Traumatic cervical spinal cord injury: Comparison of two different blood pressure targets on neurological recovery.

BACKGROUND: Controversy exists whether blood pressure augmentation therapy benefits patients suffering from spinal cord injury (SCI). This retrospective comparative study was designed to assess the impact of two different mean arterial pressure (MAP) targets (85-90 mmHg vs. 65-85 mmHg) on neurological recovery after traumatic cervical SCI. METHODS: Fifty-one adult patients with traumatic cervical SCI were retrospectively divided into two groups according to their intensive care unit (ICU) MAP targets: 85-90 mmHg (higher MAP group, n = 32) and 65-85 mmHg (lower MAP group, n = 19). Invasive MAP measurements were stored as 2-min median values for 3-7 days. The severity of SCI (AIS grade and neurological level) was evaluated upon ICU stay and during rehabilitation. Neurological recovery was correlated with individual mean MAP values and with the proportion of MAP values ≥85 mmHg upon the first 3 days (3d-MAP%≥85 ). RESULTS: The initial AIS grades were A 29.4%, B 17.6%, C 31.4%, and D 21.6%. AIS grade improved in 24 patients (47.1%). During ICU care, 82.0% and 36.8% of the measured MAP values reached ≥85 mmHg in the higher and the lower MAP groups, respectively (p < .001). The medians of individual mean MAP values were different between the groups (90.2 mmHg vs. 81.4 mmHg, p < .001). Similarly, 3d-MAP%≥85 was higher in the higher MAP group (85.6% vs. 50.0%, p < .001). However, neurological recovery was not different between the groups, nor did it correlate with individual mean MAP values or 3d-MAP%≥85 . CONCLUSION: The currently recommended MAP target of 85-90 mmHg was not associated with improved outcomes compared to a lower target in patients with traumatic cervical SCI in this cohort.

Persistent pain in intensive care survivors: a systematic review.

BACKGROUND: According to earlier studies where the main aim has been quality of life, there is growing evidence of increased levels of persistent pain in survivors of critical illness. The cause of admission and several factors during intensive care may have associated risk factors for pain persistence. This systematic review aims to determine the incidence or prevalence of persistent pain after critical illness and to identify risk factors for it. METHODS: Six databases were searched, and eventually nine studies were included in the final systematic process. The validity of observational and cross-sectional studies was analysed using the National Institute of Health 'Quality Assessment Tool for Observational Cohort and Cross-Sectional Studies'. RESULTS: The incidence of persistent pain after intensive care varied from 28% to 77%. Risk factors for persistent pain were acute pain at discharge from ICU, higher thoracic trauma score, surgery, pre-existing pain, organ failure, longer length of ventilator or hospital stay, and sepsis. No difference in incidence between medical and surgical patients was found. CONCLUSIONS: New systematic, observational studies are warranted to identify persistent pain-related factors in intensive care to improve pain management protocols and thereby diminish the risk of persistent pain after ICU stay.

Near-infrared spectroscopy after out-of-hospital cardiac arrest.

BACKGROUND: Cerebral hypoperfusion may aggravate neurological damage after cardiac arrest. Near-infrared spectroscopy (NIRS) provides information on cerebral oxygenation but its relevance during post-resuscitation care is undefined. We investigated whether cerebral oxygen saturation (rSO2) measured with NIRS correlates with the serum concentration of neuron-specific enolase (NSE), a marker of neurological injury, and with clinical outcome in out-of-hospital cardiac arrest (OHCA) patients. METHODS: We performed a post hoc analysis of a randomised clinical trial (COMACARE, NCT02698917) comparing two different levels of carbon dioxide, oxygen and arterial pressure after resuscitation from OHCA with ventricular fibrillation as the initial rhythm. We measured rSO2 in 118 OHCA patients with NIRS during the first 36 h of intensive care. We determined the NSE concentrations from serum samples at 48 h after cardiac arrest and assessed neurological outcome with the Cerebral Performance Category (CPC) scale at 6 months. We evaluated the association between rSO2 and serum NSE concentrations and the association between rSO2 and good (CPC 1-2) and poor (CPC 3-5) neurological outcome. RESULTS: The median (inter-quartile range (IQR)) NSE concentration at 48 h was 17.5 (13.4-25.0) µg/l in patients with good neurological outcome and 35.2 (22.6-95.8) µg/l in those with poor outcome, p < 0.001. We found no significant correlation between median rSO2 and NSE at 48 h, rs = - 0.08, p = 0.392. The median (IQR) rSO2 during the first 36 h of intensive care was 70.0% (63.5-77.0%) in patients with good outcome and 71.8% (63.3-74.0%) in patients with poor outcome, p = 0.943. There was no significant association between rSO2 over time and neurological outcome. In a binary logistic regression model, rSO2 was not a statistically significant predictor of good neurological outcome (odds ratio 0.99, 95% confidence interval 0.94-1.04, p = 0.635). CONCLUSIONS: We found no association between cerebral oxygenation measured with NIRS and NSE concentrations or outcome in patients resuscitated from OHCA. TRIAL REGISTRATION: ClinicalTrials.gov, NCT02698917 . Registered on 26 January 2016.

Pantoprazole in ICU patients at risk for gastrointestinal bleeding-1-year mortality in the SUP-ICU trial.

BACKGROUND: The long-term effects of stress ulcer prophylaxis with pantoprazole are unknown in ICU patients. We report 1-year mortality outcome in the Stress Ulcer Prophylaxis in the Intensive Care Unit (SUP-ICU) trial. METHODS: In the SUP-ICU trial, acutely admitted adult ICU patients at risk of gastrointestinal bleeding were randomised to intravenous pantoprazole 40 mg vs placebo (saline) once daily during their ICU stay. We assessed mortality at 1 year and did sensitivity analyses according to the trial protocol and statistical analysis plan. RESULTS: A total of 3261 of the 3291 patients with available data (99.1%) were followed up at 1 year after randomisation; 1635 were allocated to pantoprazole and 1626 to placebo. At 1 year after randomisation, 610 of 1635 patients (37.3%) had died in the pantoprazole group as compared with 601 of 1626 (37.0%) in the placebo group (relative risk, 1.01; 95% confidence interval 0.92-1.10). The results were consistent in the sensitivity analysis adjusted for baseline risk factors and in those of the per-protocol population. We did not observe heterogeneity in the effect of pantoprazole vs placebo on 1-year mortality in the predefined subgroups, that is, patients with and without shock, mechanical ventilation, liver disease, coagulopathy, high disease severity (SAPS II > 53) or in medical vs surgical ICU patients. CONCLUSION: We did not observe a difference in 1-year mortality among acutely admitted adult ICU patients with risk factors for gastrointestinal bleeding allocated to stress ulcer prophylaxis with pantoprazole or placebo during the ICU stay. (The SUP-ICU trial was funded by Innovation Fund Denmark and others; ClinicalTrials.gov number, NCT02467621).

Postoperative Delirium in Cardiac Surgery Patients.

OBJECTIVE: The authors studied the incidence of postoperative delirium among cardiac surgery patients using the Intensive Care Delirium Screening Checklist (ICDSC). DESIGN: Prospective screening. SETTING: Two university hospitals. PARTICIPANTS: A total of 1,036 consecutive patients. INTERVENTIONS: None. MEASUREMENTS AND MAIN RESULTS: Patients were prospectively screened from day 1 to day 10 after surgery or until hospital discharge. Appropriate perioperative data were collected. The overall incidence of postoperative delirium was 11.5%. In the multivariate logistic regression analysis, age over 70 years, higher EuroSCORE points, longer aortic occlusion time, and profuse drainage increased the incidence of delirium. The duration of mechanical ventilation and intensive care unit length of stay were longer in the group of patients with delirium (10.6 hours [6.6-19.5] v 6.4 hours [4.9-8.6], p < 0.001, and 1.7 days [0.9-4.2] v 0.9 days [0.9-1], p < 0.001). CONCLUSIONS: Postoperative delirium is common after cardiac surgery, and it is associated with the duration of mechanical ventilation.

Lower versus higher hemoglobin threshold for transfusion in septic shock.

BACKGROUND: Blood transfusions are frequently given to patients with septic shock. However, the benefits and harms of different hemoglobin thresholds for transfusion have not been established. METHODS: In this multicenter, parallel-group trial, we randomly assigned patients in the intensive care unit (ICU) who had septic shock and a hemoglobin concentration of 9 g per deciliter or less to receive 1 unit of leukoreduced red cells when the hemoglobin level was 7 g per deciliter or less (lower threshold) or when the level was 9 g per deciliter or less (higher threshold) during the ICU stay. The primary outcome measure was death by 90 days after randomization. RESULTS: We analyzed data from 998 of 1005 patients (99.3%) who underwent randomization. The two intervention groups had similar baseline characteristics. In the ICU, the lower-threshold group received a median of 1 unit of blood (interquartile range, 0 to 3) and the higher-threshold group received a median of 4 units (interquartile range, 2 to 7). At 90 days after randomization, 216 of 502 patients (43.0%) assigned to the lower-threshold group, as compared with 223 of 496 (45.0%) assigned to the higher-threshold group, had died (relative risk, 0.94; 95% confidence interval, 0.78 to 1.09; P=0.44). The results were similar in analyses adjusted for risk factors at baseline and in analyses of the per-protocol populations. The numbers of patients who had ischemic events, who had severe adverse reactions, and who required life support were similar in the two intervention groups. CONCLUSIONS: Among patients with septic shock, mortality at 90 days and rates of ischemic events and use of life support were similar among those assigned to blood transfusion at a higher hemoglobin threshold and those assigned to blood transfusion at a lower threshold; the latter group received fewer transfusions. (Funded by the Danish Strategic Research Council and others; TRISS ClinicalTrials.gov number, NCT01485315.).

FOUR score in monitoring the level of consciousness of an intensive care patient: first experience of the use of the Finnish language version.

BACKGROUND: The goal was to increase the knowledge of Full Outline of UnResponsiveness (FOUR) score in Finland, release its Finnish version and to evaluate its usefulness in Finnish ICU patients. MATERIALS AND METHODS: The highest FOUR and Glasgow Coma Scale (GCS) scores of the adult ICU patients treated in Tampere University Hospital between 1st January and 31st October 2015 were analyzed retrospectively. In-hospital and 1-month mortality were the primary end-points. RESULTS: The Finnish version of FOUR performed comparably to previous studies. The ability of FOUR to predict mortality was equal to GCS. CONCLUSIONS: FOUR is at least equal to GCS in predicting mortality of ICU patients.

Prognostic Value of Secretoneurin in Critically Ill Patients With Infections.

OBJECTIVES: Secretoneurin is produced in neuroendocrine cells, and the myocardium and circulating secretoneurin levels provide incremental prognostic information to established risk indices in cardiovascular disease. As myocardial dysfunction contributes to poor outcome in critically ill patients, we wanted to assess the prognostic value of secretoneurin in two cohorts of critically ill patients with infections. DESIGN: Two prospective, observational studies. SETTING: Twenty-four and twenty-five ICUs in Finland. PATIENTS: A total of 232 patients with severe sepsis (cohort #1) and 94 patients with infections and respiratory failure (cohort #2). INTERVENTIONS: None. MEASUREMENTS AND MAIN RESULTS: We measured secretoneurin levels by radioimmunoassay in samples obtained early after ICU admission and compared secretoneurin with other risk indices. In patients with severe sepsis, admission secretoneurin levels (logarithmically transformed) were associated with hospital mortality (odds ratio, 3.17 [95% CI, 1.12-9.00]; p = 0.030) and shock during the hospitalization (odds ratio, 2.17 [1.06-4.46]; p = 0.034) in analyses that adjusted for other risk factors available on ICU admission. Adding secretoneurin levels to age, which was also associated with hospital mortality in the multivariate model, improved the risk prediction as assessed by the category-free net reclassification index: 0.35 (95% CI, 0.06-0.64) (p = 0.02). In contrast, N-terminal pro-B-type natriuretic peptide levels were not associated with mortality in the multivariate model that included secretoneurin measurements, and N-terminal pro-B-type natriuretic peptide did not improve patient classification on top of age. Secretoneurin levels were also associated with hospital mortality after adjusting for other risk factors and improved patient classification in cohort #2. In both cohorts, the optimal cutoff for secretoneurin levels at ICU admission to predict hospital mortality was ≈ 175 pmol/L, and higher levels were associated with mortality also when adjusting for Simplified Acute Physiology Score II and Sequential Organ Failure Assessment scores. CONCLUSIONS: Secretoneurin levels provide incremental information to established risk indices for the prediction of mortality and shock in critically ill patients with severe infections.

Comparing the prognostic performance of ASSIST to interleukin-6 and procalcitonin in patients with severe sepsis or septic shock.

CONTEXT: We recently derived and validated a multi-biomarker-based model (ASSIST) to stratify patients with sepsis based on initial mortality risk. OBJECTIVE: The objective of this study was to compare the performance of ASSIST to interleukin-6 (IL6) and procalcitonin (PCT). METHODS: The area-under-the-receiver operating characteristic curve for predicting 28-d mortality using ASSIST was compared with that of IL6 (n = 452) and PCT (n = 235). RESULTS: The area under the curve for ASSIST was greater than that of IL6 and PCT. CONCLUSIONS: ASSIST estimated the probability of mortality more reliably than IL6 and PCT in this cohort of patients with sepsis.

Predicting one-year mortality of critically ill patients with early acute kidney injury: data from the prospective multicenter FINNAKI study.

INTRODUCTION: No predictive models for long-term mortality in critically ill patients with acute kidney injury (AKI) exist. We aimed to develop and validate two predictive models for one-year mortality in patients with AKI based on data (1) on intensive care unit (ICU) admission and (2) on the third day (D3) in the ICU. METHODS: This substudy of the FINNAKI study comprised 774 patients with early AKI (diagnosed within 24 hours of ICU admission). We selected predictors a priori based on previous studies, clinical judgment, and differences between one-year survivors and non-survivors in patients with AKI. We validated the models internally with bootstrapping. RESULTS: Of 774 patients, 308 (39.8%, 95% confidence interval (CI) 36.3 to 43.3) died during one year. Predictors of one-year mortality on admission were: advanced age, diminished premorbid functional performance, co-morbidities, emergency admission, and resuscitation or hypotension preceding ICU admission. The area under the receiver operating characteristic curve (AUC) (95% CI) for the admission model was 0.76 (0.72 to 0.79) and the mean bootstrap-adjusted AUC 0.75 (0.74 to 0.75). Advanced age, need for mechanical ventilation on D3, number of co-morbidities, higher modified SAPS II score, the highest bilirubin value by D3, and the lowest base excess value on D3 remained predictors of one-year mortality on D3. The AUC (95% CI) for the D3 model was 0.80 (0.75 to 0.85) and by bootstrapping 0.79 (0.77 to 0.80). CONCLUSIONS: The prognostic performance of the admission data-based model was acceptable, but not good. The D3 model for one-year mortality performed fairly well in patients with early AKI.

A multibiomarker-based outcome risk stratification model for adult septic shock*.

OBJECTIVES: Clinical trials in septic shock continue to fail due, in part, to inequitable and sometimes unknown distribution of baseline mortality risk between study arms. Investigators advocate that interventional trials in septic shock require effective outcome risk stratification. We derived and tested a multibiomarker-based approach to estimate mortality risk in adults with septic shock. DESIGN: Previous genome-wide expression studies identified 12 plasma proteins as candidates for biomarker-based risk stratification. The current analysis used banked plasma samples and clinical data from existing studies. Biomarkers were assayed in plasma samples obtained from 341 subjects with septic shock within 24 hours of admission to the ICU. Classification and regression tree analysis was used to generate a decision tree predicting 28-day mortality based on a combination of both biomarkers and clinical variables. The derived tree was first tested in an independent cohort of 331 subjects, then calibrated using all subjects (n = 672), and subsequently validated in another independent cohort (n = 209). SETTING: Multiple ICUs in Canada, Finland, and the United States. SUBJECTS: Eight hundred eighty-one adults with septic shock or severe sepsis. INTERVENTION: None. MEASUREMENTS AND MAIN RESULTS: The derived decision tree included five candidate biomarkers, admission lactate concentration, age, and chronic disease burden. In the derivation cohort, sensitivity for mortality was 94% (95% CI, 87-97), specificity was 56% (50-63), positive predictive value was 50% (43-57), and negative predictive value was 95% (89-98). Performance was comparable in the test cohort. The calibrated decision tree had the following test characteristics in the validation cohort: sensitivity 85% (76-92), specificity 60% (51-69), positive predictive value 61% (52-70), and negative predictive value 85% (75-91). CONCLUSIONS: We have derived, tested, calibrated, and validated a risk stratification tool and found that it reliably estimates the probability of mortality in adults with septic shock.

Variation in the use of renal replacement therapy in patients with septic shock: a substudy of the prospective multicenter observational FINNAKI study.

INTRODUCTION: Indications for renal replacement therapy (RRT) have not been generally standardized and vary among intensive care units (ICUs). We aimed to assess the proportion, indications, and modality of RRT, as well as the association between the proportion of RRT use and 90-day mortality in patients with septic shock in Finnish adult ICUs. METHODS: We identified patients with septic shock from the prospective observational multicenter FINNAKI study conducted between 1 September 2011 and 1 February 2012. We divided the ICUs into high-RRT and low-RRT ICUs according to the median of the proportion of RRT-treated patients with septic shock. Differences in indications, and modality of RRT between ICU groups were assessed. Finally, we performed an adjusted logistic regression analysis to evaluate the possible association of the ICU group (high vs. low-RRT) with 90-day mortality. RESULTS: Of the 726 patients with septic shock, 131 (18.0%, 95% CI 15.2 to 20.9%) were treated with RRT. The proportion of RRT-treated patients varied from 3% up to 36% (median 19%) among ICUs. High-RRT ICUs included nine ICUs (354 patients) and low-RRT ICUs eight ICUs (372 patients). In the high-RRT ICUs patients with septic shock were older (P = 0.04), had more cardiovascular (P <0.001) and renal failures (P = 0.003) on the first day in the ICU, were more often mechanically ventilated, and received higher maximum doses of norepinephrine (0.25 µg/kg/min vs. 0.18 µg/kg/min, P <0.001) than in the low-RRT ICUs. No significant differences in indications for or modality of RRT existed between the ICU groups. The crude 90-day mortality rate for patients with septic shock was 36.2% (95% CI 31.1 to 41.3%) in the high-RRT ICUs compared to 33.9% (95% CI 29.0 to 38.8%) in the low-RRT ICUs, P = 0.5. In an adjusted logistic regression analysis the ICU group (high-RRT or low-RRT ICUs) was not associated with 90-day mortality. CONCLUSIONS: Patients with septic shock in ICUs with a high proportion of RRT had more severe organ dysfunctions and received more organ-supportive treatments. Importantly, the ICU group (high-RRT or low-RRT group) was not associated with 90-day mortality.

Fatal surgical or procedure-related complications: a Finnish registry-based study.

INTRODUCTION: In Finland, all healthcare personnel must be insured against causing patient injury. The Patient Insurance Centre (PIC) pays compensation in all cases of malpractice and in some cases of infection or other surgical complications. This study aimed to analyze all complaints relating to fatal surgical or other procedure-related errors in Finland during 2006-2010. MATERIALS AND METHODS: In total, 126 patients fulfilled the inclusion criteria. Details of patient care and decisions made by the PIC were reviewed, and the total national number of surgical procedures for the study period was obtained from the National Hospital Discharge Registry. RESULTS: Of the 94 patients who underwent surgery, most fatal surgical complications involved orthopedic or gastrointestinal surgery. Non-surgical procedures with fatal complications included deliveries (N = 10), upper gastrointestinal endoscopy or nasogastric tube insertion (N = 8), suprapubic catheter insertion (N = 4), lower intestinal endoscopy (N = 5), coronary angiogram (N = 1), pacemaker fitting (N = 1), percutaneous drainage of a hepatic abscess (N = 1), and chest tube insertion (N = 2). In 42 (33.3 %) cases, patient injury resulted from errors made during the procedure, including 24 technical errors and 15 errors of judgment. There were 19 (15.2 %) cases of inappropriate pre-operative assessment, 28 (22.4 %) errors made in postoperative follow-up, 23 (18.4 %) cases of fatal infection, and 11 (8.8 %) fatal complications not linked to treatment errors. CONCLUSION: Fatal surgical and procedure-related complications are rare in Finland. Complications are usually the result of errors of judgment, technical errors, and infections.

[Update on current care guideline: sepsis (adults]. / Sepsis (aikuiset).

The incidence of severe sepsis and septic shock requiring intensive care in Finnish adult population has increased to 0.60 11000 /y. Despite improved prognosis, hospital mortality related to severe sepsis and septic shock is high 24.1%. Key recommendations include prompt administration of antimicrobial therapy, optimally after blood cultures, quantitative fluid resuscitation and imaging studies to identify possible source of infection. Crystalloids are suitable for fluid resuscitation. Norepinephrine is the first-choice vasopressor in septic shock. Hydrocortisone should be considered only if fluid and vasopressor treatment does not restore hemodynamics.

Increased bilateral frontal connectivity during working memory in young adults under the influence of a dopamine D1 receptor antagonist.

Increased frontal bilaterality in old compared with young adults during cognitive performance is a common finding in human functional neuroimaging studies. Age-related reductions in laterality are a widely debated topic and their origins and consequences may be manifold. The current study demonstrates that a dopamine (DA) D1 antagonist induces increased frontal bilateral connectivity in healthy young adults revealed by functional magnetic resonance imaging during a spatial working memory task. Moreover, increases in functional connectivity between right and left prefrontal cortex during the pharmacological challenge were associated with maintaining performance on drug. To our knowledge, this is the first study to pharmacologically induce increased frontal bilateral functional connectivity during a cognitive task in young adults and to show that increased bilaterality is associated with less severe cognitive impairment under the influence of a DA receptor antagonist.

Aging-related increases in behavioral variability: relations to losses of dopamine D1 receptors.

Intraindividual variability (IIV) reflects within-person changes in performance, such as trial-by-trial fluctuations on a reaction-time (RT) task. The neural underpinnings of IIV remain largely unknown. The neurotransmitter dopamine (DA) is of particular interest here, as human populations that exhibit DA alterations, such as the elderly, attention deficit hyperactivity disorder children, persons with schizophrenia, and Parkinson patients, also show increased behavioral IIV. We examined links between DA D(1) binding potential (BP) in multiple brain regions and IIV for the control and interference conditions of the Multi-Source Interference Task (MSIT), tapping the cingulo-fronto-parietal attention network. Participants were 18 young and 20 healthy old adults. PET and the radioligand [(11)C]SCH23390 were used to determine D(1) BP. The intraindividual standard deviation (ISD) was computed across successful latency trials of the MSIT conditions, independent of mean RT differences due to age, trial, and condition. Increasing ISDs were associated with increasing age and diminished D(1) binding in several brain regions (anterior cingulate gyrus, dorsolateral prefrontal cortex, and parietal cortex) for the interference, but not control, condition. Analyses of partial associations indicate that the association between age and IIV in the interference condition was linked to D(1) receptor losses in task-relevant brain regions. These findings suggest that dysfunctional DA modulation may contribute to increased variability in cognitive performance among older adults.

Hemodynamic variables and progression of acute kidney injury in critically ill patients with severe sepsis: data from the prospective observational FINNAKI study.

INTRODUCTION: Knowledge of the association of hemodynamics with progression of septic acute kidney injury (AKI) is limited. However, some recent data suggest that mean arterial pressure (MAP) exceeding current guidelines (60-65 mmHg) may be needed to prevent AKI. We hypothesized that higher MAP during the first 24 hours in the intensive care unit (ICU), would be associated with a lower risk of progression of AKI in patients with severe sepsis. METHODS: We identified 423 patients with severe sepsis and electronically recorded continuous hemodynamic data in the prospective observational FINNAKI study. The primary endpoint was progression of AKI within the first 5 days of ICU admission defined as new onset or worsening of AKI by the Kidney Disease: Improving Global Outcomes (KDIGO) criteria. We evaluated the association of hemodynamic variables with this endpoint. We included 53724 10-minute medians of MAP in the analysis. We analysed the ability of time-adjusted MAP to predict progression of AKI by receiver operating characteristic (ROC) analysis. RESULTS: Of 423 patients, 153 (36.2%) had progression of AKI. Patients with progression of AKI had significantly lower time-adjusted MAP, 74.4 mmHg [68.3-80.8], than those without progression, 78.6 mmHg [72.9-85.4], P < 0.001. A cut-off value of 73 mmHg for time-adjusted MAP best predicted the progression of AKI. Chronic kidney disease, higher lactate, higher dose of furosemide, use of dobutamine and time-adjusted MAP below 73 mmHg were independent predictors of progression of AKI. CONCLUSIONS: The findings of this large prospective multicenter observational study suggest that hypotensive episodes (MAP under 73 mmHg) are associated with progression of AKI in critically ill patients with severe sepsis.

Caudate dopamine D1 receptor density is associated with individual differences in frontoparietal connectivity during working memory.

We assess the relationship of age-related losses in striatal D1 receptor densities to age-related reductions in functional connectivity between spatially distinct cortical regions in healthy human participants. Previous neuroimaging studies have reported age-related differences in functional connectivity of the frontoparietal working memory network and the default mode network during task performance. We used functional magnetic resonance imaging and seed-based connectivity (right dorsolateral and medial prefrontal cortex) to extend these findings: Anterior-posterior connectivity of both these functional networks was reduced in older (65-75 years, n = 18) compared with younger (20-30 years, n = 19) adults, whereas bilateral connectivity in prefrontal cortex was increased in older adults. Positron emission tomography with the D1 receptor ligand [(11)C]SCH23390 was used to assess caudate D1 receptor density in the same sample. Older adults showed significantly reduced caudate D1 receptor density compared to the younger adults. Of key interest, partial correlations showed that individual differences in caudate D1 receptor density were positively associated with individual differences in dorsolateral prefrontal connectivity to right parietal cortex (BA40) and negatively with medial prefrontal connectivity to right parietal cortex (BA40 and postcentral gyrus), after controlling for age. We found no correlation of caudate D1 receptor density with anterior-posterior coupling within the default mode network or with bilateral frontal connectivity. These results are consistent with animal work that has identified a role for caudate D1 receptors in mediating information transfer between prefrontal areas and parietal cortex.

Dopamine D1 receptor associations within and between dopaminergic pathways in younger and elderly adults: links to cognitive performance.

Age-related dopamine (DA) losses have been extensively demonstrated for the D2 receptor subtype. Comparatively little is known about adult age changes regarding D1 receptors. In this study, we demonstrate marked age-related D1 receptor losses in striatal, limbic, and cortical areas using positron emission tomography and the radioligand [(11)C]SCH23390 in humans. Interregional correlations of binding potential (BP) values were high for areas within DA pathways in younger and elderly adults alike. Furthermore, interregional correlations in D1 BP between DA pathways were uniformly high in younger adults, indicating that D1 receptor densities in striatal, limbic, and cortical areas are not regulated independently, despite dopaminergic innervation from different midbrain areas. For elderly adults, between-pathway correlations of D1 receptor densities were preserved only between mesolimbic and mesocortical areas, whereas striatal BPs were weakly related to those in limbic and neocortical regions. Importantly, weak between-pathway correlations in elderly adults were found only for the slower half of the sample when BP was estimated during a cognitive interference task. These results suggest that D1 receptor densities in different pathways are not regulated independently in younger adults, but segregate in older age, and that this segregation of D1 receptor systems may be related to age-related cognitive slowing.