Surgical Risk

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Surgical Risk

Benefits and Risk
Hospital Screening Tests to Minimize Surgical Risk


Surgical risk is the set of potential adverse medical circumstances that may arise from having surgery, or the dangers and harm that may occur. Risk is determined by surgical risk factors, which are any set of circumstances that increase the risk of surgical complications. Surgical complications are any negative medical results that deviate from the normal expected outcomes of surgery, or the expected recovery scenario.


Specific subsets of the population are at higher risk for serious complications after surgery. People who are more vulnerable to surgical complications and therefore have a higher risk include the elderly, the obese, people who are in very poor physical condition from disease, lack of exercise, or malnourishment, people who have a compromised immune system such as AIDS patients, people with certain heart conditions, and smokers.

Benefits and Risk

By nature, surgery is a risky business. However, those risks have been greatly minimized by modern technology and the high standard of physician surgical training. Surgeons usually undergo the rigors of nearly a decade of intensive training and education before they perform surgeries on their own. Experience is key to becoming a qualified surgeon, and so is included even in the early training stages of a surgeon’s career. A qualified surgeon is a highly trained and skilled professional who can serve certain patients to improve or even save their lives. It can be overwhelming to read the long list of potential complications that may arise from having surgery. However, it is important to note that most of these complications are anticipated and measures are taken to avoid harm to the patient. Surgery saves many lives each year, and should be viewed in light of considering the potential benefits as well as the potential risks.


The degree of surgical risk varies between different surgical procedures, as well as with the individual medical aspects associated with each patient. The risk a patient takes when having a surgical procedure is a combination of the risks associated with the procedure itself as well as risks associated with specific patient-based factors regarding surgery. Patient-based risk factors are an important part of surgical risk, and help determine the likelihood of a surgical complication occurring. The decision to perform any surgical procedure is based on whether or not potential benefits outweigh the sum of the potential risks.

Procedure-Based Risk

Any patient undergoing surgery is at risk for medical complications that arise from the procedure itself. The specific factors that may potentially cause these complications are called procedure-based risk factors. The surgical procedures associated with the highest level of risk include cardiac surgery, lung surgery, prostate removal, and some major orthopedic surgeries such as hip replacement.

Patient-Based Risk

Many patient-based factors increase the risk of having complications during or after a surgical procedure. Patient-based factors that generally increase risk include advanced age, obesity, poor physical condition, smoking, a compromised immune system, recent heart attack or unstable heart conditions, and malnourishment. Some specific types of surgical procedures may have their own specific types of patient-based risk factors. Specific complications are also associated with certain patient-based risk factors. For example, obesity increases the risk for wound and pulmonary complications after surgery. Smoking cessation for six weeks before surgery decreases the incidence of pulmonary complications.

Risk of Excessive Bleeding

Excessive bleeding is risk factor of undergoing surgery. During any surgical procedure, there may be accidental damage to a major blood vessel. If that damage is not effectively repaired, it may result in excessive blood loss. If procedural damage is done to smaller blood vessels as an expected part of the surgery but is not properly controlled, there may be excessive blood loss. Even without surgical damage to blood vessels, if a patient undergoes too much physical activity soon after having a surgical procedure, they may accidentally open some of the internal or external surgical sites and cause bleeding. Excessive bleeding may result in the patient becoming anemic. Anemia, and the resulting fatigue associated with anemia, is a risk of surgical procedures. If a very large amount of blood is lost, it can lead to complications much more serious than anemia. A very large loss of blood risks the patient going into a state of shock.

Disorders of blood clotting predispose a surgical patient to bleeding complications. If the patient’s blood has a defective ability to clot, the body cannot properly close small wounds in a normal manner. Instead, even small cuts that are part of the surgical procedure can result in excessive or prolonged bleeding that may be life threatening. If surgery is a necessity in this type of patient, physicians can appropriately manage these conditions prior to the procedure to minimize the risk for bleeding complications.

Risk of Seroma Formation

A seroma is an internal collection of bodily fluids at a surgical site. Seromas may result from improper wound closure or as a complication of the specific procedure. For example, breast surgery is associated with a high risk of seroma formation, even when performed properly. The presence of a seroma may delay wound healing and also increases the risk of developing an infection. Seromas are more likely to form in obese individuals, or individuals whose body forms an excessive volume of fluids that need to be drained from the surgical site during the recovery period.

Risk of Infection

Hospitals may contain types of bacteria that the average person in the United States is not normally exposed to, or mutated strains of common bacteria. Having surgery and staying in the hospital may increase the risk of being exposed to these types of bacteria. Additionally, the emergence of antibiotic resistant strains of bacteria complicates the risk of infection after surgery. Infections with mutated strains of bacteria that are resistant to available antibiotics are especially difficult to prevent, treat, or control.

Risk of infection is associated with any type of surgical procedure. To minimize the chance of a patient contracting a bacterial infection, some surgical procedures involve prophylactic application of antibiotics. Surgical procedures that may involve antibiotic prophylaxis include bowel surgery, procedures that include insertion of prosthetic material, surgeries on patients with impaired immune systems, neurosurgery, cardiac surgery, and ophthalmic surgery. In addition to antibiotics, proper surgical technique in an appropriately clean operating room setting also minimizes risk of infection. Surgeons “scrub in” to surgery, meaning that they follow specific protocols of hand washing and dressing in surgical gowns that minimize risk of infection. The surgical site on the patient’s body also needs to be effectively disinfected before the procedure can be performed. However, even with proper protective measures taken, there is risk of contracting a bacterial infection at surgical sites after having a procedure.

Bacterial infections after surgery may also occur in the urinary tract when a urinary catheter is used, in the respiratory tract if the patient needs to be on a respirator after the procedure, or may be systemic infections that lead to sepsis. Patients with compromised immune systems are at especially high risk of contracting bacterial infections that healthier individuals are usually able to resist. Other patient-based risk factors for post-surgery infection include a pre existing infection before surgery, low levels of certain non-immune blood components, advanced age, obesity, smoking, diagnosis of diabetes, certain cardiovascular diseases, a physiological state of shock, excessive physical trauma, and requiring a blood transfusion. The organism most often associated with infection of surgical sites in the hospital is Staphylococcus aureus, which may be resistant to many current antibiotics such as methicillin.

Risk of Neurological Damage

Surgical procedures may involve risk of neurological damage, or damage to the nervous system. Depending on the type of surgery, nerve damage may be a result of direct injury to the brain, spinal cord, or peripheral nerves. Nerve damage from a surgical procedure may also occur secondary to the administration of spinal, epidural, or regional anesthesia, or from a temporary reduction of oxygen flow to a specific part of the body. Depending on the part of the nervous system that sustains damage, the results may be mild to severe, temporary or permanent. For example, head and neck surgery is associated with risk of injury to numerous delicate nerves, some of which may result in a permanent state of Bell’s palsy if damage occurs.

Risk of Postoperative Delirium

Although most patients experience a temporary state of confusion when they come out of anesthesia, having a surgical procedure may carry the risk of postoperative delirium. Delirium is a severe state of mental confusion, disorientation, agitation, and general incoherence. Delirium may also include hallucinations. Postoperative delirium is a temporary state of delirium that may be caused by multiple factors relating to the surgical procedure. A postoperative temporary state of delirium may occur if the patient experiences a lack of oxygen, hypotension, or sepsis as a result of the surgical procedure. Patient-based risk factors for postoperative delirium include advanced age, pre-existing dementia, chronic drug or alcohol abuse, certain metabolic disorders, side effects of certain medications such as merperidine, and sleep deprivation. Because individuals of advanced age are at higher risk for postoperative delirium, the mental status of elderly patients is frequently assessed in postoperative recovery. If delirium occurs, the patient’s oxygen levels are checked, and all non-essential drugs are temporarily discontinued. With proper treatment, post-operative delirium usually goes away within 72 hours.

Risk of Anesthesia Complications

A patient undergoing general anesthesia for a surgical procedure runs the risk of a temporary, minor disturbance in mental function after the procedure. Patients may experience slight confusion, disorientation, and decreased general mental acuity after having anesthesia for a surgical procedure. This mental state may take up to a week to fully dissipate, and may affect the patient’s ability to work or operate an automobile. Patient-based factors that increase the likelihood of anesthesia complications include advanced age, obesity, and kidney or liver insufficiencies resulting in poor metabolism of the anesthetic agent.

Risk of Cardiac Complications

Cardiac complications are another surgical risk factor. Certain types of anesthesia such as halothane may cause a cardiac arrhythmia during the induction of anesthesia. Additionally there are other factors that may contribute to cardiac complications after surgery. Certain drugs, excessive pain, certain acid-base imbalances, and problems with oxygen delivery during surgery may lead to arrhythmias. Post-operative hypertension may also occur as a result of poor pain management after a surgical procedure. Patient-based risk factors for postoperative hypertension include advanced age, congestive heart failure, and angina.

There is a slight risk of heart attack associated with non-cardiac surgeries, and a greater risk associated with cardiac or vascular surgeries. Risk factors for heart attack associated with surgery are pre-existing congestive heart failure, angina, atherosclerosis, pre-existing anemia, hypotension or anemia as a result of blood loss during surgery, defective oxygen delivery during surgery, and advanced patient age.

Risk of Other Organ-Based Complications

Any surgical procedure performed on or around an organ system has some risk of damage to that system. The following are examples of organ-based surgical risk factors. Pancreatitis (inflammation of the pancreas) is a rare complication as a result of surgery. However, within the cases of pancreatitis that do exist, approximately 10% are related to injury during surgical procedures. When a surgical procedure is performed in the physical vicinity of the pancreas, approximately 1-3% of patients may develop pancreatitis. If the surgical procedure involves maneuvering the actual biliary tract, the incidence of pancreatitis rises. Patient surgical risk factors that predispose to pancreatitis include previous history of pancreatitis, parathyroid surgery which alters blood levels of calcium very quickly and in a short period of time, cardiopulmonary bypass, and renal transplantation.

Surgeries involving the contents of the abdomen have risk for temporarily disrupting the normal movement of the intestines, a condition known as postoperative intestinal ileus. If the intestines are handled too much or are damaged, or certain types of postoperative pain medications are overused, the normal propulsive movements of the bowels may cease completely. While this condition is temporary and treatable, the patient cannot eat or drink until normal intestinal movement is restored. Postoperative ileus may cause abdominal distention, pain, constipation, and vomiting; require a prolonged hospital stay; or contribute to a regional bacterial infection.

Risk of Vascular Complications

Several vascular complications may result from a surgical procedure. If a procedure involves the placement of a central line, air may be introduced into the body cavity outside of the lung, and then collapse the lung. If a catheter is left open air may enter the blood stream, travel to, and affect the proper functioning of the heart.

Deep Venous Thrombosis (DVT) is a condition where a blood clot (thrombus) forms in a blood vessel. DVT occurs in approximately 40% of postoperative patients. Clots usually form in the lower extremities. To prevent DVT, support hose and compression devices are used during surgical procedures. DVT is dangerous because if a clot becomes an embolus (clot that detaches from the vessel wall and travels through the bloodstream) and goes into the pulmonary system (pulmonary embolus) it can be life threatening. It is one of the most common causes of sudden death in hospitalized patients and is a risk factor if a surgical procedure requires a long period of bed rest during recovery.

Pulmonary emboli may be caused by multiple types of clots in addition to DVT, and are a type of surgical risk. For example pulmonary emboli may also be caused fat droplets entering the bloodstream during joint replacement surgery. Patient-based risk factors for a pulmonary embolus during surgery include advanced age, heart disease, obesity, and varicose veins.

Risk Associated with Blood Transfusions

Patients undergoing some surgical procedures carry the risk of needing a blood transfusion. Blood transfusions may cause a dangerous immune system reaction against the blood type or other blood components of the transfusion. These reactions can make the patient very sick or may even become anaphylactic and life threatening. To prevent the likelihood of an immune reaction, blood is carefully matched to the patient in a way that minimizes risk. Although the blood used for blood transfusions is screened for known viruses, transmission of an unknown virus is a possibility.

Risk of Pulmonary Complications

Pulmonary complications are a main cause of postoperative illness. Pulmonary complications may be caused by patient-based risk factors or surgical procedure-based risk factors. Many pulmonary complications after surgery involve part of the respiratory system partially collapsing, usually within 48 hours of a surgical procedure. Other potential respiratory/pulmonary complications involve lung infections, difficulty breathing, or aspirating (breathing in) regurgitated gastric secretions while under general anesthesia. While under anesthesia the parts of the body that normally protect the respiratory system from taking in food or fluids (the epiglottis and esophageal sphincter) are relaxed. Therefore safeguards have to be set in place for protection. Endotracheal tubes are tubes placed in the throat to minimize the risk of breathing regurgitated stomach contents down into the respiratory tract. If food or fluids from the stomach enter the respiratory tract, it may result in pulmonary complications associated with high mortality rates. In order to avoid these complications patients are asked to fast from food before surgical procedures requiring general anesthesia, are positioned carefully for surgery, and carefully fitted with an endotracheal tube.

Patient-based risk factors associated with different types of pulmonary complications include advanced age, obesity, pre-existing chronic lung disease, and smoking history. Surgical procedure-based risk factors include procedures requiring a long duration of anesthesia, prolonged mechanical ventilation, thoracic or upper abdomen surgery, abdominal distention, inadequate pain control that results in the patient not coughing effectively after the procedure, oversedation due to administration of too much anesthesia, excessive


  • Why do I need a surgical procedure?
  • What are alternative options to surgery?
  • What are the potential benefits of this procedure?
  • What are the potential risks of this procedure?
  • What outcomes are anticipated if I do not have the surgical procedure?
  • Who would perform the procedure?
  • How many times has my surgeon performed this procedure before?
  • Are there any patient-based risk factors that could be altered to minimize risk?
  • Will any of my medications, over-the-counter medicines, and nutritional or herbal supplements affect my recovery from this procedure?
  • How long should recovery be expected to take?
  • Will I have to stay in the hospital after the procedure?

postsurgical pain killer use, or an endotracheal tube that is not positioned correctly.

Tool-Based Risk

The tools used during surgery pose a risk for damage to organs, nerves, or blood vessels. Scalpels, cauterizers, needles, and clamps may be mishandled and accidentally cut, burn, pierce, or cause blunt trauma to the body. Even minimal access surgeries such as a laparoscopy involve tool-based surgical risk. Tool-based risks of laparoscopies include the use of trocars, a tool used to make the first incision or entry into the abdominal cavity. If a classic trocars is used in the first “blind jab” into the abdomen, before a camera can be inserted, the physician may push too hard on the trocars and damage blood vessels or internal organs. Any surgical tool poses a risk for damage, and is only as safe as the skill of the surgeon wielding it.

Hospital Screening Tests to Minimize Surgical Risk

Hospitals may perform laboratory tests before admitting a patient for surgery in order to catch patient-based risk factors that predispose for surgical complications and treat them. Pre-surgery tests such as urinalysis, chest x-rays, or complete blood counts may identify potential risk factors that could lead to complications. Commonly performed pre-surgery tests include:


Acquired Immunodeficiency Syndrome (AIDS)— A disease syndrome in which the patient’s immune cells are destroyed by HIV virus, leaving the patient open to opportunistic infections that a healthy immune system could keep at bay.

Anaphylactic— A serious allergic reaction to a foreign protein or other material.

Anemia— A physiological state in which the number of red blood cells or amount of hemoglobin in the blood is abnormally low, leading to a decrease in the capacity of the blood to carry oxygen to the tissues.

Angina— Disease involving decreased oxygen flow to the heart and often constricting chest pain.

Aspiration— The act of inspiring or sucking foreign fluid or vomit into the airways.

Atherosclerosis— Disease involving irregularly deposited fat within the arteries that results in medical complications.

Bell Palsy— One-sided paralysis of the face that may be due to damage to the facial nerve.

Cardiac Arrhythmia— An irregular heartbeat.

Cardiac Pulmonary Bypass— A procedure where heart blood is diverted into an inserted pump in order to maintain appropriate blood flow.

Catheter— A flexible tube inserted into the body to allow passage of fluids in or out.

Central Line— A catheter passed through a vein into large blood vessels of the chest or the heart; used in various medical procedures.

Deep Venous Thrombosis (DVT)— Blood clot that usually forms in the lower extremities after prolonged inactivity.

Delirium— An altered state of consciousness that includes confusion, disorientation, incoherence, agitation, and defective perception (such as hallucinations).

Electrocardiogram (ECG)— A medical tool used to monitor the electrical impulses released by the beating heart. The results are drawn out in graphical fashion to visualize the function of the heart.

Embolus— A plug of blood cell components, bacteria, or foreign body that travels through the bloodstream, lodges, and occludes a blood vessel.

Endotracheal Tube— Tube inserted in the throat during general anesthesia to prevent aspiration of gastric contents into the respiratory tract.

Epidural Anesthesia— Regional anesthesia produced by injecting the anesthetic agent into an area near the spinal cord.

Epiglottis— A leaf-shaped piece of cartilage lying at the root of the tongue that protects the respiratory tract from aspiration during the swallowing reflex.

Esophageal Sphincter— Muscle at the opening to the stomach that keeps the stomach contents from traveling into the esophagus.

Glucose— A form of sugar used by the body for energy.

Hypotension— Low blood pressure.

Hypovolemia— An abnormally low amount of blood in the body.

Intestinal Ileus— Mechanical or dynamic obstruction of the bowel causing pain, abdominal distention, vomiting, and often fever.

Laparoscopy— Minimally invasive surgical procedure in which small incisions are made in the abdominal or pelvic cavity and surgical tools are used with a miniature camera for guidance.

Merperidine— A type of narcotic pain killer that may be used after surgical procedures.

Methicillin-resistant Staphylococcus aureus (MRSA)— A strain of Staph. bacteria that is resistant to methicillin and hence poses a greater health threat because it is difficult to control or kill.

Pancreatitis— Inflammation of the pancreas.

Parathyroid Gland— An endocrine gland that modulates calcium in the body.

Platelet— A blood component responsible for normal clotting mechanisms that seal small wounds.

Prophylaxis— The prevention of disease or infection, or of a process that can lead to disease or infection.

Sepsis— A dangerous physiological state of extensive, systemic bacterial infection.

Seroma— A seroma is an internal collection of fluid at a surgical site.

Spinal Anesthesia— Regional anesthesia produced by injecting the anesthetic agent into an area directly around the spinal cord.

Thrombus— A blood clot attached to a blood vessel wall.

Trocars— A surgical tool shaped as a hollow cylinder that is sometimes used to make an initial incision into a body cavity and through which other surgical tools are then passed.

White Blood Cell— A component of the blood involved in the immune response.

  • Chest x-rays for patients with shortness of breath, chest pain, or a cough
  • Electrocardiogram (ECG) for patients with chest pain or abnormal heart signs
  • Urinalysis for patients with urinary problems, side pain, kidney disease, or diabetes
  • White blood cell count for patients with a suspected infection, or on medications known to affect white blood cell counts
  • Platelet count for patients with excessive blood loss, alcoholism, or on medications known to affect platelet count
  • Glucose levels for patients with excessive sweating, tremors, diabetes, cystic fibrosis, an altered mental status, or alcoholism
  • Potassium levels for patients with congestive heart failure, kidney failure, muscle weakness, diabetes, or on medications known to affect potassium levels
  • Sodium levels for patients with pulmonary disease, central nervous system disease, congestive heart failure, or some types of liver disease



The Merck Manual of Diagnosis and Therapy Eighteenth Edition. 2006.

General Surgery Board Review Series. Lippincott Williams & Wilkins. 2000.

The Merck Manual Home Edition 2004.


Cheadle, W. G. “Risk Factors for Surgical Site Infection.” Surgical Infections 7, no. 1 (2006).

Weinstein, Robert A. “Nosocomial Infection Update.” Emerging Infectious Diseases, Special Issue 4, no. 3 (July-September 1998; updated April 3, 2008). [accessed April 3, 2008].


American Association for the Surgery of Trauma, 633 N Saint Clair St, Suite 2400, Chicago, Illinois, 60611,(312)202-5252, (800)789-4006, (312)202-5013,

American Academy of Orthopaedic Surgery, 6300 North River Road, Rosemont, Illinois, 60018-4262, (847)823-7186, (847)823-8125,

American Academy for Thoracic Surgery, 900 Cummings Center, Suite 221-U, Beverly, Massachusetts, 01915, (978)927-8330, (978)524-8890,

Maria Basile, PhD