[Monitoring and treatment of patients with shock in the intensive care unit]

The controversy surrounding the use of the pulmonary artery catheter, has stimulated research into alternative methods of haemodynamic monitoring. As yet, however, no new gold standard has emerged. In the future, interest in haemodynamic monitoring is likely to focus more on tissue perfusion and metabolism instead of central circulation. Important causes of shock in the ICU, apart from acute blood loss, are sepsis and acute heart failure. Septic shock results from vasodilatation and myocardial dysfunction. Early initiation of aggressive fluid resuscitation, if necessary accompanied by vasoactive and inotropic agents, improves survival. In addition, low dose corticosteroids have a positive impact on mortality. In the treatment of patients with acute heart failure, phosphodiesterase III-inhibitors are becoming part of standard therapy in addition to beta-adrenoceptor agonists, especially in patients who take beta-blockers.

[The value of the pulmonary-artery catheter: not ruled out, but not proven either]

A number of prospective, randomized trials have recently been published on the effects of using the pulmonary artery (Swan-Ganz) catheter in the peri-operative management of high-risk patients and in the treatment of critically ill patients on the intensive-care unit. These studies show that using the pulmonary-artery catheter does not lead to increased survival. It cannot be excluded that more beneficial effects would have been found with other treatment goals, or if different populations had been studied. However, based on the present evidence from the literature, the routine use of the pulmonary-artery catheter can no longer be defended.

Assessment of cardiovascular reflexes is of limited value in predicting maximal +Gz-tolerance

The importance of +Gz-induced loss of consciousness as a major cause of inflight incapacitation emphasizes the need for predicting +Gz-tolerance and investigating its possible determinants. The cardiovascular changes from +Gz-stress are initially counteracted reflexly by the cardiovascular autonomic system. The integrity of neural cardiovascular reflex control can be assessed by analysing the blood pressure (BP) and heart rate (HR) responses to different maneuvers, such as the Valsalva maneuver, standing and forced respiratory sinus arrhythmia. The aim of the present study was to investigate a possible relation between the cardiovascular responses to these tests and +Gz-tolerance. In 10 healthy subjects continuous Finapres BP and HR responses to the tests have been determined and correlated with their G-levels of peripheral light loss (PLL) during centrifuge-runs (0.1 G/s). Only mean BP recovery during Valsalva maneuver correlated marginally significantly with PLL (r = 0.63, p = 0.049). Cardiovascular findings were within normal range revealing no cardiovascular autonomic dysfunction. These results indicate that intact neural cardiovascular control seems to be a condition for tolerating +Gz-stress without determining maximal +Gz-tolerance. We conclude that assessment of cardiovascular reflexes may only confirm baroreflex integrity. However, they have limited value in predicting +Gz-tolerance.

Cardiovascular response to coughing: its value in the assessment of autonomic nervous control

1. The relationship between blood pressure and heart rate responses to coughing was investigated in 10 healthy subjects in three body positions and compared with the circulatory responses to commonly used autonomic function tests: forced breathing, standing up and the Valsalva manoeuvre. 2. We observed a concomitant intra-cough increase in supine heart rate and blood pressure and a sustained post-cough elevation of heart rate in the absence of arterial hypotension. These findings indicate that the sustained increase in heart rate in response to coughing is not caused by arterial hypotension and that these heart rate changes are not under arterial baroreflex control. 3. The maximal change in heart rate in response to coughing (28 +/- 8 beats/min) was comparable with the response to forced breathing (29 +/- 9 beats/min, P greater than 0.4), with a reasonable correlation (r = 0.67, P less than 0.05), and smaller than the change in response to standing up (41 +/- 9 beats/min, P less than 0.01) and to the Valsalva manoeuvre (39 +/- 13 beats/min, P less than 0.01). 4. Quantifying the initial heart rate response to coughing offers no advantage in measuring cardiac acceleratory capacity; standing up and the Valsalva manoeuvre are superior to coughing in evaluating arterial baroreflex cardiovascular function.