A Model for Clinical Estimation of Perioperative Hemorrhage

Transcription

1 Clin Appl Thrombosis/Hemostasis 9(2): , Westminster Publications, Inc., Glen Head, NY A Model for Clinical Estimation of Perioperative Hemorrhage Christopher Howe, MD,* Christopher Paschall, MD,* Amit Panwalkar, MD,* James Beal, PhD,' and Anil Potti, MD*t Departments of *Medicine and -Hematology, University of North Dakota School of Medicine, Fargo, North Dakota; Department of Statistics, University of North Dakota, Grand Forks, North Dakota. Summary: The purpose of this study was to assess the accuracy of estimated blood loss (EBL) as a reliable predictor of actual blood loss during orthopedic procedures. Between 1999 and 2002, 198 orthopedic cases were reviewed. A retrospective review compiled preoperative and postoperative demographic and laboratory data from the surgical patients. Estimated blood loss data was-collected from the perioperative and anesthesia reports. Statistical nalysis of EBL vs. change in hemoglobin yielded a correlation e6efficient of and a p value of We used multiple linear regression to obtain a model to predict change in hemoglobin based on EBL and the intravenous fluids received. The model is as follows: predicted change in hemoglobin = x estimated blood loss (in liters) x intravenous fluids received (in liters) The study population included 198 patients, 126 males and 72 females, who met our inclusion criteria. The mean age was 68.1 years (range: SD 12.5), indud- ing 126 males (64%) and 72 females (37%). The mean amount of perioperative intravenous fluids given was 1,732 ml (SD: 773). The mean surgical time was 64.8 minutes (SD: 23.1). The mean preoperative hematocrit and hemoglobin levels were 40.9 g/dl (SD: 4.3) and 13.9 g/dl (SD: 1.6), respectively. The mean postoperative hematocrit and hemoglobin levels were 32.0 g/dl (SD: 6.0) and 10.7 g/dl (SD: 1.6), respectively. The mean difference of preoperative hemoglobin vs. postoperative hemoglobin was 3.3 g/dl (SD 2.1). In this retrospective study, clinical estimation of blood loss was closely correlated with actual change in perioperative hemoglobin. Accurately predicting the postoperative hemoglobin level may prevent many unnecessary blood transfusions and related complications. Key Words: Estimated blood loss-hematocrit-hemoglobin- Blood transfusion. The estimated blood loss (EBL) is obtained for virtually every operation. Subsequent treatment of the patient is heavily influenced by this subjective datum. Before the acquisition of a postoperative hemoglobin (Hgb) level, the EBL is commonly used to determine whether or not a patient will receive blood products perioperatively. To our knowledge the EBL has not been previously appraised for its reliability or validity. Studies have shown that gender, body weight and height are not good predictors of blood loss whereas a positive correlation exists between operative time, anesthetic technique, operative approach, exposure to nonsteroidal antiinflamma- Address correspondence and reprint requests to Anil Potti, MD, Department of Medicine, University of North Dakota School of Medicine and Health Sciences, 1919 Elm St. N., Fargo, ND 58102; apotti@medicine.nodak.edu. tory drugs, and the preoperative hemoglobin/hematocrit levels (1-9). The primary concern raised in evaluating blood loss revolves around whether or not the surgical patient requires transfusion. Allogenic transfusions must provide optimal blood perfusion for recovery of the surgery but minimized to avoid fluid overload, respect ethical/religious concerns, and reduce exposure to bloodborne pathogens (10,11). Autologous blood transfusions have their own unique risks including iatrogenic anemia, and increased cost per unit of blood when compared to allogenic blood (12-14). Interestingly, evidence is lacking that clearly shows improved outcome in transfused patients when compared to the Jehovah's Witnesses population in which the transfusion of blood products is denied (15). Guidelines for transfusion are controversial and not addressed by this study; however, by providing more information with regard to assessment and evaluation of the postoperative patient this 131

2 132 C. HOWE ETAL study seeks to allow for a more informed decision with regard to the hemodynamic state of the patient. The aims of this study were first, to identify the relationship between EBL and change in hemoglobin and second, to quantify the relationship in a manner that would be meaningful in managing hemostasis in the perioperative period. METHODS A structured PubMed search including the years 1965 to 2001 was conducted to identify English language articles examining the predictive value of estimated blood loss. Key words used in the search included blood loss, estimated blood loss, and perioperative blood loss. Patients and Measurements The study population included patients undergoing total knee and hip arthroplasty along with open reduction internal fixations (ORIF) from 1999 through 2002 at a community-based medical center. A retrospective chart analysis was performed collecting the demographics (age and sex) of the population along with pertinent laboratory data. The data included preoperative and postoperative values for hemoglobin, hematocrit, creatinine and blood urea nitrogen. The specific surgery, surgery time, amount of intravenous fluids given and estimated blood loss were obtained from operative procedure notes and the anesthesia operative notes. Patients who were given packed red blood cells prior to obtaining a postoperative complete blood cell count were excluded from the study. Statistical Analysis The clinical and demographic characteristics including amount of intravenous fluids received, preoperative and postoperative values for hemoglobin and hematocrit were described for the cohort overall. Univariate analyses estimated the associations between estimated blood loss and change in hemoglobin, hematocrit, surgical time and amount of intravenous fluids given, using the chi-square test for categorical parameters. In a similar manner, association between changes in hemoglobin and surgery time, IV fluids administered and hematocrit change was estimated using the chisquare test. A multiple linear regression was used to obtain a model to predict change in hemoglobin based on estimated blood loss and the amount of intravenous fluids received. All analysis were performed using SPSS V.10. RESULTS Review of the literature did not reveal any studies specifically analyzing the validity of EBL, a ubiquitously used clinical value. The study population included 198 patients, 126 males and 72 females, who met our inclusion criteria. The mean age was 68.1 years (range: SD 12.5), including 126 males (64%) and 72 females (37%). The mean amount of perioperative intravenous fluids given was 1,732 ml (SD: 773). The mean surgical time was 64.8 minutes (SD: 23.1). The mean preoperative hematocrit and hemoglobin levels were 40.9 g/dl (SD: 4.3) and 13.9 g/dl (SD: 1.6), respectively. The mean postoperative hematocrit and hemoglobin levels were 32.0 g/dl (SD: 6.0) and 10.7 g/dl (SD: 1.6), respectively. The mean difference of preoperative hemoglobin vs. postoperative hemoglobin was 3.3 g/dl (SD 2.1). The mean difference of preoperative vs. postoperative hematocrit was 9.3 (SD 19.1). Preoperative and postoperative blood urea nitrogen and creatinine were statistically insignificant due to the relative infrequency in which they were recorded. The study also used the above values in a comparison of total hip arthroplasty (THA) vs. total knee arthroplasty (TKA) vs. all other recorded orthopedic procedures. The results are outlined in Table 1. Patients undergoing a THA received significantly more intravenous fluids perioperatively compared to patients undergoing TKA; mean of 1,982 ml (SD 1,022) and 1,483 ml (SD 612), respectively. The difference between the mean change in hemoglobin (Hgb) between THA and TKA was minimal, 3.6 g/dl (SD 1.3) and 3.4 g/dl (SD 1.2). Statistical analysis of estimated blood loss vs. change in hemoglobin yielded a correlation coefficient of and a p value of See Table 2 for the other correlation coefficients and p values of EBL vs. change in hematocrit, surgical time, and intravenous fluids along with change in hemoglobin vs. surgical time, intravenous fluids and change in hematocrit. We used multiple linear regression to obtain a model to predict change in hemoglobin based on EBL and the intravenous fluids received. The model is as follows: predicted change in hemoglobin = x estimated blood loss (in liters) x IV fluids received (in liters)

3 CLINICAL ESTIMATION OF PERIOPERATIVE HEMORRHAGE 133 TABLE 1. Parameter Demographic and Laboratory Data for the Study Population Hip Surgery Knee Surgery Others Average Age <50 yr yr >75 yr Gender Male Female Mean IV fluids received Mean Pre-Op Hgb Mean Pre-Op Hct Mean Post-Op Hgb Mean Post-Op Hct Mean change in Hgb Mean change in Hct Mean surgical time (1022) 14.0(1.7) 41.3(5.3) 10.4(1.5) 30.5(7.8) 3.6(1.3) 11.8(7.2) 62(18.7) (612) 14.0(1.4) 41.2(3.6) 10.8(1.4) 32.1(4.0) 3.4(1.2) 9.6(5.8) 65(18.5) (443) 12.9(2.0) 38.4(5.3) 10.9(1.8) 33.0(4.5) 2.0(1.4) 5.5(4.0) years 1732(773) 13.9(1.6) 40.9(4.3) 10.7(1.6) 32.0(6.0) 3.3(2.1) 9.3( ) 64.8(23.1) Pre-Op = preoperative, Post-Op postoperative, Hgb = hemoglobin, Hct = hematocrit, IV = intravenous. TABLE 2. Correlation Coefficients and p Values for the Association Evaluated in Our Study Association Correlation Coefficients p Value EBL vs change in Hgb EBL vs change in Hct (note: we have only 91 with Post-Op Hct) EBL vs surgical time EBLvs IVF given Hgb change vs surg time Hgb change vs IVF Hgb change vs Hct change <0.01 EBL = estimated blood loss, Hgb - hemoglobin, Hct = hematocrit, IVF = intravenous fluids. The regression coefficients for the model are summarized in Table 3. DISCUSSION Review of the literature did not reveal any studies specifically analyzing the validity of EBL, a ubiquitously used clinical value. A structured PubMed search including the years 1965 to 2001 was conducted to identify English language articles examining the predictive value of estimated blood loss. Key words used in the search included blood loss, estimated blood loss, and perioperative blood loss. To our knowledge, our study is the first conducted to specifically assess EBL as a valid clinical tool. In this retrospective study, the EBL was found to be a useful indicator in change of blood volume. It may not in itself represent actual blood loss, however it

4 134 C. HOWE ETAL TABLE 3. Regression Coefficients for the Predictive Model Unstandardized Standard Standardized Parameter Coefficients Error Coefficients p Value EBL (in liters) IVF (in liters) Constant <0.01 EBL = estimated blood loss, IVF = intravenous fluids. can be used as an accurate predictor of change in hemoglobin. The formula: AHgb=1.001 x EBL(liters) x IV fluids(liters) further illustrates the usefulness of EBL in evaluating the patient's hemodynamic state. The calculated change in hemoglobin, when related to the preoperative hemoglobin, can provide accurate information regarding the current hemodynamic status of the postoperative patient. The limitations of our study include the fact that only patients undergoing orthopedic procedures were included in the study. In addition, the scope of the study was limited to data recorded by only six to eight surgeons. Similar studies in the future would benefit from expanding the scope to include non-orthopedic surgeries, and include a greater population of surgeons estimating blood loss. The formula can predict the change in hemoglobin in non-transfused orthopedic patients. Non-orthopedic patients or those patients who have received a blood transfusion were not included in the study and therefore cannot be accurately assessed using the equation. Indeed, this is one of the limitations of not only the formula, but also the study due to the high prevalence of blood transfusion (46%-84%) (3,17-19), even when EBL is minimal. Accurately predicting the postoperative hemoglobin may prevent many unnecessary blood transfusions and all the complications that lie therein. Clinically estimated blood loss appears to be an accurate predictor of postoperative hemoglobin and, when interpreted correctly, may prevent unnecessary blood transfusions and give treating physicians a clear idea of the extent of perioperative hemorrhage. There is clearly a need for more information regarding transfusion requirements concerning surgical patients. We hope that our results (with the novel formula) will contribute to the fund of knowledge concerning the management of hemostasis in the perioperative phase. REFERENCES 1. Amrein PC, Ellman L, Harris WH. Aspirin-induced prolongation of bleeding time and perioperative blood loss. JAMA 1981;245: An HS, Mikhail WE, Jackson WT, Tolin B, Dodd GA. Effects of hypotensive anaesthesia, nonsteroidal anti-inflammatory drugs, and polymethymethacrylate on bleeding in total hip arthroplasty patients. J Arthroplasty 1991;6: Bierbaum BE, Callaghan JJ, Galante JO, Rubash HE, Tooms RE, Welch RB. An analysis of blood management in patients having a total hip or knee arthroplasty. J Bone Joint Surg Am 1999;81 (1):2. 4. Clarke AM, Dorman T, Bell M. Blood loss and transfusion requirements in total joint arthroplasty. Ann R Coll Surg Engl 1992;74: Davis FM, McDermott E, Hickton C, et al. Influence of spinal and general anaesthesia on haemostasis during total hip arthroplasty. Br JAnaesth 1987;59: Modig J. Regional anaesthesia and blood loss. Acta Anaesthesiol Scand Suppl 1981;89: Modig J, Karlstrom G. Intra- and post-operative blood loss and haemodynamics in total hip replacement when performed under lumbar epidural versus general anaesthesia. Eur J Anaesthesiol 1987;4: Roberts JM, Fu FH, McClain EJ, Ferguson AB Jr. A comparison of the posterolateral and anterolateral approaches to total hip arthroplasty. Clin Orthop 1984;187: Walker RW, Rosson JR, Bland JM. Blood loss during primary total hip arthroplasty: Use of preoperative measurements to predict the need for transfusion. Ann R Coll Surg Engl 1997;79(6): Biesma DH, Marx JJM, Van De Wiel A. Collection of autologous blood before elective hip replacement. A comparison of the results with the collection of two and four units. J Bone Joint Surg 1994;76(A):1471.

5 CLINICAL ESTIMATION OF PERIOPERATIVE HEMORRHAGE Guerra JJ, Cuckler JM. Cost effectiveness of intraoperative autotransfusion in total hip arthroplasty surgery. Clin Orthop 1995;315: Birkmeyer JD, Goodnough LT, AuBuehon JP, Noordau PG, Littenverg B. The cost effectiveness of preoperative autologous blood donation for total hip and knee replacement. Transfusion 1993;33: Etchason J, Petz L, Keeler E, et al. The cost effectiveness of preoperative autologous blood donations. N Engl J Med 1995;332: Forbes JM, Anderson MD, Anderson GF, Bleecker GC, Rossi EC, Moss GS. Blood transfusion costs: A multicenter study. Transfusion 1991;31: Kitchens CS. Are transfusions overrated? Surgical outcomes of Jehovah's Witnesses. Am J Med 1993; Welch HG, Meehan KR, Goodnough LT. Prudent strategies for elective red blood cell transfusion. Ann Intern Med 1992; 116: Berman AT, Geissele AE, Bosacco SJ. Blood loss with total knee arthroplasty. Clin Orthop 1988;(234): Flordal PA, Neander G. Blood loss in total hip replacement. A retrospective study. Arch Orthop Trauma Surg 1991;111(1): Gillham M, Mark A. A retrospective audit of blood loss in total hip joint replacement surgery at Middlemore Hospital. NZ Med J 1997; 110(1049):294.