The Partners Human Research Committee / Institutional Review Board approved this prospective observational cohort study (# 2016P000012) that was also registered in clinicaltrials.gov (# NCT02922634 ). This is a primary analysis of data. Between April 17, 2017 and October 9, 2018, study staff members recruited patients ≥ 70 years of age who were scheduled for elective spine surgery at the Brigham and Women’s Hospital and were expected to have an inpatient admission following their procedure. We selected this patient population because spine surgery is the 3rd most common surgical procedure in older persons18 (link) and our prior work showed that nearly 20% of this surgical demographic develops delirium postoperatively.19 This type of surgery is relatively homogeneous and grouped within tiers of invasiveness. Eligible patients were identified by review of the preoperative evaluation schedule in the electronic medical record. Exclusion criteria included planned outpatient surgery; history of overt stroke or brain tumor; uncorrected vision or hearing impairment (unable to see pictures or read or hear instructions); limited use of the dominant hand (limited ability to draw); and/or inability to speak, read or understand English.
We planned to prospectively enroll a total of 229 patients in the study based on a power calculation of the number of patients required for 85% power to detect a 50% difference in POD (primary outcome) at the P = 0.05 level between patients with and without a positive cognitive or frailty screen, assuming a baseline incidence of POD of 15% and approximately a 10% loss to follow up. After obtaining written informed consent, patients were screened using the FRAIL scale to identify frailty and the Mini-Cog and Animal Verbal Fluency tests to evaluate cognitive performance in the Brigham and Women’s Hospital Weiner Center for Preoperative Evaluation on the day of the patient’s scheduled preoperative evaluation which takes place no more than 4 weeks prior to surgery.9 (link),10 The FRAIL scale8 (link),16 (link) is a simple 5 point screen that measures Fatigue, Resistance (ability to climb one flight of stairs), Ambulation (ability to walk one block), Illness (greater than 5 past or current diagnoses) and weight loss (>5%). Each positive response within a domain scores 1 point, yielding a maximum score of 5. Higher scores indicate increased frailty; as described by others, we defined frail as a score of 3 or above and pre-frail as a scores of 1–2. We selected the Mini-Cog and Animal Verbal Fluency tests for cognition because they are brief, have been used previously in older surgical populations, and have been shown to be associated with the development of POD.9 (link)–11 (link),15 (link) The Mini-Cog is a simple and validated cognitive screening tool that includes a three-item recall of memory and a clock drawing component that is graded on a 5-point scale, where a score of 2 or less is considered probable cognitive impairment. Animal Verbal Fluency is a similarly simple and brief cognitive screening tool where the subject is asked to name as many animals as possible in 60 seconds and a score of 16 or less has previously been demonstrated to be associated with POD.11 (link),20 (link) For the primary analysis both Mini-Cog and Animal Verbal Fluency scores were analyzed linearly. We categorized the complexity and invasiveness of the surgical procedure according to an established 4-tier rating system: microdiscectomy is a tier 1 procedure; lumbar laminectomy, anterior cervical procedures or minimally invasive fusions are tier 2; lumbar fusion, trauma, or posterior cervical fusion procedures are tier 3; and tumor, infection, deformity, or combined anterior and posterior cervical procedures are tier 4.21 (link) For the analysis, we grouped tiers 1 and 2 (less complex) and 3 and 4 (more complex) together as there were few patients in categories 1 or 4. Other demographic and medical information such as age, sex, body mass index, highest level of education, American Society of Anesthesiologists (ASA) functional status, Metabolic Equivalent of Task (METS), total number of medications, preoperative use of opioids, alcohol consumption, and past medical history of depression and psychiatric comorbidities were obtained from the medical record.
Incidence of POD was the primary outcome. POD was identified both by chart review using published criteria and by direct, independent assessment with the Confusion Assessment Method (CAM).10 ,22 (link),23 (link) The CAM was administered once per day on postoperative days 1 to 3, or until discharge if the patient was discharged early, by an investigator blinded to chart review information. We used both methods because they are complementary. Delirium typically waxes and wanes so it can be missed if the CAM is administered during the waning period. Conversely, chart review reflects events over an entire day but may miss hypoactive POD, the most common form.1 (link) The secondary outcomes included all in-hospital cardiopulmonary (myocardial infarction, congestive heart failure, cardiac arrest, new onset arrhythmia, pulmonary embolism, reintubation and deep venous thrombosis), infectious (wound infections, pneumonia, sepsis and urinary tract infection), renal (acute renal injury), or cerebrovascular (stroke and transient ischemic accident) complications, discharge to place other than home and hospital length of stay.
Study data were managed using Research Electronic Data Capture (REDCap) hosted at Partners Healthcare.24 (link)
We planned to prospectively enroll a total of 229 patients in the study based on a power calculation of the number of patients required for 85% power to detect a 50% difference in POD (primary outcome) at the P = 0.05 level between patients with and without a positive cognitive or frailty screen, assuming a baseline incidence of POD of 15% and approximately a 10% loss to follow up. After obtaining written informed consent, patients were screened using the FRAIL scale to identify frailty and the Mini-Cog and Animal Verbal Fluency tests to evaluate cognitive performance in the Brigham and Women’s Hospital Weiner Center for Preoperative Evaluation on the day of the patient’s scheduled preoperative evaluation which takes place no more than 4 weeks prior to surgery.9 (link),10 The FRAIL scale8 (link),16 (link) is a simple 5 point screen that measures Fatigue, Resistance (ability to climb one flight of stairs), Ambulation (ability to walk one block), Illness (greater than 5 past or current diagnoses) and weight loss (>5%). Each positive response within a domain scores 1 point, yielding a maximum score of 5. Higher scores indicate increased frailty; as described by others, we defined frail as a score of 3 or above and pre-frail as a scores of 1–2. We selected the Mini-Cog and Animal Verbal Fluency tests for cognition because they are brief, have been used previously in older surgical populations, and have been shown to be associated with the development of POD.9 (link)–11 (link),15 (link) The Mini-Cog is a simple and validated cognitive screening tool that includes a three-item recall of memory and a clock drawing component that is graded on a 5-point scale, where a score of 2 or less is considered probable cognitive impairment. Animal Verbal Fluency is a similarly simple and brief cognitive screening tool where the subject is asked to name as many animals as possible in 60 seconds and a score of 16 or less has previously been demonstrated to be associated with POD.11 (link),20 (link) For the primary analysis both Mini-Cog and Animal Verbal Fluency scores were analyzed linearly. We categorized the complexity and invasiveness of the surgical procedure according to an established 4-tier rating system: microdiscectomy is a tier 1 procedure; lumbar laminectomy, anterior cervical procedures or minimally invasive fusions are tier 2; lumbar fusion, trauma, or posterior cervical fusion procedures are tier 3; and tumor, infection, deformity, or combined anterior and posterior cervical procedures are tier 4.21 (link) For the analysis, we grouped tiers 1 and 2 (less complex) and 3 and 4 (more complex) together as there were few patients in categories 1 or 4. Other demographic and medical information such as age, sex, body mass index, highest level of education, American Society of Anesthesiologists (ASA) functional status, Metabolic Equivalent of Task (METS), total number of medications, preoperative use of opioids, alcohol consumption, and past medical history of depression and psychiatric comorbidities were obtained from the medical record.
Incidence of POD was the primary outcome. POD was identified both by chart review using published criteria and by direct, independent assessment with the Confusion Assessment Method (CAM).10 ,22 (link),23 (link) The CAM was administered once per day on postoperative days 1 to 3, or until discharge if the patient was discharged early, by an investigator blinded to chart review information. We used both methods because they are complementary. Delirium typically waxes and wanes so it can be missed if the CAM is administered during the waning period. Conversely, chart review reflects events over an entire day but may miss hypoactive POD, the most common form.1 (link) The secondary outcomes included all in-hospital cardiopulmonary (myocardial infarction, congestive heart failure, cardiac arrest, new onset arrhythmia, pulmonary embolism, reintubation and deep venous thrombosis), infectious (wound infections, pneumonia, sepsis and urinary tract infection), renal (acute renal injury), or cerebrovascular (stroke and transient ischemic accident) complications, discharge to place other than home and hospital length of stay.
Study data were managed using Research Electronic Data Capture (REDCap) hosted at Partners Healthcare.24 (link)
