Effects of propofol on cerebral hemodynamics and metabolism in patients with brain trauma

Comparison of the effect of sevoflurane and propofol on the optic nerve sheath diameter in patients undergoing middle ear surgery

PURPOSE

During middle ear surgery, the patient's head is turned away from the surgical site, which may increase the intracranial pressure. Anesthetics also affect the intracranial pressure. The optic nerve sheath diameter (ONSD) measured using ultrasonography is a reliable marker for estimating the intracranial pressure. This aim of this study was to investigate the effect of sevoflurane and propofol on the ONSD in patients undergoing middle ear surgery.

METHODS

Fifty-eight adult patients were randomized into sevoflurane group (n = 29) or propofol group (n = 29). The ONSD was measured using ultrasound after anesthesia induction before head rotation (T0), and at the end of surgery (T1). The occurrence and severity of postoperative nausea and vomiting (PONV) were assessed 1 h after the surgery.

RESULTS

The ONSD was significantly increased from T0 to T1 in the sevoflurane group [4.3 (0.5) mm vs. 4.9 (0.6) mm, respectively; P < 0.001] and the propofol group [4.2 (0.3) mm vs. 4.8 (0.5) mm, respectively; P < 0.001]. No significant difference was observed in the ONSD at T0 (P = 0.267) and T1 (P = 0.384) between the two groups. The change in the ONSD from T0 to T1 was not significantly different between the sevoflurane and propofol groups [0.6 (0.4) mm vs. 0.6 (0.3) mm, respectively; P = 0.972]. The occurrence and severity of PONV was not significantly different between the sevoflurane and propofol groups (18% vs. 0%, respectively; P = 0.053).

CONCLUSION

The ONSD was significantly increased during middle ear surgery. No significant difference was observed in the amount of ONSD increase between the sevoflurane and propofol groups.

The impact of sedative and vasopressor agents on cerebrovascular reactivity in severe traumatic brain injury

BACKGROUND

The aim of this study is to evaluate the impact of commonly administered sedatives (Propofol, Alfentanil, Fentanyl, and Midazolam) and vasopressor (Dobutamine, Ephedrine, Noradrenaline and Vasopressin) agents on cerebrovascular reactivity in moderate/severe TBI patients. Cerebrovascular reactivity, as a surrogate for cerebral autoregulation was assessed using the long pressure reactivity index (LPRx). We evaluated the data in two phases, first we assessed the minute-by-minute data relationships between different dosing amounts of continuous infusion agents and physiological variables using boxplots, multiple linear regression and ANOVA. Next, we assessed the relationship between continuous/bolus infusion agents and physiological variables, assessing pre-/post- dose of medication change in physiology using a Wilcoxon signed-ranked test. Finally, we evaluated sub-groups of data for each individual dose change per medication, focusing on key physiological thresholds and demographics.

RESULTS

Of the 475 patients with an average stay of 10 days resulting in over 3000 days of recorded information 367 (77.3%) were male with a median Glasgow coma score of 7 (4-9). The results of this retrospective observational study confirmed that the infusion of most administered agents do not impact cerebrovascular reactivity, which is confirmed by the multiple linear regression components having p value > 0.05. Incremental dose changes or bolus doses in these medications in general do not lead to significant changes in cerebrovascular reactivity (confirm by Wilcoxon signed-ranked p value > 0.05 for nearly all assessed relationships). Within the sub-group analysis that separated the data based on LPRx pre-dose, a significance between pre-/post-drug change in LPRx was seen, however this may be more of a result from patient state than drug impact.

CONCLUSIONS

Overall, this study indicates that commonly administered agents with incremental dosing changes have no clinically significant influence on cerebrovascular reactivity in TBI (nor do they impair cerebrovascular reactivity). Though further investigation in a larger and more diverse TBI patient population is required.

Management of Severe Traumatic Brain Injury in Pediatric Patients

The optimal management of severe traumatic brain injury (TBI) in the pediatric population has not been well studied. There are a limited number of research articles studying the management of TBI in children. Given the prevalence of severe TBI in the pediatric population, it is crucial to develop a reference TBI management plan for this vulnerable population. In this review, we seek to delineate the differences between severe TBI management in adults and children. Additionally, we also discuss the known molecular pathogenesis of TBI. A better understanding of the pathophysiology of TBI will inform clinical management and development of therapeutics. Finally, we propose a clinical algorithm for the management and treatment of severe TBI in children using published data.

Sedation for Rapid Sequence Induction and Intubation of Neurologically Injured Patients

There are subtle physiologic and pharmacologic principles that should be understood for patients with neurologic injuries. These principles are especially true for managing patients with traumatic brain injuries. Prevention of hypotension and hypoxemia are major goals in the management of these patients. This article discusses the physiology, pitfalls, and pharmacology necessary to skillfully care for this subset of patients with trauma. The principles endorsed in this article are applicable both for patients with traumatic brain injury and those with spinal cord injuries.

Cerebrovascular Response to Propofol, Fentanyl, and Midazolam in Moderate/Severe Traumatic Brain Injury: A Scoping Systematic Review of the Human and Animal Literature

Intravenous propofol, fentanyl, and midazolam are utilized commonly in critical care for metabolic suppression and anesthesia. The impact of propofol, fentanyl, and midazolam on cerebrovasculature and cerebral blood flow (CBF) is unclear in traumatic brain injury (TBI) and may carry important implications, as care is shifting to focus on cerebrovascular reactivity monitoring/directed therapies. The aim of this study was to perform a scoping review of the literature on the cerebrovascular/CBF effects of propofol, fentanyl, and midazolam in human patients with moderate/severe TBI and animal models with TBI. A search of MEDLINE, BIOSIS, EMBASE, Global Health, SCOPUS, and the Cochrane Library from inception to May 2020 was performed. All articles were included pertaining to the administration of propofol, fentanyl, and midazolam, in which the impact on CBF/cerebral vasculature was recorded. We identified 14 studies: 8 that evaluated propofol, 5 that evaluated fentanyl, and 2 that evaluated midazolam. All studies suffered from significant limitations, including: small sample size, and heterogeneous design and measurement techniques. In general, there was no significant change seen in CBF/cerebrovascular response to administration of propofol, fentanyl, or midazolam during experiments where PCO₂ and mean arterial pressure (MAP) were controlled. This review highlights the current knowledge gap surrounding the impact of commonly utilized sedative drugs in TBI care. This work supports the need for dedicated studies, both experimental and human-based, evaluating the impact of these drugs on CBF and cerebrovascular reactivity/response in TBI.

Neurologic Considerations and Complications Related to Liver Transplantation

Neurologic complications of surgery can be devastating. The authors review neurologic considerations and complications associated with liver transplantation and discuss strategies to prevent, identify, and treat such adverse outcomes in the perioperative period.

Acute Management of Hypertension Following Intracerebral Hemorrhage

Intracerebral hemorrhage (ICH) is responsible for approximately 15% of strokes annually in the United States, with nearly 1 in 3 of these patients dying without ever leaving the hospital. Because this disproportionate mortality risk has been stagnant for nearly 3 decades, a main area of research has been focused on the optimal strategies to reduce mortality and improve functional outcomes. The acute hypertensive response following ICH has been shown to facilitate ICH expansion and is a strong predictor of mortality. Rapidly reducing blood pressure was once thought to induce cerebral ischemia, though has been found to be safe in certain patient populations. Clinicians must work quickly to determine whether specific patient populations may benefit from acute lowering of systolic blood pressure (SBP) following ICH. This review provides nurses with a summary of the available literature on blood pressure control following ICH. It focuses on intravenous and oral antihypertensive medications available in the United States that may be utilized to acutely lower SBP, as well as medications outside of the antihypertensive class used during the acute setting that may reduce SBP.

Perioperative Management of Severe Traumatic Brain Injury: What Is New?

PURPOSE OF THE REVIEW

Severe traumatic brain injury (TBI) continues to represent a global public health issue, and mortality and morbidity in TBI patients remain substantial. There are ongoing international collaborations to provide guidelines for perioperative care and management of severe TBI patients. In addition, new pharmacologic agents are being tested along with cognitive rehabilitation to improve functional independence and outcome in TBI patients. This review will discuss the current updates in the guidelines for the perioperative management of TBI patients and describe potential new therapies to improve functional outcomes.

RECENT FINDINGS

In the most recent guidelines published by The Brain Trauma Foundation, therapeutic options were reviewed based on new and revised evidence or lack of evidence. For example, changes and/or updates were made to the recommendations for the use of sedation and hypothermia in TBI patients, and new evidence was provided for the use of cerebrospinal fluid drainage as a first-line treatment for increased intracranial pressure (ICP). In addition to the guidelines, new 'multi-potential' agents that can target several mechanisms are being tested along with cognitive rehabilitation.

SUMMARY

The major goal of perioperative management of TBI patients is to prevent secondary damage. Therapeutic measures based on established guidelines and recommendations must be instituted promptly throughout the perioperative course to reduce morbidity and mortality.

Predicting the Occurrence of Hemorrhagic Cerebral Hyperperfusion Syndrome Using Regional Cerebral Blood Flow After Direct Bypass Surgery in Patients with Moyamoya Disease

OBJECTIVE

Superficial temporal artery-middle cerebral artery anastomosis is an established treatment for moyamoya disease. However, hemorrhagic cerebral hyperperfusion syndrome (CHS) leads to poor outcomes. This study aimed to identify predictors of hemorrhagic CHS based on regional cerebral blood flow (rCBF) in patients with moyamoya disease.

METHODS

The study included 251 hemispheres in 155 patients with moyamoya disease who underwent preoperative and postoperative rCBF measurements and superficial temporal artery-middle cerebral artery double anastomosis. We used rCBF increase rate for predicting hemorrhagic CHS. rCBF increase rate was calculated by 2 methods. In method 1, the rCBF value on the operated side was compared with the rCBF value on the nonoperated side. In method 2, the postoperative rCBF value on the operated side was compared with the preoperative rCBF value on the operated side. Patients were classified into 4 groups according to rCBF increase rate to predict risk of hemorrhagic CHS.

RESULTS

Hemorrhagic CHS occurred in 7 (2.8%) hemispheres (no children). Severe hemorrhagic CHS occurred in only 1 (0.4%) hemisphere. Hemorrhagic CHS was observed in patients with ≥30% rCBF increase according to method 1 and ≥50% rCBF increase according to method 2 and was most frequently noted in ≥100% rCBF increase.

CONCLUSIONS

Predictors for hemorrhagic CHS were ≥30% rCBF increase when using method 1 and ≥50% increase when using method 2.

A randomised trial to compare the increase in intracranial pressure as correlated with the optic nerve sheath diameter during propofol versus sevoflurane-maintained anesthesia in robot-assisted laparoscopic pelvic surgery

Robot-assisted surgery can cause raised intracranial pressures (ICP) due to steep trendelenburg position and pneumoperitoneum. The choice of anesthetic agents can influence the ICP, which can be measured indirectly by correlating it with the sonographically measured optic nerve sheath diameter (ONSD). In this study, our primary aim was to compare the change from baseline of the ONSD during propofol versus sevoflurane-maintained anesthesia in patients undergoing robotic pelvic surgery. In this prospective, interventional, double-blinded study, we randomised 50 patients into two groups P and S. Subjects in group P received intravenous propofol infusion while those in group S received inhalation sevoflurane for maintenance of anesthesia. The ONSD at fixed intervals was noted as the mean of four values measured using ultrasound in both eyes by two independent anesthesiologists who were blinded to the group allocation. The patient demographics and baseline parameters were similar. The mean maximum rise in ONSD from baseline was 0.01 ± 0.01 cm in group P while it was 0.03 ± 0.01 cm in group S (p = 0.001). Percentage change from baseline in group P was 3.41 ± 1.81% and 8.00 ± 2.95% in group S (p = 0.001). We found a positive correlation between the duration of surgery and the maximum rise in ONSD in group S (p = 0.003), but not in group P. Propofol-based total intravenous anesthesia is more effective than inhalation sevoflurane in attenuating the increase in ICP as correlated with the ONSD during robotic pelvic surgery.Clinical trial registration: Yes; Principal investigator: Nambiath Sujata; Trial number: REF/2016/11/012713 (registered); Trial registry: CTRI- http://ctri.nic.in .

Effect of Propofol on the Expression of MMP-9 and Its Relevant Inflammatory Factors in Brain of Rat with Intracerebral Hemorrhage

Intracerebral hemorrhage (ICH) is bleeding in brain caused by the rupture of brain blood vessel, which may lead to patient unconsciousness or death. In this study, we measured the expression of matrix metalloproteinase-9 (MMP-9) and its relevant inflammatory factors in the brain of rat with ICH. The effect of propofol on the expression of MMP-9 and inflammatory factors was investigated. We found the water content in the brain of ICH rats was significantly higher when compared with normal brain. Expression of MMP-9 and inflammatory factors IL-1β and TNF-α were up-regulated in ICH rats. Medium or high concentration of propofol can alleviate ICH in rats by inhibition of the inflammatory factor release and up-regulation of MMP-9 in brain. Our study suggests the inflammatory response after reduction of ICH through promotion of MMP-9 expression and neurite regeneration.

The effect of propofol infusion with topical epinephrine on cochlear blood flow and hearing: An experimental study

BACKGROUND AND OBJECTIVE

Propofol is the most commonly used intravenous (IV) anesthetic agent and is associated with hypotension upon induction of anesthesia. Intravenous propofol infusion has several properties that may be beneficial to patients undergoing middle ear surgery. Topical application of concentrated epinephrine is a valuable tool for achieving hemostasis in the middle ear and during mastoid surgery. The purpose of the present study was to determine the effects of propofol infusion with topical epinephrine on cochlear blood flow (CBF) and hearing in rats.

MATERIALS AND METHODS

Twenty one male Sprague-Dawley rats were divided into three groups. The rate of intravenous infusion of propofol was 4-6 ml/kg/hour. The first group (control group, n = 7) was given IV infusion of phosphate buffered saline (PBS) with topical application of PBS in the round window. In study group A (n = 7), the effect of topical phosphate buffered saline with IV infusion of propofol on CBF and hearing was evaluated. In study group B (n = 7), additional effects of topical epinephrine with IV infusion of propofol on CBF and hearing were evaluated. The laser Doppler blood flowmeter, CBF, and the mean arterial blood pressure (MAP) were measured and analyzed. Additionally, hearing test using auditory brainstem response (ABR) was performed in both groups.

RESULTS

In both groups, infusion of propofol induced a time-dependent decrease in MAP. Approximately 30 min after the start of the propofol infusion, the CBF started to decrease slowly. The decrease in CBF was significantly greater in the study group compared to the control group. The threshold was elevated in the study group relative to the control group.

CONCLUSION

During middle ear surgery, use of IV infusion of propofol with topical epinephrine cotton ball or cottonoid application is not recommended.

Intravenous versus inhalational techniques for rapid emergence from anaesthesia in patients undergoing brain tumour surgery

BACKGROUND

Brain tumour surgery usually is carried out with the patient under general anaesthesia. Over past years, both intravenous and inhalational anaesthetic agents have been used, but the superiority of one agent over the other is a topic of ongoing debate. Early and rapid emergence from anaesthesia is desirable for most neurosurgical patients. With the availability of newer intravenous and inhalational anaesthetic agents, all of which have inherent advantages and disadvantages, we remain uncertain as to which technique may result in more rapid early recovery from anaesthesia.

OBJECTIVES

To assess the effects of intravenous versus inhalational techniques for rapid emergence from anaesthesia in patients undergoing brain tumour surgery.

SEARCH METHODS

We searched the Cochrane Central Register of Controlled Trials (CENTRAL; 2014, Issue 6) in The Cochrane Library, MEDLINE via Ovid SP (1966 to June 2014) and Embase via Ovid SP (1980 to June 2014). We also searched specific websites, such as www.indmed.nic.in, www.cochrane-sadcct.org and www.Clinicaltrials.gov (October 2014). We reran the searches for all databases in March 2016, and when we update the review, we will deal with the two studies of interest found through this search that are awaiting classification.

SELECTION CRITERIA

We included randomized controlled trials (RCTs) that compared the use of intravenous anaesthetic agents such as propofol and thiopentone with inhalational anaesthetic agents such as isoflurane and sevoflurane for maintenance of general anaesthesia during brain tumour surgery. Primary outcomes were emergence from anaesthesia (assessed by time to follow verbal commands, in minutes) and adverse events during emergence, such as haemodynamic changes, agitation, desaturation, muscle weakness, nausea and vomiting, shivering and pain. Secondary outcomes were time to eye opening, recovery from anaesthesia using the Aldrete or Modified Aldrete score (i.e. time to attain score ≥ 9, in minutes), opioid consumption, brain relaxation (as assessed by the surgeon on a 4- or 5-point scale) and complications of anaesthetic techniques, such as intraoperative haemodynamic instability in terms of hypotension or hypertension (mmHg), increased or decreased heart rate (beats/min) and brain swelling.

DATA COLLECTION AND ANALYSIS

We used standardized methods in conducting the systematic review, as described by the Cochrane Handbook for Systematic Reviews of Interventions. Two review authors independently extracted details of trial methods and outcome data from reports of all trials considered eligible for inclusion. We performed all analyses on an intention-to-treat basis. We used a fixed-effect model when we found no evidence of significant heterogeneity between studies, and a random-effects model when heterogeneity was likely. For assessments of the overall quality of evidence for each outcome that included pooled data from RCTs only, we downgraded the evidence from 'high quality' by one level for serious (or by two levels for very serious) study limitations (risk of bias), indirectness of evidence, serious inconsistency, imprecision of effect or potential publication bias.

MAIN RESULTS

We included 15 RCTs with 1833 participants. We determined that none of the RCTs were of high methodological quality. For our primary outcomes, pooled results from two trials suggest that time to emergence from anaesthesia, that is, time needed to follow verbal commands, was longer with isoflurane than with propofol (mean difference (MD) -3.29 minutes, 95% confidence interval (CI) -5.41 to -1.18, low-quality evidence), and time to emergence from anaesthesia was not different with sevoflurane compared with propofol (MD 0.28 minutes slower with sevoflurane, 95% CI -0.56 to 1.12, four studies, low-quality evidence). Pooled analyses for adverse events suggest lower risk of nausea and vomiting with propofol than with sevoflurane (risk ratio (RR) 0.68, 95% CI 0.51 to 0.91, low-quality evidence) or isoflurane (RR 0.45, 95% CI 0.26 to 0.78) and greater risk of haemodynamic changes with propofol than with sevoflurane (RR 1.85, 95% CI 1.07 to 3.17), but no differences in the risk of shivering or pain. Pooled analyses for brain relaxation suggest lower risk of tense brain with propofol than with isoflurane (RR 0.88, 95% CI 0.67 to 1.17, low-quality evidence), but no difference when propofol is compared with sevoflurane.

AUTHORS' CONCLUSIONS

The finding of our review is that the intravenous technique is comparable with the inhalational technique of using sevoflurane to provide early emergence from anaesthesia. Adverse events with both techniques are also comparable. However, we derived evidence of low quality from a limited number of studies. Use of isoflurane delays emergence from anaesthesia. These results should be interpreted with caution. Randomized controlled trials based on uniform and standard methods are needed. Researchers should follow proper methods of randomization and blinding, and trials should be adequately powered.

Propofol: Effects on the Central Nervous System

Propofol remains a popular agent for providing intraoperative anesthesia as well as sedation during mechanical ventilation in the intensive care unit (ICU) setting. In addition to its sedative/anxiolytic properties, propofol has been shown to have several beneficial effects on central nervous system (CNS) parameters such as cerebral metabolic rate for oxygen, cerebral blood flow, and intracranial pressure. These properties have been demonstrated in both laboratory animals and in clinical investigations In humans. This article reviews the available literature concerning the effects of propofol on CNS dynamics and discusses its possible application as a therapeutic agent in patients with altered intracranial compliance and/or increased intracranial pressure.

Low-Dimensional Models of "Neuro-Glio-Vascular Unit" for Describing Neural Dynamics under Normal and Energy-Starved Conditions

The motivation of developing simple minimal models for neuro-glio-vascular (NGV) system arises from a recent modeling study elucidating the bidirectional information flow within the NGV system having 89 dynamic equations (1). While this was one of the first attempts at formulating a comprehensive model for neuro-glio-vascular system, it poses severe restrictions in scaling up to network levels. On the contrary, low-­dimensional models are convenient devices in simulating large networks that also provide an intuitive understanding of the complex interactions occurring within the NGV system. The key idea underlying the proposed models is to describe the glio-vascular system as a lumped system, which takes neural firing rate as input and returns an “energy” variable (analogous to ATP) as output. To this end, we present two models: biophysical neuro-energy (Model 1 with five variables), comprising K_ATP channel activity governed by neuronal ATP dynamics, and the dynamic threshold (Model 2 with three variables), depicting the dependence of neural firing threshold on the ATP dynamics. Both the models show different firing regimes, such as continuous spiking, phasic, and tonic bursting depending on the ATP production coefficient, ɛ_p, and external current. We then demonstrate that in a network comprising such energy-dependent neuron units, ɛ_p could modulate the local field potential (LFP) frequency and amplitude. Interestingly, low-frequency LFP dominates under low ɛ_p conditions, which is thought to be reminiscent of seizure-like activity observed in epilepsy. The proposed “neuron-energy” unit may be implemented in building models of NGV networks to simulate data obtained from multimodal neuroimaging systems, such as functional near infrared spectroscopy coupled to electroencephalogram and functional magnetic resonance imaging coupled to electroencephalogram. Such models could also provide a theoretical basis for devising optimal neurorehabilitation strategies, such as non-invasive brain stimulation for stroke patients.

Bedside Optic Nerve Sheath Diameter Assessment in the Identification of Increased Intracranial Pressure in Suspected Idiopathic Intracranial Hypertension

OBJECTIVE

We determined whether the bedside assessment of the optic nerve sheath diameter could identify elevated intracranial pressure in individuals with suspected idiopathic intracranial hypertension.

METHODS

This was a single-center, prospective, rater-blinded study performed in a freestanding pediatric teaching hospital. Patients aged 12 to 18 years scheduled for an elective lumbar puncture with the suspicion of idiopathic intracranial hypertension were eligible to participate. Optic nerve sheath diameter was measured via ultrasonography before performing a sedated lumbar puncture for measuring cerebrospinal fluid opening pressure. Abnormal measurements were predefined as optic nerve sheath diameter ≥4.5 mm and a cerebrospinal fluid opening pressure greater than 20 cmH2O.

RESULTS

Thirteen patients participated in the study, 10 of whom had elevated intracranial pressure. Optic nerve sheath diameter was able to predict or rule out elevated intracranial pressure in all patients.

CONCLUSIONS

Noninvasive assessment of the optic nerve sheath diameter could help to identify patients with elevated intracranial pressure when idiopathic intracranial hypertension is suspected.

Management of pediatric traumatic brain injury

OPINION STATEMENT

Pediatric severe traumatic brain injury continues to be a major cause of disability and death. Rapid initial airway and hemodynamic stabilization is critical, followed by the need for immediate recognition of intracranial pathology that requires neurosurgical intervention. Intracranial hypertension and cerebral hypoperfusion have been recognized as major insults after trauma and management should be directed at preventing both. Sedation with opioids, moderate hyperventilation to arterial carbon dioxide level of 35-40 mmHg, hyperosmolar therapy with 3 % saline or mannitol, normothermia, and cerebrospinal fluid drainage continue to be the cornerstones of initial management of intracranial hypertension (intracranial pressure >20 mmHg). Refractory intracranial hypertension is treated with high-dose barbiturate therapy to achieve medical burst suppression on electroencephalography and decompressive craniectomy. In addition, those children require antiepileptic medications for seizure prophylaxis, adequate nutritional management, and early physical therapy and rehabilitation referrals. Most of the evidence for care of children with brain injury comes from center-specific practice and experience rather than objective data. This lack of evidence provides the ground for ongoing research; nevertheless, outcomes after traumatic brain injury continue to show improvement.

Pediatric head injury: a pain for the emergency physician?

The prompt diagnosis and initial management of pediatric traumatic brain injury poses many challenges to the emergency department (ED) physician. In this review, we aim to appraise the literature on specific management issues faced in the ED, specifically: indications for neuroimaging, choice of sedatives, applicability of hyperventilation, utility of hyperosmolar agents, prophylactic anti-epileptics, and effect of hypothermia in traumatic brain injury. A comprehensive literature search of PubMed and Embase was performed in each specific area of focus corresponding to the relevant questions. The majority of the head injured patients presenting to the ED are mild and can be observed. Clinical prediction rules assist the ED physician in deciding if neuroimaging is warranted. In cases of major head injury, prompt airway control and careful use of sedation are necessary to minimize the chance of hypoxia, while avoiding hyperventilation. Hyperosmolar agents should be started in these cases and normothermia maintained. The majority of the evidence is derived from adult studies, and most treatment modalities are still controversial. Recent multicenter trials have highlighted the need to establish common platforms for further collaboration.

Effects of a novel method of anesthesia combining propofol and volatile anesthesia on the incidence of postoperative nausea and vomiting in patients undergoing laparoscopic gynecological surgery

BACKGROUND

We investigated the effects of a novel method of anesthesia combining propofol and volatile anesthesia on the incidence of postoperative nausea and vomiting in patients undergoing laparoscopic gynecological surgery.

METHODS

Patients were randomly divided into three groups: those maintained with sevoflurane (Group S, n=42), propofol (Group P, n=42), or combined propofol and sevoflurane (Group PS, n=42). We assessed complete response (no postoperative nausea and vomiting and no rescue antiemetic use), incidence of nausea and vomiting, nausea severity score, vomiting frequency, rescue antiemetic use, and postoperative pain at 2 and 24h after surgery.

RESULTS

The number of patients who exhibited a complete response was greater in Groups P and PS than in Group S at 0-2h (74%, 76% and 43%, respectively, p=0.001) and 0-24h (71%, 76% and 38%, respectively, p<0.0005). The incidence of nausea at 0-2h (Group S=57%, Group P=26% and Group PS=21%, p=0.001) and 0-24h (Group S=62%, Group P=29% and Group PS=21%, p<0.0005) was also significantly different among groups. However, there were no significant differences among groups in the incidence or frequency of vomiting or rescue antiemetic use at 0-24h.

CONCLUSION

Combined propofol and volatile anesthesia during laparoscopic gynecological surgery effectively decreases the incidence of postoperative nausea. We term this novel method of anesthesia "combined intravenous-volatile anesthesia (CIVA)".

Intracranial pressure response after pharmacologic treatment of intracranial hypertension

BACKGROUND

The accepted treatment of increased intracranial pressure (ICP) in patients experiencing severe traumatic brain injury is multimodal and algorithmic, obscuring individual effects of treatment. Using continuous vital signs monitoring, we sought to measure treatment effect and ascertain the accuracy of manual data recording.

METHODS

Patients older than 17 years, admitted and requiring ICP monitoring between 2008 and 2010 at a high-volume urban trauma center, were retrospectively evaluated. Timing and dose of ICP-directed therapy were recorded from paper and electronic medical records. ICP data were collected automatically at 6-second intervals and from manual charts. A statistical mixed model was applied to all data to account for multiple sampling.

RESULTS

A total of 117 patients met inclusion criteria; 450 treatments were administered when nursing records indicate an ICP greater than 20 mm Hg, while 968 treatments were given when ICP was greater than 20 mm Hg by automated data. Pharmacologic treatments identified include hypertonic saline (HTS), mannitol, barbiturates, and dose escalations of propofol or fentanyl infusions. Treatment with HTS resulted in the largest ICP decrease of the treatments examined, with a 1-hour ICP reduction of 8.8/9.9 mm Hg (for a small/large dose) according to manual data and a reduction of 3.0/2.4 mm Hg according to automated data. Propofol and fentanyl escalations resulted in smaller but significant ICP reductions. Mannitol (n = 8) resulted in statistically insignificant trends down in the first hour but rebounded by the second hour after administration. The average ICP in the hour before medication administration was higher for barbiturates (27 mm Hg) and mannitol (32 mm Hg) than for the other interventions (18-19 mm Hg).

CONCLUSION

ICP fell after administration of HTS, mannitol, or barbiturates and showed continued improvement after 2 hours. ICP fell initially after treatment with short-acting propofol and fentanyl but trended back up after 2 hours. Manually recorded data consistently overestimated treatment effectiveness. Automated data collection gives a more accurate assessment of patient status and responsiveness to treatment.

LEVEL OF EVIDENCE

Therapeutic study, level IV.

Sedation in traumatic brain injury

Several different classes of sedative agents are used in the management of patients with traumatic brain injury (TBI). These agents are used at induction of anaesthesia, to maintain sedation, to reduce elevated intracranial pressure, to terminate seizure activity and facilitate ventilation. The intent of their use is to prevent secondary brain injury by facilitating and optimising ventilation, reducing cerebral metabolic rate and reducing intracranial pressure. There is limited evidence available as to the best choice of sedative agents in TBI, with each agent having specific advantages and disadvantages. This review discusses these agents and offers evidence-based guidance as to the appropriate context in which each agent may be used. Propofol, benzodiazepines, narcotics, barbiturates, etomidate, ketamine, and dexmedetomidine are reviewed and compared.

The efficacy of superficial temporal artery–middle cerebral artery anastomosis in patients with moyamoya disease complaining of severe headache

Object

Some patients with moyamoya disease complain of severe headache, which may be closely related to cerebral ischemia. The efficacy of superficial temporal artery–middle cerebral artery (STA-MCA) anastomosis in these patients was evaluated by clinicoradiological studies.

Methods

Of 117 consecutive patients with ischemic moyamoya disease, 25 complained mainly of severe headache (headache group) and 92 had no significant headache (nonheadache group). Intensity of headache was evaluated pre- and postoperatively. Furthermore, regional cerebral blood flow (rCBF) and cerebrovascular reactivity (CVR) were assessed pre- and postoperatively.

Results

The headache group was significantly younger than the nonheadache group. In a group corrected for the age distribution, preoperative rCBF and CVR were similar in headache and nonheadache groups. After STA-MCA anastomosis, 16 patients with headache experienced complete relief from headache, 7 patients showed remarkable improvements and discontinued medications for headache, and the remaining 2 patients had some alleviation of headache but sometimes required medication. In the headache group, the postoperative rCBF was significantly greater than the preoperative value. The postoperative rCBF in this group was also significantly greater than the postoperative rCBF in the nonheadache group.

Conclusions

These data suggest that severe headache is one of the main symptoms in young patients with moyamoya disease probably related to cerebral circulatory disturbances. An STA-MCA anastomosis is effective in relieving headache in patients with ischemic moyamoya disease manifesting severe headache, probably by improving perfusion pressure and cerebral circulation.

Incidence and Predictive Factors of Cerebral Hyperperfusion After Extracranial-Intracranial Bypass for Occlusive Cerebrovascular Diseases

BACKGROUND:

Although many studies of postoperative cerebral hyperperfusion syndrome (CHS) after carotid endarterectomy have been reported, there are few reports related to extracranial-intracranial (EC-IC) bypass for atherosclerotic occlusive cerebrovascular diseases.

OBJECTIVE:

To examine the incidence of cerebral hyperperfusion and CHS after EC-IC bypass and to investigate predictive factors.

METHODS:

Fifty consecutive patients undergoing EC-IC bypass for atherosclerotic occlusive cerebrovascular diseases were studied. Immediately after bypass surgery, resting regional cerebral blood flow was determined under continuous sedation, and postoperative hyperperfusion was evaluated according to the definitions as follows: &gt; 50% increase in regional cerebral blood flow compared with the contralateral side (method 1) and &gt; 100% increase in corrected regional cerebral blood flow compared with preoperative values (method 2). Logistic regression analysis was conducted to determine the effect of multiple variables on postoperative hyperperfusion.

RESULTS:

Transient symptoms of CHS were observed in 3 patients. Cerebral hyperperfusion was detected in 12 patients (24%) as defined by method 1 and in 9 patients (18%) by method 2. Postoperative hyperperfusion occurred significantly more frequently in patients with the steal phenomenon (regional cerebral vasoreactivity ≤ 0%; P = .001 by method 1 and P = .001 by method 2) and correlated with impaired preoperative regional cerebral vasoreactivity (P &lt; .001). Logistic regression analysis revealed that the steal phenomenon was a significant risk factor for hyperperfusion as defined by both methods 1 (P = .009) and 2 (P = .03).

CONCLUSION:

The incidence of cerebral blood flow-assessed postoperative hyperperfusion after EC-IC bypass for atherosclerotic occlusive cerebrovascular diseases was not rare. Post EC-IC bypass CHS could be reduced by continuous, strict blood pressure control under sedation.

POSTCAROTID ENDARTERECTOMY CEREBRAL HYPERPERFUSION CAN BE PREVENTED BY MINIMIZING INTRAOPERATIVE CEREBRAL ISCHEMIA AND STRICT POSTOPERATIVE BLOOD PRESSURE CONTROL UNDER CONTINUOUS SEDATION

OBJECTIVE

Cerebral hyperperfusion syndrome is a major complication after carotid endarterectomy (CEA). We investigated whether our strategy of minimizing intraoperative cerebral ischemia and strict postoperative blood pressure control under continuous sedation prevented postoperative hyperperfusion.

METHODS

Eighty consecutive patients undergoing CEA were studied. A shunt was used in all patients during CEA. All patients were managed postoperatively under continuous sedation for as long as 48 hours on the basis of the regional cerebral blood flow (rCBF) measured immediately after CEA. Postoperative hyperperfusion was assessed, on the basis of the cerebral blood flow study under sedation (propofol) after CEA, either as a greater than 30% increase in rCBF compared with the contralateral side, or a greater than 100% increase in the corrected rCBF (calculated from percentage reduction of the contralateral rCBF induced by propofol) compared with preoperative values.

RESULTS

No patient developed cerebral hyperperfusion syndrome. Postoperative hyperperfusion was found at very low rates (2.5% in the middle cerebral artery territory and 1.3% in the anterior cerebral artery territory by definition 1, and 0% in both territories by definition 2). Ratios of regional oxygen saturation after internal carotid artery clamping to preclamp baseline values were greater than 0.9 in 78 of 80 patients, indicating very mild intraoperative cerebral ischemia. Parameters related to cerebral ischemia during CEA, such as regional oxygen saturation, internal carotid artery cross-clamping duration, and stump pressure (index), did not affect the incidence of postoperative hyperperfusion.

CONCLUSION

The present study suggests that minimizing intraoperative cerebral ischemia using a shunt, followed by strict postoperative blood pressure control under continuous sedation, can prevent post-CEA hyperperfusion.

Treatment of intracranial hypertension

PURPOSE OF REVIEW

The review provides key points and recent advances regarding the treatments of intracranial hypertension as a consequence of traumatic brain injury. The review is based on the pathophysiology of brain edema and draws on the current literature as well as clinical bedside experience.

RECENT FINDINGS

The review will cite baseline literature and discuss emerging data on cerebral perfusion pressure, sedation, hypothermia, osmotherapy and albumin as treatments of intracranial hypertension in traumatic brain-injured patients.

SUMMARY

One of the key issues is to consider that traumatic brain injury is more likely a syndrome than a disease. In particular, the presence or absence of a high contusional volume could influence the treatments to be implemented. The use of osmotherapy and/or high cerebral perfusion pressure should be restricted to patients without major contusions. Some physiopathological, experimental and clinical data, however, show that corticosteroids and albumin--therapies that have been proven deleterious if administered systematically--are worth reconsidering for this subgroup of patients. The current Pitié-Salpêtrière algorithm, where treatments are stratified according to their potential side effects, will be added at the end of the review as an example of an integrated strategy.

Infusion rate of propofol and jugular venous oxygen saturation

We compared jugular venous blood oxygen saturation (Sj(O) (2)) and the arterial-to-jugular-bulb venous oxygen content difference (AjD(O) (2)) between bispectral index (BIS) values of 40 and 60, adjusted by the infusion rate of propofol. Eighteen postoperative neurosurgical patients (Glasgow Coma Scale [GCS] scores, 11-15) were enrolled. Normocapnia, normothermia, and a mean arterial blood pressure greater than 70 mmHg were maintained. At BIS values of 40 and 60, hemoglobin, oxygen saturation, and the oxygen partial pressure of arterial and jugular venous blood were measured. Sj(O) (2) at BIS40 (58 +/- 9%) was significantly (P < 0.01) lower than that at BIS60 (63 +/- 10%), and AjD(O) (2) at BIS40 (6.3 +/- 1.5 ml.dl(-1)) was significantly (P < 0.01) higher than that at BIS60 (5.7 +/- 1.5 ml.dl(-1); mean +/- SD). At BIS40, status defined as Sj(O) (2) less than 50% was observed in 3 patients, while this status was observed in 1 patient at BIS60. In conclusion, in patients with postoperative neurosurgical surgery (GCS scores, 11-15), decreases of propofol infusion to adjust the BIS value from 40 to 60 increase the cerebral oxygen balance.

Evaluation of an anaesthetic technique used in dogs undergoing craniectomy for tumour resection

OBJECTIVE

To evaluate a total intravenous anaesthetic technique in dogs undergoing craniectomy.

STUDY DESIGN

Prospective clinical study.

ANIMALS

Ten dogs admitted for elective surgical resection of rostro-tentorial tumours.

METHODS

All dogs were premedicated with methadone, 0.2 mg kg(-1) intramuscularly 30 minutes prior to induction of anaesthesia. Anaesthesia was induced with propofol administered intravenously (IV) to effect, following administration of lidocaine 1 mg kg(-1) IV and maintained with a continuous infusion of propofol at < or =0.4 mg kg(-1) minute(-1) during instrumentation and preparation and during movement of the animals to recovery. During surgery, anaesthesia was maintained using a continuous infusion of propofol at <or =0.4 mg kg(-1) minute(-1) and alfentanil < or =1 microg kg(-1) minute(-1). Lidocaine was administered at 1 mg kg(-1) IV immediately prior to extubation. Arterial blood pressure and heart rate (HR) were recorded prior to induction and every 5 minutes throughout preparation and surgery. Central venous pressure was recorded every 5 minutes throughout surgery.

RESULTS

Administration of propofol and lidocaine prevented significant increases in mean arterial blood pressure (MAP) and HR during endotracheal intubation and extubation. Adequate MAP was maintained throughout anaesthesia. Recovery was smooth and excitement free. There was no association between duration of anaesthesia, total drugs administered, or severity of neurological disease and recovery times. Postoperatively there was no deterioration in neurological function in the immediate postoperative period with complete resolution of pre-existing neurological deficits within 7 days of surgery.

CONCLUSION

This technique provided minimal response to intubation and extubation, adequate arterial blood pressure and a smooth predictable recovery. All animals were neurologically improved by the time of discharge, suggesting that this technique had not caused significant neuronal damage.

CLINICAL RELEVANCE

Total intravenous anaesthesia with propofol and alfentanil appears to be a satisfactory anaesthetic technique for use in dogs undergoing surgery for debulking/removal of rostro-tentorial tumours.

[Management of severe traumatic brain injury]

Severe brain injuries, most often occurring in young subjects, are a major source of lost work years. These injuries are medical and surgical emergencies. Prehospital management of severe brain injuries requires intubation and mechanical ventilation aimed at normal arterial carbon dioxide pressure. Signs of transtentorial herniation: Uni- or bilateral mydriasis requires immediate perfusion of 20% mannitol or hypertonic sodium chloride. Neurological disorders after head injury justify emergency cerebral computed tomography. The presence of a mass syndrome or signs of transtentorial herniation are in principle indications for surgery. Specialized hospital management is essential. In the case of refractory intracranial hypertension, the cerebral perfusion pressure and osmotherapy should be adapted to the volume of the cerebral contusion. The use of deep hypothermia and barbiturates should be minimized as much as possible. Magnetic resonance imaging makes it possible to identify the cerebral lesions.

Combined effects of propofol and mild hypothermia on cerebral metabolism and blood flow in rhesus monkey: a positron emission tomography study

PURPOSE

Propofol reduces the cerebral metabolic rate for oxygen (CMRO2), regional CMRO2 (rCMRO2), cerebral blood flow (CBF), and regional CBF (rCBF), but maintains the coupling of cerebral metabolism and blood flow. Under mild to moderate hypothermia, the coupling is maintained, while rCBF is reduced, but no direct measurement of rCMRO2 has yet been reported. This study aimed to evaluate the effects of propofol under normothermic and mild hypothermic temperatures upon rCMRO2, rCBF, and their regional coupling, through direct measurement by positron emission tomography.

METHODS

Rhesus monkeys were anesthetized with 65% nitrous oxide and propofol. Then rCBF and rCMRO2 were measured under four sets of conditions: infusion of a low-propofol dose (12 mg.kg(-1) x h(-1)) at normothermic temperatures (38 degrees C), a high dose (25 mg x kg(-1) x h(-1)) at normothermic temperatures, a low dose under mild hypothermia (35 degrees C), and a high dose under mild hypothermia. The ratio of rCBF/rCMRO(2) was calculated from these data.

RESULTS

Reductions in CMRO2 and rCMRO2 in most regions were associated with two factors: the higher propofol dose and the induction of hypothermia, but there was no interaction between these factors. Concerning blood flow, no significant reduction was observed, except for CBF by the induction of hypothermia. The ratio of rCBF/rCMRO2 was constant in this study setting.

CONCLUSION

During propofol anesthesia, it is possible to reduce cerebral metabolism throughout the entire brain as well as in any brain region by increasing the propofol dose or inducing hypothermia. The concurrent use of these two interventions has an additive effect on metabolism, and can be considered as safe, as their combination does not impair the coupling of cerebral metabolism and blood flow.

Propofol is associated with impaired brain metabolism during hypothermic circulatory arrest: an experimental microdialysis study

BACKGROUND

Propofol is a widely used anesthetic in cardiac surgery. It has been shown to increase cerebrovascular resistance resulting in decreased cerebral blood flow. Efficient brain perfusion and tissue oxygenation during cardiopulmonary bypass (CPB) is essential in surgery requiring hypothermic circulatory arrest (HCA). The effects of propofol on brain metabolism are reported in a surviving porcine model of HCA.

METHODS

Twenty female juvenile pigs undergoing 75 minutes of HCA at a brain temperature of 18 degrees C were assigned to either propofol- or isoflurane anesthesia combined with alpha-stat perfusion strategy during CPB cooling and rewarming. Brain microdialysis analysis was used for determination of brain metabolism, and tissue oxygen partial pressure and intracranial pressures were also followed-up until 8 hours postoperatively.

RESULTS

Brain concentrations of glutamate and glycerol were significantly higher in the propofol group throughout the experiment (P < .01 and P < .01, respectively). The lactate/pyruvate ratio was significantly higher in the propofol group at 6-, 7-, and 8-hour intervals (P < .05, P < .01, and P < .05, respectively). The intracranial pressure was significantly higher at the 8-hour postoperative interval (P < .05) in the propofol group. A trend toward higher brain oxygen concentrations was observed in the isoflurane group.

CONCLUSIONS

Anesthesia with propofol as compared with isoflurane is associated with impaired brain metabolism during experimental HCA.

The Effect of Electroencephalogram-Targeted High- and Low-Dose Propofol Infusion on Histopathological Damage After Traumatic Brain Injury in the Rat

BACKGROUND

Propofol is commonly used to sedate patients after traumatic brain injury. However, the dose-dependent neuroprotective effects of propofol after head trauma are unknown. We compared histopathological damage after 6 h of electroencephalogram-targeted high- and low-dose propofol infusion in rats subjected to controlled cortical impact (CCI).

METHODS

Animals were randomly assigned to CCI/propofol with electroencephalogram burst-suppression-ratio 1%-5% (CCI/lowprop), CCI/propofol with burst-suppression-ratio 30%-40% (CCI/highprop), control group CCI/1.0 vol % halothane (CCI/halo), or sham group with halothane anesthesia (SHAM/halo). Brain slices were stained with kresyl violet (KV) and hematoxylin/eosin (HE) to evaluate lesion volume, number of eosinophilic cells, and activation of caspase-3 in the hippocampus.

RESULTS

Lesion volume (mm3) and number of eosinophilic cells in the hippocampus did not differ significantly [lesion volumes: CCI/lowprop 31.55 +/- 14.66 (KV) and 53.77 +/- 8.62 (HE); CCI/highprop 33.81 +/- 10.57 (KV) and 52.30 +/- 11.55 (HE); CCI/halo 36.42 +/- 17.06 (KV) and 57.95 +/- 8.49 (HE)]. Activation of caspase-3 occurred in the ipsilateral hippocampus in all CCI-groups.

CONCLUSION

Despite different levels of cortical neuronal function, there were no relevant differences in the short-term histopathological damage. These results challenge the view that the neuroprotective effect of propofol relates to the suppression of cerebral metabolic demand.

Propofol for sedation in neuro-intensive care

Interventions in the intensive care unit often require that the patient be sedated. Propofol is a widely used, potent sedative agent that is popular in critical care and operating room settings. In addition to its sedative qualities, propofol has neurovascular, neuroprotective, and electroencephalographical effects that are salutory in the patient in neurocritical care. However, the 15-year experience with this agent has not been entirely unbesmirched by controversy: propofol also has important adverse effects that must be carefully considered. This article discusses and reviews the pharmacology of propofol, with specific emphasis on its use as a sedative in the neuro-intensive care unit. A detailed explanation of central nervous system and cardiovascular mechanisms is presented. Additionally, the article reviews the literature specifically pertaining to neurocritical care use of propofol.

The Effects of Propofol or Sevoflurane on the Estimated Cerebral Perfusion Pressure and Zero Flow Pressure

The zero flow pressure (ZFP) is the pressure at which blood flow ceases through a vascular bed. Using transcranial Doppler ultrasonography, we investigated the effects of propofol or sevoflurane on the estimated cerebral perfusion pressure (eCPP) and ZFP in the cerebral circulation. Twenty-three healthy patients undergoing nonneurosurgical procedures under general anesthesia were studied. After induction of anesthesia using propofol, the anesthesia was maintained with either propofol infusion (n = 13) or sevoflurane (n = 10). Middle cerebral artery flow velocity, noninvasive arterial blood pressure, and end-tidal carbon dioxide partial pressure were recorded awake as a baseline, and during steady-state anesthesia at normocapnia (baseline end-tidal carbon dioxide partial pressure) and hypocapnia (1 kPa below baseline). The eCPP and ZFP were calculated using an established formula. The mean arterial blood pressure decreased in both groups. The eCPP decreased significantly in the propofol group (median, from 58 to 41 mm Hg) but not in the sevoflurane group (from 60 to 62 mm Hg). Correspondingly, ZFP increased significantly in the propofol group (from 25 to 33 mm Hg) and it decreased significantly in the sevoflurane group (from 27 to 7 mm Hg). Hypocapnia did not change eCPP or ZFP in the propofol group, but it significantly decreased eCPP and increased ZFP in the sevoflurane group.

Quand et comment débuter une sédation en neuroréanimation ?

Sedatives drugs are part of the everyday care in the neuro-ICU. Reasons to sedate patients in neuro-ICU are as usual to ensure the comfort and to secure the patients, to permit nursing as well as to permit adaptation to the ventilator. But some objectives are specific in neuro-ICU as optimisation of cerebral haemodynamics and oxygenation, and to avoid a convulsive state or a dysautonomic syndrome. Starting the sedation usually necessitate a tracheal intubation and mechanical ventilation. Patients presenting with intracranial hypertension are at risk of developing cerebral ischaemia in case of cerebral haemodynamics alteration associated with anaesthetic drugs injection. Morphinomimetics increase intracranial pressure (ICP), but cerebral perfusion pressure and oxygenation (CPP) remain usually unaltered. Injection of an intravenous bolus of thiopental or propofol lowers ICP and CPP, but also the cerebral tissular oxygen consumption: the cerebral oxygenation seems therefore protected. The succinylcholine used for emergency tracheal intubation has no effect on the cerebral haemodynamic. Some more studies are needed to better understand the cerebral oxygenation at the local level when sedative drugs are injected or perfused in patients with intracranial hypertension.

Comparative tolerability of sedative agents in head-injured adults

Sedative agents are widely used in the management of patients with head injury. These drugs can facilitate assisted ventilation and may provide useful reductions in cerebral oxygen demand. However, they may compromise cerebral oxygen delivery via their cardiovascular effects. In addition, individual sedative agents have specific and sometimes serious adverse effects. This review focuses on the different classes of sedative agents used in head injury, with a discussion of their role in the context of clinical pathophysiology. While there is no sedative that has all the desirable characteristics for an agent in this clinical setting, careful titration of dose, combination of agents, and a clear understanding of the pathophysiology and pharmacology of these agents will allow safe sedative administration in head injury.

Effect of Propofol and Clonidine on Cerebral Blood Flow Velocity and Carbon Dioxide Reactivity in the Middle Cerebral Artery

This study was designed to evaluate the effects of propofol alone and propofol-clonidine combination on human middle cerebral artery blood flow velocity (Vmca) and cerebrovascular carbon dioxide (CO2) response by using transcranial Doppler ultrasonography. Mean Vmca in response to changes in arterial partial pressure of CO2 (Paco2) was determined under the following conditions: awake (group 1), propofol anesthesia (group 2), and combined propofol-clonidine anesthesia (group 3). Normocapnic, hypercapnic, and hypocapnic values of heart rate, mean arterial pressure, partial end-tidal CO2 pressure, Paco2, and Vmca were obtained. The mean Vmca in groups 2 and 3 was significantly lower than that in group 1 at each level of Paco2. The calculated Vmca at each level of Paco2 was not different between groups 2 and 3. There was a correlation between Paco2 and Vmca in all groups, but in the anesthetized groups the effect of Paco2 on Vmca was attenuated. The present data demonstrated that clonidine-propofol does not change CO2 reactivity compared with propofol alone, but both anesthetics attenuate cerebral blood flow compared with awake controls.

Effects of propofol on cerebral blood flow and the metabolic rate of oxygen in humans

BACKGROUND

Effects of propofol on human cerebral blood flow (CBF), cerebral metabolic rate of oxygen (CMRO2), and blood flow-metabolism coupling have not been fully evaluated. We therefore assessed the effects of propofol on total-CBF and CMRO2 in patients without noxious stimuli and neurologic disorders.

METHODS

General anesthesia was induced with midazolam (0.2 mg/kg) and fentanyl (5 microg/kg) in 10 patients (ASA physical status I) undergoing knee joint endoscopic surgery. Epidural anesthesia was also performed to avoid noxious stimuli during surgery. Cerebral blood flow (CBF) and cerebral arteriovenous oxygen content difference (a-vDO2) was measured using the Kety-Schmidt method with 15% N2O as a tracer before and after propofol infusion (6 mg/kg/h for 40 min), and the CMRO2 was also calculated.

RESULTS

CBF decreased following propofol infusion from 34.4 ml/100 g/min (range 28.4-52.0) to 30.0 ml/100 g/min (range 20.2-42.4) (P=0.04). Although there was no significant change in a-vDO2, CMRO2 decreased following propofol infusion from 2.7 ml/100 g/min (range 2.2-4.3) to 2.2 ml/100 g/min (range 1.4-3.0) (P=0.04). There was a strong linear correlation between CBF and CMRO2 (r=0.90).

CONCLUSION

Propofol proportionally decreased CBF and CMRO2 without affecting a-vDO2 in humans, suggesting that normal cerebral circulation and metabolism are maintained.

[Anesthesia-resuscitation for intracranial expansive processes in children]

The most frequent space-occupying cerebral lesions in children are brain tumors, mostly posterior fossa tumors and haematoma resulting from arteriovenous malformation rupture. They result in intracranial hypertension, directly or by compression of the cerebrospinal fluid pathway resulting in hydrocephalus. Their localization and compressive effects are responsible for specific neurological deficits and general problems. Posterior fossa lesions carry a high risk of obstructive hydrocephalus, cranial nerves palsy and brain stem compression, pituitary and chiasmatic tumors a risk of blindness, pituitary deficiency and diabetes insipidus, and cortical tumors a risk of motor deficit and epilepsy. All these parameters must be analyzed before choosing anaesthetic protocols, and surgical techniques. In the presence of life-threatening intracranial hypertension, emergency anaesthetic induction, tracheal intubation and ventilation are life-saving. The specific treatment consists in either hydrocephalus derivation, initial medical treatment with osmotherapy, or rarely surgical removal. In other situations, surgical process requires a highly deep, stable anaesthesia with perfect control of cerebral haemodynamics. Surgical positioning is complex for these long lasting procedures and carries specific risks. The most common is venous air embolism in the sitting position that must be prevented by the use of specific measures. In the postoperative period, the risk of neurological and general complications commands close surveillance, fast track extubation must be adapted on an individual basis.