Magnesium: physiology and pharmacology.

Magnesium has an established role in obstetrics and an evolving role in other clinical areas, in particular cardiology. Many of the effects involving magnesium are still a matter of controversy. Over the next decade, it is likely that improvements in the measurement of magnesium, a clearer understanding of the mechanisms of its actions and further results of clinical studies will help to elucidate its role, both in terms of treating deficiency and as a pharmacological agent.

Cardiopulmonary bypass with danaparoid sodium and ancrod in heparin-induced thrombocytopenia.

Heparin is the standard anticoagulant for patients undergoing cardiopulmonary bypass. There are some patients for whom heparin is unsuitable and ancrod (a defibrinogenating enzyme) has been used as an alternative. We present a patient with heparin-induced thrombocytopenia in whom treatment ancrod was ineffective. The addition of danaparoid sodium (a heparinoid) allowed safe cardiopulmonary bypass. We discuss the reasons for this and suggest that the combination of ancrod and danaparoid sodium is a logical one in such cases.

Assessment of cardiovascular changes during laparoscopic hernia repair using oesophageal Doppler.

We have used an oesophageal Doppler to measure aortic blood flow velocity before, during and after induction of carbon dioxide pneumoperitoneum in 10 consecutive patients, mean age 58 yr, undergoing laparoscopic hernia repair. Derived values for stroke distance, minute distance and systemic vascular resistance showed considerable interpatient variation indicating unpredictable haemodynamic responses. Five minutes after insufflation of the abdomen there was a significant increase in mean arterial pressure from 82.5 to 103.6 mm Hg (P < 0.05) but both stroke distance and minute distance decreased significantly (mean 12.0 (SEM 1.4) cm to 9.0 (0.7) cm, P < 0.05; and 747.5 (82) cm min-1 to 596 (49) cm min-1, P < 0.05; respectively) indicating a significant decrease in cardiac output. There was a corresponding increase in the index of systemic vascular resistance from 1092 (747) to 2079 (400) (P < 0.05) which persisted after deflation of the abdomen. Oesophageal Doppler can provide continuous online haemodynamic data with a rapid response to acute changes and may have a role in non-invasive haemodynamic monitoring during laparoscopic procedures in older patients with cardiovascular disease.