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Scores in pediatric intensive care
SCORES IN PEDIATRIC INTENSIVE CARE ~FENNINGER
Pediatric intensive care units (PICU) throughout Europe, when compared together, have quite different structures, tasks and functions. Factors of variability include: age of patients admitted (neonates included/excluded and upper age limit for admissions); medical, surgical or combined unit; if surgical patients are admitted, type of surgery (general pediatric, cardiac, transplantation, trauma etc.); presence/absence and "filter" function of an emergency department in the hospital; presence/absence of a postoperative recovery room; admission and discharge criteria from PICU (potential "export of mortality" to regular wards etc.); organisation and resources; and ethical attitudes. For this reason it is not surprising to find considerable variations in overall mortality rates (4.1 to 20.2 p. 100), acute physiology scores (14.2 to 36) and therapeutic intervention scores (14.5 to 41.1) for clinical classification system class IV patients [1]. In our hospital -- as a practical and representative example -- a retrospective analysis of PICU deaths was done for the years 1988-90 [2]. One hundred and ninety two deaths were registered in 2 207 admissions (overall mortality 8.7p. 100). 103 deaths (53.6 p. 100) occurred in nates (postnatal age at admission to PICU ~< 28 days), although only 677 neonatal admissions (30.7 p. 100 of all admissions) were counted. This results in a neonatal mortality of 15.2 p. 100, compared to 5.8 p. 100 in infants and children. Overall (i.e., all age groups) congenital malformations played a major role (82/192 or 42.7 p. 100) and concerned the cardiovascular system in 52 and the respiratory system and nervous system/skeletal muscle/metabolism in 15 cases each. Prematurity
Abteilungsleiter, Abteilung fDr p&diatrische Intensivbehandlung, Universit&ts-Kinderklinik, Inselspital, CH-3010 Bern, Switzerland.
with pulmonary immaturity and/or cerebral lesionswas another important contributing factor to mortality (30/192 or 15.6 p. 100). Acquired conditions leading to death were hypoxic-ischemic encephalopathy (32/192 or 16.7 p. 100), severe head injury (20/192 or 10.4 p. 100), septic shock (7/192 or 3.7 p. 100), ARDS (7/192 or 3.7 p. 100) and meningitis/encephalitis (6/192 or 3.1 p. 100). Non-survivors received highly significant more ICU-specific monitoring or treatment than survivors (arterial catheters, intracranial pressure monitoring, endotracheal intubation, mechanical ventilation, adrenergic drugs, mannitol, thiopentone, renal replacement therapy etc.). 102 (53.1 p. 100) patients died while receiving full therapy, whereas (43.2 p. 100) died after withdrawing vital support, 7 neonates (3.7 p. 100) did not receive supportive treatment at all. Major factors for the decision to withdraw/withhold treatment were severe brain damage [29], severe malformations/chromosomal anomalies [21] and extreme low birth weight (i.e., severe immaturity) (9 patients). This heterogeneous mixture of ages and underlying diseases makes reliable scoring at least very difficult, if not impossible, because a scoring system has to meet many requirements (simplicity, applicability to all age groups and disease states, reliability for prognostication, lack of influence by therapeutic measures). Several systems have been developed (see table I), probably the best known and tested is the PRISM (pediatric risk of mortality) score. This score has been described by Pollack et al. as a simplification of the Physiologic Stability Index (PSI) [3, 4]. The PRISM score has 14 items which are checked in the first 24 h after admision to the PICU (see table 12). Mortality risk prediction is obtained by the formula: r = 0.207 x PRISM - 0.005 x age in months x 0.433 x operative status - 4.782 (postoperative -- 1, non operative = 0). R~an. Urg., 1994, 3 (2 bis), 191-193
-
192 -
S c o r e s in p e d i a t r i c i n t e n s i v e c a r e
Table I
Overview of scoring system used in neonatal and pediatric intensive care (list not complete)
General scoring systems Clinical classification system (CCS) Therapeutic intervention scoring system (TISS) Physiologic stability index (PSI) Organ system failure score Pediatric risk of mortality score (PRISM) . Rule of 60 ~ Pediatric trauma score Mortality risk for infants of 501-1 500 g
Reference Civetta JM, d Surg Res 1973; 14:265 Keene ARA, Cullen DJ, Crit Care Med 1983; 11:1 Pollack MM et al., Crit Care Med 1984; 12:376 Wilkinson JD et aL, Crit Care Med 1986; 14:271 Pollack MM et aL, Crit Care Med 1988; 16:1110 Sagy M. et aL, Intensive Care Med 1988; 14:646 Tepas J. et al., J Trauma 1988; 28:425 Horbar JD et al., Crit Care Med 1993; 21:12
Specific systems Glasgow Coma Scale (adapted for age) Classification of severe head injury Glasgow meningococcal septicemia prognostic score Oxygenation index
Simpson D, Reilly P, Lancet 1982; I1:450 Pfenninger J. et aL, Z Kinderchir 1984; 39:223 Thomson APJ et aL, Crit Care Med 1991; 19:26 Oritz RM et aL, Pediatr Clin North Am 1987; 34:39
PRISM score has been tested in two hospitals in the UK [5, 6]: Balakrishnan et al. [5] concluded that the PRISM score is institution independent and good for short stay patients. It underpredicts death after cardiac surgery. Only five (i.e, systolic blood pressure, Glasgow Coma Scale, PaCO2, serum bicarbonate and calcium) variables may be needed for satisfactory outcome prediction. Some of the variables (systolic and diastolic blood pressure, heart rate, prothrombin/partial thromboplastin time ratio and serum potassium) need reweighting for PICUs in the UK. Goddard [6] concluded that PRISM scoring overestimated severity of illness in infants. PRISM scoring is not institutionally independent and therefore, at present, a comparison between units may not be justified. A reappraisal of the parameter ranges for infants is suggested. The precursor of the PRISM score, the admission PSI (APSI) has also been tested in Europe by Price and Matthew [7]. These authors found a good correlation between APSI and survival/death, if the first 24 h after admission were considered. APSI did not discriminate well in patients who stayed longer than 24 h in the PICU. There was also a poor discrimination in patients with neurological problems (meningitis, hypoxic-ischemic encephalopathy, etc.). Besides these studies, some additional doubts might be raised: [1] The endpoint of scores (not only PRISM) is often questionable (survival vs. death at the end of the stay in the PICU). However, length ROan. Urg., 1994, 3(2 bis), 191-193
and quality of survival should be of much greater concern [2, 8]. Emotional discomfort: The statistical basis of PRISM score with complex mathematical formulas is unlikely to cause enthousiasm, as we are bound more to highly individualized, traditional Hippocratic thinking, particularly with regard to death. Many colleagues feel overwhelmed by the quantity of data of which not a few are felt to be unnecessary or poorly specified (handling of respiratory data when the patient is on a respirator, adjustment of the Glasgow Coma Scale for age, etc.) [3]. PRISM score and other scores as well do not account for ethical decisions about continuation or withdrawal of life support. However, these decisions, as I have shown initially, play a major role in our institution as in many other European countries [4]. Performance of PRISM scoring is time (and money) consuming. It requires considerable supervision to maintain data collection and accuracy. Don't we have other, more important tasks in and around our ICUs (good standard of patient care, teaching, etc.)? In conclusion it must be realized that an ideal scoring system for pediatric and neonatal intensive care does not exist. If scoring has to be done (request of health authorities, scientific purpose, etc.), a system should be chosen which will give a satisfactory answer to a particular question at the lowest possible price. For daily routine a simple system like CCS or TISS might be sufficient, whereas more complex questions deserve more sophisticated tools.
Scores in pediatric intensive care Table II PRISM score
Variable
Infants
Children
130-160 55-65 > 160 40-54 < 40
150-200 65-75 > 200 50-64 < 50
Diastolic BP (ram Hg)
2 6 7
> 110
Respiratory rate (breath/min)
PaO2/FiO2*
PaCO2** (tort)
Glasgow Coma Score" Pupillary reactions
PT/PTT Total bilirubin (mg/di) Potassium (mEq/L)
Calcium (mg/dl)
Glucose (mg/dl)
Bicarbonate* (mEq/L)
* *
Infants > 160 < 90 Infants 61-90 > 90 Apnea
Children > 150 < 80 Children 51-70 > 70 Apnea all ages 200-300 < 200 all ages 51-65 > 65 all ages < 8
4
1 5
2 3 1 5
[11 BEAUFILSF., ROZE J.C., AZEMA D., HAMOIR G.F., BLOC D., FLORET O., STOPFKUCHEN H., DE JONG DE Vos VAN STEENWlJIK C.C.E., VAN DER VOORT E., MAR MOLINERO F. - - Evaluation of pediatric intensive care in Europe. A collaborative study by the European Club of Pediatric Intensive Care. Intens. Care Med., 1987, 13, 65-70. [2] GERBER M. ~ Zusammenstellung tier Todesf~lle der Jahre 1988-1900 in der intensivpfegestation der Universit&tsKinderklinik Bern. Medical Thesis, University of Bern, 1993. [3] POLLACKM.M,, RUI-I'IMAN U.E, GETSON P.R. - - Pediatric risk of mortality (PRISM) score. Crit. Care Med., 1988, 16, 1110-1116. [4] POLLACK M.M., YEH T.S., RUTTIMAN U.E., HOLBROOK P.R., FIELDS A.L. - - Evaluation of pediatric intensive care. Crit. Care Med., 1984, 12, 376-383. [5] BALAKRISHNANG., AITCHISONT., HALLWORTH D., MORTON N.S. - - Prospective evaluation of pediatric risk of mortality (PRISM) score. Arch. Dis. Child, 1992, 67, 196-200. [6] GODDARD J.M. - - Pediatric risk of mortality scoring overestimates severity of illness in infants. Crit. Care Med., 1992, 20, 1662-1665. [7] PRICE H.L., MATFHEW D.J. - - Evaluation of pediatric intensive care scoring systems. Intens. Care Med., 1989, 15, 79-83. [8] BUFF W., SHANN F., TIBALLS J., WILLIAMS J., CUDDIHY L., BLEWETT L., FARLEY M. - - Long-term outcome of children after intensive care. Crit. Care IVied., 1990, 18, 961-965.
6
all ages unequal or dilated fixed and dilated all ages 1.5 x control > lmo
4 10
> 3.5 all ages 3.0-3.5 6.5-7.5 < 3.,0 > 7.5 all ages 7.0-8.0 12.0-15.0 < 7.0 > 15.0 all ages 40-60 250-400 < 40 > 400 all ages
6
< 16 > 32
-
Score
all ages
HR (beat/rain)
193
References
Age restrictions and Ranges
Systolic BP (ram Hg)
-
u
n
i
2
1 5
2 6
4 8
3
* Cannot be assessed in patients with intracardiac shunts or chronic respiratory insufficiency; requires arterial blood sampling. ** May be assessed with capillary blood gases. * * * Assessed only if there is known or suspected CNS dysfunction; cannot be assessed in patients during iatrogenic sedation, paralysis, anesthesia, etc. Scores < 8 correspond to coma or deep stupor. d Use measured values.
RCan. Urg., 1994, 3 ( 2 bis), 191-193
Pediatric intensive care units (PICU) throughout Europe, when compared together, have quite different structures, tasks and functions. Factors of variability include: age of patients admitted (neonates included/excluded and upper age limit for admissions); medical, surgical or combined unit; if surgical patients are admitted, type of surgery (general pediatric, cardiac, transplantation, trauma etc.); presence/absence and "filter" function of an emergency department in the hospital; presence/absence of a postoperative recovery room; admission and discharge criteria from PICU (potential "export of mortality" to regular wards etc.); organisation and resources; and ethical attitudes. For this reason it is not surprising to find considerable variations in overall mortality rates (4.1 to 20.2 p. 100), acute physiology scores (14.2 to 36) and therapeutic intervention scores (14.5 to 41.1) for clinical classification system class IV patients [1]. In our hospital -- as a practical and representative example -- a retrospective analysis of PICU deaths was done for the years 1988-90 [2]. One hundred and ninety two deaths were registered in 2 207 admissions (overall mortality 8.7p. 100). 103 deaths (53.6 p. 100) occurred in nates (postnatal age at admission to PICU ~< 28 days), although only 677 neonatal admissions (30.7 p. 100 of all admissions) were counted. This results in a neonatal mortality of 15.2 p. 100, compared to 5.8 p. 100 in infants and children. Overall (i.e., all age groups) congenital malformations played a major role (82/192 or 42.7 p. 100) and concerned the cardiovascular system in 52 and the respiratory system and nervous system/skeletal muscle/metabolism in 15 cases each. Prematurity
Abteilungsleiter, Abteilung fDr p&diatrische Intensivbehandlung, Universit&ts-Kinderklinik, Inselspital, CH-3010 Bern, Switzerland.
with pulmonary immaturity and/or cerebral lesionswas another important contributing factor to mortality (30/192 or 15.6 p. 100). Acquired conditions leading to death were hypoxic-ischemic encephalopathy (32/192 or 16.7 p. 100), severe head injury (20/192 or 10.4 p. 100), septic shock (7/192 or 3.7 p. 100), ARDS (7/192 or 3.7 p. 100) and meningitis/encephalitis (6/192 or 3.1 p. 100). Non-survivors received highly significant more ICU-specific monitoring or treatment than survivors (arterial catheters, intracranial pressure monitoring, endotracheal intubation, mechanical ventilation, adrenergic drugs, mannitol, thiopentone, renal replacement therapy etc.). 102 (53.1 p. 100) patients died while receiving full therapy, whereas (43.2 p. 100) died after withdrawing vital support, 7 neonates (3.7 p. 100) did not receive supportive treatment at all. Major factors for the decision to withdraw/withhold treatment were severe brain damage [29], severe malformations/chromosomal anomalies [21] and extreme low birth weight (i.e., severe immaturity) (9 patients). This heterogeneous mixture of ages and underlying diseases makes reliable scoring at least very difficult, if not impossible, because a scoring system has to meet many requirements (simplicity, applicability to all age groups and disease states, reliability for prognostication, lack of influence by therapeutic measures). Several systems have been developed (see table I), probably the best known and tested is the PRISM (pediatric risk of mortality) score. This score has been described by Pollack et al. as a simplification of the Physiologic Stability Index (PSI) [3, 4]. The PRISM score has 14 items which are checked in the first 24 h after admision to the PICU (see table 12). Mortality risk prediction is obtained by the formula: r = 0.207 x PRISM - 0.005 x age in months x 0.433 x operative status - 4.782 (postoperative -- 1, non operative = 0). R~an. Urg., 1994, 3 (2 bis), 191-193
-
192 -
S c o r e s in p e d i a t r i c i n t e n s i v e c a r e
Table I
Overview of scoring system used in neonatal and pediatric intensive care (list not complete)
General scoring systems Clinical classification system (CCS) Therapeutic intervention scoring system (TISS) Physiologic stability index (PSI) Organ system failure score Pediatric risk of mortality score (PRISM) . Rule of 60 ~ Pediatric trauma score Mortality risk for infants of 501-1 500 g
Reference Civetta JM, d Surg Res 1973; 14:265 Keene ARA, Cullen DJ, Crit Care Med 1983; 11:1 Pollack MM et al., Crit Care Med 1984; 12:376 Wilkinson JD et aL, Crit Care Med 1986; 14:271 Pollack MM et aL, Crit Care Med 1988; 16:1110 Sagy M. et aL, Intensive Care Med 1988; 14:646 Tepas J. et al., J Trauma 1988; 28:425 Horbar JD et al., Crit Care Med 1993; 21:12
Specific systems Glasgow Coma Scale (adapted for age) Classification of severe head injury Glasgow meningococcal septicemia prognostic score Oxygenation index
Simpson D, Reilly P, Lancet 1982; I1:450 Pfenninger J. et aL, Z Kinderchir 1984; 39:223 Thomson APJ et aL, Crit Care Med 1991; 19:26 Oritz RM et aL, Pediatr Clin North Am 1987; 34:39
PRISM score has been tested in two hospitals in the UK [5, 6]: Balakrishnan et al. [5] concluded that the PRISM score is institution independent and good for short stay patients. It underpredicts death after cardiac surgery. Only five (i.e, systolic blood pressure, Glasgow Coma Scale, PaCO2, serum bicarbonate and calcium) variables may be needed for satisfactory outcome prediction. Some of the variables (systolic and diastolic blood pressure, heart rate, prothrombin/partial thromboplastin time ratio and serum potassium) need reweighting for PICUs in the UK. Goddard [6] concluded that PRISM scoring overestimated severity of illness in infants. PRISM scoring is not institutionally independent and therefore, at present, a comparison between units may not be justified. A reappraisal of the parameter ranges for infants is suggested. The precursor of the PRISM score, the admission PSI (APSI) has also been tested in Europe by Price and Matthew [7]. These authors found a good correlation between APSI and survival/death, if the first 24 h after admission were considered. APSI did not discriminate well in patients who stayed longer than 24 h in the PICU. There was also a poor discrimination in patients with neurological problems (meningitis, hypoxic-ischemic encephalopathy, etc.). Besides these studies, some additional doubts might be raised: [1] The endpoint of scores (not only PRISM) is often questionable (survival vs. death at the end of the stay in the PICU). However, length ROan. Urg., 1994, 3(2 bis), 191-193
and quality of survival should be of much greater concern [2, 8]. Emotional discomfort: The statistical basis of PRISM score with complex mathematical formulas is unlikely to cause enthousiasm, as we are bound more to highly individualized, traditional Hippocratic thinking, particularly with regard to death. Many colleagues feel overwhelmed by the quantity of data of which not a few are felt to be unnecessary or poorly specified (handling of respiratory data when the patient is on a respirator, adjustment of the Glasgow Coma Scale for age, etc.) [3]. PRISM score and other scores as well do not account for ethical decisions about continuation or withdrawal of life support. However, these decisions, as I have shown initially, play a major role in our institution as in many other European countries [4]. Performance of PRISM scoring is time (and money) consuming. It requires considerable supervision to maintain data collection and accuracy. Don't we have other, more important tasks in and around our ICUs (good standard of patient care, teaching, etc.)? In conclusion it must be realized that an ideal scoring system for pediatric and neonatal intensive care does not exist. If scoring has to be done (request of health authorities, scientific purpose, etc.), a system should be chosen which will give a satisfactory answer to a particular question at the lowest possible price. For daily routine a simple system like CCS or TISS might be sufficient, whereas more complex questions deserve more sophisticated tools.
Scores in pediatric intensive care Table II PRISM score
Variable
Infants
Children
130-160 55-65 > 160 40-54 < 40
150-200 65-75 > 200 50-64 < 50
Diastolic BP (ram Hg)
2 6 7
> 110
Respiratory rate (breath/min)
PaO2/FiO2*
PaCO2** (tort)
Glasgow Coma Score" Pupillary reactions
PT/PTT Total bilirubin (mg/di) Potassium (mEq/L)
Calcium (mg/dl)
Glucose (mg/dl)
Bicarbonate* (mEq/L)
* *
Infants > 160 < 90 Infants 61-90 > 90 Apnea
Children > 150 < 80 Children 51-70 > 70 Apnea all ages 200-300 < 200 all ages 51-65 > 65 all ages < 8
4
1 5
2 3 1 5
[11 BEAUFILSF., ROZE J.C., AZEMA D., HAMOIR G.F., BLOC D., FLORET O., STOPFKUCHEN H., DE JONG DE Vos VAN STEENWlJIK C.C.E., VAN DER VOORT E., MAR MOLINERO F. - - Evaluation of pediatric intensive care in Europe. A collaborative study by the European Club of Pediatric Intensive Care. Intens. Care Med., 1987, 13, 65-70. [2] GERBER M. ~ Zusammenstellung tier Todesf~lle der Jahre 1988-1900 in der intensivpfegestation der Universit&tsKinderklinik Bern. Medical Thesis, University of Bern, 1993. [3] POLLACKM.M,, RUI-I'IMAN U.E, GETSON P.R. - - Pediatric risk of mortality (PRISM) score. Crit. Care Med., 1988, 16, 1110-1116. [4] POLLACK M.M., YEH T.S., RUTTIMAN U.E., HOLBROOK P.R., FIELDS A.L. - - Evaluation of pediatric intensive care. Crit. Care Med., 1984, 12, 376-383. [5] BALAKRISHNANG., AITCHISONT., HALLWORTH D., MORTON N.S. - - Prospective evaluation of pediatric risk of mortality (PRISM) score. Arch. Dis. Child, 1992, 67, 196-200. [6] GODDARD J.M. - - Pediatric risk of mortality scoring overestimates severity of illness in infants. Crit. Care Med., 1992, 20, 1662-1665. [7] PRICE H.L., MATFHEW D.J. - - Evaluation of pediatric intensive care scoring systems. Intens. Care Med., 1989, 15, 79-83. [8] BUFF W., SHANN F., TIBALLS J., WILLIAMS J., CUDDIHY L., BLEWETT L., FARLEY M. - - Long-term outcome of children after intensive care. Crit. Care IVied., 1990, 18, 961-965.
6
all ages unequal or dilated fixed and dilated all ages 1.5 x control > lmo
4 10
> 3.5 all ages 3.0-3.5 6.5-7.5 < 3.,0 > 7.5 all ages 7.0-8.0 12.0-15.0 < 7.0 > 15.0 all ages 40-60 250-400 < 40 > 400 all ages
6
< 16 > 32
-
Score
all ages
HR (beat/rain)
193
References
Age restrictions and Ranges
Systolic BP (ram Hg)
-
u
n
i
2
1 5
2 6
4 8
3
* Cannot be assessed in patients with intracardiac shunts or chronic respiratory insufficiency; requires arterial blood sampling. ** May be assessed with capillary blood gases. * * * Assessed only if there is known or suspected CNS dysfunction; cannot be assessed in patients during iatrogenic sedation, paralysis, anesthesia, etc. Scores < 8 correspond to coma or deep stupor. d Use measured values.
RCan. Urg., 1994, 3 ( 2 bis), 191-193