Enflurane nephrotoxicity and pre-existing renal dysfunction

Toxicity of inhaled agents after prolonged administration

Inhaled anesthetics have been utilized mostly for general anesthesia in the operating room and oftentimes for sedation and for treatment of refractory status epilepticus and status asthmaticus in the intensive care unit. These contexts in the ICU setting are related to potential for prolonged administration wherein potential organ toxicity is a concern. Over the last decade, several clinical and animal studies of neurotoxicity attributable to inhaled anesthetics have been emerging, particularly in extremes of age. This review overviews potential for and potential mechanisms of neurotoxicity and systemic toxicity of prolonged inhaled anesthesia and clinical scenarios where inhaled anesthesia has been used in order to assess safety of possible prolonged use for sedation. High dose inhaled agents are associated with postoperative cognitive dysfunction (POCD) and other situations. However, thus far no strong indication of problematic neuro or organ toxicity has been demonstrated after prolonged use of low dose volatile anesthesia.

Effect of sevoflurane anesthesia on the severity of renal histopathologic changes in rabbits pretreated with gentamicin: A controlled, investigator-blinded, experimental study

BACKGROUND

Inorganic fluoride and compound A are potential nephrotoxic products of sevoflurane, a halogenated inhalational general-anesthetic drug.

OBJECTIVE

The aim of this study was to microscopically examine the effect of sevoflurane on the severity of renal histopathologic changes in rabbits pretreated with gentamicin.

METHODS

In this controlled, investigator-blinded, experimental study at the Firat University School of Medicine, Elazig, Turkey, male New Zealand white rabbits (age range, 6-8 months; weight range, 2600-3400 g) were randomly divided into 4 groups of equal size. The gentamicin group received IM gentamicin 10 mg/kg · d(-1) for 10 days. Rabbits in the sevoflurane group received pH-balanced saline solution at a volume of 10 mg/kg · d(-1) for 10 days, equivalent to the volume of gentamicin administered to the gentamicin group. On day 11, anesthesia was induced with 8% sevoflurane in 50% oxygen and air using a suitable facemask. When a sufficient depth of anesthesia (loss of eyelash reflex and tolerance to tail-clamp stimuli) was reached (without a muscle relaxant), the rabbits were intubated (3-mm ID) and allowed to breathe spontaneously. End-tidal or end expiratory concentration of sevoflurane was then decreased to 4% and the rabbits were anesthetized at a flow rate of 4 L/min for 4 hours. The rabbits in the gentamicin + sevoflurane group were treated with IM gentamicin at a dosage of 10 mg/kg · d(-1) for 10 days. On day 11, they were exposed to sevoflurane, as described for the sevoflurane group. The control group received IM pH-balanced saline solution for the duration of the study. Twenty-four hours after treatment completion, all rabbits were euthanized and kidney tissue samples were obtained. Histopathologic examinations were then carried out using light microscopy. Changes in renal histopathology were based on the percentage of acute tubular necrosis (ATN) and judged on a scale from none to severe.

RESULTS

Forty male New Zealand white rabbits (mean [SD] age, 7 [0.49] months; mean [SD] weight, 2900 [150] g) were divided into 4 groups of 10 rabbits each. Proximal renal tubule cell injury in the form of ATN (the mean score) was significantly greater in the 3 treatment groups than in the control group (all, P < 0.001), especially at the corticomedullary junction. In the 3 treatment groups, the most severe renal damage observed was rated as mild (10%-25%). More rabbits in the gentamicin + sevoflurane group had mild renal damage (7) than in the gentamicin group (4) or the sevoflurane group (4), but the between-group differences were not statistically significant.

CONCLUSION

In this experimental study of the effects of sevoflurane on the severity of renal histopathologic changes, a higher percentage of rabbits were observed to have greater renal damage in the gentamicin + sevoflurane group than the other groups. However, between-group differences did not reach statistical significance.

Anions and the anaesthetist

Anions are the negative components of most chemical structures and play many important physiological and pharmacological roles that are of interest to the anaesthetist. Their relevance is reviewed with a particular emphasis on the inorganic anions (halides, bicarbonate, phosphate and sulphate) and the significance and limitations of the anion gap. Organic anions (albumin, lactate) are also discussed, albeit briefly. The suitability of anions for their role in neurotransmission and acid-base balance is outlined.

Anaesthesiological complications in renal transplantation: a retrospective study of 500 transplantations

This retrospective study consisted of 500 consecutive renal transplantations performed between September 1977 and September 1981. Preoperatively, congestive heart failure was registered in 262 cases (53.0%) and blood pressure disease in 352 cases (71.3%). The total number of patients with ischaemic heart disease was 22 (4.5%). General anaesthesia was given in 493 and regional anaesthesia in seven cases. In general anaesthesias, tubocurarine was the main relaxant and halothane the main inhalation agent used. Major complications during anaesthesia were blood pressure changes with a higher incidence of hypotension (49.6%) than hypertension (26.8%). Severe cardiac arrhythmias were rare and no intraoperative deaths occurred. One patient was successfully resuscitated in the ICU postoperatively, this being possibly related to hypoventilation caused by prolonged muscular relaxation. Other rare complications included one pneumothorax, one haemo- and hydrothorax, and two large haematomas all caused by preoperative central venous cannulation. In 69 cases (14.0%) additional neostigmine doses and in 34 cases (6.9%) naloxone was given at the end of anaesthesia. Pneumonia during the first postoperative week was recorded in 11 cases (2.2%), and occurred only in patients who received general anaesthesia. One of the three patients who died during the first week developed pneumonia postoperatively.

Anaesthesia and the kidney

Applied anatomy and physiology of the kidney are briefly reviewed. This includes an account of renal blood flow, glomerular filtration rate, juxtaglomerular apparatus, renal autoregulation and intra-renal blood flow distribution, tubular transport mechanisms, solute handling in proximal tubule, function of loop of Henle and distal tubule system. This section concludes with a summary of changes in tubule fluid along the length of the nephron. Acute effects of anaesthesia are reviewed in detail. Indirect effects include those on circulatory and sympathetic nervous systems, autoregulation, endocrine systems such as those involving anti-diuretic hormone, adrenaline and noradrenaline, renin-angiotensin and aldosterone. Direct effects of anaesthesia on renal function have now been confirmed both in vitro and in vivo. Delayed direct nephrotoxicity of anaesthetics relates predominantly to methoxyflurane (MOF) and its metabolism to inorganic fluoride. Other factors are MOF dose, genetics, age, enzyme induction, obesity, other nephrotoxic drugs. Clinical implications are presented. Enflurane nephrotoxicity is rare but aetiologic factors are similar to the foregoing. Isoflurane and halothane are not nephrotoxic. A consideration of the influence of anaesthetic management on the incidence and severity of postoperative acute renal failure concludes the review.

Anaesthesia for renal transplantation--5 years' experience

Two hundred and seventy patients underwent anaesthesia for 280 renal transplants between October 1977 and October 1982. Their medical records were studied retrospectively. These patients were representative of the end-stage chronic renal failure population, with the usual high incidence of cardiovascular and biochemical abnormalities. Most received general anaesthesia, with an intravenous barbiturate, muscle relaxant, narcotic and volatile supplement sequence being the most common. There were no intra-operative deaths. One postoperative death was felt to be influenced by the anaesthetic management. Four patients had life-threatening cardiac complications and a further four required postoperative respiratory support, three for delayed recovery of neuromuscular function and one for "recurarisation". Less serious complications were considerably more common. General anaesthesia utilising suxamethonium and tubocurarine as the relaxants and halothane as the volatile supplement is least likely to result in complications. Changes to this anaesthetic sequence are likely with the introduction of new agents.

Anaesthesia for the patient with impaired renal function

Patients with renal disease are at risk of further deterioration of renal function and acute tubular necrosis when subjected to anaesthesia and surgery. Optimal fluid loading and careful selection of anaesthetic techniques and agents, appropriate monitoring and the use of mannitol and dopamine assist in the maintenance of renal blood flow and help preserve renal function in these patients. In association with renal failure, physiological changes in other systems result in reduced oxygen supply to the tissues, metabolic disturbances, impairment of the coagulation and immune defence mechanisms and an increased risk of cardiac and cerebrovascular catastrophe. Although many anaesthetic techniques including regional analgesia may be used successfully in these patients caution with most drugs, especially pethidine, phenoperidine, suxamethonium and all non-depolarising neuromuscular relaxants is recommended. Of the volatile anaesthetics currently available, halothane is the agent of choice. Oxygen therapy and close monitoring of cardiorespiratory function are necessary postoperatively.

Enflurane anesthesia in living donor renal transplantation

Two groups of patients undergoing elective living donor renal transplantation were studied during enflurane or halothane supplemented anesthesia. The duration of anesthesia was similar in both groups. The mean administered enflurane dose was 243 vol % min; the corresponding halothane dose was 56 vol % min. In the enflurane group, the mean serum inorganic fluoride level peaked at 21.0 mumol/l 3 h after the end of anesthesia. The inorganic fluoride level in urine produced by the renal graft increased continuously, but did not peak, during the first 24 postanesthetic hours. The renal graft quickly started to function in all patients in both groups. The frequency of rejection reactions was higher in the enflurane group than in the halothane group. Serum creatinine levels decreased rapidly in both groups. Urine flow was high on the day of transplantation, but normalized on the first postanesthetic day. Renal sodium clearance decreased earlier in the enflurane group than in the halothane group. This difference was statistically significant on the first postanesthetic day. In the enflurane group, the required pancuronium dose was significantly lower than in the halothane group. In one patient in the enflurane group, the serum inorganic fluoride level increased to 37.5 mumol/l. In this patient renal tubular function may have been affected, but the change was not conclusive since a pronounced rejection of the graft became evident. Since increases in serum inorganic fluoride level approaching 75% of the threshold level for nephrotoxicity in normal kidneys may occur, enflurane should not be routinely used in anesthesia for renal transplantation.

Enflurane in renal transplantation: report of 375 cases

Our experience to date covers 675 kidney grafts performed in the Transplantation Department of the University of Louvain. The evolution of our anaesthesia methods has led us since the end of 1973 to conduct 375 transplantations with enflurane. The patients, aged between 18 months and 50 years, receive a conventional premedication, do not receive corticoids preoperatively nor undergo dialysis immediately prior to operation, but systematically receive a 5-unit transfusion beforehand. Having successively abandoned gallamine, succinylcholine, thiopentone and finally halothane, our present anaesthetic protocol is as follows: induction under benzodiazepines, fentanyl and enflurane, intubation under laryngeal anaesthesia. Maintenance: enflurane (2--3 MAC hours) in open circuit, pancuronium (0.02 mg/kg/h) and occasionally fentanyl. Details and comparative advantages are discussed. This anaesthesia technique combined with the systematic administration of antilymphocytic and antithymocytic serum in the postoperative period, and particularly the preliminary transfusion (producing blocking antibodies), has provided us, using cadaver kidney, with a survival rate of 96% at 6 months, 86% at 1 year and 80% at 2 years, the longest presently being 15 years.

Hepatotoxicity and halothane metabolism in an animal model with application for human toxicity

Centrilobular necrosis and a ten-fold elevation in serum alanine amino-transferase (ALT) consistently followed 2 hours of 1% halothane anaesthesia in an animal model. Conditional factors were the presence of enzyme induction and moderate hypoxia (14% oxygen), indicating an association between reductive metabolism and hepatotoxicity. Under these conditions there was at least a four-fold increase in reductive metabolites detected in the exhaled air. In clinical studies, reductive metabolites were also detected in the exhaled air of all patients examined, even after halothane anaesthesia with 100% oxygen. The amounts of reductive metabolites were comparable in man and the model, following equivalent halothane doses. It appears that a model with a similar route and rate of halothane biotransformation to man has been identified. The lesion of halothane hepatotoxicity in this model appears to be similar to that reported in man - centrilobular hepatic necrosis.