Outcome of emergency department patients with delayed admission to an intensive care unit

Emergency Medicine

(2002)

14

, 50–57

Blackwell Science, Ltd

Original Research

Outcome of emergency department patients with delayed admission to an intensive care unit

Meera

Parkhe

,

1

Paul S

Myles

,

2

Deborah S

Leach

1

and Andrew V

Maclean

1

1

Department of Emergency Medicine, Box Hill Hospital and

2

Department of Anaesthesia and

Pain Management, Alfred Hospital, Melbourne, Victoria, Australia

Abstract

Objective:

To compare 30 day mortality, length of stay and cost for adult emergency departmentpatients with a delay in intensive care unit admission of up to 24 h with a group ofpatients admitted directly from the emergency department to the intensive care unit.

Methods:

Retrospective cohort study in a 300-bed university affiliated teaching hospital. Onehundred and twenty-two adult emergency department patients admitted to the intensivecare unit either directly from the emergency department (direct group) or within 24 h ofward admission (delayed group) were identified. The main outcome measuresinvestigated were 30 day mortality, length of stay and cost.

Results:

Thirty day mortality in the delayed group was significantly higher, the risk ratio being2.46 (95% confidence interval 1.2–5.2). The length of stay and cost were similar in thedirect and delayed groups. Baseline estimate of risk of death derived from the mortalityprobability model calculated from the emergency department data was similar for thetwo groups (

P

= 0.10). Emergency department triage categorization and emergencydepartment staff seniority was significantly different (

χ

2

for trends,

P

= 0.002 and 0.023,respectively), with patients in the delayed group more likely to be triaged as less urgentand to be initially assessed by junior staff.

Conclusions:

Our study shows that patients transferred to the intensive care unit within 24 h ofward admission from the emergency department had a significant increase in 30 daymortality compared with patients admitted to the intensive care unit directly fromthe emergency department, but no difference was found in terms of length of stayand cost.

Key words:

delayed admission

,

intensive care unit

,

patient outcome

.

Correspondence: Dr Andrew Maclean, Director, Department of Emergency Medicine, Box Hill Hospital, Nelson Road, Box Hill, Victoria 3128, Australia. Email: [email protected]

Meera Parkhe, MB BS, DA, Registrar; Paul S Myles, MB BS, MPH, MD, FFARCSI, FANZCA, Head of Research; Deborah S Leach, MB BS, DipRACOG, FACEM, Deputy Director; Andrew V Maclean, MB BS, FACEM, Director.

EMM286.fm Page 50 Wednesday, February 6, 2002 9:15 PM

Outcome of delayed admission to ICU

51

Introduction

The identification of ED patients who would benefitfrom admission to an ICU can be difficult. Factorsinfluencing this decision include not only the patient’spresentation, symptoms and signs, but are also relatedto the triage process and accuracy of assessment byemergency department staff, with implications forstaffing levels, supervision and training. The decisionto admit to ICU may also be influenced by the ICUadmission policy, ICU bed availability and the opinionof the treating in-patient team. Intensive care is ofteninitiated in the ED and critically ill patients may spenda substantial amount of time in the ED before transferto the ICU.

1–4

Quality of care before admission to ICU has beenrecognized to influence outcome. McQuillan

et al.

5

have suggested that suboptimal care of severely illpatients before admission to ICU influenced morbidity,mortality and requirement for intensive care, as wellas contributed to ICU length of stay. Previous researchexamining admission source to ICU has shown thatpatients who were transferred to the ICU from otherin-patient sites were more likely to die during theirhospitalization than patients who were admitted fromthe ED.

6,7

Early identification of patients at risk ofdeterioration, intervention before ICU admissionby appropriately trained staff and facilitating accessto intensive care may be effective in decreasingmortality.

7–10

Patients admitted to an ICU late in theirhospitalization are more likely to die than thosewho enter the ICU at the beginning of theirhospitalization.

11

The aim of this analysis was to compare 30 daymortality, length of stay and costs for ED patientswith a delay in admission to ICU of up to 24 hfollowing ward admission with a group admitteddirectly from the ED to the ICU.

Methods

Setting

Box Hill Hospital is a 300-bed teaching hospitalaffiliated with Monash University in Melbourne,Australia. It has a seven-bed adult ICU. All EDpatients are triaged by nursing staff who haveundergone training in the triage process and followprescribed triage guidelines. The nurses are

encouraged to seek medical assistance when in doubt.The ED medical staff consists of emergencyphysicians, registered trainees in Emergency Medicineand rotating junior residents. An emergency physicianor registered trainee is always on duty in thedepartment, as well as an on-call emergency physicianout of hours. During the study period, ICU referrals inoffice hours were made directly to the ICU directorand, after hours, to the ICU consultant on call. TheCCU is separate from the ICU. There was nointermediate care unit in the hospital during the studyperiod.

Patients

Ethics committee approval was obtained for chartreview of ED patients admitted to the ICU from July1996 to December 1997. These patients were admittedto the ICU either directly from the ED or from thehospital wards within 24 h of transfer from the EDand were designated as the direct ICU admissiongroup and the delayed ICU admission group,respectively.

The following patients were included in thestudy:1. Patients admitted to the ICU directly from the ED.2. Patients admitted to the ICU within 24 h of ward or

CCU admission from the ED. (The delayed ICUadmission group was limited to 24 h post-transferfrom the ED in order to include only those patientswho may have been able to be identified to becritically ill or at risk of deterioration while inthe ED.)The following patients were excluded from the

study:1. Patients less than 16 years of age.2. Patients with documented ‘do not resuscitate’

(DNR) orders.3. Interhospital transfers and patients requiring

emergency surgery and postoperative intensivecare. (Outcome in these groups of patients isinfluenced by intra-operative and anaestheticfactors, which are not always identifiable in theED.)

4. Survivors of prehospital cardiorespiratory arrestrequiring endotracheal intubation (ICU admissionis predetermined in these patients; inclusion wouldhave introduced bias).

5. Patients with a known ED diagnosis of drugoverdose. (These patients were generally younger(mean age 34 years), with few or no comorbidities,


M Parkhe

et al.

52

and were known to have a 100% survival. Therewere no drug overdose patients in the delayedgroup. Inclusion would have introduced bias.)

Data collection

Medical records of patients and the ICU database werereviewed. Demographic and outcome informationcollected was entered into a personal computertabulated database.

The following information was recorded:1. Time of ED presentation, ED triage category and

seniority of ED medical staff initially assessing thepatient.

2. ED length of stay.3. Patient age, gender, presenting complaint, past

history, ED observations and ED investigationresults. These data were gathered to assess theseverity of the illness while in the ED and toidentify associated factors.

4. Requirement for endotracheal intubution.5. Time of ICU admission, ICU admission diagnosis

and ICU severity of illness scores. The ICU severityof illness scores were obtained from the ICUdatabase.

6. Intensive care unit and 30 day mortality.7. Intensive care unit and hospital length of stay

and costs. Costs were provided by the hospitalfinance department. Each patient was assignedcosts from appropriate general ledger dependanton their actual use of resources from each departmentor, in the case of an overhead department, anappropriate allocation methodology was used.The summary of methodologies is as follows:

1. Patients length of stay in hospital: administration,catering, facility, corporate.

2. Patients bed-days within the ward: CCU, wardconsumables and labour.

3. Actual cost of interventions performed: dietitian,occupational therapy, physiotherapy.

4. Actual test performed/ items dispensed: pathology,radiology, pharmacy.

5. Allocation based on time and/or service performedin department: emergency, theatre, ICU.

6. Actual cost of issues invoiced by third party:Visiting Medical Officer.

Data analysis

Demographic and clinical data are presented as themean

±

SD, median and range or number (%). Groups

were compared using Student’s

t

-test or the Mann–Whitney

U

-test for numerical variables and Chi-square with Yates’ correction for categorical variables.Risk ratios (RR) are presented with 95% confidenceintervals (CI).

We used the admission mortality probability model(MPM

0

)

12

to measure baseline severity of illness in theED because it is the only validated model currentlyavailable for assessing severity of illness at the timeof ICU admission. It includes a minimum numberof treatment variables and, thus, reflects a baselinemeasure of severity of illness that is independent oftreatment.

12

Severity of illness after ICU admissionwas measured using the Acute Physiology andChronic Health Evaluation (APACHE) II andSimplified Acute Physiology Score (SAPS) IIclassification systems.

13,14

We calculated Kaplan–Meier survival curves forhospital mortality and assessed differences betweengroups with Cox’s proportional hazards regression(adjusting for MPM

0

). We then analysed the entirestudy cohort to identify other univariate associationswith hospital mortality and significant (

P

< 0.05)associations were entered into a stepwise logisticregression model in order to identify independentpredictors. Separate regression models were developedwith and without the addition of the MPM

0

calculatedrisk.

All analyses were performed using

SPSS

forWindows v8.0 (SPSS Inc., Chicago, IL, USA).

P

< 0.05was accepted as significant.

Results

Number of patients

Using the abovementioned inclusion and exclusioncriteria, we identified 99 patients in the direct groupand 23 patients in the delayed group.

Clinical presentation in the ED

Baseline patient characteristics (on presentation to theED) are given in Table 1. Patients admitted directly tothe ICU were generally younger and were more likelyto have tachycardia, whereas patients who had adelayed admission to the ICU were more likely to havea history of respiratory, cardiac and/or gastroin-testinal disease and were more likely to have arterialdesaturation.



53

Table 1. Demographic and clinical features of patients admitted to the ICU on presentation to the ED

Factor Direct group (n = 99)

Delayed group (n = 23)

P

Median (range) age (years) 57 (16–83) 71 (42–87) 0.001Gender, M/F (%M) 59/40 (60) 12/11 (52) 0.68Median (range) triage category* 3 (1–5) 3 (1–4) 0.002ED staff

Consultant 8 (8%) 1 (4%)Registrar 68 (69%) 11 (48%)RMO 23 (23%) 11 (48%) 0.023

No. presentation out of hours (%) 42 (42) 12 (52) 0.54ED length of stay (h) 4.5 (2.5) 5.3 (3.2) 0.26No. patients with a past history† (%)

Cardiac 32 (33) 17 (74) 0.001Respiratory 31 (31) 13 (56) 0.043CNS 7 (7) 4 (17) 0.25Renal 2 (2) 2 (9) 0.33Hepatic 5 (5) 0 0.61Gastrointestinal 8 (8) 8 (35) 0.002Malignancy 7 (7) 0 0.42Other 21 (21) 0 0.90

ED observations‡Highest HR (b.p.m.) 125 ± 35 105 ± 24 0.019Lowest HR (b.p.m.) 96 ± 26 77 ± 23 0.002Highest respiratory rate (breaths /min) 30 ± 10 28 ± 10 0.65Lowest respiratory rate (breaths /min) 22 ± 7 21 ± 6 0.59Highest SBP (mmHg) 151 ± 31 143 ± 28 0.28Lowest SBP (mmHg) 112 ± 28 118 ± 20 0.37Lowest SpO2 (%) 93 ± 6 88 ± 8 0.006

Glasgow Coma score 12.5 ± 4 14.3 ± 3 0.061ED investigation‡

Hb (mg/mL; reference range 120–160) 137 ± 20 138 ± 20 0.85WCC (× 103 /mL; reference range 4–11) 13.9 ± 6 15.6 ± 8 0.27K (mmol/L; reference range 3.5–5) 4.3 ± 0.9 4.2 ± 0.8 0.59Cr (mmol/L; reference range 40–110) 168 ± 238 122 ± 77 0.37Lowest pH (reference range 7.35–7.45) 7.24 ± 0.16 7.14 ± 0.24 0.39Lowest PaO2 (mmHg; reference range 80–100) 113 ± 68 100 ± 35 0.80Highest PaCO2 (mmHg; reference range 34–45) 52 ± 28 26 ± 15 0.21

ED severity of illness scoresMPM0 risk of death 0.10 ± 0.13 0.08 ± 0.05 0.10

*Triage category based on National Triage Scale:23 1, resuscitation; 2, emergency; 3, urgent; 4, semi-urgent; 5, non-urgent. ( Redesignated,Australasian Triage Scale [ATS])

†The total number may be more than the number of patients due to multiple problems in some patients.‡Data are the mean ± SD.ALT, alanine transaminase; APTT, activated prothrombin time; CNS, central nervous system; Cr, creatinine; Hb, haemoglobin; HR, heart

rate; K, potassium; MPM0, admission mortality probability model; PaCO2 , arterial partial pressure of carbon dioxide; PaO2 , arterial partialpressure of oxygen; RMO, resident medical officer; SBP, systolic blood pressure; SpO2 , pulse oximetry oxygen saturation; WCC, white cell count.


M Parkhe

et al.

54

Severity of illness in the ED

The MPM

0

was firstly validated in our studypopulation (all patients). It was found to be stronglyassociated with hospital mortality (

P

= 0.0001), with apositive predictive value of 0.33 and a negativepredictive value of 0.85 (both using a cut off value of

P

< 0.5 to identify survivors). Mean MPM

0

risk ofdeath was found to be 0.10 in the direct group and 0.08in the delayed group. This baseline estimate of risk ofdeath was not found to be significantly different in thetwo groups (Table 1).

Emergency department triage categorization and staff seniority

There was significant difference in ED triagecategorization and in ED staff seniority (

χ

2

for trends,

P

= 0.002 and 0.023, respectively; Table 1), withpatients in the delayed group more likely to be triagedin less urgent categories and to be initially assessed byjunior staff. Time of day at which patients presented tothe ED was not associated with outcome.

Emergency department length of stay and time to ICU admission

There was no significant difference in the ED length ofstay between the two groups (Table 1).

Time to ICU following ward admission in thedelayed group is given in Table 2.

Severity of illness in the ICU

Patients who had a delayed admission to the ICU weregenerally sicker at the time of ICU admission, with anAPACHE II-derived higher risk of death and worseSAPS II scores. The delayed group had a significantlyhigher number of patients admitted to the ICU aftera cardiac arrest. The ICU admission diagnoses(categorized by organ system) are given in Table 3.

Thirty day mortality

There was a significant increase in 30 day mortality inpatients who had a delayed admission to the ICU (35%

Table 2. Time to ICU transfer following ward admission in thedelayed group (n = 23)

Time to ICU (h) No. patients (%)

0–5.99 6 (26)6.00–11.99 7 (30)12.00–17.99 7 (30)18.00–24.00 3 (13)

Table 3. Clinical conditions and severity of illness on admission to the ICU

Factor No. patients (%) PDirect group

(n = 99)Delayed group

(n = 23)

ICU admission diagnosis*Respiratory system 41 (41) 8 (35) 0.73Cardiac arrest 2 (2) 4 (17) 0.011Cardiovascular system0.87 17 (17) 3 (13) 0.87Trauma 17 (17) 2 (9) 0.49Neurological 18 (18) 2 (9) 0.43Sepsis 7 (7) 2 (9) 0.68Renal 7 (7) 1 (4) 1.0Gastrointestinal 5 (5) 4 (17) 0.11Metabolic 7 (7) 2 (9) 0.68Haematological 2 (2) 1 (4) 0.47

ICU severity of illness scoresMean (± SD) APACHE II 15.2 ± 8.4 20.1 ± 13 0.027Mean (± SD) APACHE II-derived risk of death 0.18 ± 0.22 0.32 ± 0.33 0.013Mean (± SD) SAPS II 28.9 ± 15.7 42.2 ± 24.2 0.001

*The total number may be more than the number of patients due to multiple problems in some patientsAPACHE, Acute Physiology and Chronic Health Evaluation; SAPS, Simplified Acute Physiology Score.



55

compared with 14% in the direct group; RR 2.46(95% CI 1.2–5.2); Table 4). This was associated withdecreased survival (hazard ratio 0.23 (95% CI 0.10–0.53); Fig. 1). Intensive care unit mortality was alsofound to be significantly higher in the delayed group(35% compared with 9% in the direct group; RR 3.45(95% CI 1.5–7.8)).

Length of stay and cost

The ICU and hospital length of stay and costs werenot significantly different between the two groups(Table 4).

Discussion

We found that patients in the delayed ICU admissiongroup had a significantly higher mortality whencompared with the direct ICU admission group. It is ofparticular interest that the MPM

0

score, a validatedbaseline estimate of mortality,

12

was not significantlydifferent between the two groups. Severity of illnessscores measured after ICU admission were found to besignificantly different, with the delayed group havinga higher risk of death on ICU admission. Earlyrecognition of severity of illness and optimal medicalcare in the direct group may have been effective inreducing mortality. Goldhill and Sumner

7

suggest thatintervention before ICU admission may be the mosteffective way of decreasing ICU mortality becauselittle can be done in the ICU to alter outcome if, by thetime of ICU admission, the underlying pathology issevere and irreversible.

Involvement of the respiratory system was notablein all stages of our analysis. A surprising finding wasthe significantly lower oxygen saturation in the delayedgroup, as measured by the lowest pulse oximetryreading in the ED. but similar

P

a

O

2

values in the twogroups. It is possible that blood for arterial blood gas(ABG) analysis was drawn while patients werereceiving significant oxygen therapy. Alternatively,inaccurate pulse oximetry readings could explain thisfinding. Lack of appreciation of the significance ofinitial desaturation may have contributed to thedecision to admit to the ward rather than to the ICU.

In the present study, the delayed group had asignificantly higher number of patients admitted tothe ICU after a cardiac arrest. Buist

et al.

15

noted thepresence of documented clinical instability for morethan 24 h in 31 of 122 critical events studied(unplanned ICU admission or a cardiac arrest). Otherinvestigators have found that premonitory signs andsymptoms, most frequently dyspnoea and tachypnoea,commonly precede clinical deterioration and cardio-pulmonary arrest.

8,16–18

The significant differencein ICU admissions following cardiac arrest and thesignificantly different 30 day mortality between thetwo groups, in spite of similar MPM

0

scores in the ED,

Figure 1. Survival after hospital admission, adjusting for baseline risk (mortality probability model; MPM0). (——), direct; (- - - - - -), delayed. Adjusted P < 0.001.

Table 4. Outcome after hospital and ICU admission

Factor No. patients (%) PDirect group

(n = 99)Delayed group

(n = 23)

Mortality < 30 daysICU 9 (9.1) 8 (35) 0.007Hospital 14 (14) 8 (35) 0.044

Length of stay* (days)ICU

Mean ± SD 3.6 ± 5.8 4.7 ± 9.4Median (range) 1.7 (0.1–34) 1.4 (0–38) 0.98

HospitalMean ± SD 8.7 ± 8.6 11.3 ± 10Median (range) 6.3 (0.2–44) 8.0 (0.7–39) 0.19

Median (range) costs ($)ICU 1280 (100–20 300) 1080 (30–26 400) 0.71Total hospital 6120 (750–65 300) 5690 (670–80 000) 0.64

*Survivors only.


M Parkhe et al.

56

could be explained by failure to recognize severity ofillness, rapid development or progression of disease(that may or may not have been present at the time ofhospital admission) or failure to treat adequately,including appropriate discharge destination from theED. Disease manifestation, especially in the elderly,may be subtle and masked by the use of medicationsand coexisting disease, making recognition of severityof illness difficult.

The age distribution of patients in the two groupswas significantly different. Age may have influencedthe decision not to admit to ICU. Age was not found tobe a predictor of outcome after statistical adjustmentand previous studies do not support withholdingtreatment on the sole basis of age.19–21 Coexistentdisease was significantly higher in the delayed groupand a past history of cardiac disease was found to bea predictor of hospital mortality. This may be due tothe prevalence of cardiac disease in the elderly, thesusceptibility of patients with diminished cardiacreserve unable to withstand the effects of severe acuteillness and the possible development of cardiaccomplications contributing to mortality.

In our analysis, the heart rate was significantlylower in the delayed group. This may be due to theconcurrent use of medications or altered physiolo-gical response and may have contributed to failureof recognition of severity of illness. Decreasedphysiological reserve and presence of comorbidconditions may lead to rapid progression of disease,which may be missed in the hospital ward, where vitalsigns are usually observed every 6–8 h. This couldresult in delay in optimal management. Finally,treatment bias in the elderly may result in failure toinstitute appropriate therapy.

Time of day at which patients presented to the EDwas not associated with outcome. This could reflect aconsistent level of medical and nursing care in the ED.Patients in the delayed group were generally triaged toless urgent categories. This suggests that diseasemanifestation on ED presentation may have beensubtle in these patients. It is important to recognizethat patients in less urgent triage categories may havesevere illnesses. These patients were further found tobe initially assessed by less senior medical staff andthis may have contributed to their poorer outcome.We did not find any significant difference in therequirement for endotracheal intubation, length ofstay and costs, both ICU and hospital, between the twogroups, suggesting that ICU and subsequent hospitalmanagement was similar in both groups of patients.

Severity of illness can be graded by a number ofscoring systems12–14,22 that are useful to determinegroup outcome. None of these systems has the abilityto reliably predict outcome in individual patients. TheMPM0 is the only validated measure of illness severitythat can be calculated in patients before they areadmitted to the ICU.12 No scoring system has yet beendeveloped to identify adult patients who should beadmitted to the ICU.22

The delayed group was limited to 24 h post-transferfrom the ED, because we collectively decided it to bea reasonable time limit for early identification ofpatients most likely to deteriorate. We recognize thatpatient condition will change while in hospital andsome patients may deteriorate rapidly and un-expectedly in spite of optimal management and noamount of treatment, ICU or other, would changeoutcome in these patients. We were unable to deter-mine whether ICU consultation had been obtainedfor patients not directly admitted to the ICU. It ispossible that these patients had been identified tobe critically ill or at risk of deterioration while in theED. The resource implications inherent in optimalmanagement of ICU beds may mean that not allpatients who would benefit from an ICU admission canbe accommodated. Knowledge of such constraints mayinfluence the referral pattern of ED doctors. It isconceivable that other patients with similar featureswent to the ward, got better or died and, thus, were notincluded in our study. From this retrospective analysis,we were unable to accurately define response totreatment in the ED, an important variable to beconsidered in decisions about ongoing management.Our study includes no documented DNR patient.However, if severity of illness remains unrecognized,it is unlikely that issues pertaining to resuscitationand life support would be discussed and givenconsideration prior to deterioration. This could resultin inappropriate use of ICU, a limited and costlyfacility.

This study is a retrospective exploratory analysisconfined to adult ED patients in a single hospitalsetting. Retrospective studies suffer from errors ofdocumentation and accuracy. Multiple comparisonsbetween groups increase the likelihood of significantfalse-positive results. Our inclusion and exclusioncriteria were designed to identify patients who weremost likely to have been seriously ill while in the ED.While this introduced patient selection bias in ourstudy and resulted in a small number of patients inthe delayed group, these problems are likely to exist



57

whenever studies on highly specific groups of patientsare undertaken. Our analysis identified importantdifferences between the two groups of patients;however, further research in this area is requiredbefore our results can be generalized.

Conclusions

Our study shows that patients transferred to ICUwithin 24 h of ward admission from the ED had asignificant increase in 30 day mortality compared withpatients admitted to the ICU directly from the ED. TheED is uniquely placed as a first port of call for patientswith acute and serious illness. Recognition of criticalillness in the ED and identification of those at risk ofdeterioration is crucial for optimization of patientoutcome and efficient utilization of scarce health-careresources.

Acknowledgements

We thank Dr Peter Cranswick, former Director ofIntensive Care, Box Hill Hospital, for providing accessto the ICU database. We also thank the staff of theEmergency Department, Intensive Care Unit, Infor-mation Technology Services, Education ResourceCentre, Finance Department and Health InformationServices of Box Hill Hospital, Melbourne, for theircooperation.

Accepted 2 October 2001

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Outcome of emergency department patients with delayed admission to an intensive care unit