Factors influencing corneal predescemetic endothelial keratoplasty (PDEK) graft creation: It's all in a bubble.

AIM: To assess the effect of pneumatic (air) and fluidic (transport medium) injection to the type of bubble (I, II or mixed III) and the resultant dissection of corneal endothelial grafts PDEK or DMEK. MATERIALS AND METHODS: All grafts were obtained from Dr Agrawal Hospital's Eye Bank. Air injection was the initial preferred mode of graft harvest. If pneumatic dissection was unsuccessful after 10 tries, fluidic dissection with transport medium was tried. SPSS 23.0 was used to statistically analyse the data. RESULTS: 40 consecutive donor corneas with a mean age of 46.5 and a mean endothelial count of 2980 were analysed. Air dissection lead to the harvest of 27 endothelial grafts and fluid dissection led to the creation of 7 endothelial grafts. Statistically significant difference was found the different bubble types and the type of injection (χ2 chi square=10.02, 0=0.008). CONCLUSION: In young donors pneumatic (air) graft dissection leads to PDEK in a high proportion. This percentage is reduced when transport medium is tried after unsuccessful air injection. Injection of transport medium increases the percentage of grafts harvested but also increases the ratio of Type II and III DMEK grafts created.

Iohexol does not influence the levels of blood serum cation electrolytes during intravenous pyelography.

PURPOSE: The influence of the nonionic contrast agent iohexol on blood pH and the cation electrolytes Ca, Na, K and Mg was studied in vivo in humans during the intravenous pyelography. MATERIAL AND METHODS: A population of 28 patients without renal function impairment or electrolyte imbalance was divided into two equal groups. The first group received an intravenous injection of 0.6 mL Omnipaque per kg of body weight (0.388g iohexol/kg and 0.18 g iodine/kg). The second group received a double dose of Omnipaque (1.2 mL iohexol/kg; 0.776g iohexol/kg and 0.36g iodine/kg). Blood samples (5 mL) were taken before the injection of the contrast medium and 5, 10 and 20 minutes (marking the end of the examination) after the injection. Blood pH was also determined immediately after each sample collection, while electrolytes were measured in the laboratory. Systolic and diastolic blood pressure were also determined simultaneously with each sample collection using a mercury manometer. RESULTS: Iohexol in simple and double doses did not have any statistically significant effect either on blood pH or on blood serum electrolytes during intravenous pyelography. Blood pressure, both systolic and diastolic, remained stable in all the patients during the examination. CONCLUSIONS: Our results show that the nonionic contrast medium iohexol at the doses used in routine intravenous pyelography does not have any influence on blood pH and serum cardioactive cation electrolytes in humans. An electrolyte imbalance is always a risk factor that may contribute to the development of cardiovascular side effects. This factor is eliminated when iohexol is administered intravenously instead of an ionic agent.

Effects in vivo of iohexol and diatrizoate on human plasma acetyl- and butyryl-cholinesterase activity.

PURPOSE: The aim of this study was to evaluate the effects of two iodinate contrast agents (CA), iohexol and diatrizoate, on human plasma acetyl-(AC) and butyrylcholinesterase(BC) activity. MATERIAL AND METHODS: Forty-eight patients (24 males and 24 females) scheduled for intravenous pyelography were randomly divided into four groups of 6 males and 6 females each, receiving as CA, respectively: iohexol (Omnipaque, Schering) 0.6 ml/kg body weight (G1); iohexol 1.2 mg/kg (G2); sodium and meglumine diatrizoate 58% (Urografin, Schering) 0.6 ml/kg (G3); sodium and meglumine diatrizoate 58% 1.2 ml/kg (G4). Blood samples were taken before and 5, 10, and 20 min after the injection. Enzymatic activity of AC and BC were measured by spectrophotometry. Plasma concentration of K, Na, Ca, and Mg was measured in all blood samples; blood pressure and plasma pH were measured after each sample collection. Statistical analysis was performed by Student's test. RESULTS: In G1 a reversible decrease of AC (12.9%) and BC (8.2%) plasma activity was observed at 10 min. In G2 a progressive decrease of AC (13.9%) and BC (18.4%) plasma activity was observed with a maximum at 20 min. In G3 a modest reversible decrease of BC plasma activity (5.4%) was observed. In G4 a modest progressive decrease of AC (7.3%) and BC (6.5%) plasma activities was observed. In all cases, AC and BC plasma activities remained within the normal range of values. Plasma concentration of K, Na, Ca, and Mg, as well as pH and systolic and diastolic pressure, did not show any change. No adverse effects was observed in our patients. CONCLUSIONS: Iohexol and diatrizoate induce in vivo a significant decrease of AC and BC plasma activities. The decrease is more pronounced for iohexol, a non ionic CA, which has a lower pharmacotoxicity than diatrizoate and adverse effects rate. No inference can be drawn about the relationship between plasma cholinesterase activity and adverse effects.

Comparison of felodipine and nitroglycerin actions on vasomotion physiology.

Felodipine is a Calcium blocker and nitroglycerin, a nitrate vasodilating agent, were compared. Two parameters were studied in vitro on bovine aortic media. Calcium uptake and vascular tone. The Calcium uptake measurement was performed by incubating in Krebs solution small slices of the preparation in the presence of 45Ca. Studies on vascular tone were performed on deendothelialized bovine aortic rings suspended in Krebs solution. Felodipine (1nM-100microM) decreases Ca2+ uptake and relaxes the preparation while nitroglycerin's 1nM-100microM) action is also inhibiting but very weak. When the preparation is stimulated by alpha 1-adrenergic against phenylephrine 1microM, then nitroglycerin 100microM has a much stronger inhibiting effect on Call uptake and vascular tone than felodipine 100microM. These results are reversed when the preparation is stimulated by KC165.4mM. Then felodipine 100nM exerts a strong inhibiting effect on Ca2+ uptake and vascular tone while nitroglycerin's 100nM inhibiting action is very weak. It is well known that in cases of endothelium disfunction the adrenergic stimulation provokes vasoconstriction and ischemia. This ischemia induces a second phase of vasoconstriction that is due to a depolarization provoked by the increased levels of extracellular K+. Felodipine is able to antagonize the consequences of such a depolarization. Thus, felodipine may be useful as an additional agent to nitroglycerin's treatment and that is the clinical message of our findings.

The effect of some iodinated contrast media on human plasma butyrylcholinesterase activity.

The effect of three iodinated contrast media (CM) on human plasma butyrylcholinesterase (BuChE) activity was studied during the intravenous pyelography (i.v.P). BuChE is an enzyme that participates in the metabolism of acetylcholine and hydrolyzes food esters and drugs such as nondepolarizing muscle relaxants and local anesthetics. The three CM were: diatrizoate (an ionic substance) and iohexol and iopentol (two nonionic substances). Five minutes after the intravenous injection, iohexol reduces BuChE plasma activity by 8.5% but this effect disappears within 15 minutes. Diatrizoate and iopentol decrease BuChE plasma activity by 8% and 15.2%, respectively, 5 minutes after the injection and this effect remains stable for the next 15 minutes. The underlying mechanism is unknown. Plasma BuChE activity remains within the normal range in any case and no association with side effects can be made. Thus, according to the above findings, it is not possible to connect or exclude any relationship between BuChE plasma activity and CM-derived adverse reactions during the i.v.P.

Interaction of aminoglycoside antibiotics and calcium channel blockers at the neuromuscular junctions.

Aminoglycoside antibiotics (mmol.l-1) gentamicin (0.74), streptomycin (1.02), netilmicin (1.24), amikacin (2.23), sisomicin (2.74), dactimicin (2.75), kanamycin (3.43), kanendomycin (3.45), tobramycin (3.53) and dibekacin (4.35) produce a complete neuromuscular blockade at the isolated phrenic nerve-hemidiaphragm preparation of the rat, which is only reversed by calcium chloride. On the other hand, verapamil (2.04 mmol.l-1), a calcium channel blocker, also produces a complete neuromuscular blockade at the above preparation which is reversed by calcium chloride. Aminoglycoside antibiotics are potentially capable of interacting with verapamil and produce a complete neuromuscular blockade at concentrations significantly reduced. The neuromuscular blockade which is produced by the concurrent administration of the aminoglycoside antibiotics and verapamil is obtained with the usual therapeutic blood concentrations of the individual agents. Furthermore, the neuromuscular blockade which is produced during verapamil-aminoglycoside antibiotics interactions is completely reversed after calcium chloride administration. The mechanism by which aminoglycoside antibiotics and verapamil produce neuromuscular blockade must be the same. Both classes of drugs interfere with calcium ions movements through the calcium channels of the membrane of the motor nerve-endings inhibiting acetylcholine release at the synaptic cleft. The interaction of aminoglycoside antibiotics and calcium channel blockers is of clinical significance because when these agents are given concurrently during the perioperative period they may lead to respiratory depression or prolonged apnoea. These respiratory disturbances can be managed by slow intravenous infusion of 50 to 200 mg of calcium gluconate.