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Ressources et utilitaires

Scoring systems for ICU and surgical patients:

PIM (Paediatric Index of Mortality) 

References

• F. Shann et al. Paediatric index of mortality (PIM) : a mortality prediction model for children in intensive care. Intensive Care Med. 1997;23:201-7.
• G.A. Pearson et al. Calibration of the paediatric index of mortality in UK paediatric intensive care units. Arch Dis Child. 2001;84:125-128.

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Help

PIM is calculated from information collected at the time a child is admitted to ICU.
Because PIM describes how ill the child was at the time intensive care was started, the observations to be recorded are those made at or about the time of first face-to-face (not telephone) contact between the patient and a doctor from intensive care unit (or a doctor from a specialist paediatric transport team).
Use the first value of each variable measured within the period from the time of first contact to one hour after arrival in ICU. The first contact may be in ICU, or emergency department, or a ward in your own hospital, or in another hospital (e.g. on a retrieval).
The pupils' reactions to light are used as an index of brain function; do not record an abnormal finding if this is probably caused by drugs, toxins or local injury to the eye.
If information is missing (e.g. base excess not measured), record zero (except for systolic blood pressure, which should be recorded as 120); PIM assumes that missing values are normal (eg that the base excess is 0 if it is not measured).

Common mistakes in collecting PIM data

1. Do not to over-diagnose the specified conditions - if there is any doubt, do not record a specified condition. For example: do not code cerebral haemorrhage for intracerebral bleeding associated with trauma ; impaired cardiac function associated with sepsis or surgery should not be coded as cardiomyopathy ; Downs Syndrome should not be coded as IQ <35 ; and a static disability should not be coded as neurodegenerative (even if it is severe) unless there is progressive ongoing loss of milestones.

2. You should record the first value of each variable from the time of first contact up to one hour after arrival in your ICU (not the worst value).

3. If a variable is not measured within one hour of admission to ICU it should be coded as missing (for example, if the first blood gas is not done until two hours after admission, the base excess and PaO2 should both be coded as missing). Missing data is treated as being normal when PIM is calculated.

4. The PIM equation is used to calculate the PIM logit. If any information is missing, that variable should add nothing to the PIM logit. For example, if the PaO2 or the FiO2 is missing, the value of "0.415 x 100 x FiO2 / PaO2" should be set to zero.

5. Record the FiO2 being given at the same time that the first PaO2 is measured (that is, both the FiO2 and PaO2 that you record must relate to the same time).

6. Read very carefully the definition, "booked [pre-arranged] admission to ICU after elective surgery; or elective admission for a procedure (e.g. insertion of a central line), or monitoring, or review of home ventilation.

7. The pupils are only recorded as fixed if both are >3 mm, and both are fixed, and the finding is not caused by drugs or toxins or direct injury to the eye.

8. If systolic blood pressure is not measured in the first hour, record 120 - do not record zero.

9. Randomly sample about every 20^th admission to your ICU and get another person to collect the PIM data independently a second time, so that you can check the accuracy of your data.

10. You should include all admissions to your ICU, not just selected cases.

Interpretation of PIM

PIM should only be applied to groups of patients. It should not be used to make decisions about the management of individual patients, or even to describe individual patients.

PIM predicts about 40% fewer deaths than the old PRISM II (so your ICU will not look as good with PIM). PIM was developed using data from seven large tertiary PICUs in Australia (almost all ventilated children in Australia are looked after in one of these units) and a large PICU in the UK, where the standard of care is high. PRISM II is based on data collected in 1984-85 (and outcomes have improved since then), and PRISM uses the worst results in the first 24 hours in ICU - because about 45% of deaths occur in this period, PRISM will tend to make children who die look sicker.

If PIM does not predict the correct number of deaths in your unit, this may be because the score does not work well in your environment, or because the standard of care in your unit is better or worse than in Australia. Some PICUs have changed the PIM formula so that it predicts outcomes better for their patients. This defeats one of the main purposes of the score, which is to allow you to compare your performance with that of the Australian and UK units that developed it (but you can still use it to look at trends in your own unit over time).

Elective admission

Booked admission to ICU after elective surgery; or elective admission for a procedure (e.g. insertion of a central line), or monitoring, or review of home ventilation.

Underlying condition

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