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PubMed1983

Relative effects of systemic pH, PCO2, and bicarbonate concentration on ileal ion transport.

To determine the relative effects of systemic pH, CO2 tension (PCO2), and bicarbonate concentration on ileal electrolyte transport, states of acute metabolic acidosis and alkalosis were created in Sprague-Dawley rats by gavage feeding (NH4)2SO4 and NaHCO3, respectively. During in situ perfusion of the ileum in anesthetized animals, electrolyte transport was measured before and after respiratory compensation of the systemic pH. Acute respiratory acidosis and alkalosis also were studied by ventilating animals with 0, 3, or 8% CO2. When animals in all groups were considered, net sodium absorption correlated very well with blood pH (r = -0.97). Net bicarbonate secretion correlated with the plasma bicarbonate concentration (r = 0.91) independently of blood pH and PCO2. Net chloride absorption correlated with blood PCO2 (r = 0.92) and was altered when systemic pH and bicarbonate concentration changed in opposite directions. Alterations in luminal pH and PCO2 did not affect electrolyte transport. These results suggest that systemic pH affects a sodium chloride absorptive process and that the plasma bicarbonate concentration affects a chloride absorptive-bicarbonate secretory exchange process in the rat ileum.

Acid-Base Imbalance↗
PubMed1985

Intracellular K+ and Na+ activities under hypoxia, acidosis, and no glucose in dog hearts.

To gain a better understanding of the ionic mechanisms responsible for the electrophysiological disturbances occurring during myocardial ischemia, transmembrane potentials and intracellular potassium (aiK) and sodium (aiNa) ion activities were measured under individual and combined conditions of hypoxia (Po2 less than 50 mmHg), respiratory acidosis (pH 6.6), and no glucose in isolated epicardial ventricular muscle preparations of the canine heart using conventional and ion-selective microelectrode techniques. After 30 min superfusion with hypoxic, acidic, and glucose-free solution under 2-Hz stimulation, resting membrane potential (RMP) was significantly reduced from -85.5 +/- 0.6 to -69.5 +/- 1.0 mV, accompanied by decreases in action potential amplitude, maximum upstroke velocity of phase O, and action potential duration. aiK was significantly decreased from 101.0 +/- 5.6 to 79.5 +/- 5.8 mM, whereas aiNa was not significantly altered by the combined condition. RMP and aiK were moderately decreased by hypoxia alone, slightly decreased by acidosis, and hardly affected by the glucose-free condition. The extent of depolarization was well correlated with the decrease in aiK. These results suggest that Na+-K+ pump inhibition may not be a major cause of K+ efflux from myocardial cells under the hypoxic, acidic, and glucose-free condition and that hypoxia is the most important factor affecting aiK and RMP among these conditions.

Acidosis↗
PubMed1987

Hypoxic ventilatory control in the awake cat five years after carotid body resection.

Steady state breathing patterns, alveolar gases, and arterial blood gases and pH were measured during air, acute hypoxia, and acute hyperoxia in four awake cats 5 years after combined carotid body resection (CBR) and aortic depressor nerve section. Steady state breathing patterns and alveolar gases were also measured in these animals following 3 days of hypoxia (PIO2 = 110 Torr). The results show that the awake cat without carotid bodies and aortic depressor nerves hypoventilates during normoxia in relation to intact cats. Acute hypoxia resulted in respiratory acidosis, decreased tidal volume (VT), and decreased breath duration (TTOT). Exposure to hypoxia for three days resulted in no hyperventilation (isocapnia) but increased VT and TTOT from their levels during acute hypoxia. Acute hyperoxia resulted in respiratory alkalosis and increased VT. Moderate degrees of acute inspiratory hypoxia (FIO2 less than 0.12) induced a behavioral 'arousal' in these cats; this is in direct contrast to the lack of response seen shortly after CBR. Presumably, the recrudescence of chemosensitivity via unsectioned aortic chemoreceptor afferents played a key role in the arousal responses. However, there is no evidence in the cat for recrudescent chemoreceptor input to the respiratory control system with measurable steady state effect. We conclude that the peripheral chemoreceptors are essential for normal resting ventilatory control and for acclimation to chronic hypoxia.

Adaptation, Physiological↗
PubMed1992

Electrolyte and acid-base changes with massive blood transfusions.

The case records of 471 patients with massive transfusions of ten or more units of bank blood within 24 hours were reviewed to analyze the electrolyte and acid-base changes. The patients who lived had a less severe acidosis (7.23 +/- 0.15 vs 7.11 +/- 0.17) and the HCO3 was higher (19.8 +/- 15.2 vs 13.4 +/- 6.8) (P less than 0.001). The mean anion gap, despite the low HCO3, was 11.8 +/- 7.8 mEq/L. A combined metabolic and respiratory acidosis, often following bicarbonate therapy, was fetal in 83 per cent (39/47). Serum potassium values (K) were high in 22 per cent and low in 18 per cent of patients. If potassium levels were "corrected" by subtracting 0.5 mEq/L for each 0.1 pH of metabolic acidosis, only 5 per cent of patients were hyperkalemic. Patients dying within 48 hours of the massive transfusions had higher potassium levels (4.9 +/- 1.1 vs 4.4 +/- 0.9; P less than 0.001). Ionized calcium levels (Ca++) were less than normal (1.13-1.32 mmol/L) in 94 per cent of patients and were very low (less than 0.70 mmol/L) in 46 per cent (108/234). The mortality rate with severe ionic hypocalcemia was 71 per cent (vs 40% in patients with more normal values); P less than 0.0001. pH, PCO2, K, and Ca++ must be followed closely with massive transfusions. Rapid correction of volume and pH, without overcorrection, is essential.

Blood Gas Analysis↗
PubMed1994

Compensatory mechanisms in rats with nasal obstructions.

This study, in rats was designed to demonstrate the changes in respiratory dynamics in compensation for nasal obstructions. The experiment was performed on 30 rats. Fifteen rats served as the study group while another 10 rats served as controls. Five of the 30 rats were operated on to find out whether they would live and if so, for how long. Mouth breathing caused acute respiratory acidosis and marked aerophagia, leading to spontaneous death of the five experimental animals 90 to 100 hours postoperatively. Stenosis of the oropharyngeal airway due to palatal-epiglottic approximation, is supposed to be responsible for the respiratory insufficiency in nasally-obstructed rats. The compensatory changes in respiratory mechanics caused by high oropharyngeal airway resistance, together with some possible reflex changes, may have caused air swallowing. It is supposed that the increased air volume in the stomach and guts, causing elevation of the diaphragm and a paralytic ileus, contributed to mortality. No signs of aspiration were observed in these animals. After the surgical obstruction of both nostrils, changes in acid-base balance occurred in the 15 study rats 24, 48, and 72 hours postoperatively. On the first, second, and third days, a decrease in pO2 and pH, an increase in pCO2, and a compensatory increase in serum bicarbonate was observed.

Animals↗
PubMed1990

Seizures related to severe hypophosphataemia induced by mechanical ventilation.

A patient with chronic obstructive pulmonary disease and acute respiratory failure developed grand mal seizures in the hours following onset of mechanical ventilation. These seizures were associated with an acute increase in arterial pH and were related to the occurrence of acute severe hypophosphataemia associated with recovery from respiratory acidosis.

Aged↗
PubMed1984

Relative effects of systemic pH, PCO2, and HCO3 concentration on colonic ion transport.

To determine the relative effects of systemic pH, PCO2, and bicarbonate concentration on colonic electrolyte transport, states of acute metabolic acidosis and alkalosis were created in Sprague-Dawley rats by gavage feeding (NH4)2SO4 and NaHCO3, respectively. During in situ perfusion of the distal colon in pentobarbital-anesthetized animals, electrolyte transport was measured before and after respiratory compensation of the systemic pH. Acute respiratory acidosis and alkalosis also were studied by ventilating animals with 0, 3, or 8% CO2. When animals in all groups were considered, net sodium absorption correlated well with blood PCO2 (r = 0.99) but not with blood pH. Net bicarbonate secretion correlated with the plasma (r = 0.95) and luminal (r = -0.63) bicarbonate concentrations but not with blood pH or PCO2. Net chloride absorption correlated with both blood PCO2 (r = 0.92) and the plasma bicarbonate concentration (r = 0.80). These results suggest that systemic PCO2 affects a sodium chloride absorptive process and that the plasma bicarbonate concentration affects a chloride absorptive-bicarbonate secretory exchange process in the rat colon.

Acidosis↗
PubMed2003

Usefulness of helium-oxygen mixtures in the treatment of mechanically ventilated patients.

The density of helium is markedly lower than that of air or any of its components, leading to a substantial decrease in airway resistance to flow when it is inhaled. In mechanically ventilated patients with obstructive airway disease, replacing the usual air-oxygen mixture with helium-oxygen has been shown to reduce dynamic hyperinflation and intrinsic positive end-expiratory pressure; to decrease lung inflation pressures, respiratory acidosis, and work of breathing; and to improve arterial blood gases. Aerosol delivery to distal airways is enhanced with helium-oxygen. Preliminary data also suggest that the use of helium-oxygen could be a valuable approach to decrease postextubation respiratory distress. However, interference with ventilator function and added costs are two major disadvantages of helium-oxygen. Hence, before its widespread use in mechanically ventilated patients can be recommended, studies are needed to determine whether these favorable short-term effects can influence patient outcome.

Helium↗
PubMed1977

The relationship of respiratory failure to the oxygen consumption of, lactate production by, and distribution of blood flow among respiratory muscles during increasing inspiratory resistance.

An animal model was developed to determine if blood flow to the respiratory muscles limits oxygen delivery and thus work output during inspiratory resistance. With incremental increases in the rate of work of breathing to 15 times the resting level, blood flow to the diaphragm rose exponentially 26-fold. Blood flow to other inspiratory and a few expiratory muscles increased to a much smaller extent, often only at the greater work loads. Cardiac output and blood pressure did not change. Arterial-venous oxygen content difference across the diaphragm became maximal at low work rates and thereafter all increases in oxygen delivery during higher work rates were accomplished by increments in blood flow. Oxygen consumption of the respiratory musculature calculated by blood flow times oxygen extraction increased exponentially with increasing work of breathing and was less than the increase in total body oxygen consumption at each work load. Hypoxemia and respiratory acidosis occurred when the animals inspired through the highest resistance; blood flow and oxygen consumption were even higher than that observed during previous resistances and there was no evidence of a shift to anaerobic metabolsim in blood lactate and pyruvate levels. Respiratory failure did not appear to be a consequence of insufficient blood flow in this model.

Airway Resistance↗
PubMed1984

Metabolic and respiratory hydrogen ion effects on hypoxic pulmonary vasoconstriction.

Hypoxic pulmonary vasoconstriction (HPV) was studied in the ventilated-perfused rat lung in vitro. Respiratory acidosis and alkalosis were obtained by ventilating with 2, 7, or 10% CO2 (21% O2-balance N2). Metabolic acidosis and alkalosis were produced by the addition of 0.9 N NaHCO3 or 1 N lactic acid to the perfusate at constant PCO2. At each pH the pressor responses to 2 and 4% O2 were compared with the maximum pressor response (R%max) obtained with zero O2 and 5% CO2 at a normal pH (approximately 7.35). HPV was maximal when the [H+] was between 38 and 50 nM and was attenuated by changes of pH in either direction. Both respiratory and metabolic pH changes had similar effects. The combined linear regression equations were as follows: with 2% O2 the response to acidosis was R%max = 101.37 - 0.52 [H+] and to alkalosis was R%max = 2.03 [H+] - 3.85; with 4% O2 the response to acidosis was R%max = 56.88 - 0.3 [H+] and to alkalosis was R%max = 1.16 [H+] - 4.95. These effects were not due to changes of ionized calcium.

Animals↗
PubMed2002

Analysis of performance in orienteering with treadmill tests and physiological field tests using a differential global positioning system.

The aim of this study was to determine the physiological responses to orienteering by examining the interrelationships between the information provided by a differential global positioning system (dGPS) about an orienteer's route, speed and orienteering mistakes, portable metabolic gas analyser data during orienteering and data from incremental treadmill tests. Ten male orienteers completed a treadmill threshold test and a field test; the latter was performed on a 4.3 km course on mixed terrain with nine checkpoints. The anaerobic threshold, threshold of decompensated metabolic acidosis, respiratory exchange ratio, onset of blood lactate accumulation and peak oxygen uptake (VO2peak) were determined from the treadmill test. Time to complete the course, total distance covered, mean speed, distance and timing of orienteering mistakes, mean oxygen uptake, mean relative heart rate, mean respiratory exchange ratio and mean running economy were computed from the dGPS data and metabolic gas analyser data. Correlation analyses showed a relationship between a high anaerobic threshold and few orienteering mistakes (r = - 0.64, P < 0.05). A high threshold of decompensated metabolic acidosis and VO2peak were related to a fast overall time (r = -0.70 to -0.72, P < 0.05) and high running speed (r = 0.64 to 0.79, P < 0.05 and P < 0.01, respectively), and were thus the best predictors of performance.

Adult↗
PubMed1991

Acid-base balance in alcohol users seen in an emergency room.

Over 10% of emergency room patients are diagnosed as having alcohol (6.0%) or drug intoxication. In the present study 196 alcohol intoxications treated in a hospital were studied retrospectively; 49.2% of the patients had abnormal acid-base values, alcoholics more often than non-alcoholics (p = 0.04). Mean blood ethanol concentration (BAC) was 310 mg/dl (SD 120); alcoholics had higher concentrations of alcohol. BAC was the higher the lower the serum pH was (p less than 0.002, r = -0.45). The deeper the coma the lower the serum pH (p less than 0.05) and the higher the BAC (p less than 0.0001). Respiratory acidosis (31.7%) was an important finding in those intoxicated. Metabolic acidosis (7.9%) could be explained by the presence metabolites of ethanol in the serum and by decreased extra-cellular fluid volume. Metabolic alkalosis related to vomiting and an extra-cellular fluid volume decrease was found in 7.9% of the patients. Respiratory alkalosis was a rare finding (1.6%). Hypokalemia (22.5%) and hypernatremia (15.3%) were the most important electrolyte changes. Chronic alcoholics had lower serum potassium than had non-alcoholics; 3.6% (n = 7) of the patients had to be intubated. Acid-base disturbances were frequent in adults with alcohol intoxication. Serum pH correlated well with the state of consciousness and the BAC.

Acid-Base Equilibrium↗
PubMed1989

[Periodic sublingual buprenorphine for pain relief after upper abdominal surgery].

Analgesic effects were evaluated in patients who received sublingual administration of buprenorphine (0.2mg ampule for injection) as programmed every 8 hours for 3 days following upper abdominal surgery. Patients who received periodic sublingual buprenorphine obtained satisfactory postoperative analgesia and also required less analgesics than those who never received periodic administration of analgesics. Approximately one half of patients who received periodic sublingual buprenorphine required no additional analgesics. Arterial blood-gas analysis showed a significant increase in carbon dioxide tension after sublingual buprenorphine. One patient revealed marked respiratory acidosis after sublingual buprenorphine. These results suggest that periodic sublingual buprenorphine makes up for slow onset in sublingual administration and that it is also effective, convenient, and safe for pain relief after upper abdominal surgery. We, however, should pay attention to the respiratory depression caused by sublingual buprenorphine.

Abdomen↗
PubMed1998

[Acidosis and neuroprotection in two types of acidosis model rats under isoflurane anesthesia: evaluation of blood flow, pH and amino acid levels in the cortex].

In order to evaluate the effect of brain acidosis on neuronal functions as assessed by the in vivo studies, changes of cerebral blood flow (CBF), brain pH ([pH]o) and brain amino acid levels in the same brain region of the two different acidosis model rats were measured under isoflurane anesthesia. Three micro probes to measure CBF, [pH]o and amino acids, respectively, were implanted into the frontal cortex, and these parameters were recorded simultaneously. In the metabolic acidosis rats, the sustained decrease of [pH]o and amino acid levels, particularly Glu, were detected after the treatment with 10 min-i.v. infusion of 1 N HCl, although the significant changes of CBF did not appear because of the respiratory management. In the respiratory acidosis model, however, transient and significant increase of CBF and decrease of Glu and [pH]o were recorded after 10 min-exposure to about 30% CO2 (N2O:O2:CO2 = 2:5:3). The levels of Gly and Gln were reduced after acute exposure to hypercapnia, but these levels recovered to the control level in 20-30 min after hypercapnia exposure. In both animals, the amounts of Tau was gradually reduced after the treatment with 1 N HCl and hypercapnia, and these levels did not return to the control level when other amino acid levels had recovered. These differences of brain amino acid levels in the two different types of acidosis model rats may be related to the brain amino acid metabolic pathway. Thus, during brain acidosis induced by 1 N HCl and hypercapnia, the amount of extracellular Glu in the brain was reduced, and this reduction may contribute to the neuroprotective effects.

Acidosis↗
PubMed1991

"Near miss" death in obstructive sleep apnea: a critical care syndrome.

OBJECTIVE: The objective of this study was to alert critical care physicians to the syndrome of obstructive sleep apnea with respiratory failure ("near miss" death) and to elucidate characteristics that might allow earlier recognition and treatment of such patients. DESIGN: We examined clinical and laboratory characteristics of eight patients with obstructive sleep apnea presenting to the ICU with respiratory failure. These characteristics were compared with those of eight stable apnea patients of similar severity but without a history of presentation with respiratory failure. SETTING: Medical ICU and pulmonary outpatient clinic at the Houston Veterans Administration Medical Center, a teaching hospital affiliated with Baylor College of Medicine. PATIENTS: Eight patients with obstructive sleep apnea who presented in, or developed, acute respiratory failure requiring tracheal intubation and mechanical ventilation were matched to eight stable obstructive sleep apnea outpatients from the chest clinic. MEASUREMENTS AND MAIN RESULTS: The records of these 16 patients were reviewed and multiple characteristics that might predict these obstructive sleep apnea patients prone to respiratory failure and death (called the "near miss" death group; n = 8) were examined. The mean age of the near miss group was 57 yrs. All eight patients presented with respiratory acidosis (mean pH 7.22), hypercarbia (mean PaCO2 82 torr [10.9 kPa]), and hypoxemia (mean PaO2 45 torr [6.0 kPa]). Six of the eight patients had concomitant chronic obstructive pulmonary disease as determined by clinical characteristics and spirometry. Predisposing factors included facial trauma, lower respiratory tract infections or bronchospasm, and use of pain medication. All but one of the near miss subjects had awake hypercarbia (mean PaCO2 49 torr [6.5 kPa]) and hypoxemia (mean PaO2 58 torr [7.7 kPa]) during periods of clinical stability while only two controls had concomitant chronic obstructive pulmonary disease and none had hypercarbia. The prevalence of a history of wheezing and prior hospitalization for "respiratory problems" were greater in the near miss group. Once cured of apnea, no patient presented with recurrence of respiratory failure in follow-up ranging from 6 to 80 months, and cor pulmonale recurred in only one patient during subsequent onset of central apneas. CONCLUSION: Patients with obstructive sleep apnea who have concomitant chronic obstructive pulmonary disease or hypercarbia and hypoxemia are more prone to develop severe respiratory failure and probable death than those patients with apnea alone. The current study shows that recurrent respiratory failure and presumably mortality from this acute complication can be reversed with effective treatment of the obstructive apnea.

Acute Disease↗
PubMed1993

[Anesthetic management of a patient with carcinoid syndrome].

Anesthetic management of a 75-year-old female with carcinoid syndrome is reported. She had a tumor on the ileum and multiple metastatic tumors in the both lobes of the liver. Levels of both plasma serotonin and urinary 5-hydroxyindole acetic acid (5-HIAA) were significantly elevated before the operation. Although she was treated with somatostatin-analogue percutaneously, the levels of these hormones did not decrease significantly. The partial resection of the small intestine was scheduled under general anesthesia. Before induction of general anesthesia, hydrocortisone and ulinastatin were administered intravenously to prevent the release of chemical mediators. Anesthesia was induced with ketamine, diazepam, and vecuronium, and maintained with nitrous oxide, oxygen and enflurane. There was mild bronchospasm at the beginning of the surgery and the blood pressure was unstable during the operation, but anesthetic course was relatively uneventful. Although the patient recovered from anesthesia smoothly, she developed respiratory acidosis 45 minutes after extubation. She was intubated again and ventilated artificially with pressure support ventilation whose support level was 15 cmH2O for only three hours. We conclude that we should pay much attention not only during anesthesia but also after surgery, especially to respiratory system in patients with carcinoid syndrome.

Aged↗
PubMed1992

Intravascular membrane oxygenation and carbon dioxide removal--a new application for permissive hypercapnia?

Pressure limited ventilation or "lung rest" may prevent further exacerbation of acute lung injury from high airway pressures. A therapeutic goal of an intracorporeal oxygenation and carbon dioxide removal device (IVOX) is reduction of airway pressures. We noted increased IVOX CO2 removal as mixed venous CO2 increased in experimental animals. However, we recognize the limited clinical utility of removing approximately 30% of venous CO2. Therefore, intentional hypoventilation to limit airway pressures (mild permissive hypercapnia) was used in 5 patients with respiratory failure, and again we noted improved CO2 removal with increasing mixed venous CO2 concentrations. Preliminary calculations demonstrate that a CO2 gradient of approximately 70 mm Hg is needed to remove 100 ml CO2/min. The use of more aggressive permissive hypercapnia protocols with IVOX may permit further reduction in airway pressure without problems of severe respiratory acidosis.

Adolescent↗
PubMed2000

Noninvasive pressure support ventilation for acute respiratory failure in children.

Noninvasive ventilation is becoming widely accepted not only for treatment of chronic but also acute respiratory failure of various aetiology in children. However, thus far, there is only empirical evidence that this treatment is safe and effective in improving oxygenation and alveolar ventilation and in obviating endotracheal intubation in many cases. With this limited experience it is difficult to define the ideal candidate who will respond to a noninvasive ventilation trial. Infants and small children are at high risk of developing respiratory fatigue and, consecutively, respiratory failure due to structural and functional properties of their developing respiratory system. This may justify early noninvasive pressure support ventilation as soon as clinical signs of impending respiratory failure develop and before physiological evidence of acute respiratory failure with respiratory acidosis and/or hypoxaemia are present. For the success of noninvasive ventilation in the acute care setting, the correct choice and adaptation of the patient-machine interface and the delivery system are crucial. Furthermore, medical and nursing staff must be familiar with child-specific respiratory physiology and mechanics. Well controlled randomised prospective trials in children presenting with acute respiratory failure will be needed to evaluate the treatment's effectiveness and safety, and to better define the patient likely to benefit from this alternative method of respiratory support.

Acute Disease↗