Hysteroscopy: Managing and minimizing operative complications

Hyponatremia and hypoosmolality more likely in premenopausal women

These conditions may have catastrophic consequences if they are not recognized and corrected promptly. The brain swells as it attempts to become isoosmotic with the vascular system. If swelling exceeds 5%, the risk of severe neurological damage dramatically increases.

This is an important problem in premenopausal women, since estrogen and progesterone inhibit sodium-potassium adenosine triphosphatase (ATPase) activity in the brain. This sodium pump protects the brain against cerebral edema, which can cause herniation of the brain stem and death. Although men and postmenopausal women develop dilutional hyponatremia, they are less likely to suffer brain damage because the sodium pump is intact.

Taskin et al²⁰ conducted a randomized trial showing an increase in the sodium-potassium ATPase pump activity and decreased volume deficit during hysteroscopic surgery in patients pretreated with a GnRH agonist, compared with a control group. This increased pump activity in the brain and endometrium may decrease women’s susceptibility to hyponatremic complications and brain damage.

Vigilant monitoring of fluid intake/output during hysteroscopic surgery is necessary to prevent hyponatremic complications. Avoid the pitfall of erroneously attributing deficits to fluid “in the drapes” by using drapes with a fluid-collection pouch.

The standard of care is use of electronic inflow-outflow measuring systems. Manufacturers of hysteroscopic equipment offer highly accurate electronic fluid monitoring systems that measure the weight of the distending fluid infused and collected rather than relying on manual estimation of deficit. The latter method may be inaccurate since the volume of the supply bag can vary by as much as 10%.

Adjust intrauterine pressure to reduce the likelihood of intravasation. High intrauterine pressure may be desirable for visualization, but it greatly increases the risk of intravasation.

I adjust pressure and flow rates by opening or closing the inflow and outflow valves of the resectoscope until slight amounts of bleeding from resected tissue can be visualized. Since intrauterine pressure is extremely difficult to monitor accurately during operative hysteroscopy, this practice ensures that it remains below the patient’s mean arterial pressure, thus minimizing the risk of intravasation.

Use a dilute vasopressin injection to constrict blood vessels and decrease the chance of intravasation.

Vaporizing electrodes for myoma resection and ablation seal blood vessels and reduce fluid absorption.

Guidelines for distention media

To reduce the likelihood of these complications, I recommend that surgeons:

• Draw preoperative serum electrolytes for a baseline in all patients.
• Give all patients with myomas 2 monthly injections of depot leuprolide acetate (3.75 mg intramuscularly). Give patients without fibroids a single injection 4 to 6 weeks prior to the procedure.
• Place a fluid-collection drape or a larger, plastic Mayo stand cover with the bottom cut off under the patient’s buttocks so that fluid drains into a “kick” bucket. Also adjust the resectoscope’s outflow tubing to drain into the collection bag, which should be kept on constant suction to the flow-stat electronic fluid monitor.
• Continuously record inflow and outflow using the electronic monitor with the deficit alarm set to 500 mL.
• Keep distention fluid at room temperature and monitor the patient’s core temperature continuously. Significant fluid intravasation will lower the patient’s temperature, and this may be the first sign of fluid overload.
• Perform operative hysteroscopy under spinal or epidural anesthesia so the anesthesiologist can continually assess the patient’s sensorium. Confusion and irritability are early signs of dilutional hyponatremia.
• If the fluid deficit reaches 750 mL, immediately give 20 to 40 mg of intravenous furosemide and draw a serum sodium. Do not wait for the result of the sodium level before treatment, since a 5- to 20-minute delay can be catastrophic.
• Interrupt the procedure for 5 to 10 minutes to allow the uterus to contract and to seal off small blood vessels.
• Discontinue the procedure if the fluid deficit reaches 1,500 mL or if the serum sodium level is below 125 mEq/L.

I do not limit the duration of resectoscopic procedures as long as fluid deficits are below 750 mL, as measured by electronic fluid monitor. I also ensure that the operating room staff is well educated in the use of the monitor and able to troubleshoot intraoperatively.

If the machine fails during the procedure, reset it with the alarm limit lowered to reflect the deficit recorded before failure.

Monitor the color of the outflow fluid. Excessive blood loss counted as part of the outflow can occasionally mask a distention fluid deficit.

Choosing a distention medium

There is no ideal distention medium for monopolar operative hysteroscopy. Several authors have suggested that 5% mannitol is advantageous since it is isosmolar and acts as an osmotic diuretic. However, it does not prevent hyponatremia. The main disadvantage of 5% mannitol is its high cost and limited availability in 3-L bags or 4-L bottles.