[1] Univ Stellenbosch, Dept Paediat & Child Hlth, Fac Med & Hlth Sci, POB 241, ZA-8000 Cape Town, South Africa
[2] Univ Stellenbosch, Tygerberg Hosp, Fac Med & Hlth Sci, Dept Anaesthesia & Crit Care, Cape Town, South Africa
[3] Stellenbosch Univ, Div Cardiothorac Surg, Dept Surg Sci, Tygerberg, South Africa
[4] Tygerberg Hosp, Tygerberg, South Africa