Gagging.

Gagging is a protective reflex to stop unwanted entry into the mouth and oropharynx. Some people have a reduced or absent reflex, while others have a pronounced one. Pronounced gag reflexes can compromise all aspects of dentistry, from the diagnostic procedures of examination and radiography to any form of active treatment. In some patients with marked gagging reflexes, it can lead to avoidance of treatment. Many techniques have been described that attempt to overcome this problem, and a variety of management strategies is necessary to aid the delivery of dental care. This is a review of the etiology of gagging problems, clinical assessment, and their classification and categorization prior to clinical treatment. It discusses as well methods for managing patients with gag reflexes during dental treatment.

Phenobarbital-responsive sialadenosis associated with an esophageal foreign body in a dog.

A 4-year-old Yorkshire terrier was presented for an esophageal foreign body. After removal of the foreign body, clinical signs of gagging, regurgitation, and vomiting continued unabated for >6 weeks. The dog had enlarged submandibular salivary glands that were histologically normal. Treatment with phenobarbital resulted in a rapid and dramatic resolution of clinical signs. After 3 months, the dog was weaned of phenobarbital and was free of any signs of disease 6 months later.

Pharmacodynamics and systemic exposure of esomeprazole in preterm infants and term neonates with gastroesophageal reflux disease.

OBJECTIVE: To characterize the pharmacodynamics and systemic exposure of esomeprazole in 26 preterm infants and term neonates with symptoms of gastroesophageal reflux and pathologic acid exposure. STUDY DESIGN: Enrolled patients received oral esomeprazole 0.5 mg/kg once daily for 7 days. Twenty-four-hour esophagogastric pH-impedance monitoring was performed at baseline and on day 7. Pharmacokinetic analysis was performed on day 7. Symptoms occurring during the baseline and day 7 studies were recorded on a symptom chart. RESULTS: There were no significant differences from baseline to day 7 of therapy in the frequency of bolus reflux, consistency of bolus reflux (liquid, mixed, or gas), extent of bolus reflux, or bolus clearance time. Acid bolus reflux episodes were reduced on therapy (median 30 vs 8, P < .001), as was the reflux index (mean % time esophageal pH < 4, 15.7% vs 7.1%, P < .001). The estimated geometric mean of area under the plasma concentration time curve during the dosing interval and observed maximum plasma concentration was 2.5 micromol x h/L and 0.74 micromol/L, respectively. The number of gastroesophageal reflux symptoms recorded over 24 hours was lower on therapy (median 22 vs 12, P < .05). CONCLUSIONS: In preterm infants and term neonates esomeprazole produces no change in bolus reflux characteristics despite significant acid suppression.

Emetic stimulation inhibits the swallowing reflex in decerebrate rats.

The effects of emetic stimulation on the swallowing reflex were investigated in decerebrated rats. Hypoxia, gastric distension and LiCl administration were used as emetic stimulations. The swallowing reflex was elicited by electrical stimulation of the superior laryngeal nerve (SLN, 20 Hz, 3-5 V, 0.3 ms duration) for 20 s. To examine the effect of hypoxia, nitrogen gas was inhaled under artificial ventilation. There were significantly fewer swallows during a decrease in PO(2) than under air ventilation (p<0.05). The number of swallows during 3-ml stomach distension was significantly lower than that before distension (p<0.05). Intravenous administration of LiCl (100 mg/kg) also significantly reduced the number of swallows (p<0.05). The combination of SLN stimulation and emetic stimuli occasionally produced burst activity of abdominal muscles, which might be associated with the gag reflex. Both the gag and swallowing reflexes are well known to be mediated by the nucleus of the solitary tract. The physiological roles of the gag reflex and the swallowing reflex are considered to be reciprocal. Taken together, these results suggest that emetic stimulation inhibits the swallowing pattern generator via the nucleus of the solitary tract, which in turn facilitates the gag reflex.

Efficacy of granisetron for the treatment of postoperative nausea and vomiting in women undergoing breast surgery: a randomised, double-blind, placebo-controlled trial.

BACKGROUND: Women undergoing general anaesthesia for breast surgery are especially at risk of experiencing postoperative nausea and vomiting (PONV). This study was undertaken to assess the efficacy of granisetron, a selective serotonin type 3 receptor antagonist, for the treatment of postoperative nausea and vomiting after breast surgery. DESIGN AND METHODS: This was a prospective, randomised, double-blind, placebo-controlled study carried out in a university-affiliated teaching hospital. The study included women who experienced nausea lasting >10 minutes and/or vomiting during the first 3 hours after recovery from anaesthesia for breast surgery. Patients intravenously received either placebo or granisetron at four different doses (10 microg/kg, 20 microg/kg, 40 microg/kg and 80 microg/kg). Patients were observed for 24 hours after administration of the study drug. MAIN OUTCOME MEASURES AND RESULTS: A total of 100 women were enrolled in this study. Complete control of established PONV, defined as no emetic symptoms and no need for a rescue antiemetic, was observed in 50% of women receiving granisetron 10 microg/kg (p = 0.5 vs placebo), 85% of women receiving granisetron 20 microg/kg (p = 0.009 vs placebo), 90% of women receiving granisetron 40 microg/kg (p = 0.003 vs placebo), and 85% of women receiving granisetron 80 microg/kg (p = 0.009 vs placebo), compared with 45% of placebo recipients. The efficacies of granisetron 20 microg/kg, granisetron 40 microg/kg, and granisetron 80 microg/kg for the treatment of established PONV were superior to that of granisetron 10 microg/kg (all p < 0.05). No serious adverse effects were observed in any group. CONCLUSION: The minimum effective dose of granisetron for the treatment of PONV in women undergoing breast surgery was 20 microg/kg. Increasing the granisetron dose to 80 microg/kg provided no further benefit.

Effects of injecting GABAergic agents into the medullary reticular formation upon swallowing induced by the superior laryngeal nerve stimulation in decerebrate cats.

The purpose of this study was to elucidate the role of the GABAergic system in the medullary reticular formation (MRF) in the control of swallowing. In acutely decerebrated cats (n = 12), swallowing was induced by electrical stimulation (0.3-6 V at 10-20 Hz for 10-20 s every minute) applied to the superior laryngeal nerve (SLN). The stimulus intensity was adjusted so that swallowing was induced two or four times during the period of the stimulation. Bicuculline, a GABA(A) receptor antagonist, was then injected (0.10-0.15 microl, 5 mM) into the MRF through a stereotaxically placed glass micropipette. In a total of 62 injections, 19 injections (30.6%) increased the frequency of SLN-induced swallowing when it was injected into the lateral part of the MRF corresponding to the nucleus reticularis parvocellularis (NRPv). In eight of the effective injections (42.1%) which increased the frequency of SLN-induced swallowing, SLN stimulation also induced coughing. With two injections, stimulation of the SLN-induced coughing but not facilitation of swallowing. On the other hand, an injection of 0.10-0.15 microl of 5 mM muscimol, a GABA(A) receptor agonist, into the NRPv decreased the frequency of SLN-induced swallowing. These results suggest that the NRPv neurons which are responsible for evoking swallowing are under the tonic inhibitory control of the GABAergic system.

Sympathoexcitatory response to cyclosporin A and baroreflex resetting.

We postulate that the sympathoexcitatory response associated with the immunosuppressive agent cyclosporin A is due to an upward resetting of the arterial baroreflex. We performed studies in conscious intact and sinoaortic-denervated rabbits instrumented with catheters and renal nerve electrodes. In intact rabbits, cyclosporin A (20 mg/kg i.v., 30 minutes) produced significant increases in renal sympathetic nerve activity (100% to 269 +/- 74%, P < .05) but did not increase mean arterial pressure. In intact rabbits, we determined arterial baroreflex curves relating renal sympathetic nerve activity and heart rate to mean arterial pressure by producing ramp increases (intravenous phenylephrine) and decreases (intravenous nitroprusside) in mean arterial pressure. Cyclosporin A treatment produced a shift of the midrange of the baroreflex control of heart rate (78.0 +/- 4.1 to 84.6 +/- 4.7 mm Hg, P < .05) and renal sympathetic nerve activity (74.6 +/- 3.9 to 87.0 +/- 4.8 mm Hg, P < .05). Vehicle administration produced no effects on arterial baroreflex curves relating renal sympathetic nerve activity and heart rate to mean arterial pressure. Compared with vehicle treatment, cyclosporin A reduced the maximum gain of heart rate (-5.6 +/- 0.6 versus -3.1 +/- 0.8 beats per minute per millimeter of mercury, P < .05) but had no effect on the maximum gain of renal sympathetic nerve activity. In conscious sinoaortic-denervated rabbits, cyclosporin A had no effect on mean arterial pressure (95.7 +/- 7.3 to 91.8 +/- 10.8 mm Hg), renal sympathetic nerve activity (100% to 110 +/- 6%). and heart rate (287 +/- 10 to 279 +/- 8 beats per minute). However, when the same sinoaortic-denervated rabbits were anesthetized with sodium pentobarbital, cyclosporin A (20 mg/kg i.v.) produced increases in renal sympathetic nerve activity (100% to 189 +/- 27%). These data indicate (1) that the sympathoexcitatory response to cyclosporin A depends on baroreceptor afferent input in the conscious state and (2) that this response involves an upward resetting of the arterial baroreflex.

Phenothiazine-induced bulbar palsy-like syndrome and sudden death.

There have been periodic case reports of sudden death due to aspiration or asphyxiation in patients receiving phenothiazines. The mechanism of death is unknown. The author reports a case of a drug-induced bulbar palsy-like syndrome in a man receiving fluphenazine enanthate and reviews the literature on sudden respiratory death and phenothiazines. He postulates that phenothiazine-induced bulbar palsy may cause laryngeal and/or pharyngeal dysfunctions that are responsible for aspiration.

Resinferatoxin, an ultrapotent capsaicin analogue, has anti-emetic properties in the ferret.

Resinferatoxin (100 micrograms/kg, s.c.), the ultrapotent analogue of capsaicin, when given acutely blocked radiation-(200 rads) and copper sulphate (40 mg% 30 ml, p.o.)-induced emesis in ferrets and substantially decreased loperamide (0.5 mg/kg, s.c.)-induced vomiting, without significantly affecting the von Bezold-Jarisch reflex or gag reflex. It also produced a decrease in core temperature as has been reported for capsaicin. The observation that resinferatoxin reduced or blocked emesis induced by both centrally (loperamide) and peripherally (CuSO4, radiation) acting stimuli suggests a novel anti-emetic action that may provide an insight into clinically useful innovative anti-emetics. The mechanism by which resinferatoxin has its anti-emetic effect is at present unknown, although the combination of results from the present study suggest a central site of action involving modulation of release of neurotransmitter, possibly in the nucleus tractus solitarius.

The anti-emetic effects of CP-99,994 in the ferret and the dog: role of the NK1 receptor.

1. The selective NK1 receptor antagonist, CP-99,994, produced dose-related (0.1-1.0 mg kg-1, s.c.) inhibition of vomiting and retching in ferrets challenged with central (loperamide and apomorphine), peripheral (CuSO4) and mixed central and peripheral (ipecac, cisplatin) emetic stimuli. 2. Parallel studies with the enantiomer, CP-100,263 (1 mg kg-1, s.c.), which is > 1,000 fold less potent as a NK1 antagonist, indicated that it was without significant effect against CuSO4, loperamide, cisplatin and apomorphine-induced emesis. Against ipecac, it inhibited both retching and vomiting, expressing approximately 1/10th the potency of CP-99,994. 3. The 5-HT3 receptor antagonist, tropisetron (1 mg kg-1, s.c.) inhibited retching and vomiting to cisplatin and ipecac, but not CuSO4 or loperamide. 4. CP-99,994 (1 mg kg-1, i.v.) blocked retching induced by electrical stimulation of the ventral abdominal vagus without affecting the cardiovascular response, the apnoeic response to central vagal stimulation or the guarding and hypertensive response to stimulation of the greater splanchnic nerves. CP-99,994 (1 mg kg-1, i.v.) did not alter baseline cardiovascular and respiratory parameters and it failed to block the characteristic heart rate, blood pressure and respiratory rate/depth changes in response to i.v. 2-methyl-5-HT challenge (von Bezold-Jarisch reflex). 5. Using in vitro autoradiography, [3H]-substance P was shown to bind to several regions of the ferret brainstem with the density of binding in the nucleus tractus solitarius being much greater than in the area postrema. This binding was displaced by CP-99,994 in a concentration-related manner. 6. In dogs, CP-99,994 (40 micrograms kg-1 bolus and 300 micrograms kg-1 h-1, i.v.) produced statistically significant reductions in vomiting to CuSO4 and apomorphine as well as retching to CuSO4. 7. Together, these studies support the hypothesis that the NK1 receptor antagonist properties of CP-99,994 are responsible for its broad spectrum anti-emetic effects. They also suggest that CP-99,994 acts within the brainstem, most probably within the nucleus tractus solitarius although the involvement of the area postrema could not be excluded.

Lack of involvement of alpha-adrenoceptors in sympathetic neural vasoconstriction in the hindquarters of the rabbit.

The hypothesis that sympathetic nerves in arterial blood vessels activate excitatory receptors distinct from alpha-adrenoceptors was investigated in vivo in the rabbit. In anaesthetized, ganglion-blocked rabbits, graded stimulation of the lumbar sympathetic nerve chains caused graded hind limb vasoconstriction. The responses to single pulses and short trains of stimuli were unaffected by benextramine (10 mg kg-1) and the longer trains were enhanced. Phenoxybenzamine (5 mg kg-1) slightly reduced the responses to short trains of stimuli and did not affect the responses to long trains. The dose-response curve to intra-arterial noradrenaline (after beta-adrenoceptor blockade) was shifted rightwards about ten fold by benextramine (10 mg kg-1) and by phenoxybenzamine (5 mg kg-1). In conscious rabbits the vasoconstriction caused by the nasopharyngeal reflex initiated by smoke inhalation was unaffected by benextramine (10 mg kg-1). Small mesenteric arteries (less than 250 microns) taken from untreated rabbits responded to noradrenaline with a threshold concentration of about 1 microM. Similar tissues from benextramine (10 mg kg-1)-treated rabbits were unresponsive to noradrenaline at concentrations up to 300 microM. However, these tissues were able to respond to potassium and angiotensin II. Aortic ring segments taken from the same rabbits were only about ten fold less sensitive to noradrenaline than segments from control rabbits. These results are in accord with the hypothesis that sympathetic nerves activate non-alpha-receptors in the vasculature of the rabbit.

The effect of neuroleptic and antiparkinsonian medication on the gag reflex.

A polygraph assessment of medicated psychiatric patients suggests anticholinergic effects are the primary cause of a diminished gag reflex. Sex differences indicate that females are relatively protected.

Midazolam for upper gastrointestinal endoscopy.

A water-soluble benzodiazepine, midazolam, was used in 400 patients undergoing upper gastrointestinal endoscopy, alone or in combination with pentazocine and compared with 68 patients given diazepam (Valium). In the last 200 patients the endoscopist used midazolam without the presence of an anaesthetist. The absence of injection pain was the most notable feature of midazolam. The degree of co-operation was similar in all groups but the operating conditions were significantly better when midazolam was combined with pentazocine. There was no significant difference in recovery times between the groups as assessed by the pegboard test. Midazolam is an acceptable alternative to diazepam for upper gastrointestinal endoscopy.

Sedation for gastroscopy: a comparison between midazolam and midazolam with nalbuphine.

Forty patients received either midazolam or midazolam with nalbuphine in a double-blind randomised study of sedation for upper gastrointestinal endoscopy. There were less retching, gagging and salivation in the combination group compared to midazolam alone. They were also more cooperative. These resulted in greater ease of insertion of the gastroscope. There was no significant difference in the degree of amnesia in both groups. A significant decrease in oxygen saturation was noted in both groups during the procedure. Monitoring with a pulse oximeter is recommended when sedation is administered during gastroscopy.

An experimental study of the control of the gag reflex with nitrous oxide.

Gagging represents a management problem during dental procedures. A controlled, double blind experiment on human volunteers evaluated the efficacy of nitrous oxide for suppressing experimentally-induced gagging. The ability of the subjects to tolerate palatal and oropharyngeal stimulation was evaluated by measuring the distance of the anatomic palatal and oropharyngeal structure which produce gagging. It was observed that under N(2)O/O(2) inhalation subjects tolerated a significantly more intrusive (deeper) oropharyngeal stimulation than under control conditions.