ABSTRACT
Pathophysiologic mechanisms of bradycardia during epidural anaesthesia (L3-L4 with 1% lidocaine, 38 ml) were evaluated by studying changes in selected cardiovascular and hormonal parameters. Six of eight subjects (analgesia to T8-T10) remained circulatory stable with no significant changes in heart rate (HR), mean arterial pressure (MAP) and thoracic impedance (TI). In one of two subjects MAP decreased after 25 min from 85 to 50 mmHg (11.3 to 6.7 kPa), HR from 80 to 45 beats.min-1 while thoracic impedance increased from 25.5 to 26.5 ohm. End-systolic diameter (ESD) and end-diastolic diameter (EDD) of the left ventricle determined with echocardiography were reduced from 3.8 to 3.2 cm (17%) and 5.6 to 5.0 cm (11%), respectively. In the other subject MAP decreased after 25 min from 75 to 50 mmHg (10.0 to 6.7 kPa) and HR from 82 to 60 beats.min-1 while thoracic impedance increased from 28.8 to 29.6 ohm. ESD was reduced from 3.8 to 3.3 cm (13%), and EDD from 5.6 to 5.0 cm (11%). Both subjects recovered after infusion of saline and being placed in the head-down position. There were no consistent changes in plasma catecholamines, whereas pancreatic polypeptide increased from 5 and 3 to 152 and 69 pmol.l-1, vasopressin from 3 and 2 to 152 and 46 pmol.l-1, and aldosterone from 282 and 229 to 383 and 485 pmol.l-1, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)
Subject(s)
Anesthesia, Epidural , Bradycardia/pathology , Bradycardia/physiopathology , Heart Ventricles/pathology , Ventricular Function, Left/physiology , Adult , Aldosterone/blood , Arginine Vasopressin/blood , Blood Pressure/drug effects , Blood Pressure/physiology , Bradycardia/diagnostic imaging , Cardiac Output/drug effects , Cardiac Output/physiology , Cardiography, Impedance/drug effects , Echocardiography , Epinephrine/blood , Female , Heart Rate/drug effects , Heart Rate/physiology , Heart Ventricles/diagnostic imaging , Humans , Lidocaine/administration & dosage , Lidocaine/pharmacology , Male , Norepinephrine/blood , Pancreatic Polypeptide/blood , Stroke Volume/drug effects , Stroke Volume/physiology , Ventricular Function, Left/drug effectsABSTRACT
Heart rate (HR), mean arterial pressure (MAP), indices of sympathetic and parasympathetic activity (plasma concentrations of adrenaline, noradrenaline and pancreatic polypeptide, PP), vasopressin (VP) and aldosterone (ALDO) were measured in six pigs during continuous bleeding resulting in hypovolaemic shock, from which five survived. Three stages of haemorrhage could be defined. Stage I. Resting MAP was 85 +/- 6 mmHg and increased to 96 +/- 5 mmHg with a blood loss of 275 (range 250-300) (10 (9-12)% of the estimated blood volume) concomitant with an increase in HR from 105 +/- 5 to 113 +/- 6 beats min-1 (P less than 0.05). Stage II. After a blood loss of 375 (300-500) ml (15 (13-16)%) MAP fell to 62 +/- 9 mmHg and HR to 95 +/- 5 beats min-1 (P less than 0.05). Stage III. A blood loss of 1113 (825-1450) ml (44 (30-52)%) resulted in a MAP of 50 +/- 4 mmHg and an increase in HR to 206 +/- 3 beats min-1 (P less than 0.05). Adrenaline increased from 0.3 +/- 0.1 to 0.8 +/- 0.3 (stage II) and 3.6 +/- 1.1 nmol l-1 (stage III) (P less than 0.05); noradrenaline from 0.4 +/- 0.1 to 1.5 +/- 0.4 (stage II) and 5.9 +/- 1.7 nmol l-1 (stage III) (P less than 0.05); PP from 6.2 +/- 1.6 to 13.3 +/- 2.3 (stage II) and 20.9 +/- 7.8 pmol l-1 (stage III) (P less than 0.05). VP changed only marginally, but ALDO increased from 496 +/- 54 to 623 +/- 76 pmol l-1 (stage III) (P less than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)
