Cardiopulmonary bypass temperature and brain function

A debate has emerged in recently published studies about the optimum cardiopulmonary bypass temperature for good neurological outcome - warm vs. cold, i.e. normothermic vs. hypothermic. Although many comparative studies have been performed, the results of these studies are inconclusive and are difficult to interpret. Brain function has been studied in terms of neurological and neuropsychological outcome, protein S100beta levels as a marker of brain damage, and cerebral oxygenation using jugular bulb oximetry and near-infrared spectroscopy. The studies produce no conclusive proof of the superiority of warm or cold cardiopulmonary bypass. However, it appears that any degree of bypass hypothermia (< 35 degrees C) may protect the brain. On the other hand, even a slight increase in bypass temperature to > 37 degrees C may cause marked brain injury.     

Assessment of two thoracolumbar fracture classification systems as used by multiple surgeons

BACKGROUND: The reproducibility and repeatability of modern systems for classification of thoracolumbar injuries have not been sufficiently studied. We assessed the interobserver and intraobserver reproducibility of the AO (Arbeitsgemeinschaft für Osteosynthesefragen) classification and compared it with that of the Denis classification. Our purpose was to determine whether the newer, AO system had better reproducibility than the older, Denis classification. METHODS: Anteroposterior and lateral radiographs and computerized tomography scans (axial images and sagittal reconstructions) of thirty-one acute traumatic fractures of the thoracolumbar spine were presented to nineteen observers, all trained spine surgeons, who classified the fractures according to both the AO and the Denis classification systems. Three months later, the images of the thirty-one fractures were scrambled into a different order, and the observers repeated the classification. The Cohen kappa (kappa) test was used to determine interobserver and intraobserver agreement, which was measured with regard to the three basic classifications in the AO system (types A, B, and C) as well as the nine subtypes of that system. We also measured the agreement with regard to the four basic types in the Denis classification (compression, burst, seat-belt, and fracture-dislocation) and with regard to the sixteen subtypes of that system. RESULTS: The AO classification was fairly reproducible, with an average kappa of 0.475 (range, 0.389 to 0.598) for the agreement regarding the assignment of the three types and an average kappa of 0.537 for the agreement regarding the nine subtypes. The average kappa for the agreement regarding the assignment of the four Denis fracture types was 0.606 (range, 0.395 to 0.702), and it was 0.173 for agreement regarding the sixteen subtypes. The intraobserver agreement (repeatability) was 82% and 79% for the AO and Denis types, respectively, and 67% and 56%, for the AO and Denis subtypes, respectively. CONCLUSIONS: Both the Denis and the AO system for the classification of spine fractures had only moderate reliability and repeatability. The tendency for well-trained spine surgeons to classify the same fracture differently on repeat testing is a matter of some concern.     

Transplants of neurosphere cell suspensions from aged mice are functional in the mouse model of Parkinson's

Neural stem cell therapy has the potential to treat neurodegenerative disorders. For Parkinson's disease (PD), the goal is to enhance the dopamine system sufficiently to restore the control of movement and motor activities. In consideration of autologous stem cell therapy for PD, it will be necessary to propagate the cells in most cases from aged brain tissue. We isolated cells from the subventricular zone (SVZ) in the brains of 1-year-old enhanced green fluorescent protein (GFP) mice and generated neurospheres in culture. Neurospheres yielding high numbers of neurons and astrocytes "de novo" were selected and cryopreserved before evaluating the efficacy of neurosphere cell suspensions transplanted to the 6-hydroxydopamine (6-OHDA) model of PD. In mice unilaterally lesioned with 6-OHDA, transplants of neurosphere cell suspensions to the striatum yielded astrocytes and tyrosine hydroxylase positive neurons that reduced or reversed the drug-induced behavioral circling response to amphetamine and apomorphine. Control mice without the cell suspensions showed no change in the motor behavior. Our results indicate that the SVZ in the aged mouse brain contains cells that can be expanded in the form of neurospheres, cryopreserved, re-expanded and then transplanted into the damaged dopamine system to generate functional cell progeny that offset the motor disturbances in the nigrostriatal system.     

Intellectual decline in children with moyamoya and sickle cell anaemia

Intelligence is reported to decline after onset of moyamoya in Japanese populations, but there is less evidence for this in Western populations where the condition may be secondary to stroke and sickle cell anaemia (SCA). Preoperative longitudinal IQ data were obtained from 15 children (seven males, eight females) who developed moyamoya syndrome (MMS) following a stroke (six with SCA, nine without SCA), and 19 controls (10 males, nine females; nine healthy control participants, 10 with SCA). At baseline assessment (Time 1) median age of patients was 7 years 6 months (range 3y 7mo to 12y 5mo); median age of controls was 6 years 3 months (range 4y to 11y 6mo). At follow-up (Time 2), ages were 11 years 8 months (range 3y 7mo to 12y 5mo) and 12 years 8 months (range 6y 4mo to 16y 8mo) in patients and controls respectively. Median duration of follow-up for the patient group was 3 years (range 7 to 10y) and in controls, 4 years 1 month (range 1 to 10y). In children with SCA, Verbal and Performance IQs (VIQ and PIQ) were significantly lower than in controls at Time 1; there was an additional independent statistically significant reduction in PIQ associated with MMS (p=0.004). Although there were further significant reductions in IQ by the second assessment for patients with MMS compared with controls, IQ did not differ significantly between groups with and without SCA. While the reduction in IQ attributed to SCA does not appear to become more marked with increasing age, the difference between those with and without MMS is associated with increasing effect over time.     

Pharmacokinetics of remifentanil and its major metabolite, remifentanil acid, in ICU patients with renal impairment

Background. The pharmacokinetics of remifentanil, an opioidanalgesic metabolized by non-specific esterases, and its principalmetabolite, remifentanil acid (RA), which is excreted via thekidneys, were assessed as part of an open-label safety studyin intensive care unit (ICU) patients with varying degrees ofrenal impairment. Methods. Forty adult ICU patients with normal/mildly impairedrenal function (creatinine clearance [CL_cr] 62.9 (SD) 14.5 mlmin^–1; n=10) or moderate/severe renal impairment (CL_cr14.7 (15.7) ml min^–1; n=30) were included. Remifentanilwas infused for up to 72 h, at a starting rate of 6–9µg kg^–1 h^–1 titrated to achieve a target sedationlevel, with additional propofol (0.5 mg kg^–1 h^–1)if required. Intensive arterial sampling was performed for upto 72 h after infusion. Pharmacokinetic parameters obtainedby simultaneous modelling of remifentanil and RA data were statisticallycompared between the two groups. Results. Remifentanil pharmacokinetics were not significantlyaffected by renal status. RA clearance in the moderate/severegroup was reduced to about 25% that of the normal/mild group(41 (29) vs 176 (49) ml kg^–1 h^–1, P<0.0001).Metabolic ratio, a predictor of the ratio of RA to remifentanilconcentrations at steady state, was approximately eight-foldhigher in the moderate/severe group relative to the normal/mildgroup (116 (110) vs 15 (4), P<0.0001). Maximum RA levelsapproached 700 ng ml^–1 in the moderate/severe group. Conclusions. Although RA accumulates in patients with moderate/severerenal impairment, pharmacokinetic modelling predicts that RAconcentrations during a 9 µg kg^–1 h^–1 remifentanilinfusion for up to 15 days would not exceed those reported inthe present study, for which no associated prolongation of µ-opioideffects was observed. Br J Anaesth 2004; 92: 493–503     

Superior mesenteric artery syndrome following correction of kyphosis in an adult

Superior mesenteric artery (SMA) syndrome is well described in the pediatric literature; however, to date, it has not been described in an adult individual undergoing correction of thoracic kyphosis. Medical history, physical findings, and the results of imaging studies were analyzed to describe the patient's onset of gastrointestinal obstruction following surgical correction of thoracic kyphosis. The postoperative course was marked by the onset of nausea and vomiting on postoperative day 24. The patient was admitted to the hospital, and the small bowel follow-through study showed blockage of the third portion of the duodenum at the level of the SMA. Oral intake was restricted, and total parenteral nutrition was instituted with complete resolution of her symptoms. At 1 year postoperatively, the patient was symptom-free. Although vascular compression of the duodenum with subsequent nausea and vomiting and electrolyte imbalance, caused by the relative lengthening of the spine, is most commonly associated with surgical correction of coronal plane deformities (ie, scoliosis), it may occur in patients undergoing correction of thoracic kyphosis as well. SMA syndrome is a well known potential complication in adolescents, and it should also be taken into consideration in adults undergoing deformity correction. Early institution of general medical measures of nasogastric suction, oral intake restriction, and intravenous alimentation can be successful.