Analgesic Effect in Children of Low-Dose Ketamine for Mucositis Treated by Patient-Controlled Analgesia With Morphine

Inclusion Criteria:

* Painful mucositis
* Child from 5 to 18 years.
* Presenting mucitis induced by chemotherapy or a conditioning of graft hematopoïetic.
* A pain not controlled by systematic paracetamol (10mg/kg/4h) or a the propacetamol (20mg/kg/4h).
* Not presenting a neurological or psychological difficulty at the use of the PCA or a EVA.
* First morphine amount going back to less 48h, and lass administration dating of more than 4h at the time of the beginning of the perfusion of Ketamine/placebo (EVA \> 30 after stop morphine).
* Assent signed by the parents and each time possible by the child.

Exclusion Criteria:

* The child was already included in the study.
* The age of psychomotor development is lower than 5 years
* Presence of a depression or a major depressive episode according to definition DSM IV.
* Hepatic or renal anomaly major (rank 3 or 4 of the scale of toxicity NCI CTC v2.0)
* Bilirubin\>3N
* Gamma WP\>3N
* SGOT or SGPT \>5N
* Creatinin\>3N