Hyperventilation and finger exercise increase venous-arterial Pco2 and pH differences

Introduction

Since the invention of the pulse oximeter, physicians often or even routinely perform venous blood gas analysis (VBGA). However, it has not been generally agreed that the application of VBGA is practically meaningful in routine clinical situations such as in an ED.

Methods

We measured venous-arterial Pco₂ difference ((v-a)Pco₂) and arterial-venous pH difference ((a-v)pH), and analyzed the physiological factors that affect these differences in healthy volunteers and hyperventilation patients.

Results

In healthy volunteers, both (v-a)Pco₂ and (a-v)pH increased during finger exercise or hyperventilation in an intensity-dependent manner. Doppler echography indicated that increases in (v-a)Pco₂ and (a-v)pH during hyperventilation are induced by reduction of peripheral blood flow. Approximately 40% of patients with untreated respiratory alkalosis were found to be incorrectly diagnosed if based only on VBGA.

Conclusions

It must be noted that VBGA may lead to overestimation of acidosis and to underestimation of respiratory alkalosis when extremities muscles are active or patients are hyperventilating. Physicians should keep these limitations in mind when conducting VBGA.     

Effects of amlodipine and candesartan on arterial stiffness estimated by cardio-ankle vascular index in patients with essential hypertension: A 24-week study

Background: Aortic stiffness assessed by brachio-ankle pulse wave velocity (baPWV) can be used to predict cardiovascular events. However, baPWV is dependent on blood pressure. Antihypertensive drugs have been reported to reduce baPWV; but it is difficult to determine if this effect is associated with lowered blood pressure or reduced arterial stiffness.Objectives: The primary end point of this study was to assess whether antihypertensive drugs reduce arterial stiffness as estimated by cardio-ankle vascular index (CAVI). The secondary end point was to compare the effects of 2 widely used drugs, the calcium-channel blocker amlodipine and the angiotensin II receptor blocker candesartan, on arterial stiffness.Methods: Between October 2005 and September 2006, consecutive Japanese outpatients with essential hypertension (EHT) (defined as using antihypertensive drugs at screening, systolic blood pressure [SBP] > 140 mm Hg, or diastolic BP [DBP] >90 mm Hg) were assigned to treatment for 24 weeks with either amlodipine (5-10 mg/d) or candesartan (8-12 mg/d). Arterial stiffness was evaluated with CAVI before and after 24 weeks of treatment. Relative change in arterial stiffness from baseline was also compared. The evaluator was blinded to treatment.Results: Twenty patients (11 men, 9 women; mean [SD] age, 62 [10] years) were included in the study. There were no significant differences in clinical characteristics between the 2 groups. At baseline, mean (SD) CAVI was not significantly different in the amlodipine group compared with the candesartan group (8.93 [0.93] vs 8.46 [1.34], respectively). During the 24-week treatment period, mean SBP and DBP decreased significantly in both the amlodipine (14/10 mm Hg; P = 0.006 and P = 0.005) and the candesartan groups (13/11 mm Hg; P = 0.033 and P = 0.005). Amlodipine was associated with a significant change in CAVI from baseline (8.93 [0.93] vs 8.60 [1.50]; P = 0.017), whereas candesartan was not (8.46 [1.34] vs 8.81 [1.20]). The percentage change in CAVI was significantly different in the amlodipine group compared with the candesartan group (−7.14 [8.83] vs 5.85 [16.0], respectively; P = 0.038). After 24 weeks of treatment, the CAVI of the amlodipine group was still numerically larger than baseline CAVI of the candesartan group, although the difference was not statistically significant. Furthermore, there was no significant difference in absolute CAVI between the 2 groups after 24 weeks, but the relative change from baseline was significant in favor of amlodipine. Logistic regression analysis revealed that amlodipine improved CAVI independent of its antihypertensive effect.Conclusion: These data suggest that amlodipine and candesartan had different effects on aortic stiffness estimated by CAVI, despite similar effects on brachial blood pressure after 24 weeks of treatment in these Japanese patients with EHT.     

Renal sodium/calcium exchange; a vasodilator that is defective in salt‐sensitive hypertension

The Na⁺ : Ca²⁺ exchanger is an important plasma membrane ion transport pathway that plays a major role in controlling [Ca²⁺]_i. In smooth muscle cells, it may function as a Ca²⁺ extrusion pathway and may help lower [Ca²⁺]_i in response to vasoconstrictor‐induced increases in [Ca²⁺]_i. It may also extrude [Ca²⁺]_i and lead to vasodilation in response to vasodilators. Our recent studies have been performed to determine the existence and regulation of the Na⁺ : Ca²⁺ exchanger in renal contractile cells which include afferent and efferent arterioles and mesangial cells. Exchanger activity is present in all three of these contractile elements but is higher in afferent arterioles vs. efferent arterioles. We have also examined the role of altered regulation of the exchanger in the SHR and in salt‐sensitive hypertension. With the establishment of high blood pressure, Na⁺ : Ca²⁺ exchanger activity is reduced in afferent but not in efferent arterioles in both models of hypertension. Other works in cultured mesangial cells and freshly dissected afferent arterioles, have shown that protein kinase C (PKC) up‐regulates the Na⁺ : Ca²⁺ exchanger from Dahl/Rapp salt‐resistant rats while it fails to do so in arterioles and mesangial cells from salt‐sensitive rats. This defect in PKC regulation of Na⁺ : Ca²⁺ exchange is the result of a loss of PKC‐mediated translocation of the exchanger to the plasma membrane in S mesangial cells. Thus, a defect in the PKC‐Na⁺ : Ca²⁺ exchanger‐translocation pathway may cause dysregulation of [Ca²⁺]_i and help explain the dramatic decrease in GFR that occurs in this model of hypertension.     

Sterile versus clean urinary catheterisation is not associated with post-transplantation infection

The objective of this study is to determine if there was a difference in rate of post-transplantation urinary tract infection (UTI) in patients who have an indwelling catheter inserted using sterile versus clean technique. UTI is the most common nosocomial infection in the post-transplantation period. We aim to describe risk factors associated with postoperative UTI in our institution and determine if there was a difference between those who have an indwelling catheter inserted using sterile versus clean technique. Risk factors for UTIs can be divided into recipient, donor, and procedure related factors. While an indwelling urinary catheter increases the risk of infection, it is vital for post-operative fluid balance monitoring. Given the morbidity of UTIs in transplant recipients, a number of studies have investigated modifiable risk factors; however, investigation of the technique of indwelling catheter insertion at the time of renal transplantation is yet to be examined. A retrospective analysis of a contemporaneously maintained database was performed of renal transplant recipients over a 2-year period from 2019–2021. Patients were divided into sterile versus clean technique, defined as the use of sterile gloves, gown and fenestrated drape following a surgical scrub, or sterile gloves alone following the use of alcohol-based hand sanitiser respectively. A p value of <0.05 was considered statistically significant. One hundred sixty-nine patients were included in analysis, with 31 UTIs (18.3%) within 30 days of renal transplantation. Female gender and autosomal dominant polycystic kidney disease were associated with a higher rate of UTI. One hundred twenty-three patients had a catheter inserted via sterile technique, and 46 with clean technique, with no significant difference in rate of post-operative UTI (p = 0.52). Inserting an indwelling catheter either by sterile or clean technique at the time of renal transplantation was not associated with the rate of postoperative UTI within 30 days.     

SARS-CoV-2 outbreak among staff and evacuees at Operation Allies Welcome Safe Havens

We report on five SARS-CoV-2 congregate setting outbreaks at U.S. Operation Allies Welcome Safe Havens/military facilities. Outbreak data were collected, and attack rates were calculated for various populations. Even in vaccinated populations, there was rapid spread, illustrating the importance of institutional prevention and mitigation policies in congregate settings.     

Guidelines for the management of traumatic dental injuries. I. Fractures and luxations of permanent teeth

Crown fractures and luxations occur most frequently of all dental injuries. An appropriate treatment plan after an injury is important for a good prognosis. Guidelines are useful for delivering the best care possible in an efficient manner. The International Association of Dental Traumatology (IADT) has developed a consensus statement after a review of the dental literature and group discussions. Experienced researchers and clinicians from various specialties were included in the group. In cases where the data did not appear conclusive, recommendations were based on the consensus opinion of the IADT board members. The guidelines represent the current best evidence, based on literature research and professional opinion. In this first article of three, the IADT Guidelines for management of fractures and luxations of permanent teeth will be presented.