CHF may rarely complicate the acute phase of KD When this is because of myocarditis, routine treatment with IVIG generally results in rapid clinical improvement Although IVIG therapy involves infusing large volumes of isotonic solution—2 g/kg of 5% IVIG delivers 40 mL/kg over to 12 hours—improvements in myocardial contractility compensate for the volume load, and treatment rarely leads to circulatory deterioration By the second week of illness, and especially in children with coronary artery dilatation, ischemia or infarction must be excluded as causes of new myocardial dysfunction Kawasaki Shock Syndrome An uncommon complication (7% in one study from a single institution), Kawasaki shock syndrome has been recognized as a complication that can occur during the acute phase of the illness, unrelated to IVIG infusion It is defined as systolic hypotension for age, or signs of poor perfusion It was noted that the patients who developed shock syndrome were more likely to be female, to have laboratory findings consistent with greater inflammation (higher CRP levels), more severe laboratory abnormalities (e.g., lower platelet counts, hyponatremia, hypoalbuminemia, and consumptive coagulopathy), and to have impaired cardiac function All cases required fluid resuscitation and about half required inotropic support These patients seem to have greater incidences of coronary artery abnormalities and IVIG resistance Other Complications Arthritis occurs in approximately one-third of children with KD Because it is rare in many of the conditions that may mimic KD, the presence of synovitis adds supportive evidence for the diagnosis in ambiguous cases The arthritis tends to involve the small joints of the extremities during the acute phase of illness and the large joints during the second and third weeks The arthritis of KD is always nondeforming and self-limited, generally resolving within 30 days Anti-inflammatory medications such as ibuprofen are usually effective in relieving symptoms until spontaneous resolution occurs Refractory Kawasaki Disease KD may recur in 1% to 2% of children within 12 months of diagnosis, and an additional 5% to 10% of children treated with IVIG and aspirin may respond poorly to IVIG treatment during the initial bout of illness In fact, patients who fail to respond completely to IVIG pose the greatest therapeutic dilemma Prolonged fever itself correlates with increased risk of developing coronary artery abnormalities, and fever lasting for more than 14 days identifies a group of children at risk for developing giant coronary artery aneurysms (internal diameter >8 mm), the group that is most susceptible to infarction and sudden death In cases of persistent, recurrent, or recrudescent KD, there are multiple options, including retreatment with a second dose of IVIG, g/kg over to 12 hours The risk of additional IVIG seems to be minimal, and several studies show a dose response to