1. Department of Anesthesiology; Centro Infantil Boldrini; Campinas; SP; Brazil
2. Department of Pediatric Surgery; School of Medical Science - Unicamp; Campinas; SP; Brazil
3. School of Mathematics; Federal University of Uberlandia; Uberlandia; MG; Brazil
4. Department of Anesthesiology; School of Medical Science - Unicamp; Campinas; SP; Brazil