To the Editor:
The ASA (American Society of Anesthesiologists) Physical Status Classification System is the most widely used system globally to describe a patient's preoperative medical condition. The first four categories (P1–P4) in the classification have changed little since they were first proposed in 1941,1
and are familiar to all anesthesiologists.
However, the fifth category, P5, as a description of a moribund patient, was first introduced in 19612
and adopted by the ASA in 1963.3
Initially P5 was defined as “a moribund patient who is not expected to survive for 24 h with or without
operation [emphasis added].”3,4
However, this definition was changed during the 1980s (Karen Bieterman, M.L.I.S., Librarian, American Society of Anesthesiologists, Wood Library-Museum of Anesthesiology, Park Ridge, IL, written communication) to “a moribund patient who is not expected to survive without
the operation [emphasis added].”†
This change was not merely minor nor semantic, however, as the earlier definition implied that the P5 patients would be unlikely to survive 24 h irrespective of operative intervention, while the later (current) definition suggests that survival is possible—but only with operative intervention. Moreover, the current definition has no time period specified. In other words, these two definitions describe two different types of patients.
Unfortunately, this change appears to have been missed by many researchers and authors. For example, in the 7th edition of Anesthesia
P5 is defined as “a moribund patient who is equally likely to die in the next 24 h with or without
surgery [emphasis added].” Similarly, in the 6th edition of Clinical Anesthesia
P5 is defined as “moribund patient who has little chance of survival, but is submitted to surgery as a last resort (resuscitative effort).” Several recent journal articles have also incorrectly defined P5. For example, Aplin et al
quoted the earlier definition, as did Sidi et al
whereas others, such as Skaga et al
have quoted the later, current ASA definition.
This persistent misquoting of the definition for P5 has implications for clinicians and investigators. It means that, unless a specific definition or reference is provided, it will not be clear to what “P5” refers. It also means that data from studies using the earlier definition cannot be compared directly to data from studies using the later definition. Of greater concern is the fact that many studies do not specify which definition of P5 has been used.
Whether P5 is used appropriately to describe patients' preoperative physical status, or less appropriately as a surrogate risk score, the ASA Physical Status Classification System, including P5, is used extensively in anesthesia and surgery. All clinicians and investigators should be aware of the current definition for P5, and be alert for the potential use of an incorrect definition, either defined or undefined.
Nicholas M. Thackray, F.A.N.Z.C.A., Neville M. Gibbs, F.A.N.Z.C.A.,
Sir Charles Gairdner Hospital, Nedlands, Australia. email@example.com
† American Society of Anesthesiologists. ASA Physical Status Classification System. Available at: http://www.asahq.org/clinical/physicalstatus.htm
. Accessed November 24, 2010. Cited Here...
1. Saklad M: Grading of patients for surgical procedures. Anesthesiology 1941; 2:281–4
2. Dripps RD, Lamont A, Eckenhoff JE: The role of anesthesia in surgical mortality. JAMA 1961; 178:261–6
3. American Society of Anesthesiologists: New classification of physical status. Anesthesiology 1963; 24:111
4. Owens WD, Felts JA, Spitznagel EL Jr: ASA physical status classifications: A study of consistency of ratings. Anesthesiology 1978; 49:239–43
5. Fischer SD, Bader AM, Sweitzer B: Preoperative evaluation, Anesthesia, 7th Edition. Edited by Miller RM. Philadelphia, Churchill-Livingstone, 2010, pp 1002
6. Hata TM, Moyers JR: Preoperative patient assessment and management, Clinical Anesthesia, 6th Edition. Edited by Barash PG, Cullen BF, Stoelting RK, Cahalan MK, Stock MC. Philadelphia, Lippincott, Williams & Wilkins, 2009, pp 573
7. Aplin S, Baines D, De Lima J: Use of the ASA physical status grading system in pediatric practice. Paediatr Anaesth 2007; 15:216–22
8. Sidi A, Lobato EB, Cohen JA: The American Society of Anesthesiologists' Physical Status: Category V revisited. J Clin Anesth 2000; 12:328–34
9. Skaga NO, Eken T, Søvik S, Jones JM, Steen PA: Pre-injury ASA physical status classification is an independent predictor of mortality after trauma. J Trauma 2007; 63:972–8
© 2011 American Society of Anesthesiologists, Inc.