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Three Part Question

In [critically ill patients on the ICU] is [a raised Troponin level] an [indicator of increased mortality and increased length of hospital stay]

Clinical Scenario

A 65 year old man was admitted to the ICU department with ARDS secondary to acute pancreatitis. He was found to have a raised Troponin on random blood testing. It was considered whether the raised troponin was a poor prognostic indicator for the patient.

Search Strategy

Medline 1966-2007 using the PUBMED and medscape interface.
([troponin OR troponin] AND [critical illness OR critically ill])LIMIT to english

Search Outcome

Altogether 47 papers were found on Pubmed and 21 on Medscape of these 3 were relevant to the three part question

Relevant Paper(s)

Author, date and country	Patient group	Study type (level of evidence)	Outcomes	Key results	Study Weaknesses
Lim W, Qushmaq I, Cook DJ, Crowther MA, Heels-Ansdell D, Devereaux PJ; Troponin T Trials Group. September 2005 Canada	All patients 115 admitted to St Joseph's Hospital from 12 july to 12 september 2004. 22 patients were excluded as they did not have both a Troponin measured and an ECG performed	Prospective cohort	Higher morbidity in patients with MI	37.5% versus 17.6% p= 0.05	Systematic screening was not performed. Clinical judgement was used when deciding to do troponins and ECG.
			Higher morbidity in patients with MI	50% versus 22% p=0.01
			Length of hospital stay	no increase in length of stay
King DA, Codish S, Novack V, Barski L, Almog Y. Aug 2005 Israel	128 consecutive patients admitted to ICU in the Soroka University Centre Hospital	Prospective observational Cohort study	Patients with elevated troponin had higher	a) Apache II scores p = 0.001 b) duration of mechanical ventilation p< 0.001 c) mortality p <0.001	only a one off Troponin measurement was used and not the rise and fall required to meet the diagnostic criteria
			Troponin v Apachie score	no difference in predicition of mortality p=0.08
MD; Deborah J. Cook, MSc(Epid), MD; Lauren E. Griffith, MSc(Math); Mark A. Crowther, MSc, 19/05/2006 USA	198 patients on the ICU at St Josephs between nov 2000 and january 2002. These patients were classified as having myocardial infarction (cardiac troponin I level ≥1.2 µg/L and ischemic electrocardiographic changes), elevated troponin level only (≥1.2 µg/L and no ischemic electrocardiographic changes), or normal troponin levels. Events were classified as prevalent if they occurred within 48 hours after admission and as incident if they occurred 48 hours or later after admission.		Prevelance of Raised Troponin	42.1%	817 patients in total but only 198 used due to strict inclusion criteria
			Prevelance of MI	22.2%
			Incidence of raised troponin	11.8%
			Incidence of MI	5.1%
			Median length of stay	MI-10 days/Raised Trop 8 days/ normal trop 10 days (p=0.7)
			Mortality	MI 44.4%/Elevated troponin 44.4%/normal troponin 33.7% (p=0.33)

Comment(s)

2 out of the 3 papers reviewed showed statistically significant differences in length of hospital stay and mortality for patients with MI. While only 1 out of 3 showed any significant difference in patients with Troponin rise only.

Clinical Bottom Line

Citically ill patients with a raised Troponin in association with myocardial infarction have worse prognosis. However the same can not be said for those patients with an Troponin rise on its own.

References

1. Lim W, Qushmaq I, Cook DJ, Crowther MA, Heels-Ansdell D, Devereaux PJ; Troponin T Trials Group. Elevated troponin and myocardial infarction in the intensive care unit: a prospective study critical care journal 2005;9(6):634-5.
2. King DA, Codish S, Novack V, Barski L, Almog Y. The role of cardiac troponin I as a prognosticator in critically ill medical patients: a prospective observational cohort study critical care journal Crit Care. 2005 Aug;9(4):R390-5. Epub 2005 May 31
3. MD; Deborah J. Cook, MSc(Epid), MD; Lauren E. Griffith, MSc(Math); Mark A. Crowther, MSc, Elevated Cardiac Troponin Levels in Critically Ill Patients: Prevalence, Incidence, and Outcomes American Journal of Critical Care 2006;15(3):280-288