Do iatrogenic serosal injuries result in small bowel perforation in a rabbit model?

BACKGROUND

Surgical dogma dictates that serosal injuries should be repaired during laparotomy as these injuries may result in localised areas of bowel ischaemia and may perforate. No study has investigated whether there is a correlation between the extent of serosal injuries and the risk for perforation under normal physiological conditions. We hypothesized that small bowel serosal injuries do not result in early or late perforation at physiological intraluminal pressures regardless of their size.

METHOD

An in-vivo rabbit small bowel serosal injury model was developed and two experiments were conducted. The first - to determine whether and at which pressures various lengths and circumferences of serosal injuries in small bowel result in immediate bowel perforation - was performed infusing saline into isolated bowel segments with or without a variety of serosal injuries. In the second study - to determine whether or not serosal injuries result in delayed perforation - a range of injuries was created in rabbits and the effect assessed at re-laparotomy 5 days after the creation of the injury.

RESULTS

No perforations were observed at the site of serosal injuries at physiological intraluminal pressures. Perforations occurred at 43.7+ 18.6 cmH₂O, 23.3+ 14.4 cmH₂O, and 24.4+ 23.9 cmH₂O for controls, 4 cm long and 100% circumference serosal injuries respectively (p-value = 0.18 for various lengths and 0.71 for various circumferences). No serosal injuries perforated within 72 or 120 hours after creation.

CONCLUSION

Small bowel serosal injuries do not perforate or leak at physiological intraluminal pressures, either at the time of creation or up to 120 hours thereafter.

The giraffe kidney tolerates high arterial blood pressure by high renal interstitial pressure and low glomerular filtration rate

BACKGROUND

The tallest animal on earth, the giraffe (Giraffa camelopardalis) is endowed with a mean arterial blood pressure (MAP) twice that of other mammals. The kidneys reside at heart level and show no sign of hypertension-related damage. We hypothesized that a species-specific evolutionary adaption in the giraffe kidney allows normal for size renal haemodynamics and glomerular filtration rate (GFR) despite a MAP double that of other mammals.

METHODS

Fourteen anaesthetized giraffes were instrumented with vascular and bladder catheters to measure glomerular filtration rate (GFR) and effective renal plasma flow (ERPF). Renal interstitial hydrostatic pressure (RIHP) was assessed by inserting a needle into the medullary parenchyma. Doppler ultrasound measurements provided renal artery resistive index (RI). Hormone concentrations as well as biomechanical, structural and histological characteristics of vascular and renal tissues were determined.

RESULTS

GFR averaged 342 ± 99 mL min(-1) and ERPF 1252 ± 305 mL min(-1) . RIHP varied between 45 and 140 mmHg. Renal pelvic pressure was 39 ± 2 mmHg and renal venous pressure 32 ± 4 mmHg. A valve-like structure at the junction of the renal and vena cava generated a pressure drop of 12 ± 2 mmHg. RI was 0.27. The renal capsule was durable with a calculated burst pressure of 600 mmHg. Plasma renin and AngII were 2.6 ± 0.5 mIU L(-1) and 9.1 ± 1.5 pg mL(-1) respectively.

CONCLUSION

In giraffes, GFR, ERPF and RI appear much lower than expected based on body mass. A strong renal capsule supports a RIHP, which is >10-fold that of other mammals effectively reducing the net filtration pressure and protecting against the high MAP.

Cryptococcal pneumonia in African miners at autopsy

SETTING

Deceased miners from South Africa whose cardiorespiratory organs were submitted for autopsy for compensation for occupational lung diseases from 1996 to 2000.

OBJECTIVES

To 1) calculate the prevalence of cryptococcal pneumonia in 8421 autopsied miners, a population with a high prevalence of human immunodeficiency virus (HIV) infection; 2) document the association of cryptococcal pneumonia with other pulmonary infection; 3) document the association of cryptococcal pneumonia with a clinical diagnosis of cryptococcal meningitis; and 4) determine the accuracy of the clinical diagnosis of cryptococcal pneumonia.

DESIGN

Case series of 589 black miners with histological evidence of cryptococcal pneumonia at autopsy, defined as the presence of cryptococcal organisms in the lung parenchyma, identified by staining of the mucinous capsule.

RESULTS

The incidence of cryptococcal pneumonia at autopsy was 7%. Ninety-seven of the 589 cases (16.5%) had a concomitant respiratory infection, most commonly Pneumocystis jirovecii pneumonia (51.5%), followed by mycobacterial infection (42.3%). In life, cryptococcal meningitis was diagnosed in 46.9% and cryptococcal pneumonia in only 2.7%.

CONCLUSION

Although tuberculosis remains the most common HIV-associated respiratory disease in Africa, it is important to consider the diagnosis of cryptococcal pneumonia in acquired immune-deficiency syndrome (AIDS) patients, and to bear in mind the possibility of dual pathology.

Pneumocystis jirovecii pneumonia in African miners at autopsy

SETTING

Deceased miners from South Africa whose cardio-respiratory organs were submitted for autopsy for compensation for occupational lung diseases from 1996 to 2000.

OBJECTIVES

1) To document the incidence of Pneumocystis jirovecii pneumonia (PJP) in autopsied miners; 2) to compare the incidence of PJP over a 5-year period; 3) to record the incidence of concomitant lower respiratory tract infection in a group of PJP-infected deceased miners coming to autopsy from 1996 to 2000; and 4) to describe the accuracy of the in-life diagnosis of PJP in this group.

DESIGN

Case series of 328 deceased Black miners with histological evidence of PJP at autopsy.

RESULTS

Of the 328 miners with PJP at autopsy, 107 (32.6%) had a concomitant respiratory infection, the most common being cryptococcal pneumonia (46.7%), followed by bacterial pneumonia (34.6%) and pulmonary tuberculosis (13.1%). Overall, Pneumocystis pneumonia was unsuspected prior to death in 89% of cases; however, diagnostic accuracy in life improved from 7% in 1996 to 21% in 2000.

CONCLUSION

The high rate of undiagnosed PJP is cause for concern. Clinicians should have a heightened awareness for PJP in Africa, particularly as the disease is treatable at low cost and effective prophylaxis is available.

Beneficial effects of pentoxifylline in patients with idiopathic dilated cardiomyopathy treated with angiotensin-converting enzyme inhibitors and carvedilol: results of a randomized study

BACKGROUND

We previously reported beneficial effects of pentoxifylline, a xanthine-derived agent known to inhibit the production of tumor necrosis factor-alpha, in patients with idiopathic dilated cardiomyopathy treated with diuretics, digoxin, and ACE inhibitors. Since then, 3 large clinical trials showed important clinical benefits of beta-blockers in this population. Therefore, we designed the present study to establish whether in patients with heart failure already receiving treatment with ACE inhibitors and beta-blockers, the addition of pentoxifylline would have an additive beneficial effect.

METHODS AND RESULTS

In a single-center, prospective, double-blind, randomized, placebo-controlled study, 39 patients with idiopathic dilated cardiomyopathy were randomized to pentoxifylline 400 mg TID (n=20) or placebo (n=19) if they had a left ventricular ejection fraction <40% after 3 months of therapy with digoxin, ACE inhibitors, and carvedilol. Primary end points were New York Heart Association functional class, exercise tolerance, and left ventricular function. Patients were followed up for 6 months. Five patients died (3 in the placebo group). Patients treated with pentoxifylline had a significant improvement in functional class compared with the placebo group (P:=0.01), with an increment in exercise time from 9.5+/-5 to 12.3+/-6 minutes (P:=0.1). Left ventricular ejection fraction improved from 24+/-9% to 31+/-13%, P:=0.03, in the treatment group.

CONCLUSIONS

In patients with idiopathic dilated cardiomyopathy, the addition of pentoxifylline to treatment with digoxin, ACE inhibitors, and carvedilol is associated with a significant improvement in symptoms and left ventricular function.

Peripartum cardiomyopathy: analysis of clinical outcome, left ventricular function, plasma levels of cytokines and Fas/APO-1

OBJECTIVES

1) To evaluate the outcome of patients with peripartum cardiomyopathy (PPC) on current treatment for heart failure, 2) to assess the circulating plasma levels of cytokines and Fas receptors and 3) to identify predictors of prognosis.

BACKGROUND

Previous studies in patients with PPC were done when angiotensin-converting enzyme (ACE) inhibitors and beta-adrenergic blocking agents were not routinely used in heart failure. Inflammatory cytokines play an important role in the pathogenesis and progression of heart failure of other etiologies. However, there is a paucity of data regarding cytokine expression in patients with PPC. Plasma concentrations of Fas receptors (an apoptosis-signalling receptor) have not been reported in this population.

METHODS

We followed prospectively 29 consecutive black women with PPC. All patients were treated with diuretics, digoxin, enalapril and carvedilol. Echocardiograms were performed at baseline and after six months of treatment. Cytokine and soluble Fas/APO-1 plasma levels were measured at baseline.

RESULTS

Tumor necrosis factor-alpha, interleukin-6 and Fas/APO-1 levels were significantly elevated in the study patients compared with 20 healthy volunteers. Eight patients died. sFas/APO-1 levels were significantly higher in patients who died compared with survivors (8.98 +/- 4.5 vs. 5.33 +/- 3 U/ml, respectively, p = 0.02). At six months, ejection fraction improved from 26.7 +/- 10 to 42.7 +/- 16%, p = 0.00003, with an increment of more than 10 U in 10 patients (28.1 +/- 4 to 51.9 +/- 8%, p = 0.000008).

CONCLUSIONS

Cytokine and sFas levels are elevated in patients with PPC. Despite treatment with ACE inhibitors and beta-blockers, mortality remains high. However, in 34% of the patients, left ventricular function almost completely normalized.

Association analysis of beta2 adrenoceptor polymorphisms with hypertension in a Black African population

OBJECTIVE

To determine whether or not beta2 adrenoceptor polymorphism is a risk factor for the development of hypertension in a Black South African population.

BACKGROUND

Attenuated vasodilator responses to endogenous catecholamines may contribute to the aetiology of hypertension. Downregulation of beta2 adrenoreceptors (beta2AR) following stimulation with agonists is determined in part by variation at the beta2AR gene locus. The Glu27 beta2AR genotype results in attenuated downregulation compared with the wild-type Gln27 receptor, whereas Gly16 exhibits enhanced down-regulation compared to Arg16. Possible racial differences in the prevalence of the beta2AR polymorphisms may be an explanation for the blunted responses to isoprenaline and the increased prevalence of hypertension in Black African populations.

METHODS

One hundred and ninety-two unrelated hypertensives and 123 normotensives of Black South African origin were studied. Hypertensives were recruited from hospital hypertension clinics in the province of Gauteng and if on treatment, had a 2-4 week washout period before 24-h ambulatory blood pressure assessment Normotensive controls were recruited from the same community.

RESULTS

There was no significant association between either the Arg-Gly16 polymorphism or the Gln-Glu27 polymorphism and hypertension status. Furthermore, in the hypertensives, no significant association was seen between beta2AR genotype at either site and clinical blood pressure, 24-h blood pressure or left ventricular mass. A significant association was seen between Arg16 homozygotes and lower body mass index in hypertensives (P = 0.007) although this was not a primary end point. Interestingly, the Glu27 polymorphism was much rarer in this population (allelic frequency 17%) compared to a Caucasian population.

CONCLUSION

These data suggest that beta2AR polymorphism is not a risk factor for hypertension per se in this defined population. The possibility that the decreased prevalence of Glu27 in black South African populations explains blunted vasodilator responses to isoprenaline requires further study.

Antihypertensive monotherapy with nisoldipine CC is superior to enalapril in black patients with severe hypertension

A single-center, prospective double-blind randomized trial was conducted to compare the efficacy and safety of the calcium channel blocker nisoldipine in a sustained release coat-core formulation (CC), titrated from 10 mg to 40 mg daily, with the angiotensin converting enzyme inhibitor enalapril, titrated from 10 to 40 mg daily, in the treatment of black South African patients with severe hypertension (sitting diastolic blood pressure [DBP] between 115 and 140 mm Hg, confirmed by 24-h ambulatory blood pressure monitoring). Treatment target was a sitting DBP < 95 mm Hg by the 9th week of treatment. This was followed by a 4-month open phase using nisoldipine CC 10 to 60 mg daily. Ninety-six patients had complete data at baseline, and at the end of the double-blind and open phases, and were included in this analysis. In both groups, all patients required titration up to the maximal dose of double-blind medication. Monotherapy with nisoldipine CC, but not enalapril, significantly reduced both sitting and 24-h ambulatory blood pressure (BP). Twenty-four-hour BP in the nisoldipine CC group decreased from 179+/-14 / 118+/-7 to 144+/-16 / 94+/-10 mm Hg (P < .0001) versus 181+/-13 / 117+/-5 to 171+/-17 / 110+/-11 mm Hg in the enalapril group (P = ns). The profound decrease in blood pressure achieved with nisoldipine CC was accompanied by a significant reduction in left ventricular [LV] mass index, observed after only 2 months of treatment (from 146+/-40 to 129+/-35 g/m2, P = .05). In contrast, enalapril had no effect on LV mass (from 139+/-36 to 142+/-50 g/m2, P = NS). The antihypertensive effect of nisoldipine CC was further demonstrated in the open phase, during which 24-h BP decreased from 180+/-14 / 118+/-6 mm Hg (at baseline) to 142+/-16 / 92+/-10 mm Hg at the end of the 16-week open phase (P < .0001). This effect was sustained with trough-to-peak ratio of 74% for systolic and 67% for diastolic BP, with further regression in LV mass. Reduction in 24-h systolic BP to < 135 mm Hg was associated with a greater degree of regression of LV mass index in patients treated with nisoldipine CC. The incidence of adverse events in both groups was low and both nisoldipine CC and enalapril were well tolerated. The incidence of significant ventricular arrhythmia was also low and did not change with treatment. In conclusion, our findings suggest that nisoldipine CC administered once daily could be considered as a suitable first-line antihypertensive agent in black patients with severe hypertension, based on its profound and sustained blood-pressure-lowering effect, associated with significant regression of left ventricular mass and its low side effect profile.

Randomised investigation of effects of pentoxifylline on left-ventricular performance in idiopathic dilated cardiomyopathy

BACKGROUND

There is accumulating evidence that inflammatory cytokines have an important role in the pathogenesis of heart failure. Plasma concentrations of tumour necrosis factor alpha (TNF-alpha) are high in heart failure and have been correlated with the severity of symptoms. Pentoxifylline suppresses the production of TNF-alpha. This study aimed to assess the effects of pentoxifylline on left-ventricular function and functional class in patients with idiopathic dilated cardiomyopathy.

METHODS

We undertook a single-centre, prospective, double-blind, randomised, placebo-controlled trial, in which 28 patients with idiopathic dilated cardiomyopathy were assigned pentoxifylline 400 mg three times daily or matching placebo. Clinical, echocardiographic, and radionuclide assessments were done at baseline and after 6 months of treatment. Primary endpoints were New York Heart Association (NYHA) functional class and left-ventricular function.

FINDINGS

Baseline characteristics were similar in the two groups. Four patients died during the study period, all in the placebo group. After 6 months of treatment, the proportion of patients in NYHA functional class I or II was higher in the pentoxifylline group than in the placebo group (14/14 vs 10/14; p=0.01), and ejection fraction was higher in the pentoxifylline group than in the placebo group (mean 38.7% [SD 15.0] vs 26.8% [11.0], p=0.04). At 6 months, TNF-alpha plasma concentrations were significantly lower in the pentoxifylline-treated group than in the placebo group (2.1 [1.0] vs 6.5 [5.0] pg/mL, p=0.001).

INTERPRETATION

Our results suggest that pentoxifylline improves symptoms and left-ventricular systolic function in patients with idiopathic dilated cardiomyopathy. These results must be confirmed in larger-scale trials.

Aminoguanidine prevents the decreased myocardial compliance produced by streptozotocin-induced diabetes mellitus in rats

BACKGROUND

A decreased cardiac compliance is a major feature of the cardiomyopathy of diabetes mellitus. Either an increase in the resistance afterload to the LV or an increase in collagen cross-linking induced by the formation of advanced glycosylation end products (AGEs) of collagen may be responsible for the stiff myocardium. To evaluate these hypotheses, we examined the effect of captopril, an afterload-reducing agent, and aminoguanidine, a nucleophilic hydrazine that prevents the accumulation of collagen AGEs, on left ventricular end-diastolic (LVED) compliance after 4 months of streptozotocin (0.26 mmol/kg)-induced diabetes mellitus in rats.

METHODS AND RESULTS

Diabetes mellitus produced a decrease in LV chamber compliance as a result of an increased myocardial stiffness (slope of the linearized LVED stress-LVED strain relation [unitless]: diabetes mellitus, 47+/-4; control, 27+/-3; P<.001) and an increase in blood pressure as a result of an elevated vascular resistance. LV end-systolic elastance was unaltered by diabetes mellitus. The stiff myocardium was not associated with changes in the myocardial collagen volume fraction or total hydroxyproline concentration but was associated with an increased myocardial collagen fluorescence (fluorescence units/microg hydroxyproline) (diabetes mellitus, 11+/-1.1; control, 6.6+/-0.7; P<.01). Captopril therapy (0.22 mmol x kg(-1) x d(-1)), despite producing a decrease in blood pressure through alterations in vascular resistance, failed to decrease myocardial stiffness in rats with diabetes mellitus. Alternatively, administration of aminoguanidine (7.35 mmol x kg(-1) x d(-1)) prevented both the enhanced myocardial collagen fluorescence (7.1+/-1.2) and the increased slope of the linearized LVED stress-LVED strain relation (29+/-2) but did not change markers of blood glucose control.

CONCLUSIONS

These results demonstrate that diabetes mellitus can produce a stiff myocardium before the development of myocardial fibrosis. The stiff myocardium in the early stages of the development of the cardiomyopathy of diabetes mellitus is not a consequence of an increase in ventricular resistance afterload and in these circumstances is associated with the formation of collagen AGEs.