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Summary and conclusionThe present study has been performed in the Departments of Anesthesia, Pharmacology and Clinical Pathology, Faculty of Medicine, Zagazig University. The aim of the study was a trial to evaluate the effects of sevoflurane anesthesia on renal function, both clinically and experimentally.In the clinical part, 50 adult patients of both sexes class II and III of American Society of Anesthesiologists (ASA) classification with stable renal insufficiency, not receiving hemodialysis with serum creatinine more than 2 mg/dl, these patients were subjecsted to different elective surgical operations, divided into two equal groups (A and B).In group A, anesthesia was induced by thiopentane sodium 5-7 mg/kg and fentanyl 2 ?g/kg. Tracheal intubation was facilitated with intravenous atracurium 0.6 mg/kg. Anesthesia was maintained by sevoflurane 0.5-1% concentration with fresh gas flow (100% oxygen) of 2 L/minute (low-flow sevoflurane anesthesia) with controlled ventilation. Injection of atropine 1 mg with neostigmine 2.5 mg to reverse the curarization effect of atracurium by titration method. The duration of operations in this group was from 1 up to 4 hours.While in group B, the same induction of anesthesia done as group A but, anesthesia was maintained by sevoflurane 1% to 1.5% concentration with fresh gas flow (100% oxygen) of 6-10 L/minute (high-flow sevoflurane anesthesia) with controlled ventilation. Injection of atropine 1 mg with neostigmine 2.5 mg to reverse the curarization effect of atracurium by titration method. The duration of operations in this group was also from 1 up to 4 hours.Preoperative, intraoperative and postoperative comparison of the following variables were done:1- Heart rate, blood pressure (systolic, diastolic and mean) and Electrocardiogram (ECG).2- The recovery characteristics (eye opening, squeeze fingers, spontaneous breathing, extubation, state name, nausea and vomiting) were observed and recorded.3- Blood and urine samples were collected before anesthesia and at days 1, 3 and 5 postoperatively for serum creatinine, blood urea nitrogen, creatinine clearance, serum sodium and potassium, urine osmolality and urine glucose and protein.The results of this part showed that:1- Sevoflurane caused insignificant decrease in heart rate, systolic, diastolic and mean blood pressure and may do prolongation of Q-T interval in ECG intraoperatively mainly in females.2- Recovery after sevoflurane anesthesia was rapid especially with the short duration operations and in patients of group A (low-flow sevoflurane-anesthesia), postoperative nausea and vomiting in 5% from the total patients in both groups occurred.3- There were non-significant changes in serum creatinine, blood urea nitrogen, creatinine clearance and serum sodium and potassium in both groups.4- There were significant changes in urine osmolality, urine glucose and protein in the 1st and 3rd days postoperatively which returned to basal measurements in the 5th day postoperatively.In the pharmacological experimental part, total 120 normal adult albino rats were used as an animal model. This part was divided into two studies:a) Studying the effects of graded concentrations of sevoflurane for variable durations. This study was containing 80 rats divided into 2 groups; each of 40 rats (divided into 3 subgroups; each of 10 rats) and a control group of 10 rats.b) Studying the effects of repeated administration of 2% of sevoflurane after 2 days. This study was containing 40 rats divided into 3 groups and a control group; each group of 10 rats.The parameters studied were:• Time of onset of anesthesia and time of recovery.• Recording of any abnormality.• Biochemical blood analysis for evaluating kidney function by measuring serum creatinine and blood urea nitrogen pre-exposure (control), immediately post-exposure and after 24 hours.• Histopathological study of kidney after 24 hours.The results of this part showed that:1- The onset of anesthesia and the time of recovery were affected by the concentration and the duration of exposure to sevoflurane.2- Labored breathing was noticed with high concentration and long duration.3- Renal toxicity with sevoflurane in rats depending on the concentration of the sevoflurane and the duration of exposure.4- Repeated administration of 2% concentration of sevoflurane after 2 days did not cause any renal changes.In conclusion, administration of sevoflurane both at low-flow and high-flow anesthesia in patients with preexisting renal insufficiency, produced hemodynamic stability without significant renal changes but, it may cause considerable nausea and vomiting that require treatment. While in rats, the sevoflurane has significant renal affection with high concentrations and administration for long durations.The most obvious risk factor for postoperative renal failure in surgical patients is poor preoperative renal function. The present study was performed in patients with preexisting renal insufficiency, which per definition were at a considerable risk for further postoperative deterioration. From both an absence of clinically significant postoperative deterioration of preexisting renal insufficiency and from stable measures of renal function in the postoperative period, we suggest that low-flow sevoflurane anesthesia is as safe as high-flow sevoflurane anesthesia in patients with stable renal insufficiency.RecommendationsSevoflurane has a definite place in the practice of anesthesia. This agent is clearly useful for the induction of general anesthesia in selected pediatric and adult patients. Inspired concentrations of sevoflurane 1 to 8% can be used for induction, with or without premedication, and particular advantages may apply for induction by a single breath technique with this agent. Sevoflurane is a useful agent for the maintenance of anesthesia at concentrations between approximately 1.5% and 3% and it appears safe and convenient to use with or without nitrous oxide as an adjuvant carrying gas. There are some theoretical advantages in an improved ability to avoid transient physiological disturbances between offset of the intravenous induction agent and onset of inhalational anesthesia. Current recommendations suggest maintenance flow rates as low as 2 litres of fresh gas per minute
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