For the ABS Surgical Critical Care Certifying Examination, study by practicing complete decision chains across hemodynamics, ventilation, sepsis source control, renal replacement, metabolic support, and trauma. Each section below names the concepts that distinguish sound decisions from plausible mistakes, includes worked paper scenarios, and ends with a scored exercise and readiness checks. Administrative details such as dates, fees, and eligibility are published by the American Board of Surgery and are not covered here.
Classifying shock from hemodynamic data instead of gut feel
Shock categories are defined by the relationship between cardiac output and systemic vascular resistance. Reading preload, pump function, and afterload from available data turns a memorized list into a repeatable bedside classification.
Anchor the four states to their hemodynamic signatures. Hypovolemic shock pairs low preload with low cardiac output and compensatory vasoconstriction. Cardiogenic shock shows adequate or elevated filling pressures with a failing pump. Obstructive shock mimics cardiogenic findings but the problem is external: tamponade, tension pneumothorax, or massive pulmonary embolism. Distributive shock, typical of sepsis and neurogenic causes, shows reduced afterload with preserved or increased output. In every case, ask three questions in order: is the tank full, is the pump working, are the pipes dilated.
Use lactate and central venous oxygen saturation as cross-checks rather than as classifiers. A mixed picture is common after major surgery: a septic patient may also be hypovolemic from third-spacing, so the numbers reflect overlapping components. The disciplined move is to identify which component is driving the trajectory right now, correct it, and reassess rather than averaging the picture into one label. A single elevated filling pressure, taken alone, supports almost no conclusion.
Compare the four states side by side and practice filling this table from a blank version until the discriminating variables are automatic:
| Shock state | Preload | Cardiac output | Systemic vascular resistance | Typical surgical triggers | First-line move |
|---|---|---|---|---|---|
| Hypovolemic (hemorrhage) | Low | Low | High | Bleeding, burns, bowel losses | Volume and blood; stop the source |
| Cardiogenic | High | Low | High | Perioperative infarction, arrhythmia | Inotropic support; treat the cause |
| Obstructive | High | Low | High | Tamponade, tension pneumothorax, PE | Relieve the obstruction directly |
| Distributive (septic, neurogenic) | Variable | Normal or high | Low | Sepsis, spinal cord injury | Volume, vasopressors, source control |
Ventilator escalation: decide which pressure you are treating
Plateau pressure and driving pressure describe different hazards. Adjusting tidal volume, rate, or PEEP without naming which pressure you are targeting is where ventilator decisions go wrong.
Plateau pressure reflects alveolar pressure at end-inspiration and signals overdistension risk; driving pressure, the plateau minus PEEP, reflects the cyclic strain of each breath and tracks lung injury in acute respiratory distress syndrome. Low tidal volume ventilation with permissive hypercapnia is the framework that reconciles gas-exchange goals with these limits. The practical habit: before any setting change, state the number you are protecting and the change that protects it.
Worked scenario: a 70 kg patient with ARDS is on 6 mL/kg tidal volume, PEEP 15, plateau pressure 34 cmH2O, driving pressure 19 cmH2O, pH 7.18, PaCO2 62 mmHg. The tempting mistake is raising tidal volume to 8 mL/kg to blow off carbon dioxide. The better decision is to accept permissive hypercapnia, increase respiratory rate within a safe limit, deepen sedation as appropriate, and reassess PEEP positioning, because the elevated plateau and driving pressure, not the acidemia, define the injury risk. Lowering plateau pressure at the cost of gas exchange is a deliberate trade, not a failure.
Sepsis in the surgical ICU: why source control outranks escalation
Antibiotics address the microbial component; undrained pus, necrotic tissue, or a leaking anastomosis keeps the derangement progressing regardless of regimen. Sequencing source control appropriately is the defining surgical critical care decision.
Keep three named concepts distinct. Time-to-effective antibiotics governs early outcomes and justifies broad initial coverage. Source control means physically resolving the driving anatomy, whether by drainage, debridement, or diversion, and it is categorically different from antimicrobial therapy. De-escalation then narrows coverage once cultures and clinical response define the problem. A surgical ICU patient whose sepsis persists despite appropriate antibiotics should prompt a search for inadequate source control, not a reflex to add agents.
Mini-scenario: a postoperative patient on two broad-spectrum agents for four days has a rising lactate and new vasopressor requirements; imaging shows an undrained collection. The plausible mistake is ordering a third antibiotic or switching classes. The better decision is urgent drainage, percutaneous or operative as anatomy dictates, because no regimen sterilizes an undrained abscess, and continued escalation adds toxicity and resistance pressure while the physiologic problem worsens. Antibiotics and source control are sequenced partners, not substitutes.
Renal replacement: clinical triggers, not a creatinine number
The classic replacement indications are clinical states: refractory acidemia, symptomatic uremia, refractory fluid overload, and certain intoxications. Treating a single laboratory value as a trigger is a category error worth drilling out.
Separate the staging of acute kidney injury from the decision to start replacement therapy. Staging describes severity and prognosis; the replacement decision asks whether dialysis solves a problem that other measures cannot. In a surgical ICU patient receiving ongoing resuscitation, fluid overload that prevents ventilation or drug delivery is itself an indication, even when urine output persists. Waiting for an arbitrary urea or creatinine threshold in that setting delays a therapy that addresses the immediate physiologic threat.
Modality choice then follows hemodynamics and logistics. Continuous renal replacement therapy suits patients who cannot tolerate rapid volume and solute shifts, and it allows steady fluid management during pressor support. Intermittent hemodialysis clears solute faster and suits more stable patients or time-constrained schedules. Anticoagulation needs, nursing infrastructure, and the plan for concurrent procedures all shape the choice, so practice justifying the modality from the patient's hemodynamic picture rather than from habit.
Metabolic support: route, early targets, and refeeding risk
Enteral nutrition is preferred whenever the gut is usable. The decisions that matter are early initiation within tolerance, accepting permissive underfeeding early, and identifying refeeding risk before hypophosphatemia appears.
In early sepsis and ARDS, aggressive caloric delivery on day one is not the goal; trophic feeding that maintains gut integrity while the patient is resuscitated is a defensible target, with advancement as tolerance allows. Reserve parenteral nutrition for patients in whom the enteral route is unavailable or unsafe, such as those with inaccessible anatomy or uncorrected shock precluding gut perfusion. The decision skill is naming why you are on the route you chose and what would move the patient back to enteral support.
Refeeding syndrome deserves prospective screening, not retrospective recognition. Patients with chronic alcohol use disorder, prolonged starvation, or major weight loss shift rapidly to carbohydrate metabolism; insulin drives phosphate, potassium, and magnesium intracellularly, and the resulting hypophosphatemia impairs respiratory and cardiac function. For identified high-risk patients, start at a reduced rate, check phosphate within the first day or two, and replace aggressively. A ventilated surgical patient who suddenly weakens after feeding begins is a classic presentation of this preventable sequence.
Damage control: deciding when physiology overrides anatomy
The lethal triad of hypothermia, acidosis, and coagulopathy defines when definitive repair must be deferred. Damage control is a planned sequence, not an improvised fallback, and the trigger should be recognizable mid-operation.
Understand the physiology that makes the triad lethal: coagulation enzyme function deteriorates as temperature and pH fall, while ongoing bleeding consumes factors, so each component accelerates the others. Recognizing the triad in a Laparotomy, before the oozing becomes uncontrollable, is the trainable skill. The structured response is to control hemorrhage and contamination, pack, close temporarily, and move resuscitation to the ICU with a scheduled re-exploration.
Worked scenario: during a trauma laparotomy for a splenic and hepatic injury, the patient is 34.2 degrees Celsius, pH 7.14, INR 2.3, with diffuse ooze despite packing. The colon has a devascularizing injury. The plausible mistake is completing a definitive anastomosis and chasing every bleeding point in a physiologically worsening patient. The better decision is rapid control of spillage, temporary closure, and a planned second look after rewarming, correction of acidosis, and factor replacement in the ICU, because definitive reconstruction in the lethal triad trades a controllable problem for an uncontrollable one.
A scored case-drill exercise and readiness checks
Build review around chart-style cases rather than isolated facts, and score yourself against explicit observations so weaknesses map to specific content areas instead of to vague impressions of readiness.
The exercise: write or assemble five paper cases, one per major topic, each listing vital signs, labs, ventilator settings, and the clinical context. For each case, produce exactly three outputs: a shock or state classification naming the discriminating variable, one next management move, and the named principle that constrains the move. Expected observations: classifications that cite output and resistance relationships rather than a trigger word; management moves that change one variable with a stated reason; and principles drawn from this guide's sections. A classification that says septic without addressing a concurrent hypovolemic component, or a ventilator change with no target pressure named, marks the gap to revisit.
An adaptable eight-week sequence: weeks one and two, hemodynamics and ventilation, drawing the shock table and computing driving pressure from every vent scenario you encounter; weeks three and four, sepsis sequencing and renal replacement, drilling the four replacement indications and modality justification; week five, nutrition route and refeeding decisions; week six, trauma and damage control triggers; weeks seven and eight, mixed case drills scored against the rubric above. Treat the rubric as a learning milestone, not a prediction of any outcome.
Readiness checks to run before you conclude review:
- From a blank four-column shock table, you can place a new case and name the discriminating variable within a minute of self-timed practice.
- Given a plateau pressure and PEEP, you compute driving pressure and state which ventilator adjustment it permits or forbids.
- You can list the four classic renal replacement indications without notes and explain why a creatinine threshold alone is not among them.
- You can narrate the lethal triad and the damage control sequence from memory, including why anastomosis was deferred in the worked scenario.
- You can score your own case drill honestly against the rubric and identify at least one topic area to repeat.
References and further reading
Use these references to explore the concepts and check the latest information from the relevant organizations.