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PubMed2001

Gut blood flow in fish during exercise and severe hypercapnia.

This paper reviews the effects of exercise and hypercapnia on blood flow to the splanchnic circulation. Brief struggling behaviours are known to decrease blood flow to the gut (GBF). Likewise, prolonged swimming in unfed fish has been shown to reduce GBF in proportion to the increased oxygen uptake. Therefore, the normal postprandial increase in GBF theoretically should be impaired whenever fish are active. However, indirect evidence suggests that GBF is spared to some degree when fed fish swim continuously but at a cost (10-15%) to their critical swimming speed. Severe respiratory acidosis can be created by the new intensive aquaculture settings that use oxygen injection into re-circulated water. The only study so far to examine the effects of severe hypercapnia on GBF and its regulation showed that routine GBF and alpha-adrenergic control of GBF remained normal in unfed white sturgeon (Acipenser transmontanus). However, severe hypercapnia produced a hyperactive state and increased sensitivity of GBF to struggling. As a result, routine GBF was maintained for a short period of time. Thus, environmental changes such as severe hypercapnia can indirectly impact GBF through altered struggling behaviour, but the implications of the overall reduction in GBF to food assimilation have yet to be established.

Animals↗
PubMed2002

Effects of anaesthesia on blood gases, acid-base status and ions in the toad Bufo marinus.

It is common practice to chronically implant catheters for subsequent blood sampling from conscious and undisturbed animals. This method reduces stress associated with blood sampling, but anaesthesia per se can also be a source of stress in animals. Therefore, it is imperative to evaluate the time required for physiological parameters (e.g. blood gases, acid-base status, plasma ions, heart rate and blood pressure) to stabilise following surgery. Here, we report physiological parameters during and after anaesthesia in the toad Bufo marinus. For anaesthesia, toads were immersed in benzocaine (1 g l(-1)) for 15 min or until the corneal reflex disappeared, and the femoral artery was cannulated. A 1-ml blood sample was taken immediately after surgery and subsequently after 2, 5, 24 and 48 h. Breathing ceased during anaesthesia, which resulted in arterial Po(2) values below 30 mmHg, and respiratory acidosis developed, with arterial Pco(2) levels reaching 19.5+/-2 mmHg and pH 7.64+/-0.04. The animals resumed pulmonary ventilation shortly after the operation, and oxygen levels increased to a constant level within 2 h. Acid--base status, however, did not stabilise until 24 h after anaesthesia. Haematocrit doubled immediately after cannulation (26+/-1%), but reached a constant level of 13% within 24 h. Blood pressure and heart rate were elevated for the first 5 h, but decreased after 24 h to a constant level of approximately 30 cm H2O and 35 beats min(-1), respectively. There were no changes following anaesthesia in mean cellular haemoglobin concentration, [K+], [Cl-], [Na+], [lactate] or osmolarity. Toads fully recovered from anaesthesia after 24 h.

Acid-Base Equilibrium↗
PubMed2003

Midbrain serotonergic neurons are central pH chemoreceptors.

Serotonergic neurons in the medulla are central respiratory chemoreceptors. Here we show that serotonergic neurons in the midbrain of rats are also highly chemosensitive to small changes in CO2/pH and are closely associated with large penetrating arteries. We propose that midbrain raphé neurons are sensors of blood CO2 that maintain pH homeostasis by inducing arousal, anxiety and changes in cerebrovascular tone in response to respiratory acidosis.

Action Potentials↗
PubMed1998

Fatal obstructive lung disease after haploidentical sibling cord blood transplantation.

We report the case of a patient with fatal obstructive lung disease after an HLA-haploidentical sibling cord blood transplant (CBT), with severe acute GVHD. A 2-year-old girl developed expiratory air trapping gradually with acute and chronic GVHD after CBT for the treatment of ALL. Anti-CMV and immunosuppressive therapy were ineffective, and the patient died of progressive respiratory acidosis. Necropsy of the lung revealed severe bronchiolitis obliterans with cytomegalic inclusion cells in the granulation tissues of the bronchiolitis. Thus, immunologic and GVHD problems can occur even in CBT.

Bronchiolitis Obliterans↗
PubMed2000

Effects of magnesium sulfate in a newborn piglet meconium aspiration model.

OBJECTIVE: To examine the hemodynamic effects of magnesium sulfate (MgSO4) in a neonatal model of meconium aspiration syndrome. DESIGN: A prospective animal study. PATIENTS AND PARTICIPANTS: Eight anesthetized neonatal piglets. METHODS: Animals were instrumented under fentanyl anesthesia for the determination of pulmonary and systemic blood pressures and cardiac index. A model of meconium aspiration was produced by instilling 6 to 7 ml of 20% fresh human meconium in normal saline down the endotracheal tube, resulting in hypoxemia (mean arterial O2 saturation 73 SD, 10%), respiratory acidosis (mean pH 7.08, SD 0.04; PaCO2 89, SD 2 torr), and pulmonary arterial hypertension (mean pulmonary artery pressure 52 SD, 5 mm Hg). A total of four aliquots of MgSO4 (25 mg/kg equivalent to 0.1 mM/kg of magnesium) were administered intravenously to five animals (total of 100 mg/kg MgSO4). Three animals served as controls and did not receive MgSO4. RESULTS: Each dose of MgSO4 was associated with a transient decrease in heart rate, cardiac index, pulmonary and systemic arterial pressures, and SaO2, followed by a partial gradual recovery of all these variables within 2 to 3 minutes. According to measurements taken after MgSO4 therapy, there was a significant decrease in arterial saturations (from 73 SD (10%) to 63 SD (13%); p < 0.05), mean systemic blood pressure (from 77 SD (16 mm Hg) to 74 SD (15 mm Hg); p < 0.05) and pulmonary artery pressure (to 52 SD (5 mm Hg); p < 0.05). The ratio between pulmonary and systemic vascular resistance was not significantly affected by MgSO4 therapy. There were no changes in the control animals. CONCLUSION: The administration of magnesium sulfate is associated with increased hypoxemia in this model of meconium aspiration syndrome, probably because of worsening ventilation perfusion mismatch. These data do not provide any physiological support for the use of MgSO4 in the neonate with meconium aspiration and pulmonary hypertension and suggest that this agent should be used cautiously, if at all, in such situations.

Animals↗
PubMed1988

The influence of restraint and infusion on rates of muscle protein synthesis in the rat. Effect of altered respiratory function.

1. Male rats (110-140 g body wt.) were restrained by a standard laboratory technique, by wrapping in a linen towel, and subjected to a constant intravenous infusion of saline (0.15 M-NaCl) for periods of 1 or 6 h. Fractional rates of protein synthesis (ks, %/day) were estimated at the start and at the end of the infusion period, by injection of a large concentration of [3H]phenylalanine. 2. In fed and overnight-fasted rats, restraint and infusion of saline for 1 and 6 h decreased ks in skeletal muscle by 15-20% and 30-35% respectively. Plasma glucose, insulin, glucagon and corticosterone concentrations in restrained and infused rats were not characteristic of immobilization stress. 3. Restrained rats responded to nutrient administration; ks in skeletal muscle increased by 35-40% after infusion of a mixture of amino acids and glucose for 1 or 6 h, as compared with saline-infused rats. 4. Restraint and infusion for 1 or 6 h did not overtly decrease ks and kRNA (protein synthesis per unit of RNA) in hypoxaemia-sensitive tissues, such as heart and liver. Restraint and infusion in an open cage, or in a cloth of open weave, did not decrease ks in muscle after 1 h. Blood gas measurements showed that rats restrained in a linen cloth were hypercapnic and acidotic compared with rats in an open cage. 5. It was concluded that respiratory acidosis, rather than hypoxia, resulting from restraint in a linen cloth decreases muscle protein synthesis.

Animals↗
PubMed1982

Oedema in cor pulmonale.

The mechanisms of oedema in cor pulmonale remain unexplained. On the basis of a small number of studies, cor pulmonale is not caused by cardiac muscle failure, at least in early oedematous phases. Progressive and persistent elevation of pulmonary vascular resistance may exceed the pumping capacity of the right ventricle in later stages. Alternative explanations for the sharp fall in renal blood flow as oedema appears should be sought. The renin-angiotensin-aldosterone system seems causally related to oedema. The curious position of hypercapnia remains an enigma. Surprisingly few studies of hypercapnia, renal blood flow and renal hormones are reported. Redistribution of body water from intracellular to the extracellular space may be in part due to the need to buffer extracellular respiratory acidosis caused by hypercapnia. It provides an explanation for one form of hypercapnic oedema. Cyclical loss and gain of tissue mass seems more evident in cor pulmonale than ischaemic or valvular heart failure.

Animals↗
PubMed2000

Systemic stress response during operations for acute abdominal pain performed via laparoscopy or laparotomy in children.

We compared the endocrine and metabolic changes during acute emergency abdominal surgery performed using either laparoscopy or laparotomy in children. Twenty-nine children aged 1.5-14 years were assigned to undergo laparoscopy (n = 15) or laparotomy (n = 14) with a standard anaesthesia technique. Arterial blood gases and blood prolactin, cortisol, interleukin-6, glucose, insulin, lactic acid and epinephrine levels were determined 5 min after the induction of anaesthesia, 30 min into surgery and at the end of surgery. Intra-operative heart rate and mean arterial pressure were stable in both groups. In the laparoscopy group, slight respiratory acidosis occurred during surgery (p < 0.01) but there were no changes in the laparotomy group. Insulin, cortisol, prolactin, epinephrine, lactate and blood glucose levels increased in both groups (p < 0.05) although there was no difference between the groups. The surgical stress and trauma imposed by laparoscopy seems similar to that caused by laparotomy in children undergoing emergency abdominal surgery.

Abdominal Pain↗
PubMed1999

Remifentanil vs. fentanyl during interventional rigid bronchoscopy under general anaesthesia and spontaneous assisted ventilation.

The treatment of tracheo-bronchial diseases with rigid bronchoscopy requires general anaesthesia without tracheal intubation. Spontaneous assisted ventilation is a safe modality of ventilation. In this study the use of remifentanil and fentanyl is compared during rigid bronchoscopy with spontaneous assisted ventilation. Ninety high-risk patients received fentanyl or remifentanil with propofol for general anaesthesia. During the maintenance fentanyl was delivered at 6.1 +/- 4.6 micrograms kg-1 h-1 and remifentanil at 0.15 +/- 0.07 microgram kg-1 min-1. The same degree of intra-operative respiratory acidosis with similar good operating conditions resulted in both groups. Patients treated with remifentanil recovered more quickly compared with those in the fentanyl group (3.8 +/- 2 vs. 10.4 +/- 9.2 min, P < 0.001). In conclusion, the use of remifentanil during rigid bronchoscopy under general anaesthesia with spontaneous assisted ventilation is safe and assures good operating conditions. Moreover, remifentanil permits a more rapid recovery than fentanyl. The dose of remifentanil is higher than previously described for spontaneously breathing patients.

Anesthesia, General↗
PubMed1998

Endocrine and metabolic responses to plasma volume expansion during halothane anesthesia in ponies.

The study was designed to contribute to identification of the stimulus to adrenocortical activity during halothane anaesthesia in equidae. Two groups of six ponies were premedicated with acepromazine before induction of anaesthesia with thiopentone and maintenance for 120 min with halothane in oxygen. In group H Haemaccel modified gelatine plasma replacer was infused (48+/-13 mL/kg) to maintain mean arterial blood pressure (MABP) close to preanaesthetic values. In group DH, blood pressure was maintained close to preanaesthetic levels with a lower dose of Haemaccel (10 mL/kg) combined with an infusion of dobutamine. Measurements were made before anaesthesia, at 20 min intervals during anaesthesia and 20 and 120 min after anaesthesia. MABP and blood gases, pulse and respiratory rates were measured, and blood was withdrawn for assay of cortisol, adrenocorticotrophic hormone (ACTH), glucose and lactate. Ponies in both groups became hyperoxic, hypercapnic and developed a respiratory acidosis; pulse rate increased in both groups but this was more marked in group H. Haematocrit decreased by 50% in H and by 20% in DH. Cortisol and ACTH did not change significantly during anaesthesia in either group and the area under the time curve (AUC(0-140)) was lower in the DH group. Plasma glucose and lactate remained stable. After the H treatment all ponies had a watery nasal discharge and one pony died from endotoxaemia. This investigation demonstrated that the adrenocortical response to halothane anaesthesia in ponies can be ameliorated by manipulation of ABP using plasma expansion with or without inotrope infusion; however, low dose Haemaccel with dobutamine was safer and more practical. It is suggested that, although hypotension is not the sole stimulus to adrenocortical activity during halothane anaesthesia, it may contribute, probably through an effect on tissue perfusion.

Adrenal Cortex↗
PubMed2000

Anaesthetic and cardiopulmonary effects of balanced anaesthesia with medetomidine-midazolam and butorphanol in dogs.

The anaesthetic and cardiopulmonary effects of combinations of medetomidine (Me), midazolam (Mi) and butorphanol (Bu) were evaluated in dogs. The characterization of anaesthetic effects was assessed using a scoring system. The combinations tested were 20 or 40 micrograms/kg Me and 0.5 mg/kg Mi (20Me-Mi or 40Me-Mi) followed by either an intravenous injection of physiological saline solution (PSS) or Bu (0.1 or 0.3 mg/kg). The mixture of Me and Mi was injected intramuscularly, followed 15 min later by an intravenous injection of Bu or PSS in all six groups. The combined Me-Mi induced deep sedation but not profound anaesthesia. The effect of the subsequent Bu administration was observed in the scores related to its analgesic effect. There were no significant differences between the two doses of Bu, following either 20Me-Mi or 40Me-Mi in the duration of anaesthesia, heart and respiratory rates, rectal temperature, and anaesthetic and analgesic scores except for palpebral reflex, and interdigital web clamping scores. Therefore, we concluded that the addition of 0.1 mg/kg Bu to Me-Mi elicits adequate anaesthesia with adequate analgesic effect, and side-effects such as bradycardia, hypertension, and slight respiratory acidosis in some dogs.

Adrenergic alpha-Agonists↗
PubMed2001

Comparison of sevoflurane with isoflurane for rapid mask induction in midazolam and butorphanol-sedated dogs.

Rapid mask induction can be a useful induction technique for veterinary patients, although it is often accompanied by exaggerated excitement responses in unpremedicated animals (Mutoh et al.: Jpn. J. Vet. Anesth. Surg. 26, 109-116; J. Vet. Med. Sci. 57, 1007-1013; J. Vet. Med. Sci. 57, 1121-1124; 1995). The aim of this study was to compare sevoflurane with isoflurane for rapid mask induction in six dogs sedated by a combination of midazolam (0.1 mg/kg) and butorphanol (0.2 mg/kg). Induction with sevoflurane (5%, 2.4 minimum alveolar concentration [MAC]) in O2 resulted in shorter time to loss of the palpebral reflex, negative tail clamp response, and successful intubation than with isoflurane (3%, 2.4 MAC) in O2. There were no changes in heart rate or mean arterial blood pressure during induction with sevoflurane, whereas an increase in heart rate was observed in dogs induced with isoflurane. A decrease in respiratory rate compared with the pre-induction rate was observed during induction, and associated mild respiratory acidosis, characterized by an increase in arterial PCO2, was measured at the end of the induction period in both induction groups. None of the animals had episodes of induction-related complications. These results suggest that both sevoflurane and isoflurane produce a smooth onset of induction in midazolam and butorphanol-sedated dogs. Sevoflurane is a more suitable for rapid mask induction than isoflurane since it provides faster induction associated with a lower blood/gas partition coefficient.

Anesthesia, Inhalation↗
PubMed1999

Acute myopathy after status asthmaticus: steroids, myorelaxants or carbon dioxide?

Acute myopathy complicating treatment of status asthmaticus has been increasingly recognized since its original description in 1977. We report a case of an 11-year-old boy with severe asthma requiring mechanical ventilation. He was given high doses of parenteral steroids and neuromuscular blockade with non-depolarizing agents in order to achieve controlled hypoventilation with an ensuing hypercapnoea. He developed rhabdomyolysis with elevated creatinine kinase and renal impairment secondary to myoglobinuria. Electrophysiological studies revealed myopathic abnormalities. The aetiology for this myopathy appears to be related to therapy with parenteral steroids, muscle-relaxant agents and respiratory acidosis. Patients treated with steroids and neuromuscular blocking agents should be regularly monitored for development of myopathy.

Acidosis↗
PubMed1998

Ductus venosus agenesis prevents transmission of central venous pulsations to the umbilical vein in fetal sheep.

Velocity pulsations in the umbilical vein are widely used as a marker for congestive heart failure in the fetus. It has been suggested that the atrial pressure waves are transmitted to the umbilical vein mainly through the ductus venosus. In a case of ductus venosus agenesis in a fetal sheep of 110 days' gestation, we recorded pressures in the inferior vena cava and umbilical vein simultaneously with Doppler velocimetry in the medial hepatic vein and umbilical vein, under general anesthesia. During fetal respiratory acidosis (pH 7.01) and varying degrees of umbilical clamping, we did not observe the typical pulsations in the umbilical vein (deflections of the maximum velocity during atrial contraction) in spite of varying degrees of reversed flow in the hepatic vein (5-16%). The systolic-diastolic pressure amplitude in the inferior vena cava was 5.5-6.4 mmHg, sometimes reaching 9.19-11.03 mmHg. Varying degrees of reversed portocaval pressure gradient during atrial contraction (1.40-9.51 mmHg), periods of reversed portocaval pressure gradient throughout the entire cardiac cycle, tachycardia (240 beats/min) or bradycardia (99 beats/min) also did not produce the type of pulsation in the umbilical vein that reflects augmented atrial contractions. The results support the hypothesis that the ductus venosus is essential for the transmission of atrial pressure waves to the umbilical vein.

Animals↗
PubMedDate not supplied

Mechanisms controlling the oxygen consumption in experimentally induced hypochloremic alkalosis in calves.

The study was carried out on healthy Friesian calves (n = 10) aged between 10 and 30 days. Hypochloremia and alkalosis were induced by intravenous administration of furosemide and isotonic sodium bicarbonate. The venous and arterial blood samples were collected repeatedly. 2,3-diphosphoglycerate (2,3-DPG), hemoglobin and plasmatic chloride concentrations were determined. The red blood cell chloride concentration was also calculated. pH, PCO2 and PO2 were measured in arterial and mixed venous blood. The oxygen equilibrium curve (OEC) was measured in standard conditions. The correspondence of the OEC to the arterial and mixed venous compartments was calculated, taking blood temperature, pH and PCO2 values into account. The oxygen exchange fraction (OEF%), corresponding to the degree of blood desaturation between the arterial and mixed venous compartments and the amount of oxygen released at the tissue level by 100 mL of blood (OEF Vol%) were calculated from the arterial and mixed venous OEC, combined with PO2 and hemoglobin concentration. Oxygen delivery (DO2) was calculated using the arterial oxygen content, the cardiac output measured by thermodilution, and the body weight of the animal. The oxygen consumption (VO2) was derived from the cardiac output, OEF Vol% and body weight values. Despite the plasma hypochloremia, the erythrocyte chloride concentration was not influenced by furosemide and sodium bicarbonate infusion. Due to the alkalosis-induced increase in the 2,3-DPG, the standard OEC was shifted to the right, allowing oxygen to dissociate from hemoglobin more rapidly. These changes opposed the increased affinity of hemoglobin for oxygen induced by alkalosis. Moreover, respiratory acidosis, hemoconcentration, and the slight decrease in the partial oxygen pressure in mixed venous blood (Pvo2) tended to improve the OEF Vol% and maintain the oxygen consumption in a physiological range while the cardiac output, and the oxygen delivery were significantly decreased. It may be concluded that, despite reduced oxygen delivery, oxygen consumption is maintained during experimentally induced hypochloremic alkalosis in healthy 10-30 day old calves.

2,3-Diphosphoglycerate↗
PubMed2002

To ventilate or not after minimally invasive direct coronary artery bypass surgery: the role of epidural anesthesia.

OBJECTIVE: To evaluate the effect of immediate postoperative extubation and postoperative ventilation after minimally invasive direct coronary artery bypass (MIDCAB) surgery and to assess the role of epidural anesthesia. DESIGN: Randomized prospective study. SETTING: University hospital, single institution. PARTICIPANTS: Patients (n = 90) scheduled for elective MIDCAB surgery. INTERVENTIONS: Patients were divided into 3 groups: 30 patients had general anesthesia and were extubated immediately after surgery (extubated group), 30 patients had a thoracic epidural and general anesthesia and were extubated immediately after surgery (epidural group), and 30 patients had general anesthesia and were ventilated after surgery (intubated group). MEASUREMENTS AND MAIN RESULTS: With a similar cardiac index and less vasoactive medication, mean arterial blood pressure (77 plus minus 8 mmHg [mean plus minus SD]) and heart rate (76 plus minus 10 beats/min) in the epidural group were lower on the first postoperative day than in the intubated group (83 plus minus 10 mmHg and 81 plus minus 13 beats/min) and the extubated group (86 plus minus 10 mmHg and 83 plus minus 13) (p = 0.01 and p = 0.09). Oxygenation on the first postoperative day was better in the epidural group than in the intubated group (14.8 plus minus 3.8 kPa v 12.6 plus minus 3.2 kPa; p = 0.05). The epidural group and the extubated group had a transient respiratory acidosis postoperatively. Pain score in the epidural group was lower on the first postoperative day than in the extubated group with general anesthesia (3.0 plus minus 1.6 visual analog scale v 4.6 plus minus 1.8 visual analog scale; p = 0.01). Hospital stay was shorter in the epidural group than in the ventilated group (5.9 plus minus 2.4 days v 8.1 plus minus 5.3 days; p = 0.05) CONCLUSION: Immediate postoperative extubation in patients with thoracic epidural anesthesia and supplemental general anesthesia provides the most favorable clinical circumstances after MIDCAB surgery.

Anesthesia, Epidural↗
PubMed2001

The use of dipyridamole to wean from inhaled nitric oxide in congenital diaphragmatic hernia.

A full-term neonate with a left-sided congenital diaphragmatic hernia (CDH) was ventilated mechanically by high-frequency oscillatory ventilation (HFOV). Despite inhaled nitric oxide (iNO) at a dose of 15 ppm, the neonate had severe respiratory acidosis and was placed on extracorporeal membrane oxygenation (ECMO) for 2 days. On day 7 of life, surgical repair of the CDH was performed. After the intervention, iNO (20 ppm) had to be restarted because of severe pulmonary hypertension (PHT). Ventilatory support and iNO then were weaned progressively. However, each daily attempt to discontinue iNO (from 2 ppm to 0 ppm), led to severe desaturation with significant right-to-left shunting. At the age of 33 days, dipyridamole (persantin) was administered intravenously at a dose of 0,4 mg/kg/min over 10 minutes and repeated every 12 hours for a total of 3 doses. After the second administration of dipyridamole, iNO could be stopped without rebound of PHT, and the neonate was extubated 1 week later. The authors report the use of dipyridamole for successful withdrawal of iNO. By inhibition of phosphodiesterase type 5, dipyridamole has the potential to increase the level of cyclic guanosine monophosphate in vascular smooth muscle cells, permitting vasodilation and restoration of endogenous NO. J Pediatr Surg 36:1864-1865.

Dipyridamole↗
PubMed2001

Does extubation result in haemodynamic instability in patients following coronary artery bypass grafts?

Coronary heart disease and its management continue to be at the centre of Government health policy. The present political climate demands clinical effectiveness and best practice should be established, while maintaining the philosophy of cost-effectiveness and resource management. These directives have led practitioners to question the care of patients following coronary artery bypass surgery, in particular the role of mechanical ventilation and the subsequent act of extubation. A retrospective study of 89 patients who had coronary artery bypass grafts (emergency and elective) was undertaken, to establish if extubation had a significant effect on the haemodynamic status of patients with variable degrees of left ventricular function (19% with poor left ventricular function). The study found that extubation was achieved within a mean time of 4.97 hours following return from surgery. Extubation resulted in a significant increase in heart rate (P = 0.001), as well as a respiratory acidosis (pCO2: P = 0.000; pH: P = 0.000). However, the stability of the patient was not compromised, with neither mean arterial blood pressure (P = 0.825) nor oxygenation levels (P = 0.267) being significantly altered by extubation. On multivariate analysis, the act of extubation had no significant effect on any of the dependent variables. These results suggest that it is not extubation alone that has an impact on the haemodynamic stability of patients following coronary artery bypass grafts, but that this is indeed multifactorial. Therefore extubation is 'safe' practice for patients with varying degrees of left ventricular function following coronary artery bypass grafts. Limitations of the study are acknowledged.

Adult↗