POSSUM Score Calculator (Operative Morbidity & Mortality) (2024)

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 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.

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)

Log_eR1/1-R1 = -7.04 + 0.13 x Physiological Score + 0.16 x Operative Severity Score
Log_eR2/1-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.