Hypercarbia and high-flow nasal oxygen use during anaesthesia - risking a failure to thrive?

Prevention of arterial oxygen desaturation during anaesthesia with high-flow nasal oxygen (HFNO) has gained greater acceptance for a widening range of procedures. However, during HFNO use there remains the potential for development of significant anaesthesia-associated apnoea or hypoventilation and the possibility of hypercarbia, with harmful cardiovascular or neurological sequelae. The aim of this study was to determine whether any HFNO-related hypercarbia adverse incidents had been reported on webAIRS, an online database of adverse anaesthesia-related incidents. Two relevant reports were identified of complications due to marked hypercarbia during HFNO use to maintain oxygenation. In both reports, HFNO and total intravenous anaesthesia were used during endoscopic procedures through the upper airway. In both, the extent of hypoventilation went undetected during HFNO use. An ensuing cardiac arrest was reported in one report, ascribed to acute hypercarbia-induced exacerbation of the patient's pre-existing pulmonary hypertension. In the other report, hypercarbia led to a prolonged duration of decreased level of consciousness post procedure, requiring ventilatory support. During the search, an additional 11 reports of postoperative hypercarbia-associated sedation were identified, unrelated to HFNO. In these additional reports an extended duration of severe acute hypercarbia led to sedation or loss of consciousness, consistent with the known effects of hypercarbia on consciousness. These 13 reports highlight the potential dangers of unrecognised and untreated hypercarbia, even if adequate oxygenation is maintained.

Which anesthetic agents for ambulatory electro-convulsive therapy?

PURPOSE OF REVIEW: There have been a considerable number of research articles published in the last 10 years outlining possible advances in the provision of electro-convulsive therapy (ECT) anaesthesia. This has resulted in a range of new drugs having been proposed as useful in the ECT setting. In particular, the use of adjuvant drugs that might improve outcomes to treatment has been investigated. RECENT FINDINGS: There is a high level of interest in ketamine and remifentanil as agents that may alter response in ECT anaesthesia, by reducing cognitive effects, and minimizing the dose of induction agent. The numbers of patients involved in current trials have been small, and it is not possible to give a definitive answer as to the usefulness of these drugs at this stage. SUMMARY: This review covers the major recent trials involving new and emerging treatments in ECT, and brings the reader up to date with state of knowledge of ECT anaesthesia and pharmacology.

Low dose lignocaine added to propofol does not attenuate the response to electroconvulsive therapy.

BACKGROUND: The addition of small amounts of lignocaine (50 mg) to propofol (200 mg) has been previously shown to reduce pain in injection, a common problem with this particular anaesthetic agent. The aim of this study was to investigate whether using the mixture of propofol plus lignocaine had any adverse effects on ECT seizure expression (duration, and ictal quality). METHOD: Ictal EEG records were retrospectively examined in 29 patients who underwent 80 pairs of ECT treatments, one given with propofol alone and one with propofol plus lignocaine. Ictal quality was manually rated for the transition from the polyspike phase to the slow wave phase, amplitude of the mid-ictal spike-and-wave phase, regularity of morphology of the predominant pattern of the slow wave phase, stereotypy, variability of the morphology and amplitude of the slow wave phase and post-ictal suppression. RESULTS: There was no significant difference in seizure duration between the two groups (33.4+/-13.0 s (propofol) vs. 33.6+/-11.2 s (propofol plus lignocaine). Furthermore although the addition of lignocaine delayed the onset of the slow wave phase by about 1s, it resulted in an improvement in three of four of the other measures of ictal quality. CONCLUSION: The addition of a small dose of lignocaine to propofol during ECT treatment enhanced rather than reduced the quality of the seizures produced.

Ketamine and midazolam delivered by patient-controlled analgesia in relieving pain associated with burns dressings.

BACKGROUND: A study involving the use of a mixture of ketamine and midazolam delivered via patient-controlled analgesia (PCA) device was trialed to assess its effectiveness in reducing pain associated with repeated burns dressings in an adult population. METHODS: Patients undergoing burns dressings changes were given a PCA device of ketamine and midazolam to use during the procedure. The aims were to investigate the efficacy of the device and to ascertain what (if any) adverse effects were associated with its use. RESULTS: During the trial period, 44 patients who underwent 95 separate procedures were enrolled. The effectiveness of the device was rated (out of 10) by both staff and patients with the mean scores being 8.47 and 8.50, respectively. In all but 1 case, the proposed procedure was carried out successfully. Thirteen patients reported a total of 23 adverse effects, with hallucinations (11) being the most common. CONCLUSIONS: The use of ketamine/midazolam delivered by PCA was shown to be an effective means of pain control during burns dressings as assessed by both staff and patients. The incidence of adverse events was low.

Cognitive impairment following electroconvulsive therapy--does the choice of anesthetic agent make a difference?

The range of drugs available to provide anesthesia for patients undergoing electroconvulsive therapy (ECT) is ever increasing. Initially, anesthetic agents were selected on the basis of their capacity not to antagonize the induced seizure. This was not always a simple task because almost all general anesthetic agents have "in built" antiepileptic activity. Nonbarbiturate agents such as propofol have been successfully used as alternatives to thiopental and methohexitone, but this drug too has antiepileptic properties. Most recently, opioid-like drugs such as remifentanil have been used, and there has been renewed interest in ketamine, a phencyclidine derivative. Attention has also focused on whether the anesthetic agent selected may affect the cognitive impairment seen after ECT. Studies in this area are limited, but early results suggest that agents such as ketamine may have particular benefit. This article reviews the current literature dealing with anesthesia and postoperative cognitive impairment in general and with regard to ECT in particular.

Effective strategy to guide pathology test ordering in surgical patients.

BACKGROUND: Ordering of pathology testing by junior medical staff is often a haphazard process with little regard to the appropriateness of test ordering. The aim of the present study was to reduce ordering of inappropriate pathology tests in surgical patients attending the pre-admission clinic (PAC) through the introduction of a protocol-based test ordering system and to create an environment where such improvement can be sustained. METHODS: This is a prospective study with a retrospective control group. Three cohorts of patients attending the PAC were included. Group I (n = 700) attended prior to the introduction of the test protocols (April-June 2002) and acted as a control group. Group II (n = 720) attended after the protocol introduction (April-June 2003), and group III (n = 763) attended during the subsequent 3-month period from July to August 2003. The study examined the numbers of patients in each group who were ordered any of eight standard pathology tests. The average number of tests per patient, and cost of tests per patient were also ascertained. RESULTS: Following the introduction of pathology test protocols, the ordering of all but one of the eight tests was statistically significantly reduced. In particular, ordering of coagulation studies was reduced from 22.5% to 13.8% and electrolytes, urea and creatinine from 65.2% to 48.25% of patients (both P < 0.0001). Average number of tests performed per patient declined from 2.48 to 1.88, representing a savings of 10.33 dollars per patient (a decrease from 42.22 dollars to 31.89 dollars) and a projected annualized cost saving in excess of 26,000 dollars. CONCLUSIONS: Provided that certain preliminary guidelines are followed, these protocols can reduce pathology test ordering in any pre-admission Service.

New directions in pain management.

Pain medicine is one of the most rapidly developing medical specialties of today. While there are many modalities that can be used in managing the patient in pain, drug treatment remains, for the most part, the cornerstone of treatment. Opioids retain their position as the foundation of most analgesic strategies, although they tend to be used nowadays in combination with adjuvant analgesics such as paracetamol and nonsteroidal antiinflammatory drugs. The range of available opioids has also been expanded with drugs such as hydromorphone and oxycodone, originally developed almost a century ago. This expanded choice has resulted in the concept of opioid rotation in chronic pain states, an approach that is aimed at maintaining pain control while minimizing adverse effects. Nonsteroidal antiinflammatory drugs continue to play an important role, especially as adjuvants, and the development of drugs such as celecoxib and refecoxib, highly specific for the inhibition of cyclooxygenase 2 pathway has been a further advance. The treatment of neuropathic pain continues to be a challenge to the clinician. While this has traditionally been treated with drugs from the anticonvulsant, antiarrhythmic and anti-depressant groups, results from these treatments have often been less than satisfactory. This has led to the development of completely new drug classes that modulate neuronal transmission in pain pathways, some of which are derived from exotic animal sources, such as the conotoxins from the marine snail family and epibatidine from a species of frog. The role of cannabinoids remains controversial.