Blood Loss During Transurethral Resection of the Prostate as Measured by the Chromium-51 Method

Abstract

Purpose:

To evaluate blood loss during transurethral resection of the prostate (TURP), and its predictive factors, using the chromium 51 (51Cr) labeling method.

Patients and Methods:

From January to June 2008, 41 patients who underwent TURP for symptomatic benign prostatic hyperplasia (BPH) at four French urology centers were included in the analysis. Red cells volume was measured by the 51Cr method 1 day before TURP, and on postoperative day 3. Overall blood loss was estimated by multiplication of red cells volume loss and preoperative venous hematocrit value.

Results:

Mean preoperative red cells volume was 1997 mL. Mean loss of red cells volume was 209 ml, which corresponds to an estimated blood loss of 507 mL. Mean delta of hematocrit and hemoglobin were 1.4% and 0.71 g/dL, respectively. In univariate analysis, prostate volume, weight of resected tissue, preoperative red cells volume, and resection time were significantly and directly associated with loss of red cells volume (P = 0.038, P = 0.004, P = 0.002, and P = 0.039, respectively). Bipolar and monopolar TURP did not lead to significant difference of red cells loss. In multivariate analysis, both preoperative red cells volume and weight of resected tissue were independent predictors of red cells loss (P = 0.017 and P = 0.048 respectively).

Conclusion:

We present the first study to measure blood loss secondary to TURP using the 51Cr method. This technique allowed evaluating blood loss not only during the surgical procedure but also during the postoperative period. We learned from this study that, on average, blood loss from the procedure until postoperative day 3 was more than 500 mL, which is larger than previously reported amounts as measured by other methods. Because significant blood loss might occur during the postoperative period, the 51Cr method should be used to measure blood loss when evaluating new emerging techniques to manage BPH.

Introduction

T ransurethral resection of the prostate (TURP) is the standard method to relieve bladder outlet obstruction in patients with benign prostatic hyperplasia (BPH).¹ Perioperative and postoperative bleeding during TURP is significant, and may necessitate blood transfusion. In a review of 29 studies that were published between 1986 and 1998, the mean transfusion rate was 8.6%.¹ In a recently published study that included 10,654 men who underwent TURP, the transfusion rate was 2.9%.²

Blood loss related to TURP occurs during the operative procedure as well as during the postoperative period until cessation of hematuria. Various indicators may be used to determine blood loss, such as photometry of blood concentration in irrigating fluid, or, more commonly, measurement of hemoglobin and hematocrit in venous blood before and after the procedure. Blood volume consists of the part occupied by red blood cells and that occupied by plasma Therefore, hemoglobin and hematocrit might be influenced by plasma volume. The measurement of direct red cell mass is a better indicator of the body's red cell content.

New techniques are emerging to decrease blood loss during BPH surgery, such as laser resection or vaporization. Therefore, an accurate way to measure blood loss is needed to determine whether these techniques offer an advantage over TURP.

Radioisotope chromium 51 (51Cr) labeling is a very accurate method to measure the total volume of erythrocytic, or “red cell mass,” independently of the venous hematocrit.³ This isotopic dilution technique is widely used for the diagnosis of polycythemia vera, but, to our knowledge, was never used to determine blood loss during TURP. Our aim was to evaluate blood loss during TURP and its predictive factors, using the 51 Cr-labeling method.

Patients and Methods

The study was designed by the Committee for Lower Urinary Tract Symptoms of the French Association of Urology. From January to June 2008, 41 patients who underwent TURP for symptomatic BPH at four French urology centers were included in the analysis. The exclusion criteria included previous invasive procedures on the prostate, treatment with finasteride, malignancy, oral anticoagulation, and coagulation disorders. All patients provided an informed written consent. The study was approved by the ethics committees of the four centers enrolled in the study. General or spinal anesthesia was used.

Resections were conducted using monopolar or bipolar systems by senior surgeons. Recorded data included age of the patient, preoperative prostate volume as assessed by transrectal ultrasonography, maximum flow rate, International Prostate Symptom Score (IPSS), quality-of-life score as assessed by question 8 of IPSS, resection time, and weight of resected tissue. Serum sodium level, venous hematocrit, venous hemoglobin value, and red cells volume were assessed on the day before surgery and on the third day after surgery.

Red cells volume was measured by the 51 Cr-labeling method.³ This method has been widely published and almost universally used in the United States and Western Europe, and therefore, will not be described in detail. On the third day, a second red cells labeling was performed. At the same time, residual radioactivity of the first labeling was calculated and subtracted from the second radioactive measurement. Overall blood loss was estimated by multiplication of red cells volume loss and preoperative venous hematocrit. Delta red cells volume, hematocrit, and hemoglobin were the difference of the preoperative value and the one on postoperative day 3.

Statistical analysis was performed using SPSS 17.0 software (SPSS, Inc, Chicago, IL). To compare quantitative data between two groups, a Student t test was performed. A paired t test was used to compare variables measured both preoperatively and postoperatively. For binary variables, a Fisher exact test was performed. Multivariable analyses were performed using logistic regression.

Results

Characteristics of the 41 patients are presented in Table 1. Mean preoperative red cells volume was 1997 mL (standard deviation 408, range 1190–3002). Mean loss of red cells volume (delta red cells volume) as assessed by the 51Cr method was 209 mL, which corresponds to an estimated blood loss of 507 mL (Table 2). Loss of red cells volume was <200 mL and ≥200 mL in 22 and 19 patients, respectively. Mean delta of hematocrit and hemoglobin were 1.4% and 0.71 g/dL, respectively (Table 2). In univariate analysis, prostate volume, weight of resected tissue, preoperative red cells volume, and resection time were significantly associated with loss of red cells volume (P = 0.038, P = 0.004, P = 0.002, and P = 0.039, respectively, Table 1). Preoperative hemoglobin and hematocrit values were not significantly associated with red cells loss. In multivariate analysis including the four variables tha were significantly associated with loss of red cells volume in univariate analysis, both preoperative red cells volume and weight of resected tissue were independent predictors of red cells volume loss (P = 0.017 and P = 0.048 respectively, Table 1). Loss of red cells volume was also calculated per gram of resected tissue and per minute of resection (Table 2).

Table 1.

Preoperative and Operative Parameters and Association with Red Cells Loss

	Total N = 41	Delta RCV ≥200 mL	Delta RCV <200 mL	P univariate	P multivariate
Age (y)	69.8 ± 7.3	69.4 ± 7.6	70.1 ± 7.2	0.78
Prostate volume (cc)	43.7 ± 11.6	47.7 ± 10.8	40.2 ± 11.4	0.038	0.65
Q-max (mL/s)	8.9 ± 3.1	9.2 ± 2.8	8.6 ± 3.4	0.60
IPSS score	20.8 ± 5.0	21.1 ± 3.9	20.6 ± 6.0	0.76
QoL score	4.8 ± 0.9	4.9 ± 1.0	4.7 ± 0.8	0.55
Hematocrit (%)	41.2 ± 4.4	40.5 ± 4.6	41.8 ± 4.4	0.51
Hemoglobin (g/dL)	14.3 ± 12.9	14.3 ± 10.2	14.3 ± 15.1	0.89
Serum sodium (mmol/L)	140.4 ± 2.4	140.6 ± 1.7	140.1 ± 2.8	0.54
Preoperative RCV (mL)	1997 ± 408	2200 ± 408	1822 ± 324	0.002	0.017
Resection time (min)	31.4 ± 13.4	36.1 ± 14.4	27.5 ± 11.4	0.039	0.24
Resected prostate tissue (g)	14.7 ± 7.1	18.0 ± 7.2	11.9 ± 5.7	0.004	0.048

Mean ± standard deviation.

RCV = red cells volume; Q-max = maximal urinary flow; IPSS = International Prostate Symptom Score; QoL = quality of life.

Table 2.

Estimated Blood Loss by Various Parameters

Parameter	Mean ± SD	Min; Max
Estimated blood loss^a (mL)	507	−820; 2619
Delta RCV (mL)	209 ± 303	−402; 1100
Delta_hematocrit (%)	1.4 ± 3.0	−4.0; 6.0
Delta_hemoglobin (g/dL)	0.71 ± 1.16	−0.8; 4.6
Delta_RCV/g of resected tissue	12.0 ± 22.4	−55;76.1
Delta_RCV/minute of resection	6.3 ± 9.4	−13.4; 24.4

delta RCV × preoperative hematocrit.

SD = standard deviation; RCV = red cells volume.

Twenty-one and 20 patients underwent bipolar and monopolar TURP, respectively. Comparing those two groups, no significant differences were found in terms of red cells loss (Table 3).

Table 3.

Red Cells Loss in Bipolar and Monopolar Transurethral Resection of the Prostate

	Type of TURP	N	Mean ± SD	P
Delta RCV	Bipolar	21	205 ± 300	0.9
	Monopolar	20	212 ± 314
Delta RCV/g	Bipolar	21	13.0 ± 17.0	0.78
	Monopolar	20	11.0 ± 27.4
Delta RCV/min	Bipolar	21	7,0 ± 10.4	0.60
	Monopolar	20	5.5 ± 8.5

SD = standard deviation; RCV = red cells volume.

Discussion

To our knowledge, this study is the first one to assess blood loss during TURP using a 51Cr method. Thanks to the 51Cr method, overall blood loss from the day before surgery until the third day after TURP was estimated. Mean red cells loss was 209 mL, corresponding to an estimated blood loss of 509 mL.

These values are much higher than those reported in other studies. Sandfeldt and associates⁴ analyzed the effect of 3 months of finasteride on blood loss during TURP. The fluid of irrigation during TURP was collected in heparinized buckets. The hemoglobin concentration in each collecting bucket was measured by Hemocue Low Hemoglobin system (Hemocue AB, Angelholm, Sweden). The total blood loss was obtained as the sum of the hemoglobin content in all buckets used divided by the preoperative blood hemoglobin concentration. Blood loss as estimated by this method was 257 mL and 268 mL in patients receiving finasteride vs placebo. In their analysis, mean weight of resected tissue was 20 g and 17.5 g in finasteride and placebo groups, respectively, which was higher than in our study (mean weight 14.7 g).

Ekengren and colleagues⁵ measured blood loss during TURP in 700 patients. They also used a portable Hemocue photometer, and the absorption of irrigating fluid was assessed by the ethanol method. The blood loss ranged between 10 and 3825 mL, with a median of 300 mL.

Contrary to the techniques of others assessing blood loss, the 51Cr method took into account blood loss not only during the procedure and the short postoperative period, but also during 3 days after the procedure. We identified that significant blood loss might occur after the procedure. Therefore, this method should be used to evaluate new emerging techniques, such as laser and bipolar vaporization, which are said to offer better hemostasis than TURP.^6

–11 Compared with the Hemocue method, however, the 51Cr method to assess blood loss is more expensive and time consuming; hence, the estimated cost of our method to measure blood loss was 112 euros (about $138).

In a certain number of cases, red cells volume was higher on postoperative day 3 than on the day before surgery. One explanation is that the spleen serves as a reservoir for red blood cells.¹² Red cells trapped in the spleen might be mobilized by contraction of the spleen. Spleen contraction is induced by sport, hypoxia, bleeding, or decrease in blood pressure.¹³ Therefore, bleeding during TURP might induce splenic contractions, leading to mobilization of red cells. This mechanism might interfere with the red cells count in the way of underestimating blood loss resulting from TURP. Another hypothesis is that bone narrow regenerates red cells rapidly from the immediate postoperative period until the second red cell mass measure. Actually, this second mechanism might not interfere because red cells regeneration is known to take at least 5 days from initial blood loss.¹⁴

No significant association was found between blood loss and the type of TURP—monopolar or bipolar. A similar conclusion was reached in a randomized study that compared both techniques.¹⁵ For example, in the Ho and coworkers¹⁶ study, 100 patients were randomized to be treated by monopolar or bipolar TURP. No statistical difference was found in the decline in postoperative hemoglobin level between the two groups.

We found the weight of resected tissue and resection time to be associated with blood loss. These findings were described previously by other authors. In the study by Ekengren and associates,⁵ the predictive factors of blood loss were weight of resected tissue and operative time. They also found general anesthesia and malignant tissue to be associated with a smaller blood loss. Kirollos and colleagues¹⁷ investigated factors that influenced blood loss in TURP. In their series, the weight of resected tissue was the most important factor in determining blood loss. For the same authors, regional anesthesia was associated with less blood loss than general anesthesia, and the histologic nature of the prostate did not influence blood loss. For Sandfeldt and coworkers,⁴ 3 months of treatment with finasteride before TURP was associated with lower blood loss only in the group of patients with resected weight higher than 18.6 g.

In our study, preoperative red cells volume was found to be an independent predictor of blood loss during TURP. It means that patients with lower initial red cells volume tended to have lower red cell loss after TURP. To our knowledge, this finding was not previously described. One explanation could be that, for patients with higher preoperative red cells volume, the red cells reservoir contained in the spleen was not used, and therefore remained in the spleen. Therefore, blood loss could appear as being higher in this group. This hypothesis needs confirmation.

Conclusions

We presented the first measure of blood loss secondary to TURP using the 51Cr method. This technique allowed the evaluation of blood loss not only during the surgical procedure but also during the postoperative period. We learned from this study that, on average, blood loss from the procedure until postoperative day 3 was more than 500 mL, which is much more than previously reported amounts as measured by other methods. Two independent predictors of red cells loss were identified, including weight of resected tissue and preoperative red cells volume. Because significant blood loss might occur during the postoperative period, the 51Cr method should be used to measure blood loss when evaluating new emerging techniques.

Footnotes

Disclosure Statement

No competing financial interests exist.

Abbreviations Used

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