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Keywords:

  • transurethral electrovaporisation of prostate;
  • intra-operative monitoring;
  • prostate surgery;
  • prostatic hyperplasia;
  • minimally invasive;
  • intra-operative complications

Abstract

  1. Top of page
  2. Abstract
  3. Introduction
  4. Patients and Methods
  5. Results
  6. Discussion
  7. Acknowledgements
  8. Conflict of Interest
  9. References

Objectives

  • To investigate if absorption of irrigation fluid occurs during bipolar plasma vaporisation (BPV) of the prostate.
  • To examine the clinical predictors of increased risk of fluid absorption and to assess if changes in serum electrolytes, venous pH, haemoglobin or haematocrit are able to detect intra-operative fluid absorption.

Patients and Methods

  • Over a 15-month period, 55 consecutive patients undergoing BPV of the prostate were investigated.
  • The volume of intra-operative fluid absorption was measured using expired-breath ethanol measurements.
  • Intra-operative irrigation was performed with isotonic saline containing 1% ethanol. The breath ethanol concentration was measured every 10 min during the operation and the volume of irrigation fluid absorption was calculated from these concentrations.
  • Data on clinical (age, prostate volume, smoking status) and surgical variables (operation time, irrigation volume, appearance of capsular perforation) as well as intra-operative changes in serum electrolytes, venous pH, haemoglobin and haematocrit were recorded.

Results

  • The median (range) age of the patients was 67 (48–87) years and the median (range) prostate volume was 41 (17–111) mL.
  • Nine patients (16%) showed a positive ethanol breath test during the procedure. The median (range) calculated fluid absorption in these patients was 346 (138–2166) mL.
  • Three patients had a fluid absorption >500 mL. One patient with absorption of >2 L showed clinical symptoms (dyspnoea and agitation) during the operation under spinal anaesthesia.
  • In the group of patients with fluid absorption, capsular perforation or injury to larger vessels was more often detectable.
  • In the group of patients with fluid absorption, only venous pH showed a significant change during the operation (from median 7.41 to median 7.34, P = 0.02). The pH decrease was significantly greater in the fluid absorption group than in the group of patients without fluid absorption (0.09 vs. 0.02, P = 0.005).

Conclusion

  • We have demonstrated that significant intra-operative fluid absorption can occur during BPV of the prostate. Care must be taken if using this procedure in patients with significant cardiovascular comorbidities.
  • Respecting the anatomical borders of the prostate seems to play a relevant role in preventing fluid absorption during the procedure.
  • Venous pH could be used to detect potentially dangerous fluid absorption if intra-operative monitoring with breath ethanol measurements is not available.

Abbreviations
BPV

bipolar plasma vaporisation

TUR

transurethral resection

QoL

quality-of-life

ASA

American Society of Anaesthesiology

Introduction

  1. Top of page
  2. Abstract
  3. Introduction
  4. Patients and Methods
  5. Results
  6. Discussion
  7. Acknowledgements
  8. Conflict of Interest
  9. References

Bipolar plasma vaporisation (BPV) is a viable alternative to conventional TURP with evidence of low intra- and peri-operative morbidity and superior functional short-term results [1-3]. BPV combines the advantages of tissue vaporisation (reduced bleeding, excellent overview and short learning curve) with those of the bipolar resection technique (effective coagulation, saline irrigation and affordable equipment). Therefore, it is an appealing treatment option for high-risk patients with cardiovascular comorbidities, or those on anticoagulation or antiplatelet medication.

Major bleeding and transurethral resection (TUR) syndrome are the most dangerous complications of conventional TURP [4-6] and are particularly harmful in patients in the high risk group. Several novel techniques (e.g. bipolar TURP, green-light and holmium laser treatment) have been shown to be safe and efficacious and now play an increasing role in the treatment of these patients [7-10]. The main advantage of these techniques is improved haemostasis, which minimises bleeding complications and is also thought to prevent intra-operative influx of irrigation solution into the vascular system [11]. Furthermore, isotonic saline instead of electrolyte-free solutions can be used for intra-operative irrigation so that the development of classic TUR syndrome is not possible.

The green-light laser procedure has been shown to be the most appropriate technique for patients in the high-risk group [12]. The procedure can safely be performed with ongoing antiplatelet or anticoagulation medication [13]. Furthermore, it has been shown that intra-operative fluid absorption does not occur during green-light laser vaporisation of the prostate [14].

The BPV technique shares several properties with the green-light laser technique (e.g. vaporisation and saline irrigation) but by using a conventional bipolar generator, is cost-efficient and more widely available. In high-risk patients with cardiovascular morbidity, excessive absorption of fluid, even isotonic fluid, can potentially be dangerous. Theoretically, as BPV works similarly to the green-light laser using a vaporisation technique, intra-operative fluid absorption should be minimal, but this has yet to be formally evaluated. The primary aim of the present study was to investigate if intra-operative fluid absorption occurs during BPV of the prostate.

Patients and Methods

  1. Top of page
  2. Abstract
  3. Introduction
  4. Patients and Methods
  5. Results
  6. Discussion
  7. Acknowledgements
  8. Conflict of Interest
  9. References

Consecutive patients undergoing BPV for prostatic BOO were prospectively enrolled from a single academic institution between July 2010 and October 2011. Patients were excluded if they had former alcoholic or chronic liver disease because an ethanol solution was used for intra-operative irrigation. The local ethics committee approved the study protocol and all enrolled patients provided written informed consent.

The attending urologist reviewed the referred patients and conducted the clinical assessment. Uroflowmetry was performed and post-void residual urine volume was measured during abdominal ultrasonography. Patients were asked to complete the IPSS and a quality-of-life (QoL) questionnaire. Uroflowmetry, post-void residual urine volume, IPSS and QoL were not recorded in patients with an in-dwelling urinary catheter. Medical comorbidities and medications were recorded. Preoperative blood tests included serum electrolytes and creatinine, coagulation variables, complete blood count and serum PSA concentration. Additionally, urine analysis and urine culture were performed.

The operations were performed under either general anaesthesia with endotracheal intubation or spinal anaesthesia. According to the institutional guidelines, i.v. trimethoprim-sulfametoxazole 160/800 mg single-shot antibiotic prophylaxis was administered 30–60 min before the operation.

A SurgMaster UES-40-Generator and the hemispherical HF-vaporisation electrode (both Olympus Winter & Ibe GmbH, Hamburg, Germany) were used for the operation. The electrode was introduced through a 25-F OES continuous-flow Iglesias resectoscope (Olympus) coupled to an automated irrigation–suction pump system (Endo Fluid Management System Urology, Future Medical Systems, Genève, Switzerland).

Four different surgeons (three urologists, each having performed >200 previous transurethral prostate operations) and one resident (who had performed 50 previous procedures) performed the operations. BPV was carried out similarly to a conventional TURP. After identification of the ureteric orifices, vaporisation was initiated posteriorly at the bladder neck. After vaporisation of the median lobe, the procedure was continued at the lateral lobes. Vaporisation was completed anteriorly and in the region of the verumontanum to give the appearance of a TURP-like cavity. If the total prostate volume was <30 mL, a bladder neck incision was performed at the end the procedure. After the operation, a 20-F three-way irrigation catheter was inserted and isotonic saline was used for continuous irrigation.

The expired-breath ethanol technique is an established method of investigating intra-operative absorption of irrigation fluid [15]. The university hospital pharmacy added 1% ethanol to conventional isotonic 0.9% saline (Dr. G. Bichsel AG, Interlaken, Switzerland) for use as intra-operative irrigation. The end-expiratory ethanol concentrations were measured at the beginning of the operation and at regular 10-min intervals throughout the procedure using an electrochemical AlcoQuant 6020 alcometer (EnviteC GmbH, Wismar, Germany). The values obtained represented the corresponding blood ethanol concentrations in mg/mL. A blood ethanol concentration of 0.05 mg/mL corresponds to ∼150 mL fluid absorption. If patients were under general anaesthesia, the alcometer was directly connected to the endotracheal tube and the passively expired air was used for the measurements. Patients were asked to expire directly into the alcometer whilst under spinal anaesthesia.

Changes in serum biochemical and haematological variables, such as electrolyte concentrations (sodium, potassium, chloride), venous pH, haemoglobin and haematocrit were monitored to investigate if they were affected by intra-operative fluid absorption. These were measured at the beginning of the operation, after 30 min and at the end of the procedure. The most pronounced change from the initial value was used for the statistical analyses.

The nomogram of Hahn was used intra-operatively to estimate the absorption volume of irrigation fluid during the procedure [15]. The surgeons were blinded to the results of the ethanol measurements but were informed if the critical absorption volume of 2 L was exceeded. After the operation, the surgeons recorded if a relevant intra-operative event (capsular perforation, injury to prostatic sinuses or deep bladder neck incision) occurred during the procedure. The total operation time (from the insertion of the cystoscope until the insertion of the catheter), the total irrigation volume and the type and volume of all administered i.v. fluids were recorded. Postoperatively, the more precise Hahn mathematical formula was used for the final quantification of the total absorption volume [16].

The statistical analyses were performed using IBM SPSS Statistics 20.0 (SPSS Inc., Chicago, IL, USA). The Wilcoxon signed-rank test was used to compare the values of the investigated blood tests at the beginning of the operation with those throughout the procedure. The Mann–Whitney U-test was used to compare the changes in these blood tests between the groups of patients with and without a positive breath test. A P value <0.05 was considered to indicate statistical significance.

Results

  1. Top of page
  2. Abstract
  3. Introduction
  4. Patients and Methods
  5. Results
  6. Discussion
  7. Acknowledgements
  8. Conflict of Interest
  9. References

A total of 55 patients were enrolled in this study. Table 1 shows their baseline characteristics. The median (range) age of the patients was 67 (48–87) years and the median (range) prostate volume was 41 (17–111) mL. In 18 patients (33%) BPV was performed with ongoing acetylsalicylic acid medication. None of the patients were on clopidrogel or coumarin medication. Forty-two patients (76%) were operated on under general anaesthesia and 13 patients (24%) had spinal anaesthesia. All operations were successfully performed as pure BPV and no significant intra-operative complications occurred. The median (range) irrigation volume used was 21 (12–39) L and the median (range) operation time was 70 (30–140) min.

Table 1. Baseline characteristics of all 55 patients
  1. Qmax, maximum urinary flow rate; PVR, post-void residual urine volume; IPSS,   .

No. of patients55
Median (range) age, years67 (48–87)
Median (range) prostate volume, mL41 (17–111)
Median (range) PSA, ng/mL2.57 (0.39–13.7)
BPH/prostate carcinoma, n (%)55 (100)/0 (0)
In-dwelling catheter, n (%)11 (20)
Acetylsalicylic acid medication, n (%)18 (33)
Anticoagulation medication, n (%)0 (0)
ASA score, n (%) 
15 (9)
230 (55)
320 (36)
Median (range) IPSS/QoL16 (5–35)/4 (0–6)
Median (range) Qmax, mL/s10 (3–29)
Median (range) PVR, mL98 (0–1000)

Nine of the 55 patients (16%) showed a positive ethanol breath test. In these nine patients, the measured blood ethanol values ranged from 0.04 to 0.49 mg/mL. The median (range) calculated fluid absorption for these patients was 346 (138–2166) mL. Three patients absorbed >500 mL of irrigation solution (Fig. 1). The patient who absorbed 2166 mL developed dyspnoea and agitation. This 50-year-old patient, who had no other comorbidities (American Society of Anesthesiology [ASA] score of 1), was operated on under spinal anaesthesia. His prostate volume was 53 mL. Preoperatively he had an in-dwelling catheter for urinary retention but a negative urine culture. The total operation time was 100 min and, intra-operatively, the surgeon noticed moderate diffuse bleeding but no obvious capsular perforation or opened venous sinus. A bladder lithotripsy, which was planned for concomitant bladder stones at the end of the procedure, was abandoned owing to the high and symptomatic fluid absorption. Postoperatively, the patient was symptom-free and lithotripsy was successfully performed 4 days later. No other patients developed clinical symptoms during or after the procedure and none of the operations had to be aborted owing to high blood ethanol values or high fluid absorption.

figure

Figure 1. The calculated amount of fluid absorption in the nine patients with a positive breath test.

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Figure 2 shows the temporal appearance of the positive breath ethanol tests and their duration during the procedure for each patient with positive breath test. In the majority of cases, fluid absorption was detected in the latter part of the operation.

figure

Figure 2. Temporal appearance and duration of a positive ethanol breath test in the nine patients with a positive breath test. Fluid absorption was detected in the latter part of the operation in the majority of patients.

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In five of the nine patients (56%) with fluid absorption, intraoperative events were reported as follows: capsular perforation (n = 1), injury to larger sinuses (n = 1) and deep bladder neck incision (n = 3). In the group of patients without fluid absorption, for 10 patients (22%) a relevant intra-operative event was reported. These were capsular perforation (n = 2) and a deep bladder neck incision (n = 8).

Table 2 shows the differences between the patient groups with and without a positive ethanol breath test. Besides the differences in the rate of intra-operative events, the group of patients with fluid absorption more often had an in-dwelling catheter, inhibitors of platelet aggregation or a higher ASA score. Furthermore, they were more often operated on under general anaesthesia. There were no obvious differences in the smoking status, the rate of UTIs, the operation time, the type and volume of administered i.v. fluids or the experience of the surgeons between the two groups.

Table 2. Differences between patients with (absorber group) and without (non-absorber group) a positive ethanol breath test
 Absorber groupNon-absorber group
  1. INR, International Normalised Ratio value. *Defined as intra-operative capsular perforation, injury to larger sinuses or deep bladder neck incision.

No. of patients, n (%)9 (16)46 (84)
Median (range) age, years65 (50–81)67 (48–87)
Median (range) prostate volume, mL37 (22–63)42 (17–111)
Indwelling catheter, n (%)3 (33)8 (17)
Acetylsalicylic acid medication, n (%)4 (44)14 (30)
Median (range) INR1 (0.8–1.4)1.05 (0.9–1.3)
ASA score, n (%)  
11 (11)4 (9)
23 (33)27 (59)
35 (56)15 (32)
Smokers, n (%)1 (11)9 (20)
Positive urine microbiology, n (%)3 (33)17 (36)
Anaesthesia, n (%)  
Intubation8 (89)34 (74)
Spinal1 (11)12 (26)
Median (range) operation time, min80 (45–110)70 (30–140)
Median (range) irrigation volume, L26 (12–33)21 (12–39)
I.v. fluids  
Median (range) volume of fluids administered, mL1100 (400–1900)1025 (300–1900)
Type of fluids administered, %  
Ringer's solution7877
Sodium chloride (0.9%)1919
Others34
Intra-operative events*, n (%)5 (55)10 (22)

Figure 3 shows that for all serum biochemical and haematological variables investigated, increases and decreases were seen. In patients with a positive breath test, venous pH was the only blood test that showed a significant intra-operative change (from median [range] 7.41 [7.34–7.46] to 7.34 [7.31–7.35]; P = 0.02). Severe metabolic acidosis was not detectable in any of the patients. All other investigated variables did not change significantly in the group of patients with a positive breath test (data not shown). A comparison between patients with and without fluid absorption is shown in Table 3. The only significant difference between the two groups was in venous pH, with the fluid absorption group showing a larger decrease (−0.09 vs −0.02, P = 0.005). The sensitivity of a pH decrease to detect fluid absorption was 88%, whereas its specificity was only 32%.

figure

Figure 3. Percentage of patients with a decrease, increase or no change in the respective blood tests in the groups of patients with (absorber group) and without fluid absorption (non-absorber group). In the absorber group, none of the values showed a decrease or increase exclusively. Furthermore, no clear difference was detectable for any of the variables between the absorber and the non-absorber group.

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Table 3. Comparison of intra-operative changes in the investigated blood variables between patients with (absorber group) and without (non-absorber group) a positive ethanol breath test
 Absorber group, median (range)Non-absorber group, median (range)P
  1. *Indicates a significant difference between the two groups (Mann-Whitney U-test).

Sodium, mmol/L0 (−6–2)0 (−5–10)0.63
Potassium, mmol/L0.2 (−0.7–0.3)0.1 (−1.9–1.4)0.85
Chloride, mmol/L0 (−3–7)1 (−9–8)0.46
Venous pH−0.09 (−0.14–0.01)−0.02 (−0.16–0.07)0.005*
Haemoglobin, g/dL−0.7 (−2.7–2.3)−0.6 (−4.9–2.2)1.0
Haematocrit, %−2.2 (−8–7.7)−1.4 (−12.3–6.4)0.95

Venous pH remained the only blood variable with a significant change in the absorber group and a significant difference in its change between the two groups of patients, if the fluid absorption group was restricted to only patients with absorption of >500 mL (previously defined as significant fluid absorption [17]; data not shown).

Major postoperative complications did not occur in any of the 55 patients. No patients required re-operation for persistent haematuria or clot retention. Re-catheterisation after initial catheter removal was necessary in five patients (9%) owing to urinary retention (n = 4) or persistent bleeding (n = 1). The median (range) time to definitive catheter removal was 3 (2–13) days and the median (range) postoperative hospital stay 4 (2–8) days.

Discussion

  1. Top of page
  2. Abstract
  3. Introduction
  4. Patients and Methods
  5. Results
  6. Discussion
  7. Acknowledgements
  8. Conflict of Interest
  9. References

This prospective investigation showed that significant intra-operative absorption of irrigation fluid can occur during BPV of the prostate. The majority of patients had a negative ethanol breath test and in those with a positive test, most absorbed <500 mL. Three patients had fluid absorption >500 mL. In our single case where >2 L of saline was absorbed, there was no obvious intra-operative event such as capsular perforation and no postoperative sequelae; however, this patient was a healthy 50-year-old man and a similar large volume influx in patients with significant cardiac comorbidities could result in dangerous complications.

It has been shown that >30% of the patient population with LUTS have an ASA score of ≥3 and thus have significant comorbidities [6]. Conventional TURP is still associated with a considerable risk of major bleeding and TUR syndrome [6, 18], so these high-risk patients may benefit from minimally invasive alternatives such as BPV; however, to be considered a suitable treatment option for high-risk patients, the safety profile of a proposed alternative procedure needs to be evaluated properly. Green-light laser vaporisation, which has been shown to be safe and efficacious [7, 13, 14], is currently the most recommended technique to treat patients in the high-risk group [12]. The BPV technique, which shares several properties with the green-light laser technique, has been introduced as a widely available and cost-efficient alternative [3]. It can be performed with a conventional bipolar generator and lower-priced vaporisation electrodes compared with the cost-intensive laser fibres; however, our investigation shows that, in terms of intra-operative fluid absorption, BPV appears to be inferior to the green-light laser procedure during which Barber et al. [14] showed that fluid absorption does not occur.

In the present study, neither usage of a vaporisation technique, nor the use of an automatic low-pressure irrigation-suction pump in combination with an Iglesias resectoscope could prevent the absorption of irrigation solution. Low-pressure irrigation has been shown to reduce but not prevent fluid absorption during TURP [19, 20]. It has also been shown that capsular perforation and injury to larger vessels are risk factors for fluid absorption [21]. In the present investigation, 55% of the patients with fluid absorption had a perceived capsular perforation or injury to larger vessels. The fact that fluid absorption occurred only in the latter part of the operation also indicates that fluid absorption mainly occurs when the operation approaches the prostatic capsule. This has previously also been shown for conventional TURP [22]; however, it is important to know that significant fluid absorption can also occur without obvious injury to the capsule or larger vessels. Whilst smoking and an extended and prolonged resection have furthermore been identified to be associated with a higher risk of intra-operative fluid absorption during TURP [22, 23], this was not shown in our investigation.

Absorption of isotonic saline during bipolar transurethral procedures does not result in classic TUR syndrome, which is caused by a combination of absorption of excess hypotonic fluid volume and toxicity of solutes in the solution used (e.g. glycine). Classic TUR syndrome is characterised by visual disturbances, renal failure, with life-threatening cardiopulmonary failure as well as neurological symptoms caused by cerebral oedema [4]. Neurological symptoms are unlikely to occur if isotonic saline is absorbed during bipolar transurethral surgery, but saline absorption results in a greater plasma expansion and so can lead to a more pronounced acute volume overload [24]. Initial symptoms include skin swelling and dyspnoea. Pulmonary oedema and cardiovascular de-compensation can develop if larger amounts of saline are absorbed. It has been shown that the severity of symptoms also depends on the medical condition of the respective patients, with less pronounced symptoms in young and healthy patients [4]. This might explain the mild symptoms of the patient with >2 L fluid absorption in the present investigation.

Hyponatraemia as an indicator of fluid absorption is only of use when hypo-osmolar irrigation solutions are used, such as during conventional TURP. Also, as the body's homeostatic mechanisms adjust to compensate for electrolyte changes caused by fluid absorption, serum sodium concentrations need to be measured repeatedly during the procedure if it is to be used reliably [4]. As expected, in our investigation hyponatraemia was not detectable as isotonic fluid was used. Additionally, intra-operative changes in potassium, haemoglobin and haematocrit were not helpful to detect fluid absorption. It has been reported that saline absorption results in a hyperchloraemic acidosis owing to its high concentration of chloride [25] and hence hyperchloraemia and acidosis are potential indicators of excessive saline absorption [26]. We did not find chloride concentration to be a reliable variable in detecting fluid absorption because changes in serum chloride concentration were seen equally in the non-absorber group. By contrast, venous pH showed both a significant decrease in the absorber group and a significant difference between the absorber and the non-absorber group. The pH decrease had good sensitivity to detect fluid absorption but specificity was low and hence a minimal change in pH is not clinically helpful.

We did not find a significant difference in the type and amount of administered i.v. fluids between our two groups, but it is important to note that i.v. saline or other solutions, particularly if given in large volume during the procedure, can confound the investigated blood variables; therefore, these variables are not very reliable for monitoring fluid absorption during transurethral surgery. In comparison, the measurement of intra-operative breath ethanol is not affected by i.v. fluids, and is a sensitive, non-invasive and relatively easy-to-perform technique for the early detection of fluid absorption and therefore allows a timely initiation of adequate treatment and postoperative care [4, 15].

Some limitations of the present investigation deserve mention. The study was powered to investigate fluid absorption, but not to perform detailed analyses for the assessment of risk factors of fluid absorption. Accordingly, a statistical analysis was not performed for this aspect. We were able to show that a pH decrease in general has a low specificity for the detection of fluid absorption; however, the pH decrease was more pronounced in the group of patients with fluid absorption. This indicates that the specificity could be improved by defining a threshold value below which fluid absorption is most likely. The definition of a reliable threshold value was not possible owing to our relatively small sample size. Similarly, our study was underpowered to analyse clinical risk factors to predict fluid absorption. A larger prospective investigation would be required to identify formally the potential risk factors and clinical predictors of fluid absorption during BPV and our results could be helpful in designing this.

In conclusion, we have demonstrated that significant intra-operative fluid absorption can occur during BPV of the prostate. Care must be taken if using this procedure in patients with significant cardiovascular comorbidities. Respecting the anatomical borders of the prostate seems to play a relevant role in preventing fluid absorption during the procedure. Venous pH could be used with good sensitivity but a low specificity to detect potentially dangerous fluid absorption if intra-operative monitoring with breath ethanol measurements was not available.

Acknowledgements

  1. Top of page
  2. Abstract
  3. Introduction
  4. Patients and Methods
  5. Results
  6. Discussion
  7. Acknowledgements
  8. Conflict of Interest
  9. References

The authors thank Prof. Robert G. Hahn for his assistance in the calculations of fluid absorption and Alexandra Veloudios for the organisation of the patient care during the study.

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  2. Abstract
  3. Introduction
  4. Patients and Methods
  5. Results
  6. Discussion
  7. Acknowledgements
  8. Conflict of Interest
  9. References
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