Ovarian hyperstimulation syndrome (OHSS) is a complication of ovarian induction that may be caused by any agent that stimulates the ovaries. Over the last 10 years, the incidence has risen due to the increased use and development of in-vitro fertilisation (IVF) treatments, where the ultimate goal is to produce enough oocytes and embryos. It is thought to be the most common complication of IVF treatment, though the true incidence is unknown, because mild to moderate cases are probably under-reported.
OHSS occurs 3-8 days after treatment with human chorionic gonadotrophin (hCG), and the effects continue throughout the luteal phase. A variety of cytokines and pro- inflammatory mediators such as vascular endothelial growth factor are secreted from the hyperstimulated ovaries, leading to increased vascular permeability and a prothrombotic effect. The condition may become severe enough to warrant intensive care admission.
Problems and special considerations
Clinical manifestations of the syndrome are:
• Enlargement of the ovaries
• Pleural effusion
• Ascites
Additional complications that may occur include:
• Hypovolaemic shock
• Renal failure
• Acute lung injury
• Thromboembolism
• Cerebrovascular disorders
Women undergoing ovarian stimulation who develop OHSS may be classified by the severity of their presenting symptoms and signs (Table 2.1).
Management options
Prophylactic plasma expanders such as human albumin solution may reduce the risk of severe OHSS in women at high risk; these include women with a large number of oocytes retrieved, high oestradiol levels or polycystic ovary syndrome.
Once suspected, the diagnosis of OHSS is made on clinical grounds as there are no specific diagnostic tests. However, the combination of elevated haematocrit with reduced serum osmolality and sodium levels is highly suggestive. Pelvic ultrasound may demonstrate multiple ovarian follicles, enlarged ovaries or free fluid.
Table 2.1 Grading of ovarian hyperstimulation syndrome
|
Grade |
Features |
|
Mild |
Abdominal distension and discomfort |
|
Moderate |
Abdominal pain, nausea, vomiting and diarrhoea Ultrasound evidence of ascites |
|
Severe |
Clinical ascites ± hydrothorax, oliguria, haematocrit > 0.45, hypo-osmolality, hyponatraemia, hyperkalaemia, hypoproteinaemia |
|
Critical |
Tense ascites/large hydrothorax, haematocrit > 0.55, white cell count > 25 x 109/l, oliguria/anuria, thromboembolism, acute respiratory distress syndrome |
Adapted with permission from RoyalCollege of Obstetricians and Gynaecologists. The Management of Ovarian Hyperstimulation Syndrome. Green-top Guideline 5. London: RCOG, 2016.
Mild to moderate forms of OHSS will be self-limiting and can be managed in the outpatient setting with analgesia, antiemetics and oral hydration, but those women with more severe pathology are likely to require hospitalisation for monitoring and intravenous fluids to correct the hypovolaemia and haemoconcentration.
Ultrasound-guided paracentesis should be considered for women with severe pain, abdominal distension, respiratory compromise or oliguria thought to be secondary to ascites. In women with impaired renal function, dopamine has been given to improve renal perfusion. Ultrafiltration and intravenous reinfusion of ascitic fluid has been used in severe cases. Thromboprophylaxis must be considered.
Monitoring is tailored to the severity of the syndrome, and the following progression is recommended:
• Urea and electrolytes
• Full blood count and packed cell volume
• Plasma/urine osmolality
• Clotting screen
• Chest radiography
• Invasive haemodynamic monitoring may be beneficial for those with a reduced urine output or persistently raised haematocrit despite large volumes of fluid replacement.
Clinicians should be aware that pregnancies complicated by OHSS have an increased risk of pre-eclampsia and preterm delivery.
Key points
• Hyperstimulation comprises ovarian enlargement, pleural effusion and ascites, which may be relentless.
• Severe protein loss may result in shock and renal failure.
• The most severe form occurs in 1-2% of cases treated with human chorionic gonadotrophin.
Further reading
Budev M, Arroliga A, Falcone T. Ovarian hyperstimulation syndrome. Crit Care Med 2005; 33: S301-6.
Royal College of Obstetricians and Gynaecologists. The Management of Ovarian Hyperstimulation Syndrome. Green-top Guideline 5. London: RCOG, 2016. www.rcog.org.uk/en/guidelines-researc h-services/guidelines/gtg5 (accessed December 2018).
Sansone P, Aurilio C, Pace MC, et al. Intensive care treatment of ovarian hyperstimulation syndrome (OHSS). Ann N Y Acad Sci 2011; 1221: 109-18.