Appendix

PIM is calculated from information collected at the time a child is admitted to your ICU. Because PIM describes how ill the child was at the time you started intensive care, 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 your 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 your ICU. The first contact may be in your ICU, or your 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 (e.g. that the base excess is 0 if it is not measured). Variables 1–7 are descriptive variables that are not needed to calculate PIM. Include allchildren admitted to your ICU.

(1)

Identifier (e.g. ICU admission number):

(2)

Age (months):

(3)

Diagnostic group (1 = Resp, 2 = CVS, 3 = Postop, 4 = Accident, 5 = Neurol, 6 = Other):

(4)

Date admitted to ICU (dd/mm/yyyy):

(5)

Days in ICU on this admission:

(6)

Endotracheal tube in situ at any time during this ICU admission (no = 0, yes = 1):

(7)

Outcome of ICU admission (discharged from ICU = 0, died in ICU = 1):

(8)

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 (no = 0, yes = 1):

(9)

Record the number in square brackets if the condition is present (if in doubt, record 0): [0] none [1] cardiac arrest out of hospital [2] severe combined immune deficiency [3] malignancy after completion of 1st induction [4] spontaneous cerebral haemorrhage from aneurysm or AV malformation [5] cardiomyopathy or myocarditis [6] hypoplastic left heart, <1 mth, requiring Norwood [7] HIV infection [8] IQ <35, worse than Down's [9] a neurodegenerative disorder (progressive ongoing loss of milestones)

(10)

Response of pupils to bright light (>3 mm and both fixed = 1, other = 0, unknown = 0):

(11)

Base excess in arterial or capillary blood, mmol/l (unknown = 0):

(12)

Pao₂, mm Hg (unknown = 0):

(13)

Fio₂ at time of Pao₂ if oxygen via ETT or headbox (unknown = 0):

(14)

Systolic blood pressure, mm Hg (unknown = 120):

(15)

Mechanical ventilation at any time during the first hour in ICU (no = 0, yes = 1):

example of how to calculate pim

Child has: pupils react (fixed = no = 0), myocarditis (specified diagnosis = yes = 1), emergency admission (elective = no = 0), ventilated (= yes = 1), systolic blood pressure 40 mm Hg, base excess −16.0 mmol/l, Fio₂ 1.00, and Pao₂ 60 mm Hg.

PIM logit = (2.357 × 0) + (1.826 × 1) + (−1.552 × 0) + (1.342 × 1) + (0.021 × absolute(40 − 120)) + (0.071 × absolute(−16.0)) + (0.415 × 100 × 1.00/60) − 4.873 = 1.803.

Predicted probability of death = e^logit / (1 + e^logit) = 2.7183^1.803 / (1 + 2.7183^1.803) = 0.8585, or 86%.

At <www.pedsccm.wustl.edu/clinical/pim-readme.html> there is a free program that calculates PIM.

common mistakes in collecting pim data

(1)

Do not overdiagnose the specified conditions (number 9 on the form)—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; Down's 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. “Lymphoma/leukaemia after 1st induction” has been changed to “malignancy after 1st induction”.

(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 are 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 × 100 × Pao₂/Fio₂” 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)

Make sure that you are consistent about the Pao₂ units (all mm Hg, or all kPa), and the Fio₂ (all between 0.0 and 1.0, not percentages between 0 and 100).

(7)

Read very carefully the definition, “booked [prearranged] 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”.

(8)

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.

(9)

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

(10)

Randomly sample about every 20th 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.

(11)

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