Cardiovascular and metabolic responses to adrenaline infusion in patients with short-term hypothyroidism

Modulation of plasma adrenomedullin by epinephrine infusion during head up tilt

We investigated whether head up tilt (HUT) with and without simultaneous epinephrine infusion modulate plasma adrenomedullin. We studied eight healthy male volunteers, using two 5 min 70° HUT trials: control (saline infusion) and intervention (epinephrine infusion, titrated to a dose which increased supine systolic pressure by 20% above resting values). Protocols were randomized and separated by 2 weeks. Cardiac function and systolic time intervals, recorded using a phonocardiograph microphone, included left ventricular ejection time (LVET), pre-ejection period (PEP), PEP/LVET and electromechanical systole (QS2). Compared to saline infusion, epinephrine increased supine adrenomedullin (3.2 ± 0.8 pmol/l, i.e., mean ± SEM, respectively), heart rate (HR) (+11.3 ± 2.6 bpm), systolic pressure (+18.4 ± 2.6 mmHg) but decreased supine LVET, LVET corrected for HR (LVETi) and QS2-time (all p = 0.004). Despite similar HUT induced thoracic fluid shifts, reflected by similar thoracic impedance changes, HUT-induced adrenomedullin increases were minimal in epinephrine-supplemented men in comparison to controls (+8% vs. 42%). During HUT, epinephrine infusion decreased only the LVET (p = 0.039). Our findings confirm that short-term HUT increases plasma adrenomedullin. They further suggest that with increased supine epinephrine levels (epinephrine infusion clamping systolic arterial pressure at 120% control level), supine cardiac performance rises to a level similar to that during HUT, while adrenomedullin is still elevated with HUT. This might be in accordance with a 'dampening' role of adrenomedullin during catecholaminergic cardiovascular stimulation. As epinephrine is used as a drug to treat cardiac arrest and ventricular arrhythmias, our results may have important clinical/emergency resuscitation applications.

Short-term hypothyroidism after Levothyroxine-withdrawal in patients with differentiated thyroid cancer: clinical and quality of life consequences

Acute hypothyroidism induced by thyroid hormone withdrawal in patients with differentiated thyroid cancer during monitoring for remnant or metastatic disease, seriously affects multiple organs and systems, and especially in severe cases can impair quality of life. Indeed, it may induce untoward cardiovascular effects and can be hazardous in patients with underlying cardiovascular disease, particularly in the elderly. Moreover, acute hypothyroidism deranges the lipid profile and exacerbates neuropsychiatric illness. The introduction of recombinant human TSH (rhTSH) as a diagnostic and therapeutic tool in the care of patients with thyroid cancer has widened the scope of disease management. The use of rhTSH prevents derangement of various systems at approximately equivalent societal costs to that of withdrawal and promotes compliance while preserving the patient's normal daily functioning and productivity. Its reliability allied with its safety render this compound a valid alternative in the monitoring of patients with differentiated thyroid carcinoma as well as providing an alternative therapeutic procedure whenever LT4-withdrawal may be hazardous or in cases of patient non-compliance.

Management of patients with thyroid disease: oral health considerations

BACKGROUND

The thyroid gland and its hormones play an important role in the regulation of growth, development and metabolic functions of the body. Thyroid diseases include a group of conditions that can affect the delivery of dental care.

LITERATURE REVIEWED

The authors conducted a MEDLINE search of the medical and dental literature concerning thyroid disease and its management published between 1980 and 2000. The authors found eight published articles concerning this topic in the dental literature; a few of the articles specifically addressed thyroid disease and dental care. They reviewed the medical literature within the scope of provision of dental care.

CONCLUSIONS

The oral health care professional can play a role in the screening of dental patients who have undiagnosed thyroid disease. In addition, to treat patients who have thyroid disease, a thorough understanding of the many related pathological conditions, as well as the signs and symptoms that can occur, is needed. Specific dental treatment protocols for these patients are not found in the medicodental literature published between 1980 and 2000.

CLINICAL IMPLICATIONS

As part of a health care team, the dentist plays an important role in detecting thyroid abnormalities. Modifications of dental care must be considered when treating patients who have thyroid disease.

Signalling in body-weight homeostasis: neuroendocrine efferent signals

Whilst a number of neuroendocrine afferent signals are implicated in body-weight homeostasis, the major efferent pathway is the sympathetic nervous system (SNS), which affects both energy expenditure and substrate utilization. Thyroid hormones and their interactions with the SNS may also have a role to play. Some of the variability in resting energy expenditure can be explained by differences in SNS activity, and beta-blockade can reduce energy expenditure and diet-induced thermogenesis in Caucasians. Excess energy intake leads to SNS activation and increased diet-induced thermogenesis. A relationship has also been demonstrated between spontaneous physical activity and SNS activity. In many animal models the SNS activates brown adipose tissue thermogenesis, hence increasing diet-induced thermogenesis and dissipating excess energy as heat. This effect is mediated via beta3-adrenoceptors and activation of an uncoupling protein unique to brown adipose tissue. Homologous proteins have been identified in human tissues and may play a role in human energy expenditure. How the SNS is implicated in this process is unclear at present. beta3-Adrenoceptor polymorphism has been associated both with lower resting energy expenditure in some populations and with reduced autonomic nervous system activity. SNS effects on substrate cycling may also play a role. In the development of obesity the effects of the SNS in promoting lipolysis and fat oxidation are likely to be at least as important as its effects on thermogenesis. beta-Blockade has relatively small effects on energy expenditure, but more pronounced effects on reducing lipid oxidation, so tending to favour fat storage and weight gain. Low lipid oxidation is a risk factor for weight gain, and there is some evidence that low basal sympathetic nerve activity in muscle is associated with this process. Overall, the relationship between SNS activity and obesity is complex, with evidence of low SNS activity occurring in some, but not all, studies.

ADVERSE DRUG INTERACTIONS IN DENTAL PRACTICE: INTERACTIONS ASSOCIATED WITH VASOCONSTRICTORS

BACKGROUND

Adrenergic vasoconstrictors are commonly used by dentists to enhance the pain-relieving action of local anesthetics and to control local bleeding. Although normally considered safe for these applications, vasoconstrictors can participate in drug interactions that potentially are harmful to patients.

METHODS

The faculty of a March 1998 symposium entitled "Adverse Drug Interactions in Dentistry: Separating the Myths From the Facts" extensively reviewed the literature on drug interactions. They then established a significance rating of alleged adverse drug interactions pertaining to dentistry, based on the quality of documentation and severity of effect. The author of this article focused on the adrenergic vasoconstrictors epinephrine and levonordefrin.

RESULTS

Vasoconstrictor drug interactions involving tricyclic antidepressants, nonselective beta-adrenergic blocking drugs, certain general anesthetics and cocaine are well-documented in both humans and animals as having the potential for causing serious morbidity or death. Evidence for adverse interactions involving adrenergic neuronal blocking drugs, drugs with alpha-adrenergic blocking activity, local anesthetics and thyroid hormones is much less compelling, suggesting for the most part that clinically significant reactions may occur only when both the vasoconstrictor and the interacting drug are used in excessive doses. In the case of monoamine oxidase inhibitors, there is no credible evidence of a significant interaction with epinephrine or levonordefrin.

CONCLUSIONS

Potentially serious adverse drug interactions involving adrenergic vasoconstrictors can occur in dental practice. In most circumstances, careful administration of small doses of vasoconstrictors and avoidance of gingival retraction cord containing epinephrine, coupled with monitoring of vita signs, will permit these drugs to be used with no risk or only minimally increased risk. Only in the case of cocaine intoxication must adrenergic vasoconstrictors be avoided completely.

CLINICAL IMPLICATIONS

For optimal patient safety, dentists must recognize potential drug interactions involving adrenergic vasoconstrictors and modify their use of these agents accordingly.