Thermal suit in preventing unintentional intraoperative hypothermia during general anaesthesia: a randomized controlled trial

BACKGROUND

Unintentional perioperative hypothermia causes serious adverse effects to surgical patients. Thermal suit (T-Balance^® ) is an option for passive warming perioperatively. We hypothesized that the thermal suit will not maintain normothermia more efficiently than conventional cotton clothes when also other preventive procedures against unintentional hypothermia are used.

METHODS

One hundred patients were recruited to this prospective, randomized trial. They were allocated to the Thermal Suit group or a Control group wearing conventional hospital cotton clothes. All patients received our institution's standard treatment against unintentional hypothermia including a warming mattress, a forced-air upper body warming blanket and a warming device for intravenous fluids. Eardrum temperature was measured pre-operatively. In the operating room and post-anaesthesia care unit temperatures were measured from four locations: oesophagus, left axilla, dorsal surface of the left middle finger and dorsum of the left foot. The primary outcome measure was temperature change during robotic-assisted laparoscopic radical prostatectomy.

RESULTS

The temperatures of 96 patients were analysed. There was no difference in mean core temperatures, axillary temperatures or skin temperatures on the finger between the groups. Only foot dorsum temperatures were significantly lower in the Thermal Suit group. Intraoperative temperature changes were similar in both groups. In the post-anaesthesia care unit temperature changes were minimal and they did not differ between the groups.

CONCLUSION

Provided that standard preventive procedures in maintaining normothermia are effective the thermal suit does not provide any additional benefit over conventional cotton clothes during robotic-assisted laparoscopic radical prostatectomy.

Treatment of hyperphosphatemia, secondary hyperparathyroidism and hypocalcemia with calcium carbonate favorably modulates vaccination response in uremic rats

AIMS

Immune dysfunction is characteristic of renal failure, leading to suboptimal antibody generation and increased susceptibility to infections. We tested whether the treatment of uremic phosphate retention by increased calcium carbonate intake will beneficially influence vaccination response in 5/6-nephrectomized rats.

METHODS

The nephrectomized (uremic) and sham-operated (control) rats were either fed 0.3% calcium diet (NTX and Sham groups, respectively) or 3% high-calcium diet (Ca-NTX and Ca-Sham groups). All rats were immunized with tetanus toxoid 6 weeks after the operations, and antitoxin levels were measured 7 weeks later.

RESULTS

Plasma creatinine was significantly elevated after the nephrectomy: the values (mean +/- SD) in the NTX (n = 16), Ca-NTX (n = 11), Sham (n = 14) and Ca-Sham (n = 8) groups were 97 +/- 14, 93 +/- 17, 66 +/- 7, and 69 +/- 8 micromol/l, respectively. The NTX group developed phosphate retention and secondary hyperparathyroidism, which were completely prevented by the high calcium diet. The mean tetanus antitoxin concentrations of the groups were: NTX 0.25 +/- 0.32; Ca-NTX 0.45 +/- 0.44; Sham 0.58 +/- 0.24 and Ca-Sham 0.64 +/- 0.25 IU/ml (log of geometric mean concentration). The antibody response in the NTX group was significantly lower, i.e. 43% of that in the Sham group (p = 0.003), while the response in the Ca-NTX group was not different from that in the Sham group. The tetanus response of all the uremic rats inversely correlated with the plasma levels of phosphate (r = 0.447, p = 0.02), parathormone (r = -0.409, p = 0.03) and creatinine (r = 0.578, p = 0.002).

DISCUSSION

We conclude that renal failure impairs vaccination response in rats, the impairment of which can be favorably modulated by phosphate-binding and PTH-suppressing high-calcium diet.

Mechanism of the prorelaxing effect of thyroxine on the sphincter of Oddi

BACKGROUND

Disturbances in the function of sphincter of Oddi (SO) may prevent normal bile flow and thus enhance the probability of common bile duct stone (CBDS) formation. Previously, we have shown increased prevalence of hypothyroidism in CBDS patients.

METHODS

In animal (pig) experiments, thyroxine (T4) and triiodothyronine have a specific inhibitory effect on SO contractility, which raises the possibility that the lack of this prorelaxing effect in hypothyroidism could, at least in part, explain the increased prevalence of CBDS. The aims of the present study were to investigate, whether human SO reacts similarly to T4, and to study the mechanisms of the T4 prorelaxing effect.

RESULTS

We found that T4 had similar inhibitory effects on both human and pig SO contractions. The T4 effect was dose-dependent, and maximum was observed in 30 min. The maximal prorelaxing effect was achieved with 0.1 nM T4 concentration, the effect of the physiological T4 concentration (0.01 nM) being about half of the maximal effect. Addition of alpha-adrenoceptor antagonist phentolamine, beta-adrenoceptor antagonist propranolol, nitric oxide (NO)-synthesis inhibitor L-NAME, nerve conductance blocker tetrodotoxin, or cyclooxygenase inhibitor diclofenac did not affect the T4-induced inhibition of contraction. Addition of transcription inhibitor actinomycin D or translation inhibitor cyclophosphamide partially reversed the T4-induced inhibition of contraction. Addition of K+ channel blocker glibenclamide totally reversed the T4-induced inhibition of contraction. In Western blotting, the thyroid hormone receptor (TR) antibody recognized 53 kDa and 58 kDa proteins, corresponding to beta1 and beta2 isoforms of TR, in the human SO tissue.

CONCLUSIONS

We conclude that T4 has a direct prorelaxing effect on human SO that expresses TR beta1 and beta2. This effect is mediated through a transcriptional mechanism that requires new mRNA and protein synthesis and subsequently leads to the activation of K+ channels.

Bile flow to the duodenum is reduced in hypothyreosis and enhanced in hyperthyreosis

Disturbances in sphincter of Oddi (SO) function may prevent normal bile flow and thus enhance probability of common bile duct stone (CBDS) formation. We have previously shown increased prevalence of diagnosed hypothyroidism in CBDS patients, which may be explained by thyroxine-induced inhibition of SO contractility, in addition to previously suggested changes in bile composition and hepatocytic excretion. The aim of this study was to investigate biliary dynamics in relation to altered thyroid gland function in rat, a rodent without a gallbladder. Euthyroid, hypothyroid or hyperthyroid Spraque-Dawley rats were anaesthetized with i.p. urethane, and exsanguinated at 15, 45, or 60 min after intravenous 99mTc HIDA injection. At these timepoints, the bile flow to intestine was determined by measuring the relative intestine vs. liver radioactivity. At 45 min this was 44% lower in hypothyroid rats and at 60 min 73% higher in hyperthyroid rats compared to euthyroid rats, while hepatic radioactivity at 15 min and blood pressure at injection were similar in the groups. We conclude that the bile flow to duodenum is reduced in hypothyreosis and enhanced in hyperthyreosis.

High-calcium diet enhances vasorelaxation in nitric oxide-deficient hypertension

Because the effects of calcium supplementation on arterial tone in nitric oxide-deficient hypertension are unknown, we investigated the influence of elevating dietary calcium from 1.1 to 3.0% in Wistar rats treated with N(G)-nitro-L-arginine methyl ester (L-NAME; 20 mg. kg(-1). day(-1)) for 8 wk. A high-calcium diet attenuated the development of hypertension induced by L-NAME and abrogated the associated impairments of endothelium-independent mesenteric arterial relaxations to nitroprusside, isoproterenol, and cromakalim. Endothelium-dependent relaxations to acetylcholine during nitric oxide synthase inhibition in vitro were decreased in L-NAME rats and improved by calcium supplementation. The inhibition of cyclooxygenase by diclofenac augmented the responses to acetylcholine in L-NAME rats but not in calcium + L-NAME rats. When hyperpolarization of smooth muscle was prevented by KCl precontraction, the responses to acetylcholine during combined nitric oxide synthase and cyclooxygenase inhibition were similar in all groups. Furthermore, superoxide dismutase enhanced the acetylcholine-induced relaxations in L-NAME rats but not in calcium + L-NAME rats. In conclusion, calcium supplementation reduced blood pressure during chronic nitric oxide synthase inhibition and abrogated the associated impairments in endothelium-dependent and -independent arterial relaxation. The augmented vasorelaxation after increased calcium intake in L-NAME hypertension may be explained by enhanced hyperpolarization and increased sensitivity to nitric oxide in arterial smooth muscle and decreased vascular production of superoxide and vasoconstrictor prostanoids.

Arterial responses in vitro and plasma digoxin immunoreactivity after losartan and enalapril treatments in experimental hypertension

Treatment with the angiotensin-converting enzyme inhibitor, quinapril, has been shown to normalize increased dihydropyridine sensitivity and impaired potassium relaxation, characteristic features of arterial smooth muscle in spontaneously hypertensive rats, and also reduce the concentration of plasma digoxin-like immunoreactivity in these animals. However, whether angiotensin II receptor blocker therapy can beneficially influence these variables is not known. Therefore, we compared the effects of 10-week losartan and enalapril treatments (15 and 4 mg/kg/day, respectively) on functional responses of mesenteric arterial rings in spontaneously hypertensive rats and Wistar-Kyoto rats. Both losartan and enalapril normalized blood pressure, cardiac mass, and media to lumen ratio without significantly changing the media cross-sectional area in the mesenteric artery of spontaneously hypertensive rats (i.e. induced outward remodelling). The inhibitory effect of the calcium entry blocker nifedipine on calcium-evoked contractions was similar and less marked in arterial preparations from Wistar-Kyoto rats and losartan- and enalapril-treated spontaneously hypertensive rats than in those from untreated spontaneously hypertensive rats. Furthermore, the relaxations of arterial rings induced by the return of potassium to the organ bath (upon precontractions elicited by potassium-free solution) were used to evaluate the function of vascular Na+,K+-ATPase. The rate of potassium relaxation was faster in losartan- and enalapril-treated spontaneously hypertensive rats and all Wistar-Kyoto groups than in untreated spontaneously hypertensive rats, and the response was effectively inhibited by the sodium pump inhibitor ouabain. Both treatments especially augmented the ouabain-sensitive part of the potassium-relaxation in spontaneously hypertensive rats, indicating the involvement of the sodium pump in this response. However, no significant changes in plasma digoxin-like immunoreactivity were observed. In conclusion, the outward remodelling following long-term AT1-receptor blockade and angiotensin-converting enzyme inhibition in spontaneously hypertensive rats was associated with normalization of the increased dihydropyridine sensitivity of arteries. Both losartan and enalapril treatments also augmented arterial potassium relaxation in spontaneously hypertensive rats, suggesting enhanced function of Na+,K+-ATPase, but this effect could not be attributed to changes in circulating sodium pump inhibitor concentration.

Differential regulation of cardiac adrenomedullin and natriuretic peptide gene expression by AT1 receptor antagonism and ACE inhibition in normotensive and hypertensive rats

OBJECTIVE

To study the effects of long-term treatment with the type 1 angiotensin (AT1) receptor antagonist losartan and the angiotensin-converting enzyme (ACE) inhibitor enalapril, on cardiac adrenomedullin (ADM), atrial natriuretic peptide (ANP) and B-type natriuretic peptide (BNP) gene expression.

METHODS

Spontaneously hypertensive rats (SHR) and Wistar-Kyoto (WKY) rats were given losartan (15 mg/kg per day) or enalapril (4 mg/kg per day) orally for 10 weeks. The effects of drugs on systolic blood pressure, cardiac hypertrophy, ANP, BNP and ADM mRNA and immunoreactive-ANP (IR)-ANP, IR-BNP and IR-ADM levels in the left ventricle and atria were compared.

RESULTS

Losartan and enalapril treatments completely inhibited the increase of systolic blood pressure occurring with ageing in SHR. The ratio of heart to body weight was reduced in both losartan- and enalapril-treated SHR and WKY rats. Treatment with losartan or enalapril reduced left ventricular ANP mRNA and IR-ANP in both strains, and ventricular BNP mRNA levels in SHR rats. Inhibition of ACE, AT1 receptor antagonism, changes in blood pressure or cardiac mass had no effect on left ventricular ADM gene expression in SHR and WKY rats. In addition, atrial IR-ANP and IR-ADM levels increased in SHR whereas IR-BNP levels decreased in WKY and SHR rats in response to drug treatments.

CONCLUSIONS

Our results show that ventricular ADM synthesis is an insensitive marker of changes in haemodynamic load or cardiac hypertrophy. Furthermore, the expression of ADM, ANP and BNP genes is differently regulated both in the left ventricle and atria in response to AT1 receptor antagonism and ACE inhibition.

Potassium channel-mediated vasorelaxation is impaired in experimental renal failure

Chronic renal failure is associated with increased cardiovascular morbidity and abnormal arterial tone, but the underlying pathophysiological mechanisms are poorly understood. Therefore, we studied the responses of isolated mesenteric arterial rings from Wistar-Kyoto rats in standard organ chambers 6 wk after subtotal (5/6) nephrectomy or sham operation. Subtotal nephrectomy resulted in a 1.7-fold elevation of plasma urea nitrogen, whereas blood pressure was not significantly affected. Endothelium-mediated relaxations of norepinephrine-precontracted rings to ACh were impaired in renal failure rats. The nitric oxide (NO) synthase inhibitor N(G)-nitro-L-arginine methyl ester inhibited relaxations to ACh more effectively in the renal failure group, whereas the cyclooxygenase inhibitor diclofenac did not significantly affect the response in either group. Inhibition of Ca(2+)-activated K(+) channels by charybdotoxin and apamin attenuated NO synthase- and cyclooxygenase-resistant relaxations to ACh in control but not renal failure rats and abolished the difference between these groups. Endothelium-independent relaxations to isoproterenol and cromakalim, vasodilators acting via beta-adrenoceptors and ATP-sensitive K(+) channels, respectively, were impaired in the renal failure group, whereas relaxations to the NO donor nitroprusside were similar in both groups. In conclusion, endothelium-mediated relaxation in renal failure rats was impaired in the absence and presence of NO synthase and cyclooxygenase inhibition but not with prevented smooth muscle hyperpolarization. Endothelium-independent relaxations to isoproterenol and cromakalim were also attenuated after 5/6 nephrectomy. These results suggest that impaired vasodilatation in experimental renal failure could be attributed to reduced relaxation via arterial K(+) channels.

Arterial function in nitric oxide-deficient hypertension: influence of long-term angiotensin II receptor antagonism

OBJECTIVE

Since the effects of angiotensin II receptor antagonism on arterial function in nitric oxide (NO)-deficient hypertension are unknown, we investigated the influence of losartan therapy (20 mg kg-1 day-1) on the control of arterial tone in NG-nitro-L-arginine methyl ester (L-NAME; 20 mg kg-1 day-1)-induced hypertension.

METHODS

Forty Wistar rats were divided into four groups: control, losartan, L-NAME, and losartan + L-NAME. The responses of isolated mesenteric arterial rings were examined in standard organ chambers after 8 treatment weeks.

RESULTS

Losartan therapy prevented the development of L-NAME-induced hypertension and the associated impairments of endothelium-independent relaxations to nitroprusside, isoprenaline, and cromakalim, vasodilators acting via the formation of NO, activation of beta-adrenoceptors and opening of K+ channels, respectively. In addition, endothelium-dependent relaxations of noradrenaline-precontracted rings to acetylcholine during NO synthase inhibition in vitro were decreased in L-NAME rats, and clearly improved by losartan therapy. The inhibition of cyclooxygenase by diclofenac improved the responses to acetylcholine more effectively in L-NAME than losartan + L-NAME rats, but the relaxations remained decreased in L-NAME rats when compared with losartan + L-NAME rats. When hyperpolarization of smooth muscle was prevented by precontractions induced by high concentration of KCl, the responses to acetylcholine during combined NO synthase and cyclooxygenase inhibition were similar and almost abolished in all groups. Furthermore, superoxide dismutase, a scavenger of superoxide anions, enhanced the acetylcholine-induced relaxations more effectively in L-NAME than losartan + L-NAME rats, although plasma antioxidant capacity was similar in all study groups.

CONCLUSION

Chronic L-NAME-induced hypertension was associated with attenuated arterial relaxation via endothelium-dependent and -independent mechanisms, both of which were improved by the losartan treatment. The mechanisms whereby losartan enhanced arterial relaxation in this model of experimental hypertension may have included enhanced hyperpolarization and increased sensitivity to NO in smooth muscle, and decreased vascular production of superoxide and vasoconstrictor prostanoids.

Losartan and enalapril therapies enhance vasodilatation in the mesenteric artery of spontaneously hypertensive rats

We studied the effects of 10-week long enalapril and losartan treatments (4 and 15 mg kg(-1) day(-1), respectively) on mesenteric arterial function in vitro in spontaneously hypertensive rats (SHR) and Wistar-Kyoto rats (WKY). The relaxations of noradrenaline-precontracted rings to acetylcholine, nitroprusside and cromakalim were similar in WKY and enalapril- and losartan-treated SHR, and more pronounced than in untreated SHR. The responses to acetylcholine were attenuated by N(G)-nitro-L-arginine methyl ester in WKY and drug-treated SHR, but were completely inhibited in untreated SHR. When hyperpolarization of smooth muscle was prevented by KCl-induced precontractions, no differences were found in the relaxations to acetylcholine and nitroprusside between the groups, and the dilatations to cromakalim were abolished. Moreover, in noradrenaline-precontracted rings of drug-treated SHR, the addition of tetraethylammonium attenuated the nitric oxide synthase and cyclooxygenase-resistant relaxations to acetylcholine and abolished the enhanced dilatations to nitroprusside. In conclusion, since the enhancement of vasorelaxation in enalapril- and losartan-treated SHR was abolished by conditions preventing hyperpolarization, the improved vasodilatation following these therapies could be attributed to enhanced vasodilatation via K+ channels in this model of hypertension.

Accumulation of bisphosphonates in human artery and their effects on human and rat arterial function in vitro

Clodronate, etidronate and pamidronate are bisphosphonates introduced in the treatment of hypercalcaemia and osteoporosis. Interestingly, they also inhibit development of experimental atherosclerosis and affect smooth muscle tone of isolated rat tail artery. We have studied in vitro whether these hydrophilic compounds 1) accumulate in the wall of the human artery, 2) influence human arterial tone, and 3) interfere with the vascular action of L-type Ca2+ antagonists. Human internal mammary artery rings were incubated with 14C-labelled bisphosphonates. After a 2-hr incubation, the ratios of artery-to-incubate concentrations with 4 and 40 mumol/l of clodronate were, respectively, 3.0 +/- 0.5 (mean +/- S.E.M.) and 1.3 +/- 0.2, with 4 and 40 mumol/l of etidronate 7.4 +/- 0.9, and 3.2 +/- 0.4, and with 0.4 and 4 mumol/l of pamidronate 4.7 +/- 0.7 and 3.9 +/- 0.8. Both tested bisphosphonates, clodronate and pamidronate, reduced the arterial contractile force induced by alpha-adrenergic stimulation with noradrenaline and membrane depolarization with high concentration of KCl. Clodronate also decreased the arterial contraction induced by cumulative addition of Ca2+ with KCl as the agonist, and had an additive inhibitory effect on this response with the L-type Ca2(+)-channel blocker nifedipine. The results demonstrate that 1) bisphosphonates accumulate markedly in human artery, 2) clodronate and pamidronate reduce human arterial contactile force to alpha-adrenergic and depolarizing stimuli, and 3) as shown with clodronate, bisphosphonates may exert an additive inhibitory effect on human arterial contractions with an L-type Ca2(+)-channel blocker.