Cerebral haemodynamic changes during propofol-remifentanil or sevoflurane anaesthesia: transcranial Doppler study under bispectral index monitoring.

BACKGROUND: Sevoflurane or propofol-remifentanil-based anaesthetic regimens represent modern techniques for neurosurgical anaesthesia. Nevertheless, there are potential differences related to their activity on the cerebrovascular system. The magnitude of such difference is not completely known. METHODS: In total 40 patients, treated for spinal or maxillo-facial disorders, were randomly allocated to either i.v. propofol-remifentanil or inhalational sevoflurane anaesthesia. Transcranial Doppler was used to assess changes in cerebral blood flow velocity, carbon dioxide reactivity, cerebral autoregulation and the bispectral index to assess the depth of anaesthesia. RESULTS: Time-averaged mean flow velocity (MFV) was significantly reduced after induction of anaesthesia in both sevoflurane and propofol-remifentanil groups (P<0.001). At deeper levels of anaesthesia, MFV increased in the sevoflurane group, suggesting an uncoupling flow/metabolism, whereas it was further reduced in the propofol-remifentanil group (P<0.001). Indices of cerebral autoregulation were reduced in patients with high-dose sevoflurane whereas autoregulation was preserved in patients anaesthetized with propofol-remifentanil (P<0.001). Higher CO(2) concentrations impaired cerebral autoregulation in the sevoflurane group but not in patients anaesthetized with propofol-remifentanil. CONCLUSIONS: Propofol-remifentanil anaesthesia induced a dose-dependent low-flow state with preserved cerebral autoregulation, whereas sevoflurane at high doses provided a certain degree of luxury perfusion.

Significance of hypoxemia screening in candidates for liver transplantation: our experience.

Hepatopulmonary syndrome (HPS) is recognized as one of the causes of hypoxemia in patients with chronic liver disease. This complication is responsible for increased mortality and increased perioperative risk in liver transplantation candidates. Recent data from the literature suggest extending the screening for HPS to all candidates for liver transplantation. The aim of this retrospective study was to evaluate the incidence of hypoxemia among a population of patients awaiting liver transplantation. Using pulse oximetry as a screening tool for hypoxemia, 39 of 198 patients (20%) were hypoxemic. The results of this study confirmed the importance of screening for hypoxemia among patients awaiting liver transplantation. In these patients, a more accurate evaluation of respiratory function should be performed to confirm or exclude the diagnosis of HPS.

Drugs of anesthesia acting on central cholinergic system may cause post-operative cognitive dysfunction and delirium.

Given the progressive and constant increase of average life expectancy, an increasing number of elderly patients undergo surgery. After surgery, elderly patients often exhibit a transient reversible state of cerebral cognitive alterations. Among these cognitive dysfunctions, a state of delirium may develop. Delirium is an aetiologically non-specific syndrome characterised by concurrent disturbances of consciousness and attention, perception, thinking, memory, psychomotor behaviour and the sleep-wake cycle. Delirium appears to occur in 10-26% of general medical patients over 65, and is frequently associated with a significant increase in morbidity and mortality. During hospitalization, mortality rates have been estimated to be 10-26% of patients who developed post-operative delirium, and 22-76% during the following months. Over the last few decades, post-operative delirium has been associated with several pre-operative predictor factors, as well as age (50 years and older), alcohol abuse, poor cognitive and functional status, electrolyses or glucose abnormalities, and type of surgery. The uncertain pathogenesis of post-operative cognitive dysfunctions and delirium has not permitted a causal approach to developing an effective treatment. General anesthesia affects brain function at all levels, including neuronal membranes, receptors, ion channels, neurotransmitters, cerebral blood flow and metabolism. The functional equivalents of these impairments involve mood, memory, and motor function behavioural changes. These dysfunctions are much more evident in the occurrence of stress-regulating transmission and in the alteration of intra-cellular signal transduction systems. In addition, more essential cellular processes, that play an important role in neurotransmitter synthesis and release, such as intra-neuronal signal transduction and second messenger system, may be altered. Keeping in mind the functions of the central muscarinic cholinergic system and its multiple interactions with drugs of anesthesia, it seems possible to hypothesize that the inhibition of muscarinic cholinergic receptors could have a pivotal role in the pathogenesis not only of post-operative delirium but also the more complex phenomena of post-operative cognitive dysfunction.

Assessment of peri-neonatal mortality and morbidity risk in twin pregnancy.

A case control study on peri-neonatal mortality and morbidity rates in 154 twin pregnancies has been performed. The mortality rates along with main neonatal morbidity factors were evaluated in relation to the birth weight and gestational age. The risk of death in peri-neonatal period was 17 times greater (relative risk 17.30) (p less than .00005) in newborns weighing less than 2000 g and about 15 times (r.r. 14.53) (p less than .00005) in twins born before 34th week of gestational age with respect to the controls. The Apgar score of the 2nd twin was lower than that of the 1st, both at 1' (p less than .05) and 5' (p less than .025). The development of HMD was strongly influenced by the gestational age when less than 34th week (r.r. 15.89) (p less than .00005). No difference in incidence was found between the newborns with gestational age between 34-37 weeks and those at term. The potential implications of these findings on obstetric and neonatologic treatment of LBW and VLBW twins was discussed.