Plasma potassium response to acute respiratory alkalosis

Severe Respiratory Alkalosis during Hemodialysis

Respiratory alkalosis during hemodialysis session is a rare complication. We managed two patients with severe respiratory alkalosis, a woman who developed this 75 min after the beginning of the session and a man who developed it about 1 h before the end of the session. In both, the cause was a hypotensive episode, and both hypotension and alkalosis were successfully treated.

Lingering Altitude Effects During Piloting and Navigation in a Synthetic Cockpit

INTRODUCTION: A study was performed to evaluate a cockpit flight simulation suite for measuring moderate altitude effects in a limited subject group. Objectives were to determine whether the apparatus can detect subtle deterioration, record physiological processes throughout hypobaric exposure, and assess recovery.METHODS: Eight subjects trained to perform precision instrument control (PICT) flight and unusual attitude recovery (UAR) and completed chamber flights dedicated to the PICT and UAR, respectively. Each flight comprised five epochs, including ground level pressure (GLP), ascent through altitude plateaus at 10,000, 14,000, and 17,500 ft (3050, 4270, and 5338 m), then postexposure recovery. PICT performance was assessed using control error (FSE) and time-out-of-bounds (TOOB) when pilots exited the flight corridor. UARs were assessed using response times needed to initiate correction and to achieve wings-level attitude. Physiological indices included S_po₂, heart rate (HR), end tidal O₂ and CO₂ pressures, and respiration metrics.RESULTS: Seven subjects completed both flights. PICT performance deteriorated at altitude: FSE increased 33% at 17,513 ft and 21% in Recovery vs. GLP. Mean TOOB increased from 11 s at GLP to 60 s in Recovery. UAR effects were less clear, with some evidence of accelerated responses during and after ascent.CONCLUSIONS: The test paradigm was shown to be effective; piloting impairment was detected during and after exposure. Physiological channels recorded a combination of hypoxia, elevated ventilation, and hypocapnia during ascent, followed by respiratory slowing in recovery. Findings indicate precision piloting and respiration are subject to changes during moderate altitude exposure and may remain altered after S_po₂ recovers, and changes may be linked to hypocapnia.Beer J, Morse B, Dart T, Adler S, Sherman P. Lingering altitude effects during piloting and navigation in a synthetic cockpit. Aerosp Med Hum Perform. 2023; 94(3):135-141.

The Effects of Cold Exposure Training and a Breathing Exercise on the Inflammatory Response in Humans: A Pilot Study

OBJECTIVE

We previously showed that a training intervention comprising a combination of meditation, exposure to cold, and breathing exercises enables voluntary activation of the sympathetic nervous system, reflected by profoundly increased plasma epinephrine levels, and subsequent attenuation of the lipopolysaccharide (LPS)-induced inflammatory response. Several elements of the intervention may contribute to these effects, namely, two different breathing exercises (either with or without prolonged breath retention) and exposure to cold. We determined the contribution of these different elements to the observed effects.

METHODS

Forty healthy male volunteers were randomized to either a short or an extensive training in both breathing exercises by either the creator of the training intervention or an independent trainer. The primary outcome was plasma epinephrine levels. In a subsequent study, 48 healthy male volunteers were randomized to cold exposure training, training in the established optimal breathing exercise, a combination of both, or no training. These 48 participants were subsequently intravenously challenged with 2 ng/kg LPS. The primary outcome was plasma cytokine levels.

RESULTS

Both breathing exercises were associated with an increase in plasma epinephrine levels, which did not vary as a function of length of training or the trainer (F(4,152) = 0.53, p = .71, and F(4,152) = 0.92, p = .46, respectively). In the second study, the breathing exercise also resulted in increased plasma epinephrine levels. Cold exposure training alone did not relevantly modulate the LPS-induced inflammatory response (F(8,37) = 0.60, p = .77), whereas the breathing exercise led to significantly enhanced anti-inflammatory and attenuated proinflammatory cytokine levels (F(8,37) = 3.80, p = .002). Cold exposure training significantly enhanced the immunomodulatory effects of the breathing exercise (F(8,37) = 2.57, p = .02).

CONCLUSIONS

The combination of cold exposure training and a breathing exercise most potently attenuates the in vivo inflammatory response in healthy young males. Our study demonstrates that the immunomodulatory effects of the intervention can be reproduced in a standardized manner, thereby paving the way for clinical trials.Trial Registration:ClinicalTrials.gov identifiers: NCT02417155 and NCT03240497.

Bidirectional ventricular tachycardia induced by respiratory alkalosis mediated hypokalemia in a patient with acute ischemic heart failure

Bidirectional ventricular tachycardia (BVT) is a rare arrhythmia that is generally observed in patients with catecholaminergic ventricular tachycardia or digoxin overdose. Herein, we present a case of BVT and electrical storm (ES) in an acute ischemic heart failure patient that is typically induced by hypokalemia. The patient was in invasive mechanical ventilator (MV) support and hypokalemia was related to acute respiratory alkalosis and that caused refractory hypokalemia despite intravenous (IV) potassium replacement. We also discuss our approach to solve refractory hypokalemia caused by respiratory alkalosis.

Assessing and responding to anxiety and panic in the Emergency Department

Anxiety and panic symptoms are widespread in the general population. The physical manifestations of anxiety and panic commonly account for people presenting to Emergency Departments (EDs). It is therefore important for ED clinicians to be informed of the numerous causes of anxiety and panic and equipped to respond effectively. This paper describes the underlying pathophysiology of the physical symptoms of anxiety and panic and differential diagnoses to consider. Organic conditions that are associated with symptoms of anxiety and panic are highlighted. Brief interventions are tabled for ED clinicians to use when explaining symptoms, and to promote individual self-management.

The role of the clinical laboratory in diagnosing acid-base disorders

Acid-base homeostasis is fundamental for life. The body is exceptionally sensitive to changes in pH, and as a result, potent mechanisms exist to regulate the body's acid-base balance to maintain it in a very narrow range. Accurate and timely interpretation of an acid-base disorder can be lifesaving but establishing a correct diagnosis may be challenging. The underlying cause of the acid-base disorder is generally responsible for a patient's signs and symptoms, but laboratory results and their integration into the clinical picture is crucial. Important acid-base parameters are often available within minutes in the acute hospital care setting, and with basic knowledge it should be easy to establish the diagnosis with a stepwise approach. Unfortunately, many caveats exist, beginning in the pre-analytical phase. In the post-analytical phase, studies on the arterial reference pH are scarce and therefore many different reference values are used in the literature without any solid evidence. The prediction models that are currently used to assess the acid-base status are approximations that are mostly based on older studies with several limitations. The two most commonly used methods are the physiological method and the base excess method, both easy to use. The secondary response equations in the base excess method are the most convenient. Evaluation of acid-base disorders should always include the assessment of electrolytes and the anion gap. A major limitation of the current acid-base laboratory tests available is the lack of rapid point-of-care laboratory tests to diagnose intoxications with toxic alcohols. These intoxications can be fatal if not recognized and treated within minutes to hours. The surrogate use of the osmolal gap is often an inadequate substitute in this respect. This article reviews the role of the clinical laboratory to evaluate acid-base disorders.

Electrolyte and Acid-Base Disturbances in End-Stage Liver Disease: A Physiopathological Approach

Electrolyte and acid-base disturbances are frequent in patients with end-stage liver disease; the underlying physiopathological mechanisms are often complex and represent a diagnostic and therapeutic challenge to the physician. Usually, these disorders do not develop in compensated cirrhotic patients, but with the onset of the classic complications of cirrhosis such as ascites, renal failure, spontaneous bacterial peritonitis and variceal bleeding, multiple electrolyte, and acid-base disturbances emerge. Hyponatremia parallels ascites formation and is a well-known trigger of hepatic encephalopathy; its management in this particular population poses a risky challenge due to the high susceptibility of cirrhotic patients to osmotic demyelination. Hypokalemia is common in the setting of cirrhosis: multiple potassium wasting mechanisms both inherent to the disease and resulting from its management make these patients particularly susceptible to potassium depletion even in the setting of normokalemia. Acid-base disturbances range from classical respiratory alkalosis to high anion gap metabolic acidosis, almost comprising the full acid-base spectrum. Because most electrolyte and acid-base disturbances are managed in terms of their underlying trigger factors, a systematic physiopathological approach to their diagnosis and treatment is required.

Noninvasive blood potassium measurement using signal-processed, single-lead ecg acquired from a handheld smartphone

OBJECTIVE

We have previously used a 12-lead, signal-processed ECG to calculate blood potassium levels. We now assess the feasibility of doing so with a smartphone-enabled single lead, to permit remote monitoring.

PATIENTS AND METHODS

Twenty-one hemodialysis patients held a smartphone equipped with inexpensive FDA-approved electrodes for three 2min intervals during hemodialysis. Individualized potassium estimation models were generated for each patient. ECG-calculated potassium values were compared to blood potassium results at subsequent visits to evaluate the accuracy of the potassium estimation models.

RESULTS

The mean absolute error between the estimated potassium and blood potassium 0.38±0.32 mEq/L (9% of average potassium level) decreasing to 0.6 mEq/L using predictors of poor signal.

CONCLUSIONS

A single-lead ECG acquired using electrodes attached to a smartphone device can be processed to calculate the serum potassium with an error of 9% in patients undergoing hemodialysis.

SUMMARY

A single-lead ECG acquired using electrodes attached to a smartphone can be processed to calculate the serum potassium in patients undergoing hemodialysis remotely.

Opiate withdrawal complicated by tetany and cardiac arrest

Patients with symptoms of opiate withdrawal, after the administration of opiate antagonist by paramedics, are a common presentation in the emergency department of hospitals. Though most of opiate withdrawal symptoms are benign, rarely they can become life threatening. This case highlights how a benign opiate withdrawal symptom of hyperventilation led to severe respiratory alkalosis that degenerated into tetany and cardiac arrest. Though this patient was successfully resuscitated, it is imperative that severe withdrawal symptoms are timely identified and immediate steps are taken to prevent catastrophes. An easier way to reverse the severe opiate withdrawal symptom would be with either low dose methadone or partial opiate agonists like buprenorphine. However, if severe acid-base disorder is identified, it would be safer to electively intubate these patients for better control of their respiratory and acid-base status.

Voluntary activation of the sympathetic nervous system and attenuation of the innate immune response in humans

Excessive or persistent proinflammatory cytokine production plays a central role in autoimmune diseases. Acute activation of the sympathetic nervous system attenuates the innate immune response. However, both the autonomic nervous system and innate immune system are regarded as systems that cannot be voluntarily influenced. Herein, we evaluated the effects of a training program on the autonomic nervous system and innate immune response. Healthy volunteers were randomized to either the intervention (n = 12) or control group (n = 12). Subjects in the intervention group were trained for 10 d in meditation (third eye meditation), breathing techniques (i.a., cyclic hyperventilation followed by breath retention), and exposure to cold (i.a., immersions in ice cold water). The control group was not trained. Subsequently, all subjects underwent experimental endotoxemia (i.v. administration of 2 ng/kg Escherichia coli endotoxin). In the intervention group, practicing the learned techniques resulted in intermittent respiratory alkalosis and hypoxia resulting in profoundly increased plasma epinephrine levels. In the intervention group, plasma levels of the anti-inflammatory cytokine IL-10 increased more rapidly after endotoxin administration, correlated strongly with preceding epinephrine levels, and were higher. Levels of proinflammatory mediators TNF-α, IL-6, and IL-8 were lower in the intervention group and correlated negatively with IL-10 levels. Finally, flu-like symptoms were lower in the intervention group. In conclusion, we demonstrate that voluntary activation of the sympathetic nervous system results in epinephrine release and subsequent suppression of the innate immune response in humans in vivo. These results could have important implications for the treatment of conditions associated with excessive or persistent inflammation, such as autoimmune diseases.

Errors in potassium measurement: a laboratory perspective for the clinician

Errors in potassium measurement can cause pseudohyperkalemia, where serum potassium is falsely elevated. Usually, these are recognized either by the laboratory or the clinician. However, the same factors that cause pseudohyperkalemia can mask hypokalemia by pushing measured values into the reference interval. These cases require a high-index of suspicion by the clinician as they cannot be easily identified in the laboratory. This article discusses the causes and mechanisms of spuriously elevated potassium, and current recommendations to minimize those factors. "Reverse" pseudohyperkalemia and the role of correction factors are also discussed. Relevant articles were identified by a literature search performed on PubMed using the terms "pseudohyperkalemia," "reverse pseudohyperkalemia," "factitious hyperkalemia," "spurious hyperkalemia," and "masked hypokalemia."

Association of smoking, sleep apnea, and plasma alkalosis with nocturnal ventricular arrhythmias in men with systolic heart failure

BACKGROUND

Excess sudden death due to ventricular tachyarrhythmias remains a major mode of mortality in patients with systolic heart failure. The aim of this study was to determine the association of nocturnal ventricular arrhythmias in patients with low ejection fraction heart failure. We incorporated a large number of known pathophysiologic triggers to identify potential targets for therapy to reduce the persistently high incidence of sudden death in this population despite contemporary treatment.

METHODS

Eighty-six ambulatory male patients with stable low (≤ 45%) ejection fraction heart failure underwent full-night attendant polysomnography and simultaneous Holter recordings. Patients were divided into groups according to the presence or absence of couplets (paired premature ventricular excitations) and ventricular tachycardia (VT) (at least three consecutive premature ventricular excitations) during sleep.

RESULTS

In multiple regression analysis, four variables (current smoking status, increased number of arousals, plasma alkalinity, and old age) were associated with VT and two variables (apnea-hypopnea index and low right ventricular ejection fraction) were associated with couplets during sleep.

CONCLUSIONS

We speculate that cessation of smoking, effective treatment of sleep apnea, and plasma alkalosis could collectively decrease the incidence of nocturnal ventricular tachyarrhythmias and the consequent risk of sudden death, which remains high despite the use of β blockades.

Pathophysiology and management of hypokalemia: a clinical perspective

Potassium (K(+)) ions are the predominant intracellular cations. K(+) homeostasis depends on external balance (dietary intake [typically 100 mmol per day] versus excretion [95% via the kidney; 5% via the colon]) and internal balance (the distribution of K(+) between intracellular and extracellular fluid compartments). The uneven distribution of K(+) across cell membranes means that a mere 1% shift in its distribution can cause a 50% change in plasma K(+) concentration. Hormonal mechanisms (involving insulin, β-adrenergic agonists and aldosterone) modulate K(+) distribution by promoting rapid transfer of K(+) across the plasma membrane. Extrarenal K(+) losses from the body are usually small, but can be marked in individuals with chronic diarrhea, severe burns or prolonged sweating. Under normal circumstances, the kidney's distal nephron secretes K(+) and determines final urinary excretion. In patients with hypokalemia (plasma K(+) concentration <3.5 mmol/l), after the exclusion of extrarenal causes, alterations in sodium ion delivery to the distal nephron, mineralocorticoid status, or a specific inherited or acquired defect in distal nephron function (each of which affects distal nephron K(+) secretion), should be considered. Clinical management of hypokalemia should establish the underlying cause and alleviate the primary disorder. This Review aims to inform clinicians about the pathophysiology and appropriate treatment for hypokalemia.

Secondary responses to altered acid-base status: the rules of engagement

Each of the four canonical acid-base disorders expresses as a primary change in carbon dioxide tension or plasma bicarbonate concentration followed by a secondary response in the countervailing variable. Quantified empirically, these secondary responses are directional and proportional to the primary changes, run a variable time course, and tend to minimize the impact on body acidity engendered by the primary changes. Absence of an appropriate secondary response denotes the coexistence of an additional acid-base disorder. Here we address the expected magnitude of the secondary response to each cardinal acid-base disorder in humans and offer caveats for judging the appropriateness of each secondary response.

The effect of changes in arterialPCO2on neuroendocrine function in man

There is evidence that changes in arterial P(CO(2)) (P(a,CO(2))), as well as P(O(2)), influence neuroendocrine function. The hyponatraemia and fluid retention (cor pumonale) seen in chronic obstructive pulmonary disease (COPD) and type II respiratory failure is associated with increased vasopressin release. This study examines the specific effects of altered P(a,CO(2)) on hormone release from the posterior and anterior pituitary. The study was performed in 20 ventilated ICU patients in the late recovery phase of their illness. None had primary respiratory disease. Control blood samples were taken and the alveolar ventilation was then adjusted to allow the P(a,CO(2)) increase or decrease for a period of 3 h, during which time further blood samples were taken for the determination, by radioimmmunoassy of vasopressin, oxytocin, growth hormone and cortisol. Urine output and electrolyte concentrations were also measured. Circulating concentrations of growth hormone and oxytocin increased with increasing P(a,CO(2)). Vasopressin release showed a similar pattern up to a P(a,CO(2)) of approximately 6.0 kPa, above which vasopressin concentrations were inversely related to P(a,CO(2)). There was no significant effect on cortisol concentrations. No significant effects were established in urinary parameters during the short period of this study. Thus an increase in CO(2) is associated with stimulated pituitary hormone release. The effect on the neurohypophysial hormones may account for the fluid retention and hyponatraemia seen in COPD and hence provide a rationale for treatment.

Respiratory alkalosis and associated electrolytes in long-term ventilator dependent persons with tetraplegia

STUDY DESIGN

A pilot case control study of the acid-base and electrolyte status in 30 long-term ventilator-dependent (LTVD) and 30 self ventilating persons with tetraplegia.

OBJECTIVES

To assess the extent of respiratory alkalosis and screen for associated hypokalaemia, hypomagnesaemia and/or hypophosphataemia.

SETTING

Medically stable persons with tetraplegia under the long-term care of the Southport Spinal Injuries Centre, England.

METHODS

Blood gases and electrolytes were sampled from 30 control patients with tetraplegia and from 30 patients having been LTVD for more than 12 months.

RESULTS

All the blood gas measurements in the LTVD group lay outside both the reference range and the 95% confidence intervals (CI) of the control group: pH 7.46 (0.06); PCO(2) 3.46 (1.1) kPa; bicarbonate 18.3 (3.8) and base excess -3.2 (2.8) mmol/l; PO(2) 13.8 (2.8) kPa (means and standard deviations). The serum potassium, magnesium, phosphate, and sodium means lay within the reference ranges but the potassium, phosphate and calcium were at or below the 95% CI of the control values. One patient on part-time ventilatory support having less bicarbonate compensation had low serum electrolytes during ventilation.

CONCLUSION

There was no evidence of biochemical jeopardy from long-term mechanical hyperventilation although acutely administered hyperventilation has the potential to cause falls in serum potassium, magnesium and phosphate and so caution should be exercised in part-time ventilated persons. The full range of electrolytes should be assayed during stabilisation in LTVD and periodically thereafter. Hyperventilation helps to maintain good oxygenation in LTVD persons with paralysis and normal lungs.

SPONSORSHIP

None.

Factitious hyperkalemia

Pseudohyperkalemia, or factitious hyperkalemia, constitutes an artificially high plasma potassium level (P(K)) from a variety of possible causes. Occasionally, the cause cannot be elucidated. Three patients who showed unusually large differences between free-flowing and tourniquet (stasis) potassium levels prompted us to investigate the influence of tourniquets in routine phlebotomy in eight healthy volunteers. P(K) showed a consistent but rather small average increase of 0.2 mEq/L (P < 0.001) during tourniquet use; however, the range was 10-fold, from 0.05 to 0.5 mEq/L in our subjects. We suggest there may be large variability leading to an excessive increase in P(K) in some individuals. In the three patients presented, average excessive increases in P(K) of 1.6, 1.3, and 1.7 mEq/L were seen. Although diagnosing and treating true hyperkalemia remains paramount, recognizing factitious hyperkalemia is important to preclude unnecessary investigations and potentially hazardous intervention.

Opioid peptide modulation of circulatory response to hyperventilation in humans

After hyperventilation, systolic blood pressure (SBP) significantly decreased in 10 subjects (group 1), did not change in eight (group 2) and increased in 15 (group 3). Diastolic blood pressure and heart rate increased in all groups. The decrease in SBP was associated with a decrease in plasma catecholamines and increase in beta-endorphin, whereas the increase in SBP was accompanied by an increase in catecholamine and Met-enkephalin levels. Naloxone abolished the hyperventilation-induced SBP and catecholamine decrease only in group 1. These findings show an activation of the endogenous opioid system after hyperventilation and the role of beta-endorphin in reducing SBP in response to the test.

The effects of respiratory alkalosis and acidosis on net bicarbonate flux along the rat loop of Henle in vivo

We have studied the effects of acute respiratory alkalosis (ARALK, hyperventilation) and acidosis (ARA, 8% CO2), chronic respiratory acidosis (CRA; 10% CO2 for 7-10 days), and subsequent recovery from CRA breathing air on loop of Henle (LOH) net bicarbonate flux (JHCO3) by in vivo tubule microperfusion in anesthetized rats. In ARALK blood, pH increased to 7.6, and blood bicarbonate concentration ([HCO3-]) decreased from 29 to 22 mM. Fractional urinary bicarbonate excretion (FEHCO3) increased threefold, but LOH JHCO3 was unchanged. In ARA, blood pH fell to 7.2, and blood [HCO3-] rose from 28 to 34 mM; FEHCO3 was reduced to < 0.1%, but LOH JHCO3 was unaltered. In CRA, blood pH fell to 7.2, and blood [HCO3-] increased to > 50 mM, whereas FEHCO3 decreased to < 0.1%. JHCO3 was reduced by approximately 30%. Bicarbonaturia occurred when CRA rats breathed air, yet LOH JHCO3 increased (by 30%) to normal. These results suggest that LOH JHCO3 is affected by the blood-to-tubule lumen [HCO3-] gradient and HCO3- backflux. When the usual perfusing solution at 20 nl/min was made HCO3- free, mean JHCO3 was -34.5 +/- 4.4 pmol/min compared with 210 +/- 28.1 pmol/min plus HCO3-. When a low-NaCl perfusate (to minimize net fluid absorption) containing mannitol and acetazolamide (2 x 10(-4) M, to abolish H(+)-dependent JHCO3) was used, JHCO3 was -112.8 +/- 5.6 pmol/min. Comparable values for JHCO3 at 10 nl/min were -35.9 +/- 5.8 and -72.5 +/- 8.8 pmol/min, respectively. These data indicate significant backflux of HCO3-along the LOH, which depends on the blood-to-lumen [HCO3-] gradient; in addition to any underlying changes in active acid-base transport mechanisms, HCO3- permeability and backflux are important determinants of LOH JHCO3 in vivo.