Vasopressin and blood flow to the canine small intestine

Low-dose vasopressin in the treatment of septic shock in sheep

After induction of cecal perforation, 20 anesthetized sheep were randomized to be treated, when arterial blood pressure fell below 75 mm Hg, with vasopressin (fixed dose of 0.02 U/minute), norepinephrine (0.5-5 microg/kg/minute titrated to maintain mean arterial pressure between 75 and 85 mm Hg), vasopressin + norepinephrine (vasopressin at fixed dose 0.01 U/minute plus norepinephrine titrated as for norepinephrine only group), or no vasopressor (Ringer's lactate [control]). Mean arterial pressure was well maintained in all treatment groups. Superior mesenteric arterial blood flow was significantly lower in the vasopressin + norepinephrine group than in the vasopressin group. Vasopressin alone or combined with norepinephrine limited the increase in blood lactate concentration and ileal PCO2-gap compared with control and norepinephrine groups. Urine output was higher in the vasopressin group than in control and norepinephrine groups. Survival time was longer in the vasopressin (30 +/- 6 hours) and vasopressin + norepinephrine (30 +/- 3 hours) groups than in the norepinephrine group (20 +/- 1 hours, p < 0.05) and in all treatment groups than in the control group (17 +/- 2 hours, p < 0.05). Tissue injury was less severe in the vasopressin and vasopressin + norepinephrine groups than in the others. In this clinically relevant model of septic shock due to peritonitis, vasopressin administration (alone or with norepinephrine) can prolong survival.

[Vasodilatory septic shock refractory to catecholamines: is there a role for terlipressin?]

We report two patients in vasodilatory septic shock refractory to catecholamines in which a continuous infusion of terlipressin was associated with a dramatic increase in systemic arterial blood pressure and short-term survival. Low doses of terlipressin were sufficient in both cases (0.01-0.0 mg h(-1)) to restore blood pressure by increase of systemic vascular resistances. The haemodynamic response was immediate, long-acting, dose-dependent and reversible in a few hours when the drug administration was stopped. A further increase in terlipressin dose regimen markedly decreased cardiac performance. Terlipressin simultaneously induced vasoconstriction within the cutaneous vascular territory, leading to local skin necrosis. The splanchnic vascular territory seemed to be constricted in the same way. Further studies are needed to better understand and precise the role of terlipressin in the treatment of vasodilatory septic shock refractory to catecholamines.

Vasopressin can increase coronary perfusion pressure during human cardiopulmonary resuscitation

OBJECTIVES

To determine the hemodynamic effect of vasopressin on coronary perfusion pressure (CPP) in prolonged human cardiac arrest.

METHODS

A prospective, open-label clinical trial of vasopressin during cardiac resuscitation was performed. Ten patients presenting in cardiac arrest initially received resuscitative measures by emergency physicians according to Advanced Cardiac Life Support (ACLS) guidelines. A central venous catheter for fluid and drug administration and a femoral artery catheter for measurement of CPP (aortic minus right atrial relaxation phase pressures) were placed. When each patient was deemed nonsalvageable, 1.0 mg epinephrine was given and CPP was measured for 5 minutes, followed by a dose of vasopressin (1.0 U/kg). CPP measurements were continued for another 5 minutes.

RESULTS

The mean duration of cardiac arrest (out-of-hospital interval plus duration of ED ACLS) was 39.6 +/- 16.5 min. There was no improvement in CPP after 1.0 mg of epinephrine. Vasopressin administration resulted in a significant increase of CPP in 4 of the 10 patients. Patients responding to vasopressin had a mean increase in CPP of 28.2 +/- 16.4 mm Hg (range: 10-51.5), with these peak increases occurring at 15 seconds to 4 minutes after administration. The increases in the vasopressin levels after administration did not differ between the responders and nonresponders.

CONCLUSIONS

In this human model of prolonged cardiac arrest, 40% of the patients receiving vasopressin had a significant increase in CPP. This pilot study suggests that investigation of earlier use of vasopressin as a therapeutic alternative in the treatment of cardiac arrest is warranted.

Hemodynamic and metabolic effects of vasopressin blockade in endotoxin shock

BACKGROUND

Arginine vasopressin V1 receptor antagonist (AVPRA) was administered to investigate the influence of vasopressin blockade on hemodynamics and metabolism during endotoxin shock.

METHODS

Anesthetized rats were divided into four groups: control (0.9% saline solution, n = 5), drug control (AVPRA, n = 5), endotoxin (endotoxin, 5 mg/kg, n = 10), and pretreatment (AVPRA and endotoxin, n = 10). Hemodynamics and oxygen transport were evaluated for 2 hours. Terminal arterial and portal venous concentrations of endotoxin, pyruvate, lactate, and ketone bodies were determined.

RESULTS

The endotoxin group maintained blood pressure levels similar to those of control animals. AVPRA pretreatment decreased vascular resistance and resulted in lower blood pressure than endotoxin alone. Endotoxin decreased oxygen consumption and the oxygen extraction ratio and increased arterial lactate concentration and the lactate/pyruvate ratio. Endotoxin also decreased arterial ketone body concentration and markedly decreased ketone body availability in the mesenteric circulation. AVPRA pretreatment improved oxygen consumption, oxygen extraction ratio, and ketone body availability; arterial lactate concentration, lactate/pyruvate ratio, and arterial ketone body concentration were not affected. Pretreatment with AVPRA also decreased arterial and portal venous concentrations of endotoxin.

CONCLUSIONS

Vasopressin receptor blockade during endotoxemia resulted in lower blood pressure than endotoxin alone. Vasopressin receptor blockade also maintained oxygen extraction ratio and ketone body availability in the mesenteric circulation. Vasopressin may play a key role in the response to endotoxemia.

The effect of global ischemia and reperfusion on the plasma levels of vasoactive peptides. The neuroendocrine response to cardiac arrest and resuscitation

OBJECTIVE

Return of spontaneous circulation with CPR is a function of coronary perfusion pressure, which is determined by vasomotor tone and the force of compression. Vasomotor tone is affected by the relative stimulation of arterial vasoconstricting and vasorelaxing receptors by vasoactive substances. We measured the plasma levels of the endogenous vasoactive peptides arginine vasopressin (AVP) angiotensin II (ANG-II) and atrial natriuretic peptide (ANP) during cardiac arrest and resuscitation.

DESIGN

A fibrillatory canine model of canine arrest was used. 'Down time' was greater than 10 min, during which no therapy, including BLS, was given. Standard ACLS was initiated at the end of the down time with manual external chest compression standardized to an esophageal pulse pressure of 50 mmHg. Blood samples were collected through an aortic catheter during spontaneous circulation and 3 min after initiation of ACLS. Peptide levels were measured using standard RIA techniques. Results are reported as the mean +/- S.D. in pg/ml.

RESULTS

AVP levels increased from a baseline of 1.7 +/- 1.0 pg/ml during spontaneous circulation to 29.9 +/- 33.3 during cardiac arrest and CPR (P = 0.01). There was a moderate positive correlation between aortic pressure and circulating AVP levels after the first dose of epinephrine (R = 0.5). There was a trend towards higher AVP levels in animals with return of spontaneous circulation (P = 0.12). ANG-II levels increased from a baseline of 14.7 +/- 12.9 pg/ml during spontaneous circulation to 151 +/- 105 during cardiac arrest and CPR (P < 0.05). ANP levels increased from a baseline of 55 +/- 46 pg/ml during spontaneous circulation to 293 +/- 73 during cardiac arrest and CPR (P < 0.01).

CONCLUSION

There were significant increases in the levels of these endogenous vasoactive peptides. This reflects the neuroendocrine response to global ischemia and CPR reperfusion. Plasma levels of these peptides may effect the vital organ perfusion pressures, response to exogenous vasopressors, and outcome of resuscitative efforts. Future therapies may be directed at enhancing or blocking the effect of these peptides so as to optimize perfusion pressure which is one of the principle determinants of outcome during CPR.

Comparison of vasopressin and triglycyl-lysine vasopressin on splanchnic and systemic hemodynamics in dogs

Triglycyl-lysine vasopressin (tGLVPP) is activated in the circulation when the N-triglycyl residue of the molecule is cleaved by endothelial peptidases, releasing lysine vasopressin. We compared the effect of an intravenous bolus dose of tGLV (20 micrograms/kg) with a constant infusion (2.75 mU/kg/min) of arginine and lysine vasopressin (Pitressin) in normal mongrel dogs. Portal pressure was artifactually increased by a constricting flow probe. Baseline values were similar in both groups; at the time of near-maximal reduction in portal pressure, both drugs equally reduced portal venous pressure (38 +/- 4 vs 39 +/- 4%), superior mesenteric arterial blood flow (40 +/- 8 vs 39 +/- 9%), portal venous flow (35 +/- 4 vs 40 +/- 5%), and heart rate (9 +/- 2 vs 11 +/- 7%. Cardiac output obtained 10-30 min after tGLVP administration was similar that of VP, and each drug reduced cardiac output significantly when compared with its own baseline (18 +/- 4 vs 21 +/- 7%). Mean arterial pressure increased similarly with both drugs (11 +/- 3 vs 11 +/- 3%). The only difference observed was the hepatic arterial flow response. While tGLVP increased HAF 34 +/- 11%, the physiologic autoregulatory response to a decrease in portal venous flow and pressure; vasopressin was associated with no such compensatory response (1 +/- 6%). Whether this advantage of tGLVP and its more prolonged reduction of portal venous pressure (mean 103 min) are beneficial in the clinical setting requires additional studies.