the independent associations between intraoperative hemodynamic abnormalities and death, stroke, and perioperative myocardial infarction in cardiac surgical patients have been published (9,10). The purpose of this investigation was to determine whether intraoperative aberrations of blood pressure or HR were associated with perioperative mortality or major morbidity in patients undergoing complex noncardiac surgery while controlling for the influence of major coexisting medical illness.


   Methods
Top
 Abstract
 Introduction
 Methods
Results
 Discussion
 References
 
The study was institutionally approved as a retrospective investigation. Subjects (n = 797) were drawn from a group of 1056 patients who had participated in an IRB-approved anesthesia outcome study of patients undergoing major elective noncardiac surgery at one institution (11). The IRB waived the requirement for informed consent.

Patients undergoing the following elective surgical procedures were enrolled: major orthopedic (e.g., revision hip arthroplasty, fusion/instrumentation of multiple lumbar or thoracic vertebrae); major general (e.g., any laparotomy expected to exceed 2 h, including partial hepatectomy, pancreatic surgery, and colon surgery); major urological (e.g., radical cystectomy, radical nephrectomy); major vascular (e.g., abdominal aortic aneurysm repair); and major gynecological (e.g., cancer debulking procedure, abdominal hysterectomy with oophorectomy). These procedures were selected for several reasons: 1) they are routinely performed surgeries, 2) they represent a diverse group of procedure types, and 3) a previous study performed at Duke University Medical Center found these procedures to be associated with prolonged hospitalization and postoperative complications (12). Study patients received routine anesthetic care and surgical management. Each patient was treated after surgery according to standard institutional surgical "care maps"; only patients undergoing surgical procedures enabling them to be targeted for discharge from the hospital before the 10th postoperative day were enrolled.

To quantify perioperative risk of morbidity and mortality due to underlying medical conditions, the physiological component of the POSSUM (Physiological and Operative Severity Score for the enUmeration of Mortality) operative risk stratification index (13) was determined for each patient. The POSSUM criteria have been cited as the most appropriate scoring system available for assessing risk in noncardiac surgical patients (14). The POSSUM physiological score includes 12 preoperative factors (including age, preoperative blood pressure, cardiac disease, and renal function). A point value of 1, 2, 4, or 8 was assigned for 10 of the 12 factors, depending on the severity of the abnormality (e.g., 1 point for no dyspnea and 8 points for dyspnea at rest). The POSSUM score was obtained by prospective evaluation in the operating room before surgery by a trained anesthesia research nurse.

A subset of patients from the original study had undergone surgery in operating rooms with computerized anesthesia information systems (CompuRecord; Philips, Andover, MA). Every patient with a valid computerized anesthesia record (n = 797) from the original study (n = 1056) was included in this study. Intraoperative hemodynamic data were derived from these computerized anesthesia records that automatically stored hemodynamic values every 15 s. HR, mean arterial blood pressure (MAP), systolic arterial blood pressure (SAP), and diastolic arterial blood pressure were extracted from the computerized anesthesia records. The raw data obtained every 15 s may contain artifactual values because of intermittent electrocautery interference and transducer flushing, among other causes. Therefore, the data were filtered for such artifacts by using the median value in consecutive 5-min epochs.

With Microsoft Access (Microsoft, Inc., Redmond, WA), we quantified the extent and duration of abnormal hemodynamic states during the anesthesia. For every 5-min epoch, the median HR, MAP, and SAP was classified as low, normal, or high, according to criteria derived from the results of a survey of 39 anesthesiologists (Table 1) (15). For each hemodynamic variable, the proportion of 5-min epochs in which the median value was classified into an abnormal hemodynamic category was calculated. Each hemodynamic variable was evaluated at every 5-min epoch in an independent fashion. Thus, it was possible for patients to experience epochs that were classified as high at one interval and low at another interval in the same surgical procedure.


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  		Table 1. Table 1. Criteria Used to Define Abnormal Hemodynamics
 
The primary composite end point, negative surgical outcome (NSO), was a postoperative hospital length of stay of >10 days with a morbid condition or death during the same hospitalization after surgery. A research nurse reviewed the chart of every patient who remained an inpatient on the 11th postoperative day. At that time, the research nurse noted the presence or absence of postoperative morbidity of the following types: gastrointestinal, pulmonary, renal, infectious, wound complication, pain, cardiovascular, neurological, or hematological. The criteria for defining these morbid states have been published previously (10,16). The patients were observed until discharge, and all deaths during hospitalization were noted.

The composite outcome variable (NSO) was the sole outcome variable analyzed. Data for the derived hemodynamic abnormalities were summarized to identify outliers and to characterize the distributions of these variables. Bivariate contingency tables were created to examine the association between outcome and each hemodynamic measure. Significance levels were determined by {chi}2 tests for trend or by Fisher’s exact test, as appropriate. Each derived hemodynamic variable with a P value of <0.20 was considered a potential independent predictor. Mantel-Haenszel tests and multiple logistic regression were then used to test the independent influence of these associations while controlling for risk due to medical conditions.


   Results
Top
 Abstract
 Introduction
 Methods
 Results
Discussion
 References
 
The median operation length in this cohort was 220 min. Patient characteristics and surgical outcomes are described in Table 2. One-hundred-twenty-four patients had an NSO, including 13 who died in the hospital up to Day 10. Of the patients who remained hospitalized on the 11th postoperative day, 111 of 154 (72.1%) had a morbid condition. There was a strong association between POSSUM score and NSO in patients undergoing operations lasting <220 min and >220 min (P < 0.001 for each). These results are displayed in Table 3.


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  		Table 2. Table 2. Perioperative Patient Characteristics
 

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  		Table 3. Table 3. Incidence of Negative Surgical Outcome Stratified by Operation Length, Stratified on Physiological POSSUM Score
 
Preliminary analyses using bivariate contingency tables did not reveal any consistent trends in rate of NSO with increasing frequency of hemodynamic aberrations. Thus, in all further analyses, the hemodynamic variables (MAP, SAP, and HR) were included as binary variables—any patient who experienced any of these aberrant conditions for any amount of time was considered positive for that variable.

We used Mantel-Haenszel tests to look for an association between the occurrence of each hemodynamic condition and NSO, controlling for the influence of POSSUM scores. There were no strong associations between hemodynamic abnormalities and NSO in the cohort undergoing operations <220 min in duration, and this group was not analyzed further. In 388 patients with operations >220 min, increased HR (P = 0.044; Table 4) and increased SAP (P = 0.034; Table 5) were each associated with NSO. The proportion of patients experiencing NSO was larger for patients experiencing low MAP in all but the highest quartile of POSSUM scores (Table 6). We further noted that there was a strong association between decreased MAP and increased HR.


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  		Table 4. Table 4. Incidence of Negative Surgical Outcome (NSO) by High Heart Rate, Stratified on POSSUM Physiological Score in Long Operations (>220 minutes)
 

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  		Table 5. Table 5. Incidence of Negative Surgical Outcome (NSO) by High Systolic Arterial Blood Pressure, Stratified on POSSUM Physiological Score in Long Operations (>220 minutes)
 

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  		Table 6. Table 6. Incidence of Negative Surgical Outcome (NSO) by Low Mean Arterial Blood Pressure, Stratified on POSSUM Physiological Score in Long Operations (>220 minutes)
 
The confounding effect of decreased MAP and increased HR was apparent in the multiple logistic regression analyses. Although each contributed significantly when considered without the other, increased HR was the stronger predictor. The independent influence of increased HR and increased SAP in operations >220 min is shown in the multiple regression results (Table 7). These results are consistent with those noted in the Mantel-Haenszel tests.


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  		Table 7. Table 7. Multivariate Analysis of Negative Surgical Outcome in Long Operations (>220 minutes)
 

   Discussion
Top
 Abstract
 Introduction
 Methods
 Results
 Discussion
References
 
This study investigated associations between hemodynamic variables measured in the course of complex noncardiac surgery, and poor postoperative outcome. Preoperative risk assessment with the POSSUM physiological score was included in the model to examine the additional effects of intraoperative hemodynamic aberrations on poor postoperative outcome, over and above the influence of the factors that existed when patients were brought to surgery. The POSSUM physiological score reflects the presence of preoperative hypotension, hypertension, tachycardia, and bradycardia. Thus, our findings suggest that intraoperative tachycardia and hypertension during long, complex noncardiac surgery may partially explain the variability in outcome seen among patients with similar degrees of preoperative risk.

There are very few reports of independent associations of intraoperative hemodynamic aberrations with complications. Jain et al. (9) reported that SAP <90 mm Hg after cardiopulmonary bypass was an independent predictor of perioperative myocardial infarction. In a previous study at two institutions (including the authors’), we identified independent associations between various hemodynamic aberrations, including increased pulmonary artery diastolic pressure, with death, stroke, and myocardial infarction after coronary artery bypass surgery (9).

A potential limitation of our study relates to the selection of the primary end point as a composite of mortality and prolonged postoperative hospitalization with morbidity. Mortality is the most important end point, but it is relatively infrequent compared with morbidity in this group of surgical patients. We chose prolonged postoperative hospitalization with morbidity because the presence of both strongly suggests that the prolonged hospitalization was due to the morbid condition (12). Furthermore, if the morbidity resulted in a prolonged hospitalization, it also has a greater economic effect.

A major question not addressed by this study is the reason for the association of brief periods of hemodynamic abnormalities with complications that are overwhelmingly noncardiac. The majority of the morbidity observed in patients with prolonged hospitalization in our study involved organ systems unrelated to the type or site of surgery. Infectious, pulmonary, and renal complications were observed frequently. Hemodynamic predictors of adverse outcome identified in this study may not be the primary causes. They may be markers of pathophysiological states that caused the complications but are not reflected in the POSSUM physiological score or the anesthesia record. For example, high HR could represent hypovolemic states with inadequate tissue perfusion, due to causes such as hemorrhage, endotoxemia, or exaggerated inflammatory responses to surgery (16). The confounding effect noted between decreased MAP and increased HR further suggests that hypovolemia may be the underlying cause of the hemodynamic aberrations that were associated with complications.

This observational study allowed us to identify hemodynamic abnormalities associated with adverse outcomes in patients undergoing treatment by experienced teams of anesthesiologists and surgeons. The hemodynamic changes observed in these patients occurred despite attempts to maintain normal hemodynamic status during surgery. It does not necessarily follow, however, that more aggressive therapy aimed at normalizing hemodynamics would improve outcome. A randomized clinical trial would be required to test the latter hypothesis.

Another limitation of the study was the categorization of hemodynamic variables into normal and abnormal groups on the basis of limits defined by a survey of clinicians. The choice of absolute limits rather than relative changes from baseline was based on our concern that we could not establish the true baseline values in these patients in the perioperative period.

In conclusion, specific intraoperative hemodynamic aberrations were independently associated with poor postoperative outcome, as reflected by mortality or prolonged postoperative hospitalization with morbidity. These findings demonstrate the prognostic relevance of intraoperative hemodynamic status over and above the effects of certain preoperative risk factors. The question of whether outcomes could be improved by greater control of intraoperative hemodynamic variables awaits prospectively designed studies. These additional studies would be justifiable on the basis of the expense of current health care resources that must be devoted to caring for patients with poor postoperative outcomes.


   References
Top
 Abstract
 Introduction
 Methods
 Results
 Discussion
 References
 

  1. Goldman L, Caldera DL. Risks of general anesthesia and elective operation in the hypertensive patient. Anesthesiology 1979; 50: 285–92.[ISI][Medline]
  2. Prys-Roberts C, Meloche R, Foex P. Studies of anaesthesia in relation to hypertension. I. Cardiovascular responses of treated and untreated patients. Br J Anaesth 1971; 43: 112–37.
  3. Charlson ME, MacKenzie CR, Gold JP, et al. Preoperative characteristics predicting intraoperative hypotension and hypertension among hypertensives and diabetics undergoing noncardiac surgery. Ann Surg 1990; 212: 66–81.[Medline]
  4. Mauney FM, Ebert PA, Sabiston DC. Postoperative myocardial infarction: a study of predisposing factors, diagnosis and mortality in a high risk group of surgical patients. Ann Surg 1970; 172: 497–502.[ISI][Medline]
  5. Hollenberg HP, Pirraglia PA, Williams-Russo P, et al. Computerized data collection in the operating room during coronary artery bypass surgery: a comparison to the hand-written anesthesia record. J Cardiothorac Vasc Anesth 1997; 11: 545–51.[Medline]
  6. Lerou JG, Dirksen R, van Daele M, et al. Automated charting of physiological variables in anesthesia: a quantitative comparison of automated versus handwritten anesthesia records. J Clin Monit 1988; 41: 37–47.
  7. Cook RI, McDonald JS, Nunziata E. Differences between handwritten and automatic blood pressure records. Anesthesiology 1989; 71: 385–90.[ISI][Medline]
  8. Reich DL, Wood RK, Mattar R, et al. Arterial blood pressure and heart rate discrepancies between handwritten and computerized anesthesia records. Anesth Analg 2000; 91: 612–6.[Abstract/Free Full Text]
  9. Jain U, Laflamme CJA, Aggarwal A, et al. Electrocardiographic and hemodynamic changes and their association with myocardial infarction during coronary artery bypass surgery. Anesthesiology 1997; 86: 576–91.[ISI][Medline]
  10. Reich DL, Bodian CA, Krol M, et al. Intraoperative hemodynamic predictors of mortality, stroke and myocardial infarction following coronary artery bypass surgery. Anesth Analg 1999; 88: 814–22.
  11. Bennett-Guerrero E, Panah MH, Barclay GR, et al. Decreased endotoxin immunity is associated with greater mortality and/or prolonged hospitalization after surgery. Anesthesiology 2001; 94: 992–8.[ISI][Medline]
  12. Bennett-Guerrero E, Welsby I, Dunn TJ, et al. The use of a postoperative morbidity survey to evaluate patients with prolonged hospitalization after routine, moderate-risk, elective surgery. Anesth Analg 1999; 89: 514–9.[Abstract/Free Full Text]
  13. Copeland GP, Jones D, Walters M. POSSUM: a scoring system for surgical audit. Br J Surg 1991; 78: 355–60.[Medline]
  14. Jones HJ, de Cossart L. Risk scoring in surgical patients. Br J Surg 1999; 86: 149–57.[ISI][Medline]
  15. Reich DL, Pavone L, Bennett-Guerrero E, Krol M. How do anesthesiologists define abnormal heart rate and blood pressure [abstract]? Anesth Analg 1999; 88: S192.
  16. Bennett-Guerrero E, Ayuso L, Hamilton-Davies C, et al. Relationship of preoperative antiendotoxin core antibodies and adverse outcomes following cardiac surgery. JAMA 1997; 277: 646–50.[Abstract]
Accepted for publication April 5, 2002.




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Lippincott, Williams & Wilkins Anesthesia & Analgesia® is published for the International Anesthesia Research Society® by Lippincott Williams & Wilkins with the assistance of Stanford University Libraries' HighWire Press®. Copyright 2006 by the International Anesthesia Research Society. Online ISSN: 1526-7598   Print ISSN: 0003-2999 HighWire Press