ABS Surgical Critical Care common mistakes
ABS Surgical Critical Care · Understand the traps and how to avoid them.
When answering questions about oxygen delivery (DO2) and consumption (VO2), the candidate calculates DO2 using the arterial oxygen content (CaO2) but forgets to multiply by cardiac output, or uses the wrong units, leading to a numerically incorrect answer and a wrong interpretation of supply-dependence.
The candidate memorizes the formula DO2 = CO × CaO2 × 10 but under exam pressure omits the cardiac output term or misapplies the 10 (dL to L conversion), because they have not practiced the calculation with realistic values and unit checks.
What to do instead
Before the exam, write out the full equations for CaO2, DO2, and VO2 from memory and practice 5–10 calculations with typical ICU values (e.g., CO 5 L/min, Hb 10 g/dL, SaO2 98%, PaO2 100 mmHg). During the exam, always write the units next to each number and verify that the final DO2 is in mL/min (typically 500–1000 mL/min) and VO2 is 200–300 mL/min.
When interpreting arterial blood gases in a patient with a mixed acid-base disorder, the candidate calculates the anion gap but fails to correct it for hypoalbuminemia, leading to a missed diagnosis of an unmeasured anion (e.g., lactate, ketones, toxins) and an incorrect conclusion that the metabolic acidosis is a normal anion gap acidosis.
The candidate memorized the anion gap formula (Na – [Cl + HCO3]) but does not routinely apply the albumin correction (add 2.5 to the anion gap for every 1 g/dL decrease in albumin below 4.0), because they have not internalized that hypoalbuminemia is common in critically ill surgical patients and alters the gap.
What to do instead
Develop a stepwise ABG interpretation checklist that always includes: (1) calculate anion gap, (2) correct for albumin, (3) calculate delta-delta if metabolic acidosis is present, (4) check for appropriate respiratory compensation. Practice with ABG examples from hypoalbuminemic patients until the correction becomes automatic.
In a trauma patient with hemorrhagic shock, the candidate selects a vasopressor (e.g., norepinephrine) as the first-line treatment to restore blood pressure before completing adequate volume resuscitation, rather than prioritizing blood product transfusion and hemorrhage control.
The candidate conflates the management of septic shock (where early vasopressors are appropriate) with hemorrhagic shock, and may be influenced by protocols that emphasize early vasopressors in undifferentiated shock. They fail to recognize that in hemorrhagic shock, vasopressors can worsen tissue hypoperfusion by increasing afterload and may mask ongoing bleeding.
What to do instead
Memorize the principle: in hemorrhagic shock, resuscitation begins with blood products (damage control resuscitation) and simultaneous hemorrhage control; vasopressors are adjuncts only after volume resuscitation is underway or in the presence of vasoplegia. Use a mental algorithm: shock + bleeding → activate massive transfusion protocol, give blood, find and stop the bleeding; add vasopressors only if hypotension persists despite adequate volume and blood products.
When assessing a burn patient's fluid needs, the candidate uses the Parkland formula but forgets to subtract the time elapsed since the burn, or calculates the rate for the first 8 hours from the time of presentation rather than from the time of injury, leading to under- or over-resuscitation.
The candidate remembers the Parkland formula (4 mL × kg × %TBSA) but forgets that half of the calculated volume must be given in the first 8 hours after the burn, and the remaining half over the next 16 hours. They also may not account for the fact that the clock starts at the time of injury, not at the time of arrival.
What to do instead
Practice the Parkland calculation with a time component: e.g., a 70 kg patient with 40% TBSA burn arriving 2 hours after injury. Calculate total 24-hour volume = 4 × 70 × 40 = 11,200 mL. First 8 hours = 5,600 mL, but since 2 hours have elapsed, give 5,600 mL over the next 6 hours (rate ~933 mL/hr), then 5,600 mL over the remaining 16 hours. Always write out the timeline explicitly.
In a patient with acute respiratory distress syndrome (ARDS), the candidate orders a tidal volume of 10–12 mL/kg predicted body weight (PBW) instead of the lung-protective 6 mL/kg PBW, and does not recognize the need to adjust the plateau pressure target (<30 cm H2O).
The candidate may use actual body weight instead of predicted body weight, or may not be familiar with the ARDSNet protocol. They may also fear hypercapnia and increase tidal volume, not understanding that permissive hypercapnia is acceptable.
What to do instead
Memorize the ARDSNet ventilator settings: tidal volume 6 mL/kg PBW (can go down to 4 mL/kg), plateau pressure ≤30 cm H2O, and pH ≥7.20. Practice calculating PBW for a given height and sex. Review the ARDSNet table for adjusting tidal volume based on plateau pressure and pH. Understand that hypercapnia is tolerated as long as pH remains above the lower limit.
When a postoperative patient develops oliguria and hypotension, the candidate attributes it solely to hypovolemia and gives repeated fluid boluses without considering other causes such as abdominal compartment syndrome, cardiac tamponade, or sepsis, and fails to measure intra-abdominal pressure (IAP).
The candidate anchors on the most common cause (hypovolemia) and does not systematically consider the differential diagnosis of shock in the surgical patient. They may not know that abdominal compartment syndrome can occur after massive fluid resuscitation, pancreatitis, or abdominal surgery, and that it requires IAP measurement.
What to do instead
Adopt a systematic approach to shock in the surgical patient: assess for hypovolemia, cardiogenic, obstructive, and distributive causes. In any patient with a tense abdomen, recent abdominal surgery, or massive fluid resuscitation, measure IAP via bladder pressure. Remember that abdominal compartment syndrome (IAP >20 mmHg with new organ dysfunction) requires decompression, not more fluids. Practice creating a differential diagnosis for shock in surgical patients.
In a patient with severe acute pancreatitis, the candidate fails to recognize the risk of infected pancreatic necrosis and does not order appropriate imaging (contrast-enhanced CT) or antibiotics when clinical signs of infection appear, instead attributing fever and leukocytosis solely to the inflammatory response.
The candidate may not know the timeline of pancreatic necrosis (sterile necrosis can become infected after 2–4 weeks) and may be overly cautious about using antibiotics, leading to delayed diagnosis of infected necrosis, which has high mortality.
What to do instead
Learn the natural history of acute pancreatitis: sterile necrosis is common, but infection occurs in 20–40% and is suspected when there is clinical deterioration, persistent fever, or organ failure after the first week. Order a contrast-enhanced CT (or MRI) to look for gas in the necrosis, and consider image-guided fine-needle aspiration for culture if diagnosis is uncertain. Start broad-spectrum antibiotics with good pancreatic penetration (e.g., carbapenems) if infection is suspected, and plan for surgical or endoscopic necrosectomy if needed.
When managing a patient with acute respiratory failure who is a candidate for noninvasive ventilation (NIV), the candidate applies NIV to a patient with an altered mental status or inability to protect the airway, or fails to reassess the patient after 30–60 minutes to determine if NIV is successful.
The candidate may be eager to avoid intubation and applies NIV indiscriminately, not recognizing contraindications. They may also not know that a trial of NIV should be reassessed within 1 hour, and that failure to improve (e.g., persistent tachypnea, high CO2, or worsening pH) should prompt intubation.
What to do instead
Memorize the contraindications to NIV: inability to protect airway, excessive secretions, altered mental status (unless due to hypercapnia), hemodynamic instability, facial trauma/surgery, and high aspiration risk. Always reassess after 30–60 minutes: if respiratory rate, pH, and PaCO2 are not improving, or if the patient is fatigued, proceed to intubation. Practice with case scenarios to identify when NIV is appropriate and when to abandon it.
In a critically ill patient receiving enteral nutrition, the candidate fails to monitor for and prevent refeeding syndrome in a malnourished patient, or does not recognize the need to start feeding at a low rate and supplement electrolytes (especially phosphate, potassium, magnesium).
The candidate may not be familiar with refeeding syndrome, or may prioritize caloric goals over safety. They may also not check electrolyte levels frequently in the first 72 hours of feeding.
What to do instead
Identify high-risk patients: low BMI, unintentional weight loss, little oral intake for >5 days, low pre-albumin, or electrolyte abnormalities before feeding. In these patients, start enteral feeding at 10–20 kcal/hr, check electrolytes (phosphate, potassium, magnesium) daily for the first 3–5 days, and replace aggressively. Know that refeeding syndrome can cause cardiac and respiratory failure due to hypophosphatemia.
When asked about leadership or administration of a critical care unit, the candidate focuses only on clinical duties (e.g., rounds, protocols) and ignores key administrative responsibilities such as disaster planning, resource allocation, quality improvement, and interdisciplinary team management, leading to incomplete answers on leadership questions.
The candidate may have limited exposure to administrative aspects of critical care and may not realize that the exam tests non-clinical competencies like ICU management, patient safety, and team leadership. They may also overlook the importance of communication and conflict resolution.
What to do instead
Study the core competencies of ICU administration: staffing models, bed management, disaster preparedness, quality metrics (e.g., VAP, CLABSI, mortality), family communication, and end-of-life care. Review the roles of the intensivist as a leader, including conflict resolution, team building, and resource stewardship. Practice answering questions about how to handle ICU overcrowding, triage, and policy development.