Sevoflurane anaesthesia induces cognitive impairment in young mice through sequential tau phosphorylation

BACKGROUND

The volatile anaesthetic sevoflurane induces time (single or multiple exposures)-dependent effects on tau phosphorylation and cognitive function in young mice. The underlying mechanism for this remains largely undetermined.

METHODS

Mice received 3% sevoflurane for 0.5 h or 2 h daily for 3 days on postnatal day (P) 6, 9, and 12. Another group of mice received 3% sevoflurane for 0.5 h or 1.5 h (3 × 0.5) on P6. We investigated effects of sevoflurane anaesthesia on tau phosphorylation on P6 or P12 mice, on cognitive function from P31 to P37, and on protein interactions, using in vivo studies, in vitro phosphorylation assays, and nanobeam single-molecule level interactions in vitro.

RESULTS

An initial sevoflurane exposure induced CaMKIIα phosphorylation (132 [11]% vs 100 [6]%, P<0.01), leading to tau phosphorylation at serine 262 (164 [7]% vs 100 [26]%, P<0.01) and tau detachment from microtubules. Subsequent exposures to the sevoflurane induced GSK3β activation, which phosphorylated detached or free tau (tau phosphorylated at serine 262) at serine 202 and threonine 205, resulting in cognitive impairment in young mice. In vitro phosphorylation assays also demonstrated sequential tau phosphorylation. Nanobeam analysis of molecular interactions showed different interactions between tau or free tau and CaMKIIα or GSK3β, and between tau and tubulin at a single-molecule level.

CONCLUSIONS

Multiple exposures to sevoflurane can induce sequential tau phosphorylation, leading to cognitive impairment in young mice, highlighting the need to investigate the underlying mechanisms of anaesthesia-induced tau phosphorylation in developing brain.

Focal drug-resistant temporal lobe epilepsy associated with an ipsilateral anterior choroidal artery aneurysm: illustrative case

BACKGROUND

The occurrence of both an intracranial aneurysm and epilepsy, especially drug-resistant epilepsy (DRE), is rare. Although the overall incidence of aneurysms associated with DRE is unclear, it is thought to be particularly infrequent in the pediatric population. Surgical ligation of the offending aneurysm has been reported in conjunction with resolving seizure activity, although few cases have cited a combined approach of aneurysm ligation and resection of an epileptogenic focus.

OBSERVATIONS

We present the case of a 14-year-old female patient with drug-resistant temporal lobe epilepsy and an ipsilateral supraclinoid internal carotid artery aneurysm. Seizure semiology, electroencephalography monitoring, and magnetic resonance imaging all indicated a left temporal epileptogenic focus, in addition to an incidental aneurysm. The authors recommended a combined surgery involving resection of the temporal lesion and surgical clip ligation of the aneurysm. Near-total resection and successful ligation were achieved, and the patient has remained seizure free since surgery at 1 year postoperatively.

LESSONS

In patients with focal DRE and an adjacent intracranial aneurysm, a combined surgical approach involving both resection and surgical ligation can be used. Several surgical timing and neuroanesthetic considerations should be made to ensure the overall safety and efficacy of this procedure.

Differential effects of dexmedetomidine on Gram-positive and Gram-negative bacterial killing and phagocytosis

Dexmedetomidine is a commonly used sedative in perioperative and intensive care settings with purported immunomodulatory properties. Since its effects on immune functions against infections have not been extensively studied, we tested the effects of dexmedetomidine on Gram-positive [Staphylococcus aureus and Enterococcus faecalis] and Gram-negative bacteria [Escherichia coli], and on effector functions of human monocytes THP-1 cells against them. We evaluated phagocytosis, reactive oxygen species (ROS) formation, and CD11b activation, and performed RNA sequencing analyses. Our study revealed that dexmedetomidine improved Gram-positive but mitigated Gram-negative bacterial phagocytosis and killing in THP-1 cells. The attenuation of Toll-like receptor 4 (TLR4) signaling by dexmedetomidine was previously reported. Thus, we tested TLR4 inhibitor TAK242. Similar to dexmedetomidine, TAK242 reduced E. coli phagocytosis but enhanced CD11b activation. The reduced TLR4 response potentially increases CD11b activation and ROS generation and subsequently enhances Gram-positive bacterial killing. Conversely, dexmedetomidine may inhibit the TLR4-signaling pathway and mitigate the alternative phagocytosis pathway induced by TLR4 activation through LPS-mediated Gram-negative bacteria, resulting in worsened bacterial loads. We also examined another α2 adrenergic agonist, xylazine. Because xylazine did not affect bacterial clearance, we proposed that dexmedetomidine may have an off-target effect on bacterial killing process, potentially involving crosstalk between CD11b and TLR4. Despite its potential to attenuate inflammation, we provide a novel insight into potential risks of dexmedetomidine use during Gram-negative infections, highlighting the differential effect of dexmedetomidine on Gram-positive and Gram-negative bacteria.

2023 American Society of Anesthesiologists Practice Guidelines for Preoperative Fasting: Carbohydrate-containing Clear Liquids with or without Protein, Chewing Gum, and Pediatric Fasting Duration-A Modular Update of the 2017 American Society of Anesthesiologists Practice Guidelines for Preoperative Fasting

These practice guidelines are a modular update of the "Practice guidelines for preoperative fasting and the use of pharmacologic agents to reduce the risk of pulmonary aspiration: Application to healthy patients undergoing elective procedures." The guidance focuses on topics not addressed in the previous guideline: ingestion of carbohydrate-containing clear liquids with or without protein, chewing gum, and pediatric fasting duration.

Testosterone attenuates sevoflurane-induced tau phosphorylation and cognitive impairment in neonatal male mice

BACKGROUND

Sevoflurane anaesthesia induces phosphorylation of the microtubule-associated protein tau and cognitive impairment in neonatal, but not adult, mice. The underlying mechanisms remain largely to be determined. Sex hormones can be neuroprotective, but little is known about the influence of testosterone on age-dependent anaesthesia effects.

METHODS

Six- and 60-day-old male mice received anaesthesia with sevoflurane 3% for 2 h daily for 3 days. Morris water maze, immunoassay, immunoblotting, co-immunoprecipitation, nanobeam technology, and electrophysiology were used to assess cognition; testosterone concentrations; tau phosphorylation; glycogen synthase kinase-3β (GSK3β) activation; binding or interaction between tau and GSK3β; and neuronal activation in mice, cells, and neurones.

RESULTS

Compared with 60-day-old male mice, 6-day-old male mice had lower testosterone concentrations (3.03 [0.29] vs 0.44 [0.12] ng ml^-1; P<0.01), higher sevoflurane-induced tau phosphorylation in brain (133 [20]% vs 100 [6]% in 6-day-old mice, P<0.01; 103 [8]% vs 100 [13]% in 60-day-old mice, P=0.77), and sevoflurane-induced cognitive impairment. Testosterone treatment increased brain testosterone concentrations (1.76 [0.10] vs 0.39 [0.05] ng ml^-1; P<0.01) and attenuated the sevoflurane-induced tau phosphorylation and cognitive impairment in neonatal male mice. Testosterone inhibited the interaction between tau and GSK3β, and attenuated sevoflurane-induced inhibition of excitatory postsynaptic currents in hippocampal neurones.

CONCLUSIONS

Lower brain testosterone concentrations in neonatal compared with adult male mice contributed to age-dependent tau phosphorylation and cognitive impairment after sevoflurane anaesthesia. Testosterone might attenuate the sevoflurane-induced tau phosphorylation and cognitive impairment by inhibiting the interaction between tau and GSK3β.

Anesthetics isoflurane and sevoflurane attenuate flagellin-mediated inflammation in the lung

Isoflurane and sevoflurane are volatile anesthetics (VA) widely used in clinical practice to provide general anesthesia. We and others have previously shown that VAs have immunomodulatory effects and may have a significant impact on the progression of disease states. Flagellin is a component of Gram negative bacteria and plays a significant role in the pathophysiology of bacterial pneumonia through its binding to Toll-like Receptor 5 (TLR5). Our results showed that VAs, not an intravenous anesthetic, significantly attenuated the activation of TLR5 and the release of the neutrophil chemoattractant IL-8 from lung epithelial cells. Furthermore, flagellin-induced lung injury was significantly attenuated by VAs by inhibiting neutrophil migration to the bronchoalveolar space. The lungs of cystic fibrosis (CF) patients are highly colonized by Pseudomonas aeruginosa, which causes inflammation. The retrospective study of oxygenation in patients with CF who had received VA versus intravenous anesthesia suggested that VAs might have the protective effect for gas exchange. To understand the interaction between VAs and TLR5, a docking simulation was performed, which indicated that isoflurane and sevoflurane docked into the binding interphase between TLR5 and flagellin.

Risk factors for pediatric surgical site infection following neurosurgical procedures for hydrocephalus: a retrospective single-center cohort study

Background

Infection is a major complication following cerebral spinal fluid (CSF) diversion procedures for hydrocephalus. However, pediatric risk factors for surgical site infection (SSI) are currently not well defined. Because a SSI prevention bundle is increasingly introduced, the purpose of this study was to evaluate risk factors associated with SSIs following CSF diversion surgeries following a SSI bundle at a single quaternary care pediatric hospital.

Methods

We performed a retrospective cohort study of patients undergoing CSF diversion procedures from 2017 to 2019. SSIs were identified prospectively through continuous surveillance. We performed unadjusted logistic regression analyses and univariate analyses to determine an association between SSIs and patient demographics, comorbidities and perioperative factors to identify independent risk factors for SSI.

Results

We identified a total of 558 CSF diversion procedures with an overall SSI rate of 3.4%. The SSI rates for shunt, external ventricular drain (EVD) placement, and endoscopic third ventriculostomy (ETV) were 4.3, 6.9 and 0%, respectively. Among 323 shunt operations, receipt of clindamycin as perioperative prophylaxis and presence of cardiac disease were significantly associated with SSI (O.R. 4.99, 95% C.I. 1.27–19.70, p = 0.02 for the former, and O.R. 7.19, 95% C.I. 1.35–38.35, p = 0.02 for the latter). No risk factors for SSI were identified among 72 EVD procedures.

Conclusion

We identified receipt of clindamycin as perioperative prophylaxis and the presence of cardiac disease as risk factors for SSI in shunt procedures. Cefazolin is recommended as a standard antibiotic for perioperative prophylaxis. Knowing that unsubstantiated beta-lactam allergy label is a significant medical problem, efforts should be made to clarify beta-lactam allergy status to maximize the number of patients who can receive cefazolin for prophylaxis before shunt placement. Further research is needed to elucidate the mechanism by which cardiac disease may increase SSI risk after shunt procedures.

Vaping and E-Cigarette Use in Children and Adolescents: Implications on Perioperative Care From the American Society of Anesthesiologists Committee on Pediatric Anesthesia, Society for Pediatric Anesthesia, and American Academy of Pediatrics Section on Anesthesiology and Pain Medicine

Electronic cigarettes (e-cigarettes) or vaping use in adolescents has emerged as a public health crisis that impacts the perioperative care of this vulnerable population. E-cigarettes have become the most commonly used tobacco products among youth in the United States. Fruit and mint flavors and additives such as marijuana have enticed children and adolescents. E-cigarette, or vaping, product use-associated lung injury (EVALI) is a newly identified lung disease linked to vaping. Clinical presentation of EVALI can be varied, but most commonly includes the respiratory system, gastrointestinal (GI) tract, and constitutional symptoms. Clinical management of EVALI has consisted of vaping cessation and supportive therapy, including supplemental oxygen, noninvasive ventilation, mechanical ventilation, glucocorticoids, and empiric antibiotics, until infectious causes are eliminated, and in the most severe cases, extracorporeal membrane oxygenation (ECMO). Currently, although there is an insufficient evidence to determine the safety and the efficacy of e-cigarettes for perioperative smoking cessation, EVALI clearly places these patients at an increased risk of perioperative morbidity. Given the relatively recent introduction of e-cigarettes, the long-term impact on adolescent health is unknown. As a result, the paucity of postoperative outcomes in this potentially vulnerable population does not support evidence-based recommendations for the management of these patients. Clinicians should identify "at-risk" individuals during preanesthetic evaluations and adjust the risk stratification accordingly. Our societies encourage continued education of the public and health care providers of the risks associated with vaping and nicotine use and encourage regular preoperative screening and postoperative outcome studies of patients with regard to smoking and vaping use.

Dexmedetomidine and Clonidine Attenuate Sevoflurane-Induced Tau Phosphorylation and Cognitive Impairment in Young Mice via α-2 Adrenergic Receptor

BACKGROUND

Anesthetic sevoflurane induces tau phosphorylation and cognitive impairment in young mice. The underlying mechanism and the targeted interventions remain largely unexplored. We hypothesized that dexmedetomidine and clonidine attenuated sevoflurane-induced tau phosphorylation and cognitive impairment by acting on α-2 adrenergic receptor.

METHODS

Six-day-old mice received anesthesia with 3% sevoflurane 2 hours daily on postnatal days 6, 9, and 12. Alpha-2 adrenergic receptor agonist dexmedetomidine and clonidine were used to treat the mice with and without the α-2 adrenergic receptor antagonist yohimbine. Mouse hippocampi were harvested and subjected to western blot analysis. The New Object Recognition Test and Morris Water Maze were used to measure cognitive function. We analyzed the primary outcomes by using 2- and 1-way analysis of variance (ANOVA) and Mann-Whitney U test to determine the effects of sevoflurane on the amounts of phosphorylated tau, postsynaptic density-95, and cognitive function in young mice after the treatments with dexmedetomidine, clonidine, and yohimbine.

RESULTS

Both dexmedetomidine and clonidine attenuated the sevoflurane-induced increase in phosphorylated tau amount (94 ± 16.3% [dexmedetomidine plus sevoflurane] versus 240 ± 67.8% [vehicle plus sevoflurane], P < .001; 125 ± 13.5% [clonidine plus sevoflurane] versus 355 ± 57.6% [vehicle plus sevoflurane], P < .001; mean ± standard deviation), sevoflurane-induced reduction in postsynaptic density-95 (82 ± 6.6% [dexmedetomidine plus sevoflurane] versus 31 ± 12.4% [vehicle plus sevoflurane], P < .001; 95 ± 6.4% [clonidine plus sevoflurane] versus 62 ± 18.4% [vehicle plus sevoflurane], P < .001), and cognitive impairment in the young mice. Interestingly, yohimbine reversed the effects of dexmedetomidine and clonidine on attenuating the sevoflurane-induced changes in phosphorylated tau, postsynaptic density-95, and cognitive function.

CONCLUSIONS

Dexmedetomidine and clonidine could inhibit the sevoflurane-induced tau phosphorylation and cognitive impairment via activation of α-2 adrenergic receptor. More studies are needed to confirm the results and to determine the clinical relevance of these findings.

Mechanistic consideration of the effect of perioperative volatile anesthetics on phagocytes

A growing literature has shown that volatile anesthetics are promiscuous molecules targeting multiple molecules, some of which are critical for immunological functions. We focused on studies that delineated target molecules of volatile anesthetics on immune cells and summarized the effects of volatile anesthetics on immune functions. We also presented the perspectives of studying volatile anesthetics-mediated immunomodulation.

Interaction of Tau, IL-6 and mitochondria on synapse and cognition following sevoflurane anesthesia in young mice

Tau phosphorylation is associated with cognitive impairment in young mice. However, the underlying mechanism and targeted interventions remain mostly unknown. We set out to determine the potential interactions of Tau, interleukin 6 (IL-6) and mitochondria following treatment of anesthetic sevoflurane and to assess their influences on synapse number and cognition in young mice. Sevoflurane (3% for 2 ​h) was given to wild-type, Tau knockout, IL-6 knockout, and cyclophilin D (CypD) knockout mice on postnatal (P) day 6, 7 and 8. We measured amounts of phosphorylated Tau, IL-6, reactive oxygen species (ROS), mitochondrial membrane potential (MMP), ATP, postsynaptic density 95 (PSD-95), synaptophysin, N-cadherin, synapse number, and cognitive function in the mice, employing Western blot, electron microscope and Morris water maze among others. Here we showed that sevoflurane increased Tau phosphorylation and caused IL-6 elevation, mitochondrial dysfunction, synaptic loss and cognitive impairment in young wild-type, but not Tau knockout, mice. In young IL-6 knockout mice, sevoflurane increased Tau phosphorylation but did not cause mitochondrial dysfunction, synaptic loss or cognitive impairment. Finally, sevoflurane increased Tau phosphorylation and IL-6 amount, but did not induce synaptic loss and cognitive impairment, in young CypD knockout mice or WT mice pretreated with idebenone, an analog of co-enzyme Q10. In conclusion, sevoflurane increased Tau phosphorylation, which caused IL-6 elevation, leading to mitochondrial dysfunction in young mice. Such interactions caused synaptic loss and cognitive impairment in the mice. Idebenone mitigated sevoflurane-induced cognitive impairment in young mice. These studies would promote more research to study Tau in young mice.

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Research in context.•

Evidence before this studya.

Tau, a microtubule-associated protein that is predominantly expressed inside neurons, is associated with microtubule assembly and function. Tau phosphorylation, aggregation and spread all serve as the pathogenesis of age-dependent neurodegeneration in the old brain, as well as the neuropathogenesis of Alzheimer’s disease. However, the effects of Tau on the cellular changes and the function of the young brain are undetermined. Our previous studies showed that anesthetic sevoflurane induced Tau phosphorylation, IL-6 elevation, mitochondrial dysfunction and synaptic loss in brain tissues of neonatal mice, as well as cognitive impairment in the mice. However, the potential interactions of the Tau phosphorylation, IL-6 elevation and mitochondrial dysfunction and the influences of these interactions on synapse number and cognitive function in neonatal mice remains largely unknown.

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Added value of studyb.

Employing sevoflurane as a clinically relevant tool, and using the approaches including wild-type, Tau, IL-6, and CypD knockout neonatal mice, the present studies showed that Tau phosphorylation caused IL-6 elevation, which induced mitochondrial dysfunction, leading to synaptic loss and cognitive impairment in the neonatal mice. Idebenone, a synthetic analog of coenzyme Q10, mitigated the sevoflurane-induced cognitive impairment in the neonatal mice.

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Implications of all the available evidencec.

These findings demonstrated the role of Tau phosphorylation in cognitive impairment in neonatal mice, revealed the effects of the interactions of Tau phosphorylation, IL-6 elevation and mitochondrial dysfunction on the synapse number and cognitive function in the mice, and identified potential targeted intervention of the cognitive impairment in the neonatal mice.

Is Anesthesia Bad for the Brain? Current Knowledge on the Impact of Anesthetics on the Developing Brain

There are compelling preclinical data that common general anesthetics cause increased neuroapoptosis in juvenile animals. Retrospective studies demonstrate that young children exposed to anesthesia have school difficulties, which could be caused by anesthetic neurotoxicity, perioperative hemodynamic and homeostatic instability, underlying morbidity, or the neuroinflammatory effects of surgical trauma. Unnecessary procedures should be avoided. Baseline measures of blood pressure are important in determining perioperative blood pressure goals. Inadvertent hypocapnia or moderate hypercapnia and hyperoxia or hypoxia should be avoided. Pediatric patients should be maintained in a normothermic, euglycemic state with neutral positioning. Improving outcomes of infants and children requires the collaboration of anesthesiologists, surgeons, pediatricians and neonatologists.

Does general anesthesia affect neurodevelopment in infants and children?

General anesthesia has been unequivocally linked to abnormal development of the central nervous system, leading to neurocognitive impairments in laboratory models. In vitro and in vivo studies have consistently shown that exposure to GABA agonists (eg, volatile anesthetics, midazolam, and propofol) or NMDA antagonists (eg, ketamine, isoflurane, and nitrous oxide) produces dose dependent and developmental age dependent effects on various neuronal transmission systems. Exposure to these drugs increases neuronal cell death in juvenile animals including rats, mice, and non-human primates. The possibility of anesthetic induced neurotoxicity occurring in children has led to concerns about the safety of pediatric anesthesia. A spectrum of behavioral changes has been documented after general anesthetic exposure in young children, including emergence delirium, which may be evidence of toxicity. Most clinical studies are retrospective; specifics about medications or monitoring are unavailable and many of the outcomes may not be sensitive to detect small neurocognitive deficits. Some of these retrospective studies have shown an association between anesthesia exposure at a young age and neurocognitive deficits, but others have not. Practitioners and families should be reassured that although general anesthetics have the potential to induce neurotoxicity, very little clinical evidence exists to support this.

The volatile anesthetic sevoflurane reduces neutrophil apoptosis via Fas death domain-Fas-associated death domain interaction

Sepsis remains a significant health care burden, with high morbidities and mortalities. Patients with sepsis often require general anesthesia for procedures and imaging studies. Knowing that anesthetic drugs can pose immunomodulatory effects, it would be critical to understand the impact of anesthetics on sepsis pathophysiology. The volatile anesthetic sevoflurane is a common general anesthetic derived from ether as a prototype. Using a murine sepsis model induced by cecal ligation and puncture surgery, we examined the impact of sevoflurane on sepsis outcome. Different from volatile anesthetic isoflurane, sevoflurane exposure significantly improved the outcome of septic mice. This was associated with less apoptosis in the spleen. Because splenic apoptosis was largely attributed to the apoptosis of neutrophils, we examined the effect of sevoflurane on FasL-induced neutrophil apoptosis. Sevoflurane exposure significantly attenuated apoptosis. Sevoflurane did not affect the binding of FasL to the extracellular domain of Fas receptor. Instead, in silico analysis suggested that sevoflurane would bind to the interphase between Fas death domain (DD) and Fas-associated DD (FADD). The effect of sevoflurane on Fas DD-FADD interaction was examined using fluorescence resonance energy transfer (FRET). Sevoflurane attenuated FRET efficiency, indicating that sevoflurane hindered the interaction between Fas DD and FADD. The predicted sevoflurane binding site is known to play a significant role in Fas DD-FADD interaction, supporting our in vitro and in vivo apoptosis results.-Koutsogiannaki, S., Hou, L., Babazada, H., Okuno, T., Blazon-Brown, N., Soriano, S. G., Yokomizo, T., Yuki, K. The volatile anesthetic sevoflurane reduces neutrophil apoptosis via Fas death domain-Fas-associated death domain interaction.

Differences in Blood Pressure in Infants After General Anesthesia Compared to Awake Regional Anesthesia (GAS Study-A Prospective Randomized Trial)

BACKGROUND

The General Anesthesia compared to Spinal anesthesia (GAS) study is a prospective randomized, controlled, multisite, trial designed to assess the influence of general anesthesia (GA) on neurodevelopment at 5 years of age. A secondary aim obtained from the blood pressure data of the GAS trial is to compare rates of intraoperative hypotension after anesthesia and to identify risk factors for intraoperative hypotension.

METHODS

A total of 722 infants ≤60 weeks postmenstrual age undergoing inguinal herniorrhaphy were randomized to either bupivacaine regional anesthesia (RA) or sevoflurane GA. Exclusion criteria included risk factors for adverse neurodevelopmental outcome and infants born at <26 weeks of gestation. Moderate hypotension was defined as mean arterial pressure measurement of <35 mm Hg. Any hypotension was defined as mean arterial pressure of <45 mm Hg. Epochs were defined as 5-minute measurement periods. The primary outcome was any measured hypotension <35 mm Hg from start of anesthesia to leaving the operating room. This analysis is reported primarily as intention to treat (ITT) and secondarily as per protocol.

RESULTS

The relative risk of GA compared with RA predicting any measured hypotension of <35 mm Hg from the start of anesthesia to leaving the operating room was 2.8 (confidence interval [CI], 2.0-4.1; P < .001) by ITT analysis and 4.5 (CI, 2.7-7.4, P < .001) as per protocol analysis. In the GA group, 87% and 49%, and in the RA group, 41% and 16%, exhibited any or moderate hypotension by ITT, respectively. In multivariable modeling, group assignment (GA versus RA), weight at the time of surgery, and minimal intraoperative temperature were risk factors for hypotension. Interventions for hypotension occurred more commonly in the GA group compared with the RA group (relative risk, 2.8, 95% CI, 1.7-4.4 by ITT).

CONCLUSIONS

RA reduces the incidence of hypotension and the chance of intervention to treat it compared with sevoflurane anesthesia in young infants undergoing inguinal hernia repair.

Leukocyte function-associated antigen-1 deficiency impairs responses to polymicrobial sepsis

AIM: To determine the role of leukocyte function-associated antigen-1 (LFA-1) in polymicrobial sepsis model in mice.

METHODS: Cecal ligation and puncture model was used to study polymicrobial sepsis in wild type and LFA-1 knockout (KO) (= CD11a KO) mice. Their survivals were examined. Neutrophil recruitment to the abdominal cavity, bacterial tissue load and bacterial killing by neutrophils, tissue cytokine profiles, and serum cytokines were examined. Apoptosis of tissues was assessed using cleaved-caspase 3 and TUNNEL staining. The recruitment of neutrophils to various tissues was assessed using myeloperoxidase staining or measuring myeloperoxidase activity.

RESULTS: LFA-1 deficiency significantly decreased survival (P = 0.0024) with the reduction of neutrophil recruitment to the abdominal cavity and higher bacterial load in blood. It was also associated with increased apoptosis in spleen and more organ injuries probed by interleukin-6 mRNA level. However, the deficiency of LFA-1 did not prevent neutrophil recruitment to lung, liver, spleen or kidney, which suggested the existence of LFA-1 independent recruitment mechanism in these organs.

CONCLUSION: LFA-1 deficiency did not attenuate neutrophil recruitment to various organs to adequately mitigate secondary tissue injury in sepsis. It was associated with decreased neutrophil recruitment to the abdominal cavity, higher bacterial load, leading to increased mortality in an abdominal, polymicrobial sepsis.

Progress in anesthesia and management of the newborn surgical patient

Ongoing advances in the perioperative management of the newborn have undoubtedly decreased the incidence of morbidity and mortality of this vulnerable patient group. The introduction of new surgical techniques and more comprehensive understanding of the effects of varied anesthetic drugs and techniques on the surgical newborn present many challenges for pediatric surgeons and anesthesiologists. Thorough preoperative evaluation and open communication between members of the health care team are important. A basic understanding of age-dependent variables and the interaction of anesthetic and surgical procedures is essential in minimizing perioperative morbidity and mortality.

Anesthetic neurotoxicity

All routinely utilized sedatives and anesthetics have been found neurotoxic in a wide variety of animal species, including non-human primates. Neurotoxic effects observed in animals include histologic evidence for apoptotic neuronal cell death and subsequent learning and memory impairment. Several cohort studies in neonates with significant comorbidities requiring surgical procedures early in life have also demonstrated abnormal neurodevelopmental outcomes. This article provides an overview of the currently available data from both animal experiments and human clinical studies regarding the effects of sedatives and anesthetics on the developing brain.

Anaesthetic neurotoxicity and neuroplasticity: an expert group report and statement based on the BJA Salzburg Seminar

Although previously considered entirely reversible, general anaesthesia is now being viewed as a potentially significant risk to cognitive performance at both extremes of age. A large body of preclinical as well as some retrospective clinical evidence suggest that exposure to general anaesthesia could be detrimental to cognitive development in young subjects, and might also contribute to accelerated cognitive decline in the elderly. A group of experts in anaesthetic neuropharmacology and neurotoxicity convened in Salzburg, Austria for the BJA Salzburg Seminar on Anaesthetic Neurotoxicity and Neuroplasticity. This focused workshop was sponsored by the British Journal of Anaesthesia to review and critically assess currently available evidence from animal and human studies, and to consider the direction of future research. It was concluded that mounting evidence from preclinical studies reveals general anaesthetics to be powerful modulators of neuronal development and function, which could contribute to detrimental behavioural outcomes. However, definitive clinical data remain elusive. Since general anaesthesia often cannot be avoided regardless of patient age, it is important to understand the complex mechanisms and effects involved in anaesthesia-induced neurotoxicity, and to develop strategies for avoiding or limiting potential brain injury through evidence-based approaches.

β-Ionone arrests cell cycle of gastric carcinoma cancer cells by a MAPK pathway

β-Ionone is an end ring analog of β-carotenoid which has been shown to possess potent anti-proliferative activity both in vitro and in vivo. To investigate the possible inhibitory effects of β-ionone, we studied cell growth characteristics, DNA synthesis, cell cycle progression, as well as mitogen-activated protein kinases (MAPKs) pathways in the human gastric adenocarcinoma cancer cell line (SGC-7901). Our results show that cell growth and DNA synthesis were inhibited, and the cell cycle was arrested at the G0/G1 phase in a dose-dependent manner in cells treated with β-ionone (25, 50, 100 and 200 μmol/L) for 24 h. We found that the β-ionone significantly decreased the extracellular signal-regulated kinase protein expression and significantly increased the levels of p38 and Jun-amino-terminal kinase protein expression (P < 0.01). β-Ionone also inhibited cell cycle-related proteins of Cdk4, Cyclin B1, D1 and increased p27 protein expression in SGC-7901 cells. These results suggested that the cell cycle arrest observed may be regulated through a MAPK pathway by transcriptional down-regulation of cell cycle proteins. These results demonstrate potent ability of β-ionone to arrest cell cycle of SGC-7901 cells and decrease proliferation.

Perioperative central nervous system injury in neonates

Anaesthetic-induced developmental neurotoxicity (AIDN) has been clearly established in laboratory animal models. The possibility of neurotoxicity during uneventful anaesthetic procedures in human neonates or infants has led to serious questions about the safety of paediatric anaesthesia. However, the applicability of animal data to clinical anaesthesia practice remains uncertain. The spectre of cerebral injury due to cerebral hypoperfusion, metabolic derangements, coexisting disease, and surgery itself further muddles the picture. Given the potential magnitude of the public health importance of this issue, the clinician should be cognisant of the literature and ongoing investigations on AIDN, and raise awareness of the risks of both surgery and anaesthesia.

Morphine-enhanced apoptosis in selective brain regions of neonatal rats

Prolonged neonatal opioid exposure has been associated with: antinociceptive tolerance, long-term neurodevelopmental delay, cognitive, and motor impairment. Morphine has also been shown to induce apoptotic cell death in vitro studies, but its in vivo effect in developing rat brain is unknown. Thus, we hypothesized that prolongued morphine administration in neonatal rats in a model of antinociceptive tolerance and dependence is associated with increased neuroapoptosis. We analyzed neonatal rats from the following groups (1) naïve group (n=6); (2) control group (normal saline (NS), n=5), and (3) morphine group (n=8). Morphine sulfate or equal volume of NS was injected subcutaneously twice daily for 6½ days starting on postnatal day (PD) 1. Development of antinociceptive tolerance was previously confirmed by Hot Plate test on the 7th day. Evidence of neuronal and glial apoptosis was determined by cleaved caspase-3 immunofluorescence combined with specific markers. At PD7, morphine administration after 6½ days significantly increased the density of apoptotic cells in the cortex and amygdala, but not in the hippocampus, hypothalamus, or periaqueductal gray. Apoptotic cells exhibited morphology analogous to neurons. Irrespective of the treatment, only a very few individual microglia but not astrocytes were caspase-3 positive. In summary, repeated morphine administration in neonatal rats (PD1-7) is associated with increased supraspinal apoptosis in distinct anatomical regions known to be important for sensory (cortex) and emotional memory processing (amygdala). Brain regions important for learning (hippocampus), and autonomic and nociceptive processing (hypothalamus and periaqueductal gray) were not affected. Lack of widespread glial apoptosis or robust glial activation following repeated morphine administration suggests that glia might not be affected by chronic morphine at this early age. Future studies should investigate long-term behavioral sequelae of demonstrated enhanced apoptosis associated with prolonged morphine administration in a neonatal rat model.

Sedative drug modulates T-cell and lymphocyte function-associated antigen-1 function

BACKGROUND

Sedative drugs modify immune cell functions via several mechanisms. However, the effects of sedatives on immune function have been primarily investigated in neutrophils and macrophages, and to the lesser extent lymphocytes. Lymphocyte function-associated antigen-1 (LFA-1) is an adhesion molecule that has a central role in regulating immune function of lymphocytes including interleukin-2 (IL-2) production and lymphocyte proliferation. Previous clinical studies reported that propofol and isoflurane reduced IL-2 level in patients, but midazolam did not. We previously demonstrated that isoflurane inhibited LFA-1 binding to its counter ligand, intercellular adhesion molecule-1 (ICAM-1), which might contribute to the reduction of IL-2 levels. In the current study, we examined the effect of propofol, midazolam, and dexmedetomidine on LFA-1/ICAM-1 binding, and the subsequent biological effects.

METHODS

The effect of sedative drugs on T-cell proliferation and IL-2 production was measured by calorimetric assays on human peripheral blood mononuclear cells. Because LFA-1/ICAM-1 binding has an important role in T-cell proliferation and IL-2 production, we measured the effect of sedative drugs on ICAM-1 binding to LFA-1 protein (cell-free assay). This analysis was followed by flow cytometric analysis of LFA-1 expressing T-cell binding to ICAM-1 (cell-based assay). To determine whether the drug/LFA-1 interaction is caused by competitive or allosteric inhibition, we analyzed the sedative drug effect on wild-type and high-affinity LFA-1 and a panel of monoclonal antibodies that bind to different regions of LFA-1.

RESULTS

Propofol at 10 to 100 μM inhibited ICAM-1 binding to LFA-1 in cell-free assays and cell-based assays (P < 0.05). However, dexmedetomidine and midazolam did not affect LFA-1/ICAM-1 binding. Propofol directly inhibits LFA-1 binding to ICAM-1 by binding near the ICAM-1 contact area in a competitive manner. At clinically relevant concentrations, propofol, but not dexmedetomidine or midazolam, inhibited IL-2 production (P < 0.05). Additionally, propofol inhibited lymphocyte proliferation (P < 0.05).

CONCLUSIONS

Our study suggests that propofol competitively inhibits LFA-1 binding to ICAM-1 on T-cells and suppresses T-cell proliferation and IL-2 production, whereas dexmedetomidine and midazolam do not significantly influence these immunological assays.

Endoscopic strip craniectomy in early infancy: the initial five years of anesthesia experience

BACKGROUND

Minimally invasive endoscopic strip craniectomy (ESC) is a relatively new surgical technique for treating craniosynostosis in early infancy. In this study we reviewed our anesthesia experience with ESC. The hypothesis was that infants with low body weight and syndromes would have a higher risk of perioperative blood transfusion and that those with respiratory complications are more likely to be admitted to the intensive care unit (ICU).

METHODS

We retrospectively reviewed patient charts and anesthesia records of the first 100 consecutive infants who underwent ESC between May 2004 and December 2008 and follow-up evaluations until December 2009. Outcomes included (a) perioperative blood transfusion, (b) venous air embolism (VAE), (c) ICU admission, and (d) reoperation with craniofacial reconstruction procedures. Multivariable logistic regression was used to determine significant factors of patient outcomes.

RESULTS

Infants ranging from 4 to 34 weeks of age (weight: 3.2 to 10.1 kg), presented for 87 single and 13 multiple ESC. Four infants had a craniofacial syndrome. The mean surgical time was 48 minutes (range: 26 to 86 minutes). Ninety-two infants had a median estimated blood loss of 23 mL (interquartile ranges [IQR]: 15 to 30 mL). Eight infants who required blood transfusion received a median amount of 17.2 mL/kg (IQR: 10.1 to 21.2 mL/kg). Body weight ≤5 kg (P = 0.04), sagittal ESC (P < 0.01), syndromic craniosynostosis (P < 0.01), and earlier date of surgery in the series (P < 0.01) were factors associated with blood transfusion. VAE was detected in 2 infants with no changes in clinical outcome. Eight infants were admitted to the ICU. Factors associated with ICU admission were blood transfusion (P < 0.001) and respiratory complications (P < 0.001). Eighty-two infants were discharged on postoperative day 1 (range: 1 to 3 days). Six infants underwent subsequent fronto-orbital advancement and 1 cranial vault reconstruction. Multiple-suture craniosynostosis (P < 0.01), associated syndromes (P = 0.03), and ICU admission after ESC (P = 0.04) were predictive of reoperation.

CONCLUSIONS

Twenty percent of infants undergoing ESC had 1 or more of the following: need for blood transfusion, VAE, respiratory complications, and ICU admission. Multivariable analysis confirmed that patients with lower body weight, those with earlier date of surgery in the series, those undergoing sagittal ESC, and those with syndromic craniosynostosis had a higher rate of blood transfusion. ICU admissions often occurred in infants requiring transfusion and those with respiratory complications. Infants with multiple-suture craniosynostosis were more likely to require subsequent craniofacial reconstruction procedures.

Detection of intestinal inflammation by MicroPET imaging using a (64)Cu-labeled anti-beta(7) integrin antibody

BACKGROUND

The primary function of integrin beta(7) is the recruitment and retention of lymphocytes to the inflamed gut. The aim of this study was to investigate the possibility of imaging colitis radioimmunodetection by targeting the beta(7) integrin with a radiolabeled antibody.

METHODS

FIB504.64, a monoclonal antibody that binds to beta(7) integrin, was conjugated with a bifunctional chelator and labeled with (64)Cu. The antibody (50 microg, 7 MBq) was injected into C57BL/6 mice with experimentally induced colitis (n = 6). MicroPET images were collected at 1, 24, and 48 hours postinjection and the biodistribution was measured at 48 hours by tissue assay. Data were also obtained for a (64)Cu-labeled nonspecific isotype-matched antibody in mice with colitis and (64)Cu-labeled FIB504.64 in healthy mice (n = 5-6).

RESULTS

The microPET images showed higher uptake of (64)Cu-labeled FIB504.64 in the gut of mice with colitis than for either of the controls. This observation was confirmed by the 48-hour ex vivo biodistribution data: the percentage of injected dose per gram of tissue (%ID/g +/- SD) (large intestine) colitis mice with (64)Cu-labeled FIB504.64, 6.49 +/- 2.25; control mice with (64)Cu-labeled FIB504.64, 3.64 +/- 1.12; colitis mice, (64)Cu-labeled nonspecific antibody 3.97 +/- 0.48%ID/g (P < 0.05 between groups).

CONCLUSIONS

The selective uptake of (64)Cu-labeled FIB504.64 antibody in the gut of animals with colitis suggests that integrin beta(7) may be a promising target for radioimmunodetection of this disease, which would aid diagnosis, assessment, and therapy guidance of this disease.

Acute intraoperative neurogenic pulmonary edema during endoscopic ventriculoperitoneal shunt revision

We present an incident of fulminant intraoperative neurogenic pulmonary edema in a 21-yr-old man undergoing an endoscopic ventriculoperitoneal shunt revision. His intraoperative course was complicated by intracranial bleeding requiring vigorous saline irrigation, which was accompanied by an acute increase in heart rate and arterial blood pressure. Shortly thereafter, the patient developed pulmonary edema and was promptly treated with resolution of pulmonary symptoms within 24 h. This report addresses the importance of recognition of neurogenic pulmonary edema as a possible intraoperative complication resulting from an increase in intracranial pressure due to hemorrhage and intraventricular irrigation during endoscopic ventriculoperitoneal shunt revision.

Is anesthesia bad for the newborn brain?

Although certain data suggest that common general anesthetics may be neurotoxic to immature animals, there are also data suggesting that these same anesthetics may be neuroprotective against hypoxicischemic injury, and that inadequate analgesia during painful procedures may lead to increased neuronal cell death in animals and long-term behavioral changes in humans. The challenge for the pediatric anesthesia community is to design and implement studies in human infants to ascertain the safety of general anesthesia. In this article, the authors review the relevant preclinical and clinical data that are currently available on this topic.

Prolonged exposure to ketamine increases brain derived neurotrophic factor levels in developing rat brains

Prolonged exposure to ketamine, a NMDA receptor antagonist, results in accelerated neurodegeneration and attenuated weight gain in neonatal rats. Suppression of the NMDA receptors by non-competitive antagonists has resulted in conflicting reports of both increased and decreased expression of BDNF. To examine the effect of prolonged ketamine exposure on BDNF expression, we administered saline or ketamine (20 mg/kg) at 90-minute intervals over 9 hours to postnatal day 7 (P7) rat pups. The ketamine-treated rat pups had increased neurodegeneration, BDNF and TrkB cDNA products and protein levels. This increased expression of BDNF may be a response to ketamine-induced injury.

Clinical research approaches to studying pediatric anesthetic neurotoxicity

Neuronal cell death after general anesthesia has recently been demonstrated in neonatal animal models. The possibility of anesthesia-induced neurotoxicity during an uneventful anesthetic procedure in human neonates or infants has led to serious questions about the safety of pediatric anesthesia. However, the applicability of animal data to clinical anesthesia practice remains uncertain. This paper examines the evidence for the effects of commonly used anesthetics on neuronal structure and neurocognitive function in laboratory models and evaluates its relevance to clinical care in humans. Published retrospective reviews demonstrate temporary neurological sequelae after prolonged anesthetic exposure in young children and larger studies identify long-term neurodevelopmental impairment after neonatal surgery and anesthesia. However, there are no prospective studies evaluating neurocognitive function in children after neonatal exposure to anesthetics. Given the potential magnitude of the public health importance of this issue, this review also discusses epidemiological approaches and several ongoing prospective studies that are assessing the long-term neurocognitive effects of general anesthesia on the neonate.

The volatile anesthetic isoflurane perturbs conformational activation of integrin LFA-1 by binding to the allosteric regulatory cavity

The molecular and structural basis of anesthetic interactions with conformations and functionalities of cell surface receptors remains to be elucidated. We have demonstrated that the widely used volatile anesthetic isoflurane blocks the activation-dependent conformational conversion of integrin lymphocyte function associated antigen-1 (LFA-1), the major leukocyte cell adhesion molecule, to a high-affinity configuration. Perturbation of LFA-1 activation by isoflurane at clinically relevant concentrations leads to the inhibition of T-cell interactions with target cells as well as ligand-triggered intracellular signaling. Nuclear magnetic resonance spectroscopy reveals that isoflurane binds within a cavity in the LFA-1 ligand-binding domain, which is a previously identified drug-binding site for allosteric small-molecule antagonists that stabilize LFA-1 in a low-affinity conformation. These results provide a potential mechanism for the immunomodulatory properties of isoflurane.

Detection of unanticipated intracranial hemorrhage during intraoperative magnetic resonance image-guided neurosurgery. Report of two cases

The authors report unanticipated intraoperative intracranial hemorrhaging in two pediatric neurosurgical patients. Both children were undergoing elective craniotomies with the aid of intraoperative magnetic resonance (iMR) imaging. In both cases, the ability of iMR imaging to aid in diagnosis allowed prompt and definitive treatment of potentially life-threatening complications. These cases illustrate the ability of iMR imaging to aid in differentiating unexpected and/or unexplained intraoperative events in pediatric neurosurgery.

Pediatric Neuroanesthesia

Recent advances in pediatric neurosurgery have drastically improved the outcome in infants and children afflicted with surgical lesions of the central nervous system (CNS). Because most of these techniques were first applied to adults, the physiologic and developmental differences that are inherent in pediatric patients present challenges to neurosurgeons and anesthesiologists alike. The aim of this paper is to highlight these age-dependent approaches to the pediatric neurosurgical patient.

Lidocaine pretreatment for the prevention of propofol-induced transient motor disturbances in children during anesthesia induction: a randomized controlled trial in children undergoing invasive hematologic procedures

BACKGROUND

We examined the effect of lidocaine pretreatment before propofol administration on the incidence of transient motor disturbances and on propofol requirements for anesthesia induction in infants and children undergoing repeated painful diagnostic and therapeutic hematological procedures.

METHODS

A series of 358 children subgrouped according to the presence of a peripheral-vein or central venous catheter were randomly assigned to receive an intravenous dose of 2% lidocaine (2.0 mg.kg(-1)) or an equivalent volume of saline, 1 min before propofol (1.5-3.5 mg.kg(-1)) injected for anesthesia induction.

RESULTS

The incidence of spontaneous movements was significantly lower in patients pretreated with lidocaine than in those receiving placebo (2.5% vs 29%; P < 0.001, by chi-square test), as was the propofol induction dose (1.6 +/- 0.2 mg.kg(-1) vs 2.2 +/- 0.3 mg.kg(-1); P < 0.001) and pain at the injection site in patients peripheral-vein catheter (12% vs. 54%; P < 0.001). Lidocaine administration also improved children's acceptance as reported by parents on the Observational Scale of Behavioral Distress administered 2 h after the procedure (6.5 +/- 2.5 vs. 9.4 +/- 3.3; P < 0.001). Bouts of coughing developed significantly more frequently after lidocaine pretreatment than after placebo (62.5% vs. 17.5%; P < 0.001).

CONCLUSIONS

Because lidocaine pretreatment before the induction of propofol-based anesthesia decreases propofol-induced motor disturbances, lowers hypnotic requirements and reduces pain at the injection site, without inducing untoward events, thus improving children's and parental acceptance, it should become standard practice in infants and children undergoing repeated painful diagnostic and therapeutic hematological procedures.

Anesthesia for epilepsy surgery in children

BACKGROUND

The perioperative management of infants and children for epilepsy surgery should focus on the specific problems unique to the state of the disease, age of the child, and operative conditions. A basic understanding of age-dependent variables and the interaction of anesthetic and surgical procedures are essential in minimizing perioperative morbidity and mortality. Specific medical conditions that impact the conduct of anesthesia include congenital anomalies, chronic anticonvulsant therapies, and evolving coagulopathies. The neurosurgical procedure and neurophysiological monitoring will determine the type of anesthetic technique to be utilized during surgery.

OBJECTIVE

This review will provide a systematic approach to pediatric patients undergoing epilepsy surgery.

Anesthesia and analgesia during and after surgery in neonates

BACKGROUND

Historically, the use of anesthetics and analgesics in neonates and infants has been based on extrapolations from studies performed in adults and older children. Over the past 20 years, there has been a growing body of research on the clinical pharmacology and clinical outcomes of these agents in neonates and infants.

OBJECTIVE

This article summarizes clinical pharmacology and clinical outcomes studies of opioids, opioid antagonists, sedative-hypnotics, nonsteroidal anti-inflammatory drugs and acetaminophen, and local anesthetics in neonates and infants to highlight gaps in the available knowledge, review some concerns about study design, and identify drugs that should receive high priority for future study.

METHODS

Relevant studies were identified through a search of MEDLINE and a review of textbooks, conference proceedings, and abstracts. The available literature was subjected to expert committee-based review.

CONCLUSIONS

There is a growing body of information on analgesic and anesthetic pharmacokinetics, pharmacodynamics, and clinical outcomes in neonates and infants, permitting safe and effective use in some clinical settings. Major gaps in knowledge persist, however. Future research may involve a combination of clinical trials and preclinical studies in suitable infant animal surrogate models.

Anesthetics and brain toxicity

PURPOSE OF REVIEW

Recent experimental data from rodent studies have demonstrated accelerated neurodegeneration in rat pups exposed to commonly used anesthetic drugs. These provocative findings certainly question and undermine the safe use of anesthetic drugs, particularly in pediatric anesthesia, and have prompted many to investigate the neurotoxic effect of anesthetic drugs on the developing brain. This review will address the scientific evidence for the anesthetic-induced neurotoxicity and its applicability in humans.

RECENT FINDINGS

Several investigators have shown that prolonged administration of anesthetic drugs, including ketamine, isoflurane, nitrous oxide and midazolam, produced increased neurodegeneration in 7-day-old rat pups. The combination of the latter three drugs led to altered learning behavior in adulthood. Despite these unequivocal findings in rodents, similar changes cannot be reproduced in other species. Furthermore, withholding anesthesia during painful procedures in neonatal rats resulted in significant long-term aberrant responses to sensory stimulation and pain thresholds.

SUMMARY

Taken together, these studies question the applicability of these data to the anesthetic management of the neonate. Further investigations in this area are needed before withholding anesthetics in the anesthetic management of pediatric surgical patients.

Summary proceedings from the neonatal pain-control group

Recent advances in neurobiology and clinical medicine have established that the fetus and newborn may experience acute, established, and chronic pain. They respond to such noxious stimuli by a series of complex biochemical, physiologic, and behavioral alterations. Studies have concluded that controlling pain experience is beneficial with respect to short-term and perhaps long-term outcomes. Yet, pain-control measures are adopted infrequently because of unresolved scientific issues and lack of appreciation for the need for control of pain and its long-term sequelae during the critical phases of neurologic maturation in the preterm and term newborn. The neonatal pain-control group, as part of the Newborn Drug Development Initiative (NDDI) Workshop I, addressed these concerns. The specific issues addressed were (1) management of pain associated with invasive procedures, (2) provision of sedation and analgesia during mechanical ventilation, and (3) mitigation of pain and stress responses during and after surgery in the newborn infant. The cross-cutting themes addressed within each category included (1) clinical-trial designs, (2) drug prioritization, (3) ethical constraints, (4) gaps in our knowledge, and (5) future research needs. This article provides a summary of the discussions and deliberations. Full-length articles on procedural pain, sedation and analgesia for ventilated infants, perioperative pain, and study designs for neonatal pain research were published in Clinical Therapeutics (June 2005).

Anesthetic management of pial synangiosis and intracranial hemorrhage with a Fontan circulation

We report the case of a 11-year-old girl with Moyamoya syndrome, who had undergone staged-repair of tricuspid atresia to a Fontan circulation, scheduled to undergo bilateral pial synangiosis. Surgery for the first hemisphere was complicated by intracranial hemorrhage requiring an emergency craniotomy. The case highlights the importance of understanding Fontan physiology and its interrelationship with the cerebral circulation in the setting of cerebrovascular insufficiency and raised intracranial pressure.