Situation: A 72-year-old woman is admitted for elective open repair of a large abdominal wall hernia under general anesthesia tomorrow morning. She lives with her daughter, is alert and oriented, and wears glasses and dentures. The surgeon has confirmed that she can give her own consent. Although she is alert and oriented, the nurse records a baseline cognitive screening score before surgery. What is the main purpose of this baseline?

Older adults are at high risk of postoperative delirium, an acute change in attention and cognition. A documented preoperative baseline lets the team recognize a new change after surgery.

Core purpose of baseline cognitive screening

A baseline cognitive screening score is obtained before surgery because older adults are at high risk for postoperative delirium (POD), which is an acute, fluctuating disturbance in attention and cognition that develops after an operation. The defining feature of delirium is that it represents a change from the person's own preoperative level of function. Without a documented baseline, a new-onset change in attention, orientation, or executive function after surgery can be missed or mistaken for the patient's usual state, especially when family members are not immediately available to describe what is normal for her.

Key point! The baseline is a reference point for comparison, not a single diagnostic test. A low baseline score alone does not diagnose delirium; the diagnosis requires evidence of an acute change or fluctuation from that baseline after surgery.

The patient in this scenario is alert and oriented, wears glasses and dentures, and lives with her daughter. Even though she appears cognitively intact, her age of 72 years places her in a group where the incidence of postoperative delirium is elevated, particularly after major surgery under general anesthesia. Recording her preoperative cognitive performance allows the postoperative team to detect even subtle declines in attention, orientation, or processing speed that might otherwise be attributed to fatigue, pain, or medication effects.

Watch out! The baseline screening is not used to decide whether general anesthesia is safe, to select fall-prevention measures, or to calculate a sedative dose. Those are separate clinical decisions. The screening's purpose is specifically to enable later recognition of a new cognitive change.

Why a baseline matters for delirium detection

Postoperative delirium is a clinical diagnosis based on the Diagnostic and Statistical Manual of Mental Disorders (DSM-5) criteria, which require a disturbance in attention and awareness that develops acutely and tends to fluctuate, plus an additional cognitive disturbance. The key phrase is "not better explained by a preexisting neurocognitive disorder". This means the clinician must know what the patient's cognition was like before surgery to determine whether the current presentation is new or simply a continuation of preexisting impairment.

In older surgical patients, preoperative cognitive impairment is a well-established risk factor for postoperative delirium. However, many older adults have mild, undiagnosed cognitive deficits that are not obvious during a brief preoperative interview. A structured screening tool, such as the Montreal Cognitive Assessment (MoCA), can quantify performance across multiple domains, including attention, executive function, memory, language, and visuospatial ability. The preoperative score then serves as the individual's own reference point.

The study by Yan et al. ^[1] characterized preoperative domain-specific performance on the MoCA in older surgical patients and explored associations with adverse outcomes. This work highlights that cognitive screening in the preoperative period is not merely a formality; it provides a structured, quantifiable baseline that can be compared with postoperative assessments. When a patient's postoperative MoCA score drops significantly from their own preoperative score, the team has objective evidence of an acute change, which supports a diagnosis of delirium rather than assuming the patient was always like this.

Clinical application in this patient

This 72-year-old woman is scheduled for elective open repair of a large abdominal wall hernia under general anesthesia. Several factors in her presentation increase her risk for postoperative delirium: advanced age, major surgery, general anesthesia, and the physiological stress of the perioperative period. Although she is currently alert and oriented, her baseline cognitive screening score provides a personalized benchmark.

After surgery, the nurse will perform serial cognitive assessments, often using a brief delirium screening tool such as the Confusion Assessment Method (CAM) or the 4AT. These tools ask whether there is an acute change or fluctuating course in mental status, inattention, altered level of consciousness, or disorganized thinking. To answer the first question accurately—"Is there an acute change from baseline?"—the nurse must know what the baseline was. The preoperative screening score supplies that information.

The retrospective analysis by Kamimura et al. ^[3] examined pre-fracture cognitive assessment using the DASC-21 and its relationship to postoperative delirium risk in older adults undergoing hip fracture surgery. Although that study focused on a different surgical population and used an informant-based tool, the underlying principle is the same: knowing the patient's premorbid cognitive status improves the ability to recognize delirium after surgery. In acute settings, patients may not be able to report their own baseline reliably, and family members or structured preoperative assessments become essential.

Key point! The baseline cognitive score is most useful when it is documented clearly in the chart and communicated to the postoperative nursing team. A score that is recorded but not referenced during postoperative assessments has limited clinical value.

How the baseline score is used after surgery

The baseline score is not a threshold that triggers an intervention by itself. Instead, it functions as a comparator. The postoperative sequence is as follows:

Step	What happens	Role of baseline score
Preoperative	Cognitive screening (e.g., MoCA) is administered and documented	Establishes the patient's own reference level
Postoperative day 1 and beyond	Serial delirium screening (e.g., CAM, 4AT) is performed	Current performance is compared with the preoperative baseline
If a change is detected	Acute decline in attention, orientation, or executive function is noted	Supports diagnosis of delirium rather than preexisting impairment
If no change is detected	Patient remains at their own baseline	Delirium is less likely; other causes of symptoms should be considered

The prospective cohort study by Mahmoud et al. examined plasma total tau as a biomarker of postoperative delirium after major cardiac surgery. While that study focused on a blood-based marker rather than cognitive screening, it reinforces the broader principle that early identification of patients at risk for postoperative delirium requires preoperative assessment. Biomarkers and cognitive screening tools serve complementary roles: the biomarker may indicate neuronal injury, while the cognitive baseline allows the clinical team to recognize the functional consequence of that injury.

Similarly, the review by Li et al. on biomarkers of perioperative neurocognitive disorders after cardiac surgery describes a multifactorial pathogenesis involving cerebral hypoperfusion, inflammation, blood-brain barrier disruption, and host vulnerability. This mechanistic background explains why an older adult undergoing major surgery is susceptible to cognitive changes, but it does not replace the need for a clinical baseline. The baseline cognitive score is the clinical anchor that allows the team to interpret postoperative cognitive performance in the context of the individual patient.

Why the other options are incorrect

Option 2: To help decide whether general anesthesia is safe for her. The decision about anesthetic safety is made by the anesthesia team based on cardiovascular, pulmonary, renal, and hepatic function, airway assessment, and overall frailty. A cognitive screening score does not determine whether general anesthesia can be administered. A patient with a low MoCA score can still safely undergo general anesthesia, and a patient with a high score can still develop delirium.

Option 3: To select her fall-prevention measures after surgery. Fall prevention is important for all older surgical patients, but fall risk is assessed using tools such as the Morse Fall Scale or Hendrich II Fall Risk Model, which evaluate gait, mobility, medications, continence, and history of falls. The cognitive baseline score is not the primary determinant of which fall-prevention interventions are selected. Delirium itself increases fall risk, but the baseline score is used to detect delirium, not to directly choose fall precautions.

Option 4: To decide the dose of her preoperative sedative. Preoperative sedative dosing is based on age, weight, comorbidities, medication history, and the planned anesthetic technique. Cognitive screening does not provide pharmacokinetic or pharmacodynamic information that would guide sedative dosing. In fact, minimizing or avoiding preoperative sedatives, particularly benzodiazepines, is often recommended in older adults because these medications can precipitate or worsen delirium, but this decision is independent of the baseline cognitive score.

Watch out! A common error is to think that a normal baseline cognitive score means the patient will not develop delirium. This is incorrect. A normal baseline simply means the team has a clean reference point. Delirium can occur in patients with completely normal preoperative cognition, especially after major surgery with general anesthesia. The baseline score does not predict delirium; it enables its detection.

Integration with the nursing process

From a nursing process perspective, the baseline cognitive screening is part of the assessment phase. It is a preoperative data point that informs the postoperative plan of care. The nursing diagnosis of acute confusion or risk for acute confusion is supported by the presence of risk factors (advanced age, major surgery, general anesthesia) and is confirmed when the postoperative assessment shows a change from the documented baseline.

The nurse's role includes administering the baseline screening accurately, documenting the score in a location that is accessible to the postoperative team, and communicating the baseline to colleagues during handoff. When the patient returns from surgery, the nurse compares current mental status with the baseline at regular intervals, particularly during the first 48 to 72 hours when delirium risk is highest. Any acute change in attention, orientation, or level of consciousness triggers further evaluation for delirium and its underlying causes, such as pain, hypoxia, infection, electrolyte imbalance, or medication effects.

In this patient's case, her glasses and dentures are relevant to postoperative cognitive assessment. If she cannot see or hear clearly because her sensory aids are not in place, she may appear confused when she is actually experiencing sensory deprivation. Ensuring that she has her glasses and dentures after surgery is a simple but important nursing intervention that supports accurate cognitive assessment and reduces the risk of misinterpreting sensory impairment as delirium.