pituitrin and Cardiac-Output--High

The arteriovenous fistula model of circulation can produce a high output and low peripheral resistance situation. Here, we have examined the effects of noradrenaline, vasopressin and sodium nitroprusside on cardiac index, mean arterial blood pressure, venous tone, resistance to venous return, arterial resistance, and blood volume in chronically shunted anaesthetized rats. The cardiac index of rats with chronic arteriovenous fistula (AVF) was significantly higher (36.65+/-2.28 ml/min per 100 g; (mean+/-S.E.M.; n=24) in comparison to sham-operated rats (20.04+/-0.86 ml/min per 100 g; mean+/-S.E.M.; n=8). Cardiac index did not significantly change during the infusion of noradrenaline (1.0, 3.0 and 10 microg/kg per min), vasopressin (10, 30, 100 ng/kg per min) or sodium nitroprusside (0.1, 0.3 and 1.0 microg/kg per min) compared to saline infusion in AVF animals. Infusion of noradrenaline significantly increased heart rate, dP/dt, mean circulatory filling pressure (Pmcf) and resistance to venous return without affecting mean arterial blood pressure when compared to saline infusion. Administration of vasopressin significantly increased dP/dt, mean arterial blood pressure, and Pmcf without affecting heart rate, resistance to venous return or arterial resistance compared to saline infusion. Infusion of sodium nitroprusside did not significantly affect any haemodynamic parameter measured when compared to saline infusion. The results indicate that the presence of chronic AVF alters responsiveness of the various segments of the circulatory system to vasoactive agents. Moreover, it produces a major impediment to overall changes that can normally be induced following the infusion of such agents.

Topics: Anesthesia; Animals; Arteriovenous Fistula; Blood Pressure; Blood Volume; Body Weight; Cardiac Output; Cardiac Output, High; Heart; Heart Rate; Lung; Male; Nitroprusside; Norepinephrine; Organ Size; Rats; Rats, Sprague-Dawley; Vascular Resistance; Vasoconstrictor Agents; Vasodilator Agents; Vasopressins

We report the case of a 65-year-old man who developed norepinephrine-resistant vasoplegic syndrome after elective off-pump coronary artery bypass surgery (OPCAB). The failure of norepinephrine to improve the patient's hemodynamics prompted us to start treatment with vasopressin; within 30 minutes, the hemodynamics began to improve. After 12 hours, the patient was stable enough to be weaned from the vasopressin. He was discharged from the hospital on the 10th postoperative day. To our knowledge, ours is the 1st report of vasopressin use for vasodilatory shock after OPCAB in the English-language medical literature. Herein, we discuss the pathophysiology and management of vasoplegic syndrome--which is controversial--with special emphasis on the use of vasopressin in this situation.

Topics: Aged; Blood Pressure; Cardiac Output, High; Coronary Artery Bypass, Off-Pump; Humans; Hypotension; Male; Syndrome; Tachycardia; Vascular Resistance; Vasoconstrictor Agents; Vasopressins