Fig. 5

Theoretical model explaining different patterns of change in stroke volume after phenylephrine administration. (A) Venous return (left) and cardiac output (right) during post-induction hypotension and after phenylephrine administration in patients with high total peripheral resistance and preload dependency (Group 1). The crossing point of the respective venous return and SV curves indicates the instantaneous working point of the heart during post-induction hypotension (a). The new crossing point a’ is observed after the administration of phenylephrine. (B) The crossing point of the respective venous return and SV curves indicates the instantaneous working point of the heart at post-induction hypotension (b) in patients with low total peripheral resistance and preload dependency (Group 2). The new crossing point b’ is observed after the administration of phenylephrine. (C) The crossing point of the respective venous return and SV curves indicates the instantaneous working point of the heart at post-induction hypotension (c) in patients with high total peripheral resistance and preload independency (Group 3). The new crossing point c’ is observed after the administration of phenylephrine. (D) The crossing point of the respective venous return and SV curves indicates the instantaneous working point of the heart at post-induction hypotension (d) in patients with low total peripheral resistance and preload independency (Group 4). The new crossing point d’ is observed after the administration of phenylephrine. SV, stroke volume