POSSUM Score for Operative Morbidity and Mortality

Estimates morbidity and mortality in general and orthopaedic surgery patients based on clinical data.

Refer to the text below the calculator for more information about the POSSUM score.


The Physiological and Operative Severity Score for the enUmeration of Mortality and morbidity (POSSUM) processes clinical data in a logarithmic model that derives morbidity and mortality risk.

The score can be used for emergency and elective general surgery (tab 1) or orthopaedic surgery (tab 2) and should be computed at time of surgery (not on admission).

The score is not indicated for trauma patients nor can be used in predicting morbidity and mortality after trauma surgery.


The POSSUM score consists of two components, a physiological score and an operative score that are used in two equations to compute mortality (R1) and morbidity (R2) risks:

  • LogeR1/1-R1 = -7.04 + 0.13 x Physiological Score + 0.16 x Operative Severity Score
  • LogeR2/1-R2 = -5.91 + 0.16 x Physiological Score + 0.19 x Operative Severity Score

Physiological Score

1

Age

2

Cardiac signs | Chest X-ray

3

Respiratory signs | Chest X-ray

4

Systolic blood pressure (mmHg)

5

Pulse (beats/min)

6

Glasgow coma score

7

Urea nitrogen (mmol/L)

8

Sodium (mEq/L)

9

Potassium (mEq/L)

10

Haemoglobin (g/dL)

11

WCC (x1012/L)

12

Electrocardiogram

Operative Score

13

Operative magnitude

14

No. of operations within 30 days

15

Blood loss per operation (mL)

16

Peritoneal contamination

17

Presence of malignancy

18

Timing of operation

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Physiological Score

1

Age

2

Cardiac signs | Chest X-ray

3

Respiratory signs | Chest X-ray

4

Systolic blood pressure (mmHg)

5

Pulse (beats/min)

6

Glasgow coma score

7

Urea nitrogen (mmol/L)

8

Sodium (mEq/L)

9

Potassium (mEq/L)

10

Haemoglobin (g/dL)

11

WCC (x1012/L)

12

Electrocardiogram

Operative Score

13

Operative magnitude

14

No. of operations within 30 days

15

Blood loss per operation (mL)

16

Contamination

17

Presence of malignancy

18

Timing of operation

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The POSSUM Score explained

The Physiological and Operative Severity Score for the enUmeration of Mortality and morbidity (POSSUM) processes clinical data in a logarithmic model that derives morbidity and mortality risk.

The score is recommended for estimating risks in emergency and elective general surgery (tab 1) or orthopaedic surgery (tab 2) and should be computed at time of surgery (not on admission). It can help clinicians in the process of obtaining informed consent when discussing operative risks with patients and families.

The score is not indicated for trauma patients nor can be used in predicting morbidity and mortality after trauma surgery.

The score was originally developed by Copeland et al. in 1991 to provide a scoring system for surgical audit. Data from 1372 patients who underwent emergency and elective surgery was processed. Logistic regression analysis yielded statistically significant equations for morbidity and mortality.

The clinical data that is scored is part of usual admission clinical history and examination so in most clinical settings the cardiological, radiological and biochemical evidence is readily available.

The POSSUM score consists of two components, a physiological score (obtained from scoring 12 variables) and an operative score (obtained from scoring 6 variables). Individual variable scores range from 1 to 8.

The physiological scores range from 12 to 88 whilst the operative scores range from 6 to 48.

Physiological Score Items

Physiological Score
Variable 1 point 2 points 4 points 8 points
Age ≤ 60 61-70 ≥ 71  
Cardiac signs
Chest X-ray
Normal Normal Cardiac drugs or steroids
Oedema; warfarin
Borderline cardiomegaly
Jugular venous pressure
Cardiomegaly
Respiratory signs
Chest X-ray
Normal Normal Shortness of breath on exertion
Mild chronic obstructive airway disease
Shortness of breath on stairs
Moderate chronic obstructive airway disease
Shortness of breath at rest
Any other change
Systolic blood pressure (mmHg) 110-130 131-170 or 100-109 ≥ 171 or 90-99 ≤ 89
Pulse (beats/min) 50-80 81-100 or 40-49 101-120 ≥ 121 or ≤ 39
Glasgow coma score 15 12-14 9-11 ≤ 8
Urea nitrogen (mmol/L) < 7.5 7.6-10 10.1-15 ≥ 15.1
Sodium (mEq/L) > 136 131-135 126-130 ≤ 125
Potassium (mEq/L) 3.5-5 3.2-3.4 or 5.1-5.3 2.9-3.1 or 5.4-5.9 ≤ 2.8 or ≥ 6
Haemoglobin (g/dL) 13-16 11.5-12.9 or 16.1-17 10-11.4 or 17.1-18 ≤ 9.9 or ≥ 18.1
WCC (x1012/L) 4-10 10.1-20 or 3.1-3.9 ≥ 20.1 or ≤ 3  
Electrocardiogram Normal AF (60-90)   Any other change

Operative Score Items

Operative Score
Variable 1 point 2 points 4 points 8 points
Operative magnitude Minor Intermediate Major Major+
No. of operations within 30 days 1   2 > 2
Blood loss per operation (mL) < 100 101-500 501-999 > 1000
Peritoneal contamination No Serious Local pus Free Bowel content, pus or blood
Presence of malignancy No Primary cancer only Node metastases Distant metastases
Timing of operation Elective   Emergency resuscitation possible, operation <24h Emergency immediate operation <2h

Examples of magnitude for general surgery:

  • Minor: hernia, varicose vein, minor perianal surgery, scrotal surgery, minor transurethral resection of tumor, excision of large subcutaneous lesion;
  • Intermediate: open cholecystectomy, laparoscopic cholecystectomy, appendectomy, excision of lesion requiring grafting or minor excision, minor amputation, thyroid lobectomy;
  • Major: laparotomy and small-bowel resection, colonic resection or anterior resection, major amputation, nonaortic vascular surgery, cholecystectomy and exploration of bile duct, total thyroidectomy;
  • Major+: abdominoperineal excision of rectum, aortic surgery, whipple resection, radical total gastrectomy;
Orthopaedic Operative Score
Variable 1 point 2 points 4 points 8 points
Operative magnitude Minor Intermediate Major Major+
No. of operations within 30 days 1   2 > 2
Blood loss per operation (mL) < 100 101-500 501-999 > 1000
Contamination No Incised wound e.g. stab Minor contamination or necrotic tissue Gross contamination or necrotic tissue
Presence of malignancy No Primary cancer only Node metastases Distant metastases
Timing of operation Elective   Emergency resuscitation possible, operation <48h Emergency immediate operation <6h

Examples of magnitude for orthopaedic surgery:

  • Minor: fasciotomy, ganglion/bursa, tenotomy/tendon repair, endoscopic joint surgery, carpal tunnel/nerve release; removal of wire/nail, closed reduction of fracture;
  • Intermediate: excision/osteotomy of small bone, minor joint replacement, amputation of digit(s), closed reduction with external fixation, open reduction of small bone fracture;
  • Major: osteotomy of long bone, ligamentous reconstruction and prosthesis, arthrodesis of large joint, major joint replacement, amputation of limb, disk surgery, open reduction of long bone fracture;
  • Major+: radical tumorectomy, major spinal reconstruction, revision prosthetic replacement of major joint, hind limb/forelimb amputation;

Possum equations for mortality risk (R1) and morbidity risk (R2)

  • LogeR1/1-R1 = -7.04 + 0.13 x Physiological Score + 0.16 x Operative Severity Score
  • LogeR2/1-R2 = -5.91 + 0.16 x Physiological Score + 0.19 x Operative Severity Score
 

Limitations and alternatives

The POSSUM score has been subsequently validated and modified for numerous subtypes of surgery, such as: vascular surgery, colorectal surgery, oncologic gastric surgery, orthopaedic surgery, hepatectomy or emergency laparotomy.

In hepato-pancreatic-biliary surgery, the POSSUM scores were found to overestimate risk.

In 1998, a modified version, the P-POSSUM or Portsmouth POSSUM was derived, and is now considered a more accurate score for the mortality component. The study by Prytherch et al. found that the original POSSUM logistic regression equation for mortality overpredicted the overall risk of death by more than twofold (in patients at lowest risk <5% overpredicted by more than sevenfold).

There are other perioperative morbidity and/or mortality risk predictors available, either for general surgery or for specific diseases and morbidities:

  • The Surgical Apgar Score (SAS) offers a morbidity and mortality risk estimation and whilst it is deemed more objective than POSSUM, it is less comprehensive (uses only 3 intraoperative variables) whilst POSSUM uses several more preoperative variables.
  • The APACHE II model estimates risk of mortality in intensive care patients.
  • The Revised Cardiac Risk Index (RCRI) estimates risk of perioperative cardiac events in patients undergoing heart surgery.
 

References

Original reference

Copeland GP, Jones D, Walters M. POSSUM: a scoring system for surgical audit. Br J Surg. 1991; 78355- 360.

Copeland GP. The POSSUM System of Surgical Audit. Arch Surg. 2002; 137(1):15-19.

Other references

Prytherch DR, Whiteley MS, Higgins B, Weaver PC, Prout WG, Powell SJ. POSSUM and Portsmouth POSSUM for Predicting Mortality. Physiological and Operative Severity Score for the enUmeration of Mortality and Morbidity. Br J Surg. 1998;85(9):1217-20.

Brooks MJ, Sutton R, Sarin S. Comparison of Surgical Risk Score, POSSUM and p-POSSUM in higher-risk surgical patients. Br J Surg. 2005; 92(10):1288-92.


Specialty: Emergency

No. Of Variables: 18

Year Of Study: 1991

Abbreviation: POSSUM

Article By: Denise Nedea

Published On: June 1, 2020 · 12:00 AM

Last Checked: June 1, 2020

Next Review: June 1, 2025