The last decade has seen the development of more sophisticated tools capable of providing continuous analysis of parameters that previously required frequent blood sampling or invasive surgical procedures. These include transcutaneous skin electrodes capable of monitoring PO2 and PCO2, the tissue pH electrode, and instrumentation for continuous intravascular analysis of PO2 and PCO2 using polarographic electrodes or specifically designed catheters and a mass spectrometer. Noninvasive monitoring of intracranial pressure is available for the neonate and infant with an open and accessible fontanel.