Ovarian Hyperstimulation Syndrome

Ovarian hyperstimulation syndrome (OHSS) is an iatrogenic complication of controlled ovarian stimulation. It can develop after fertility treatment and may occur in a patient who is not yet pregnant or in one who has conceived. It is not ordinary pregnancy-related bloating or edema. The central problem is an acute increase in vascular permeability, mediated primarily by vascular endothelial growth factor (VEGF). Fluid moves out of the intravascular space into the peritoneal cavity, producing ascites, and sometimes into the pleural space, producing a pleural effusion. The patient therefore has excess fluid in the wrong compartment: the abdomen or chest may be filling while the vascular space becomes relatively depleted. That fluid shift explains the characteristic combination of increasing abdominal girth, rapid weight gain, hemoconcentration, tachycardia, hypotension, reduced renal perfusion, and oliguria. It also increases thromboembolic risk because the blood becomes concentrated and circulation is sluggish. Severe fluid shifts can impair breathing, renal function, and cardiac output. The experienced nurse watches the trajectory rather than dismissing one symptom. A patient whose abdomen is enlarging quickly, whose weight has risen sharply, and whose...