Effects of local injection of prilocaine-felypressin on the myocardial oxygen balance in dogs

Therapeutic potential of vasopressin in the treatment of neurological disorders

Vasopressin (VP) is a nonapeptide made of nine amino acids synthesized by the hypothalamus and released by the pituitary gland. VP acts as a neurohormone, neuropeptide and neuromodulator and plays an important role in the regulation of water balance, osmolarity, blood pressure, body temperature, stress response, emotional challenges, etc. Traditionally VP is known to regulate the osmolarity and tonicity. VP and its receptors are widely expressed in the various region of the brain including cortex, hippocampus, basal forebrain, amygdala, etc. VP has been shown to modulate the behavior, stress response, circadian rhythm, cerebral blood flow, learning and memory, etc. The potential role of VP in the regulation of these neurological functions have suggested the therapeutic importance of VP and its analogues in the management of neurological disorders. Further, different VP analogues have been developed across the world with different pharmacotherapeutic potential. In the present work authors highlighted the therapeutic potential of VP and its analogues in the treatment and management of various neurological disorders.

Impact of dexmedetomidine on the tissue distribution, anesthetic action, and hemodynamic effects of mepivacaine

The present study investigated the regional blood flow, tissue distribution, local anesthetic action, and hemodynamic effects of mepivacaine containing dexmedetomidine hydrochloride (DEX) in rats. Blood flow was measured after injection of 0.5% mepivacaine (M group), 12.5 µg/ml DEX (D group), or 0.5% mepivacaine containing 12.5 µg/ml DEX (DM group) into the upper lip. Mepivacaine distribution was autoradiographically observed in maxillary bone resected after injection of 0.5% ³H-mepivacaine (HM group) or 0.5% ³H-mepivacaine containing 12.5 µg/ml DEX (DHM group) into the palatal mucosa adjacent to the right maxillary first molar. Radioactivity was also measured using a liquid scintillation counter. SEP were measured to analyze anesthetic action. Blood pressure and heart rate were measured to compare hemodynamic effect. The addition of DEX significantly decreased blood flow compared to M group from 10 to 60 min after injection. The addition of DEX significantly increased the amount of radioactivity compared to HM group in the palatal mucosa from 5 to 60 min after injection and in the body of the maxilla from 2 to 60 min after injection. Maximum blood radioactivity was measured at 5 min after injection in HM group and 50 min after injection in DHM group. The addition of DEX significantly decreased peak-to-peak amplitudes compared to M group until 60 min after injection. No significant hemodynamic differences were observed. DEX enhances the action of mepivacaine in reducing regional blood flow prolongs its tissue retention, and increases the local anesthetic action without affecting hemodynamics on local administration.

Dexmedetomidine Enhances the Pulpal Anesthetic Effect of Lidocaine: A Pilot Study

Dexmedetomidine hydrochloride (DEX) demonstrates analgesic, sedative, and hypotensive effects. DEX may also enhance the effect of local anesthetics used in the oral cavity, although this has not been well established in combination with lidocaine. We conducted a single-blind crossover study in 8 healthy volunteers to investigate whether DEX enhances the anesthetic effect of lidocaine in the oral cavity. DEX or DEX + lidocaine was injected into the labial gingiva corresponding to the root apex of the maxillary left central incisor and into the buccal gingiva corresponding to the root apex of the mandibular right first molar. Pain threshold, blood pressure, pulse rate, oxygen saturation, and bispectral index were measured 5 minutes after treatment and at 10-minute intervals for 60 minutes. DEX + lidocaine caused pulpal anesthesia in more subjects than lidocaine alone; this difference was significant for both central incisors and first molars up to 40 minutes after treatment. Following DEX + lidocaine treatment, blood pressure and bispectral index were significantly reduced at several time points, and pulse rate significantly reduced at all time points. Neither treatment caused changes in oxygen saturation. In conclusion, administering DEX with lidocaine for dental local anesthesia caused sedation and enhanced local anesthesia compared to lidocaine alone.

Felypressin, but not epinephrine, reduces myocardial oxygen tension after an injection of dental local anesthetic solution at routine doses

PURPOSE

The aim of this study was to evaluate the effect of epinephrine (Epi) or felypressin (Fely) contained in dental local anesthetics on myocardial oxygen balance.

MATERIALS AND METHODS

Male Japanese White tracheotomized rabbits were anesthetized with isoflurane. Three doses of 0.18, 0.36, and 0.72 mL of 2% lidocaine hydrochloride containing 1:80,000 Epi or 3% prilocaine hydrochloride containing Fely 0.03 IU/mL were injected into the rabbit tongue muscle. These doses were equivalent to 2, 4, and 8 of dental local anesthetic cartridges in humans weighing 50 kg by body weight correction, respectively. Heart rate, blood pressure, aortic blood flow, myocardial tissue blood flow, and myocardial tissue oxygen tension were continuously monitored. Data were recorded immediately before and 10, 20, 30, and 60 minutes after the injection.

RESULTS

Heart rate decreased in the Fely group. Systolic blood pressure increased in the Epi group, and diastolic blood pressure increased in both groups. Aortic blood flow and myocardial tissue blood flow increased, whereas myocardial tissue oxygen tension did not change in the Epi group. In contrast, aortic blood flow, myocardial tissue blood flow, and myocardial tissue oxygen tension decreased in the Fely group.

CONCLUSION

It is suggested that Fely, but not Epi, decreases myocardial oxygen tension and aggravates myocardial oxygen demand/supply balance even after an injection of dental local anesthetic solution at routine doses.

Vasopressin impairs brain, heart and kidney perfusion: an experimental study in pigs after transient myocardial ischemia

Introduction

Arginine vasopressin (AVP) is increasingly used to restore mean arterial pressure (MAP) in low-pressure shock states unresponsive to conventional inotropes. This is potentially deleterious since AVP is also known to reduce cardiac output by increasing vascular resistance. The effects of AVP on blood flow to vital organs and cardiac performance in a circulation altered by cardiac ischemia are still not sufficiently clarified. We hypothesised that restoring MAP by low dose, therapeutic level AVP would reduce vital organ blood flow in a setting of experimental acute left ventricular dysfunction.

Methods

Cardiac output (CO) and arterial blood flow to the brain, heart, kidney and liver were measured in nine pigs using transit-time flow probes. Left ventricular pressure-volume catheter and central arterial and venous catheters were used for haemodynamic recordings and blood sampling. Transient left ventricular ischemia was induced by intermittent left coronary occlusions resulting in a 17% reduction in cardiac output and a drop in MAP from 87 ± 3 to 67 ± 4 mmHg (p < 0.001). A low-dose therapeutic level of AVP (0.005 U/kg/min) was used to restore MAP to pre-ischemic values (93 ± 4 mmHg).

Results

AVP further impaired systemic perfusion (CO and brain, heart and kidney blood flow reduced by 29, 18, 23 and 34%, respectively) due to a 2.0-, 2.2-, 1.9- and 2.1-fold increase in systemic, brain, heart and kidney specific vascular resistances. The hypoperfusion induced by AVP was associated with an increased systemic oxygen extraction. Oxygen saturation in blood drawn from the great cardiac vein fell from 29 ± 1 to 21 ± 3% (p = 0.01). Finally, these effects were reversed 40 min after AVP was withdrawn.

Conclusion

Low dose AVP induced a pronounced reduction in vital organ blood flow in pigs after transient cardiac ischemia. This indicates a potentially deleterious effect of AVP in patients with heart failure or cardiogenic shock due to impaired coronary perfusion.

Cardiovascular effects of felypressin

Cardiovascular effects of felypressin (FEL) were studied in Wistar rats. Heart rate and mean arterial pressure measurements were taken in awake rats treated with vasopressin (AVP), FEL, or epinephrine (EPI). Each group received either an intravenous (IV) or an intracerebroventricular V1 receptor antagonist, saline, area postrema removal, or sham surgery. Analysis of variance and Student-Newman-Keuls (P < .05) were applied. Felypressin and AVP induced a pressor effect, and bradycardia was inhibited by IV V1 antagonist. Intracerebroventricular V1 antagonist and area postrema removal enhanced their pressor effects. Epinephrine induced a higher pressor effect and a similar bradycardia that was not affected by the treatments. It was concluded that FEL depends on V1 receptors to induce pressor and bradycardic effects, and that it produces a high relationship between bradycardia and mean arterial pressure variation depending on area postrema and central V1 receptors. These effects are potentially less harmful to the cardiovascular system than the effects of EPI.