Airborne field hospital in disaster area: lessons from Armenia (1988) and Rwanda (1994)

The outcome of survivors within disaster areas largely depends upon the quick reallocation and operation of logistic and medical support systems. Enthusiastic media equipped with advanced communication systems, reveal mass human suffering in real time. But, the response period required for the organization of rescue systems is much slower and is most frustrating. In this article, we present our experience in quick deployment and operation of airborne field hospitals gained following the earthquake disaster in Armenia in 1988 and the civil war in Rwanda in 1994. Deployment of improvised, volunteer-based, military field hospitals was feasible within 24 hours after the decision was made. A multi-disciplinary structure enabled an effective, flexible mode of operation and reduced the dependency on mericulous, time-consuming assessments of requirements prior to deployment. These missions are a paradigm for the successful incorporation and integration within the capabilities of military infrastructure of volunteer professionals drafted from civil medical facilities. Such field hospitals could provide backup for primary care medical systems in disaster areas and substitute or take some pressure off of local hospitals, particularly when evacuation systems are insufficient.

Meningococcal meningitis among Rwandan refugees: diagnosis, management, and outcome in a field hospital

OBJECTIVE

To study the diagnostic process, clinical course, and outcome of Rwandan refugees with meningococcal meningitis, treated in an Israeli field hospital in Goma, Zaire, in the summer of 1994.

METHODS

Patient hospital charts and laboratory records were reviewed with critical evaluation of clinical presentation and diagnostic tests. Patients were treated as part of a disaster relief effort in a refugee camp experiencing several coexisting lethal epidemics.

RESULTS

A total of 65 patients were identified as having group A meningococcal meningitis. Latex agglutination test for Neisseria meningitidis soluble antigen in the cerebrospinal fluid was found to be a superior diagnostic tool, as compared to Gram stain, and at least as effective as culture. The mortality rate was 14%; mortality was markedly affected by co-morbidity (e.g., dysentery, pneumonia, and malnutrition).

CONCLUSIONS

The outcome of patients with meningococcal meningitis, treated in referral centers within a disaster area may be favorable, despite overwhelming coexisting epidemics, and may be comparable to that achieved in advanced medical facilities. Encephalopathy may be a diagnostic pitfall in the perspective of coexisting epidemics, requiring a high index of suspicion and routine lumbar puncture. The latex agglutination test is highly useful in achieving prompt diagnosis of meningococcal meningitis, in particular when sample handling for culture and microscopy is suboptimal.

Diarrheal epidemics among Rwandan refugees in 1994. Management and outcome in a field hospital

We describe the clinical course and outcome of Rwandan refugees with cholera-like illness (n = 567) and clinical dysentery (n = 1,062) treated at the Israeli Army field hospital in the disaster region of Goma, Zaire, during the summer of 1994. Vigorous fluid administration was the primary therapy, complemented with antibiotics for patients with presumed Shigella infection. Recovery rates were 94% and 96% for patients with cholera and dysentery, respectively. Mortality was substantially affected by comorbid conditions such as pneumonia and meningitis, which occurred in one-quarter of these patients. Infective, metabolic, and surgical complications (including three cases of intussusception) may have contributed to the deaths. The outcome of patients during diarrheal epidemics of cholera or bacillary dysentery may be favorable, even in disaster settings, if patients are evacuated promptly to medical facilities and appropriate therapy is instituted. We close with general observations on procedures to be followed in future epidemics of diarrheal diseases.

Myoglobinuric acute renal failure in the rat: a role for acidosis?

Myoglobin induces renal injury by mechanisms that remain incompletely defined. Acidosis has been suggested as an important factor in myoglobinuric renal failure, and urine alkalization is routinely recommended for its prevention. We tested this hypothesis by exploring the effects of acid-base balance upon myoglobin nephrotoxicity in vivo and in vitro. In isolated rat kidneys at normal pH, myoglobin at concentrations of 25-250 mg/dl minimally affected renal perfusion flow, glomerular filtration rate (GFR) and tubular sodium reabsorption (TRNa). By contrast, at pH 7.1 myoglobin induced vasoconstriction, reduced GFR and TRNa and increased hypoxic injury to medullary thick ascending limbs. These changes were largely reproduced by perfusing kidneys with hematin, suggesting its release from myoglobin in acidosis. Chronic alkalosis or acidosis was induced in rats by supplementing drinking water with 0.28 M NaHCO3 or NH4Cl, respectively. Acute renal failure, produced in control animals by myoglobin infusion (38 mg/100 g body weight), was comparably prevented by both chronic alkalosis and acidosis. Acute intravenous or oral acid load provided similar protection. Thus, although acidosis exacerbates myoglobin toxicity in isolated perfused kidneys, acute or chronic exogenous acid load prevents renal damage in vivo. This may underscore the protective properties of solute load, a consequence of preconditioning, and suggests that, in the crush syndrome, endogenous acidosis rather than being an independent risk factor is a marker of tissue hypoperfusion and organism susceptibility to myoglobin renal toxicity.

The effect of ketotifen on nitric oxide synthase activity

1. We studied the effect of ketotifen, a second generation H1-receptor antagonist on nitric oxide synthase (NOS) activity in colonic mucosa and in renal tissues, and on rat renal haemodynamics in vivo. 2. Ketotifen (100 micrograms ml-1) increased human colonic NOS activity from 3.7 +/- 0.6 to 14.5 +/- 1.3 nmol g-1 min-1 (P < 0.005, ANOVA). In rat renal cortical and medullary tissues ketotifen increased NOS activity by 55% and 86%, respectively (P < 0.001). The stimulation of NOS activity was attenuated by NADPH deletion and by the addition of N omega nitro-L-arginine methyl ester (L-NAME) or aminoguanidine, but not by [Ca2+] deprivation. NOS activity was unaffected by two other H1-antagonists, diphenhydramine and astemizole, or by the structurally related cyproheptadine. Renal cortical NOS activity was also significantly stimulated 90 min after intravenous administration of ketotifen to anaesthetized rats. 3. Ketotifen administration to anaesthetized rats induced modest declines in blood pressure and reduced total renal, cortical and outer medullary vascular resistance. This is in contrast to diphenhydramine, which did not induce renal vasodilatation. 4. We conclude that ketotifen stimulates NOS activity by mechanisms other than H1-receptor antagonism. The association of this effect with therapeutic characteristics of ketotifen and the clinical implications of these findings are yet to be defined.

Renal microcirculation and tissue damage during acute ureteral obstruction in the rat: effect of saline infusion, indomethacin and radiocontrast

Radiocontrast agents and nonsteroidal anti-inflammatory drugs (NSAIDs) are commonly used for the diagnosis and treatment of renal colic. We studied their impact during unilateral acute urinary outflow obstruction upon renal microcirculation and parenchymal integrity. Laser-Doppler and ultrasonic regional flow measurements demonstrated selective decline of outer medullary blood flow by 23 +/- 2% during an acute increase of intra-pelvic pressure to 50 to 55 cm H2O (N = 28, X +/- SEM, P < 0.01). In rats preconditioned with indomethacin, this manipulation reduced medullary blood flow by 50 +/- 4% (N = 16, P < 0.01 vs. obstruction alone), with cortical and total renal blood flow declining by 18 +/- 4% and 16 +/- 2%, respectively (P < 0.01). Unilateral obstruction alone for 24 hours in intact rats resulted in injury (hemorrhage and necrosis) to the papilla and fornix (formed laterally by inner stripe and medially by the inner medulla). These changes were detected as early as 30 minutes after ureteral ligature by staining for fragmented nuclear DNA (TUNEL). Mild damage of thick ascending limbs (mTALs) was associated with substantial medial fornix injury. Indomethacin markedly increased mTAL injury in obstructed kidneys, but attenuated inner medullary damage, both in the medial border of the urinary space and at the papilla. This latter protective effect, probably mediated by the decrease in intrapelvic pressure, was blunted by concomitant intravenous fluid load. Contrast media (iothalamate) and L-NAME (N omega nitro-L-arginine methyl ester) both augmented inner stripe and inner medullary damage in hydronephrotic kidneys. In rats concomitantly subjected to radiocontrast, indomethacin and L-NAME (an acute renal failure protocol, J Clin Invest 94:1069, 1994), unilateral obstruction augmented inner stripe hypoxic damage (65 +/- 6% vs. 24 +/- 11% of mTALs in contralateral kidneys, N = 7, P < 0.01). Injury was maximal at the fornix (93 +/- 6% vs. 39 +/- 14% of mTALs in the mid-inner stripe, P < 0.01) and extended to the outer stripe and medullary rays. Thus, in the rat acute ureteral obstruction alters medullary blood flow and within 24 hours produces medullary damage in both forniceal and inner medullary locations, that is exacerbated by concomitant measures which limit medullary oxygenation. Contrast studies, forced hydration and NSAIDs for renal colic are potentially harmful and their use should be re-evaluated.

Failure of insulin-like growth factor 1 to improve radiocontrast nephropathy

Exogenous insulin-like growth factor 1 (IGF-1) has been reported to improve experimental ischemic acute renal failure. We investigated a possible beneficial role of IGF-1 in a model of radiocontrast nephropathy induced by indomethacin, nitro-L-arginine ester and iothalamate. Multiple injections of recombinant human IGF-1 (or its vehicle) at 150 microg/100 g body weight/day were given for 24 h starting 1 h after radiocontrast, or initiated 1 day after the insults and continued for 48 h. IGF-1 prevented neither the fall in creatinine clearance nor medullary thick ascending limb necrosis observed at 24 h. Similarly IGF-1, given for 2 days after renal failure had been established, did not accelerate functional recovery at 72 h, did not ameliorate catabolism and did not alter the morphological evolution of intrarenal damage. In conclusion, IGF-1 had no beneficial effects in this model of radiocontrast nephropathy.

Myoglobinuric acute renal failure in the rat: a role for medullary hypoperfusion, hypoxia, and tubular obstruction

Myoglobin induces renal injury by mechanisms that remain incompletely defined. In this study, the effects of myoglobin upon renal microcirculation, oxygenation, morphology, and function were investigated in anesthetized rats, and the contribution of coexisting perturbations to myoglobin nephrotoxicity were evaluated. Myoglobin infusion (3.3 mg/min) reduced outer medullary blood flow and Po2, whereas renal blood flow and cortical Po2 were unaffected. Myoglobin infusion (38 mg/100 g weight over 45 min) induced renal failure associated with collecting duct and medullary thick ascending limb dilation and casts, with focal tubular damage, confined mainly to the superficial cortex. Preconditioning with indomethacin, I-N-monomethyl arginine, and theophylline reduced cortical superficial damage but enhanced injury within the inner stripe of the outer medulla and in medullary rays, the zones of lowest O2 supply. In preconditioned animals, tubulorrhexis was primarily observed in collecting ducts transversing the inner stripe, and was remarkably reminiscent of human descriptions (J. Oliver et al., J Clin Invest 1951; 30: 1307-1440). Deterioration in kidney function closely correlated with morphologic features of both tubular obstruction and necrosis. In conclusion, medullary vasoconstriction and intrarenal hypoxia may play a role in myoglobin-induced renal failure. The deterioration in kidney function appears to reflect the combined effects of cortical damage, medullary hypoxic injury, and tubular obstruction.

The role of medullary ischemia in acute renal failure

The introduction of new techniques for the determination of renal parenchymal oxygenation and intrarenal microcirculation has elucidated some important aspects in the pathophysiology of acute renal failure (ARF). Data accumulated over the last decade with these techniques, together with improved morphologic evaluation of the kidney, indicate that medullary damage may play a pivotal role in various forms of acute and chronic renal hypoxic and toxic insults. The outer medulla functions normally under hypoxic conditions, as a result of limited regional oxygen supply and high oxygen consumption for urinary concentration. Outer medullary oxygenation is critically balanced by mechanisms designed to adjust oxygen demand and supply, and their insufficiency may lead to ARF with hypoxic medullary damage. In this article, we outline our current concept of the physiologic control of medullary oxygenation and review the clinical conditions that predispose to hypoxic medullary damage, including rhabdomyolysis, hypercalcemia, or the exposure to endotoxin, nonsteroidal anti-inflammatory drugs, radiologic contrast agents, cyclosporine, FK506, and amphothericin. We shall indicate a possible role for medullary oxygen insufficiency in clinical conditions known to predispose to ARF, such as preexisting renal disease, diabetes mellitus, hypertension, atherosclerosis, effective volume depletion, urinary obstruction, or aging, and suggest potential strategies to preserve medullary oxygenation and integrity.

Dopamine increases renal medullary blood flow without improving regional hypoxia

The effects of dopamine (10 micrograms/kg/min i.v.) upon intrarenal microcirculation, total, superficial cortical and outer medullary blood flows and outer medullary pO2 were continuously determined in anesthetized rats with ultrasonic and laser-Doppler probes and oxygen microelectrodes. While total and cortical flows were unaffected, outer medullary flow increased by 35 +/- 5% (mean +/- SE, p < 0.01). Outer medullary pO2 was not significantly altered (from 16 +/- 4 to 18 +/- 4 mm Hg). In volume-expanded rats total and cortical flows rose as well. In rats pretreated with indomethacin, with or without N omega-nitro-L-arginine methyl ester HCl, dopamine restored renal microcirculation and ameliorated outer medullary hypoxia.

Emphysematous complications in dentistry, 1960-1993: an illustrative case and review of the literature

Seventy-four reports of emphysematous complications in ambulatory dental patients, published in the English literature between the years 1960 and 1993, are reviewed, and an additional case of subcutaneous, retropharyngeal, and mediastinal emphysema following an impression-taking procedure for a crown preparation is presented. This rare complication occurred mainly in patients in the third and fifth decades of life, after dental procedures on the third molar, in particular during mandibular extractions and treatment on the right side. The use of an air syringe, high-speed handpieces, or their combination was reported in 71% of cases. Centripetal air dissection, with retropharyngeal and mediastinal emphysema, occurred in 35% of the patients, especially following extractions.

Determinants of intrarenal oxygenation. II. Hemodynamic effects

To study hemodynamic effects on intrarenal oxygenation, O2 microelectrodes were inserted into rat kidneys. In a previous study [M. Brezis, Y. Agmon, and F. H. Epstein. Am. J. Physiol. 267 (Renal Fluid Electrolyte Physiol. 36): F1059-F1062, 1994], we showed that tubular metabolism is a major determinant of intrarenal oxygenation, in part responsible for medullary hypoxia observed under basal conditions. Acute hypotension (by controlled hemorrhage, aortic ligation, or nitroprusside infusion) paradoxically increased medullary PO2 (from 21 +/- 2 to 39 +/- 2 mmHg, P < 0.001) while decreasing cortical PO2 (from 46 +/- 2 to 32 +/- 3 mmHg, P < 0.001), abolishing corticomedullary gradients of oxygen. Laser-Doppler studies indicated that, while cortical blood flow was reduced during hypotension, medullary blood flow was unchanged or increased. The increase in medullary PO2 induced by hypotension was abolished by prior administration of furosemide, suggesting that during hypotension, reduced glomerular filtration rate (GFR), distal delivery, and reabsorption result in decreased oxygen utilization. Acute infusions of atriopeptin III (0.1-1 microgram.kg-1.min-1) decreased both cortical PO2 (from 61 +/- 2 to 55 +/- 2 mmHg, P < 0.001) and medullary PO2 (from 15 +/- 1 to 7 +/- 1 mmHg, P < 0.001), consistent with atriopeptin-induced increases in GFR and tubular reabsorptive work. These data suggest that medullary oxygen availability increases during renal hypoperfusion and may decrease during renal vasodilation.

Loop diuretics reduce hypoxic damage to proximal tubules of the isolated perfused rat kidney

The straight portion (S3) of the proximal tubule lies in close proximity to the thick ascending limbs (TALs) at the cortico-medullary junction. Since a delicate balance exists between oxygen demand and the limited oxygen supply in this region, we hypothesized that reduction of thick limb metabolic activity might augment oxygen availability to S3 segments, which depend heavily upon aerobic metabolism, and prevent hypoxic damage. The degree of functional deterioration and morphological damage to S3 was assessed in isolated rat kidneys perfused with an erythrocyte-free medium. Bumetanide (10(-5) M) and furosemide (10(-4) M) reduced S3 fragmentation from 9.8 +/- 3.9% of tubules in controls to 0 and 1.4 +/- 0.9%, respectively (P < 0.0005). Tubular glucose reabsorption was better preserved in kidneys exposed to loop diuretics than in control kidneys (P < 0.01), and urinary alkaline phosphatase (P < 0.05) and the total amount of LDH released into the perfusate and urine (P < 0.01) were lower in the treatment groups. Morphological damage to S3 was closely correlated with medullary TAL necrosis (r = 0.66, P < 0.001), urinary alkaline phosphatase excretion (r = 0.89, P < 0.001) and glycosuria (r = 0.83, P < 0.001). We conclude that under hypoxic conditions TALs and S3 segments may compete with each other for a limited oxygen supply. Reduction of active transport in the mTAL might augment oxygen availability to S3 segments and improve their survival.

Effects of salt depletion on the kidney: changes in medullary oxygenation and thick ascending limb size

Previous studies have shown that salt depletion enhances the susceptibility of the kidney to nephrotoxins (amphotericin, cyclosporine, and contrast). To study the renal response to salt depletion, Sprague-Dawley rats were fed a sodium-deficient diet (N = 12) with pair-fed controls (N = 13) for 4 wk. In addition, rats from each group underwent 24-h water deprivation studies (N = 9; four salt deprived, five normal). Plastic 1-micron horizontal sections of mid-inner stripe were examined, and cross-sectional areas of the medullary thick ascending limb (mTAL) were analyzed. The mTAL of the salt-deprived rats were smaller (P = 0.04) and showed greater variance in size (P = 0.02) than control (618 +/- 106 versus 693 +/- 50 microns2). However, mean glomerular and collecting duct cross-sectional areas were unaffected by salt intake. Cross-sectional areas of long- and short-loop mTAL were significantly different, regardless of group (518 +/- 78 versus 732 +/- 92 microns2). Maximal urinary concentrating ability was found to correlate with mTAL cross-sectional area (r = 0.85; P = 0.004) and with long-loop mTAL size (r = 0.77; P = 0.016). However, it did not significantly correlate with short loop mTAL size (r = 0.53; P = 0.14).(ABSTRACT TRUNCATED AT 250 WORDS)

Chronic amphotericin nephropathy: morphometric, electron microscopic, and functional studies

The two major hypotheses for the pathogenesis of amphotericin nephrotoxicity are direct interaction with epithelial cell membranes and vasoconstriction. Studies indicating the special vulnerability of the medullary ray and medulla to hypoxia led to a reexamination of amphotericin nephrotoxicity. Twenty-four rats were divided into four groups: amphotericin injection (5 mg/kg daily for 3 wk), amphotericin plus salt depletion, vehicle, and salt depletion and vehicle. The amphotericin group had polyuria (P < 0.01) but normal serum creatinine. In contrast, amphotericin plus salt depletion rats exhibited renal failure (creatinine of 1.49 +/- 0.05 versus amphotericin alone 0.98 +/- 0.01; P < 0.01). Semiquantitative histologic analysis of cortical and medullary injury correlated with functional impairment. Cortical changes in the amphotericin group were largely restricted to the medullary ray, where focal rupture and calcification of thick ascending limbs were noted. The S2/S3 tubules in the medullary rays showed focally diminished cell complexity with histiocytic/lymphocytic infiltration. However, calcification was also seen in the area of the macula densa. Morphometry revealed that the thick ascending limbs in the medulla were hypertrophied (1,420 +/- 63 versus 1,195 +/- 48 microns 2 for vehicle; P < 0.05). In contrast, in the amphotericin and salt depletion group, the changes in the medullary ray extended to the labyrinth and the thick ascending limbs in the inner stripe showed atrophic changes (772 +/- 23 microns 2; P < 0.01 versus vehicle). Thus, changes as a result of amphotericin toxicity take place both in areas known to be most vulnerable to hypoxia (medullary ray and medulla), and in areas rich in oxygen (adjacent to glomerulus). Salt depletion potentiates the cortical changes and converts medullary hypertrophy to atrophy. These findings support a dual pathogenesis for amphotericin nephropathy (direct toxicity and vasoconstriction).

Glycine reduces early renal parenchymal uptake of cisplatin

We evaluated the effect of glycine infusions on the early renal uptake of cisplatin, measured one hour after cisplatin was injected, as well as five days following cisplatin administration. Glycine (1.25 mmol per 100 g body wt) markedly attenuated the early uptake of platinum by the kidney, an effect not observed with control infusions of saline or of L-alanine. The kidney content of platinum at five days, on the other hand, was similar in glycine-treated animals and saline controls. Early inhibition of renal uptake of platinum may be responsible for glycine's protective action in experimental cisplatin nephrotoxicity.

Effects of ioversol versus iothalamate on endothelin release and radiocontrast nephropathy

RATIONALE AND OBJECTIVES

Certain radiocontrast agents, including iothalamate, iohexol, and ioxaglate, release the renal vasoconstrictor peptide endothelin from vascular endothelium in a way that might contribute to radiocontrast nephropathy. The effects of the nonionic, low osmolar agent, ioversol, on endothelin release and renal function are investigated.

METHODS

Effects of ioversol were compared with equi-iodine doses of iothalamate when applied to cultured bovine aortic endothelial cells or injected into normal rats and rats preconditioned by uninephrectomy, salt depletion, and indomethacin (USIC) to develop radiocontrast nephropathy.

RESULTS

In comparison with iothalamate, ioversol had a greatly reduced propensity to stimulate the release of endothelin, from cultured cells and when injected into anesthetized rats. Ioversol produced less renal vasoconstriction than did iothalamate, in control and in USIC rats, and the development of radiocontrast nephropathy, assessed by creatinine clearance and morphologic damage to the renal medulla, was largely avoided.

CONCLUSIONS

These results strengthen the hypothesis that endothelin release induced by radiocontrast agents is correlated with their renal toxicity and therefore, may play a role in radiocontrast nephropathy.