Trapping of electrolytes during fluid absorption in transurethral resection of the prostate

Measurement of Procedure-Specific Irrigation-Fluid Absorption in Transurethral Therapy of Lower Urinary Tract Syndrome, Using Ethanolic Saline and Breath Alcometry

INTRODUCTION

Transurethral resection risks excessive absorption of irrigating fluid with potentially severe or life-threatening consequences. We determined the amount of absorbed saline irrigation fluid during photoselective vaporisation of the prostate (PVP) and bipolar transurethral resection of the prostate (bTURP).

PATIENTS AND METHODS

Patients at our institution treated by one of these methods were monitored by the alcometric method: ethanol is added to the irrigation fluid and blood alcohol is measured with a breathalyser. Various possible correlations were investigated.

RESULTS

Data from 71 patients (36 PVP, 35 bTURP) were analysed. Detection of any absorption was more frequent under bTURP (71% of patients) than under PVP (39%; p = 0.006). Absorption in the volume range 500-1,000 ml was conspicuously more frequent in the bTURP procedure than in PVP.

CONCLUSIONS

Presence of absorption was more frequent under bTURP than under PVP. However, high-volume absorption was more frequent during bTURP than in PVP.

Fluid volume kinetics of dilutional hyponatremia; a shock syndrome revisited

OBJECTIVE

To evaluate whether the pathophysiology of shock syndromes can be better understood by comparing central hemodynamics with kinetic data on fluid and electrolyte shifts.

METHODS

We studied the dilutional hyponatremic shock that developed in response to overhydration with electrolyte-free irrigating fluid - the so-called 'transurethral resection syndrome' - by comparing cardiac output, arterial pressures, and volume kinetic parameters in 17 pigs that were administered 150 ml/kg of either 1.5% glycine or 5% mannitol by intravenous infusion over 90 minutes.

RESULTS

Natriuresis appeared to be the key factor promoting hypovolemic hypotension 15-20 minutes after fluid administration ended. Excessive sodium excretion, due to osmotic diuresis caused by the irrigant solutes, was associated with high estimates of the elimination rate constant (k10) and low or negative estimates of the rate constant describing re-distribution of fluid to the plasma after translocation to the interstitium (k21). These characteristics indicated a high urinary flow rate and the development of peripheral edema at the expense of plasma volume and were correlated with reductions in cardiac output. The same general effects of natriuresis were observed for both irrigating solutions, although the volume of infused 1.5% glycine had a higher tendency to enter the intracellular fluid space.

CONCLUSION

Comparisons between hemodynamics and fluid turnover showed a likely sequence of events that led to hypovolemia despite intravenous administration of large amounts of fluid.

Natriuresis and “dilutional” hyponatremia after infusion of glycine 1.5%

STUDY OBJECTIVE

To challenge the view that the hyponatremia resulting from absorption of glycine 1.5% is attributed to the expansion of the extracellular fluid (ECF) volume, and that the change in serum sodium is therefore widely used to calculate the amount of irrigant absorbed.

DESIGN

Retrospective analysis of six studies.

SETTING

University-affiliated hospital.

MEASUREMENTS

Approximately 1.2 L of glycine 1.5% was infused in 23 volunteers (two studies), 1 L in 10 prostatectomy patients, 2.4 L in 6 sheep, 4 L in 6 other sheep, and 3 L in 9 piglets. The distribution of the irrigant water was estimated from the difference between the measured and the expected serum sodium levels, taking into account the urinary losses of sodium and water.

MAIN RESULTS

Between 30% and 50% of the irrigant volume had diffused into the cells 30 minutes after the infusion, and only between 0% and 50% of the fluid remained in the ECF. One hour later, natriuresis accounted for 100% of the residual hyponatremia in the small-volume experiments, and it accounted for approximately 50% in the large-volume experiments. The change in serum sodium could not be used to quantify the small infusion volumes, but the large ones could be quantified fairly accurately if assessed at the very end of the infusion.

CONCLUSIONS

Diffusion of water into the cells and natriuresis reduced and prolonged the hyponatremia associated with infusions of glycine 1.5%. This finding makes IV fluid with sodium added a more rational alternative than furosemide in the treatment of fluid overload with this irrigating solution.