Loss of hypoxic ventilatory response following bilateral neck dissection.

Modified radical neck or combined radical and modified radical neck surgery is performed for treatment of head and neck cancer. Because of the extensive nature of the surgery, including dissection around the carotid vessels, we prospectively evaluated hypoxic ventilatory responses preoperatively and postoperatively in five patients. The change in ventilation to percent desaturation varied between -0.22 and -0.60 L/min per percent desaturation in the five study patients. In the postoperative evaluation, two of five patients showed flattened responses compared with the preoperative measurements due to denervation of their carotid bodies. Two patients showed increased responses due to loss of upper airway resistance from tracheostomy. We conclude that after bilateral neck dissection for cancer surgery some patients may lose their hypoxic ventilatory responses due to carotid body denervation.

Effect of alteration of cerebrospinal fluid bulk flow on nicotine cerebrospinal fluid exit transfer kinetics.

This study was undertaken to determine if a compound which alters the bulk flow of cerebrospinal fluid (CSF) alters the elimination kinetics of a compound in the CSF. Acetazolamide was chosen as the CSF bulk flow-altering agent. It produces a relatively large effect on the flow process, affecting both choroidal and extrachoroidal CSF production, and has been shown to affect CSF flow following iv administration. The compound monitored was nicotine. Acetazolamide was administered orally for one week before and intravenously during the experiment. Nicotine was administered by a bolus injection directly into the CSF via the cisterna magna. The results indicate that the introduction of acetazolamide into the general circulation increases the rate of removal of nicotine from the CSF. Subjects receiving acetazolamide had elevated CSF pressures. The increase in CSF pressure associated with the administration of acetazolamide suggests pressure as a possible factor in the observed increase in the rate of removal of nicotine.

The ventilatory response to intravenous and ventriculo-cisternal theophylline.

The stimulatory effect of theophylline on ventilation was studied in nine anesthetized dogs. Theophylline infused intravenously (10 mg/kg bolus, then 1.00 mg/kg/hr) for 210 minutes significantly increased the minute volume of ventilation (P less than 0.05 at 210 minutes). After a recovery period of seven to fourteen days, ventriculo-cisternal perfusion was performed with mock cerebrospinal fluid (CSF). Theophylline added to the mock CSF did not significantly change the minute ventilation. ventriculo-cisternal perfusion utilizing mock CSF not containing theophylline combined with intravenous theophylline infusion stimulated ventilation similarly to the previous intravenous theophylline infusion. Therefore, stimulation of ventilation by theophylline appears to relate to the serum theophylline concentration and not the ventricular CSF theophylline concentration.