Employing dobutamine as a useful agent to reverse the terlipressin-linked impairments in cardiopulmonary hemodynamics and global oxygen transport in healthy and endotoxemic sheep

Therapeutic regimens of endotoxaemia in sheep

Endotoxaemia is an inflammatory condition which happens due to the presence of outer cell wall layer of Gram-negative bacteria in blood circulation, containing lipopolysaccharide commonly known as endotoxin. This condition causes high mortality in affected animals and sheep are highly susceptible in this regard. Several researchers have emphasised the therapeutic regimens of endotoxaemia and its sequels in sheep. Furthermore, sheep are among the most commonly used animal species in experimental studies on endotoxaemia, and for the past five decades, ovine models have been employed to evaluate different aspects of endotoxaemia. Currently, there are several studies on experimentally induced endotoxaemia in sheep, and information regarding novel therapeutic protocols in this species contributes to better understanding and treating the condition. This review aims to specifically introduce various treatment methods of endotoxaemia in sheep.

The effects of terlipressin on regional hemodynamics and kidney function in experimental hyperdynamic sepsis

Background and Aims

Although terlipressin (TP) may improve renal function in cirrhotic patients, its use in sepsis remains controversial due to concerns about regional ischemia. We investigated the effects of TP on regional hemodynamics and kidney function in experimental hyperdynamic sepsis.

Methods

We studied thirteen merino ewes in a university physiology laboratory using a randomized controlled cross over design. We implanted flow probes around the pulmonary, circumflex coronary, superior mesenteric, renal and iliac arteries. We injected live Escherichia coli and induced hyperdynamic sepsis. We treated animals with either bolus vehicle or a single dose of TP (sTP = 1 mg). In a second group, after 1 mg of TP, two additional bolus injections (mTP) of 0.5 mg were given at 2 hourly intervals.

Main Results

sTP (1 mg) significantly increased mean arterial pressure (MAP) (74 to 89 mmHg; P<0.0001) creatinine clearance (31 to 85 mL/min; P<0.0001) and urine output (24 to 307 mL/hr) (P<0.0001). However, it decreased CO (5.7 to 3.9 L/min; p<0.0001), coronary blood flow (CBF) (43 to 32 mL/min; p<0.0001) and mesenteric blood flow (MBF) (944 to 625 mL/min; p = 0.004) and increased blood lactate (2.1 to 4.0 mmol/L; p<0.0001). Extra doses of TP caused little additional effect.

Conclusions

In hyperdynamic sepsis, bolus TP transiently improves MAP and renal function, but reduces CO, CBF and MBF, and increases blood lactate. Caution should be applied when prescribing bolus TP in septic patients at risk of coronary or mesenteric ischemia.

Bench-to-bedside review: Vasopressin in the management of septic shock

This review of vasopressin in septic shock differs from previous reviews by providing more information on the physiology and pathophysiology of vasopressin and vasopressin receptors, particularly because of recent interest in more specific AVPR1a agonists and new information from the Vasopressin and Septic Shock Trial (VASST), a randomized trial of vasopressin versus norepinephrine in septic shock. Relevant literature regarding vasopressin and other AVPR1a agonists was reviewed and synthesized. Vasopressin, a key stress hormone in response to hypotension, stimulates a family of receptors: AVPR1a, AVPR1b, AVPR2, oxytocin receptors and purinergic receptors. Rationales for use of vasopressin in septic shock are as follows: first, a deficiency of vasopressin in septic shock; second, low-dose vasopressin infusion improves blood pressure, decreases requirements for norepinephrine and improves renal function; and third, a recent randomized, controlled, concealed trial of vasopressin versus norepinephrine (VASST) suggests low-dose vasopressin may decrease mortality of less severe septic shock. Previous clinical studies of vasopressin in septic shock were small or not controlled. There was no difference in 28-day mortality between vasopressin-treated versus norepinephrine-treated patients (35% versus 39%, respectively) in VASST. There was potential benefit in the prospectively defined stratum of patients with less severe septic shock (5 to 14 μg/minute norepinephrine at randomization): vasopressin may have lowered mortality compared with norepinephrine (26% versus 36%, respectively, P = 0.04 within stratum). The result was robust: vasopressin also decreased mortality (compared with norepinephrine) if less severe septic shock was defined by the lowest quartile of arterial lactate or by use of one (versus more than one) vasopressor at baseline. Other investigators found greater hemodynamic effects of higher dose of vasopressin (0.06 units/minute) but also unique adverse effects (elevated liver enzymes and serum bilirubin). Use of higher dose vasopressin requires further evaluation of efficacy and safety. There are very few studies of interactions of therapies in critical care - or septic shock - and effects on mortality. Therefore, the interaction of vasopressin infusion, corticosteroid treatment and mortality of septic shock was evaluated in VASST. Low-dose vasopressin infusion plus corticosteroids significantly decreased 28-day mortality compared with corticosteroids plus norepinephrine (44% versus 35%, respectively, P = 0.03; P = 0.008 interaction statistic). Prospective randomized controlled trials would be necessary to confirm this interesting interaction. In conclusion, low-dose vasopressin may be effective in patients who have less severe septic shock already receiving norepinephrine (such as patients with modest norepinephrine infusion (5 to 15 μg/minute) or low serum lactate levels). The interaction of vasopressin infusion and corticosteroid treatment in septic shock requires further study.

Vascular hyporesponsiveness to vasopressors in septic shock: from bench to bedside

PURPOSE

To delineate some of the characteristics of septic vascular hypotension, to assess the most commonly cited and reported underlying mechanisms of vascular hyporesponsiveness to vasoconstrictors in sepsis, and to briefly outline current therapeutic strategies and possible future approaches.

METHODS

Source data were obtained from a PubMed search of the medical literature with the following MeSH terms: Muscle, smooth, vascular/physiopathology; hypotension/etiology; shock/physiopathology; vasodilation/physiology; shock/therapy; vasoconstrictor agents.

RESULTS

Nitric oxide (NO) and peroxynitrite are crucial components implicated in vasoplegia and vascular hyporeactivity. Vascular ATP-sensitive and calcium-activated potassium channels are activated during shock and participate in hypotension. In addition, shock state is characterized by inappropriately low plasma glucocorticoid and vasopressin concentrations, a dysfunction and desensitization of alpha-receptors, and an inactivation of catecholamines by oxidation. Numerous other mechanisms have been individualized in animal models, the great majority of which involve NO: MEK1/2-ERK1/2 pathway, H(2)S, hyperglycemia, and cytoskeleton dysregulation associated with decreased actin expression.

CONCLUSIONS

Many therapeutic approaches have proven their efficiency in animal models, especially therapies directed against one particular compound, but have otherwise failed when used in human shock. Nevertheless, high doses of catecholamines, vasopressin and terlipressin, hydrocortisone, activated protein C, and non-specific shock treatment have demonstrated a partial efficiency in reversing sepsis-induced hypotension.

Terlipressin, a provasopressin drug exhibits direct vasoconstrictor properties: consequences on heart perfusion and performance

OBJECTIVE

Terlipressin has been proposed as an alternative treatment to catecholamines to restore blood pressure in septic shock. Terlipressin is considered as a vasopressin prodrug capable of releasing small but sustained amounts of [Lysine] vasopressin (LVP) and to provide prolonged biological effect. However, terlipressin may act as a direct vasopressor beyond its conversion into LVP. We investigated terlipressin direct vasoconstrictive properties and consequences on myocardial perfusion and performance.

DESIGN

Experimental studies.

SETTINGS

National Research Institute Laboratories.

SUBJECTS

Rat aorta and heart, human uterine artery.

INTERVENTIONS

Studies of vasoconstriction on isolated vascular rings obtained either from rat aorta or human uterine artery, and of coronary flow, ventricular performance, and heart rhythm on rat hearts using a modified Langendorff heart apparatus.

MEASUREMENTS AND MAIN RESULTS

Terlipressin induced a rapid, saturable, and dose-dependent contraction of rat aortas and human uterine arteries. Although the maximal terlipressin-induced vasoconstriction observed on rat arteries was weaker than LVP, or arginine-vasopressin, pharmacologic properties on human arteries, such as full agonism and strong maximal effect (900% of the maximal response obtained with phenylephrine), suggest a high potential of terlipressin to directly vasoconstrict human vessels. Similarly, terlipressin induced a saturable and dose-dependent vasoconstriction of coronary arteries that was reversible and antagonized by selective V1a antagonists. Maximum rates of left ventricle pressure rise (dP/dtmax) and fall (dP/dtmin) decreased both only in proportion to the decrease in coronary flow.

CONCLUSIONS

Besides long lasting effect through slow conversion into LVP, terlipressin is a fast acting vasopressor peptide per se that has an impact on coronary circulation and myocardial function.

Effects of short-term simultaneous infusion of dobutamine and terlipressin in patients with septic shock: the DOBUPRESS study

BACKGROUND

Terlipressin bolus infusion may reduce cardiac output and global oxygen supply. The present study was designed to determine whether dobutamine may counterbalance the terlipressin-induced depression in mixed-venous oxygen saturation (Svo) in patients with catecholamine-dependent septic shock.

METHODS

Prospective, randomized, controlled study performed in a university hospital intensive care unit. Septic shock patients requiring a continuous infusion of norepinephrine (0.9 microg kg(-1) min(-1)) to maintain mean arterial pressure (MAP) at 70 (sd 5) mm Hg were randomly allocated to be treated either with (i) sole norepinephrine infusion (control, n=20), (ii) a single dose of terlipressin 1 mg (n=19), or (iii) a single dose of terlipressin 1 mg followed by dobutamine infusion titrated to reverse the anticipated reduction in Svo2 (n=20). Systemic, pulmonary, and regional haemodynamic variables were obtained at baseline and after 2 and 4 h. Laboratory surrogate markers of organ (dys)function were tested at baseline and after 12 and 24 h.

RESULTS

Terlipressin (with and without dobutamine) infusion preserved MAP at 70 (5) mm Hg, while allowing to reduce norepinephrine requirements to 0.17 (0.2) and 0.2 (0.2) microg kg(-1) min(-1), respectively [vs1.4 (0.3) microg kg(-1) min(-1) in controls at 4 h; each P<0.001]. The terlipressin-linked decrease in Svo2 was reversed by dobutamine at a mean dose of 20 (8) microg kg(-1) min(-1) [Svo2 at 4 h: 59 (11)% vs 69 (12)%, P=0.028].

CONCLUSIONS

In human catecholamine-dependent septic shock, terlipressin (with and without concomitant dobutamine infusion) increases MAP and markedly reduces norepinephrine requirements. Although no adverse events were noticed in the present study, potential benefits of increasing Svo2 after terlipressin bolus infusion need to be weighted against the risk of cardiovascular complications resulting from high-dose dobutamine.