Ritodrine- and terbutaline-induced hypokalemia in preterm labor: mechanisms and consequences

New therapeutic target NCF1-directed multi-bioactive conjugate therapies prevent preterm birth and adverse pregnancy outcomes

Preterm birth (PTB) is a leading cause of neonatal morbidity and mortality worldwide, yet the cellular and molecular mechanisms driving this condition remain undeciphered, thus limiting discovery of new therapies. In-depth analyses of human and mouse tissues associated with PTB, in combination with cellular studies, indicated that aberrantly high-expressed neutrophil cytoplasmic factor (NCF) 1 leads to oxidative distress, recruitment, and pro-inflammatory activation of neutrophils and macrophages, while sequentially overexpressed pro-inflammatory mediators induce contractions of uterine smooth muscle cells (USMCs) as well as apoptosis of USMCs and amniotic epithelial cells, thereby causing PTB. According to these new findings, we rationally engineered an amphiphilic macromolecular conjugate LPA by covalently integrating low-molecular-weight heparin, a reactive oxygen species-responsive/scavenging component, and an anti-inflammatory peptide. This bioengineered macromolecular conjugate can self-assemble into multi-bioactive nanoparticles (LPA NP). In a mouse model of PTB, LPA NP effectively delayed PTB and inhibited adverse pregnancy outcomes, by regulating NCF1-mediated oxidative-inflammatory cascades, i.e., attenuating oxidative stress, inhibiting inflammatory cell activation, reducing local inflammation, and decreasing contraction/apoptosis of myometrial cells. Packaging LPA NP into temperature-responsive, self-healing, and bioadhesive hydrogel further potentiated its in vivo efficacies after intravaginal delivery, by prolonging retention time, sustaining nanotherapy release, and increasing bioavailability in the placenta/uterus. Importantly, both the conjugate/nanotherapy and hydrogel formulations exhibited excellent safety profiles in pregnant mice, with negligible side effects on the mother and offspring.

Antenatal mgnesium sulfate and ritodrine increased potassium levels in preterm infants: A cohort study

BACKGROUND

Ritodrine and magnesium sulfate are administered to prevent preterm labor. Magnesium sulfate is also administered to prevent preeclampsia. These drugs have been reported to increase potassium levels in pregnant women and neonates. The aim of this study was to investigate the relationship between potassium levels in preterm infants and antenatal treatment.

METHODS

This prospective cohort study was conducted at Saiseikai Suita Hospital. Preterm infants born at <35 weeks' gestation between October 2012 and September 2014 were recruited and divided into four groups based on the antenatal treatment their mothers received. Serum and urine electrolyte levels at birth and serum potassium levels 1 day after birth were measured.

RESULTS

The mothers of 16 infants received no antenatal treatment (condition C); the mothers of 29 infants received antenatal ritodrine (R); the mothers of seven infants received magnesium sulfate (M); and the mothers of 15 infants received both magnesium sulfate and ritodrine (M + R). At birth, potassium levels were similar among the four groups. However, potassium levels a day after birth were significantly higher in the M + R group than in the other groups: median (min.-max.) mEq/L 4.8 (3.8-6.2), 4.8 (3.6-6.0), and 4.4 (3.8-5.9) vs. 5.8 (4.9-7.2), in the C, R, and M groups versus the M + R group, respectively (P < 0.01). Significantly more infants in the M + R group exhibited a fractional excretion of potassium of <10% compared with those in the other groups.

CONCLUSION

The increased potassium levels we observe in preterm infants of mothers who received antenatal magnesium sulfate and ritodrine administration on postnatal day 1 warrant monitoring by neonatologists.

Activation of the kidney sodium chloride cotransporter by the β2-adrenergic receptor agonist salbutamol increases blood pressure

The thiazide-sensitive sodium-chloride-cotransporter (NCC) in the kidney distal convoluted tubule (DCT) plays an essential role in sodium and potassium homeostasis. Here, we demonstrate that NCC activity is increased by the β2-adrenoceptor agonist salbutamol, a drug prevalently used to treat asthma. Relative to β1-adrenergic receptors, the β2-adrenergic receptors were greatly enriched in mouse DCT cells. In mice, administration of salbutamol increased NCC phosphorylation (indicating increased activity) within 30 minutes but also caused hypokalemia, which also increases NCC phosphorylation. In ex vivo kidney slices and isolated tubules, salbutamol increased NCC phosphorylation in the pharmacologically relevant range of 0.01-10 μM, an effect observed after 15 minutes and maintained at 60 minutes. Inhibition of the inwardly rectifying potassium channel (Kir) 4.1 or the downstream with-no-lysine kinases (WNKs) and STE20/SPS1-related proline alanine-rich kinase (SPAK) pathway greatly attenuated, but did not prevent, salbutamol-induced NCC phosphorylation. Salbutamol increased cAMP in tubules, kidney slices and mpkDCT cells (model of DCT). Phosphoproteomics indicated that protein phosphatase 1 (PP1) was a key upstream regulator of salbutamol effects. A role for PP1 and the PP1 inhibitor 1 (I1) was confirmed in tubules using inhibitors of PP1 or kidney slices from I1 knockout mice. On normal and high salt diets, salbutamol infusion increased systolic blood pressure, but this increase was normalized by thiazide suggesting a role for NCC. Thus, β2-adrenergic receptor signaling modulates NCC activity via I1/PP1 and WNK-dependent pathways, and chronic salbutamol administration may be a risk factor for hypertension.

Over-the-counter antacids linked to severe hypokalaemia in the context of threatened preterm labour

A healthy multiparous woman presented at 35 weeks and 4 days' gestation with threatened preterm labour on multiple occasions. An incidental finding of severe hypokalaemia (2.4 mmol/L) was detected on routine blood tests. The cause of this hypokalaemia was not initially obvious. It was eventually linked to overuse of over-the-counter antacids for pregnancy-associated heartburn. The patient was managed with parenteral and then oral electrolyte replacement which corrected a pH of 7.55, bicarbonate of 36.7 mEq/L and a base excess 13.1. In this case report we consider whether hypokalaemia could be linked to uterine irritability and threatened preterm labour, whether antacids were being abused in the context of an eating disorder and the importance of taking a full drug history.

Safety and Efficacy of Tocolytics for the Treatment of Spontaneous Preterm Labour

BACKGROUND

Preterm birth is the major cause of perinatal mortality and morbidity worldwide. Attempts to reduce the burden may be proactive using biochemical or biophysical prediction and preventative measures. If these efforts fail, then the approach may have to be reactive using tocolytics to inhibit spontaneous preterm labour.

OBJECTIVE

We have reviewed the evidence concerning the safety and efficacy of various classes of tocolytic agents.

RESULTS

The evidence to support the use of magnesium sulfate or nitric oxide donors as a tocolytic is poor. Compared to placebo or no treatment, there is evidence to support the efficacy of calcium channel blockers (mainly nifedipine), prostaglandin synthetase inhibitors (mainly indomethacin and sulindac), oxytocin receptor antagonists (mainly atosiban) and β2-agonists (mainly ritodrine, terbutaline, salbutamol and fenoterol). Maternal safety concerns have reduced the use of β2-agonists. Fetal safety and gestational age restrictions have largely condemned prostaglandin synthetase inhibitors to second-line therapy. First-line therapy in Europe and other parts of the world outside the USA and Australia is limited to calcium channel blockers and oxytocin receptor antagonists. With respect to efficacy, atosiban and nifedipine are similar, but the robustness of the evidence favours atosiban. With respect to safety, atosiban is clearly the safest tocolytic as there are fetomaternal concerns with nifedipine, particularly in high daily doses.

CONCLUSION

The perfect tocolytic that is uniformly effective and safe does not exist. Cost, licensing and informed consent are considerations involved in the choice. Efforts continue to develop and introduce other or better agents, including novel compounds such as progesterone, PGF2α antagonists and statins.

Selective ß2-Adrenoceptor Agonists and Relevant Hyperlactatemia: Systematic Review and Meta-Analysis

Selective ß₂-agonists have been imputed as potential cause of l-hyperlactatemia since the 1970s. To document the prevalence of hyperlactatemia associated with selective ß₂-agonists and to investigate the predisposing factors, we searched for published articles until April 2019 pertaining to the interplay of administration of selective ß₂-agonists and circulating l-lactic acid in the Excerpta Medica, Web of Science, and the U.S. National Library of Medicine databases. Out of the 1834 initially retrieved records, 56 articles were included: 42 papers reporting individual cases, 2 observational studies, and 12 clinical trials. Forty-seven individual patients receiving a selective ß₂-agonist were found to have l-lactatemia ≥5.0 mmol/L, which decreased by ≥3.0 mmol/L or to ≤2.5 mmol/L after discontinuing (N = 24), reducing (N = 17) or without modifying the dosage of the selective ß₂-agonist (N = 6). Clinical trials found that l-lactic acid significantly increased in healthy volunteers administered a ß₂-agonist. l-lactatemia ≥5.0 mmol/L was observed in 103 (24%) out of 426 patients with asthma or preterm labor managed with a selective ß₂-agonist and was more common in patients with asthma (30%) than in premature labor (5.9%). A significant relationship was also noted between l-lactate level and intravenous albuterol dose or its circulating level. In conclusion, relevant l-hyperlactatemia is common on high dose treatment with a selective ß₂-agonist.

Blood potassium and urine aldosterone after doxapram therapy for preterm infants

OBJECTIVE

We often encounter infants who developed hypokalaemia following low-dose doxapram for apnea of prematurity (AOP).

AIMS

To determine changes in blood potassium (K+) levels after doxapram administration.

STUDY DESIGN

We studied infants born before 30 weeks gestation. Doxapram (0.1-0.3 mg/kg/h) in addition to methylxanthines was used to treat AOP refractory to methylxanthines.

RESULTS

Twenty-five infants received doxapram were studied. Fifty-two percent developed hypokalemia (<3.0 mEq/L) during doxapram administration. Time after starting doxapram to nadir blood K+ (<3.0 mEq/L) level was 11 days. Blood K+ levels normalized after 5 days of stopping doxapram administration. Data at 10 days before and after and at the time of doxapram administration were, respectively: lowest blood K+ level: 3.9, 3.0, and 3.6 mEq/L; urine aldosterone: 90, 206, and 146 pg/μg creatinine. Blood pH, blood pressure and urine volume were similar.

CONCLUSIONS

Doxapram-induced hypokalemia may be due to an inappropriate increase in aldosterone levels.

Periodic Paralysis and Encephalopathy as Initial Manifestations of Graves' Disease: Case Report and Review of the Literature

BACKGROUND

Thyrotoxic periodic paralysis (TPP) is an uncommon complication of Graves' disease, characterized by the triad of acute hypokalemia without total body potassium deficit, episodic muscle paralysis, and thyrotoxicosis. Graves' encephalopathy is an extremely rare form of encephalopathy associated with autoimmune thyroid disease (EAATD), characterized by neuropsychiatric symptoms, increased antithyroid antibodies and cerebrospinal fluid protein concentration, nonspecific electroencephalogram abnormalities, and cortico-responsiveness. Coexistence of both these complications in the same patient has not been reported before.

CASE REPORT

We herein present a 48-year-old white male patient with TPP and encephalopathy as initial presentations of Graves' disease. Flaccid tetraparesis was reversed a few hours after potassium level correction and the patient did not suffer any relapse with the successful pharmaceutical management of the thyroid function. One month later, the patient presented with dizziness and behavioral symptoms, such as inappropriate laughter and anger. Brain magnetic resonance imaging revealed meningeal enhancement and cerebrospinal fluid analysis showed a mild protein increase, with a blood-brain barrier disruption. With the suspicion of EAATD, the patient was treated with high doses of corticosteroids and improved dramatically.

CONCLUSIONS

To our knowledge this is the first reported coexistence of potentially treatable TPP and EAATD as initial neurological manifestations of Graves' disease, thereby underscoring the necessity of suspicion of possible underlying Graves' disease in patients with acute paralysis and encephalopathy of unclear origin.

Rebound hyperkalemia after cessation of ritodrine in a parturient undergoing cesarean section

A 36-year-old parturient with a suspicion of placenta accreta under tocolytic therapy with ritodrine infusion underwent emergency cesarean section under general anesthesia with propofol, ketamine, and remifentanil because massive bleeding was anticipated. The ritodrine infusion was discontinued 1 h before cesarean section. The baby was delivered 6 min after induction of anesthesia. However, after the manual removal of the placenta from the uterus, the bleeding was massive and uncontrollable. We rapidly transfused crystalloid, colloid, and red blood cells through potassium removal filter. Hyperkalemia (5.8 mmol/L) was detected just before blood transfusion. One hour later, hemostasis was still difficult, and hyperkalemia was promoted (6.1 mmol/L). Thus, glucose insulin therapy started with intravenous furosemide to treat hyperkalemia. Gynecologists decided to induce the Bakri balloon tamponade for the treatment of postpartum hemorrhage. At the end of surgery, plasma potassium level also reduced to 5.5 mmol/L. In the ICU, the bleeding still continued, and then radiologists performed bilateral internal iliac artery embolization for full hemostasis. Postoperative plasma potassium level was stable and 3.3 mmol/L in the next morning. Although one of the common adverse reactions of ritodrine is hypokalemia, we should also beware of a rebound hyperkalemia after its cessation.

Comparison of perinatal outcomes between long-term and short-term use of tocolytic agent: a historical cohort study in a single perinatal hospital

AIM

The aim of this study was to evaluate the effect of long-term use of tocolytic agents to prevent preterm delivery and improve perinatal outcome.

METHODS

A historical cohort study was performed in a single perinatal center. The maternal characteristics, frequency of preterm labor and prescribed dose of tocolytic agents were compared before and after changing the management protocol for threatened premature delivery.

RESULTS

A total of 1548 deliveries were carried out before changing the protocol for the use of tocolytic agents for threatened premature delivery and 1444 deliveries afterwards. There was no significant difference in the maternal characteristics before and after the revision except for maternal age. The total number of ritodrine hydrochloride ampules used was reduced from 4654 to 514, and the total vials of magnesium sulfate used were reduced from 1574 to 193, but perinatal outcomes, such as rate of preterm birth, neonatal weight, and rate of NICU hospitalization were not different between the groups.

CONCLUSION

There was no significant change in the frequency of preterm delivery before and after changing of the protocol for threatened premature delivery. Because a decrease in the given dose of tocolytic agents did not affect the timing of delivery and neonatal outcomes, long-term tocolysis in patients with threatened premature delivery should be restricted to prevent maternal and fetal adverse side-effects.

Case of thyrotoxic periodic paralysis in a caucasian male and review of literature

Objective. Thyrotoxic periodic paralysis (TPP), a known condition in Asian men, is becoming increasingly common in men from Western countries. Since suspicion for TPP as a differential in diagnosis is of utmost importance to avoid overcorrection of hypokalemia and other complications, we are reporting a case of TPP in a 25-year-old Caucasian male. Methods. The patient presented with intermittent lower extremity weakness after consumption of a large high-carbohydrate meal. Clinical examination revealed diffusely enlarged thyroid gland, no muscle power in lower extremities, tremors, and brisk deep tendon reflexes. Results. Clinical and laboratory findings were consistent with Graves' disease and the patient had hypokalemia. The patient responded to potassium repletion and was treated with propylthiouracil and propranolol. After treatment with radioactive iodine, the patient developed postablative hypothyroidism for which he was treated with levothyroxine. Conclusion. Since this condition is overlooked by physicians in Western countries, we present a case of TPP in a Caucasian male thus showing the importance of consideration of TPP in Caucasians despite its rare occurrence and the need for prompt diagnosis to avoid the danger of hyperkalemia in management of the paralytic attack in TPP patients.

Betamimetics for inhibiting preterm labour

BACKGROUND

Preterm birth is a major contributor to perinatal mortality and morbidity worldwide. Tocolytic agents are drugs used to inhibit uterine contractions. Betamimetics are tocolytic agents that have been widely used, especially in resource-poor countries.

OBJECTIVES

To assess the effects of betamimetics given to women with preterm labour.

SEARCH METHODS

We searched the Cochrane Pregnancy and Childbirth Group's Trials Register (31 December 2013) and reference lists of retrieved studies.

SELECTION CRITERIA

Randomised controlled trials of betamimetics, administered by any route or any dose, in the treatment of women in preterm labour where betamimetics were compared with other betamimetics, placebo or no treatment.

DATA COLLECTION AND ANALYSIS

Two review authors assessed risk of bias and extracted the data independently.

MAIN RESULTS

Twenty-eight trials were assessed as eligible for inclusion in the review, but eight did not report any outcome data relevant to the review. Results are based on the 20 trials that contributed data.Twelve trials, involving 1367 women, compared betamimetics with placebo. Betamimetics decreased the number of women in preterm labour giving birth within 48 hours (average risk ratio (RR) 0.68, 95% confidence interval (CI) 0.53 to 0.88, 10 trials, 1209 women). There was a decrease in the number of births within seven days (average RR 0.80; 95% CI 0.65 to 0.98, five trials, 911 women) but there was no evidence of a reduction in preterm birth (before 37 weeks' gestation) (RR 0.95; 95% CI 0.88 to 1.03, 10 trials, 1212 women). No benefit was demonstrated for betamimetics for perinatal death (RR 0.84; 95% CI 0.46 to 1.55, 11 trials, 1332 infants), or neonatal death (RR 0.90; 95% CI 0.27 to 3.00, six trials, 1174 infants). No significant effect was demonstrated for respiratory distress syndrome (RR 0.87; 95% CI 0.71 to 1.08, eight trials, 1239 infants). A few trials reported on cerebral palsy, infant death and necrotising enterocolitis; no significant differences between groups were identified for any of these outcomes. Betamimetics were significantly associated with the following outcomes: withdrawal from treatment due to adverse effects; maternal chest pain; dyspnoea; palpitation; tremor; headaches; hypokalaemia; hyperglycaemia; nausea or vomiting; nasal stuffiness; and fetal tachycardia.Nine trials compared different types of betamimetics. Other betamimetics were compared with ritodrine in five trials (n = 948). Other comparisons were examined in single trials: hexoprenaline compared with salbutamol (n = 140), slow versus moderate release salbutamol (n = 52) and salbutamol compared with terbutaline (n = 200). Trials were small, varied, and of insufficient quality to delineate any consistent patterns of effect.

AUTHORS' CONCLUSIONS

Betamimetics help to delay birth, which may give time to allow women to be transferred to tertiary care or to complete a course of antenatal corticosteroids. However, multiple adverse effects must be considered. The data are too few to support the use of any particular betamimetic.

Investigating the relationship between intra-operative electrolyte abnormalities (sodium and potassium) with post-operative complications of coronary artery bypass surgery

Background:

Generally, the electrolyte abnormalities are seen in many hospitalized patients, and this problem increases in ones with heart diseases. The purpose of this study is determination of the prevalence of electrolyte abnormalities during the coronary artery bypass surgery (CABG) and detecting the relationship between these abnormalities with the complications after the surgeries.

Materials and Methods:

This is a cross-sectional study, which is done in Chamran hospital, the medical and educational center of Isfahan, Iran, in 2011. The target population included the patients who have undergone CABG in this hospital. In this study, 100 patients who had been candidates for CABG were selected, and we extracted their recorded intra-operative electrolyte information. The collected data was entered into the computer and analyzed by SPSS software. The Chi-square and t student tests were used for data analysis.

Results:

The mean ± SD of sodium during CABG was 137.95 ± 4.6 (range 127-152) mg\dl. Also, the mean ± SD of potassium was 4.65 ± 0.9 (range: 2.9-7.4). According to these results, 48 patients (48% of all) had electrolyte imbalance and 52 patients (52% of all) were normal. Sodium level in 71% of patients was normal, and in 29% of them was abnormal. Potassium level in 73% of individuals was normal, and in 27% of them was abnormal.

Conclusion:

Giving an attention to electrolyte abnormalities in patients who have undergone CABG surgery is a considerable necessity for them, and sufficient arrangements are needed to prevent such abnormalities.

Treating acute asthma--salbutamol may not always be the right answer

β2 agonists are used as first-line treatment in acute asthma. However, they may paradoxically worsen respiratory failure through development of lactic acidosis

Thyrotoxic hypokalemic periodic paralysis: An overlooked pathology in western countries

Thyrotoxic hypokalemic periodic paralysis (THPP) is a complication of hyperthyroidism that is mostly diagnosed in Asian populations; consequently, it can be difficult to recognize in western populations. THPP represents an endocrine emergency that can result in respiratory insufficiency, cardiac arrhythmias, and death. Its differential diagnosis from the other more common forms of hypokalemic paralysis is important to avoid inappropriate therapy. Here, we discuss the main pathogenetic hypotheses, clinical features, and therapies of this disease. We also report an example of THPP management in our primary care unit.

Multicentre, parallel group, randomised, single-blind study of the safety and efficacy of atosiban versus ritodrine in the treatment of acute preterm labour in Korean women

OBJECTIVE

To compare the efficacy and safety of atosiban with those of ritodrine in preterm labour.

DESIGN

Multicentre, single-blind, randomised, controlled trial.

SETTING

Obstetric units in six referral centres in Korea.

POPULATION

Women with singleton pregnancies with preterm labour, between 24 and 33 + 6 weeks of gestation.

METHODS

One hundred and twenty-eight women were randomised to receive intravenous atosiban (n= 63) or ritodrine (n= 65) and were stratified by gestational age (<28 weeks and >or=28 weeks). Atosiban or ritodrine was administered for up to 48 hours. Progression of labour was assessed by the frequency of contractions and cervical dilatation and effacement. Alternative tocolysis could be given as rescue therapy.

MAIN OUTCOME MEASURE

Efficacy was assessed as the proportion of women in each group who did not deliver and did not need alternative tocolytic therapy at 48 hours and 7 days after therapy initiation. Safety was assessed as the numbers of maternal adverse events and neonatal morbidity.

RESULTS

Tocolytic efficacy after 7 days was significantly better in the atosiban group than in the ritodrine group (60.3 versus 34.9%), but not at 48 hours (68.3 versus 58.7%). Maternal adverse events related to therapy were reported less frequently in the atosiban group (7.9 vs 70.8%; P= 0.0001), resulting in fewer early drug terminations due to adverse events (0 versus 20.0%; P= 0.0001). This, however, was not accompanied by a concurrent improvement in perinatal outcomes.

CONCLUSION

The efficacy and safety of atosiban in the treatment of preterm labour were superior to those of ritodrine.

Pragmatic comparison of β2-agonist side effects within the Worldwide Atosiban versus Beta Agonists Study

OBJECTIVE

While beta2-agonists for the acute treatment of preterm labour unequivocally reduce the odds of delivery within 48 h and 7 days, they have been associated with substantial maternal and fetal side effects. We aimed to compare side effect profiles of beta2-agonist tocolytics.

STUDY DESIGN

Pragmatic comparison of ritodrine, salbutamol and terbutaline from re-analysis of data obtained within three comparator arms of three simultaneous comparable randomised controlled trials of beta2-agonists against atosiban in 742 women in preterm labour. The prevalence of categoric side effects between treatment groups was analysed using a chi2 test. The differences in continuous variables between treatment groups were analysed in analyses of covariance.

RESULTS

The prevalence of categoric side effects was similar with the three drugs, with the exception of the subjective symptom of palpitations (ritodrine 24.0%, terbutaline 9.3% and salbutamol 12.3%, P=0.003). There were also some differences in maternal diastolic blood pressure (P<0.001) and serum glucose levels (P<0.001), although these were small (<3 mmHg and < or =2.8 mmol/L, respectively) and clinically unimportant.

CONCLUSION

Side effects were common with all three drugs. Thus, choosing one beta2-agonist over the other to minimise side effects has little rationale, especially now that safer tocolytics are available.

Thyrotoxic periodic paralysis and anesthesia report of a case and literature review

Thyrotoxic periodic paralysis (TPP) is a disease characterized by recurrent episodes of paralysis and hypokalemia during a thyrotoxic state. The disease primarily affects people of Asian descent, but can affect other ethnic groups. In Asians, the symptoms of thyrotoxicosis are distinct and usually precede the first paralytic episode, whereas in non-Asian populations, paralysis is the presenting symptom. If TPP has not been diagnosed and the patient has a surgical procedure during general or regional anesthesia, symptoms of the disease may be confused with other adverse perioperative events such as delayed recovery from neuromuscular paralysis. No specific anesthetic regimen is superior. Current TTP treatment recommendations involve treating the underlying hyperthyroid state. Other modalities such as beta-blockade and potassium replacement are also important in the acute paralytic state. Future diagnostic and treatment innovations may lie in the genetic and molecular understanding of this disease. We present a case of an Asian male with known TPP undergoing general anesthesia, a brief case series involving 5 patients, and a review of the literature.

Safety of intravenous terbutaline in acute severe asthma: a retrospective study

OBJECTIVE

(1) To determine the effect of intravenous terbutaline in children with acute severe asthma on parameters like heart rate, blood pressure, electrocardiogram and serum electrolytes; (2) to assess the safety profile and to evaluate the outcome of children treated with intravenous terbutaline for acute severe asthma.

DESIGN

Retrospective study of admission records of children admitted with acute severe asthma who needed intravenous terbutaline.

SETTING

Children's Hospital at the Leicester Royal Infirmary, UK.

PATIENTS

77 children with acute severe asthma admitted between April 1999 and October 2002.

RESULTS

There was a significant increase in heart rate and significant fall in diastolic blood pressure in this cohort. Four patients required inotropic support. None of the patients had cardiac arrhythmias. Potassium supplements were required in 10 patients due to hypokalaemia. All patients improved and none required initiation of ventilation after commencing terbutaline. There was no mortality in this cohort.

CONCLUSIONS

Terbutaline was found to be safe for use in this patient group in doses ranging between 1 and 5 microg/kg/min. Intravenous terbutaline was found to be a useful adjunct in those who failed to respond to standard initial therapy.

Betamimetics for inhibiting preterm labour

BACKGROUND

Preterm birth is a major contributor to perinatal mortality and morbidity worldwide. Tocolytic agents are drugs used to inhibit uterine contractions. The most widely used tocolytic agents are betamimetics especially in resource-poor countries.

OBJECTIVES

To assess the effects of betamimetics given to women with preterm labour.

SEARCH STRATEGY

We searched the Cochrane Pregnancy and Childbirth Group trials register (May 2003) without language restrictions.

SELECTION CRITERIA

Randomised controlled trials of betamimetics, administered by any route or any dose, in the treatment of women in preterm labour where betamimetics are compared with other betamimetics, placebo or no treatment.

DATA COLLECTION AND ANALYSIS

Two reviewers evaluated independently methodological quality and extracted the data. We sought additional information to enable assessment of methodology and conduct intention-to-treat analyses. We present the results using the relative risk for categorical data and the weighted mean difference for continuous data.

MAIN RESULTS

Eleven randomised controlled trials, involving 1332 women, compared betamimetics with placebo. Betamimetics decreased the number of women in preterm labour giving birth within 48 hours (relative risk (RR) 0.63; 95% confidence interval (CI) 0.53 to 0.75) but there was no decrease in the number of births within seven days after carrying out a sensitivity analysis of studies with adequate allocation of concealment. No benefit was demonstrated for betamimetics on perinatal death (RR 0.84; 95% CI 0.46 to 1.55, 7 trials, n = 1332), or neonatal death (RR 1.00; 95% CI 0.48 to 2.09, 5 trials, n = 1174). No significant effect was demonstrated for respiratory distress syndrome (RR 0.87; 95% CI 0.71 to 1.08, 8 trials, n = 1239). A few trials reported the following outcomes, with no difference detected: cerebral palsy, infant death and necrotizing enterocolitis. Betamimetics were significantly associated with the following: withdrawal from treatment due to adverse effects; chest pain; dyspnoea; tachycardia; palpitation; tremor; headaches; hypokalemia; hyperglycemia; nausea/vomiting; and nasal stuffiness; and fetal tachycardia. Other betamimetics were compared with ritodrine in five trials (n = 948). Trials were small, varied and of insufficient quality to delineate any consistent patterns of effect.

REVIEWERS' CONCLUSIONS

Betamimetics help to delay delivery for women transferred to tertiary care or completed a course of antenatal corticosteroids. However, multiple adverse effects must be considered. The data are too few to support the use of any particular betamimetics.

Diagnosing thyrotoxic periodic paralysis in the ED

Thyrotoxic periodic paralysis (TPP) and sporadic periodic paralysis (SPP) are the most common causes of hypokalemic periodic paralysis (HPP) in EDs in Asia. Their neuromuscular presentations are almost indistinguishable. We conducted this study to identify clinical clues that can help EPs distinguish between TPP and SPP. Thirty-four patients presenting to the ED with HPP were enrolled during a 3-year period. They did not have known hyperthyroidism before the attack and no family history of paralysis. They all had low K(+) excretion rates. Vital signs and blood biochemistry, including acid-base and electrolytes, were measured. TPP was subsequently established by thyroid function tests. Twenty patients had TPP and 14 patients had SPP. There was no significant difference in age and sex distribution between them. Systolic (SBP) but not diastolic blood pressure (SBP 145 +/- 4 vs 128 +/- 4 mm Hg, P < 0.001) and heart rate (106 +/- 3 vs 73 +/- 3 beats/min, P < 0.001) were significantly higher in those experiencing TPP than SPP. Among the biochemical factors, only plasma phosphate concentration (2.2 +/- 0.2 vs 3.2 +/- 0.2 mg/dL, P < 0.001) was significantly lower in those experiencing TPP than SPP. Systolic hypertension, tachycardia, and hypophosphatemia are clinical clues favoring the diagnosis of TPP.

Rebound perioperative hyperkalemia in six patients after cessation of ritodrine for premature labor

IMPLICATIONS

This report describes six patients who had marked hyperkalemia 60-150 min after cessation of intravenous ritodrine, which had been administered for management of preterm labor. Abnormal electrocardiographic findings are very important clues for a prompt diagnosis of hyperkalemia.

Controversies in tocolytic therapy

In general, tocolytic agents are effective in stopping uterine contractions and in temporarily delaying delivery. The benefit of stopping uterine contractions is dependent on the fetal status and gestational age. The rationale for stopping preterm labor is to improve neonatal outcome. At this time, the best way to improve neonatal outcome would be to assure delivery in a center capable of caring for a preterm infant and prescription of glucocorticoids to decrease the risk of respiratory distress syndrome and other neonatal complications. Intravenous tocolysis for premature labor has found a prominent place in the obstetrician's armamentarium. We recommend the use of magnesium sulfate as first-line therapy. When comparing maternal and fetal risks, side effects, and the safety profile, magnesium sulfate is superior to beta-mimetics; however, there are still significant problems with potential morbidity and mortality for both mother and fetus with any tocolytics. Adjunctive use of indomethacin with magnesium sulfate may be used through 32 weeks for up to 48 hours at a time. Most tocolytics are effective in stopping labor for 48-72 hours. None have been shown to decrease the rate of preterm delivery. Once the uterus is quiescent and intravenous tocolytics are stopped, prolonged use of tocolytics has not been shown to be effective in preventing preterm birth. Tocolytics have significant long-term side effects to the mother's cardiovascular system, carbohydrate metabolism, and the fetal cardiovascular system. Thus, the prolonged use of prophylactic tocolytics after cessation of intravenous medications is not recommended. Tocolytics may be an appropriate therapy during preterm labor vaginal bleeding, ruptured membranes, multiple gestation, or advanced cervical dilatation. In all situations, however, careful guidelines must be observed. These guidelines include: (1) maternal and fetal well-being must be established before tocolytic therapy; (2) causes of preterm labor should be evaluated and treated when possible; (3) the risk/benefit ratio for both the mother and fetus must be re-evaluated on an ongoing basis; (4) when tocolytics are given before pulmonary maturity, then antenatal corticosteroids also should be considered in every case; (5) long-term use of tocolytics is difficult to justify at this time; (6) the safest tocolytic should be used for the shortest amount of time possible. It is doubtful, because of the nature of tocolytics, that newer tocolytics will be developed that will eliminate the problems of preterm delivery. Preterm delivery is an end-stage symptom of a multifactorial disease. Preterm labor is one of the last symptoms in a cascade of biochemical events that lead to preterm delivery. The most appropriate way to end preterm delivery would be to prevent the causes that initiate the cascade that ends in preterm labor. Authors' Note: Literally hundreds of papers have been written in the last 30 years on tocoloysis. For the purposes of space, when studies are summarized in peer-reviewed articles, we have referenced the reviews instead of the individual studies.