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Purpose
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Ovarian Hyperstimulation Syndrome (OHSS) is an exaggerated response to ovulation induction with FSH and HCG. OHSS is a self-limiting disorder with a broad spectrum of clinical manifestations related to increased capillary permeability and fluid retention mediated by many inflammatory mediators including vascular endothelium growth factor.
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The role of this guideline is to outline the risk factors, clinical features and appropriate management of severe OHSS. The guidelines also aim to assist in determining the appropriate site of care.
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Incidence at the Royal Women's Hospital
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- Out of 2731 stimulated cycles during 2004 there were 15 patients with a severe OHSS an incidence of 0.5%. One of these patients required transfer to an intensive care unit at another hospital.
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- During 2003 the incidence of severe OHSS was 0.1% (3/2691).
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Risk factors
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- Polycystic ovarian syndrome
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Prevention
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The keys to preventing OHSS are experience with ovulation induction therapy and recognition of risk factors for OHSS. Ovulation induction regimens should be highly individualised, carefully monitored, and use the minimum dose and duration of gonadotropin therapy necessary to achieve the therapeutic goal.
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Luteal phase support with hCG (Pregnyl) should be avoided in women with >10 follicles at OPU.
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Caution is indicated when any of the following indicators for increasing risk of OHSS are present:
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- The emergence of a large number of intermediate sized follicles (10-14 mm); and
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- Early symptoms (eg. Abdominal bloating & discomfort prior to OPU).
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Prevention is best achieved by withholding the ovulatory trigger injection of hCG (Ovidrel) if the doctor is concerned about the probable onset of subsequent OHSS. In occasional cases this risk is justifiable to improve the chances of success where previous treatment attempts have failed.
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Given the evidence suggesting that hCG may play a pivotal role in the development of OHSS, hCG 5,000 IU may be prudent for patients judged to be at high risk for OHSS. 8% Progesterone (vaginal gel, daily) for luteal phase support rather than supplemental doses of hCG, may further reduce risks of OHSS. When signs of potential OHSS emerge even before administration of hCG, cycle cancellation and less aggressive stimulation in a subsequent cycle should be seriously considered.
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Prophylactic IV administration of 20% albumin (20 - 50 g) at time of oocyte retrieval has been suggested as a means to reduce risk of OHSS when E2 levels are markedly elevated or there is history of a previous episode of OHSS. Studies of its efficacy have had mixed results, and albumin treatment risks exacerbation of ascites, allergic reactions, and virus/prion transmission. However, a recent meta-analysis of five randomized controlled trials demonstrated that prophylactic albumin administration significantly reduced risk of developing OHSS (odds ratio [OR] 0.28, 95% confidence interval [CI] 0.11, 0.73); albumin infusion may be expected to prevent one case of severe OHSS for every 18 women at risk who are treated.
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Clinical manifestations
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Mild manifestations of OHSS are relatively common and include:
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- Lower abdominal discomfort
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Progression of illness is recognised when symptoms persist, worsen or include ascites. Serious illness exists when abdominal pain is accompanied by one or more of the following:
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- Respiratory difficulty -Pleural effusion
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Assessment / Investigations
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A history should be taken and examination performed to assess the patient with respect to the duration and severity of the symptoms, the presence of risk factors and the existence of any co-morbidities.
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Investigations that complement the assessment include:
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 | - FBE (haematocrit), VRBA, Creatinine, Electrolytes CUE, LFT(albumin), ß-HCG (if >9 days post OPU), coagulation
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| - abdominal ultrasound, CXR
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- ECG if electrolyte imbalance
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Management
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1. Outpatient
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Patients have daily phone contact with Reproductive Services clinic nurses or Melbourne IVF nurses for at least 7 days and report;
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- Assessment of pain / discomfort (score on 1-10 scale)
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- Report any vomiting, nausea, bloating or shortness of breath
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- Symptom score >5 reported to clinician
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2. In-Patient
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- Strict fluid balance including daily weighing and measurement of abdominal girth
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- Monitor electrolytes and correct abnormalities
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- DVT prophylaxis including compression stockings and heparin
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- Physiotherapy including mobilisation and chest physio
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- Analgesia if severe pain may require PCA opiods (avoid NSAID if pregnant)
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- Antiemetic therapy as required
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- Dietician review regarding nutrition
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- Psychological support from all staff but in particular visit from RBU counsellors +/- pastoral care
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- Paracentesis for symptom relief, may not alter the course of the disease
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- Patients requiring high level nursing or experiencing respiratory or other compromises should be managed in the High Dependency Unit.
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- Rarely will patients require transfer to an intensive care unit if the level of care exceeds that which can be supplied at RWH. Such a decision should be made by the anaesthetist in charge of HDU in consultation with the IVF specialist.
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3. Controversies
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a. IV fluid
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The ideal fluid replacement in OHSS is not clear. Both crystalloids and colloids including Albumin can be used to correct intravascular hypovolaemia,
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b. Paracentesis
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Draining ascitic fluid improves symptoms and respiratory function in the short term and may remove some of the mediators of OHSS. The optimal volume of fluid to be removed and over what time interval has not been established. During 2004, 11 of the 15 patients in HDU underwent paracentesis.
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c. Diuretics
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Use should only be considered once intravascular volume has been restored. (Haematocrit < 38%).
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Complications
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- Acute renal failure, hyperkalaemia
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- Infection e.g urine, chest.
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Links
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Royal Women's Hospital Clinical Practice Guidelines (CPGs) are intended to provide guidance to health care professionals, based on a thorough evaluation of research evidence, on the practical assessment and management of specific clinical issues or situations. The guidelines allow some flexibility on the part of the health care professional based on the needs of the specific patient for whom they are caring.
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