Fluid absorption and the ethanol monitoring method

Fluid absorption is a well-known complication of endoscopic surgeries, such as transurethral prostatic resection and transcervical endometrial resection. Absorption of electrolyte-free fluid in excess of 1 L, which occurs in 5% to 10% of the operations, markedly increases the risk of adverse effects from the cardiovascular and neurological systems. Absorption of isotonic saline, which is used with the new bipolar resection technique, will change the scenario of adverse effects in a yet unknown way. Hyponatremia no longer occurs, but marking the saline with ethanol reveals that fluid absorption occurs just as much as with monopolar prostate resections.

Ethanol monitoring is a method for non-invasive indication and quantification of fluid absorption that has been well evaluated. By using an irrigating fluid that contains 1% of ethanol, updated information about fluid absorption can be obtained at any time perioperatively by letting the patient breathe into a hand-held alcolmeter.

Regression equations and nomograms with variable complexity are available for estimating how much fluid has been absorbed, both when the alcolmeter is calibrated to show the blood ethanol level and when it is calibrated to show the breath ethanol concentration. Examples of how such estimations should be performed are given in this review article.

The difficulty is that the anesthesiologist must be aware of how the alcolmeter is calibrated (for blood or breath) and be able to distinguish between the intravascular and extravascular absorption routes, which give rise to different patterns and levels of breath ethanol concentrations.