Seppo Kaukinen

Whole-body impedance cardiography in the measurement of cardiac output

OBJECTIVE To evaluate the reliability of whole-body impedance cardiography with electrodes on wrists and ankles in the measurement of cardiac output compared with the thermodilution method. DESIGN Prospective, clinical investigation. SETTING Surgical intensive care unit and operating room at a university hospital. PATIENTS Simultaneous cardiac output measurements by thermodilution and whole-body impedance cardiography were performed in 74 patients undergoing a coronary artery bypass grafting operation. INTERVENTIONS None. MEASUREMENTS AND MAIN RESULTS A total of 97 triplicate, simultaneous cardiac output measurements were carried out with thermodilution and whole-body impedance cardiography: 74 measurements were conducted in patients who were awake and 23 measurements were conducted during anesthesia but before the commencement of surgery. The mean cardiac output difference (bias) between the two methods was 0.25 +/- 0.81 (SD) L/min; the limits of agreement (2 SD) were-1.37 and 1.87 L/min, respectively. The repeatability value (rv = 2.83 x SD) for whole-body impedance cardiography (rv = 0.46 L/min) was considerably better than for the thermodilution method (rv = 1.05 L/min). Whole-body impedance cardiography reliably detected cardiac output changes induced by head-up tilt before anesthesia, by anesthesia induction, and by intubation. Two factors predicted the between-methods stroke volume difference: hematocrit (correlation coefficient r = -.36, r2 = .13; p < .001); and body mass index (r = .29, r2 = .08; p < .01). Using the multiple linear regression equation for correcting the stroke volume by hematocrit and body mass index, the limits of agreement (2 SD) between the methods studied were reduced to +/-1.28 L/min for cardiac output and +/-0.72 L/min/m2 for cardiac index. CONCLUSIONS There was close agreement between whole-body impedance cardiography and thermodilution in the measurement of cardiac output in patients with coronary artery disease without cardiac shunts and valvular lesions. The repeatability of the impedance method was significantly better than the repeatability of thermodilution. Whole-body impedance cardiography can be recommended for the assessment of cardiac output and its changes in the resting state. Whole-body impedance cardiography is a feasible and handy method for noninvasive and continuous measurement of cardiac output.

Non-invasive measurement of cardiac output: whole-body impedance cardiography in simultaneous comparison with thermodilution and direct oxygen Fick methods

ObjectiveTo determine the reliability of whole-body impedance cardiography (ICGWB), with electrodes attached to wrists and ankles, in the measurement of cardiac output (CO) on the basis of simultaneous comparison with thermodilution (TD) and direct oxygen Fick (Fick) methods.DesignProspective clinical study.SettingA surgical intensive care unit at a university hospital.PatientsThirty consecutive subjects undergoing a coronary artery bypass surgery were investigated preoperatively.MeasurementsICGWB derived CO was measured simultaneously with the TD and Fick methods to establish the biases and limits of agreement (LA) between the methods.ResultsThe results obtained by ICGWB and the invasive methods showed good agreement. The bias and LA between COTD and COICG were 0.001/min; −1.37 and 1.37 1/min, respectively, and were close to those obtained between COTD and COFICK, 0.321/min; 1.74 and −1.101/ min. The bias and LA between the COFICK and COICG were −0.32 1/min; −2.24 and 1.60 1/min respectively. The repeatability value of consecutive single measurements for ICGWB (RVICG=0.571/min) was much better than for the TD method (RVTD=1.10 1/min).ConclusionThere was close agreement between the results of the three methods in the measurement of CO. In sedated preoperative patients the accuracy of ICGWB is within clinically acceptable limits and its repeatability is excellent. ICGWB provides a useful alternative to the TD and Fick methods in cases where the pressures supplied by the pulmonary artery catheter are not essential.

Hemodynamic effects of iloprost, a prostacyclin analog

Iloprost is a chemically stable derivative of carbaprostacyclin. We studied its hemodynamic effects in 10 patients in an intensive care unit. Iloprost was infused intravenously for 3 days for the treatment of advanced obliterative arterial disease of the lower extremities. Clinically significant hemodynamic responses were obtained with an infusion rate of 0.5 ng/kg/min. All subjects tolerated the dose of 4 ng/kg/min, which increased heart rate an average of 11% and cardiac index an average of 26%. This infusion rate decreased mean arterial pressure by 15%, total peripheral resistance by 31%, and pulmonary vascular resistance by 34%. Mean pulmonary arterial pressure, pulmonary capillary wedge pressure, left and right ventricular stroke work indices, and rate pressure product did not change. At higher doses of up to 8 ng/kg/min, responses were augmented only slightly, but side effects such as headache, nausea, and abdominal colics became more prominent. The data show iloprost to be a potent vasodilator that reduces both pre‐ and afterload and presumably induces a compensatory increase in cardiac output and heart rate, but does not increase the work load or oxygen demand of the heart.

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.

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.

Hemodynamic and hormonal changes in patients pretreated with captopril for surgery of the abdominal aorta

Cardiovascular and hormonal responses to aortic cross-clamping (ACC) and declamping (ADC) were studied in 20 patients undergoing reconstructive aortic surgery anesthetized with fentanyl and droperidol. Ten of the patients served as a control group, and 10 patients were treated with oral captopril (25 mg the day before operation and 25 mg one hour before anesthesia) to prevent intraoperative and postoperative hypertension. After the induction of anesthesia in the captopril group, hypotension was seen in four patients and bradycardia in three patients. In both groups, the most important changes in hemodynamics after the ACC were an increase in systemic vascular resistance and decreases in cardiac and stroke index. After the ADC, the cardiac index (CI) improved nearly to the level before the ACC. The urine output during anesthesia was 46 +/- 5 mL/h in the control group and 73 +/- 11 mL/h (P less than 0.05) in the captopril group. Postoperatively, patients in both groups were hypertensive and tachycardic. In the control group, plasma renin activity rose significantly during the ACC, indicating activation of the renin-angiotensin system (RAS). In both groups, significant increases in plasma vasopressin (PAVP), epinephrine, and norepinephrine were also observed before the ACC and during the postoperative period. The results suggest that oral captopril increases the risk of hypotension and bradycardia after induction of anesthesia, and does not prevent postoperative hypertension.

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.

Median nerve somatosensory evoked potentials during isoflurane anaesthesia

PurposeThe effect of isoflurane on the subcortical P14 component of the median nerve somatosensory evoked potential (SEP) is poorly known. We studied whether the P14 wave from the upper brainstem, recorded with a nasopharyngeal electrode, was attenuated at the isoflurane-induced EEG burst-suppression level. We also compared the effect of isoflurane on the P14, cervical N13 and cortical N20, N35 and N60 components.MethodsSeventeen elective patients were anaesthetized with isoflurane. Somatosensory evoked potentials were recorded pnor to anaesthesia, at 0.5 MAC and I MAC end-tidal isoflurane as well as at the level when EEG was in burst-suppression (mean 1.9 vol% end-tidal isoflurane).ResultsIsoflurane had varying effects on the subcortical components of median SEP. The amplitude of nasopharyngeal P14 was stable, but the mean latency increased from 14.4 ± 1.2 msec at 0.5 MAC to 15.2 ± 1.1 msec at burstsuppression level (P < 0.05). In contrast, the N13 neck response amplitude was attenuated from 3.3 ± 0,6 μV to 2.6 ±0.5μV (P < 0.005) without latency changes. The latency of the cortical N20 wave was increased from 19.7 ± 1.1 msec at awake to 24.4 ± 1.6 msec at burst-suppression level (P < 0.0001) and amplitude was reduced from 3.3 ± 1.1 μV to 1.3 ± 0.6 μV (P < 0.0001). The later cortical components were attenuated even during 0.5 MAC isoflurane and were not recordable during EEG burst-suppression.ConclusionWe conclude that P14 can reliably be recorded with nasopharyngeal electrodes during isoflurane anaesthesia, even during EEG burst-suppression, when the N20 wave is attenuated. In contrast, the middle-latency SEP components are sensitive to isoflurane anaesthesia.RésuméObjectifNous connaissons mal l’action de l’isoflurane sur la composante sous-corticale P14 du potentiel somatosensoriel évoqué (SEP) du nerf médian. Nous avons cherché si l’onde P14 enregistrée à la partie supérieure du tronc cérébral avec une électrode nasopharyngée diminuait lorsque l’isoflurane ralentissait l’ÉEG jusqu’au niveauburst-suppression. Nous avons aussi comparé l’influence de l’isoflurane sur les composantes P14, cervicale N13 et cortkales N20, N25 et N60.MethodesDix-sept patients électifs ont été anesthésiés à l’isoflurane. Les potentiels évoqués somatosensorielsont été enregistrés avant l’anesthésie, à 0,5 MAC et à 1,0 MAC télé-expiratoires et au niveau deburst-suppression ÉEG (concentration télé-expiratoire 1,9% d’isoflurane).RésultatsL’isoflurane avait des effets variés sur les composantes non-corticales des SEP médians, L’amplitude du P14 nasopharyngé était stable, mais la latence moyenne augmentait de 14,4 ± 1,2 ms à 0.5 MAC à 15 ± 1,1 ms pendant leburst-suppression (P < 0,05). Par contre, l’amplitude de la réponse N13 cervicale était atténuée de 3,3 ± 0,6 μV à 2,6 ± 0,5 μV (P < 0,005) avec une latence inchangée. La latence de l’onde corticale N20 augmentait de 19,7 ± 1,1 ms a l’etat vigile à 24,4 ± 1,6 ms pendant leburst-suppression (P < 0,0001). Les demières composantes corticales diminuaient même sous isoflurane 0,5 MAC et n’étaient pas enregistrables pendant leburst-suppression à l’ÉEG.ConclusionNous concluons qu’il est possible d’enregistrer P14 fidèlement avec des électrode nasopharyngées pendant l’anesthésie à l’isoflurane, meme pendant leburst-suppression lorsque l’onde N20 est atténuée. Par contre, les composantes SEP de latence moyenne sont sensibles à l’anesthésie à l’isoflurane.

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.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 6.3mg/l in unstable vs 17.4 9.6 and 25.8 12.3mg/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.

Cytokine responses in patients undergoing coronary artery bypass surgery after ischemic preconditioning.

OBJECTIVE The release of proinflammatory cytokines has been shown to be associated with the development of complications after coronary artery bypass grafting with cardiopulmonary bypass. The purpose of the present study was to establish whether ischemic preconditioning (IP) could limit inflammatory cytokines release in patients undergoing elective coronary artery bypass surgery. METHODS Twenty-two patients with multiple-vessel coronary artery disease and stable angina admitted for first-time elective coronary artery bypass surgery were randomized into control or ischemic preconditioning groups. Patients in the IP group were exposed to two cycles of two-minute myocardial ischemia, followed by three minutes of reperfusion, at the beginning of the revascularization operation, before the cross-clamping and ischemic period used for coronary artery bypass graft anastomosis. Peripheral plasma levels of TNF-alpha, IL-6, IL-8 and IL-10 were measured perioperatively. RESULTS Significant elevation of IL-6, IL-8 and IL-10 were observed in both groups after reperfusion. Ischemic preconditioning has no effect on cytokine release in the early stage after reperfusion. Arterial blood IL-6 levels in the preconditioning group were significantly lower than in controls at 20 h after declamping (52.93 +/- 9.79 vs 96.04 +/- 17.56 pg/ml, p < 0.05). CONCLUSIONS The results indicate that ischemic preconditioning results in no effect on systemic inflammatory cytokine release in the early stage but a delayed reduction in IL-6 levels at 20 h after reperfusion.Objective - The release of proinflammatory cytokines has been shown to be associated with the development of complications after coronary artery bypass grafting with cardiopulmonary bypass. The purpose of the present study was to establish whether ischemic preconditioning (IP) could limit inflammatory cytokines release in patients undergoing elective coronary artery bypass surgery. Methods