Neuropsychological Outcome After Carbon Monoxide Exposure Following a Storm: A Case-Control Study

Bérengère Pages; Mélanie Planton; Sophie Buys; Béatrice Lemesle; Philippe Birmes; Emmanuel Joseph Barbeau; Stéphanie Maziero; Laurie Cordier; Claudine Cabot; Michèle Puel; Michèle Genestal; François Chollet; Jérémie Pariente

Disclosures

BMC Neurol. 2014;14(153)

Background

The cognitive consequences of carbon monoxide (CO) poisoning are well described.^[1] They can be observed during the acute phase of the poisoning, after a few days and persist for over a year.^[2–6] They mainly involve memory, attention, processing speed and executive functions.^[6] However, most studies have been carried out without an ad-hoc group of control subjects, mainly relying on published norms for comparison.^[7,8] Interestingly, Deschamps et al. did not evidence any difference between patients and controls when a specific group of controls was recruited.^[9] These last studies gathered patients with variable circumstances of CO intoxication, which may be the reason for their heterogeneous results, but which also questions the extent to which results apply to all patients. It was to avoid these limitations that we carried out the present study in a homogenous group of intoxicated patients using rigorously selected control subjects.

The storm Klaus reached the South West of France between 23^rd and 25^th January 2009 leaving 1,745,000 households without electricity. It is considered to be the most violent storm in France in the past decade, resulting in 1.2 billion Euros of structural damage. Alternative means of heating and lighting, including electricity generators, were used and resulted in increased CO poisoning. 117 persons were poisoned in the Midi-Pyrenean region and referenced by the local specialized center.

The main aim of this study was to evaluate cognitive and psychiatric outcome after CO exposure during the Klaus storm in a homogeneous group of patients and to compare the results with those obtained in a group of controls paired 1:1 to patients for age, gender and education level.

1 2 3 4 5 6

Next Section

Table 1. Causes of CO poisoning, initial symptoms and symptoms observed during the study
Cause of CO poisoning
Electric generator	58%
Gas heater	29%
Charcoal heater	8%
Gas water heater	5%
Initial symptoms*
Headache	82%
Dizziness	55%
Nausea	53%
Fatigue	29%
Loss of consciousness	29%
Cardiac ischemia	10%
Severe ketoacidosis	3%
Acute pulmonary edema	3%
Symptoms during study evaluation
Headache	47%
Fatigue	45%
Feeling sad	39%
Concentration difficulties	39%
Feeling apathetic	32%
Experiencing reviviscences	32%
Memory complaint	26%
Reduction of daily activities	26%
Still on sick leave	24%

*No patient presented paralysis, ventricular arrhythmia, convulsion, shock, coma, stroke or rhabdomyolysis as initial symptoms. No brain lesions assessed by CT scan was reported.

Table 2. Patients' and controls' cognitive, psychiatric and global scores
	Patients (n = 38)	Controls (n = 38)	p value	Cohen's D
Cognitive assessment
Disorientation in time and space (MEM III)
MEM III, orientation (/14)	13.76 (±0.48)	13.86 (±0.34)	0.281	-
Memory
Free recall
FCRST (sum of 3 free recall,/48)	11.21 (±2.30)	11.86 (±2.32)	0.048	0.47
FCRST (delayed free recall,/16)	13 (±2.02)	13.92 (±1.51)	0.028	0.52
Cued recall
FCSRT (sum of 3 total recall,/48)	14.63 (±1.66)	15.36 (±0.88)	0.030	0.55
FCSRT (delayed total recall,/16)	15.63 (±0.91)	15.92 (±0.35)	0.073	-
Executive functions
Processing speed
TMT A time	36.73 (±17.64)	31.13 (±12.04)	0.110	-
Stroop test (denomination time)	64.21 (±14.58)	59.05 (±8.39)	0.063	-
Stroop test (reading time)	48.31 (±10.07)	41.71 (±6.54)	0.001	0.79
Digit symbol test (/133)	67.92 (±17.80)	76.71 (±17.74)	0.034	0.49
Working memory
Letter-Number sequencing (WAIS III,/21)	9.97 (±2.56)	11.36 (±2.36)	0.016	0.57
Flexibility
TMTB time	36.73 (±17.64)	31.13 (±12.04)	0.010	0.63
TMT B-A time	54.55 (±43.57)	32.24 (±24.13)	0.008	0.64
TMT B-A Errors	0.08 (±0.68)	0.13 (±0.34)	0.685	-
Inhibition
Stroop test (interference score, time)	59.65 (±38.36)	39.86 (±21.37)	0.007	0.61
Stroop test (interference score, non-corrected errors)	0.47 (±1.51)	0.02 (±0.16)	0.013	0.59
Language
Denomination (/10)	9.95(±0.23)	9.95 (±0.23)	1.000	-
Psychiatric assessment
MNI, major depressive episode, n (%)	8 (21.05%)	0	0.003	-
MNI, manic episode, n (%)	2 (5.26%)	1 (2.63%)	0.556	-
MNI, hypomanic episode, n (%)	2 (5.26%)	0	0.152	-
MNI, post-traumatic stress disorder, n (%)	6 (15.78%)	0	0.011	-
MNI, psychotic disorders, n (%)	1 (2.63%)	0	0.314	-
MNI, antisocial personality disorder, n (%)	0	0	-	-
Global assessment
Cognitive complaints
Mc Nair score (/45)	11.56 (±7.97)	13.52 (±5.00)	0.206	-
Quality of life
MOS SF-36, Total (/135)	103.81 (±18.37)	113.42 (±9.29)	0.020	0.69

MEM III, Wechsler Memory Scale; FCRST, Free and Cued Selective Reminding Test; WAIS III, Wechsler Adult Intelligence Scale; TMT, Trail Making Test; MINI, Mini International Neuropsychiatric Interview; MOS SF-36, Medical outcome Study Short Form 36.