Claes-Roland Martling

Substance P-immunoreactive sensory nerves in the lower respiratory tract of various mammals including man

SummaryThe occurrence and origin of substance P (SP)-immunoreactive (IR) nerves in the lower respiratory tract was studied by means of immunohistochemistry in the guinea-pig, rat, cat and man. In addition, biopsies from human material were also analysed by radioimmunoassay. SP-IR nerves were seen in four principal locations: 1) under or within the lining epithelium, 2) around blood vessels, 3) within the bronchial smooth muscle layer, and 4) around local tracheobronchial ganglion cells. Ligation experiments combined with capsaicin pretreatments indicated that all SP-IR nerves in the respiratory tract are sensory. The trachea seems to be mainly supplied by the vagal nerves, while intrapulmonary bronchi and blood vessels receive SP-IR nerves of both vagal and non-vagal (spinal) origin. SP-IR nerves were also found in the human bronchi with principally similar location as in the guinea-pig. The levels of SP-IR in the trachea and peripheral bronchi of man were about 3–4 pmol/g, which is in the same range as the content of corresponding tissues from the guinea-pig.In conclusion, the present experimental findings of SP-IR nerves in the lower respiratory tract in both experimental animals and man support the functional evidence for the importance of SP in the vagal and non-vagal (spinal) control of bronchial smooth muscle tone and vascular permeability.

The Outcome of Neutrophil Gelatinase-Associated Lipocalin-Positive Subclinical Acute Kidney Injury: A Multicenter Pooled Analysis of Prospective Studies

OBJECTIVES The aim of this study was to test the hypothesis that, without diagnostic changes in serum creatinine, increased neutrophil gelatinase-associated lipocalin (NGAL) levels identify patients with subclinical acute kidney injury (AKI) and therefore worse prognosis. BACKGROUND Neutrophil gelatinase-associated lipocalin detects subclinical AKI hours to days before increases in serum creatinine indicate manifest loss of renal function. METHODS We analyzed pooled data from 2,322 critically ill patients with predominantly cardiorenal syndrome from 10 prospective observational studies of NGAL. We used the terms NGAL(-) or NGAL(+) according to study-specific NGAL cutoff for optimal AKI prediction and the terms sCREA(-) or sCREA(+) according to consensus diagnostic increases in serum creatinine defining AKI. A priori-defined outcomes included need for renal replacement therapy (primary endpoint), hospital mortality, their combination, and duration of stay in intensive care and in-hospital. RESULTS Of study patients, 1,296 (55.8%) were NGAL(-)/sCREA(-), 445 (19.2%) were NGAL(+)/sCREA(-), 107 (4.6%) were NGAL(-)/sCREA(+), and 474 (20.4%) were NGAL(+)/sCREA(+). According to the 4 study groups, there was a stepwise increase in subsequent renal replacement therapy initiation-NGAL(-)/sCREA(-): 0.0015% versus NGAL(+)/sCREA(-): 2.5% (odds ratio: 16.4, 95% confidence interval: 3.6 to 76.9, p < 0.001), NGAL(-)/sCREA(+): 7.5%, and NGAL(+)/sCREA(+): 8.0%, respectively, hospital mortality (4.8%, 12.4%, 8.4%, 14.7%, respectively) and their combination (4-group comparisons: all p < 0.001). There was a similar and consistent progressive increase in median number of intensive care and in-hospital days with increasing biomarker positivity: NGAL(-)/sCREA(-): 4.2 and 8.8 days; NGAL(+)/sCREA(-): 7.1 and 17.0 days; NGAL(-)/sCREA(+): 6.5 and 17.8 days; NGAL(+)/sCREA(+): 9.0 and 21.9 days; 4-group comparisons: p = 0.003 and p = 0.040, respectively. Urine and plasma NGAL indicated a similar outcome pattern. CONCLUSIONS In the absence of diagnostic increases in serum creatinine, NGAL detects patients with likely subclinical AKI who have an increased risk of adverse outcomes. The concept and definition of AKI might need re-assessment.

Co-existence of peptide HI (PHI) and VIP in nerves regulating blood flow and bronchial smooth muscle tone in various mammals including man

By immunohistochemistry it was found that PHI- and VIP-like immunoreactivity (-IR) occurred in the same autonomic neurons in the upper respiratory tract, tongue and salivary glands with associated ganglia in rat, guinea-pig, cat, pig and man. VIP- and PHI-like immunoreactivity was also found in similar locations in the human heart. The N-terminally directed, but not the C-terminally directed, PHI antiserum or the VIP antiserum stained endocrine cells in the pig duodenum. This suggests the existence of an additional PHI-like peptide. Ligation of nerves acutely caused marked overlapping axonal accumulations of PHI- and VIP-IR central to the lesion. Two weeks after transection of the nerves, both types of immunoreactivities were still observed in accumulations both in the axons as well as in the corresponding cell bodies. The levels of PHI- and VIP-IR in normal tissues from the cat were around 10-50 pmol/g with a molar ratio of about 1 to 2. Systemic administrations of PHI and VIP induced hypotension, probably due to peripheral vasodilation in both guinea-pig and cat. Furthermore, both PHI and VIP caused an inhibition of the vagally induced increase in respiratory insufflation pressure in guinea-pig. PHI and VIP relaxed the guinea-pig trachea in vitro, suggesting a direct action on tracheobronchial smooth muscle. VIP was about 5-10 times more potent than PHI with regard to hypotensive effects and 2-3-fold, considering respiratory smooth muscle-relaxant effects in the guinea-pig. PHI was about 50-fold less potent to induce hypotension in the cat than in the guinea-pig. Although species differences seem to exist as regards biological potency, PHI should also be considered when examining the role of VIP as an autonomic neurotransmitter.

Dramatic effect on oxygenation in patients with severe acute lung insufficiency treated in the prone position.

OBJECTIVE To confirm the positive effect of prone positioning on oxygenation in patients with acute lung insufficiency. DESIGN Clinical follow-up study. SETTING The intensive care unit at a tertiary care academic hospital. PATIENTS Thirteen patients suffering from severe acute lung insufficiency caused by trauma, septicemia, aspiration, and burn injury. Eleven of the patients had severe hypoxia (oxygenation indices [PaO2/FIO2] < or = 80 torr [< or = 10.7 kPa]). Patients > 70 yrs of age were excluded from the study. INTERVENTIONS Treatment in the prone position without changing other ventilatory settings than FIO2 when saturation increased. MEASUREMENTS AND MAIN RESULTS Twelve of the 13 patients responded to treatment in the prone position. The patient that did not respond improved her gas exchange when nitric oxide was instituted. She died, however, from a Gram-negative septicemia. No patient needed extracorporeal membrane oxygenation. Apart from the settings of FIO2 when saturation increased, the ventilatory settings were unchanged. In the prone position, the oxygenation index increased (p < .0002) and the alveolar-arterial oxygen gradient, P(A-a)O2, decreased dramatically (p < .0001). CONCLUSIONS The prone position significantly improves impaired gas exchange due to severe acute lung insufficiency. It is suggested that this treatment is used before more complex modalities.

Calcitonin gene-related peptide and the lung: neuronal coexistence with substance P, release by capsaicin and vasodilatory effect

The occurrence and distribution of calcitonin gene-related peptide (CGRP) in the lower airways was studied by means of immunohistochemistry and radioimmunoassay (RIA) in combination with high performance liquid chromatography (HPLC). CGRP-like immunoreactivity (-LI) was observed in nerves from the epiglottis down to peripheral bronchi in rat, cat and guinea pig and also in human bronchi. Double staining revealed colocalization of CGRP-LI and substance P (SP)-LI in cell bodies of nodose and jugular ganglia as well as in axons and nerve terminals of the airways. Systemic capsaicin pretreatment induced a marked loss of the CGRP- and SP-immunoreactive (-IR) nerves in the lower airways. CGRP-IR was also present in epithelial endocrine cells and neuroepithelial bodies. The content of CGRP-LI as measured with RIA in guinea pig bronchi was significantly lower after capsaicin pretreatment. Analysis of human bronchial extracts revealed that CGRP-LI coeluted with synthetic human CGRP on HPLC. In the isolated perfused guinea pig lung capsaicin exposure caused overflow of CGRP-LI suggesting release from peripheral branches of sensory nerves. Both in vivo experiments in the guinea pig measuring insufflation pressure as well as in vitro studies on isolated guinea pig and human bronchi showed that whereas tachykinins contracted bronchial smooth muscle no contractile or relaxing effect was elicited by human or rat CGRP. However, CGRP caused relaxation of serotonin precontracted guinea pig and human pulmonary arteries. In conclusion, the presence and release of CGRP-LI from capsaicin sensitive nerves in the lower airways adds another possible mediator, in addition to tachykinins, of vascular reactions upon sensory nerve irritation.

Occurrence and effects of multiple tachykinins; Sustance P, neurokinin A and neuropeptide K in human lower airways

In the present work we have studied the occurrence of different tachykinins (substance P (SP), neurokinin A (NKA) and neuropeptide K (NPK)) in human distal bronchi and pulmonary arteries by means of radioimmunoassay (RIA) and high performance liquid chromatography (HPLC). We have also compared the biological effects of different tachykinins on isolated human bronchi and pulmonary arteries in vitro. The concentration of immunoreactive SP using antiserum SP2 in the pulmonary arteries was higher (1.34 +/- 0.15 pmol/g) than in the bronchi (0.56 +/- 0.05 pmol/g). The contents of other tachykinins than SP measured using antiserum K12 was on the other hand considerably higher in the bronchi (0.33 +/- 0.14 pmol/g) than in pulmonary arteries (0.13 +/- 0.02 pmol/g). Immunoreactive materials corresponding to SP, NKA and NPK were identified in bronchial extracts by RIA combined with HPLC, which also indicated the presence of an eledoisin (ELE)-like component. In vitro studies showed that NKA was the most potent of the tachykinins as a bronchoconstrictor agent, being several hundred-fold more active than SP, acetylcholine and histamine. NPK had an intermediate potency. The bronchoconstrictor effect of NKA was unaffected by atropine, mepyramine and cimetidine. The tachykinins SP and NKA had on the other hand, a rather equal potency in inducing relaxation of serotonin precontracted pulmonary arteries. In conclusion, multiple tachykinins are present in lower airways of man. These peptides exert different biological activities whereby NKA is a very active bronchoconstrictor agent compared to SP while both NKA and SP have rather similar relaxatory activities of vascular smooth muscle.

Inhibition of cholinergic and non-adrenergic, non-cholinergic bronchoconstriction in the guinea pig mediated by neuropeptide Y and α2-adrenoceptors and opiate receptors

The mechanisms underlying the regulatory influence of neuropeptide Y (NPY) and of alpha 2-adrenoceptor and opiate receptor activation on cholinergic and excitatory non-adrenergic, non-cholinergic (e-NANC) neurotransmission were studied in guinea pig hilus bronchi in vitro. NPY inhibited both the cholinergic and e-NANC bronchial contractions evoked by field stimulation. The NPY attenuation of the e-NANC contraction could not be antagonized by the alpha 2-antagonist, idazoxan, or naloxone. UK 14,304 a specific alpha 2-agonist, also reduced the two nervous components of bronchial contraction and this action was inhibited by idazoxan. NPY and UK 14,304 exerted a minor influence on the bronchial smooth muscle tone per se or on contractions evoked by acetylcholine or neurokinin A. This suggested that the inhibitory responses were caused by a prejunctional action reducing the release of transmitter substances from sensory and cholinergic nerve endings. Furthermore NPY (10(-7) M) seemed to be more potent to inhibit both contractile components than noradrenaline (10(-6) M) in the presence of propranolol (3 X 10(-6) M). Morphine was able to reduce the e-NANC response via a naloxone-sensitive mechanism. The capsaicin-evoked bronchoconstriction and the bronchodilator NANC effect evoked by field stimulation were, however, not influenced by UK 14,304. It is concluded that NPY, alpha 2-receptor and opiate receptor activation inhibit the release of sensory transmitters evoked by field stimulation but not by capsaicin.

Capsaicin Sensitive Afferents Contribute to Acute Airway Edema following Tracheal Instillation of Hydrochloric Acid or Gastric Juice in the Rat

The formation of acute edema in the tracheobronchial mucosa following local instillation of hydrochloric acid or gastric juice was studied in rats. Protein extravasation using the Evans blue technique was measured and used to indicate edema formation. A pH dependent Evans blue extravasation was observed whereby pH 2 produced a small, pH 1,5 an intermediate, and pH 1 a pronounced effect. Also, gastric juice (pH 1.3 ± 0.1) induced a marked Evans blue extravasation in the tracheobronchial mucosa. Rats which had been pretreated with capsaicin (100 mg/kg s.c.) had a much lower Evans blue extravasation following local instillation of both hydrochloric acid and gastric juice. Thus, the increase in Evans blue content induced by acid at pH 1.5 was abolished while about 50% of the response remained at pH 1. The protein extravasation caused by gastric juice was reduced by about 70% after capsaicin treatment. Terbutaline (73 nmol/kg, iv) or emprophylline (25 μmol/kg, iv) injected intravenously 10 min before, as well as hydrocortisone injected immediately after the intratracheal instillation of gastric juice, did not influence the magnitude of edema formation. Beta-methasone (0.25 mg/kg ip) pretreatment 24 h prior to the gastric juice exposure enhanced tracheal extravasation. In conclusion, acute protein extravasation in the lower airway mucosa induced by hydrochloric acid or gastric juice is mainly dependent on capsaicin sensitive sensory nerves, suggesting that local release of mediators, such as tachykinins, play a key role in this reaction.

Capsaicin pretreatment inhibits vagal cholinergic and non-cholinergic control of pulmonary mechanics in the guinea pig

Summary1.The effects of vagal nerve stimulation, ether, capsaicin, histamine and substance P (SP) on lung resistance (R1) and dynamic lung compliance (CDYN) were studied in anaesthetized guinea pigs. The in vivo responses in control animals were compared with the effects after systemic pretreatment with capsaicin or local application of capsaicin on the cervical vagal nerves.2.Vagal nerve stimulation induced an increase in RL and a fall in CDYN. Significant changes in RL and DDYN (more than 50%) were still present after atropine, while the vagal heart response was abolished. Systemic or local capsaicin pretreatment abolished the atropine-resistant vagal effect on RL and CDYN. The atropine-sensitive changes in pulmonary mechanics upon vagal stimulation were significantly reduced by capsaicin pretreatment.3.The increase in RL and a fall in CDYN induced by ether and capsaicin was significantly reduced or abolished by systemic capsaicin pretreatment, while the histamine-induced bronchoconstriction was only slightly reduced. Ether and capsaicin seemed also to activate capsaicin-sensitive neurons of non-vagal origin since they still caused large effects in animals, which has been locally pretreated with capsaicin on the vagal nerves. The increased RL and decreased CDYN induced by SP was unchanged in capsaicin-pretreated animals.4.The tracheal tension increase in vitro induced by acetylcholine and histamine was uninfluenced by systemic capsaicin pretreatment. The atropine-sensitive tracheal contraction and atropine-resistant relaxation upon field stimulation seemed also to be unchanged after capsaicin pretreatment.5.Choline-acetyltransferase activity and muscarinic receptor-binding characteristics (affinity and number of receptor sites) in the trachea and lung of the guinea pig and rat were found to be unchanged after systemic capsaicin pretreatment.6.In conclusion, capsaicin pretreatment abolishes the non-cholinergic vagal changes in RL and CDYN. However, the vagal cholinergic control of pulmonary mechanics was partially inhibited by capsaicin pretreatment. This seemed to occur via mechanisms not involving degeneration of cholinergic nerves or major changes in muscarinic receptor function.

Three cases of PICU sedation with isoflurane delivered by the ‘AnaConDa®’

Prolonged sedation in the pediatric intensive care unit may be difficult because of tolerance, drug dependence and withdrawal, drug interactions and unwanted drug effects. We present three patients sedated with isoflurane via the Anesthetic Conserving Device, AnaConDa®. AnaConDa® is a modified heat and moisture exchanger that allows evaporation and delivery of inhalational anesthetics without an anesthesia machine, vaporizer or adapted ventilator. Two patients with abdominal complications and prolonged sedation for mechanical ventilation were converted to isoflurane sedation for several days. The third patient with refractory status epilepticus received isoflurane to treat epileptiform electroencephalogram activity. Patients weighing 40 and 30 kg were treated with AnaConDa® placed at the Y‐piece, while the patient weighing 20 kg was treated with AnaConDa® in the inspiratory limb of the respiratory circuit. Adequate sedation was achieved with endtidal isoflurane concentration of 0.3–0.4%, while antiepileptic effect was achieved at a higher dose, 0.9%. Intravenous sedatives could be reduced or discontinued during isoflurane sedation. Inhaled sedation of isoflurane with AnaConDa® was effective in these patients. It may provide an alternative in difficult cases needing prolonged sedation and should be evaluated further.