In Vitro Negative Inotropic Effect of Low Concentrations of Bupivacaine Relates to Diminished Ca2+ Sensitivity but not to Ca2+ Handling or β-Adrenoceptor Signaling

TY - JOUR

T1 - In Vitro Negative Inotropic Effect of Low Concentrations of Bupivacaine Relates to Diminished Ca2+ Sensitivity but not to Ca2+ Handling or β-Adrenoceptor Signaling

AU - Flenner, Frederik

AU - Arlt, Nicole

AU - Nasib, Mahtab

AU - Schobesberger, Sophie

AU - Koch, Thea

AU - Ravens, Ursula

AU - Friedrich, Felix

AU - Nikolaev, Viacheslav

AU - Christ, Torsten

AU - Stehr, Sebastian N

PY - 2018/6

Y1 - 2018/6

N2 - BACKGROUND: Systemic toxicity of local anesthetics is predominantly complicated by their myocardial toxicity. Especially long-acting local anesthetics exert a negative inotropic effect that has been described at lower concentrations than defined for blockade of myocardial ion channels. We evaluated the negative inotropic effect of bupivacaine at a concentration described for clinical toxicity testing the hypothesis that negative inotropy is a result of reduced Ca sensitivity rather than blockade of ion channels.METHODS: We simultaneously measured force development and action potentials in guinea pig right papillary muscles (n = 5 to 7). L-type Ca currents (n = 8 to 16) and Ca transients (n = 10 to 11) were measured in isolated cardiomyocytes. Sensitivity of myofilaments to Ca was assessed in skinned fibers (n = 10). Potential effects of bupivacaine on 3',5'-cyclic adenosine monophosphate concentrations were measured using Förster Resonance Energy Transfer (n = 12 to 14) microscopy.RESULTS: Bupivacaine reduced force in a concentration-dependent manner from 173 ± 119 µN at baseline to 28 ± 13 µN at 300 µM (mean ± SD). At concentrations giving half-maximum negative inotropic effects (5 µM), the maximum upstroke velocity of action potentials, as a surrogate of sodium channel activity, was unaffected. Maximum positive inotropic effects of isoprenaline were also reduced to 50%. Neither basal nor isoprenaline-induced 3',5'-cyclic adenosine monophosphate accumulation, L-type Ca currents, or Ca transients were affected by 5 µM bupivacaine, but this concentration significantly decreased Ca sensitivity of myofilaments, changing the negative logarithm of the half-maximum effective Ca concentrations from 5.66 to 5.56 -log[M].CONCLUSIONS: We provide evidence that the negative inotropic effect of bupivacaine may be caused mainly by a reduction in myofilament sensitivity to Ca.

AB - BACKGROUND: Systemic toxicity of local anesthetics is predominantly complicated by their myocardial toxicity. Especially long-acting local anesthetics exert a negative inotropic effect that has been described at lower concentrations than defined for blockade of myocardial ion channels. We evaluated the negative inotropic effect of bupivacaine at a concentration described for clinical toxicity testing the hypothesis that negative inotropy is a result of reduced Ca sensitivity rather than blockade of ion channels.METHODS: We simultaneously measured force development and action potentials in guinea pig right papillary muscles (n = 5 to 7). L-type Ca currents (n = 8 to 16) and Ca transients (n = 10 to 11) were measured in isolated cardiomyocytes. Sensitivity of myofilaments to Ca was assessed in skinned fibers (n = 10). Potential effects of bupivacaine on 3',5'-cyclic adenosine monophosphate concentrations were measured using Förster Resonance Energy Transfer (n = 12 to 14) microscopy.RESULTS: Bupivacaine reduced force in a concentration-dependent manner from 173 ± 119 µN at baseline to 28 ± 13 µN at 300 µM (mean ± SD). At concentrations giving half-maximum negative inotropic effects (5 µM), the maximum upstroke velocity of action potentials, as a surrogate of sodium channel activity, was unaffected. Maximum positive inotropic effects of isoprenaline were also reduced to 50%. Neither basal nor isoprenaline-induced 3',5'-cyclic adenosine monophosphate accumulation, L-type Ca currents, or Ca transients were affected by 5 µM bupivacaine, but this concentration significantly decreased Ca sensitivity of myofilaments, changing the negative logarithm of the half-maximum effective Ca concentrations from 5.66 to 5.56 -log[M].CONCLUSIONS: We provide evidence that the negative inotropic effect of bupivacaine may be caused mainly by a reduction in myofilament sensitivity to Ca.

KW - Journal Article

U2 - 10.1097/ALN.0000000000002180

DO - 10.1097/ALN.0000000000002180

M3 - SCORING: Journal article

C2 - 29547406

VL - 128

SP - 1175

EP - 1186

JO - ANESTHESIOLOGY

JF - ANESTHESIOLOGY

SN - 0003-3022

IS - 6

ER -