The impact of brushing teeth on carbon-14 urea breath test results

OBJECTIVE

The 14C urea breath test noninvasively detects the presence of the urease-producing bacteria Helicobacter pylori in the stomach. Several sources of errors have been identified to cause false or indeterminate results on the test. The objective of this study was to identify whether brushing teeth affects the test results.

METHODS

We performed the 14C urea breath test on 168 patients, with breath samples counted at 10 and 20 min after oral administration of 2 microCi (74 kBq) 14C urea. Ninety-four patients brushed their teeth before the test while 74 did not.

RESULTS

Thirty-six of the 74 patients (49%) who did not brush their teeth had positive results at 10 min, which became negative at 20 min. None of the 94 patients who brushed their teeth before testing showed this pattern with agreement of results at 10 and 20 min.

CONCLUSION

We recommend brushing teeth before the 14C urea breath test since it significantly decreased the ambiguous results of the test in our laboratory.

Placental binding and transfer of radiopharmaceuticals: technetium-99m d, 1-HMPAO

Placental binding and transfer of 99mTc d, 1-hexamethyl propyleneamine oxime (HMPAO) was studied in vitro using human placenta and pregnant guinea pigs.

MATERIALS AND METHODS

Five pieces of human placenta were incubated in 50 ml Earle's solution containing 1.85 MBq 99mTc d, 1-HMPAO. The percent binding of the tracer to the placenta per 1 ml standard solution was calculated. Pregnant guinea pigs representing first, second and third trimesters were each injected with 74 MBq 99mTc d, 1-HMPAO through the jugular or femoral vein after sedation was induced with pentabarbital sodium. Static images were obtained, the guinea pigs were killed, and the fetuses were removed, weighed and imaged separately. The placentas, maternal and fetal brains, lungs, livers and kidneys also were removed, and the radioactivity was assayed in a dose calibrator for each organ. The percent radioactivity in each organ was calculated.

RESULTS

The binding of 99mTc d, 1-HMPAO to human placenta ranged from 2.95% +/- 1.5% to 5.82% +/- 0.3% per 1 ml standard solution. Both the binding of 99mTc d, 1-HMPAO to guinea pig placenta and its transfer to the fetus increased with gestational age. The percent binding ranged from 0.09% +/- 0.06% to 0.43% +/- 0.05%, whereas that of transfer to the fetus ranged from 0.05% +/- 0.03% to 2.19% +/- 0.64%. Of the amount transfered to the fetus, the order of accumulation in the fetal organs was liver > blood >> brain > lungs > kidneys > heart.

CONCLUSION

Technetium-99m d, 1-HMPAO binds to the placenta, and a minimal amount crosses the placental barrier and is transfered into the fetal circulation, mostly in the liver but a measurable amount is found in brain tissue.

Is rocuronium an exception to the relation between onset and offset? A comparison with pipecuronium

A general relation between the rate of onset and rate of recovery from non-depolarizing blockade has been demonstrated, with recovery consistently about ten times slower than onset. This observation has led to the suggestion that non-depolarizing agents share a common mechanism of action. Rocuronium, a recently introduced steroidal non-depolarizing agent, is claimed to have a very rapid onset but an intermediate duration and appears to test this hypothesis. To investigate this paradox we have calculated the rates of onset and recovery of rocuronium using the isolated human forearm and compared them with those of pipecuronium. The mean ratio of recovery time/onset time for rocuronium was 31.3, which is significantly greater than that for pipecuronium, 11.6 (P < 0.01). Whilst pipecuronium conforms to the same general relation between onset and offset described previously for other non-depolarizing agents, rocuronium appears to have a disproportionately rapid rate of onset for its rate of recovery. This suggests that onset, recovery, or both onset and recovery, from rocuronium blockade occur in a different manner to that of other non-depolarizing agents.

Effect of voluntary tetanus on recovery of vecuronium block in the isolated forearm

This study was conducted to investigate the effect of voluntary tetanus on the recovery from neuromuscular block produced by a nondepolarising drug, vecuronium, in the isolated forearm. We have studied the recovery indices and train of four fade at different levels of recovery following vecuronium in both isolated forearms simultaneously, in six sets of experiments. In one hand the volunteer performed a maximum contraction of his thumb repeatedly at fixed intervals. We found that following voluntary tetanus there is an increased rate of recovery from nondepolarising neuromuscular block; mean Recovery Index (7.4, SD 0.97) compared to control Recovery Index (10.55, SD 2.58), p < 0.05. The train-of-four fade also showed a sustained reduction in the isolated forearm which underwent voluntary tetanus. During the later phase of recovery the train-of-four fade showed significant difference statistically (p < 0.01). The findings of this study supports the hypothesis that more rapid recovery associated with voluntary tetanus is due to a reduction in the presynaptic block thus resulting in an increased rate of transmitter release.