Surgical and not analgesic technique affects postoperative inflammation following colorectal cancer surgery: a prospective, randomized study.

AIM: Epidural analgesia reduces the surgical stress response. However, its effect on pro- and anti-inflammatory cytokines in the genesis of inflammation following major abdominal surgery remains unclear. Our main objective was to elucidate whether perioperative epidural analgesia prevents the inflammatory response following colorectal cancer surgery. METHODS: Ninety-six patients scheduled for open or laparoscopic surgery were randomized to epidural analgesia (group E) or patient-controlled intravenous analgesia (group P). Surgery and anaesthesia were standardized in both groups. Plasma cortisol, insulin and serum cytokines [interleukin 1ß (IL-1ß), IL-4, IL-5, IL-6, IL-8, IL-10, IL-12p70, IL-13, tumour necrosis factor α, interferon γ, granulocyte-macrophage colony-stimulating factor, prostaglandin E2 and vascular endothelial growth factor] were measured preoperatively (T0), 1-6 h postoperatively (T1) and 3-5 days postoperatively (T2). Mixed model analysis was used, after logarithmic transformation when appropriate, for analyses of cytokines and stress markers. RESULTS: >There were no significant differences in any serum cytokine concentration between groups P and E at any time point except for IL-10 which was 87% higher in group P [median and range 4.1 (2.3-9.2) pg/ml] compared to group E [2.6 (1.3-4.7) pg/ml] (P = 0.002) at T1. There was no difference in plasma cortisol and insulin between the groups at any time point after surgery. A significant difference in median serum cytokine concentration was found between open and laparoscopic surgery with higher levels of IL-6, IL-8 and IL-10 at T1 in patients undergoing open surgery compared to laparoscopic surgery. No difference in serum cytokine concentration was detected between the groups or between the surgical technique at T2. CONCLUSIONS: Open surgery, compared to laparoscopic surgery, has greater impact on these inflammatory mediators than epidural analgesia vs intravenous analgesia.

Reduction in mortality after epidural anaesthesia and analgesia in patients undergoing rectal but not colonic cancer surgery: a retrospective analysis of data from 655 patients in central Sweden.

BACKGROUND: There is some evidence that epidural analgesia (EDA) reduces tumour recurrence after breast and prostatic cancer surgery. We assessed whether EDA reduces long-term mortality after colorectal cancer surgery. METHODS: All patients having colorectal cancer surgery between January 2004 and January 2008 at Linköping and Örebro were included. Exclusion criteria were: emergency operations, laparoscopic-assisted colorectal resection, and stage 4 cancer. Statistical information was obtained from the Swedish National Register for Deaths. Patients were analysed in two groups: EDA group or patient-controlled analgesia (PCA group) as the primary method of analgesia. RESULTS: A total of 655 patients could be included. All-cause mortality for colorectal cancer (stages 1-3) was 22.7% (colon: 20%, rectal: 26%) after 1-5 yr of surgery. Multivariate regression analysis identified the following statistically significant factors for death after colon cancer (P<0.05): age (>72 yr) and cancer stage 3 (compared with stage 1). A similar model for rectal cancer found that age (>72 yr) and the use of PCA rather than EDA and cancer stages 2 and 3 (compared with stage 1) were associated with a higher risk for death. No significant risk of death was found for colon cancer when comparing EDA with PCA (P=0.23), but a significantly increased risk of death was seen after rectal cancer when PCA was used compared with EDA (P=0.049) [hazards ratio: 0.52 (0.27-1.00)]. CONCLUSIONS: We found a reduction in all-cause mortality after rectal but not colon cancer in patients having EDA compared with PCA technique.

To continue or discontinue aspirin in the perioperative period: a randomized, controlled clinical trial.

BACKGROUND: Major adverse cardiac events (MACEs) are a common cause of death after non-cardiac surgery. Despite evidence for the benefit of aspirin for secondary prevention, it is often discontinued in the perioperative period due to the risk of bleeding. METHODS: We conducted a randomized, double-blind, placebo-controlled trial in order to compare the effect of low-dose aspirin with that of placebo on myocardial damage, cardiovascular, and bleeding complications in high-risk patients undergoing non-cardiac surgery. Aspirin (75 mg) or placebo was given 7 days before surgery and continued until the third postoperative day. Patients were followed up for 30 days after surgery. RESULTS: A total of 220 patients were enrolled, 109 patients received aspirin and 111 received placebo. Four patients (3.7%) in the aspirin group and 10 patients (9.0%) in the placebo group had elevated troponin T levels in the postoperative period (P=0.10). Twelve patients (5.4%) had an MACE during the first 30 postoperative days. Two of these patients (1.8%) were in the aspirin group and 10 patients (9.0%) were in the placebo group (P=0.02). Treatment with aspirin resulted in a 7.2% absolute risk reduction [95% confidence interval (CI), 1.3-13%] for postoperative MACE. The relative risk reduction was 80% (95% CI, 9.2-95%). Numbers needed to treat were 14 (95% CI, 7.6-78). No significant differences in bleeding complications were seen between the two groups. CONCLUSIONS: In high-risk patients undergoing non-cardiac surgery, perioperative aspirin reduced the risk of MACE without increasing bleeding complications. However, the study was not powered to evaluate bleeding complications.

N-terminal fragment of pro-B-type natriuretic peptide is a predictor of cardiac events in high-risk patients undergoing acute hip fracture surgery.

BACKGROUND: The aim of this investigation was to assess the incidence of elevated N-terminal fragment of pro-B-type natriuretic peptide (NT-proBNP) and its relation to outcome defined as perioperative adverse cardiac events and all-cause mortality in high-risk patients undergoing non-elective surgery for hip fracture. METHODS: A cohort of patients with hip fractures were extracted from a prospective observational study of high-risk patients (ASA class III or IV) undergoing emergency surgery. NT-proBNP and troponin I were measured before operation. An NT-proBNP > or = 3984 ng litre(-1) was set as the cut-off level for significance. Perioperative adverse cardiac events and 30 day and 3 month mortality were recorded. RESULTS: Sixty-nine subjects were included. Thirty-four subjects (49%) had an NT-proBNP > or = 3984 ng litre(-1) before surgery. Thirty-four subjects (49%) had a perioperative adverse cardiac event. Of these, 22 subjects (65%) had NT-proBNP above the diagnostic threshold compared with 12 subjects (34%) who had an NT-proBNP below the diagnostic threshold (P=0.01). Preoperative NT-proBNP > or = 3984 ng litre(-1) [odds ratio (OR) 3.0; 95% confidence interval (CI) 1.0-8.9] and congestive heart failure (OR 3.0; 95% CI 1.0-9.0) were independent predictors of perioperative adverse cardiac events. A total of eight subjects (12%) died within 30 days after operation. CONCLUSIONS: There is a high incidence of elevated NT-proBNP in subjects undergoing non-elective hip fracture surgery. Preoperative NT-proBNP is a valuable predictor of cardiac complications in the perioperative period.

Predictors of cardiac events in high-risk patients undergoing emergency surgery.

BACKGROUND: The aim of this study was to determine the incidence of myocardial damage and left ventricular myocardial dysfunction and their influence on outcome in high-risk patients undergoing non-elective surgery. METHODS: In this prospective observational study, 211 patients with American Society of Anesthesiologists classification III or IV undergoing emergent or urgent surgery were included. Troponin I (TnI) was measured pre-operatively, 12 and 48 h post-operatively. Pre-operative N-terminal fragment of B-type natriuretic peptide (NT-proBNP), as a marker for left ventricular systolic dysfunction, was analyzed. The diagnostic thresholds were set to TnI >0.06 microg/l and NT-proBNP >1800 pg/ml, respectively. Post-operative major adverse cardiac events (MACE), 30-day and 3-months mortality were recorded. RESULTS: Elevated TnI levels were detected in 33% of the patients post-operatively. A TnI elevation increased the risk of MACE (35% vs. 3% in patients with normal TnI levels, P<0.001) and 30-day mortality (23% vs. 7%, P=0.003). Increased concentrations of NT-proBNP were seen in 59% of the patients. Elevated NT-proBNP was an independent predictor of myocardial damage post-operatively, odds ratio, 6.2 [95% confidence interval (CI) 2.1-18.0] and resulted in an increased risk of MACE (21% vs. 2.5% in patients with NT-proBNP < or = 1800 pg/ml, P<0.001). CONCLUSION: Myocardial damage is common in a high-risk population undergoing unscheduled surgery. These results suggest a close correlation between myocardial damage in the post-operative period and increased concentration of NT-proBNP before surgery. The combinations of TnI and NT-proBNP are reliable markers for monitoring patients at risk in the peri-operative period as well as useful tools in our risk assessment pre-operatively in emergency surgery.

Propofol causes neurite retraction in neurones.

BACKGROUND: The mechanism by which anaesthetic agents produce general anaesthesia is not yet fully understood. Retraction of neurites is an important function of individual neurones and neural plexuses during normal and pathological conditions, and it has been shown that such a retraction pathway exists in developing and mature neurones. We hypothesized that propofol decreases neuronal activity by causing retraction of neuronal neurites. METHODS: Primary cultures of rat cortical neurones were exposed in concentration- and time-response experiments to 0.02, 0.2, 2, and 20 microM propofol or lipid vehicle. Neurones were pretreated with the GABA(A) receptor (GABA(A)R) antagonist, bicuculline, the myosin II ATPase activity inhibitor, blebbistatin, and the F-actin stabilizing agent, phalloidin, followed by administration of propofol (20 microM). Changes in neurite retraction were evaluated using time-lapse light microscopy. RESULTS: Propofol caused a concentration- and time-dependent reversible retraction of cultured cortical neurone neurites. Bicuculline, blebbistatin, and phalloidin completely inhibited propofol-induced neurite retraction. Images of retracted neurites were characterized by a retraction bulb and a thin trailing membrane remnant. CONCLUSIONS: Cultured cortical rat neurones retract their neurites after exposure to propofol in a concentration- and time-dependent manner. This retraction is GABA(A)R mediated, reversible, and dependent on actin and myosin II. Furthermore, the concentrations and times to full retraction and recovery correspond to those observed during propofol anaesthesia.

Differential effect on vasodilatation and pain after intradermal capsaicin in humans during decay of intravenous regional anesthesia with mepivacaine.

BACKGROUND AND OBJECTIVES: When given intracutaneously, capsaicin can cause burning pain by central propagation in thin afferents, as well as neurogenic vasodilatation, reflecting antidromic conduction in the same fibers. We wanted to test the hypothesis that an intravenous regional block (IVRA) inhibits these two phenomena to a similar degree. METHODS: Sixteen healthy volunteers participated. A bilateral IVRA was performed by simultaneously injecting mepivacaine in one arm and normal saline in the other in a randomized, double-blind manner. Ten minutes after release of the tourniquet, neurogenic inflammation was inflicted in each forearm by intracutaneous capsaicin. Microvascular skin blood flow was measured with a laser Doppler perfusion imager. The area of the flare and the flow therein were measured, taking into account the change in baseline caused by mepivacaine treatment and the postischemic hyperemia. Pain was repeatedly evaluated by visual analog scale. RESULTS: The reactive hyperemia following arterial occlusion was less in the mepivacaine-treated arm 10 minutes after tourniquet release (P=.026). Intracutaneous capsaicin elicited a flare in both arms. The area of the flare was smaller 10 minutes after capsaicin (P=.009) in the mepivacaine-treated arm. There was no difference between the arms concerning the mean blood flow within the flare or in ischemic or capsaicin-induced pain. CONCLUSIONS: Mepivacaine, given as an IVRA, had no effect on the post-IVRA sensory function of thin afferents but differentially decreased the spread of the capsaicin-induced flare.

Propofol alters vesicular transport in rat cortical neuronal cultures.

Neuronal intracellular transport is performed by motor proteins, which deliver vesicles, organelles and proteins along cytoskeletal tracks inside the neuron. We have previously shown that the anesthetic propofol causes dose- and time-dependent, reversible retraction of neuronal neurites. We hypothesize that propofol alters the vesicular transport of cortical neurons due to this neurite retraction. Primary cultures of co-cultivated rat cortical neurons and glial cells were exposed to either 2 µM propofol, control medium or the lipid vehicle, in time-response experiments. Reversibility was tested by washing propofol off the cells. The role of the GABA(A) receptor (GABA(A)R) was assessed with the GABA(A)R antagonist gabazine. Vesicles were tracked using differential interference contrast video microscopy. Propofol caused a retrograde movement in 83.4±5.2% (mean±S.E.M.) of vesicles, which accelerated over the observed time course (0.025±0.012 µm.s⁻¹). In control medium, vesicles moved predominantly anterograde (84.6±11.1%) with lower velocity (0.011±0.004 µm.s⁻¹). Cells exposed to the lipid vehicle showed the same dynamic characteristics as cells in control medium. The propofol-induced effect on vesicle transport was reversible and blocked by the GABA(A)R antagonist gabazine in low concentration. Our results show that propofol causes a reversible, accelerating vesicle movement toward the neuronal cell body that is mediated via synaptic GABA(A)R. We have previously reported that propofol initiates neurite retraction, and we propose that propofol causes vesicle movement by retrograde flow of cytoplasm from the narrowed neurite.

The effect of propofol on actin, ERK-1/2 and GABAA receptor content in neurones.

AIM: Interaction with the gamma-aminobutyric acid receptor (GABA(A)R) complex is recognized as an important component of the mechanism of many anaesthetic agents, including propofol. The aims of this study were to investigate the effect of propofol on GABA(A)R, to determine whether exposure of neurones to propofol influences the localization of GABA(A)R within the cell and to look for cytoskeletal changes that may be connected with activation, such as the mitogen-activated protein kinase (MAPK) pathway. METHODS: Primary cortical cell cultures from rat, with and without pre-incubation with the GABA(A)R antagonist bicuculline, were exposed to propofol. The cells were lysed and separated into membrane and cytosolic fractions. Immunoblot analyses of filamentous actin (F-actin), the GABA(A)beta(2)-subunit receptor and extracellular signal-regulated kinase-1/2 (ERK-1/2) were performed. RESULTS: Propofol triggers an increase in GABA(A)R, actin content and ERK-1/2 phosphorylation in the cytosolic fraction. In the membrane fraction, there is a decrease in GABA(A)beta(2)-subunit content and an increase in both actin content and ERK-1/2 phosphorylation. The GABA(A)R antagonist bicuculline blocks the propofol-induced changes in F-actin, ERK and GABA(A)beta(2)-subunit content, and ERK-1/2 phosphorylation. CONCLUSION: We believe that propofol triggers a dose-dependent internalization of the GABA(A)beta(2)-subunit. The increase in internal GABA(A)beta(2)-subunit content exhibits a close relationship to actin polymerization and to an increase in ERK-1/2 activation. Actin contributes to the internalization sequestering of the GABA(A)beta(2)-subunit.

The difference between sleep and anaesthesia is in the intracellular signal: propofol and GABA use different subtypes of the GABA(A) receptor beta subunit and vary in their interaction with actin.

BACKGROUND: Propofol is known to interact with the gamma-aminobutyric acidA (GABA(A)) receptor, however, activating the receptor alone is not sufficient for producing anaesthesia. METHODS: To compare propofol and GABA, their interaction with the GABAA receptor beta subunit and actin were studied in three cellular fractions of cultured rat neurons using Western blot technique. RESULTS: Propofol tyrosine phosphorylated the GABA(A) receptor beta2 (MW 54 and 56 kDa) and beta3 (MW 57 kDa) subtypes. The increase was shown in both the cytoskeleton (beta2(54) and beta2(56) subtypes) and the cell membrane (beta2(54) and beta3 subtypes). Concurrently the 56 kDa beta2 subtype was reduced in the cytosol. Propofol, but not GABA, also tyrosine phosphorylated actin in the cell membrane and cytoskeletal fraction. Without extracellular calcium available, the amount of actin decreased in the cytoskeleton, but tyrosine phosphorylation was unchanged. GABA caused increased tyrosine phosphorylation of beta2(56) and beta3 subtypes in the membrane and both beta2 subtypes in the cytoskeleton but no cytosolic tyrosine phosphorylation. CONCLUSION: The difference between propofol and GABA at the GABA(A) receptor was shown to take place in the membrane, where the beta2(54) was increased by propofol and instead the beta2(56) subtype was increased by GABA. Only propofol also tyrosine phosphorylated actin in the cell membrane and cytoskeletal fraction. This interaction between the GABAA receptor and actin might explain the difference between anaesthesia and physiological neuronal inhibition.

Effects of increases in the inspired oxygen fraction on brain surface oxygen pressure fields in pig and man.

In six patients undergoing neurosurgical operation, brain surface oxygen pressure was studied during an increase of the inspired oxygen fraction (FiO2). The eight-channel oxygen surface electrode (MDO-electrode) was placed directly on the brain cortex. FiO2 was increased to four levels, from baseline level 0.21 to 0.3, 0.5, 0.7 and 1.0, respectively. During these four stages and FiO2 0.21, brain surface oxygen pressure (PtO2) was measured. The physiological variables such as blood pressure, PaCO2, pH and temperature were stable throughout the study. The results are presented as mean values +/- s.d. and a PtO2 histogram for each FiO2-level. Already at an FiO2 of 0.3 (at a PaO2 of 16.3 +/- 3.4 kPa) scattered histograms were seen in five of six patients. A scattered histogram indicates disturbed microcirculation. At the FiO2 levels of 0.5, 0.7 and 1.0, all histograms were scattered. The PtO2 values did not increase proportionally to PaO2 at FiO2 levels 0.3, 0.5 or 0.7. But at FiO2 1.0 four patients had normal mean PtO2 values and two patients very high mean PtO2 values. It is possible that the four patients with normal PtO2 values succeeded in regulating the cerebral microcirculation as a response to the high FiO2 leading to a high PaO2 (60.1 +/- 6.4 kPa). The same study was initially done on six pigs in which the regional cerebral blood flow (rCBF) was also measured. MDO-electrode measurements at different FiO2-levels gave the same results as in the patients. rCBF decreased when FiO2 was increased.

Central circulation during halothane-diethyl-ether azeotrope and isoflurane anaesthesia in the pig.

The fatal anaesthetic ratio (FAR) has been determined for halothane-diethyl-ether (HE) in pigs, and the central circulation during hypovolaemia has been investigated using a well-documented agent such as isoflurane as a standard. The fatal anaesthetic ratio for HE in pigs was (3.21/1.03) = 3.12. This is high compared to the FAR for halothane of 1.7. The central circulation was investigated in 12 pigs which were randomly allocated to either HE or isoflurance anaesthesia, respectively. Baseline values were recorded when they were stable at 1.3 MAC of the volatile anaesthetic used. The pigs were bled 30% of their blood volume, and measurements were made at 5 and 30 min. There was one significant difference between these groups in central circulation: the blood pressure was higher at baseline measurement in the HE group. At 5 min and 30 min, there were no significant differences between these groups. There was a general depression of central circulation without any sign of decreased contractility. HE anaesthesia is well tolerated during hypovolaemia in pigs.

Effects of hypotension induced by adenosine on brain surface oxygen pressure and cortical cerebral blood flow in the pig.

Six pigs were anaesthetized with ketamine in combination with fentanyl and droperidol and paralysed with pancuronium. The pigs were tracheotomized and ventilated mechanically. Mean arterial blood pressure, MABP, was lowered from 97 +/- 21 mmHg stepwise to 58 +/- 2, 33 +/- 4 and 22 +/- 4 mmHg by intravenous infusion of adenosine (4-8 mg kg-1 min-1). Regional cerebral blood flow (rCBF) was measured directly onto the cortex of the brain by local atraumatic application of 133xenon. Brain surface oxygen pressure (PtO2) was obtained using a multiwire oxygen surface electrode. At the level of 60 mmHg, rCBF showed a significant increase, while flow values were not changed from initial values with further hypotension. Ten minutes after adenosine was discontinued, rCBF showed a rebound effect with higher values than initially. During normotension mean cortical PtO2 varied between 2.1 KPa and 3.9 kPa. During adenosine infusion PtO2 was increased at MABP-levels of 60 and 30 mmHg, while at 20 mmHg a decrease was seen in all animals. After discontinuation of the adenosine infusion, PtO2 values were higher than those measured at the initial normotension, a similar rebound phenomenon as seen with rCBF. During the experiments all hypotensive levels could be maintained at constant level without progressively increasing infusion rates, indicating no tachyphylaxis during these time periods. After discontinuation of the drug, blood pressure did not fully reach pre-hypotensive level within 10 min. Thus, hypotension induced by adenosine down to a MABP of 30 mmHg in animal experiments does not cause deterioration in either cerebral blood flow or oxygen pressure.

Specific blood flow reducing effects of hyperoxaemia on high flow capillaries in the pig brain.

The mechanisms behind oxygen mediated changes in tissue blood flow remain unsettled. Today these are thought to (from experiments on separate vessels and other tissues than the brain) operate through the vessels themselves, probably by involvement of the endothelium in the distal parts of the vascular tree. The aim of this study was to investigate how hyperoxaemia affects the cerebrocortical capillary blood flow distribution in order to gain further knowledge of oxygen mediated blood flow regulating mechanisms. The experiments were performed on seven ventilated anaesthetized pigs. A multiwire Clark-type microelectrode, placed on the brain surface (motor cortex), was used for capillary blood flow (hydrogen clearance) and oxygen pressure measurements, both of which were made at normoxaemia (arterial PO2 14.4 kPa) and hyperoxaemia (arterial PO2 50.4 kPa)(the animals serving as their own control). Blood pressure, arterial PCO2 and pH remained unchanged throughout the experiments. During hyperoxaemia a 11% reduction in the cerebrocortical capillary blood flow was found (P < 0.001). This flow reduction was seen mainly in two capillary blood flow classes (6/7 animals). In parallel a heterogeneous increase in the cerebrocortical oxygen pressures from 4.5 to 10.1 kPa (mean) (P < 0.001) was found. These results show that hyperoxaemia causes a selective reduction in capillary blood flow affecting capillaries at specific flow levels. A finding that suggests, for the brain, that both the oxygen sensor and effect mechanism is situated distally, in the vascular tree.

Morphine, morphine-6-glucuronide, and morphine-3-glucuronide in cerebrospinal fluid and plasma after epidural administration of morphine.

BACKGROUND AND OBJECTIVES: It has been suggested that the potency of epidural morphine might be explained by spinal metabolism to the active and potent metabolite morphine-6-glucuronide (M6G). The main objective of this study was to describe the early pharmacokinetics of epidurally administered, morphine with special attention to the appearance of the glucuronated metabolites in cerebrospinal fluid (CSF). METHODS: Morphine was administered epidurally to eight patients scheduled for major abdominal surgery. The concentrations of morphine and its 6-glucuronide and 3-glucuronide metabolites were monitored in blood and CSF at 10, 30, 60, and 120 minutes and 10 and 24 hours. Postoperative pain was estimated on a visual analog scale, and analgesia requirements (administered by a patient-controlled technique) were recorded. RESULTS: Only traces of the metabolites were found in CSF and in only two patients throughout the 24 hours. Both metabolites appeared rapidly (within 30 minutes) in plasma in all patients and were found in plasma throughout the study period. Morphine concentration peaked in CSF within 30 minutes at a very high level; in plasma, it peaked at 10 minutes. No correlation was seen between initial or later concentrations of morphine in CSF and postoperative pain or morphine requirements. CONCLUSIONS: No evidence of spinal metabolism of morphine could be found. Rapid distribution of morphine to CSF and plasma occurred after epidural administration. No value of initial CSF morphine concentrations for prediction of analgesic requirements could be demonstrated.

Local application of 133Xenon for measurement of regional cerebral blood flow (rCBF) during halothane, enflurane, and isoflurane anesthesia in humans.

It is well known that halothane causes an increase in cerebral blood flow (CBF). In this study the effects of halothane, enflurane, and isoflurane on regional cerebral blood flow (rCBF) in humans were determined in the presence of 70% N2O at a combined MAC concentration of 1.5. CBF was determined in 24 patients from the washout of locally applied 133Xenon with the use of an external scintillation. All 24 patients (control n = 6, halothane n = 6, enflurane n = 6, and isoflurane n = 6) were undergoing neurosurgical procedures. All patients were anesthetized with thiopental, fentanyl, droperidol, and 70% N2O in oxygen and paralyzed with pancuronium. The measurements were performed after the dura had been opened and before definitive surgery. The first measurement was done in the absence of any volatile agent, and the wash-out curve was registered for 6 min. The second measurement was done after one of the volatile agents had been added for at least 20 min and had reached a concentration of 0.58% for halothane, 1.14% for enflurane, or 1.0% for isoflurane in the expiratory gases in order to obtain about 1.5 MAC with each volatile anesthetic. The anesthetic concentrations were measured with the Engström multigas analyzer EMMA. The physiologic variables changed very little throughout the period of observation. Body temperature, heart rate, blood pressure, PaCO2, and PaO2 were stable. Ephedrine was used to maintain a stable arterial pressure. At approximately 1.5 MAC, halothane (plus N2O) increased rCBF to nearly three times (166%) the control value, while enflurane induced only a slight increase (35%) in rCBF.(ABSTRACT TRUNCATED AT 250 WORDS)

Propofol decreases random and chemotactic stimulated locomotion of human neutrophils in vitro.

We have studied the influence of clinical concentrations of propofol (2,6-diisopropyl phenol), emulsified propofol (Diprivan) and the emulsifier of propofol (Intralipid 10%) on random and chemotactic locomotion of human polymorphonuclear leucocytes in an agarose assay. Random locomotion was decreased (P < 0.001) to a similar extent by the three drugs. Concentrations of propofol 2.5 micrograms ml-1 and greater, and of Diprivan 3.33 micrograms ml-1 and greater, also reduced chemotaxis (P < 0.05) against both zymosan-activated human serum (C5a) and N-formyl-methionyl-leucylphenylalanine (FMLP), used as chemoattractants. Intralipid reduced chemotaxis towards C5a but not towards FMLP. We conclude that propofol in clinically relevant concentrations may adversely affect leucocyte locomotion in vitro.

A tyrosine kinase regulates propofol-induced modulation of the beta-subunit of the GABA(A) receptor and release of intracellular calcium in cortical rat neurones.

Propofol, an intravenous anaesthetic, has been shown to interact with the beta-subunit of the gamma-amino butyric acid(A) (GABA(A)) receptor and also to cause changes in [Ca2+]i. The GABA(A) receptor, a suggested target for anaesthetics, is known to be regulated by kinases. We have investigated if tyrosine kinase is involved in the intracellular signal system used by propofol to cause anaesthesia. We used primary cell cultured neurones from newborn rats, pre-incubated with or without a tyrosine kinase inhibitor before propofol stimulation. The effect of propofol on tyrosine phosphorylation and changes in [Ca2+]i were investigated. Propofol (3 microg mL(-1), 16.8 microM) increased intracellular calcium levels by 122 +/- 34% (mean +/- SEM) when applied to neurones in calcium free medium. This rise in [Ca2+]i was lowered by 68% when the cells were pre-incubated with the tyrosine kinase inhibitor herbimycin A before exposure to propofol (P < 0.05). Propofol caused an increase (33 +/- 10%) in tyrosine phosphorylation, with maximum at 120 s, of the beta-subunit of the GABA(A)-receptor. This tyrosine phosphorylation was decreased after pre-treatment with herbimycin A (44 +/- 7%, P < 0.05), and was not affected by the absence of exogenous calcium in the medium. Tyrosine kinase participates in the propofol signalling system by inducing the release of calcium from intracellular stores and by modulating the beta-subunit of the GABA(A)-receptor.

Propofol induces changes in the cytosolic free calcium concentration and the cytoskeletal organization of cultured human glial cells and primary embryonic rat brain cells.

BACKGROUND: The site of action of the intravenous anesthetic drug propofol is uncertain. Therefore, we examined the effects of propofol on the cytosolic free calcium levels of cultured primary embryonic rat brain cells (80-85% neurons), and on the organization of the cytoskeleton in these rat cells and in a model system of cultured human glial cells (astrocytes). METHODS: Propofol was added to the cells as the clinically available solution Diprivan. Cytosolic free calcium changes in neurons were studied using Fura2 and a single-cell microfluorometric method. Fluorescence microscopy was used to study the organization of actin filaments and tubulin in detergent-extracted cells. RESULTS: An increase in the cytosolic free calcium concentration of 116 +/- 39 nM was seen shortly after the addition of 0.3 microgram.ml-1 propofol, and a propofol concentration of 0.03 microgram.ml-1 resulted in an increase in cytosolic free calcium concentration of the same magnitude, 119 +/- 42 nM. Most of the calcium (60-75%) came from the extracellular environment, and the rest was from intracellular stores. When neurons were depleted of intracellular calcium by 1,2-bis-5-methyl-amino-phenoxylethane-N,N'-tetra-acetoxymethyla cetate (MAPT/AM), no changes were seen in the actin organization of the cytoskeleton. Actin organization was affected by all concentrations of propofol, 0.3-50 micrograms.ml-1 (1.7-280 microM), when exposure to the drug was achieved by a 30-min incubation. After the incubation, the exposed cells were more rounded and exhibited increased ruffling activity, both at the periphery and on the cellular surface, and ring-shaped actin structures were also seen. These effects were concentration dependent and reversible, and reached a maximum after 20 min of incubation. Propofol had no apparent effect on the organization of tubulin. CONCLUSIONS: Propofol induced changes in the cytoskeletal organization of actin in cultured rat neurons and human glial cells. These changes must have been due to the increase in intracellular calcium seen shortly after the addition of propofol, since no effects on actin organization were seen when intracellular calcium was depleted.