Biomedical subjects

S Kaukinen

Publications and source records attributed to S Kaukinen.

At least 37 records · Page 2Linked to original sources

PubMed2001

Effect of ischemic preconditioning on myocardial protection in coronary artery bypass graft patients : can the free radicals act as a trigger for ischemic preconditioning?

OBJECTIVE: To investigate the interrelationship of free radicals (FRs), ischemic preconditioning (IP), and hemodynamic function in coronary artery bypass graft (CABG) patients. DESIGN: Prospective, randomized, and controlled clinical study. PATIENTS: Forty CABG patients were randomized into an IP group (n = 20) and a control group (n = 20). INTERVENTION: The IP group was preconditioned with two cycles of two-min ischemia followed by 3-min reperfusion before cross-clamping. MEASUREMENT AND RESULTS: FR content in coronary sinus blood was measured directly using alpha-phenyl-N-tert-butylnitrone-electron spin-trapped spectroscopy. A small amount of FRs was generated after the IP protocol (5.6% above the baseline) but not in control subjects. A larger amount was generated 10 min after declamping in both groups (8.4% in IP protocol and 7.7% in control subjects). Hemodynamic function recovered better in the IP group at 1 h and 6 h after declamping. There was a significant negative correlation between FR generation after declamping and left ventricular stroke work index (LVSWI) at 1 h and 6 h after declamping (r = -0.71 and - 0.59, respectively) in the control subjects but not in the IP group. There was a significant positive correlation between FR generation after the IP protocol and cardiac index at 1 h and 6 h (r = 0.50 and 0.61, respectively) and LVSWI at 1 h and 6 h (r = 0.56 and 0.54, respectively) after declamping in the IP group but not in the control subjects. CONCLUSION: FR generation after the operation correlates with ventricular functional depression in CABG patients. IP protects the stunning heart but does not alter FR generation. The association of better hemodynamic recovery after CABG with FR generation during the IP period suggests that FRs might act as one of the triggers for IP.

Aged↗

PubMed2001

Cardioprotective effect of adenosine pretreatment in coronary artery bypass grafting.

OBJECTIVE: There are several reports of the use of adenosine as a cardioprotective agent during cardiac surgery. Adenosine treatment might affect neutrophils and inflammatory mediators. The present prospective randomized study was designed to investigate the effect of adenosine pretreatment on myocardial recovery and inflammatory response in patients undergoing elective coronary artery bypass surgery. DESIGN: A prospective, randomized, controlled study. SETTING: Operative unit and ICU in a university hospital in Finland. PATIENTS: Thirty male patients undergoing primary, elective coronary revascularization. INTERVENTIONS: Patients in the adenosine group received a 7-min infusion of adenosine (total, 650 microg/kg) before the initiation of cardiopulmonary bypass. MEASUREMENTS: Postoperative creatine kinase (CK)-MB release and hemodynamics were recorded. Perioperative leukocyte and cytokine release were measured. RESULTS: Adenosine pretreatment resulted in less CK-MB release and an improved postbypass cardiac index. Similar leukocyte counts and cytokine responses were seen in both groups perioperatively. Neutrophil counts were similar between the groups before and after myocardial ischemia when measured simultaneously in arterial and coronary sinus blood. CONCLUSIONS: The present results support the hypothesis that adenosine pretreatment is cardioprotective in humans, but the present dose failed to regulate the inflammatory responses after coronary artery bypass grafting.

Adenosine↗

PubMed2000

Intercellular adhesion molecule-5 induces dendritic outgrowth by homophilic adhesion.

Intercellular adhesion molecule-5 (ICAM-5) is a dendritically polarized membrane glycoprotein in telencephalic neurons, which shows heterophilic binding to leukocyte beta(2)-integrins. Here, we show that the human ICAM-5 protein interacts in a homophilic manner through the binding of the immunoglobulin domain 1 to domains 4-5. Surface coated ICAM-5-Fc promoted dendritic outgrowth and arborization of ICAM- 5-expressing hippocampal neurons. During dendritogenesis in developing rat brain, ICAM-5 was in monomer form, whereas in mature neurons it migrated as a high molecular weight complex. The findings indicate that its homophilic binding activity was regulated by nonmonomer/monomer transition. Thus, ICAM-5 displays two types of adhesion activity, homophilic binding between neurons and heterophilic binding between neurons and leukocytes.

Animals↗

PubMed2000

Beneficial effects of ischemic preconditioning on right ventricular function after coronary artery bypass grafting.

BACKGROUND: Preservation of right ventricular myocardium is unsatisfactory in patients with critical stenosis or occlusion of the right coronary artery. The aim of this study was to investigate whether ischemic preconditioning (IP) improved the recovery of right ventricular function after coronary artery bypass grafting. METHODS: Forty patients with three-vessel disease who had coronary artery bypass grafting were randomly assigned to the IP group (n = 20) or control group (n = 20). In the IP group, two cycles of two minutes of ischemia after three minutes of reperfusion were given before cross-clamping. Hemodynamic data were collected. Right ventricular ejection fraction was measured by thermodilution. RESULTS: Right ventricular ejection fraction and right ventricular systolic volume index were decreased post-operatively (lowest value at 6 hours postoperatively). The changes in right ventricular ejection fraction were significantly milder in the IP group postoperatively (p = 0.012). The decrease in right ventricular systolic volume index postoperatively was also less in IP patients (p = 0.002). Fewer inotropic drugs were used in the IP group compared with controls. CONCLUSIONS: Ischemic preconditioning had a myocardial protective effect on recovery of right ventricular contractility in patients who had coronary artery bypass grafting.

Aged↗

PubMed2000

Adenosine with cold blood cardioplegia during coronary revascularization.

OBJECTIVE: To investigate whether adenosine in association with blood cardioplegia results in more rapid cardiac arrest or improved myocardial protection. DESIGN: A prospective, randomized, placebo-controlled double-blind clinical study. SETTING: Operative and intensive care units in a university hospital, Finland. PARTICIPANTS: Forty patients undergoing primary, elective coronary revascularization. INTERVENTION: Adenosine as a bolus dose, 12 mg intravenously, was given immediately before the induction of blood cardioplegia. MEASUREMENTS AND MAIN RESULTS: There were nonsignificantly higher serial serum values of CK (MB) (p = 0.33), troponin-T (p = 0.23), and troponin-I (p = 0.10) in the adenosine group. There were no differences between the groups in arrest time, blood pressure decrease, or lactate extraction. CONCLUSIONS: The adenosine regimen used in this study did not cause more rapid arrest with blood cardioplegia. The effect on cardioprotection was insignificant.

Adenosine↗

PubMed2000

Release of brain-specific creatine kinase and neuron-specific enolase into cerebrospinal fluid after hypothermic and normothermic cardiopulmonary bypass in coronary artery surgery.

BACKGROUND: Coronary artery bypass (CABG) surgery is successfully managed with normothermic cardiopulmonary bypass (CPB) using warm blood cardioplegia. The lack of the protective effect of hypothermia, however, might make the central nervous system vulnerable. METHODS: Thirty-six patients were randomized into normothermic CPB (36-37 degrees C) (NTCPB group, n=18) and hypothermic CPB (28 degrees C) (HTCPB group, n=18) in order to examine whether normothermic or hypothermic CPB induces the release of the intracellular brain enzymes, creatine kinase (CK), its brain-specific isoenzyme (CK-BB), and neuron-specific enolase (NSE) into cerebrospinal fluid (CSF). In addition, clinical neurologic examination and neuropsychologic assessment were done preoperatively, 5 d and 11-23 mo postoperatively. RESULTS: One patient in each group suffered a stroke after surgery. Two patients in the normothermic group had minor neurologic complications. The cognitive decline after operation was similar in the NTCPB and HTCPB groups. CSF enzymes from normothermic and hypothermic CABG patients without gross neurologic complications were not significantly higher than CSF enzymes from orthopaedic reference patients. CABG patients with neurologic complications had higher enzyme concentrations. Cognitive decline after the operation correlated statistically significantly with CSF enzyme concentrations in the NTCPB group, but not in the HTCPB group. CONCLUSION: CABG operation without major neurologic complication does not induce the release of CK, CK-BB or NSE enzymes into CSF, irrespective of whether the CPB is normothermic or hypothermic.

Brain↗

PubMed2000

Esmolol cardioplegia in unstable coronary revascularisation patients. A randomised clinical trial.

BACKGROUND: Esmolol has been studied and applied to control hypertension and tachycardia during open heart surgery. Esmolol has been used on a minor scale as a single cardioplegic agent. Little information is available on esmolol as a component of blood cardioplegia. In this prospective, randomised, double-blind clinical study we investigated whether esmolol improves cardioprotection in patients scheduled for an urgent coronary operation. METHODS: Forty patients with unstable angina were operated using cold blood cardioplegia as the basic cardioprotective method. Cardioplegia was infused intermittently, and esmolol was given into the cardioplegia line (15 mg/min) during cold infusions. Patients with ongoing myocardial infarction were excluded. RESULTS: The arrest time during the cardioplegic induction or the rate of spontaneous resumption of the heart rhythm did not differ significantly between the groups. The serial measurements of plasma creatine kinase MB-fraction activity (P=0.27), serum creatine kinase MB-fraction mass assay (P=0.16), troponin I (P=0.41) and myoglobin (P=0.14) similarly did not differ between the groups, nor did myocardial lactate extraction (P= 0.12). CONCLUSION: Esmolol addition to blood cardioplegia did not increase the efficacy of cardioprotection in the present study setting in unstable patients during urgent coronary revascularisation.

Adrenergic beta-Antagonists↗

PubMed2000

Comparison of bioimpedance and radioisotope methods in the estimation of extracellular water volume before and after coronary artery bypass grafting operation.

To estimate extracellular water volume (ECW) changes in connection with coronary artery bypass grafting operation, simultaneous ECW estimations by 51Cr-EDTA dilution and whole-body bioimpedance techniques were performed in 15 patients. The assessments of ECW were compared with patients' weighing results. Whole-body bioimpedance-derived ECW correlated significantly with 51Cr-EDTA dilution-based ECW in the pre-operative period (r=0.74; P<0.005); the bias was 0.2 +/- 1.1 l (+/-SD). In the post-operative period, the agreement between these methods was poor, the bias being 0.5 +/- 2.5 l, and no significant correlation between the methods was found (r=0.38; P>0.05). Whole-body bioimpedance-derived ECW changes correlated significantly with weight changes of the patient induced by the operation (r=0.52; P<0.05). 51Cr-EDTA dilution-based ECW changes correlated neither with weight changes (r=0.33; P>0.05) nor with bioimpedance-derived ECW changes (r=0.03; P>0.05). Alterations in radioisotope tracer distribution and loss of it due to blood leakage in the post-operative period were presumed to explain the discrepancy between dilution technique and weighing results. The results suggest that bioimpedance is a useful non-invasive method for assessment of extracellular volume changes induced by coronary artery bypass grafting operations. 51Cr-EDTA dilution-based ECW determination is not suitable in related conditions.

Aged↗

PubMed2000

Allopurinol does not increase free radical scavenging capacity during reperfusion in coronary artery bypass graft patients.

OBJECTIVES: Allopurinol protects the heart against ischaemic events during coronary artery bypass grafting (CABG), possibly because of its antioxidant properties. This double-blind study was designed to investigate whether allopurinol (1 g), given before cardiopulmonary bypass and prior to the opening of cross-clamping, has an antioxidant effect in CABG patients by measuring plasma total peroxyl radical scavenging capacity. DESIGN: Twenty-seven patients with stabile angina were randomized into allopurinol (n = 14) or placebo (n = 13) groups. RESULTS: During 10 min reperfusion, plasma hypoxanthine and xanthine concentrations increased only in the allopurinol group, whereas uric acid concentrations decreased. Total peroxyl radical scavenging capacity (TRAP) decreased from the initial value at all measuring points in both groups. CONCLUSIONS: The reducing effect of allopurinol on free radical generation cannot be seen in TRAP values, obviously because the uric acid concentration of plasma decreases markedly. The positive clinical effects of allopurinol in CABG patients may arise from its direct oxygen free radical scavenging function.

Aged↗

PubMed2000

Effect of allopurinol on myocardial oxygen free radical production in coronary bypass surgery.

OBJECTIVES: Allopurinol protects the heart from reperfusion injury. The aim of this study was to investigate myocardial free radical production during reperfusion with and without allopurinol treatment in coronary artery bypass grafting patients randomized into allopurinol (n = 14) or placebo (n = 13) groups. DESIGN: Allopurinol (1 g) was given blind prior to cardiopulmonary bypass and prior to opening the aorta. Oxygen free radicals were measured before anesthesia in arterial blood, before cross-clamping and 1 and 10 min after reperfusion in arterial and coronary sinus blood. Levels were measured as relative concentrations by the electron spin resonance method. RESULTS: One minute after reperfusion the level of spin-trapped radicals in arterial blood was elevated significantly (p = 0.016) in the allopurinol group, from 7.7 (SE: 0.8) to 8.6 (1.4) and non-significantly (p = 0.074) in the placebo group, from 7.3 (0.7) to 8.3 (0.8). Ten minutes after reperfusion the arterial values were 8.6 (1.5) in the allopurinol and 7.6 (0.7) in the placebo group, the sinus values being 7.6 (1.3) and 8.3 (0.8), respectively. Myocardial free radical production was -0.94 (1.21) in the allopurinol and +0.79 (0.96) in the placebo group after 10 min reperfusion, the difference being significant (p = 0.043). CONCLUSIONS: All patients in both groups had an increasing tendency to free radical production during early reperfusion. Patients treated with allopurinol showed less myocardial production of free radicals, indicating that its protective effect may be due to its antioxidative properties.

Aged↗

PubMed2000

Protective effect of unstable angina in coronary artery bypass surgery.

OBJECTIVE: To test the hypothesis that recent ischaemic episodes in unstable cases have a protective effect on coronary artery bypass graft (CABG) patients. MATERIALS AND METHODS: Twenty unstable patients with ischaemic episodes within 3 days before operation were compared with 20 stable patients. Haemodynamic data were monitored up to the first postoperative day. Biochemical markers were measured up to the second postoperative day. RESULTS: The cardiac index decreased at 1 and 6 h after declamping in the stable group (89% and 97% of baseline) but increased in unstable patients (104% and 122%, p =0.038 and 0.036, respectively). The depression in the right ventricular stroke work index was significantly attenuated in the unstable group (58%, 67% and 83% in stable and 90%, 97% and 117% in unstable patients, p = 0.027, 0.010 and 0.049 at 1 and 6 h after declamping and 1st POD). The release of cardiac troponin I (CTnI) and CK-MB was significantly lower in the unstable group at 6 h after declamping (5.6 +/- 2.9 and 19.0 +/- 6.3 microg/l in unstable vs 17.4 +/- 9.6 and 25.8 +/- 12.3 microg/l in stable patients, p = 0.000 and 0.039, respectively). CONCLUSION: Recent unstable angina before CABG might act as an ischaemic preconditioning stimulus and could improve haemodynamic function and cellular viability. Delayed preconditioning most likely causes this protective effect.

Aged↗

PubMed2000

Ischaemic preconditioning has a beneficial effect on left ventricular haemodynamic function after a coronary artery biopass grafting operation.

OBJECTIVE: Ischaemic preconditioning (IP) is the most effective procedure for endogenous myocardial protection. However, studies on the effects of IP in cardiac surgery are rare and controversial. The present aim was to investigate whether IP improves the haemodynamic recovery of CABG patients. DESIGN: The study included 40 stable CABG patients with 3-vessel disease, randomized into an IP group (n = 20) and a control group (n = 20). In the IP group two cycles of 2-min ischaemia following 3-min reperfusion before cross-clamping were induced. The haemodynamics of the patients were followed-up to the first postoperative morning. RESULTS: The cardiac index decreased at 1 and 6 h after surgery in the control group but increased in the IP group (-0.33 vs 0.09 l/min/m2, p = 0.02 and -0.15 vs 0.57 l/min/m2, p = 0.001, respectively). Depressions in the left ventricular stroke work index and the right ventricular stroke work index at 6 h after surgery were more severe in controls and were statistically significant (p = 0.049 and 0.007, respectively). Less inotropic support was used in the IP group. There were no differences in serum CK-MB, cardiac troponin I, myoglobin or lactate values between the two groups. CONCLUSION: IP has a beneficial effect on left ventricular haemodynamic recovery after a CABG operation.

Aged↗

PubMed2000

The comparison of hypertonic saline (7.5%) and normal saline (0.9%) for initial fluid administration before spinal anesthesia.

Hypertonic saline can be used for initial fluid administration before spinal anesthesia. It is effective in small-volume fluid resuscitation. This randomized double-blinded study compared the effects of 7.5% hypertonic saline (HS) and 0.9% normal saline (NS) in doses containing 2 mmol/kg of sodium in 40 ASA physical status I-II patients undergoing arthroscopy or other lower limb surgery under spinal anesthesia. We infused 1.6 mL/kg of HS or 13 mL/kg of NS for initial fluid administration before spinal anesthesia induced with a 10-mg dose of 0.5% hyperbaric bupivacaine. Etilefrine was administered to maintain mean arterial pressure at > or =80% of its control value. Systolic and diastolic blood pressure, heart rate, and cardiac index did not differ between the groups, and the amount of etilefrine administered was similar in the treatment groups. In all our patients, the plasma sodium concentrations were within the normal range after surgery and serum osmolality was within the normal range after spinal anesthesia. The time and the volume of the first micturition were similar in both groups, despite the much smaller amount of infused free water in the HS group. We conclude that 7.5% HS was as good as NS for the initial fluid administration before spinal anesthesia when the amount of sodium was kept unchanged.

Adolescent↗

PubMed1999

Reg1ulatory role and molecular interactions of a cell-surface heparan sulfate proteoglycan (N-syndecan) in hippocampal long-term potentiation.

The cellular mechanisms responsible for synaptic plasticity involve interactions between neurons and the extracellular matrix. Heparan sulfates (HSs) constitute a group of glycosaminoglycans that accumulate in the beta-amyloid deposits in Alzheimer's disease and influence the development of neuron-target contacts by interacting with other cell surface and matrix molecules. However, the contribution of HSs to brain function is unknown. We found that HSs play a crucial role in long-term potentiation (LTP), a finding that is consistent with the idea that converging molecular mechanisms are used in the development of neuron-target contacts and in activity-induced synaptic plasticity in adults. Enzymatic cleavage of HS by heparitinase as well as addition of soluble heparin-type carbohydrates prevented expression of LTP in response to 100 Hz/1 sec stimulation of Schaffer collaterals in rat hippocampal slices. A prominent carrier protein for the type of glycans implicated in LTP regulation in the adult hippocampus was identified as N-syndecan (syndecan-3), a transmembrane proteoglycan that was expressed at the processes of the CA1 pyramidal neurons in an activity-dependent manner. Addition of soluble N-syndecan into the CA1 dendritic area prevented tetanus-induced LTP. A major substrate of src-type kinases, cortactin (p80/85), and the tyrosine kinase fyn copurified with N-syndecan from hippocampus. Moreover, association of both cortactin and fyn to N-syndecan was rapidly increased after induction of LTP. N-syndecan may thus act as an important regulator in the activity-dependent modulation of neuronal connectivity by transmitting signals between extracellular heparin-binding factors and the fyn signaling pathway.

Animals↗

PubMed1999

Cardiac output can be reliably measured noninvasively after coronary artery bypass grafting operation.

OBJECTIVE: To evaluate the reliability of whole-body impedance cardiography in the measurement of cardiac output after coronary artery bypass grafting operation in comparison with the thermodilution method. DESIGN: Prospective, consecutive sampling. PATIENTS: A total of 82 patients undergoing coronary artery bypass surgery were investigated. In a group of 41 patients who were intubated, cardiac output measurements were taken simultaneously with whole-body impedance cardiography and the thermodilution method within the first 3 hrs after the operation (early intensive care unit [ICU] period). In another group of 41 patients, the measurements were taken before the operation and in the second 12 hrs after cardiac surgery (late ICU period). INTERVENTIONS: None. MEASUREMENTS AND MAIN RESULTS: The agreement between the thermodilution and whole-body impedance cardiography cardiac output measurements was good before the operation, bias 0.04 +/- 1.64 L/min (n = 41), and in the late ICU period, bias 0.00 +/- 1.84 L/min (+/-2 SD) (n = 41). The results were within 20% in 81%-85% of the cases. The agreement was satisfactory in the early ICU period, bias 0.38 +/- 2.74 L/min (n = 41). It was presumed that thermal instability of the patients was one possible source of measurement errors in the thermodilution method, causing reduced agreement between the methods in this period. The repeatability values (rv = 2.83 x SDs) for whole-body impedance cardiography were 0.44 L/min before the operation, 0.30 L/min in the early ICU period, and 0.65 L/min in the late ICU period, being significantly better than for the thermodilution method (0.79, 0.51, and 1.11 L/min, respectively) in all phases of the investigation (p < .001). The agreement between the thermodilution method and whole-body impedance cardiography is similar to reported comparisons between invasive methods in analogous settings. CONCLUSIONS: Whole-body impedance cardiography reliably measures cardiac output in patients after coronary artery bypass grafting operation. The excellent repeatability of whole-body impedance cardiography enhances the value of the method in continuous monitoring of patients after the operation.

Aged↗

PubMed1999

Amrinone, a phosphodiesterase III inhibitor, and arachidonic acid metabolism in humans.

Amrinone-a phosphodiesterase III inhibitor-is used in the treatment of acute heart failure. In addition to its hemodynamic effects, amrinone has been shown to inhibit thromboxane synthesis in vitro. We investigated the effects of amrinone on thromboxane, prostaglandin, and leukotriene synthesis in humans. Eight healthy male volunteers took part in this single-blind study in which either amrinone (a 1.5-mg/kg bolus in 30 min and after that 10 microg/kg/min for 1 h 30 min) or placebo (0.9% NaCl) were infused. Amrinone infusion increased systolic blood pressure but had no significant effect on diastolic blood pressure or heart rate. Amrinone did not modulate thromboxane B2 synthesis stimulated by either spontaneous clotting or calcium-ionophore A23187 in whole blood. Amrinone had no effects on prostaglandin E2 or leukotriene E4 production in A23187-stimulated whole blood, nor did it affect urinary excretion of 11-dehydrothromboxane B2 or 2,3-dinor-6-keto-prostaglandin F1alpha, the index metabolites of thromboxane A2 and prostacyclin productions, respectively. We conclude that amrinone has no effects on eicosanoid production in humans at the dose level used in this study, and that the hemodynamic effects noticed are not mediated via cyclooxygenase or lipoxygenase products of arachidonic acid metabolism.

Adult↗

PubMed1998

Dopexamine unloads the impaired right ventricle better than iloprost, a prostacyclin analog, after coronary artery surgery.

OBJECTIVE: To evaluate the ventricle-unloading properties of dopexamine and iloprost and to compare their effects on right ventricular (RV) function and oxygen transport in patients with low RV ejection fraction (RVEF) after cardiac surgery. DESIGN: A prospective, randomized, double-blind, cross-over, clinical study. SETTING: University hospital. PARTICIPANTS: Twenty patients with proximal total stenosis of the right coronary artery studied immediately after coronary artery surgery. INTERVENTIONS: Treatment drugs were administered in a random order in doses equipotent with respect to cardiac output response. Infusion rates were increased stepwise to induce a 25% increase in cardiac index. A washout period of 60 minutes was allowed between treatments. MEASUREMENTS AND MAIN RESULTS: Central hemodynamics, RV function assessed by the EF (fast-response thermodilution), end-systolic and end-diastolic volumes, and systemic oxygenation were measured before and after the first drug, after the washout period, and after the second drug. Central filling pressures remained constant during treatments. Both drugs decreased pulmonary vascular resistance index, but iloprost was more effective (p < 0.05). Iloprost decreased mean arterial and pulmonary artery pressure, which were unaffected by dopexamine. Dopexamine increased EF significantly more than iloprost (p < 0.001). End-systolic volume index decreased subsequent to dopexamine only (p < 0.001). Iloprost increased intrapulmonary shunt more than dopexamine (p < 0.001). Changes in oxygen delivery, consumption, and extraction were similar. CONCLUSION: The findings suggest that dopexamine is more effective than iloprost for support and unloading of the postoperatively disturbed RV in terms of RVEF and end-systolic volume. The reduction of pulmonary vascular resistance after administration of iloprost without a decrease in end-systolic volume might not be considered a reduction of RV afterload. Iloprost increases the pulmonary shunt fraction, however, more than dopexamine, indicating a more prominent vasodilator effect.

Cardiac Output↗

PubMed1998

Clonidine does not attenuate median nerve somatosensory evoked potentials during isoflurane anesthesia.

BACKGROUND: Clonidine, an alpha2 agonist, reduces the requirements of several anesthetics. However, the effects of clonidine on somatosensory evoked potentials (SEPs) are unclear. These effects on cortical SEPs during isoflurane anesthesia were studied in 20 ASA I-II patients scheduled for elective surgery. Furthermore, the isoflurane concentration required to induce electroencephalogram (EEG) burst-suppression with and without clonidine was studied. METHODS. Anesthesia was maintained with isoflurane at a FiO2 of 0.4. At 1 MAC isoflurane the patients were randomly given either intravenous clonidine 2 microg kg(-1) (ten patients) or saline (ten patients). Finally, the isoflurane concentration was increased to a point at which a burst-suppression pattern appeared in the EEG. SEPs upon median nerve stimulation were recorded (1) before induction of anesthesia, (2) at 1 MAC before clonidine/saline, (3) at 1 MAC after clonidine/saline, (4) at EEG burst-suppression. RESULTS: The cortical SEP amplitude was attenuated from 3.7 (2.0) microV to 2.1 (1.3) microV (p < 0.001) and the peak latency increased from 19.3 (1.1) ms to 22.0 (1.3) ms (p < 0.0001) during 1 MAC isoflurane anesthesia, but the addition of clonidine did not further increase these changes. The isoflurane end-tidal concentration needed to induce burst-suppression EEG was not significantly different in the clonidine group compared with the placebo group (2.0% vs. 2.1%, p = 0.07). CONCLUSIONS: The effect of clonidine in reducing the requirements of anesthetics during general anesthesia is not seen in the cortical SEPs. The isoflurane-induced burst-suppression in the EEG was not affected by clonidine, suggesting that the EEG effects of clonidine and isoflurane were not additive. If SEPs are monitored intraoperatively, clonidine can be used as an adjuvant during isoflurane anesthesia without harmful effects on SEP monitoring.

Adrenergic alpha-Agonists↗