a 34-year - old woman ( height , 162 cm ; weight , 53 kg ) with menorrhagia was admitted for elective hysteroscopic myomectomy of a 4.7  4.5 cm submucosal benign fibroid adenoma . three years before , she had undergone a large loop excision of the transformation zone of the uterine cervix due to carcinoma in situ . she was premedicated with intramuscular injection of midazolam 2 mg and glycopyrrolate 0.2 mg . upon arrival at the operating room vital signs were blood pressure 121/70 mmhg , heart rate 56 beats / min and pulse - oxymetry revealed 99% of spo2 before anesthetic induction . anesthesia was induced with 1.5 mg / kg of propofol , and 1 g / kg of remifentanil , and tracheal intubation was facilitated with 0.8 mg / kg of rocuronium . the patient 's lungs were ventilated with a tidal volume of 7 - 9 ml / kg , i : e ratio of 1 : 1.9 at a respiratory rate of 8 - 12 breaths / min in 50% oxygen with medical air to maintain normocarbia throughout the procedure . anesthesia was maintained with continuous infusion of remifentanil ( 0.1 - 0.2 g / kg / min ) and sevoflurane ( 1.5 - 2.5% ) . after the induction of anesthesia , 0.9% normal saline was infused at a rate of 4 ml / kg / h . an esophageal temperature probe was monitored and the patient was kept warm using a forced - air warming system ( bair - hugger , augustine - medical , eden prairie , mn , usa ) at 36. after lithotomy positioning for surgical hysteroscopy , electrolyte - free 5 : 1 sorbitol / mannitol solution was used as a distending solution . the solution was infused using a high - pressure surgical irrigator ( irrigator ; biomedical dynamics , burnsville , minnesota , usa ) under pressures of 100 - 140 mmhg . the effluent distending solution was collected , and fluid balance was assessed continuously throughout the operation . at 40 minutes after the start of the procedure , 2 l of sorbitol / mannitol solution had been used , and effluent volume was not checked precisely due to a large amount of fluid leakage through the uterine cervix . during the procedure , the esophageal temperature gradually decreased from 36.5 to 33. at 50 minutes after the start of the procedure , spo2 as measured by pulse - oximetry abruptly declined to 85% , and end - tidal co2 ( etco2 ) decreased to 22 mmhg . we inserted a 20 g catheter to the left radial artery for continuous arterial pressure monitoring and blood sampling . the first arterial blood gas results were ph 7.264 , pao2 151.7 mmhg , paco2 31.7 mmhg , base excess -12.7 mmol / l , sao2 93.7% in fio2 1.0 ; other laboratory findings revealed sodium 83 mmol / l , potassium 3.4 mmol / l , chloride 62 mmol / l , hemoglobin 8.5 g / dl . the patient was immediately treated with 10 mg of furosemide and infused with 3% saline at a rate of 60 ml / hr . peep 5 cmh2o was applied , spo2 reached to 98 - 100% in fio2 1.0 . the total procedure time was about 150 minutes and total infused intravenous fluid was crystalloid 1,160 ml , packed rbc 1 pint , and the total urine output was 3,600 ml . at the end of the procedure , arterial blood gas analysis showed ph 7.287 , pao2 143.7 mmhg , paco2 29.5 mmhg , base excess -10.6 mmol / l , sao2 99.0% in fio2 0.5 ; other laboratory findings revealed sodium 92 mmol / l , potassium 4.7 mmol / l , chloride 63 mmol / l , hemoglobin 11.7 g / dl . afterwards , she was cared for in the postanesthetic care unit for 40 minutes and her urine output was 1,600 ml , with 20 mg furosemide . she was subsequently transferred to the intensive care unit ( icu ) with stopping infusion of 3% saline . the patient 's lungs were ventilated with synchronized intermittent mandatory ventilation , a tidal volume of 310 ml / kg , peep 8 cmh2o , pressure support 8 mmhg at a respiratory rate of 8 - 12 breaths / min in 40% oxygen . chest auscultation revealed diffuse coarse crepitations over the whole lung field and the chest x - ray revealed severe pulmonary edema ( fig . 1 ) . after admission to the icu , urine output was maintained with 8 - 10 ml / kg / hr with infusion of furosemide ( 10 mg / hr ) for 16 hours , and serum sodium levels were recovered to 108 mmol / l three hours later ( table 1 ) . brain computed tomography performed on the first postoperative day showed mild brain edema . at 15 hours after admission to the icu , her mental status was alert without neuralgic sequalae , her vital signs were stable , and the pulmonary edema had improved . she was weaned from mechanical ventilation . she was transferred to the general ward on the second postoperative day and discharged on the fourth postoperative day . the patient remained asymptomatic during six months of follow - up with no neurologic complications . hysteroscopic procedures have been increasingly used with several benefits when compared with traditional surgical procedures . despite their increasing use , the absorption of fluid distention media can still cause unpredictable complications such as volume overload , dilutional hyponatremia , water intoxication , and cerebral edema [ 1 - 3 ] . mmol / l for every liter of hypotonic fluid absorption . in a previous study of 101 patients who absorbed over 2 l of glycin solution during myoma resections , the patients did not develop volume overload , and their recovery was usually uneventful within 12 hours . however , absorption of less than 2 l of distention medium could cause death induced by hyponatremia ( 98 mmol / l ) and cerebral edema . in our case , the patient experienced extreme hyponatremia ( 83 mmol / l ) accompanied by metabolic acidosis due to absorption of the distention medium , resulting in pulmonary edema and brain swelling , with absorption of less than 2 l of distention fluid . hyponatremia is one of the most common electrolyte disturbances encountered by anesthesiologist , and sometimes it can lead to permanent or lethal complications . dilutional hyponatremia combined with water intoxication can cause fatal cerebral edema and lead to death . it is thought that the free water of distention medium readily traverses cellular membranes and the blood brain barrier , moving easily between the intravascular , extracellular , and intracellular spaces as an osmotic gap between areas equilibrating extra and intracellular osmolality . although extreme hyponatremia is associated with convulsions and coma , the classic central nerve system signs are mainly caused by the accompanying acute serum hypoosmolality . in our case , the patient 's mental status was fully recovered without neurologic complications about 17 hours after the development of severe hyponatremia . although we did not evaluate the value of measured serum osmolality in this patient , the sorbitol and mannitol in the distention medium , which are restricted to the extracellular fluids and draw water from the central compartment , may cause extremely reduced serum sodium levels while relatively maintaining the serum osmolality . the relatively maintained serum osmolality may be associated with the rapid recovery and lack of neuralgic sequalae in this patient . although the amount of distention fluid absorbed seems to be dependent on the duration of the procedure and the pressure of surgical irrigator , the absorption volume of distention medium measured by the surgical irrigator does not necessarily reflect changes in serum sodium and osmolality . therefore , the measurement , not calculation , of serum osmolality , may predict the clinical course . in previous cases , hypercarbia may induce peripheral arteriolar dilatation and lead to the increased absorption of fluid distention medium . however , in our case , moderate metabolic acidosis was observed with decreased serum bicarbonate concentration and this was resolved after correction of hyonatremia . however , the total amount of extracellular bicarbonate did not decrease with rapid volume expansion but simply decreased in concentration . in a previous animal study , with normal renal function , acute volume expansion caused increased renal bicarbonate wasting . bicarbonate reabsorption decreased due to increased sodium diuresis and decreased reabsorption of solute in the proximal tubule . therefore , patients with normal renal function may have potential for worsening dilutional acidosis with acute volume expansion . rapid correction of hyponatremia can also lead to neurologic disorder , so it was suggested that the correction not exceed 25 mmol / l in 48 hours . neurologic disorders such as extrapontine and pontine myelinolysis related with rapid correction have usually been known to develop in chronic hyponatremic patients . in our case , the serum sodium level was rapidly corrected with only 3% saline at a rate of 60 ml / hr for 140 minutes and a large amount of urine output . in the healthy system , osmoreceptors in the hypothalmus sense the diffusion of water into or out of receptor cells caused by changes in serum osmolality . in response , the hypothalamus directs the pituitary to increase or decrease the release of vasopressin from the posterior pituitary . in this case , although furosemide was used , fluid overload may have caused a decrease in vasopressin release , leading to dieresis and rapid recovery of serum sodium levels . a significantly lower amount of distention fluid was absorbed during hysteroscopy with general anesthesia rather than epidural anesthesia . however , general anesthesia could mask early signs of hyponatremia and water intoxication such as bradycardia , hypertension , headache , nausea , and mental status change . in our patient who had general anesthesia , therefore , especially in the cases where general anesthesia is used during hysteroscopy , intraoperative fluid balance should be maintained and the possibility of water intoxication should be considered when saturation and capnogram abruptly decrease . in conclusion , this case shows the risk of extreme hyponatremia with moderate metabolic acidosis caused by distention medium absorption during minimally invasive hysteroscopy . early detection and prompt management of massive absorption of fluid distention medium is important for patient recovery without neurologic complications .
excess absorption of fluid distention media remains an unpredictable complication of operative hysteroscopy and may lead to lethal conditions . 
 we report an extreme hyponatremia , caused by using an electrolyte - free 5 : 1 sorbitol / mannitol solution as distention / irrigation fluid for hysteroscopic myomectomy . a 34-year - old female developed severe pulmonary edema and extreme hyponatremia ( 83 mmol / l ) during transcervical endoscopic myomectomy . 
 a brain computed tomography showed mild brain swelling without pontine myelinolysis . 
 the patient almost fully recovered in two days . 
 meticulous attention should be paid to intraoperative massive absorption of fluid distention media , even during a simple hysteroscopic procedure .