Delirium after Emergency/Elective Open and Endovascular Aortoiliac Surgery at a Surgical Ward with a High-standard Delirium Care Protocol

Abstract

Delirium is a common problem in elderly patients undergoing surgery. Standard delirium care is not available at all surgical wards. We determined the incidence, risk factors, and outcomes of postoperative delirium among patients undergoing elective/emergency aortoiliac surgery at a surgical ward with high-standard delirium care. A prospective descriptive survey in 107 patients was conducted. High-standard delirium care was given to patients above age 65, consisting of an extended focus on risk factors and intensive screening. The Delirium Observation Scale was used as a screening instrument for delirium. Patients were classified as having delirium if they met the DSM-IV criteria. The overall incidence of delirium was 23%. The incidence was 14% after elective surgery. Delirium occurred in 59% after emergency surgery and more often after open than after endovascular aneurysm repair (p < .01). Delirium was associated with age (p < .01) and emergency surgery (p = .01) and is an important and frequent complication after aortoiliac surgery.

Keywords

delirium incidence outcome risk factor vascular surgery

Delirium is characterized by an acute and fluctuating decline in attention and cognition.¹ It is a common and serious complication, especially in elderly patients undergoing surgery.^2–5 Delirium can be caused by many different interacting factors depending on the vulnerability of the patient.⁶ Known risk factors for delirium are advanced age, male gender, dementia, poor functional status, medical illness, and use of anticholinergic medication.^7–10

Delirium is not an innocent and temporary change in mental status. Patients with delirium are at risk for an increased number of complications, increased length of hospital stay, higher mortality rates, poorer functional and mental recovery, and higher medical costs. However, it is always hard to tell whether a patient had pneumonia first and then became delirious or that a patient was already delirious and then took more superficial breaths and developed pneumonia.

The incidence of delirium varies in the literature, partly owing to the level of delirium care given on the wards. At a surgical ward with high-standard delirium care with trained professionals, delirium is recognized more often.¹¹ Most studies for delirium at a surgical ward were performed in patients after orthopedic or cardiac surgery.^12–18 Only a few studies evaluated the incidence of and risk factors for delirium after vascular and abdominal aortic surgery.^19–22 The incidence of delirium after vascular surgery varies between 29 and 39%, including surgery for peripheral vascular disease.²³ No data exist on delirium after endovascular aneurysm repair (EVAR).

At our surgical ward, high-standard delirium care has routinely been provided since 2004. No data are available on the incidence of and risk factors for delirium after aortoiliac surgery at surgical wards with high-standard delirium care.

The objective of this study was to determine the incidence, risk factors, and outcomes of postoperative delirium among patients undergoing elective or emergency open or endovascular aortoiliac surgery at a (vascular) surgical ward with high-standard delirium care. Furthermore, we compared the outcomes after open and endovascular surgery.

Materials and Methods

Patients

All patients undergoing aortoiliac surgery admitted to the surgical department of the Jeroen Bosch Hospital, a suburban teaching hospital, between July 2006 and July 2008 were included in a prospective database. The surgical procedures consisted of elective and acute thromboendarterectomies of the distal aorta and placement of aortoaortic, aorta bifurcation, or uni-iliac prostheses by open or endovascular methods. Patients suffering from Alzheimer disease or dementia were excluded.

At the surgical department of the Jeroen Bosch Hospital, high-standard delirium care has been given to patients aged 65 years and older since 2004, consisting of conservative measurements such as focusing on risk factors such as impaired hearing or vision by putting on hearing aids and glasses. Photographs of relatives are routinely placed beside beds and calendars are present in every room to prevent disorientation and to install familiar key points near all patients. It is important to state that we did not use preoperative pharmacologic treatment to prevent postoperative delirium in this series of patients.

Because delirium develops in a short period of time and fluctuates during the day, the validated 13-item Delirium Observation Scale (DOS) of verbal and nonverbal behavior was used three times a day (each shift) by trained nursing staff to identify delirium, whether or not patients showed delirious symptoms.^24,25 A DOS score < 3 means that a patient is probably not delirious; a DOS score ≥ 3 indicates that the patient is probably delirious. If a patient scored ≥ 3 on the DOS, the geriatric consultation team was consulted the same day to observe the patient. Patients were classified as having delirium by the geriatrician if they met the Diagnostic and Statistical Manual of Mental Disorders, 4th Edition (DSM IV), criteria and were then observed daily and pharmacologically treated by a geriatric consulting team consisting of geriatricians and trained geriatric nurses. Daily advice was given to the surgical department by the geriatric consultation team concerning the medication and the severity and prognosis of delirium in the individual patient. Haloperidol was the standard medical treatment in the standardized hospital protocol.²⁶

Methods

Surgical, anesthetic, and geriatric files were reviewed for prospective collected data such as patient characteristics and pre-, intra-, and postoperative data, approved by the patient and the ethical board. Preoperative factors included demographic data, length, weight, medical history, number of medications, America Society of Anesthesiologists (ASA) classification, preoperative blood pressure, heart rate, and laboratory data. The Charlson Comorbidity Score (CCS) and Index (CCI) were calculated from the medical history, with higher scores indicating greater comorbidity. The CCS is known to relate inversely to outcome.²⁷ Unfortunately, there was no preoperative DOS score or cognitive screening test to evaluate because we included elective and emergent vascular surgery patients.

Intraoperative data were type of anesthesia, type of surgery, length of anesthesia, length of surgery, blood loss, infusion volume, transfusion volume, blood pressure, heart rate, and laboratory data. All general anesthesia patients were given the same general anesthetic agent.

Postoperative data were occurrence of delirium, length of intensive care unit (ICU) and hospital stay, laboratory data, number of postoperative complications, and mortality.

If patients developed delirium, routine investigations for the physical causes underlying the delirium were performed (laboratory and urinary investigations and, if indicated, chest radiography).

Statistical Methods

SPSS for Windows version 15.0 (SPSS Inc, Chicago, IL) was used to evaluate our data. Differences between delirious and nondelirious patients were analyzed by Student t-tests for continuous data and chi-square or Fisher exact tests for dichotomous data. Univariate logistic regression analysis was performed when the differences between the groups were significantly different (p < .10). The cutoff points were based on the available literature or the means of the different variables in this population. A multivariate step forward logistic regression analysis followed with preoperative and perioperative data. We used a probability for stepwise entry of p < .05 and a probability of removal of p < .10. The final results were considered statistically significant if p was ≤ .05.

Results

We identified 110 patients who met the eligibility criteria. Thirty-three patients underwent EVAR (2 emergency, 31 elective), and 77 patients underwent open surgery (22 emergency, 55 elective). Three patients were excluded because of a lack of data. The mortality rate for all patients was 7.3% (n = 8 of 110); it was 2.4% (n = 2 of 85) for elective surgery and 27.3% (n = 6 of 22) for emergency surgery. The mortality rate was higher in patients developing delirium compared to patients who did not (p = .03).

Table 1 shows the patient characteristics and perioperative data of the delirious and nondelirious patients. The overall incidence of delirium was 23% (25 of 107); it was 14% (12 of 85) following elective aortoiliac surgery and 59% (13 of 22) following emergency surgery. In this series, no patients were found to be delirious after elective EVAR. Delirium started most often on day 1 after surgery and DOS scores were highest on days 2 and 3 and then gradually reduced. Delirium lasted for 1 to 3 days in 9 patients and for more than 3 days in 16 patients (range 4–29 days). In the > 3-day delirium group, patients scored significantly and consistently higher on the DOS group compared to the patient group with a 1- to 3-day delirium (p < .05).

Table 1.

Patient Characteristics and Perioperative Data of Delirious and Nondelirious Patients

	Postoperative Delirium	No Postoperative Delirium	p
Total (n = 107) (%)	25 (23)	82 (77)
Patient characteristics and preoperative data
Gender
Male (%)	18 (72)	64 (78)	.53
Female (%)	7 (28)	18 (22)
Age (yr)	73.4 ± 6.4	67.8 ± 9.7	.01
BMI	26.8 ± 3.6	25.4 ± 3.9	.22
ASA	3.1 ± 0.7	2.7 ± 0.6	.01
Medical history
Number of diagnosis	5.0 ± 2.3	4.5 ± 2.1	.32
Charlson Comorbidity Score	1.2 ± 1.1	1.1 ± 1.0	.64
Medications (n)	4.5 ± 2.3	4.8 ± 2.4	.59
Blood pressure (mm Hg)
Systolic	131.8 ± 23.6	141.2 ± 25.0	.10
Diastolic	71.7 ± 15.4	77.5 ± 10.3	.03
Heart rate (1/min)	75.6 ± 15.1	70.9 ± 13.2	.14
Laboratory data
Hemoglobin (mmol/L)	8.0 ± 1.7	8.4 ± 1.0	.20
Urea (mmol/L)	8.9 ± 8.0	6.4 ± 2.9	.02
Creatinine (μmol/L)	120.8 ± 38.4	108.7 ± 71.3	.42
Intraoperative data
Type of anesthesia
General (%)	11 (34)	21 (66)	.08
Concurrent general and epidural (%)	12 (19)	51 (81)	.21
Other (%)	2 (17)	10 (83)	.43
Surgery			< .01
Emergency	13 (59)	9 (41)
Elective	12 (14)	73 (86)
Type of pathology
Aortoiliac occlusive disease (%)	0 (0)	17 (100)	.01
Infrarenal abdominal aortic aneurysm (%)	18 (25)	53 (75)	.50
Juxta-/suprarenal aortic aneurysm (%)	6 (67)	3 (33)	.01
Other (%)	1 (10)	9 (90)	.45
Type of surgery			.01
Laparotomy	23 (31)	51 (69)
Endovascular	2 (6)	31 (94)
Length of anesthesia (min)	288 ± 98	250 ± 88	.08
Length of surgery (min)	229 ± 87	186 ± 70	.01
Blood loss (mL)	2,630 ± 1,915	1,283 ± 1,144	< .01
Infusion volume (mL)	7,799 ± 2,859	5,246 ± 3,209	< .01
Transfusion (mL)	1,882 ± 1,682	456 ± 841	< .01
Blood pressure, lowest during surgery (mm Hg)
Systolic	92 ± 15	101 ± 21	.05
Diastolic	44 ± 8	48 ± 11	.08
Heart rate during surgery (1/min)
Highest	90 ± 20	79 ± 20	.01
Lowest	62 ± 12	58 ± 11	.08
Hemoglobin (mmol/L)	5.3 ± 1.1	6.0 ± 1.2	.02
Postoperative data
Length of ICU stay (d)	6.5 ± 6.7	1.5 ± 3.4	< .01
Length of hospital stay (d)	26.3 ± 17.1	9.4 ± 7.4	< .01
Laboratory data
Hemoglobin* (mmol/L)	6.6 ± 1.0	6.7 ± 0.9	.60
Urea^† (mmol/L)	9.4 ± 4.9	5.9 ± 3.0	< .01
Creatinine^† (μmol/L)	121.6 ± 56.8	109 ± 89	.52
Complications (n)	3.0 ± 1.5	0.7 1.3	< .01
Mortality (n) (%)	3 (12)	2 (2)	.03

ASA = American Society of Anesthesiologists; BMI = body mass index; ICU = intensive care unit.

*First postoperative day.

^†At discharge.

Data are expressed as number (%) or mean ± SD.

Compared to nondelirius patients, the delirious patients were significantly older (p = .01) and had higher ASA scores (p = .01), lower diastolic blood pressure (p = .03), and a higher concentration of urea preoperatively (p = .02). Delirious patients underwent longer operations (p = .01) and more often showed signs of hemodynamic instability, more blood loss (p < .01), more infusion volume (p < .01), and more transfusion volume (p < .01). Probably, this resulted in a significantly higher heart rate (p = .01) and lower hemoglobin during surgery (p = .02). Type of anesthesia, length of ventilator requirements, and use of psychoactive medication were not significant risk factors.

Delirium occurred more often after laparotomy than after an EVAR procedure (p = .01). Postoperatively, delirious patients had a longer ICU stay (p < .01) and total length of hospital stay (p < .01). Delirious patients had a higher level of urea at discharge (p < .01), developed more complications (p < .01), and had a longer total length of hospital stay (p < .01).

Table 2 shows the logistic regression analyses. Univariate analysis confirmed the above-mentioned risk factors for delirium, except for the lower preoperative diastolic blood pressure (p = .06). After multivariate analysis, the relative risk factors for delirium were advanced age (OR 7.7; 95% CI 1.9–30.4; p < .01) and emergency surgery (OR 5.3; 95% CI 1.3–21.2; p = .01).

Table 2.

Univariate and Multivariate Analysis

	Univariate Analysis		Multivariate Analysis
	OR (95% CI)	p	OR (95% CI)	p
Patient characteristics and preoperative data
Age ≥ 70 yr	3.6 (1.4–9.6)	.01	7.7 (1.9-30.4)	< .01
ASA ≥ 3	3.7 (1.2–11.8)	.03	*
Blood pressure (mm Hg)
Systolic ≤ 130	1.2 (0.5–2.9)	.90	*
Diastolic (≤ 75 vs > 75)	2.2 (0.9–5.6)	.06	*
Laboratory data
Urea ≥ 7.0 mmol/L	2.8 (1.1–7.2)	.03	*
Intraoperative data
Surgery
Emergency	8.8 (3.1–25.0)	< .01	5.3 (1.3-21.2)	.01
Elective (reference)
Type of surgery
Laparotomy	7.0 (1.5–31.7)	.01	*
Endovascular (reference)
Length of anesthesia (≥ 250 min)	2.6 (1.0–7.2)	.06	*
Length of surgery (≥ 200 min)	2.9 (1.1–7.6)	.03	*
Blood loss (≥ 1,500 mL)	4.4 (1.6–12.0)	< .01	*
Infusion (> 6,000 mL)	4.0 (1.5–10.7)	.01	*
Transfusion (≥ 900 mL)	7.2 (2.6–20.0)	< .01	*
Heart rate			*
Highest > 80/min)	4.1 (1.6–10.7)	.01
Lowest < 60/min vs ≥ 60/min)	0.5 (0.2–1.2)		*
Laboratory data: hemoglobin (< 5.5 mmol/L)	2.5 (1.0–6.6)	.06	*
Postoperative data
Length of ICU stay (d)	1.2 (1.1–1.4)	< .01
Length of hospital stay (d)	1.1 (1.1–1.2)	< .01
Complications	2.5 (1.7–3.6)	< .01
Urea ≥ 7.0 mmol/L (at discharge)	5.3 (1.9–14.6)	< .01

ICU = intensive care unit.

*Parameter not in the final model after step forward analysis.

Table 3 represents the patient characteristics and perioperative data in elective aortoiliac surgery. Again, we found that delirium seemed to be associated with hemodynamic instability; patients developing delirium had more blood loss (p < .01) and needed more infusion (p < .01) and transfusion volume (p < .01) than patients who did not develop delirium.

Table 3.

Patient Characteristics and Perioperative Data in Elective Aortoiliac Surgery

	Postoperative Delirium	No Postoperative Delirium	p
Total (n = 85) (%)	12 (14)	73 (86)
Patient characteristics and preoperative data
Gender
Male (%)	8 (67)	55 (75)	.50
Female (%)	4 (33)	18 (25)
Age (yr)	72.3 (68.6–75.9)	68.6 (66.3–70.8)	.89
BMI	26.6 (24.0–29.3)	25.5 (24.6–26.4)	.27
ASA	2.8 (2.6–3.1)	2.5 (2.4–2.6)	.07
Medical history
Number of diagnosis	5.6 (3.9–7.3)	4.5 (4.0–5.0)	.80
Charlson Comorbidity Score	1.3 (0.5–2.0)	1.0 (0.7–1.2)	.55
Medications (n)	5.9 (4.7–7.1)	4.9 (4.4–5.4)	.22
Blood pressure (mm Hg)
Systolic	140.6 (132.0–149.3)	139.6 (134.5–144.7)	.22
Diastolic	77.5 (68.9–86.0)	77.4 (75.2–79.7)	.81
Heart rate (1/min)	68.7 (62.3–75.2)	69.4 (66.4–72.5)	.31
Laboratory data
Hemoglobin (mmol/L)	9.0 (8.3–9.6)	8.4 (8.2–8.6)	.41
Urea (mmol/L)	6.9 (5.2-8.6)	6.2 (5.7–6.8)	.27
Creatinine (μmol/L)	102.0 (89.5–114.5)	99.1 (94.0–104.2)	.55
Intraoperative data
Type of anesthesia
General (%)	1 (8)	12 (92)	.42
Concurrent general and epidural (%)	9 (15)	51 (85)	.51
Other (%)	2 (17)	10 (83)	.54
Type of pathology
Aortoiliac occlusive disease (%)	0 (0)	17 (100)	.11
Infrarenal abdominal aortic aneurysm (%)	7 (13)	46 (87)	.76
Juxta-/suprarenal aortic aneurysm (%)	5 (71)	2 (29)	< .01
Other (%)	0 (0)	8 (100)	.59
Type of surgery
Laparotomy	12 (22)	42 (78)	< .01
Endovascular	0 (0)	31 (100)
Length of anesthesia (min)	320.7 (248.6–392.6)	253.2 (233.5–272.9)	.06
Length of surgery (min)	255.1 (184.9–325.3)	189.5 (172.3–206.7)	.40
Blood loss (mL)	2,661 (1,328–3,993)	1,180 (939–1,421)	< .01
Infusion volume (mL)	8,431 (5,932-10,930)	5,139 (4,367–5,911)	< .01
Transfusion (mL)	1,276 (297–2,255)	337 (205–469)	< .01
Blood pressure, lowest during surgery (mm Hg)
Systolic	94 (86–101)	102 (97–107)	.99
Diastolic	44 (38–49)	48 (46–51)	1.0
Heart rate during surgery (1/min)
Highest	82 (67–96)	76 (72–80)	.39
Lowest	55 (50–61)	56 (54–59)	.74
Laboratory data
Hemoglobin (mmol/L)	5.8 (5.2–6.4)	6.1 (5.7–6.5)	.94
Postoperative data
Length of ICU stay (d)	4.8 (0.6–9.0)	2.1 (0.7–3.4)	< .01
Length of hospital stay (d)	24.8 (12.8–36.9)	8.8 (7.4–10.3)	< .01
Laboratory data
Hemoglobin* (mmol/L)	7.2 (6.5–7.8)	6.7 (6.4–7.0)	.28
Urea^† (mmol/L)	7.9 (5.0–10.9)	5.7 (5.0–6.4)	.83
Creatinine^† (μmol/L)	119.6 (83.4–155.8)	98.1 (89.3–106.9)	.73
Complications (n)	3.1 (2.0–4.2)	0.7 (0.4–0.9)	< .01
Mortality (n) (%)	0 (0)	2 (3)	.59

ASA = American Society of Anesthesiologists; BMI = body mass index; ICU = intensive care unit.

*First postoperative day.

^†At discharge.

Data are expressed as number (%) or mean ± SD.

Laparotomy (p < .01) and juxta-/suprarenal aortic aneurysms (p < .01) were significant risk factors for developing delirium following elective surgery. Once again, we found that delirious patients had a longer ICU stay (p < .01) and total length of hospital stay (p < .01). Age was not a significant risk factor in the elective surgery group. Fortunately, the mortality rate in our series was too low to determine the effect of delirium on mortality.

Univariate analysis of the elective patient group shows that length of anesthesia over 250 minutes (p = .04) and laparotomy (p < .01) are both risk factors for delirium. Delirious patients in the elective surgery group more often needed over 6 L of infusion volume (p = .03) and more than 900 mL of transfusion volume (p < .01) than the nondelirious patients. In the elective EVAR group, no patient developed delirium.

The average age of patients undergoing EVAR versus patients undergoing an open procedure was 74.4 years (95% CI 72.0–74.4) and 67.3 years (95% CI 65.1–69.5), respectively (p = .001).

Despite an incidence of delirium of 0% versus 14% after elective EVAR or open surgery, open surgery could not be designated as a significant risk factor owing to limitations in techniques for statistical analysis. Because not one patient in the elective endovascular EVAR group developed delirium, it is not possible to calculate a tangible odds ratio for the elective endovascular surgery group (endovascular vs open).

After multivariate analysis, the only relative risk factor for delirium was ASA score ≥ 3 (OR 8.7; 95% CI 1.0–78.2; p = .05) (Table 4).

Table 4.

Univariate and Multivariate Analysis in Elective Surgery

	Univariate Analysis		Multivariate Analysis
	OR (95% CI)	p	OR (95% CI)	p
Patient characteristics and preoperative data
Age ≥ 70 yr	2.4 (0.7–8.8)	.18	*
ASA ≥ 3	4.1(0.8–20.5)	.08	8.7 (1.0–78.2)	.05
Intraoperative data
Length of anesthesia (> 250 min)	9.8 (1.2–81.7)	.04	*
Type of surgery
Laparotomy	†	< .01	0.000	.99
Endovascular (reference)
Blood loss (≥ 1,500 mL)	3.9 (1.0–14.7)	.05	*
Infusion (> 6,000 mL)	4.8 (1.2–19.3)	.03	*
Transfusion (≥ 900 mL)	6.8 (1.6–28.1)	< .01	3.6 (0.8–17.0)	.10
Postoperative data
Length of ICU stay (d)	1.2 (1.0–1.3)	.02
Length of hospital stay (d)	1.1 (1.1–1.2)	< .01
Complications (n)	2.3 (1.5–3.6)	< .01

ASA = American Society of Anesthesiologists; ICU = intensive care unit.

*Parameter not in the final model after step forward analysis.

^†Because not one patient developed a delirium in the elective endovascular repair group, it is not possible to calculate a tangible odds ratio for the elective endovascular surgery group (endovascular vs open).

Table 5 shows previous reports on the incidence of postoperative delirium following vascular surgery.

Table 5.

Previously Published Reports on Incidence of Delirium following Vascular Surgery

Lead Author	Year	Incidence (%)	Significant Risk Factors	Elective Surgery Included	Emergency Surgery Included
Katznelson³¹	2009	22	Beta-blockers, age, history of cerebrovascular accident, open aortic reconstruction, amputation	Yes	No
Balansundaram²³	2007	29.1–39.2	Age, cognition, depression, intraoperative blood transfusion, previous amputation	Yes	No
Benoit¹⁹	2005	33	Pack-years smoked, mental status scores, psychoactive medication	Yes	No
Böhner²⁰	2003	39.2		Yes	No
Schneider²¹	2002	36	Depression, perioperative transfusion/infusion	Yes	No

Discussion

This is the first study to report on the incidence, risk factors, and outcomes of delirium after elective and emergency open and endovascular aortoiliac surgery at a surgical ward with a high-standard delirium care protocol. The overall incidence of delirium was 23%. An incidence as high as 59% was found after emergency surgery. In contrast, in elective surgery, our study showed a delirium rate of 14%. This delirium rate is low compared to previous studies in elective patients, showing an incidence of delirium of 33 to 36.2%.^19,21 This suggests a positive effect of the high-standard delirium care given on our surgical ward; however, the previously mentioned studies did not include endovascular surgery and patient groups might be too heterogeneous and therefore noncomparable (see Table 5). By optimizing conservative preoperative measurements preventing delirium, medication to treat delirium might not be needed because in certain patients, delirium does not occur. However, in the emergency surgery group, the incidence of delirium is as high as 59%, potentially caused by hemodynamic instability, blood loss, and variations in blood pressure during the operation and in the acute setting. Furthermore, we think that the incidence and outcome of postoperative delirium might be positively influenced by implementing a delirium protocol at every ICU. Prophylactic intraoperative intravenous medication (haloperidol) preventing delirium in this group might be challenging because of the amount of blood loss. Intramuscular medication might be an option here.

As in our study, other studies have described a reduction in the prevalence of delirium and a shorter length of hospital stay owing to high-standard delirium care.^16,25,28,29

Despite the significantly higher mean age in the EVAR group compared to the open surgery group, no patient in the elective EVAR group developed delirium. This negligible delirium rate is an obvious advantage of the elective EVAR procedure setting. All patients who did develop delirium after an endovascular procedure were in an emergency setting. Reperfusion syndrome following supraceliac balloon occlusion might be a contributing factor in these emergency EVAR patients suffering from delirium. Because not one patient in the elective endovascular group developed delirium, we were not able to calculate a tangible odds ratio for the elective endovascular surgery (OR = ∞ [infinity] for endovascular vs open surgery). This also precluded EVAR versus laparotomy analysis as a risk factor in the multivariate analysis.

After multivariate analysis, age and emergency surgery were significantly associated with a greater risk of developing delirium. These risk factors were also found in other studies and reviews. Cognitive impairment might also be a risk factor, but because we included patients in an emergency setting (although patients suffering from dementia were excluded), we were not able to measure preoperative cognitive status in all patients. In our study, delirium was also associated with the development of more complications and a longer ICU and total length of hospital stay, which is according to the literature.^{1,10,20,21,30}

Length of ventilator requirements was not related to the occurrence of delirium. However, prolonged sedation might have suppressed delirious symptoms.

Patients were enrolled prospectively and were all admitted to a surgical ward with well-described high-standard delirium care. Daily follow-up by the nursing staff and a geriatric consulting team with a reliable delirium workup and protocol maximized the identification of postoperative delirium, in contrast to other studies where the follow-up was performed by a consulting psychiatrist.^20,21

Within the strategy used by the nursing staff, the DOS is validated for a mean score of 3 after three measurements over the last 24 hours. In this study, patients with a DOS score of 3 or more at a single measurement were considered delirious. By using the DOS score in this way, the threshold to detect delirium might be lower than by using the DOS score in the validated way. A geriatric consulting team diagnosed delirium according to the DSM-IV criteria and subsequently treated and followed these patients. The 14% delirium rate found after elective surgery (including endovascular procedures) is still low compared to the incidence of 33 to 36.2% reported in the literature, despite this active low-threshold delirium detection.

Delirium is not specific to vascular surgery. The association between vascular surgery and delirium may have a different or additional pathophysiologic basis compared to surgery for nonvascular problems.³ Atherosclerosis, for example, is known to impair cognitive abilities. Delirium and atherosclerosis share common risk factors, such as older age, male sex, and renal function loss.^1,3,10,30

Recently, some progress was made in the medical treatment of delirium.^17,30 Because symptomatic atherosclerosis, a known risk for dementia and delirium, is inherent to our study population, the generalizability of our findings to other medical and (nonvascular) surgical populations may be limited. Benoit and colleagues suggested that aggressive medical treatment of cardiovascular disease is of benefit in preventing delirium.¹⁹ Further studies are needed to investigate the need and possibilities of delirium prophylaxis in patients undergoing (acute aortoiliac) surgery.

In conclusion, delirium is an important and frequent complication after aortoiliac surgery, especially emergency surgery. Considering the delirium rate reported in the literature, high-standard delirium care seems to reduce the risk of this complication.

Footnotes

Acknowledgment

Financial disclosure of authors and reviewers: None reported.

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