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Objective: If bilateral thyroid surgery is planned and staged thyroidectomy considered in case of loss of neuromonitoring signal (LOS), a waiting time of 20 minutes is suggested for evaluation of early nerve recovery. This recommendation is based on clinical observations and has not been thoroughly validated experimentally., Methods: Sixteen pigs were randomly studied, and electromyogram (EMG) was continuously recorded during traction injury until an amplitude decrease of 70% from baseline (BL) (16 nerves) or LOS (16 nerves), and further during 40-minute recovery time. At the end of the experiments, vocal cord twitch was evaluated by video-laryngoscopy., Results: In the 70% group, 8 of 16 nerves recovered to or above an amplitude of 50% of baseline after 20 minutes and finally one more after 40 minutes. In the LOS group, only one nerve showed recovery after 20 minutes and one more after 40 minutes. Video-laryngoscopy revealed good or strong vocal cord twitches, in 10 of 14 nerves in the 70% group and in only 2 of 14 nerves in the LOS group., Conclusions: The overall intraoperative recovery was low after LOS. Even after 70% amplitude depression, only half of the nerves showed recovery to amplitudes ≥50% of BL. Nerve recovery is dynamic, and a waiting time of 20 minutes seems appropriate for the identification of early nerve recovery before decisions are taken to continue or terminate surgery. The final EMG amplitude was not always well correlated with estimated vocal cord twitch, evaluated by video-laryngoscopy. This observation needs further investigation., Competing Interests: The authors declare no potential conflict of interest., (© 2020 The Authors. Laryngoscope Investigative Otolaryngology published by Wiley Periodicals LLC on behalf of The Triological Society.)

Objectives: Potassium-based depolarizing St Thomas' Hospital cardioplegic solution No 2 administered as intermittent, oxygenated blood is considered as a gold standard for myocardial protection during cardiac surgery. However, the alternative concept of polarizing arrest may have beneficial protective effects. We hypothesize that polarized arrest with esmolol/adenosine/magnesium (St Thomas' Hospital Polarizing cardioplegic solution) in cold, intermittent oxygenated blood offers comparable myocardial protection in a clinically relevant animal model., Methods: Twenty anaesthetized young pigs, 42 ± 2 (standard deviation) kg on standardized tepid cardiopulmonary bypass (CPB) were randomized (10 per group) to depolarizing or polarizing cardiac arrest for 60 min with cardioplegia administered in the aortic root every 20 min as freshly mixed cold, intermittent, oxygenated blood. Global and local baseline and postoperative cardiac function 60, 120 and 180 min after myocardial reperfusion was evaluated with pressure-conductance catheter and strain by Tissue Doppler Imaging. Regional tissue blood flow, cleaved caspase-3 activity, GRK2 phosphorylation and mitochondrial function and ultrastructure were evaluated in myocardial tissue samples., Results: Left ventricular function and general haemodynamics did not differ between groups before CPB. Cardiac asystole was obtained and maintained during aortic cross-clamping. Compared with baseline, heart rate was increased and left ventricular end-systolic and end-diastolic pressures decreased in both groups after weaning. Cardiac index, systolic pressure and radial peak systolic strain did not differ between groups. Contractility, evaluated as dP/dtmax, gradually increased from 120 to 180 min after declamping in animals with polarizing cardioplegia and was significantly higher, 1871 ± 160 (standard error) mmHg/s, compared with standard potassium-based cardioplegic arrest, 1351 ± 70 mmHg/s, after 180 min of reperfusion (P = 0.008). Radial peak ejection strain rate increased and the load-independent variable preload recruitable stroke work was increased with polarizing cardioplegia after 180 min, 64 ± 3 vs 54 ± 2 mmHg (P = 0.018), indicating better preserved left ventricular contractility with polarizing cardioplegia. Phosphorylation of GRK2 in myocardial tissue did not differ between groups. Fractional cytoplasmic volume in myocytes was reduced in hearts arrested with polarizing cardioplegia, indicating reduction of cytoplasmic oedema., Conclusions: Polarizing oxygenated blood cardioplegia with esmolol/adenosine/magnesium offers comparable myocardial protection and improves contractility compared with the standard potassium-based depolarizing blood cardioplegia., (© The Author 2016. Published by Oxford University Press on behalf of the European Association for Cardio-Thoracic Surgery.)

Noninvasive measurements of myocardial strain and strain rate by speckle tracking echocardiography correlate to cardiac contractile state but also to load, which may weaken their value as indices of inotropy. In a porcine model, we investigated the influence of acute dynamic preload reductions on left ventricular strain and strain rate and their relation to the pressure-conductance catheter-derived preload recruitable stroke work (PRSW) and peak positive first derivative of left ventricular pressure (LV-dP/dtmax). Speckle tracking strain and strain rate in the longitudinal, circumferential, and radial directions were measured during acute dynamic reductions of end-diastolic volume during three different myocardial inotropic states. Both strain and strain rate were sensitive to unloading of the left ventricle (P < 0.001), but the load dependency for strain rate was modest compared with strain. Changes in longitudinal and circumferential strain correlated more strongly to changes in end-diastolic volume (r = -0.86 and r = -0.72) than did radial strain (r = 0.35). Longitudinal, circumferential, and radial strain significantly correlated with LV-dP/dtmax (r = -0.53, r = -0.46, and r = 0.86), whereas only radial strain correlated with PRSW (r = 0.55). Strain rate in the longitudinal, circumferential and radial direction significantly correlated with both PRSW (r = -0.64, r = -0.58, and r = 0.74) and LV-dP/dtmax (r = -0.95, r = -0.70, and r = 0.85). In conclusion, the speckle tracking echocardiography-derived strain rate is more robust to dynamic ventricular unloading than strain. Longitudinal and circumferential strain could not predict load-independent contractility. Strain rates, and especially in the radial direction, are good predictors of preload-independent inotropic markers derived from conductance catheter., (Copyright © 2016 the American Physiological Society.)

Background: Speckle Tracking Echocardiography (STE) strain analysis relies on both spatial and temporal smoothing. The user is often allowed to adjust these smoothing parameters during analysis. This experimental study investigates how different degrees of user controllable spatial and temporal smoothing affect global and regional STE strain values in recordings obtained from normal and ischemic myocardium., Methods: In seven anesthetized pigs, left ventricular short- and long-axis B-mode cineloops were recorded before and after left anterior descending coronary artery occlusion. Peak- and postsystolic global STE strain in the radial, circumferential and longitudinal direction as well as corresponding regional strain in the anterior and posterior walls were measured. During post-processing, strain values were obtained with three different degrees of both spatial and temporal smoothing (minimum, factory default and maximum), resulting in nine different combinations., Results: All parameters for global and regional longitudinal strain were unaffected by adjustments of spatial and temporal smoothing in both normal and ischemic myocardium. Radial and circumferential strain depended on smoothing to a variable extent, radial strain being most affected. However, in both directions the different combinations of smoothing did only result in relatively small changes in the strain values. Overall, the maximal strain difference was found in normal myocardium for peak systolic radial strain of the posterior wall where strain was 22.0 ± 2.2% with minimal spatial and maximal temporal smoothing and 30.9 ± 2.6% with maximal spatial and minimal temporal smoothing (P < 0.05)., Conclusions: Longitudinal strain was unaffected by different degrees of user controlled smoothing. Radial and circumferential strain depended on the degree of smoothing. However, in most cases these changes were small and would not lead to altered conclusions in a clinical setting. Furthermore, smoothing did not affect strain variance. For all strain parameters, variance remained within the corresponding interobserver variance.

Aims: The aim of this study was to investigate whether multi-layer radial strain and strain rate analysis is superior to one-layer strain analysis for confirming reperfusion following a non-occlusive coronary stenosis., Methods and Results: In 10 anaesthetized pigs, an extracorporeal shunt was inserted from the brachiocephalic to the left anterior descending coronary artery. Microspheres were injected and left ventricular (LV) short- and long-axis echocardiographic views were recorded with the open shunt, during the 120 min of severe stenosis and 20 min (early) and 100 min (late) after reperfusion. The anterior wall was analysed for radial one-layer and three-layer tissue Doppler imaging (TDI) strain and strain rate, in addition to radial, circumferential, and longitudinal speckle-tracking echocardiography (STE) strain. During stenosis, perfusion was reduced in the two inner wall layers (P< 0.01). All peak systolic strain and strain rate parameters were reduced, whereas post-systolic longitudinal strain and post-systolic strain in the two inner layers increased (P< 0.001). At early reperfusion, hyperaemia was evident in all layers (P< 0.01). Peak systolic TDI strain and strain rate increased in the mid- and subendocardial layer, whereas post-systolic strain decreased (P< 0.05). Peak systolic STE strain increased in the circumferential and longitudinal direction, whereas post-systolic longitudinal strain decreased (P< 0.05). At late reperfusion, strain and strain rate were unchanged while perfusion returned to baseline values in the mid- and subendocardium., Conclusion: Both multi-layer radial TDI strain and strain rate and one-layer STE strain measurements in the circumferential and longitudinal direction can confirm reperfusion early after a non-occlusive coronary stenosis. An advantage of multi-layer analysis was not evident.

Background: A single-dose strategy for cardioplegia is desired in minimal invasive approaches to valve surgery and aortic arch repairs. We hypothesized that a single infusion of Bretschneider HTK solution offers myocardial protection comparable to repeated cold oxygenated blood., Methods: Sixteen pigs on bypass with 60 minutes of aortic cross-clamping were randomized to a single dose of Custodiol (HTK group) or repeated oxygenated blood cardioplegia (CBC group). Left ventricular function and perfusion were evaluated by conductance catheter, echocardiography, and microspheres. Myocardial injury was assessed with serum troponin-T., Results: Baseline values showed no group differences. One hour after declamping cardiac index was reduced in the HTK group, 3.5 +/- 0.2 L x min(-1) x m(-2) (mean +/- standard error of the mean) compared with 4.7 +/- 0.4 L x min(-1) x m(-2) in the CBC group (p < 0.0005), decreasing to 4.0 +/- 0.2 and 3.9 +/- 0.2 L x min(-1) x m(-2) after 2 and 3 hours, respectively (p < 0.005 versus 1 hour). In the HTK group cardiac index remained low and unchanged. In the CBC group preload recruitable stroke work was 72.6 +/- 1.2 mm Hg 1 hour after declamping, decreasing to 65.2 +/- 2.5 and 60.3 +/- 3.9 mm Hg after 2 and 3 hours, respectively (p < 0.05 versus 1 hour). In the HTK group corresponding values after 1, 2, and 3 hours were low at 47.2 +/- 4.4, 48.4 +/- 4.2, and 50.7 +/- 4.3 mm Hg, respectively (p < 0.025 versus CBC for all). Subendocardial radial peak systolic strain averaged 80.5% +/- 4.8% after declamping in the CBC group versus 53.4% +/- 5.5% in the HTK group (p = 0.002). Serum troponin-T release was lower in the CBC group., Conclusions: Repeated oxygenated blood cardioplegia provides better myocardial protection and preservation of left ventricular function than a single dose of HTK during the early hours after declamping.

Objective: Myocardial dysfunction after reperfusion can be a clinical problem in the early postoperative phase after on-pump cardiac surgery. The aim was, in an experimental setting, to investigate if administration of the beta-adrenergic receptor blocker esmolol prior to cross-clamping for 80 min with cold oxygenated blood cardioplegia would improve myocardial protection and early postoperative function., Methods: Twenty-four anaesthetised pigs were randomly allocated into one of two equally sized groups and put on mild hypothermic cardiopulmonary bypass. Esmolol 1 mg kg(-1) or saline was administered into the arterial line 4 min prior to aortic cross-clamp. Cardiac arrest during 80 min of cross-clamp was obtained with repeated antegrade cold oxygenated blood cardioplegia; the pigs were weaned from bypass following a standardised protocol. Left ventricular global and regional myocardial function and tissue blood flow were evaluated with conductance catheter, echocardiography and coloured microspheres at baseline and at 1, 2 and 3 h after declamping. Four animals did not fulfil the protocol and were excluded., Results: No significant differences between groups could be demonstrated for left ventricular global and local function and tissue blood flow at baseline. At 1h after declamping the slope of preload recruitable stroke work (PRSW(slope)) averaged 73.7+/-12.7 mm Hg (SD) in controls and 72.7+/-11.1 mm Hg in esmolol-treated animals. In controls PRSW(slope) decreased to 62.1+/-11.0 and 58.4+/-12.7 mm Hg after 2 and 3h, respectively (p<0.005 vs 1h for both). In the esmolol-treated animals PRSW(slope) remained unchanged at 72.0+/-11.4 and 73.7+/-12.9 mm Hg at 2 and 3 h after declamp and were significantly higher (p<0.025 and <0.001) than the corresponding values in the control group. The slope of the end systolic pressure volume relationship did not differ between groups at 1 and 2 h after declamp, but were 1.85+/-0.86 and 2.51+/-0.96 mm Hg ml(-1) in controls and in esmolol-treated animals, respectively, after 3h (p<0.025)., Conclusions: Esmolol administered prior to cold oxygenated cardioplegic arrest alleviates left ventricular dysfunction in the early hours after cardiopulmonary bypass.