Malnutrition in surgical patients is associated with poor wound healing, increased rates of infection, longer hospital stay, and higher mortality. Volume shifts, increased hemodynamic changes, and tissue injury all contribute to an acute phase reaction, which increases metabolic demands. Catecholamines and cortisol increase protein turnover and muscle breakdown as fat and protein are shuttled to essential organs. Weakened respiratory muscles contribute to atelectasis, pneumonia, and prolonged respiratory failure. Immunity is impaired as cell growth and cell turnover are decreased.
From the VA Cooperative study comparing outcomes of patients with mild, moderate, and severe malnutrition, preoperative nutritional supplementation is indicated for severely malnourished patients awaiting major surgery but who cannot tolerate oral intake for five days prior to intervention. Such high-risk patients include cancer patients who have lost more than 10% of their body weight, or other patients who have lost 15% of their body weight in the preceding six months.
Enteral nutrition reduces complications and improves outcomes over parenteral nutrition. Enteral feeding prevents atrophy associated with disuse and helps the gastrointestinal tract provide a barrier to infection. Trials comparing enteral and parental nutrition have consistently found that enteral nutrition has fewer complications and improved survival compared with parenteral nutrition. Patients with head and neck malignancies and other anatomic barriers to oral intake may benefit from placement of a gastrostomy or jejenostomy tube. Postpyloric feeding is indicated in cases of gastric outlet obstruction or early satiety.
Nasogastric and orogastric routes are indicated for short-term feeding because they are relatively minor interventions and are associated with fewer complications. However, caution must be taken when placing nasogastric or orogastric tubes in obtunded patients who are at increased risk for aspiration and inadvertent placement in the respiratory tract. Postplacement radiographs of styleted tubes confirming placement are indicated for all patients.
- For nasogastric (NG) and orogastric (OG) tubes, postplacement radiographs of styleted tubes to confirm placement are indicated for all patients to reduce risk for aspiration and inadvertent placement in the respiratory track.
Enteral nutrition is not safe for patients with bowel obstruction. Patients with an ileus should not be fed enterally until the ileus resolves; feeding in some instances puts the patient at risk for vomiting and possible aspiration. Most patients with escalating vasopressor requirements should not be enterally fed because the gut mucosal integrity may be impaired; these patients also have an increased risk for intestinal ischemia. Some clinicians advocate for restricting all forms of enteral nutrition for patients who are hypotensive or receiving pressor agents due to the resultant ileus and relative bowel ischemia that may ensue. Enteral nutrition may be used cautiously in patients receiving low-dose vasopressor support, while monitoring for gut ischemia and ileus.
Most nutritional formulas provide all essential elements and minerals and contain 1–2 kcal/ml. Specific tube feeding formulas have been developed for patients with renal disease, respiratory failure, hepatic insufficiency, and diabetes. Elemental formulas are provided to patients with malabsorptive disorders. Patients taking enteral formulas should be monitored for feeding intolerance, hypernatremia, and diarrhea. Patients fed through their stomach should have gastric residuals checked every six hours, and feeds should not be held if residuals are less than 300 ml. Patients fed through the small bowel do not have to have residuals checked. When diarrhea occurs in a tube-fed patient, infectious causes should be ruled out. Whenever there is any doubt about how best to meet a patient's nutritional needs, consultation with a nutritional support service or the surgeon should be initiated.
- Patients receiving gastric tube feeding should have gastric residuals checked every six hours, and feeds should be held only when residuals are greater than 300 ml. Patients fed through the small bowel do not require residuals to be checked.
In cases where enteral nutrition is not possible, total parenteral nutrition (TPN) may be used but is accompanied by an increased risk of central line-associated blood stream infections (CLABSI) and hyperglycemia. Most patients should receive 150% of their total nonprotein calorie needs to optimize their nutrition. Patients should receive at least 1.5 gm/kg of protein as well. For those who are severely malnourished, caloric provision should be reintroduced in a graduated fashion to avoid refeeding syndrome. Refeeding syndrome may occur when nutritional support is given to severely malnourished patients, and metabolism suddenly shifts from a catabolic to an anabolic state. Carbohydrate intake triggers insulin release, with subsequent cellular uptake of potassium, phosphate, and magnesium. When the serum concentrations of these electrolytes are reduced, arrhythmias and severe muscle weakness can occur.
Improvements in nutritional status should be monitored through weekly prealbumin and C-reactive protein (CRP) levels. Traditionally, protein status was monitored by albumin levels. However, albumin has a half-life of 20 days and is not an appropriate measure of short-term nutritional improvement. Its levels are also affected by fluid balance, and so patients with volume overload will have low relative levels.
The half-life of prealbumin is 48 hours, making it a more reliable marker of response to feeding. Unfortunately, during inflammation hepatic synthesis of transport proteins is suppressed, with resultant low levels of prealbumin due to inflammation alone. C-reactive protein (CRP) is an acute phase reactant that peaks 48 hours after the inflammatory insult, and levels of CRP are routinely used to monitor the degree of inflammation and assist in the interpretation of prealbumin levels.
Guidelines from the American Society of Parenteral and Enteral Nutrition (ASPEN) do not recommend nutritional support in well-nourished patients who will resume oral feeding within 7–10 days post surgery. However, patients following emergency surgery, burns, head injury, and orthopedic trauma have particularly high metabolic demands and may need up to 2 gm/kg of protein per day to maintain nitrogen balance. If the need for prolonged enteral support is determined intraoperatively, placement of a gastrostomy or jejenostomy tube during the initial operation should be considered. In this case, feeds can usually be started within a day or two following surgery.
Patients receiving tube feeds may remain malnourished if they never obtain their daily requirements due to frequent interruptions secondary to medication administration or radiologic tests or other procedures. Commonly, tube feeds are held in surgical ICU patients because of high gastric residuals and impending procedures or planned extubation. Clinicians should maintain vigilance in assessing patients' nutritional needs, monitoring patients' actual nutritional intake, and adjusting nutritional provision actively and frequently to support postoperative needs. Consultation with nutrition specialists may be necessary to optimize support.
Candidates for TPN include patients who have undergone massive intestinal resection or who cannot tolerate enteral feeds. Central venous access is required to administer the high levels of dextrose in TPN. Either a subclavian or internal jugular approach is most appropriate for short-term access as femoral catheters have higher risks of thrombosis, infection, and hematomas. TPN poses an increased risk for line sepsis and bacteremia. A peripherally inserted central venous catheter (PICC) or a subclavian tunneled line is preferred for patients requiring long-term parenteral nutrition (more than six to eight days).
In the surgical settings, some surgeons liberally transfuse blood and use triggers of a hematocrit less than 30 or a hemoglobin level less than 10 mg/dL. Liberal use of blood transfusion has been associated with higher mortality. Transfusion has been associated with immunosuppression and increased infectious complications. Despite the risks, clear indications for transfusion remain. Platelet transfusion is indicated in the setting of microvascular bleeding and normothermia. Hypothermia should be corrected before transfusion because cold body temperature can increase platelet dysfunction.
Cryoprecipitate, which contains fibrinogen, factor VIII, von Willebrand factor (VWF), and fibronectin, treats fibrinogen deficiency in consumptive coagulopathy, Von Willebrand deficiency, and hemophilia. Fresh frozen plasma (FFP) contains all of the clotting factors as well as fibrinogen. It is used for emergent transfusion in warfarin-induced coagulopathy, liver disease, and disseminated intravascular coagulation (DIC) prior to procedures or in the event of spontaneous bleeding. In patients without cardiovascular disease, transfusion of packed red blood cells is indicated when the hemoglobin level is 7 mg/dL or less.
Recombinant factor VIIa (rFVIIa) is a synthetic form of factor VII, which activates factors X and IX when it interacts with factor II (thrombin) on the subendothelium. Due to its cost, use of factor rFVIIa has been limited to treatment of coagulopathy from hemorrhagic shock and reversal of Coumadin-induced coagulopathy in head injured patients. Recombinant FVIIa has been shown to increase the risk of thrombosis.
Massive transfusion is defined as the transfusion of more than 10 units of packed red blood cells (pRBCs). Transfusion of pRBCs and crystalloid can cause a dilutional coagulopathy. Recent investigations from the wars in Iraq and Afghanistan have demonstrated improved outcomes with a 1:1:1 ratio of platelets, FFP, and packed red cells. Many trauma centers have resorted to this strategy for massive transfusions. Institutional guidelines vary, and clinicians should work within the guidelines of their local practice environment.
Damage Control Surgery and the Open Abdomen
Damage control surgery is the term most often applied to (1) trauma patients in extremis, and (2) patients with major intraabdominal injury needing immediate control of hemorrhage and contamination but too unstable for definitive immediate repair. After surgical hemorrhage is controlled in the operating room (OR), patients are usually taken to the ICU for resuscitation and stabilization before definitive surgical repair, which is delayed to manage hypothermia, metabolic acidosis, and coagulopathy in the ICU. Typically, patients will have an open abdomen with a temporary closure device. Once stabilized, further evaluation and definitive repairs can be completed.
The SICU as an Operating Room
Transporting critically ill and unstable patients can pose serious risks to the patient and require considerable resources to transfer monitoring devices and ensure that drugs are readily available. A dedicated nurse and a respiratory therapist must travel with an intubated patient, and, if emergent surgery is required, an operating room (OR) must be immediately available. Increasingly, the ICU is used as an alternative to the OR. Unfortunately, ideal operating conditions cannot usually be replicated. The OR provides access to inhalational agents, sterility, room lights, and temperature control that cannot be moved to other locations. However, there are times when scarce OR availability and the patient's condition make bedside procedures preferable. Bedside laparotomy, open and percutaneous tracheostomy, feeding tube placement, and fasciotomies are examples of procedures that can be done at the bedside in emergent or elective circumstances. Emergent laparotomy for abdominal compartment syndrome is sometimes performed at the bedside.
Patients should be prepared as they would be for the OR. Informed consent should be obtained, coagulopathy corrected, and preoperative antibiotics given, if appropriate. If general anesthesia is necessary, an anesthesiologist should be present to manage anesthetics and the airway. At a minimum, one nurse should be present for patient recovery. Blood pressure monitoring, pulse oximetry, and cardiac telemetry should be used during the procedure to monitor vital signs.
Bedside procedures should be handled similarly to those in the OR. All personnel should understand their role. It may be helpful to have OR staff come to the bedside if ICU staff are unfamiliar with OR procedures. Sterile procedures and technique must be used, and all personnel in the room should have caps and masks on. It may be useful to bring sterile drapes from the OR, as they will be large enough to provide ample coverage. Surgeons and instrument technicians should scrub as they would for the OR. Foot traffic in the space should be kept to a minimum.