Ovarian hyperstimulation syndrome (OHSS) Flashcards
What is the pathophysiology of OHSS?
- Luteinisation of follicles by LH (administered exogenous gonadotrophins) and then hCG.
- OHSS does not occur unless ovulatory dose of hCG is administered.
- Hyperstimulated ovaries secrete VEGF leading in systemic increased capillary permeability and third spacing and intravascular volume depletion.
Define early and late OHSS:
- Early OHSS: occurs within 7 days of hCG injection and associated with excessive ovarian response.
- Late OHSS: occurs within 10 days of hCG injection; usually result of endogenous hCG from early pregnancy. This form is more severe and prolonged.
What is the incidence of OHSS?
0.6-33%
What are the risk factors for OHSS?
- Young age <30 years old
- PCOS
- Lean physique
- hCG administration
- Superovulation (>20 oocytes retrieved)
- High or rapidly rising seru oestradiol.
- Multiple pregnancy
- Previous OHSS
How can you prevent or reduce the risk of OHSS?
- Identifying at risk patients.
- Follicle tracking with ultrasound and cycle cancellation (withholding hCG injection if excessive follicles develop)
- Withholding embryo transfer (elective cryopreservation)
- Luteal phase support with progesterone instead of hCG.
What are some differential diagnoses for OHSS?
- Ovarian torsion
- Ovarian cyst accident
- Ectopic pregnancy
- Bowel perforation
- Pelvic infection and abscess
- Appendicitis
Define mild OHSS:
- Mild abdominal pain
- Abdominal distension
- Ovarian size <8 cm
Define moderate OHSS:
In addition to mild abdominal pain and abdominal distension:
- USS evidence of ascites
- Nausea and vomiting
- Diarrhoea
- Ovarian size between 8-12 cm.
Define severe OHSS:
Any one of the following:
- Clinical ascites
- Hydrothorax
- Haemoconcentrated Hct >0.45
- Electrolyte disturbance.
- Oliguria
- Raised Cr
- Ovarian size >12 cm
Define critical OHSS:
- Tense ascites
- Large hydrothorax
- Haemoconcentrated Hct >0.55
- Oligo- or anuria
- Elevated WCC >25
- VTE
- Acute respiratory distress syndrome
Discuss the history you would take from a woman you suspect has OHSS:
- Time of onset of symptoms relative to trigger.
- Medication used for trigger (hCG or GnRH agonist)
- Number of follicles on final monitoring scan
- Number of eggs collected
- Were embryos replaced and how many?
- PCOS diagnosis?
Symptoms: - Abdominal bloating - Abdominal pain and need for analgesia - Nausea and vomiting - Shortness of breath, orthopnoea, inability to talk full sentences - Reduced urine output - Leg swelling - Vulval swelling Associated comorbidities such as thrombosis
Discuss the examination you would perform for a woman you suspect has OHSS:
General:
- Volume status
- Oedema
- Observations
- Body weight
Abdomen:
- Shifting dullness
- Distension/girth
- Mass
- Peritonism
Respiratory:
- Pleural effusion
- Pneumonia
- Pulmonary oedema
Pelvic:
- Palpable masses / ovaries
- Adnexal tenderness
Discuss the investigations you would order for a woman you suspect has OHSS:
Bloods:
- FBC: haemoconcentration, elevated WCC
- U&Es: elevated Cr, electrolyte disturbance (hyponatremia, hyperkalaemia)
- LFTs: low albumin, abnormal enzymes
- Coags: elevated fibrinogen, reduced antithrombin
- CRP (severity)
- hCG (to determine if pregnant)
Imaging:
- Pelvic USS: ascities, ovarian size, other adnexal masses/collections, ?pregnancy
Adjuncts depending on clinical findings:
- ABG
- D-dimer
- ECG / ECHO
- CXR: pleural effusions, pulmonary oedema
- CTPA or V/Q Scan: PE
Discuss your management of a woman with mild-moderate OHSS only:
- Outpatient management with review every 2-3 days.
- Review acutely if worsening.
- Prophylactic clexane.
- Drink at least 1L/day and measure urine output (at least 1L/day)
- Avoid NSAIDs (renal impairment)
Outline indications for inpatient management of OHSS:
Indications for inpatient management of OHSS:
- Moderate to severe OHSS
- Unable to attend follow-up
- Worsening OHSS
- Unable to tolerate oral fluids due to nausea
- Uncontrolled pain
