Ovarian hyperstimulation syndrome (OHSS)

Ovarian hyper stimulation syndrome (OHSS) is the most serious consequence of induction of ovulation. It may occur after stimulation of the ovaries into superovulation with drugs such as human chorionic gonadotrophin (hCG) and human menopausal gonadotrophin. It is rare with clomifene except in polycystic ovarian syndrome (PCOS).

Grades and associated clinical features:

Mild OHSS

• Abdominal bloating.


• Mild abdominal pain.


• Ovarian size usually <8 cm.

Moderate OHSS

• Moderate abdominal pain.


• Nausea ± vomiting.


• Ultrasound evidence of ascites.


• Ovarian size usually 8-12 cm.

Severe OHSS

• Clinical ascites (occasionally hydrothorax).


• Oliguria.


• Haemoconcentration haematocrit >45%.


• Hypoproteinaemia.


• Ovarian size usually >12 cm.

Critical OHSS

• Tense ascites or large hydrothorax.


• Haematocrit >55%.


• White cell count >25 x 109/L.


• Oligo-anuria.


• Thromboembolism.


• Acute respiratory distress syndrome.

Risk factors:

• Polycystic ovarian syndrome (PCOS) greatly increases the risk.


• Younger women are at greater risk.


• High oestrogen levels and a large number of follicles.


• The use of hCG for luteal phase support.


• Administration of gonadotrophin-releasing hormone (GnRH) agonist.

Presentation:

• Symptoms usually appear 4 or 5 days after harvesting of eggs.


• There is abdominal pain and distension due to accumulation of fluid.


• In 1 or 2% of cases with very enlarged ovaries, the patient is ill with severe pain, nausea and vomiting.


• There may also be pleural effusions with fluid passing from the abdomen into the pleural cavity.

Investigations:

• Ultrasound of the ovaries and abdomen for fluid. A possible risk in this condition is torsion of the ovary and ultrasound scan may suggest this.


• FBC,as there may be haemoconcentration. (Serious findings are haematocrit above 45% and white cell count above 15 x 10⁹/L.)


• U&E and creatinine, as renal function may be impaired. (Serious findings are sodium below 135 mmol/L or potassium above 5.0 mmol/L.)


• Coagulation screen.


• LFTs.


• CXR and lateral (to assess any pleural effusion).

Management:

In mild cases:

Analgesia and increased oral fluids will suffice. The condition will settle rapidly unless pregnancy occurs, when it will take longer to subside.
In moderate cases:

Admission to hospital for thromboprophylaxis and monitoring may be judicious.
Severe cases:

These require very careful monitoring of fluid balance:

• An initial bolus of a litre of fluid intravenously (IV) should be followed by enough to maintain urine output of 30 to 40 ml an hour.


• A diuretic should be given if urine output is inadequate.


• Aspiration of ascites or pleural effusion can relieve symptoms.


• Albumin may be given to replace circulating volume and it may need to be given periodically:


• Clear guidance on the management of the acute, severe condition is not available but each aspect is tackled as required and intensive care may be required.

Ovarian hyperstimulation syndrome (OHSS)