Hormonal responses and cardiac filling pressures in head-up or head-down position and pneumoperitoneum in patients undergoing operative laparoscopy.

In order to determine if there are differences in stress responses, as reflected in neuroendocrine activation, we have compared data from two groups of patients undergoing laparoscopic surgery either in the head-up position for cholecystectomy or in the head-down position for hysterectomy. Arterial blood samples were obtained for measurement of serum concentrations of cortisol, catecholamines, renin activity and atrial natriuretic peptide (measured as N-terminal peptide of proANP), and haemodynamic data (pulmonary capillary wedge pressure, PCWP) were collected at the following times: in awake patients, supine at rest (baseline); in awake patients in the position used during surgery; during laparoscopy; and 2 h after surgery. The same anaesthetic technique and normocapnic mechanical ventilation were used in both groups. There were no significant differences between groups in cortisol or adrenaline concentrations, or in renin activity. There was, however, a three-fold increase in cortisol towards the recovery period in both groups. Noradrenaline concentrations increased more in the head-up group suggesting increased sympathetic nervous activity. In awake patients, plasma NT-proANP concentrations were significantly higher in the head-down tilt compared with the head-up position, and NT-proANP correlated well with PCWP. During pneumoperitoneum, however, NT-proANP concentrations remained low in spite of increased PCWP suggesting that inflation of the abdomen interferes with venous return. In conclusion, abdominal surgical laparoscopy in both the head-up and head-down positions caused marked activation of neuroendocrine responses. The two surgical positions, however, differed in their effect on the circulation. In awake patients, head-down tilt was associated with increased concentrations of plasma NT-proANP, indicating increased venous return and atrial stretch.