ASA classification as predictor of Postop outcomes

Summary by Ricki Pad DO, 08.29.22
https://pubmed.ncbi.nlm.nih.gov/8881629/

Take Home Point:

  • The highest risk odds ratio for developing a postoperative complication was associated with worsening ASA classification and “major” vs “minor” or “moderate” operation 

  • Overall mortality rates:

    1. ASA I – 0.1%

    2. ASA II – 0.7%

    3. ASA III – 3.5%

    4. ASA IV – 18.3%

    5. ASA V – 93.3%  

  • The major limitation of this study is the subjective nature of the ASA classification system. As you can probably see in practice the amount of variability a single patient can have in their classification.

Summary:

Prospective study of 6301 surgical patients in a university hospital, studied strength of ASA classification and perioperative risk factors using both univariate analysis and odds ratio of the risk of developing a postoperative complication.

 

AIM: evaluate the prognostic value of ASA classification with regard to perioperative variables such as blood loss, duration of ICU stay, postoperative complication and mortality

Patients and Methods

  • All patients operated on in Department of general and vascular surgery between May 1, 1989 and April 30, 1993

  • Patients assessed before operation by two experienced anesthetist (one of which was a consultant), assigned a ASA classification based on the 1963 ASA classification system

    • Patient data looked at – preoperative disease states (anemia, HTN, previous MI/stroke, smoking status, pulmonary function, diabetes mellitus, acute/chronic renal failure, major intestinal disease)

    • Operations were classified according to the Hoehn system (total time, blood loss, minor v moderate v major operation) 

  • Postoperative outcomes were obtained:

    • Pulmonary complications: bronchopulmonary infection, positive sputum culture, CXR, atelectasis or pleural effusion

    • Cardiac: significant arrhythmias, ECG changes, increase in cardiac enzymes

    • Wound: inflammation or purulent wound discharge

    • Genitourinary: culture positive UTI

  • Analysis

    • Comparison between ASA and perioperative variables

    • Univariate analysis of the relationship between the most prevalent preoperative events disease states and the incident of major postoperative events
       

Results

  • Of 6301 patients, more than 75% of patients classified as ASA II or III, 15 patients were classified as ASA V

    • 14 patients died in hospital - excluded from statistical analysis on morbidity

  • Major preoperative disease states identified were arterial hypertension, smoking, severe bronchopulmonary disease, and major gastrointestinal disease

  • Perioperative variables in relation to ASA –

    • Increase in duration of operation between ASA I and ASA II-IV (P < 0.05), and between ASA II and III (P < 0.05)

    • Intraoperative blood loss was 5-20 fold greater in ASA IV than in ASA I-III (P<0.05)

    • Postoperative intensive care unit and total hospital stay of ASA II-IV were 1-5 and 7-11 days longer than ASA I (P <0.05)

    • Threefold increase in cardiac complications was found in between individual classes I-IV (P <0.05)

    • Postoperative wound and UTI infections 2-3 times greater in ASA classes II-IV than class I

    • HTN and previous MI implied 50% increase in developing cardiac complication

    • Severe bronchopulmonary disease implied significant increase in cardiac or pulmonary complication and increased duration of postoperative ventilation

  • Highest risk odds ratio for developing a postoperative complication were associated with worsening ASA classification and a “major” vs a “moderate” or “minor” operation per Hoehn

  • ASA IV implied a risk odds ratio of 4.26 times higher risk of developing postoperative complication than ASA I

 
Discussion

  • Few studies have examined relationship between ASA physical status and perioperative morbidity, this study identified several specific intra- and postoperative variables significantly correlated with ASA classification

  • Major drawback of the ASA system is assessment of a patient’s correct ASA classification by different anesthetists, to minimize this variability, ASA class was performed by two anesthetist adhering strictly to 1963 criteria.

  • This study highlights the value of ASA classification in the prediction of postoperative complications.