Nitrous Oxide-Induced Cerebral Venous Thrombosis: A Case Report, Potential Mechanisms, and Literature Review

Cerebral venous thrombosis can result from hypercoagulation, either genetic or acquired. Hyperhomocysteninemia was previously thought to be linked with thrombophilia, although this is still controversial to this present day. In recent years, there has been a notable surge in the recreational use of nitrous oxide, which could potentially lead to hyperhomocysteinemia. We present a case of a 19-year-old female who was diagnosed with cerebral venous thrombosis with intracerebral hemorrhage. She had a history of nitrous oxide abuse, which is known to cause dysfunction of vitamin B12. Additionally, we conducted a literature review of cerebral venous thrombosis following nitrous oxide usage. Investigation showed that her serum vitamin B12 level was <100 pg/mL (reference range 197-771 pg/mL), and homocysteine level was 100.6 µmol/L (reference range 5.0-15.0 µmol/L). After receiving a vitamin B12 supplement, both serum vitamin B12 and homocysteine levels returned to normal. No other risk factors for thrombophilia were detected. Previously reported cases predominantly demonstrated hyperhomocysteinemia. The most likely mechanism of her cerebral venous thrombosis was hyperhomocysteinemia due to vitamin B12 deficiency caused by nitrous oxide abuse. This finding supports the hypothesis that hyperhomocysteinemia can induce cerebral venous thrombosis.

Pneumocystis carinii pneumonia in patients without HIV infection

BACKGROUND

Pneumocystis carinii pneumonia (PCP) can occur in immunocompromised patients without HIV infection. Risk factors, clinical features, treatment outcomes, and factors related to mortality in these patients may be useful clinical data for physicians who care for these patients.

METHOD

A retrospective study of PCP patients without HIV infection at Ramathibodi Hospital, from 1994 to 2001, was conducted. Only cases with microbiological and/or pathological proven were included.

RESULTS

There were 19 patients with 42.1 per cent males and a mean age of 44.6 years. All patients had underlying immunocompromised diseases. 94.7 per cent of the cases received immunosuppressive drugs. PCP occurred at a mean duration of 26.4 months after the diagnosis and treatment of underlying diseases. Common clinical presentations of PCP were progressive dyspnea, fever, and non-productive cough. All patients had abnormal chest radiography with a majority of bilateral interstitial infiltration (63.2%). Diagnosis of PCP was confirmed with microbiological examination from bronchoalveolar larvage (84.2%) and pathological diagnosis from transbronchial biopsy (15.8%). Almost all of the cases (94.7%) were treated with co-trimoxazole. Ten patients (52.6%) had concomitant bacterial pneumonia or fungal pneumonitis. Overall mortality rate was 36.8 per cent. Mortality was significantly higher in patients who needed mechanical ventilation (p = 0.006). There was a trend toward a higher mortality rate in patients with concomitant pulmonary diseases (p = 0.09).

CONCLUSIONS

PCP may complicate a variety of immunocompromised states especially autoimmune diseases and hematologic malignancy. Patients who receive corticosteroids and/or cytotoxic drugs should receive primary PCP prophylaxis. The mortality rate is high especially in severe cases that need mechanical ventilation. Intensive care and close monitoring are needed for these patients.

Sleep apnoea syndrome in Ramathibodi Hospital: clinical and polysomnographic baseline data

OBJECTIVE

The aim of this study was to determine clinical and baseline polysomnographic data on obstructive sleep apnoea (OSA) in Thai patients. This prospective study was performed at the Sleep Laboratory Center, Ramathibodi Hospital, Mahidol University, Thailand.

METHODOLOGY

Ninety adult cases clinically suspected of having OSA were studied. The study included clinical, blood chemistry, electrocardiogram, chest radiograph, arterial blood gas, spirometry and full night polysomnography.

RESULTS

Fifty-nine cases (65.6%) out of a total of 90 cases had an abnormal apnoea (i.e. apnoea index (AI) of 5 or more). The incidence of upper airway abnormality among cases with AI of 5 or more was 79.7% (47/59 cases). Among 59 patients with abnormal AI, associated medical problems comprised hypertension (n=22), obesity hypoventilation (n=9), hypothyroidism (n=4), chronic airflow obstruction (n=4), diabetes mellitus (n=3) and chronic renal failure (n=1). Obstructive sleep apnoea was present in all 59 cases. Central apnoea and mixed apnoea were rare.

CONCLUSION

Symptoms and signs suggestive of OSA can lead to a high detection rate and confirmation of OSA by polysomnography. The OSA characteristics of Thai patients were similar to the patients in the Western world.

Instability of ventilatory control in patients with obstructive sleep apnea

Because of the oscillatory pattern of upper airway resistance and breathing during sleep in patients with obstructive sleep apnea (OSA), we hypothesized that OSA patients have an underlying instability of ventilatory drive to inspiratory muscles. To assess the stability of ventilatory drive in OSA patients and controls, we used the pseudorandom binary stimulation (PRBS) test and examined the closed- and open-loop responses to hyperoxic hypercapnia. The closed-loop response is produced by interactions of dynamic gain in controller, plant, and ventilatory feedback. The open-loop response reflects controller dynamic gain or frequency-dependent chemosensitivity. As compared with 16 nonapneic, nonobese control subjects, a group of nine obese OSA patients had a higher peak response and a more rapid and irregular recovery phase of the closed-loop CO2 response in the PRBS test. The two groups had similar open-loop responses in the PRBS test, suggesting that central dynamic CO2 chemosensitivity was not abnormal in OSA. We conclude that the differences between OSA patients and controls in the closed-loop response in the PRBS test are not due to differences in dynamic controller gain, but are related to differences in dynamic plant gain and/or negative ventilatory feedback. In addition to OSA, obesity may affect these variables and may have been responsible for our findings.

Pharmacologic treatment of sleep-disordered breathing

Available literature on the use of pharmacologic agents for the treatment of sleep-disordered breathing was reviewed by evidenced-based methodology. Evidence tables were created and studies were graded according to study design and the number of subjects included. Scores for each group of studies evaluating each pharmacologic agent were established so that the quality of research for different drugs could be compared. The use of various ventilatory stimulants, psychotropic drugs, and antihypertensive agents were reviewed. The most objective data are available on theophylline and opioid antagonist/nicotine groups. Although more controlled studies would be helpful, relatively clear-cut indications for the use of ventilatory stimulants exist for hypercapnic obesity-hypoventilation patients (medroxyprogesterone), myxedema (thyroid replacement), central apnea (acetazolamide), and periodic breathing in congestive heart failure (theophylline). Few randomized, well-controlled trials have been published that evaluate pharmacologic agents in the treatment of classic OSA. To date, no one agent stands out as being useful for OSA. Future research will need to characterize subjects so that various subsets of patients can be tried on one or on a combination of various pharmacologic agents.