Changes of blood pressure and cerebral arterio-venous oxygen content differences (AVDo2) with and without bupivacaine scalp infiltration during craniotomy

In 20 patients subjected to craniotomy for supratentorial cerebral tumours, the effect of scalp infiltration with bupivacaine before incision was evaluated by measuring mean arterial blood pressure (MABP) and cerebral arterio-venous oxygen content differences (AVDO2) repeatedly during the operation. All patients were given halothane 0.5% anaesthesia. Ten patients were given bupivacaine 0.25% and ten patients were given normal saline for scalp infiltration prior to incision. The study was performed in a double-blind randomized fashion. Significantly higher values of MABP (P less than 0.0005) after incision were found in the saline group compared to the bupivacaine group. Significantly lower values of AVDO2 (P less than 0.0005) after incision were seen in the saline group compared to the bupivacaine group. The results indicate that the increase in MABP associated with a decrease in AVDO2, suggesting an increase in CBF and cerebral hyperperfusion, is reduced by using bupivacaine scalp infiltration prior to incision.     

Cerebral blood flow, cerebral metabolic rate of oxygen and relative CO2 reactivity during neurolept anaesthesia in patients subjected to craniotomy for supratentorial cerebral tumours

In 10 patients subjected to craniotomy for supratentorial cerebral tumours in neurolept anaesthesia, cerebral blood flow (CBF) and cerebral metabolic rate of oxygen (CMRO2) were measured twice peroperatively by a modification of the Kety & Schmidt technique, using 133Xe. The relative CO2 reactivity was assessed indirectly as the % change of the arteriovenous oxygen difference (AVDO2) per mm change in PaCO2. The patients were premedicated with diazepam 10-15 mg perorally. For induction, thiopentone 4-6 mg/kg, droperidol 0.2 mg/kg and fentanyl 5 micrograms/kg were used, and for maintenance N2O 67% and fentanyl 4 micrograms/kg/h. During the first flow measurement the median and range of CBF was 30 ml/100 g/min (range 17-45), of AVDO2 8.0 vol % (range 4.1-9.5), and of CMRO2 2.28 ml O2/100 g/min (range 1.57-2.84). During the second CBF study, AVDO2 increased to 9.3 vol % (range 3.4-11) (P less than 0.05), and CMRO2 increased to 2.51 ml O2/100 g/min (range 1.88-3.00) P less than 0.05, while CBF was unchanged. The CO2 reactivity was present in all studies, median 1.8%/mmHg (range 0.5-15.1). The correlation coefficients between jugular venous oxygen tension/saturation, respectively, and CBF were high at tensions/saturations exceeding 4.0 kPa and 55%, indicating that hyperperfusion is easily unveiled by venous samples from the jugular vein during this anaesthesia.     

The effect of metoprolol upon blood pressure, cerebral blood flow and oxygen consumption in patients subjected to craniotomy for cerebral tumours

Hypertension and cerebral hyperperfusion are often seen in the immediate postoperative period after craniotomy for supratentorial tumours. Metoprolol is known to attenuate the postoperative hypertensive response after hypotensive anaesthesia and this study was carried out to evaluate the effect of metoprolol on cerebral blood flow (CBF) and cerebral metabolic rate of oxygen (CMRo₂) before extubation and cerebral arteriovenous oxygen content difference (AVDo₂), mean arterial blood pressure (MABP), Pao₂ and Paco₂ in a 180–min period after extubation. Twenty patients anaesthetized with thiopentone, fentanyl, nitrous oxide 67%, and halothane 0.5% were randomized to receive intravenous metoprolol or placebo at the end of the peroperative period. There were no significant differences in CBF– and CMRo₂ values between the two groups. In the period between closure of the dura and 5 min after extubation, an increase in MABP was observed in the control group ( P < 0.05), but not in the metoprolol group. During the same period a decrease in AVDo₂ was observed in both groups ( P < 0.05); during the next 10 min an increase was observed, but with no difference in AVDo₂ values between the groups. A higher level of Pao₂ in the metoprolol group was observed in the postoperative period. These findings suggest that peroperative treatment with metoprolol reduces postoperative MABP but does not influence the cerebral blood flow and metabolism.     

Cerebral blood flow and oxygen consumption during isoflurane and halothane anesthesia in man

In 13 patients, the effects on cerebral blood flow (CBF) and cerebral metabolic rate of oxygen (CMRO2) of isoflurane and halothane administered in a clinically relevant situation were studied. Measurements were performed during fentanyl/nitrous oxide (65%) anesthesia together with moderate hyperventilation (PaCO2 approx 4.5 kPa), and repeated after addition of 0.65 MAC of isoflurane (n = 6) or halothane (n = 7). CBF was measured after intravenous administration of 133xenon and CMRO2 was calculated from the arterial venous differences of oxygen content (AVDO2) determined in arterial and jugular venous bulb blood. CBF and CMRO2 (means +/- s.e. mean) determined prior to administration of volatile agents were 28 +/- 5 ml x 100(-1) x min-1 and 2.0 +/- 0.3 ml x 100 g-1 x min-1, respectively, in the isoflurane group. In the halothane group, CBF was 25 +/- 0.4 ml x 100 g-1 x min-1 and CMRO2 was 2.0 +/- 0.4 ml x 100 g-1 x ml-1. There were no significant intergroup differences. Isoflurane did not change CBF, whereas halothane produced an increase of 36% (P less than 0.05) compared to values obtained during fentanyl/N2O anesthesia. In addition, isoflurane caused a further decrease in CMRO2 of 12% (P less than 0.01) as compared to a 20% increase (P less than 0.05) with halothane. The cerebral metabolic depression caused by the short-acting anesthetic induction agents would be expected to decrease with time, and could partly explain the observed increase in CMRO2 produced by halothane. The study suggests that the cerebrovascular and metabolic properties of isoflurane differ from those of halothane, also in man.     

Plasma Catecholamines During Surgical Stress: Differences Between Neurolept and Enflurane Anaesthesia

To evaluate the influence of enflurane and neurolept anaesthesia on the sympatho-adrenal response to surgery, arterial plasma concentrations of adrenaline and noradrenaline were measured at 11 carefully defined events before, during and after cholecystectomy in two groups of five patients. During steady-state anaesthesia prior to operation and after cholangiography, when the operative procedure had been interrupted for 10 min, adrenaline concentrations were similar in the two groups. During periods of stress such as intubation, skin incision and abdominal exploration, adrenaline levels were 4–6 times higher in the neurolept patients compared to the enflurane patients ( p <0.01), in whom adrenaline levels were very stable. Noradrenaline levels also varied with stress but without difference between the two groups. Systolic blood pressure was approximately 20 mmHg higher during operation in the neurolept group than in the enflurane group ( P <0.05). It is concluded that enflurane blocks the sympatho-adrenal response to surgical stress more effectively than conventional neurolept anaesthesia.     

Effects of propofol on intraocular pressure in surgery of strabismus in children

Propofol was assessed for eye surgery in 20 children. ASA group I or II, 2-14 year-old, randomly assigned to 2 equal groups. Premedication, analgesia and muscle paralysis were similar in both groups. Group P patients were given an induction dose of 4 mg.kg-1 propofol, followed by an infusion of 15 mg.kg-1.h-1 for the first half hour, and then 10 mg.kg-1.h-1 to maintain anaesthesia. Group C patients were given 10 mg.kg-1 thiopentone for induction and halothane for maintenance. The quality of anaesthesia was assessed by monitoring adverse effects, heart rate, blood pressure, the length of anaesthesia, the delay of the first spontaneous breath and eye opening, and extubation. Intraocular pressure was measured before and 3 min after intubation, and 5 min after extubation. The quality of anaesthetic induction and maintenance were very similar in both groups. Pain occurred more frequently at the injection site with propofol (p less than 0.01). Children in group P recovered more quickly, and extubation was possible much earlier in this group (p less than 0.05). However, restlessness was significantly more frequent in group P (n = 9) than in group C (n = 1) (p less than 0.01). Systolic, diastolic blood pressure and heart rate were significantly lower in group P (p less than 0.05; 0.001; 0.001 respectively). No significant decrease in intraocular pressure in both groups was observed. The use of propofol for eye surgery in children is acceptable, despite some restlessness during recovery.     

The effect of ketanserin upon postoperative blood pressure, cerebral blood flow and oxygen metabolism in patients subjected to craniotomy for cerebral tumours

Hypertension and cerebral hyperperfusion are often seen in the immediate postoperative period after craniotomy for supratentorial tunours. This study was performed to evaluate the effect of ketanserin, given at the end of the peroperative period, upon cerebral blood flow (CBF), and cerebral metabolic rate of oxygen (CMRO₂) before extubation. Mean arterial blood pressure (MABP), cerebral arterio-venous oxygen content difference (AVDO₂), PaO₂, and PaCO₂ were repeatedly measured during the operation, and 180 minutes after extubation. Ten patients were included in this study. The results were compared to those from a recent study in which ten patients served as control. All patients were anaesthetized with thiopentone, fentanyl, nitrous oxide 67%, halo-thane 0.5% anesthesia. Ten patients were given ketanserin 10–20 mg (mean 18,5 mg) before extubation. There was no significant difference in CBF- and CMRO₂ values between the two groups. During the period between closure of the dura and 5 minutes after extubation, an increase in MABP was observed in the control group ( P <0.05) but not in the ketanserin group. During the same period, a decrease in AVDO₂ was observed in both groups ( P <0.05) and during the next 10 minutes an increase was observed. However, no difference in AVDO₂ values between the two groups was found.
These findings suggest that peroperative treatment with ketanserin reduces postoperative hypertension without influencing the cerebral blood flow or metabolism.     

Hemodynamics of coronary surgery patients under isoflurane and neuroleptanalgesia

The haemodynamic effects of isoflurane- and modified neurolept-anaesthesia were evaluated in 24 patients undergoing coronary artery bypass grafting. 12 patients (isoflurane group) were anaesthetized after an induction with 1.5 mg/kg methohexital and a unique dose of 0.005 mg/kg fentanyl with isoflurane (0.5-1.5 Vol%), N2O/O2 and pancuronium. 12 patients (neurolept group) received fentanyl (0.04 mg/kg), flunitrazepam, pancuronium and N2O/O2. Haemodynamic measurements were made before anaesthesia, in steady state anaesthesia, after sternotomy, after extracorporal circulation, after thoracic closure and one, two and four hours after the end of the operation. Between both groups we could not find significant differences in the haemodynamic parameters RAP, PAP, PCWP, PVR, CI, SVI, AP and CPP. However in the isoflurane group the peripheral vascular resistance (TPR) was significantly lower in steady state anaesthesia and after sternotomy. In the neurolept group the heart rate (HR) was significantly higher after bypass than in the isoflurane group. We believe, that at this time fentanyl analgesia was reduced. Before extracorporal bypass, patients with isoflurane anaesthesia had a lower arterio-mixed venous oxygen content difference (AVDO2) than patients with neurolept anaesthesia. Therefore it can be supposed that isoflurane lowers the oxygen demand more than neurolept anaesthesia. After surgery neurolept anaesthetized patients showed postanaesthetic shivering more frequently than those in the isoflurane group. We suggest that the vasodilating effect of isoflurane induces a homogeneous heat gain during warming the patients up, and that, therefore, in patients of the isoflurane-group AVDO2 and TPR were lower than in the patients of the neurolept-group during the first postoperative hours.(ABSTRACT TRUNCATED AT 250 WORDS)     

Per- and postoperative changes in the arterio-venous oxygen content difference (AVDO2) in patients subjected to craniotomy for cerebral tumours

Summary Sixteen patients with supratentorial cerebral tumours were subjected to craniotomy under thiopentone, fentanyl, nitrous oxide, halothane anaesthesia during moderate hypocapnia (PaCO₂ level 4.0 kPa). The arterio-venous oxygen content difference (AVDO₂) was measured peroperatively, and repeatedly during the first three hours after extubation.Peroperatively the level of AVDO₂ averaged 8.0 vol% during opening of the dura, and decreased to 7.0 vol% during closure of the dura (P<0.05). Immediately after extubation the AVDO₂ decreased to 4.3 vol% (P<0.05), and during the next 3 hours a gradual increase to 5.8 vol% (P<0.05) was disclosed. In individual cases the postoperative changes in AVDO₂ correlated fairly well with changes in mean arterial blood pressure (MABP), but other factors including duration of the operation, age of the patients, size of the tumour, level of PaCO₂ and adaptation to prolonged hyperventilation during operation are supposed to be responsible for the low levels of AVDO₂ observed in the postoperative period.     

Aerobic, anaerobic and combination estimates of cerebral hypoperfusion during and after cardiac surgery

We studied 15 patients undergoing cardiac surgery involving hypothermic cardiopulmonary bypass (CPB). Cerebral arteriovenous difference in oxygen content (AVDO2) was significantly less during CPB and for up to 18 h after operation compared with pre-CPB values (P < 0.05). There were no significant changes in mean jugular bulb oxyhaemoglobin saturation (SjvO2), cerebral arteriovenous difference in lactate content or lactate-oxygen index (LOI). SjVO2 and arterial carbon dioxide tension (PaCO2) (P = 0.005) were positively correlated as were AVDO2 and haemoglobin concentration (P = 0.012). AVDO2 and PaCO2 (P = 0.007) were negatively correlated as were LOI and arterial oxyhaemoglobin saturation (P = 0.037). There were no significant correlations between mean arterial pressure and any of the variables. SjVO2 and AVDO2 may require correction for changes in PaCO2 and haemoglobin concentration before relating these variables to cerebral outcome.      

A comparison of the cerebral hemodynamic effects of sufentanil and isoflurane in humans undergoing carotid endarterectomy

Prompted by reports of potentially deleterious cerebral vasodilation by the synthetic opioid sufentanil, the authors compared the effects of either isoflurane/N2O and sufentanil/N2O on cerebral blood flow (CBF), arteriovenous difference in oxygen content (AVDO2), and CBF reactivity to changes in PaCO2 during carotid endarterectomy. Cerebral blood flow was measured using the iv method of 133-Xe CBF determination and AVDO2 was measured using systemic arterial-jugular venous oxygen content differences. Patients, age 68 +/- 1 yr (mean +/- SE), received either isoflurane (n = 10), 0.75% in O2 and N2O, 1:1; or sufentanil (n = 10), 1.5-2 micrograms/kg bolus and then 0.2-0.3 micrograms.kg-1.h-1 infusion in addition to O2 and N2O, 2:3. Measurements were made immediately before carotid occlusion, and then at two levels of PaCO2 (approximately 32 and 42 mmHg) after insertion of a temporary in-dwelling bypass shunt. Prior to carotid occlusion, there was no significant difference in CBF (ml.100 g-1.min-1) between patients receiving isoflurane (22 +/- 3) or sufentanil (20 +/- 2). Similarly, there was no difference in AVDO2 (vol-%) between isoflurane (4.5 +/- 0.7) and sufentanil (5.4 +/- 0.8) groups. Using a two-way ANOVA design with anesthetic as the between-group factor and elevation of PaCO2 as the within-group repeated measure, there was a significant effect of hypercarbia to increase CBF (P less than 0.0001) and decrease AVDO2 (P less than 0.001). The product of AVDO2 and CBF, which reflects cerebral metabolic oxygen consumption, remained constant (P = 0.364).(ABSTRACT TRUNCATED AT 250 WORDS)     

The Modifying Effect of Spinal Anaesthesia on Intra- and Postoperative Adrenocortical and Hyperglycaemic Response to Surgery

Plasma cortisol and glucose were measured in 24 patients undergoing abdominal hysterectomy during spinal anaesthesia with 0.5% hyperbaric tetracaine or neurolept anaesthesia. The sensory level of analgesia to pinprick extended to at least T4 before skin incision in the spinal group. The mean sensory analgesic level regressed almost linearly, reaching the fourth lumbar segment 4 h after incision. Plasma cortisol and glucose measurements from before to 9 h after skin incision showed significant increases in both parameters during and after surgery. Plasma cortisol and glucose levels were significantly lower during and immediately after surgery in the spinal group, but later postoperatively the mean levels were similar in the two groups. The increase in plasma cortisol 1 h after skin incision in the spinal group correlated to the segmental level of analgesia at that time (r = 0.77, P less than 0.01) and a similar correlation was found with regard to plasma glucose changes (r = 0.60, P less than 0.05). The regression lines showed that maintenance of a sensory analgesic level about the fourth thoracic segment prevented the adrenocortical and hyperglycaemic response to surgery. These findings are in accordance with the anatomical assumption that the upper segmental level of visceral afferent input to the spinal cord is about the fourth thoracic segment. Our results further demonstrate that the inhibitory effect of spinal anaesthesia on the stress response to surgery is transient, and correlates to the regression of sensory analgesia.     

Moderate Hypotensive Anaesthesia for Reduction of Blood Loss During Total Hip Replacement

Thirty-two consecutive patients scheduled for total hip replacement were randomly allocated to receive either neurolept anaesthesia or halothane anaesthesia. In the halothane group, systolic blood pressure was reduced to 10.69-13.33 kPa in normotensive patients, and to 13.33-16.0 kPa in hypertensive patients by adjusting the inspired halothane concentration and using supplementary fentanyl when necessary. In the neurolept group, no attempt was made to reduce blood pressure below the level achieved with adequate anaesthetic doses of fentanyl and droperidol. The average peroperative blood loss in the halothane group was 809 ml (range 250–1700 ml); this was significantly lower than in the neurolept anaesthesia group in which an average blood loss of 1909 ml (range 600–4900 ml) occurred. Moderate hypotensive halothane anaesthesia is recommended as an anaesthetic technique for total hip replacement.     

Baroreflex activity in carotid endarterectomy during general anesthesia

The baroreceptor reflex was studied in eleven patients, aged 69 +/- 6 years, scheduled for carotid endarterectomy under general anaesthesia. Nine were hypertensive. The anaesthetic protocol was the same for all the patients: premedication with morphine and scopolamine, induction with 5 mg.kg-1 thiopentone, 6 micrograms.kg-1 fentanyl and 0.01 mg.kg-1 pancuronium bromide. All the patients were intubated and ventilated with a mixture of nitrous oxide and oxygen. Fentanyl, 100 micrograms, was routinely given at the time of incision. Baroreflex sensitivity was tested using Smyth's method, with a bolus of 75 micrograms trinitrin and plotting changes in heart rate against those in systolic blood pressure. Electrocardiogram, invasive arterial blood pressure and airway pressure were simultaneously recorded. PaCO2 and PaO2 were measured during arterial clamping. The tests were carried out before clamping, 2 min later and 10 to 20 min after the last injection of fentanyl. In the seven patients for whom clamping lasted more than 15 min, a further test was carried out after administration of 0.4 +/- 0.05 vol% halothane (Datex analyser) for 5 min. During anaesthesia, baroreflex sensitivity was low (1.8 +/- 0.3 ms.mmHg-1). After clamping, there was only a significant change in Pasys, with no changes in heart rate or blood gas values (129 +/- 8 mmHg before clamping; 167 +/- 12 mmHg after clamping; n = 8; p less than 0.01). After halothane administration, the sensitivity slope decreased, but not significantly. Moreover, halothane decreased the R-R intervals (1140 +/- 84 after clamping; 963 +/- 76 under halothane; n = 6; p less than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)     

Natural killer cell activity in patients undergoing minor gynaecological surgery

Natural killer (NK) cell activity was investigated in 24 patients who were undergoing minor gynaecological surgery performed during neurolept, halothane or spinal anaesthesia. The endocrine response to anaesthesia and surgery was monitored using serum cortisol and plasma catecholamine estimations. The surgical trauma was insufficient to elicit an endocrine stress response. No changes in NK cell cytotoxicity occurred in any group during premedication, anaesthesia or surgery. Post-operatively the NK cell activity fell transiently in the two groups that received general anaesthesia (P less than 0.05), whereas no reduction was found in the group that was given spinal anaesthesia. The results indicate that minor surgery induces only small variations in NK cell cytotoxicity and no conclusions can be made, therefore, concerning the influence of different anaesthetic techniques on NK cell cytotoxicity.     

Cerebral blood flow and metabolism during adenosine–induced hypotension in patients undergoing cerebral aneurysm surgery

The effects of adenosine-induced hypotension on cerebral blood flow (CBF), cerebral metabolic rate of oxygen (CMRO2), and cerebral lactate production, together with systemic haemodynamics, were studied in 10 patients undergoing cerebral aneurysm surgery in neurolept anaesthesia with controlled hyperventilation. CBF changes were determined in six of the patients with a retrograde thermodilution technique in the jugular vein. Hypotension was induced with a continuous infusion of adenosine in the superior vena cava. The dose range was 0.06-0.35 mg/kg/min, and this caused a 42% reduction in mean arterial blood pressure (MABP) from 79 +/- 4 to 46 +/- 1 mmHg (10.5 +/- 0.5 to 6.1 +/- 0.1 kPa) through a profound reduction in systemic vascular resistance (SVR), which amounted to 61%. No significant change occurred in CBF. Whole body AV-difference of oxygen was decreased by 37%, and cerebral AV-difference by 28%, corresponding to reductions in whole body oxygen uptake and CMRO2 of 16 and 17%, respectively. Cerebral AV-difference of lactate did not change. In the posthypotensive period MABP was increased by 10%, together with a minor increase in CBF (15%). It is concluded, that adenosine-induced hypotension at MABP levels between 40-50 mmHg (5.3-6.7 kPa) does not affect cerebral oxygenation unfavourably, and may even offer a protective effect by reducing cerebral oxygen demand. The slight CBF increase in the posthypotensive period was probably secondary to an increase in MABP together with a blunted autoregulation, but in no case was this effect considered to be harmful for the patient.     

Catecholamine and Endocrine Response in Children During Halothane and Enflurane Anaesthesia for Adenoidectomy

In 28 children undergoing adenoidectomy, plasma concentrations of catecholamines, ACTH and cortisol were measured. Fourteen children were anaesthetized with halothane (seven non-intubated, seven intubated) and 14 with enflurane (seven non-intubated, seven intubated). During undisturbed anaesthesia, plasma catecholamines were significantly higher with halothane than with enflurane (P less than 0.05). Immediately after surgery, catecholamines were increased up to 300% in the halothane groups. In the enflurane groups, however, the catecholamine concentrations remained unchanged. This difference between the two agents, after surgery, was statistically significant (P less than 0.01 for intubated and P less than 0.001 for non-intubated children). Fifteen minutes postoperatively no difference was found in plasma concentrations between the groups. In all four groups, plasma concentrations of ACTH and cortisol increased similarly during the procedure. It was concluded that plasma catecholamines were higher during halothane than during enflurane anaesthesia in children undergoing adenoidectomy. This difference may be caused by a stimulating effect of halothane on the endogenous catecholamine release. This increased sympathomimetic response during halothane anaesthesia was correlated to the incidence of ventricular arrhythmias previously found with this agent during adenoidectomy.     

Dose-response Curves for Vecuronium during Halothane and Neurolept Anaesthesia: Single Bolus versus Cumulative Method

The purpose of this study was to compare the incremental, cumulative dose method and the single bolus injection technique for construction of dose-response curves for vecuronium. Dose-response curves were determined in 77 patients divided into four groups according to the anaesthetic given and the method used for construction of dose-response curves. The regression lines corresponding to the four dose-response curves were found to be parallel. For vecuronium ED50 during neurolept anaesthesia was found to be 28 micrograms kg-1 with the single bolus injection technique and 35.2 micrograms kg-1 with the incremental, cumulative dose method (P less than 0.05). During halothane anaesthesia, ED50 was found to be 25.7 micrograms kg-1 and 26.2 micrograms kg-1, respectively (P greater than 0.05). Potentiation of vecuronium by halothane was found with the cumulative method only. It is concluded that the incremental, cumulative dose method is not suitable for potency determinations of vecuronium.     

Cardiovascular and endocrine effects of clonidine premedication in neurosurgical patients

The present study was conducted to examine the haemodynamic and endocrine effects of clonidine, given as sole preanaesthetic medication, in neurosurgical patients. Nineteen patients of ASA physical status I and II, subjected to craniotomy, randomly received po premedication of either clonidine (300 micrograms, n = 9) or placebo (n = 10). Blood pressure and heart rate were monitored continuously, while arterial blood samples were collected at specific times, from induction of anaesthesia to recovery, for the measurement of plasma concentrations of epinephrine, norepinephrine, cortisol, aldosterone, and glucose. Clonidine treatment led to a decrease in mean arterial blood pressure (MABP), heart rate (HR), and plasma cortisol and aldosterone concentrations throughout the study, compared with placebo (P less than 0.05). Clonidine, however, did not prevent increases in MABP (16 +/- 5 mmHg, mean +/- SE, P less than 0.05) and HR (18 +/- 4 bpm, P less than 0.05) during induction of anaesthesia, which was comparable to the placebo group. Plasma catecholamine concentrations did not differ between the two groups. Plasma glucose concentrations increased in both groups at the end of the study (P less than 0.05), but were lower in clonidine-treated patients (P less than 0.05). Though statistically significant, the observed inhibitory haemodynamic and endocrine effects of clonidine seem to be of minor clinical importance. As the action of clonidine on cerebral blood flow regulation is not well known, we see no advantage in the preanaesthetic administration of clonidine to neurosurgical patients with normal cardiovascular status.     

The effect of halothane and isoflurane on plasma cytokine levels

The aim of this study was to investigate the effect of halothane vs. isoflurane on cytokine production during minor elective surgery. Forty adult patients, ASA I-II were randomly allocated to receive halothane or isoflurane. Venous samples for interleukin (IL)-1beta, IL-2, IL-6, tumour necrosis factor-alpha (TNF-alpha) and interferon-gamma (IFN-gamma) were taken before anaesthesia, before incision, at the end of anaesthesia and 24 h postoperatively. In both groups, IL-6 and TNF-alpha levels remained low throughout the study period. Before incision, in both groups IL-1beta and IFN-gamma showed a decrease (p<0.01 for IL-1beta in isoflurane group and p<0.05 for the others) compared with pre-induction. By the end of anaesthesia and surgery, IL-1beta had increased significantly (p<0.05) and IFN-gamma had decreased significantly (p<0.05) in both groups compared with pre-incisional levels. By 24 h postoperatively in both groups, IL-1beta had decreased significantly (p<0.05), whereas IFN-gamma had increased significantly (p<0.05) compared with the end of anaesthesia and surgery level. Pre-incisionally, IL-2 increased in the halothane group (p<0.01), whereas it decreased significantly in the isoflurane group (p<0.001) compared with the pre-induction level. By the end of anaesthesia and surgery and by 24 h postoperatively, IL-2 had decreased significantly in the halothane group (p<0.001), whereas it increased significantly in the isoflurane group (p<0.001) compared with pre-incision and end of anaesthesia and surgery levels, respectively.