Transtracheal oxygen therapy: an effective and safe alternative to nasal oxygen administration.

Transtracheal oxygen therapy (TTOT) improves the efficiency of oxygen delivery and overcomes the discomfort associated with nasal oxygen delivery in patients on long-term oxygen therapy (LTOT). In addition, TTOT improves compliance and quality of life, and may reduce morbidity. Experience with TTOT in Europe is, however, scarce and the safety of TTOT has not yet been completely determined. These were reasons for testing the acceptance, efficacy and safety of TTOT. Patients were selected on the basis of the accepted indications and contraindications for TTOT. In 75 patients (48 males and 27 females) the mean follow-up time was 16 (range 0.5-51.5) months. Compared to nasal cannulae, TTOT caused a reduction in the oxygen flow rate of 47 (33-60)% at rest and a significant increase in the number of hours that oxygen was used. All patients on TTOT used oxygen for at least 20 h x day(-1). Most patients saw the procedure as a minor intervention. It was usually performed on an out-patient basis. In 34 patients, 51 mainly minor complications were seen, and most of these occurred in the first 10 patients. After precautions had been taken, complications occurred less frequently. No patient needed to be hospitalized because of a complication. TTOT had to be stopped in two patients; nevertheless, all patients preferred TTOT to the nasal cannulae. We conclude that transtracheal oxygen therapy is an effective and safe alternative to nasal oxygen administration, provided that it is restricted to a well-defined group of patients and applied by a motivated and experienced group of physicians.

Long-term oxygen therapy.

This review discusses the different aspects of long-term oxygen therapy (LTOT). In selected patients with chronic hypoxaemia, LTOT may increase the life-span and quality of life. Since identification of these patients is both important and difficult, the indications for LTOT are discussed. Next, the appropriate time at which LTOT should be initiated is discussed in the section on the physiological criteria. Even in patients who qualify for LTOT, the effectiveness of this therapy may vary. Because they are important in this context, the prescription guidelines are considered. Finally, possible ways of increasing the efficiency of LTOT are reviewed in the sections on home oxygen systems, oxygen-conserving methods and the organization of LTOT in the Netherlands.

Can technetium 99m bisdiethylphosphinoethanebis-t butylisocyanide (99mTc-DEPIC) be used for routine radionuclide ventriculography?

Radionuclide ventriculography is a useful investigation in the evaluation of cardiac function. Generally, in vivo technetium 99m-labelled red blood cells (RBC) yield good quality images in ventriculography. However, it is widely believed that some drugs have an adverse effect on RBC labelling. Zanelli et al. (1987) developed a radiopharmaceutical (technetium 99m bis-diethylphosphinoethanebis-t-butylisocyanide, 99mTc-DEPIC) to obtain better results in patients using such drugs. We undertook a prospective study of 6 patients with cardiovascular and/or pulmonary disease using several kinds of drugs to evaluate imaging of the cardiac blood pool with 99mTc-DEPIC and in vivo labelled 99mTc-RBC. After injection, blood samples were taken, and gated equilibrium blood pool studies were performed. The radiochemical purity of the injected 99mTc-DEPIC varied from 76.4 to 93.6% (mean 86.4%, SD 5.7%). The protein (pre-albumin) binding was 100%. Biological half-life in blood varied from 3.3 to 4.7 h (mean 4.1 h, SD 0.5 h). For 99mTc-RBC no significant blood disappearance was seen for 8 h. The percentage of RBC-bound 99mTc varied from 96.9% to 98.3% (mean 97.0%, SD 0.5%) and was stable for at least 8 h. The heart-to-lung, heart-to-spleen, and heart-to-liver ratios were higher for 99mTc-RBC than for 99mTc-DEPIC. Furthermore, 99mTc-DEPIC showed a significant decline of the ejection fraction with time. Visually, the images with 99mTc-RBC were superior to those with 99mTc-DEPIC, especially a few hours after injection. According to our findings, in vivo labelling of 99mTc-RBC is still the method of choice for routine radionuclide ventriculography.(ABSTRACT TRUNCATED AT 250 WORDS)

Pharmacokinetics of cefepime in patients with respiratory tract infections.

The steady-state pharmacokinetics of cefepime were evaluated in 10 middle-aged and elderly patients with acute lower respiratory tract infections who were receiving 1 g intravenously every 12 h. One preinfusion and 15 postinfusion serum samples and total urine output were collected over one dosing interval between days 3 and 8 of therapy. Cefepime concentrations in serum over time exhibited a multicompartmental profile. Peak and trough concentrations in serum determined by a validated high-performance liquid chromatography method were 71.2 +/- 17.2 (mean +/- standard deviation) and 6.0 +/- 4.9 mg/liter, respectively. The steady-state volume of distribution was 0.22 +/- 0.05 liter/kg. Elimination half-lives ranged from 1.93 to 6.04 h (3.92 +/- 1.28 h), and total body clearances ranged from 36.9 to 102 ml/min per 1.73 m2 (73.0 +/- 19.7 ml/min per 1.73 m2). The disposition of cefepime at steady state in patients was comparable to previous observations in healthy elderly volunteers. The predictive performance of regression equations derived from single-dose studies in volunteers relating creatinine clearance with total body and renal clearances of cefepime exhibited slight biases (mean predictive errors, -9.7 and 2.1 ml/min per 1.73 m2, respectively) and similar precisions. Predicted and observed total body clearances (63.3 +/- 25.1 versus 73.0 +/- 19.7 ml/min per 1.73 m2, respectively) and renal clearances (51.3 +/- 24.4 versus 49.3 +/- 19.6 ml/min per 1.73 m2, respectively) were not significantly different. The pharmacokinetics of cefepime in infected patients appeared to be unaltered by illness, and the steady-state disposition of cefepime was predictable from data derived from single-dose studies in volunteers.

Bronchospasmolytic effects of salbutamol as powder inhalation in patients with reversible bronchial obstruction.

In a double-blind double-dummy crossover study, the effects of salbutamol dry powder inhaled from Salbutamol cyclocaps Pharbita 0.4 mg with the Pharbita inhaler and from a reference product were compared. On the first trial day, a single dose of one of the two preparations was administered, and 2 days later a single dose of the another preparation was administered, in random order. The effects on lung function (FEV1) were monitored from 15 to 360 min after administration. For both products the increase in FEV1 with reference to baseline values was statistically highly significant. There was no significant difference between the products.

Decrease of plasma potassium due to inhalation of beta-2-agonists: absence of an additional effect of intravenous theophylline.

The effect on the plasma potassium concentration of inhalation of the beta-2-agonists fenoterol, salbutamol (albuterol), and terbutaline from metered-dose inhalers was studied in normal volunteers. All three drugs caused a significant, dose-dependent decrease, more pronounced for fenoterol and salbutamol than for terbutaline. Relative to the bronchodilating potency (one puff of fenoterol 0.2 mg is considered to be equivalent to two puffs of salbutamol 2 x 0.1 mg, or two puffs of terbutaline 2 x 0.25 mg), fenoterol had a more pronounced effect on plasma potassium than salbutamol or terbutaline. The systemic effect on plasma potassium seems to be related to the structure of the drugs: the more lipophilic the drug (fenoterol) the sooner the systemic symptoms appear and the more pronounced they are. The effects of theophylline alone, and combined with fenoterol, were also studied. The intravenous infusion of theophylline (after placebo inhalation; maximal mean plasma concentration 14.9 +/- 2.2 mg l-1) caused a small but significant decrease of plasma potassium. There was no additive or synergistic effect when theophylline was added to fenoterol. It is concluded that inhalation of beta-agonists induces a decrease of plasma potassium, that this effect is relatively more pronounced for fenoterol than either salbutamol or terbutaline, and that it is not enhanced by the concomitant use of theophylline. Theophylline by itself causes a slight decrease in plasma potassium concentration.

Hypokalaemia induced by inhalation of fenoterol.

The effect of inhalation of fenoterol, a beta 2-agonist, on plasma potassium was studied in four groups of four healthy young subjects. Group I received 3 times 2 puffs (0.2 mg fenoterol/puff), group II 3 times 3 puffs, and group III 3 times 4 puffs. Group IV received 3 times 4 puffs of a placebo, according to the group III schedule. The puffs were given at 30-min intervals. Plasma potassium levels decreased significantly in subjects who received fenoterol: the decrease was 0.4 +/- 0.3 (SD) mmol/l in group I, 0.5 +/- 0.2 mmol/l in group II and 0.9 +/- 0.1 mmol/l in group III. In the placebo group plasma potassium levels were unchanged. Inhalation of beta 2-agonists may be dangerous, especially in patients under stress--eg, during an acute asthmatic attack, when the plasma potassium concentration would already be subnormal as the result of raised circulating adrenaline levels.