Intramuscular injection of sevoflurane detects malignant hyperthermia predisposition in susceptible pigs

BACKGROUND

The authors hypothesized that intramuscular sevoflurane injection allows diagnostic differentiation between malignant hyperthermia-susceptible (MHS) and -nonsusceptible (MHN) pigs by measurement of intramuscular lactate and carbon dioxide partial pressure (PCO2), and that dantrolene reduces the sevoflurane-induced PCO2 increase.

METHODS

With approval of the local animal care committee, microdialysis probes with attached microtubing for sevoflurane injection were placed in the adductor muscles of nine MHS and six MHN pigs, and PCO2 probes with microtubing were positioned in the triceps muscle of eight MHS and six MHN pigs. After equilibration, sevoflurane boluses at different concentrations and a sevoflurane-dantrolene bolus were injected synchronously. Lactate, pyruvate, and glucose as well as PCO2 were measured spectrophotometrically, and the rate of PCO2 increase was calculated.

RESULTS

Intramuscular sevoflurane injection increased local lactate and PCO2 dose dependently, and significantly higher in MHS than in MHN pigs. Measurement of the rate of PCO2 increase allowed a distinct differentiation between single MHS and MHN pigs. No significant increase in PCO2 was found with sevoflurane and dantrolene.

CONCLUSIONS

Local sevoflurane induces a hypermetabolic reaction measured by PCO2 and lactate increases. The reduced PCO2 increase in MHS after sevoflurane and dantrolene injection is likely to be a result of the sevoflurane-mediated calcium release and its antagonism by dantrolene. Sevoflurane may be useful for a less invasive diagnostic test for malignant hyperthermia in humans.

Prediction of hypertensive crisis based on average, variability and approximate entropy of 24-h ambulatory blood pressure monitoring

Approximate entropy (ApEn) of blood pressure (BP) can be easily measured based on software analysing 24-h ambulatory BP monitoring (ABPM), but the clinical value of this measure is unknown. In a prospective study we investigated whether ApEn of BP predicts, in addition to average and variability of BP, the risk of hypertensive crisis. In 57 patients with known hypertension we measured ApEn, average and variability of systolic and diastolic BP based on 24-h ABPM. Eight of these fifty-seven patients developed hypertensive crisis during follow-up (mean follow-up duration 726 days). In bivariate regression analysis, ApEn of systolic BP (P<0.01), average of systolic BP (P=0.02) and average of diastolic BP (P=0.03) were significant predictors of hypertensive crisis. The incidence rate ratio of hypertensive crisis was 14.0 (95% confidence interval (CI) 1.8, 631.5; P<0.01) for high ApEn of systolic BP as compared to low values. In multivariable regression analysis, ApEn of systolic (P=0.01) and average of diastolic BP (P<0.01) were independent predictors of hypertensive crisis. A combination of these two measures had a positive predictive value of 75%, and a negative predictive value of 91%, respectively. ApEn, combined with other measures of 24-h ABPM, is a potentially powerful predictor of hypertensive crisis. If confirmed in independent samples, these findings have major clinical implications since measures predicting the risk of hypertensive crisis define patients requiring intensive follow-up and intensified therapy.

Thrombotic microangiopathic hemolytic anemia in a patient with SLE: diagnostic difficulties

BACKGROUND

A 19-year-old woman with newly diagnosed systemic lupus erythematosus (SLE) presented with hemolytic anemia, thrombocytopenia, hypertension, tonic-clonic seizures, blurry vision, nephrotic syndrome and renal insufficiency.

INVESTIGATIONS

At a general hospital, the investigations included brain MRI, echocardiography, laboratory tests including measurement of the amount of protein excreted daily, platelet count, levels of lactate dehydrogenase, creatinine and anticardiolipin antibodies, direct Coombs' test, peripheral blood smear, and measurement of blood pressure. At a tertiary institution the investigations included physical examination, electroencephalography, brain MRI, magnetic resonance angiography, repetition of laboratory tests plus measurement of von Willebrand factor-cleaving protease activity, measurement of levels of antibodies to double-stranded DNA and platelets, and renal biopsy.

DIAGNOSIS

Thrombotic microangiopathic hemolytic anemia with a possible underlying diagnosis of malignant hypertension, antiphospholipid antibody syndrome, catastrophic antiphospholipid antibody syndrome, thrombotic thrombocytopenic purpura, or active SLE.

MANAGEMENT

At the general hospital, therapy included a single dose of intravenous cyclophosphamide 500 mg, eight daily plasma exchange treatments, three daily infusions of methylprednisolone 1 g followed by methylprednisolone 60 mg every 8 h, an infusion of rituximab 657 mg and ultrafiltration via hemodialysis. At the tertiary institution, therapy included an infusion of cyclophosphamide 650 mg, aspirin 81 mg daily, prednisone 40 mg daily, mycophenolate mofetil 750 mg twice daily, and aggressive management of hypertension.

Malignant Hypertension Due to Renal Artery Stenosis After Open Partial Nephrectomy in a Solitary Kidney

Laparoscopic and open partial nephrectomy is now routinely performed on small renal masses. Complications of clamping the renal artery during nephron-sparing surgery can include atheroembolic events and dissection of the renal artery. We report a case involving renal artery stenosis after open partial nephrectomy on a solitary kidney.

Hyperperfusion syndromes: insight into the pathophysiology and treatment of hypertensive encephalopathy

Hypertensive encephalopathy is one of the manifestations of a hypertensive crisis. It is not the absolute value of the blood pressure that causes the encephalopathy, rather the presence of an abrupt rise in pressure. In terms of clinical and radiographic findings, there are many similarities among a group of entities, including hypertensive encephalopathy, eclampsia, and immunosuppressant neurotoxicity. Hyperperfusion syndromes may represent these clinical disease states that may share the same pathophysiology. Magnetic resonance imaging fluid attenuated inversion recovery sequences have recognized the prominent cortical involvement of the disease that had been previously missed on computed tomography. Studies have found cortical involvement in 94% of their patients, particularly in mild cases. Animal models demonstrate endothelial damage and enhanced pinocytosis in the cortex as reasons why edema may begin in that region of the brain. Patients diagnosed with hypertensive encephalopathy should be diagnosed and treated promptly in order to avoid further neurological complications. The mean arterial pressure should be lowered by 20% to 25% within the first hour of patient presentation, followed by further gradual reduction in blood pressure over the following 24 hours. Hypertensive emergency in acute ischemic stroke should be managed with more caution. According to the 2003 American Stroke Association treatment guidelines, for patients with ischemic stroke not eligible for thrombolytic therapy, target blood pressures are a diastolic blood pressure <120 mmHg and systolic blood pressure <220 mmHg. The systolic pressure must be <185 mmHg and diastolic pressure <110 mmHg at all times if eligible for thrombolytic therapy.

Thrombotic microangiopathy due to malignant hypertension following corticosteroid therapy for microscopic polyangitis

A 78-year-old woman was treated with 40 mg of prednisolone for microscopic polyangitis, and favorable effects were observed. However, her blood pressure increased and she developed severe thrombocytopenia. Thrombotic microangiopathy (TMA) due to malignant hypertension was suspected and she was treated with an angiotensin-converting enzyme inhibitor; her platelet count then rose. She showed a close temporal relationship between initiation of corticosteroid therapy and the onset of TMA. Corticosteroid therapy should be used with caution in patients with underlying vascular endothelial damage.

Posterior reversible encephalopathy syndrome: a variant of hypertensive encephalopathy

Posterior reversible encephalopathy syndrome (PRES) is a recently described variant of hypertensive encephalopathy characterized by headache, visual disturbances and altered mental function. Its causes are diverse and in contrast to hypertensive encephalopathy, it can develop without significant elevation of blood pressure. This syndrome is mostly reversible when correctly managed; however, failure to recognize it can lead to cerebral infarction and death.

Ophthalmoscopic findings in malignant hypertension

Malignant hypertension may present with retinopathy, choroidopathy, and optic neuropathy. Flame-shaped retinal hemorrhages, an early finding, are due to smooth muscle necrosis and bleeding along the nerve fiber layer. Cotton-wool spots, or cytoid bodies, are not exudates, but rather are retinal infarcts. Hypertensive optic neuropathy is a late finding. Optical coherence tomography is a relatively new imaging technique for evaluating retinal thickness and the location of pathology in patients with malignant hypertension.

Zerebrale Veränderungen bei krisenhafter arterieller Hypertonie: MRT-Befunde der hypertensiven Enzephalopathie sind wegweisend für Diagnose und Therapie

PURPOSE

In the nine years since the posterior reversible (leuc) encephalopathy syndrome (PRES) was first described, a number of causes have been under discussion. These not only include arterial hypertension, i. e. hypertensive crises, but also various toxic substances, i. e. immunosuppressive or chemotherapeutic agents, that are responsible for the formation of the symptoms and characteristic MR tomographic brain findings.

MATERIALS AND METHODS

Initial and follow-up MRI examinations of 8 patients were analyzed. All patients had acute neurological symptoms (headaches, seizures, visual disorders and vigilance disturbances) together with a detectable hypertensive crisis.

RESULTS

MRI disclosed increased signal intensity in subcortical and some cortical lesions in all patient FLAIR sequences. These changes were particularly extensive in the posterior circulation (occipital, cerebellum and brain stem) although they were also detected in brain areas supplied by the carotid artery. However, a cytotoxic genesis of the changes was ruled out in each patient by means of a normal DWI. Furthermore, when the blood pressure was normalized, reversibility of the lesions as proof of the diagnosis was detectable.

CONCLUSION

The imaging findings can be typically analyzed as a predominantly posterior distribution of encephalopathic lesions with a high probability of reversibility after lowering blood pressure was patients suffering from a critical increase in blood pressure with corresponding neurological symptoms. The exact pathophysiology remains unclear, but the cause currently most favored is a vasculopathy of the posterior circulation due to diminished adrenergic autoregulation in combination with a dysfunction of the endothelial cells. In conclusion, we suggest designating this subpopulation from the non-uniform pool of patients with posterior (leuc) encephalopathy as "hypertensive encephalopathy". "Hypertensive encephalopathy" has to be distinguished from "toxic encephalopathy", particularly due to different therapeutic and prognostic consequences.

Infantile polyarteritis nodosa presenting as hyponatraemic hypertensive syndrome

The association of arterial hypertension with hyponatraemic dehydration, known as hyponatraemic hypertensive syndrome (HHS), is a rare and serious hypertensive complication. Here, we describe a 17-mo-old girl who presented with severe hyponatraemic dehydration, hypokalaemia, polyuria, and nephrotic-range proteinuria associated with malignant arterial hypertension and systemic inflammatory disease. Diagnosis of classic polyarteritis nodosa (c-PAN) was made on the basis of renal arteriography demonstrating small arterial aneurysms in association with non-aneurismal changes such as arterial cut-off, arterial tapering stenosis and nephrogram perfusion defect. A decrease of blood pressure by antihypertensive treatment resulted in the normalization of HHS abnormalities. However, c-PAN became well controlled only after 4 mo of immunosuppressive therapy.

CONCLUSION

The main interest of this case was the uncommon presentation of systemic polyarteritis nodosa in a very young child. Renal ischaemia from intrarenal vessel disease may have been the trigger event for HHS in our case. Management of PAN-associated severe arterial hypertension is based on immunosuppressive and antihypertensive treatment.

Hypertensive crisis: hypertensive emergencies and urgencies

Hypertensive crisis is a serious condition that is associated with end-organ damage or may result in end-organ damage if left untreated. Causes of acute rises in blood pressure include medications,noncompliance, and poorly controlled chronic hypertension. Treatment of a hypertensive crisis should be tailored to each individual based on the extent of end-organ injury and comorbid conditions. Prompt and rapid reduction of blood pressure under continuous surveillance is essential in patients who have acute end-organ damage.

[Clinical reasoning and decision making in practice. A 39-year-old woman with somnolence, hypertension and haemolysis]

A 39-year-old woman was admitted with somnolence, severe hypertension and thrombotic microangiopathy. Both malignant hypertension and thrombotic thrombocytopenic purpura (TTP) were considered. Immediate therapy was instituted to treat both diseases because of severe clinical deterioration. Eventually, TTP was considered less likely due to the presence of grade IV hypertensive retinopathy (papilloedema and soft exudates) and a normal Von Willebrand factor-cleaving protease level. Differentiating TTP from malignant hypertension can be difficult as both diseases have similar clinical, laboratory and radiological features. In both diseases, hypertension, thrombotic microangiopathy and encephalopathy with white-matter lesions in the posterior regions of the brain may be apparent. Funduscopic abnormalities consistent with grade III and IV hypertensive retinopathy are rare in TTP, as are normal levels ofVon Willebrand factor-cleaving protease. Therefore, the diagnosis TTP was considered less likely and plasmapheresis was stopped. Hereafter, the laboratory values pointing towards haemolysis remained normal with adequate blood pressure control supporting the rejection of TTP as the cause of the symptoms.

[Hypertensive encephalopathy: differential diagnosis of brain edema with midline shift]

Hypertensive encephalopathy is a severe complication of hypertensive crisis or malignant hypertonia. We report a case with grave clinical and radiological features. The patient was comatose, with pupillary dysfunction, and initial CT suggested a local intracranial mass with edema. Cranial MRI showed almost completely hyperintensive supratentorial white matter, with edema and midline shift, and hypertensities in cerebellum and brainstem. The patient recovered, and the radiological findings improved after antihypertensive therapy. Hypertensive encephalopathy may be differentiated by MRI, manifests acutely, and is potentially reversible when adequate therapy is rapidly performed.

Malignant hypertension secondary to cortisol-secreting adrenal tumour

Adrenal cortical tumour-induced malignant hypertension is rare, except for some documented aldosterone-producing adenomas. Hypertension is a common feature of Cushing's syndrome, whereas malignant hypertension is rarely seen. This case in Taiwan is only the second reported case with malignant hypertension secondary to a cortisol-secreting adrenal tumour. The immunohistochemical study of the excised tumour showed strong positive staining of interleukin (IL)-6. IL-6 can trigger inflammatory vascular damage, which is typical in the malignant phase of hypertension. We hypothesise that IL-6 may have played an important role in this case.