Low Infusion Pressure Research Articles

Comment on: Vitreous-lens interface changes after cataract surgery using active fluidics and active sentry with high and low infusion pressure settings.

Comment on: Vitreous-lens interface changes after cataract surgery using active fluidics and active sentry with high and low infusion pressure settings.

Hysteroscopic removal of intrauterine device in early pregnancy

BackgroundIntrauterine devices (IUDs) are commonly used as contraceptives worldwide. However, pregnancies in patients carrying this kind of device may occur. IUD removal when the woman wishes to continue their pregnancy may be very challenging. Only 9 manuscripts in literature reported such similar procedure.Case presentationWe report the case of an hysteroscopic removal of IUD in a young woman at 6 weeks of gestation.DiscussionThe case reported highlights safety and efficacy of operative hysteroscopy as a method of IUD removal in early pregnancy, although other different methods have been reported in literature. In our opinion, maintaining a low infusion pressure during the procedure may help avoiding potential gestational sac damage and IUD displacement for better grasping.

Does low infusion pressure microincision cataract surgery (LIPMICS) reduce frequency of post-occlusion breaks?

Objective: To compare the number of surge events and efficacy of phacoemulsification using a near-physiological intraocular pressure (IOP) setting and a standard IOP setting. Materials and methods: The surgical data of patients who underwent phacoemulsification with IOL implantation using the CENTURION Vision System’s Active Fluidics setting and Active Sentry Handpiece (Alcon Laboratories, USA) were analyzed. Results: The study included 181 patients (204 eyes). In Group 1, the IOP was set at 20 mmHg (n=102, 50%), and in Group 2, the IOP was set at 60 mmHg (n=102, 50%). Total case time was significantly lower (p=.036) in Group 1 (0:03:17.20 ± 0:00:34.55 vs. 0:03:28.71 ± 0:00:43.03). There was no statistically significant difference between the mean cumulative dissipated energy (CDE) (7.06 ± 3.20 vs. 7.59 ± 3.26) and mean ultrasound (UJS) time (0:00:36 ± 0:00:12 vs. 0:00:38 ± 0:00:13) between the two groups (p=0.24 and p=0.31, respectively). Active sentry (AS) engaged less often (p<0.001) in Group 1. There was no statistically significant correlation between the CDE and AS activation in Group 1 (p=0.96). A strong statistically significant correlation between the CDE and AS activation (p<0.0001, r=0.61, CI (0.47 to 0.72)) was observed in group 2. Conclusion: During phacoemulsification, surge events are more likely to occur when operating at high IOP settings.Abbreviations: LIPMICS = low infusion pressure microincision cataract surgery, IOP = intraocular pressure, CDE = cumulative dissipated energy, UJS = mean ultrasound time, AS = Active sentry, LOCS = Lens Opacities Classification System, NO = nuclear opalescence, AFR = aspiration flow rate

Release and extraction of retained subfoveal perfluorocarbon liquid facilitated by subretinal BSS, vibration, and gravity: a case report

BackgroundPerfluorocarbon liquid (PFCL) is an effective surgical adjuvant in performing vitrectomy for severe vitreoretinal pathologies such as proliferative vitreoretinopathy and giant retinal tears. However, subretinal retention of PFCL can occur postoperatively and retained PFCL causes severe visual disorders, particularly when PFCL was retained under the fovea. Although several procedures have been proposed for subfoveal PFCL removal, such as direct aspiration or submacular injection of balanced salt solution (BSS) to dislodge the subfoveal PFCL, the retinal damage associated with these procedures has been a major problem. Here, we report a case of subfoveal retention of PFCL for which we performed a novel surgical technique that attempts to minimize retinal damage.Case presentationA 69-year-old man presented with subfoveal retained PFCL after surgery for retinal detachment. To remove the retained PFCL, the internal limiting membrane overlying the subretinal injection site is first peeled to allow low-pressure (8 psi) transretinal BSS infusion, using a 41-gauge cannula, to slowly detach the macula. A small drainage retinotomy is created with the diathermy tip at the inferior position of the macular bleb, sized to be slightly wider than that of the PFCL droplet. The head of the bed is then raised, and the surgeon gently vibrates the patient’s head to release the PFCL droplet to allow it to migrate inferiorly towards the drainage retinotomy. The bed is returned to the horizontal position, and the PFCL, now on the retinal surface, can be aspirated. The subfoveal PFCL is removed while minimizing iatrogenic foveal and macular damage. One month after PFCL removal, the foveal structure showed partial recovery on optical coherence tomography, and BCVA improved to 20/40.ConclusionCreating a macular bleb with low infusion pressure and using vibrational forces and gravity to migrate the PFCL towards a retinotomy can be considered as a relatively atraumatic technique to remove subfoveal retained PFCL.

Hypercholesterolemic Mice Exhibit Lymphatic Vessel Dysfunction and Degeneration

Lymphatic vessels are essential for lipid absorption and transport. Despite increasing numbers of observations linking lymphatic vessels and lipids, little research has been devoted to address how dysregulation of lipid balance in the blood, ie, dyslipidemia, may affect the functional biology of lymphatic vessels. Here, we show that hypercholesterolemia occurring in apolipoprotein E-deficient (apoE(-/-)) mice is associated with tissue swelling, lymphatic leakiness, and decreased lymphatic transport of fluid and dendritic cells from tissue. Lymphatic dysfunction results in part from profound structural abnormalities in the lymphatic vasculature: namely, initial lymphatic vessels were greatly enlarged, and collecting vessels developed notably decreased smooth muscle cell coverage and changes in the distribution of lymphatic vessel endothelial hyaluronic acid receptor-1 (LYVE-1). Our results provide evidence that hypercholesterolemia in adult apoE(-/-) mice is associated with a degeneration of lymphatic vessels that leads to decreased lymphatic drainage and provides an explanation for why dendritic cell migration and, thus, immune priming, are compromised in hypercholesterolemic mice.

Sensory neuron targeting by self-complementary AAV8 via lumbar puncture for chronic pain

Lumbar puncture (LP) is an attractive route to deliver drugs to the nervous system because it is a safe bedside procedure. Its use for gene therapy has been complicated by poor vector performance and failure to target neurons. Here we report highly effective gene transfer to the primary sensory neurons of the dorsal root ganglia (DRGs) with self-complementary recombinant adeno-associated virus serotype 8 (sc-rAAV8) modeling an LP. Transgene expression was selective for these neurons outlining their cell bodies in the DRGs and their axons projecting into the spinal cord. Immunohistochemical studies demonstrated transduction of cells positive for the nociceptive neuron marker vanilloid receptor subtype 1, the small peptidergic neuron markers substance P and calcitonin gene-related peptide, and the nonpeptidergic neuron marker griffonia simplicifolia isolectin B4. We tested the efficacy of the approach in a rat model of chronic neuropathic pain. A single administration of sc-rAAV8 expressing the analgesic gene prepro-beta-endorphin (ppbetaEP) led to significant (P < 0.0001) reversal of mechanical allodynia for >/=3 months. The antiallodynic effect could be reversed by the mu-opioid antagonist naloxone 4 months after gene transfer (P < 0.001). Testing of an alternative nonopioid analgesic gene, IL-10, alone or in combination with ppbetaEP was equally effective (P < 0.0001). All aspects of the procedure, such as the use of an atraumatic injection technique, isotonic diluent, a low-infusion pressure, and a small injection volume, are consistent with clinical practice of intrathecal drug use. Therefore, gene transfer by LP may be suitable for developing gene therapy-based treatments for chronic pain.

High infusion pressure in conjunction with vitreous surgery alters the morphology and function of the retina of rabbits

To investigate the effects of high infusion pressure in conjunction with pars plana vitrectomy (PPV) on retinal morphology and function in rabbits. Pars plana vitrectomy was performed under urethane (0.8 mg/kg) anaesthesia in the right eye of albino rabbits following phacoemulsification and aspiration (PEA). The left eyes were not touched. After PEA, the animals were divided into two groups. In six eyes, intraocular pressure (IOP) was increased to 80 mmHg for 30 mins (high-pressure group) and in five eyes IOP was maintained at 40 mmHg for 30 mins (low-pressure group). The IOPs were regulated by the height of the bottle of balanced salt solution (BSS) and monitored with a pressure transducer. After the pressure elevation, vitreous fluid was collected to measure the glutamate concentration. Then, PPV was performed for 15 mins in both groups under an infusion pressure of 40 mmHg. In five additional rabbits, PEA alone was performed in the right eye, and vitreous fluid was collected (PEA group). Functional alterations were assessed by recording visual evoked potentials (VEPs) and electroretinograms (ERGs). Ten days after the IOP changes, the animals were killed with intravenous pentobarbital sodium and the eyes were prepared for histological analysis. Damage to retinal ganglion cells (RGCs) was quantified by counting the number of cells in the ganglion cell layer (GCL). The contralateral eyes in the high-pressure group served as controls (n = 6). The mean implicit time (IT) of the VEPs in the high-pressure group was significantly longer than that before the IOP elevation, by 114-124% (p < 0.05, paired t-test), and also than that of control eyes (p < 0.05, anova followed by t-test). No significant changes in the VEPs were detected in either the low-pressure group or the PEA group. There were significantly fewer cells in the GCL in the high-pressure group (24.7/mm) than in the control animals (41.4/mm; p < 0.05, Dunnett's test). The number of cells in the GCL in the low-pressure and PEA groups did not significantly differ to that in the controls. The amplitudes of the ERG a- and b-waves were not significantly changed (p > 0.05, paired t-test). These results suggest that high infusion pressure in conjunction with PPV leads to morphological and functional changes in the retina. The absence of ERG changes and presence of VEP changes suggest that these changes were due to damage to RGCs, which supports the morphological observations.

The importance of cardioplegic infusion pressure in neonatal myocardial protection

Background. Cardioplegia infusion pressure is usually not directly monitored during neonatal heart operations. We hypothesize that the immature newborn heart may be damaged by even moderate elevation of cardioplegic infusion pressure, which in the absence of direct aortic monitoring may occur without the surgeon’s knowledge. Methods. Twenty neonatal piglets received cardiopulmonary bypass and the heart was protected for 70 minutes with multidose blood cardioplegia infused at an aortic root pressure of 30 to 50 mm Hg (low pressure) or 80 to 100 mm Hg (high pressure). Group 1 (n = 5, low pressure), and group 2 (n = 5, high pressure) were uninjured (nonhypoxic) hearts. Group 3 (n = 5, low pressure) and group 4 (n = 5, high pressure) first underwent 60 minutes of ventilator hypoxia (Fi o 2 8% to 10%) before initiating cardiopulmonary bypass to produce a clinically relevant hypoxic stress before cardiac arrest. Function was assessed using pressure volume loops (expressed as a percentage of control), and coronary vascular resistance was measured with each cardioplegic infusion. Results. In nonhypoxic (uninjured) hearts (groups 1 and 2) cardioplegic infusion pressure did not significantly affect systolic function (end systolic elastance, 104% versus 96%), preload recruitable stroke work (102% versus 96%) diastolic compliance (152% versus 156%), or coronary vascular resistance but did raise myocardial water (78.9% versus 80.1%; p < 0.01). Conversely, if the cardioplegic solution was infused at even a slightly higher pressure in hypoxic hearts (group 4), there was deterioration of systolic function (end systolic elastance, 28% versus 106%) ( p < 0.001) and preload recruitable stroke work (31% versus 103%; p < 0.001), rise in diastolic stiffness (274% versus 153%; p < 0.001), greater myocardial edema (80.5% versus 79.6%), and marked increase in coronary vascular resistance ( p < 0.001) compared to hypoxic hearts given cardioplegia at low infusion pressures (group 3), which preserved function. Conclusions. Hypoxic neonatal hearts are very sensitive to cardioplegic infusion pressures, such that even moderate elevations cause significant damage resulting in myocardial depression and vascular dysfunction. This damage is avoided by using low infusion pressures. Because small differences in infusion pressure may be difficult to determine without a direct aortic measurement, we believe it is imperative that surgeons directly monitor cardioplegia infusion pressure, especially in cyanotic patients.

Fibrin Glue Vasal Anastomosis Compared To Conventional Sutured Vasovasostomy in the Rat

Vasectomy reversal has become a frequently performed surgical procedure with best results obtained with the use of the operating microscope and microsurgical technique. The present study was undertaken to evaluate the use of fibrin glue (“Tisseel”, Immuno U.S., Inc.) for vasovasostomy and to compare this technique to conventional sutured vasovasostomy. Utilizing 60 male Sprague Dawley rats, a conventional two layered sutured anastomosis of vasovasostomy (30 rats) was compared to a fibrin glue technique of vasal anastomosis (30 rats). The fibrin glue technique was performed with two transmural sutures, was unstented, and utilized the biological glue to seal the anastomosis. The contralateral vas of each animal underwent vasectomy and reapproximation of unligated ends so that the rate of spontaneous recanalization could be accessed. Rats were sacrificed at 24 hours, one week, four weeks, and three months postvasovasostomy. The vasal specimens were evaluated for gross patency, presence and size of sperm granuloma, mean flow rates at varying infusion pressures, tensile strength measurements and histologic studies. Combining the one and three month groups, a similar patency rate was obtained by either technique; 83% (n = 18) for the sutured group, and 90% (n = 21) for the fibrin glue group. The rate of spontaneous recanalization of the contralateral vasa in the one and three month animals was 8% (n = 38). The mean flow rates obtained at high and low infusion pressures were not statistically different for the two techniques. The tensile strength of the glue anastomosis averaged 78% of the tensile strength achieved by the conventional sutured technique. The incidence of sperm granuloma after vasovasostomy was 28% for the fibrin glue group and 61% for the sutured group. Additionally, 67% of granulomas were small (<3mm.) in the glue group, compared to only 36% in the sutured group. Histology revealed similar morphological changes in the area of anastomosis with either technique. Operative time for sutured vasovasostomy averaged 24 minutes, compared to an average of 11 minutes for the glue assisted vasovasostomy.The use of fibrin glue allowed the performance of a sperm tight patent anastomosis that had the advantages of reduced incidence of sperm granuloma formation, reduced operative time, and less microsurgical skill required to perform the anastomosis.

Absorption of 1.5% Glycine after Percutaneous Ultrasonic Lithotripsy for Renal Stone Disease

An elderly normotensive man underwent percutaneous ultra? sonic lithotripsy for renal stone disease, the procedure lasting three hours and the fragments being washed out with 20 1 1-5% glycine. After two hours the inflation pressure had risen to 25 cm H20 and his blood pressure to 150 mm Hg. Inflation pressure continued to rise until drainage tubes were inserted into the retroperitoneal space, releasing a large volume of fluid, some of which appeared to be from the peritoneal cavity. Shortly after transfer to the recovery area the patient showed signs of the transurethral resection syndrome, with hyponatraemia, hyper kalaemia, and hypertension. He was treated appropriately and survived. Low infusion pressures should be used for irrigation during lithotripsy and 0-9% saline instead of 1-5% glycine. In patients given a general anaesthetic any rise in inflation pressure suggests extravasation of fluid and warrants emergency estimation of the plasma sodium concentration.

Pancreatic ductal mucosa as a protective barrier in the pathogenesis of pancreatitis

The pancreatic ducts are lined by mucus-secreting epithelial cells. At low infusion pressures this lining shows remarkable resistance to normal bile, activated pancreatic enzymes, and bacteria. Infected bile has proved to be the most potent factor in this series of experiments in breaching this barrier. The earliest changes in the ductal wall are difficult to assess by using only the routine histologic technics. In these experiments attempts were made to find new ways of studying the anatomic and functional integrity of the ductal wall. The nature and mode of action of bile “altered” by the E. coli organisms is still open to speculation.