Richard W. Light

Pulmonary function after coronary artery bypass surgery

Coronary artery bypass graft surgery (CABG) adversely affects pulmonary function tests (PFTs). Although several previous studies have addressed these changes, none has measured the forced vital capacity (FVC) on a daily basis. The purpose of the present study was to assess serial changes in the FVC following CABG and to identify factors that may influence these changes. The FVC was obtained pre- and daily postoperatively (1-10 days) in 120 patients. Fifty-one patients received saphenous vein grafts (SVG group) while 69 received at least one internal mammary artery graft in addition to SVG (IMA group). On the first postoperative day, the FVC decreased to 33% of the pre-operative value in the SVG group and to 29% in the IMA group. The spirometry gradually improved, but after 10 days, the FVC remained reduced (SVG, 70%; IMA, 60%). Although the decreases in FVC tended to be greater in the IMA group, there was no significant difference in the two groups (P = 0.27). The changes in FVC were not significantly related to age (P = 0.48), smoking history (P = 0.65), anesthesia (P = 0.38) or pump time (0.09). From this study, it is concluded that after CABG, there is a significant worsening of the pulmonary function. The nadir of FVC occurs immediately after surgery and improves gradually thereafter. However, on the tenth postoperative day, the FVC still remains more than 30% below pre-operative values. Since there is only a slight tendency for patients undergoing IMA grafting to have larger decreases in their pulmonary function, patients with ventilatory impairment should not be excluded from IMA grafting.

Effects of diuresis on the characteristics of pleural fluid in patients with congestive heart failure

PURPOSEnThe pleural fluid that accumulates secondary to congestive heart failure is almost always a transudate based upon its level of protein and lactic acid dehydrogenase (LDH). Previous work has suggested that the characteristics of the fluid may change into those of an exudate with diuresis. The purpose of the present study was to determine whether aggressive diuresis does result in this change in pleural fluid characteristics.nnnPATIENTS AND METHODSnTwelve patients with severe congestive heart failure (ejection fraction 23.9 +/- 9.6%) and pleural effusions were studied serially as they underwent diuresis. After an initial thoracentesis was performed, the patients then underwent aggressive diuresis for 12 to 48 hours with one or two follow-up thoracentesis.nnnRESULTSnThe mean weight loss during the study period was 4.5 +/- 2.8 kg. With diuresis the LDH level, LDH ratio, protein level, and protein ratio all increased significantly (p less than 0.05). All 12 patients had transudative pleural effusions at the onset of diuresis. However, despite the increases in the levels of protein and LDH with diuresis, only one patients pleural fluid attained values compatible with an exudate.nnnCONCLUSIONnFrom this study we conclude that it is uncommon for a transudative pleural effusion due to congestive heart failure to develop the characteristics of an exudative pleural effusion with rapid diuresis.

Effect of desipramine on control of ventilation and depression scores in patients with severe chronic obstructive pulmonary disease

Decreased ventilatory responses to carbon dioxide (CO2) correlate with elevated scores on tests for depression in normal subjects and with episodes of endogenous depression in psychiatric patients. Patients with severe chronic obstructive pulmonary disease (COPD) frequently develop resting hypercapnia due to impaired ventilatory mechanics or drive, and may also have elevated scores on tests for depression. Tricyclic antidepressant drugs can improve ventilatory mechanics and possibly drive. We hypothesized that antidepressant drugs might enhance ventilatory drive and improve arterial blood gases in patients with severe COPD and that these improvements might correlate with improvement in depression scores. Therefore, we studied the effects of desipramine versus placebo on spirometry, resting arterial blood gases, hypercapnic ventilatory and mouth occlusion pressure responses, and scores on the Beck and Zung self-rated depression scales. In our patients the resting arterial CO2 (PaCO2) was found to depend almost equally on ventilatory mechanics and drive. In addition, patients with higher depression scores tended to have a lower PaCO2 when the severity of airways obstruction was taken into consideration. In a 16-week, double-blind, crossover comparison of desipramine with placebo, both treatments led to significant improvement in depression scores. Desipramine had no effects on resting PaCO2, spirometry, or ventilatory control.

Effectiveness of sodium hydroxide as a pleural sclerosing agent in rabbits: Influence of concomitant intrapleural lidocaine

The two agents that have been used most commonly to produce a pleurodesis are tetracycline and bleomycin. Tetracycline is no longer generally available because of more stringent requirements on the manufacturing process. Bleomycin is very expensive. Therefore, alternative agents are necessary particularly in developing countries. The objective of this project was to determine whether 0.5% sodium hydroxide is an effective sclerosant in an experimental model in rabbits. Sodium hydroxide (NaOH) (2 ml of 0.5%) was instilled intrapleurally in 24 anesthetized male rabbits. Half the rabbits received 1 ml of 2% lidocaine 3–5 min before the NaOH. Twenty-eight days after the instillation, the animals were sacrificed, and the pleural spaces were assessed grossly for evidence of pleurodesis and microscopically for evidence of fibrosis and inflammation. The results indicated that the intrapleural injection of NaOH was effective in creating a pleurodesis only if the animals were not premedicated with lidocaine. The mean (±S.D.) degree of gross pleurodesis after NaOH alone 2.8 (1.0) was significantly (p < 0.001) greater than after that following the combination 1.3 (0.5). We conclude that NaOH is an effective pleural sclerosant but that it is ineffective if it is injected concomitantly with lidocaine.

Comparison of mitoxantrone and tetracycline as pleural sclerosing agents in rabbits

Bleomycin is the antineoplastic agent used most commonly for the treatment of malignant pleural effusion. It is absorbed rapidly from the pleural space and does not elicit pleurodesis in the normal rabbit pleura. Mitoxantrone is a new antineoplastic that differs from bleomycin in that it binds to membranes. Accordingly it might remain in the pleural space for a longer period and produce a pleurodesis. The objective of this project was to determine whether mitoxantrone is an effective sclerosant in an experimental model in rabbits. The following medications were instilled intrapleurally in anesthetized male rabbits: 35 mg/kg tetracycline or 0.5, 1.0, or 2.0 mg/kg mitoxantrone. The animals were killed at 28 days and the pleural spaces assessed grossly for pleurodesis and microscopically for fibrosis and inflammation. The mean degree of gross pleurodesis did not differ significantly in the rabbits that received tetracycline (3.8 ± 0.4) and in the rabbits that received 2 mg/kg mitoxantrone (3.2 ± 1.3). The degree of pleural and lung inflammation was significantly greater after mitoxantrone than after tetracycline, both ipsilaterally and contralaterally. The mortality after the highest dose of mitoxantrone was 50%. From this study we conclude that the intrapleural administration of mitoxantrone in rabbits can produce a pleurodesis. The histologic picture after mitoxantrone administration differs markedly from that after tetracycline injection. After mitoxantrone injection there are many more inflammatory cells present on the side that received the injection, and there is much more fibrosis and inflammation in the contralateral pleura and lung. The model of pleural fibrosis following intrapleural mitoxantrone may be useful for the study of pleural fibrosis.