Naloxone in shock

Naloxone for shock

BACKGROUND

There is pre-clinical evidence, involving several animal species, suggesting that opioid peptides play a role in the physiopathology of shock (endotoxic, hypovolemic, cardiogenic, spinal, anaphylactic). Many case reports have suggested that naloxone (an opiate antagonist) might be an effective treatment for shock in humans, but others have not supported such a point of view. This controversy led us to undertake a meta-analysis of the available evidence on the efficacy of naloxone as a treatment measure of shock in humans.

OBJECTIVES

To evaluate the effectiveness and safety of naloxone in human shock and to estimate the methodological quality of the clinical trials.

SEARCH STRATEGY

Computerized bibliographic search up to December 2002, review of references of all papers found on the subject and contact with primary investigators of eligible studies.

SELECTION CRITERIA

Randomized controlled trials evaluating naloxone in human shock, regardless of the patient's age (adult, child or neonate).

DATA COLLECTION AND ANALYSIS

Three independent reviewers extracted data on study design, intervention, outcome and methodological quality.

MAIN RESULTS

Three independent readers reviewed 80 human publications and selected six clinical trials. Overall agreement on study selection was perfect (concordance: 100%). This meta-analysis includes six studies involving 126 patients with septic, cardiogenic, hemorrhagic or spinal shock. Naloxone therapy was associated with statistically significant hemodynamic improvement (odds ratio 0.24; 95% confidence interval [95%CI] 0.09-0.68). The mean arterial pressure was significantly higher in the naloxone groups than in the placebo groups (weighted mean difference: +9.33 mmHg; 95%CI 7.07-11.59). No heterogeneity was found for this outcome. The death rate was lower in the naloxone group (odds ratio 0.59; 95%CI 0.21-1.67) but this was consistent with the play of chance. A significant heterogeneity for the latter outcome was detected (p<0.05).

REVIEWER'S CONCLUSIONS

Naloxone improves blood pressure, especially mean arterial blood pressure. However, the clinical usefulness of naloxone to treat shock remains to be determined, and additional randomized controlled trials are needed to assess its usefulness.

Opiate antagonists for the treatment of schizophrenia

Numerous studies suggest that opiate antagonists may have antipsychotic properties. A review of the literature describing the use of naloxone to treat schizophrenic patients has shown mixed results. The three studies on naltrexone have found no benefit in controlling auditory hallucinations. We present a synopsis of these studies.

Septic shock in critically ill patients: aetiology, management and outcome

Over a period of 28 months, 45 episodes of septic shock from 83 episodes of bacteraemia were studied prospectively to evaluate their clinical profile, management and outcome. Thirty-six patients were studied, the overall incidence of septic shock being 54.2%. Gram-negative organisms accounted for 23 (51.1%) of such episodes, Gram-positive 17 (37.8%), and three episodes were polymicrobial (6.7%). The organisms isolated most frequently were Staphylococcus epidermidis (17.8%), Pseudomonas aeruginosa (13.3%), Escherichia coli and Klebsiella sp. (each 11.1%). Coagulation abnormalities were detected in 32 episodes (78%) and disseminated intravascular coagulation (DIC) occurred in 11 of these with high mortality. The most common underlying conditions were respiratory, hepatic and renal failures. The majority of these patients received crystalloids, colloids, vasopressor drugs and blood. Swan-Ganz catheters (SGC) were inserted on eight occasions, the majority of times indicating a hyperdynamic circulatory response. The overall mortality was 40%, despite aggressive management and intensive care. The most important factor in reducing mortality is early detection of bacteraemia and prompt management of these patients.

Opioid biology: the next set of questions

A range of biologically different opioid peptides are synthesised as components of three distinct precursors, pro-opiomelanocortin, proenkephalin, and prodynorphin. They interact with a number of receptors which have so far been characterised as mu, delta, kappa, sigma, and epsilon. It is unclear which ligands bind to which receptors under physiological circumstances, but preferential in vitro interactions include enkephalins with delta receptors, dynorphin with kappa receptors, and beta-endorphin with epsilon receptors. Post-translational processing determines which of several opioid products are produced from each precursor, but the identity of the enzymes involved and regulation of processing is unknown. Opioid involvement in the neuroendocrine and cardiovascular systems is reviewed. Naloxone-sensitive opioid mechanisms are implicated in the control of gonadotrophin and adrenocorticotropic hormone secretion and in the hypotension of various types of shock. The investigation of possible dynorphin involvement in neurohypophysial function is taking place because vasopressin and dynorphin A (1-8) have been shown to coexist in the neurosecretory vesicles of magnocellular neurons.

Naloxone

Naloxone hydrochloride, a synthetic N-allyl derivative of oxymorphone, is an effective agent for the reversal of the cardiovascular and respiratory depression associated with narcotic and possibly some non-narcotic overdoses. It is essentially a pure narcotic antagonist, is relatively safe, and is a useful diagnostic and therapeutic agent. Due to naloxone's pharmacokinetic profile, a continuous infusion protocol is recommended when prolonged narcotic antagonist effects are required. The complex pharmacodynamics of naloxone, specifically relating to endorphin receptor sites, focus its potential use in a variety of clinical situations as continuing research illustrates the association of endogenous opioid compounds with various disease states.

An investigation of the role of the specific opioid antagonist naloxone in clinical toxicology

1 An assessment of the current role of naloxone in clinical toxicology has been made in a series of three separate epidemiological studies. 2 Through the National Poisons Information Service we found that the role of naloxone in opioid poisoning is often not appreciated by the enquirer and that toxicological screening is often requested before the diagnostic use of naloxone. 3 The recommended dose of naloxone (0.4--1.2 mg i.v.) is not always adequate. In 51 cases where naloxone was effective, doses of up to 3.2 mg were necessary (mean 1.8 +/- 0.3 mg SEM i.v.). 4 In 31 cases of non-opioid poisoning, naloxone in doses of 0.4--1.2 mg i.v. caused no deterioration, whilst six patients in whom no opioids were detected showed clinical improvement. 5 In 300 cases of suspected ethanol-induced coma, 49 showed reversal of coma with naloxone, and in 38 cases ethanol was the sole cause of coma (mean plasma concentration 3.54 +/- 0.62 g/l SEM). 6 These results suggest that the role of naloxone in clinical toxicology is not fully appreciated. There is a need for further education as to its indications in opioid poisoning, together with additional studies to define more accurately the dose/response relationship. In addition, the role of naloxone in coma induced by ethanol and certain other non-opioids needs to be evaluated further.

Endogenous opiates: 1981

This paper is the fourth of an annual series reviewing the research concerning the endogenous opiate peptides. This installment covers only work published during 1981 and attempts to provide a comprehensive, but not exhaustive, survey of the area. Previous papers in the series have dealt with research done before 1981. Topics concerning endogenous opiates reviewed here include a delineation of their receptors, their distribution, their precursors and degradation, behavioral effects resulting from their administration, their possible involvement in physiological responses, and their interactions with other peptides and hormones. Due to the burgeoning literature in this field, the comprehensive nature of this review in the future will be limited to considerations of behavioral phenomena related to the endogenous opiates.