• Incidence of adverse events. [ Time Frame: Followed for the length of the procedure. ] [ Designated as safety issue: Yes ]
• Clinically significant changes in heart rate, blood pressure, and oxygen saturation. [ Time Frame: Followed for the length of the procedure. ] [ Designated as safety issue: No ]

• - incidence of adverse events
• - clinically significant changes in heart rate, blood pressure, and oxygen saturation

This study will examine whether the combination of two anaesthetic medications, propofol and remifentanil, is suitable for short duration surgical procedures, providing a shorter recovery time and fewer side effects than either drug used alone.

Propofol is the primary medication used by anesthesiologists at HSC to provide sedation for lumbar puncture. Propofol provides amnesia, anxiolysis, and hypnosis, but because propofol has no analgestic properties patients often respond to the pain of LP needle insertion. To ensure patient immobility, the dose of propofol is often increased, resulting in a duration of action that is excessive for lumbar puncture. Remifentanil is an ultra-short acting opioid which can be used to provide analgesia and sedation for short painful procedures with minimal residual pain. However, when used as the sole agent, remifentanil is associated with a high incidence of respiratory depression and/or arterial oxygen desaturation and does not provide amnesia or anxiolysis. The combination of propofol and remifentanil may be particularly suitable for short duration procedures, providing a shorter recovery time and fewer side effects than either drug used alone.

The objective is to determine the minimum effective dose of remifentanil required to prevent movement for insertion of a lumbar puncture needle when co-administered with propofol. The results obtained from this study will be used in a future study of the recovery characteristics of propofol and remifentanil in children undergoing lumbar puncture.

• Hematologic Diseases
• Neoplasms

Inclusion Criteria:

• Clinical diagnosis of a hemato-oncological disorder
• Scheduled to undergo a lumbar puncture
• Aged 4-11 years
• Male or female
• Unpremedicated
• Willing and able to provide informed consent (or informed consent by parents)

Exclusion Criteria:

• Children who are known or suspected to be difficult to ventilate by face mask
• Children who are deemed medically unfit to receive either of the two study medications
• Children who are obese (weight for height > 95th percentile,
• Children who do not have an indwelling intravenous line