Effect of high-flow nasal oxygen on hypoxaemia during procedural sedation: a systematic review and meta-analysis.

We conducted a systematic review to evaluate the effect of high-flow nasal oxygen and conventional oxygen therapy during procedural sedation amongst adults and children. We searched MEDLINE, EMBASE and CINAHL for randomised controlled trials that reported the effects of high-flow nasal oxygen during procedural sedation. The primary outcome measure was hypoxaemia and the secondary outcomes were minimum oxygen saturation; hypercarbia; requirement for airway manoeuvres; and procedure interruptions. The quality of evidence was assessed using the revised Cochrane risk-of bias tool and grading of recommendations, assessment, development and evaluation (GRADE). Nineteen randomised controlled trials (4121 patients) including three in children were included. Administration of high-flow nasal oxygen reduced hypoxaemia, risk ratio (95%CI) 0.37 (0.24-0.56), p < 0.001; minor airway manoeuvre requirements, risk ratio (95%CI) 0.26 (0.11-0.59), p < 0.001; procedural interruptions, risk ratio (95%CI) 0.17 (0.05-0.53), p = 0.002; and increased minimum oxygen saturation, mean difference (95%CI) 4.1 (2.70-5.50), p < 0.001; as compared with the control group. High-flow nasal oxygen had no impact on hypercarbia, risk ratio (95%CI) 1.24 (0.97-1.58), p = 0.09, I2 = 0%. High-flow nasal oxygen reduced the incidence of hypoxaemia regardless of the procedure involved, degree of fractional inspired oxygen, risk-profile of patients and mode of propofol administration. The evidence was ascertained as moderate for all outcomes except for procedure interruptions. In summary, high-flow nasal oxygen compared with conventional oxygenation techniques reduced the risk of hypoxaemia, increased minimum oxygen saturation and reduced the requirement for airway manoeuvres. High-flow nasal oxygen should be considered in patients at risk of hypoxaemia during procedural sedation.

A comparison of ultrasound guided bilateral single injection shot Erector Spinae Plane blocks versus wound infiltration for post-operative analgesia in laparoscopic assisted colonic surgery- a prospective randomised study.

BACKGROUND: Both wound infiltration (WI) with local anaesthetic and Erector Spinae Plane block (ESPB) have been described for post-operative analgesia after abdominal surgery. This study compared the efficacy of WI versus ESPB for post-operative analgesia after laparoscopic assisted colonic surgery. METHODS: Seventy-two patients between 18 and 85 years of age undergoing elective surgery were randomised to receive either WI or ESPB. In the WI group a 40 ml bolus of 0.5% Ropivacaine, infiltrated at the ports and minimally invasive wound at subcutaneous and fascia layers. In the ESPB group at T8 level, under ultrasound guidance, a 22-gauge nerve block needle was passed through the Erector Spinae muscle to reach its fascia. A dose up to 40 ml of 0.5% Ropivacaine, divided into two equal volumes, was injected at each side. Both groups had a multimodal analgesic regime, including regular Paracetamol, dexamethasone and patient-controlled analgesia (PCA) with Fentanyl. The primary end point was a post-operative pain score utilising a verbal Numerical Rating Score (NRS, 0-10) on rest and coughing in the post anaesthetic care unit (PACU) and in the first 24 h. Secondary outcomes measured were: opioid usage, length of stay and any clinical adverse events. RESULTS: There was no significant treatment difference in PACU NRS at rest and coughing (p-values 0. 382 and 0.595respectively). Similarly, there were no significant differences in first 24 h NRS at rest and coughing (p-values 0.285 and 0.431 respectively). There was no significant difference in Fentanyl use in PACU or in the first 24 h (p- values 0.900 and 0.783 respectively). Neither was there a significant difference found in mean total Fentanyl use between ESPB and WI groups (p-value 0.787). CONCLUSION: Our observations found both interventions had an overall similar efficacy. TRIAL REGISTRATION: The study was registered with the Australian New Zealand Clinical Trial Registry (ACTRN: 12619000113156 ).

The effect of advanced recovery room care on postoperative outcomes in moderate-risk surgical patients: a multicentre feasibility study.

Postoperative complications are common and may be under-recognised. It has been suggested that enhanced postoperative care in the recovery room may reduce in-hospital complications in moderate- and high-risk surgical patients. We investigated the feasibility of providing advanced recovery room care for 12-18 h postoperatively in the post-anaesthesia care unit. The primary hypothesis was that a clinical trial of advanced recovery room care was feasible. The secondary hypothesis was that this model may have a sustained impact on postoperative in-hospital and post-discharge events. This was a multicentre, prospective, feasibility before-and-after trial of moderate-risk patients (predicted 30-day mortality of 1-4%) undergoing non-cardiac surgery and who were scheduled for postoperative ward care. Patients were managed using defined assessment checklists and goals of care in an advanced recovery room care setting in the immediate postoperative period. This utilised existing post-anaesthesia care unit infrastructure and staffing, but extended care until the morning of the first postoperative day. The advanced recovery room care trial was deemed feasible, as defined by the recruitment and per protocol management of > 120 patients. However, in a specialised cancer centre, recruitment was slow due to low rates of eligibility according to narrow inclusion criteria. At a rural site, advanced recovery room care could not be commenced due to logistical issues in establishing a new model of care. A definitive randomised controlled trial of advanced recovery room care appears feasible and, based on the indicative data on outcomes, we believe this is warranted.

Comparison of ultrasound-guided transmuscular quadratus lumborum block catheter technique with surgical pre-peritoneal catheter for postoperative analgesia in abdominal surgery: a randomised controlled trial.

Following abdominal surgery, the provision of postoperative analgesia with local anaesthetic infusion through both transmuscular quadratus lumborum block and pre-peritoneal catheter have been described. This study compared these two methods of postoperative analgesia following laparotomy. Eighty-two patients 18-85 years of age scheduled to undergo elective surgery were randomly allocated to receive either transmuscular quadratus lumborum block or pre-peritoneal catheter block. In the transmuscular quadratus lumborum group, an 18-gauge Tuohy needle was passed through the quadratus lumborum muscle under ultrasound guidance to reach its anterior aspect. A 20-ml bolus of ropivacaine 0.375% was administered and catheters placed bilaterally. In the pre-peritoneal catheter group, 20 ml of ropivacaine 0.375% was infiltrated at each of three subcutaneous sub-fascial levels, and pre-peritoneal plane catheters were placed bilaterally. Both groups received an infusion of ropivacaine 0.2% at 5 ml.h-1 , continued up to 48 h along with a multimodal analgesic regime that included regular paracetamol and patient-controlled analgesia with fentanyl. The primary end-point was postoperative pain score on coughing, assessed using a numerical rating score (0-10). Secondary outcomes were pain score at rest, fentanyl usage until 48 h post-operation, satisfaction scores and costs. There was no treatment difference between the two groups for pain score on coughing (p = 0.24). In the transmuscular quadratus lumborum group, there was a reduction in numerical rating score at rest (p = 0.036) and satisfaction scores on days 1 and 30 (p = 0.004, p = 0.006, respectively), but fentanyl usage was similar. In the transmuscular quadratus lumborum group, the highest and lowest blocks observed in the recovery area were T4 and L1, respectively. The transmuscular quadratus lumborum technique cost 574.64 Australian dollars more per patient than the pre-peritoneal catheter technique.

Deaths in Incorrectly Identified Low-Surgical-Risk Patients.

BACKGROUND: The American Society of Anesthesiologists (ASA) physical classification system was developed for assessing anaesthetic risk, but is often also used to estimate surgical death risk. Patients with low ASA grades (ASA 1 or 2) are expected to have better surgical outcomes than patients with higher ASA grades (ASA ≥ 4). This study examined the course to death in patients classified as ASA 1 or 2 was examined, to investigate possible factors in unexpected deaths, in addition to evaluating the use of ASA grades by clinicians. METHODS: Patient data from the national surgical mortality audit of Australian hospitals were examined. The patient group was listed as ASA grade 1 or 2 by surgeons. Patients over 60 or under 20 were excluded in the final analysis, as were cases from New South Wales due to data not being available. A total of 357 cases were examined. Assessor summaries of the cases were examined, and ASA score reassessed to determine accuracy. RESULTS: More than 95% (n = 339) of cases listed as ASA 1 or 2 were found to have an incorrectly low grade, with 17.6% (n = 63) of cases listed as "expected" deaths. CONCLUSION: ASA grades appear to be misunderstood in the reporting of patient surgical risk. Many patient summaries list patients with severe systemic disease or expected deaths as ASA 1 or 2, contrary to the intended use of this classification system. Improved education on the use of the ASA grading system would be beneficial to clinicians.

Predicting patients at risk of early postoperative adverse events.

Adverse events after surgery are common. Identification of markers of at-risk patients may facilitate efficient and effective perioperative resource allocation. This pilot study aimed to identify simple preoperative factors associated with postoperative adverse events. In 1291 surgical patients, the relationship between patient and surgical factors and adverse events in the post-anaesthesia care unit was examined using binomial logistic regression analysis. Adverse events in the postoperative care unit were common, including desaturation (13.6%), hypotension (5.8%) and apnoea (5.5%), with 19.9% of cases requiring attendance by an anaesthetist to manage unexpected complications. Average length of stay in the post-anaesthesia care unit was 120 minutes and prolonged stay for medical reasons was common. A number of patient and surgical factors, including surgical complexity, preoperative arrhythmia, previous anaesthetic issues and heart failure were strongly associated with these adverse events. Areas under receiver operating characteristic curves ranged from 0.63 to 0.80. Patients with adverse events in the post-anaesthesia care unit appeared to have a higher risk of intervention in postoperative wards from a medical emergency or intensive care unit team. Our preliminary findings suggest that preoperative identification of key factors may have utility in determining risk of early postoperative problems and hence, aid perioperative planning.

The relationship between patient data and pooled clinical management decisions.

A strong relationship between patient data and preoperative clinical decisions could potentially be used to support clinical decisions in preoperative management. The aim of this exploratory study was to determine the relationship between key patient data and pooled clinical opinions on management. In a previous study, panels of anaesthetists compared the quality of computer-assisted patient health assessments with outpatient consultations and made decisions on the need for preoperative tests, no preoperative outpatient assessment, possible postoperative intensive care unit/high dependency unit requirements and aspiration prophylaxis. In the current study, the relationship between patient data and these decisions was examined using binomial logistic regression analysis. Backward stepwise regression was used to identify independent predictors of each decision (at P >0.15), which were then incorporated into a predictive model. The number of factors related to each decision varied: blood picture (four factors), biochemistry (six factors), coagulation studies (three factors), electrocardiography (eight factors), chest X-ray (seven factors), preoperative outpatient assessment (17 factors), intensive care unit requirement (eight factors) and aspiration prophylaxis (one factor). The factor types also varied, but included surgical complexity, age, gender, number of medications or comorbidities, body mass index, hypertension, central nervous system condition, heart disease, sleep apnoea, smoking, persistent pain and stroke. Models based on these relationships usually demonstrated good sensitivity and specificity, with receiver operating characteristics in the following areas under curve: blood picture (0.75), biochemistry (0.86), coagulation studies (0.71), electrocardiography (0.90), chest X-ray (0.85), outpatient assessment (0.85), postoperative intensive care unit requirement (0.88) and aspiration prophylaxis (0.85). These initial results suggest modelling of patient data may have utility supporting clinicians' preoperative decisions.

Pharmacokinetics of oxycodone after subcutaneous administration in a critically ill population compared with a healthy cohort.

This study aimed to characterise and compare the absorption pharmacokinetics of a single subcutaneous dose of oxycodone in critically ill patients and healthy subjects. Blood samples taken at intervals from two minutes to eight hours after a subcutaneous dose of oxycodone in patients (5 mg) and healthy volunteers (10 mg) were assayed using high performance liquid chromatography. Data were analysed using a non-compartmental approach and presented as mean (SD). Parameters were corrected for dose differences between the groups assuming linear kinetics. Ten patients (eight male, two female) and seven healthy male subjects were included. Maximum venous concentration and area under the concentration curve were approximately two-fold lower in the patient group for an equivalent dose, suggesting either reduced bioavailability or increased clearance: maximum venous concentration 0.14 ± 0.06 vs 0.05 ± 0.02 µg/ml (P <0.0001); area under the concentration curve 19.50 ± 9.15 vs 9.72 ± 2.71 µg/ml/minute (P <0.001) respectively. However, time to maximum venous concentration and mean residence time were not different, suggesting similar absorption rates: time to maximum venous concentration 22.10 ± 18.0 vs 20.50 ± 16.10 minutes (P=0.81); mean residence time 353 ± 191 vs 291 ± 80 minutes (P=0.26). Kinetic parameters were less variable in patients than in volunteers. The patients therefore had reduced exposure to subcutaneous oxycodone. This warrants further model-based analysis and experimentation. Dose regimens for subcutaneous oxycodone developed in healthy volunteers cannot be directly translated to critically ill patients.

An analysis of computer-assisted pre-screening prior to elective surgery.

In order to assess the potential utility of guided patient self-assessment as an early preoperative triage tool, a computer-assisted questionnaire delivered by a non-clinician via telephone was 1) compared to face-to-face interview and examination by anaesthetists in outpatient clinics and 2) evaluated as a mechanism to stream patients to day of surgery assessment. In total, 514 patients scheduled for elective surgery in two tertiary public hospitals were assessed initially by telephone and then in an outpatient clinic. Both forms of assessment were marked by panels of specialist anaesthetists, who also provided an opinion on which patients would have been suitable to bypass preoperative anaesthetic outpatient assessment based upon information provided by the telephone interview. Overall, the quality of assessment provided by non-clinician telephone interview was comparable to face-to-face interview by anaesthetists, although more complex issues required face-to-face assessment. Panel review considered that 398 patients (60%) would not have required evaluation by an anaesthetist until the day of surgery, thus avoiding the need to separately attend a preoperative outpatient clinic. The sensitivity of telephone interview provided information to correctly classify patients as suitable for day of surgery evaluation was 98% (95% confidence interval 96 to 99%) with a specificity of 97% (95% confidence interval 92 to 98%). This study demonstrates that remote computer-assisted assessment can produce quality patient health information and enable early patient work-up and triage with the potential to reduce costs through more efficient use of resources.

Cardiac output and propofol concentrations in prone surgical patients.

The aim of this study was to compare cardiac output and plasma propofol concentrations in the supine and prone positions in healthy adult patients presenting for lumbar spine surgery. Patients received propofol and remifentanil via effect-site steered target-controlled infusions. Cardiac output and plasma propofol concentration were compared during 20 minutes in the supine position and 20 minutes after positioning on a Wilson frame. Cardiac output did not change significantly over 20 minutes in either position (P = 0.37) and was similar at 20 minutes in the supine (6.1 [1.6] l/minute) and prone positions (6.1 [1.9] l/minute) (P = 0.87). Propofol concentrations were similar in the supine and prone positions at 20 minutes (2.55 [0.89] and 2.53 [0.90] microg/ml; P = 0.93). We conclude that prone positioning on the Wilson frame does not affect cardiac output or plasma propofol concentration.

Characteristics of plasma NOx levels in severe sepsis: high interindividual variability and correlation with illness severity, but lack of correlation with cortisol levels.

Objectives Nitric oxide (NO) concentrations are elevated in sepsis and their vasodilatory action may contribute to the development of hyperdynamic circulatory failure. Hydrocortisone infusion has been reported to reduce nitric oxide metabolite (NOx) concentrations and facilitate vasopressor withdrawal in septic shock. Our aim was to determine whether NOx concentrations relate to (i) protocol-driven vasopressor initiation and withdrawal and (ii) plasma cortisol concentrations, from endogenous and exogenous sources. Demonstration of a relation between NOx, cortisol and vasopressor requirement may provide an impetus towards the study of hydrocortisone-mediated NOx suppression as a tool in sepsis management. Design A prospective study of 62 patients with severe sepsis admitted to the intensive care unit. Measurements Plasma NOx, total and free cortisol, and corticosteroid-binding globulin (CBG) concentrations were measured and related to protocol-driven vasopressor use for 7 days following admission. Results Patients who developed septic shock (n = 35) had higher plasma NOx, total and free cortisol, and lower CBG concentrations than the nonseptic shock group (n = 27). Cortisol, CBG and NOx concentrations correlated with illness severity. Free cortisol, and to a lesser extent total cortisol, but not NOx concentrations, predicted septic shock. NOx concentrations were higher in nonsurvivors, and the concentrations were characteristically stable within individuals but marked interindividual differences were only partly accounted for by illness severity or renal dysfunction. NOx concentrations did not correlate with cortisol, did not relate to vasopressor requirement and did not fall after standard dose hydrocortisone, given for clinical indications. Conclusions Nitric oxide production increased with sepsis severity but did not correlate with plasma cortisol or vasopressor requirement. NOx levels were not suppressed reproducibly by hydrocortisone. High interindividual variability of NOx levels suggests that absolute NOx levels may not be a suitable target for individualized hydrocortisone therapy.

Adverse physiological events under anaesthesia and sedation: a pilot audit of electronic patient records.

Review of perioperative activity including adverse events, throughput and compliance with 'best practice', can theoretically be used to optimise healthcare delivery. Computer-based analysis of electronic patient records could provide a practical means to manage quality improvement. This pilot study examined the effectiveness of such a system in practice. All intraoperative patient notes and physiological data were collected over 17 months in a rural hospital using data from an electronic record-keeping system. Algorithms were developed to automatically identify potential adverse events based on physiological measures. Each computer-identified event was reviewed by a panel of three anaesthetists and assessed for validity, severity and probable cause. Two areas were identified to pilot quality improvement activities-sedation for colonoscopies and inhalational anaesthesia with desflurane. Specific 'in-house' guidelines were created for these procedures and feedback on the patterns of adverse events were provided to anaesthetic staff A total of 138 separate adverse events were identified for all operative cases over 17 months, with an overall adverse event incidence of 3.3%. The adverse event incidence during colonoscopy and laryngospasm/hypoxia during desflurane anaesthesia was 6.3% and 1.3% respectively. This decreased to 2.8% (P <0.005) and 0.13% (P <0.0001) respectively for the nine months following feedback and the introduction of guidelines. Anaesthesia information systems can be an effective quality improvement tool and may enhance existing tools such as incident reporting systems.

Cerebral cortical effects of desflurane in sheep: comparison with isoflurane, sevoflurane and enflurane.

BACKGROUND: Different volatile anesthetic agents have differing propensities for inducing seizures. A measure of the predilection to develop seizures is the presence of interictal spike discharges (spikes) on the electrocorticogram (ECoG). In this study, we investigated the propensity of desflurane to induce cortical spikes and made a direct objective comparison with enflurane, isoflurane, and sevoflurane. The ECoG effects of desflurane have not been previously reported. METHODS: After establishment of invasive monitoring and a parasagittal array of eight electrodes to record the ECoG; eight adult merino sheep were given a series of short inhalational anesthetics (using desflurane, enflurane, sevoflurane and isoflurane); each titrated to ECoG burst suppression. Anesthetic effect was estimated by the effects on the approximate entropy of the ECoG. The effect of anesthetic on the spike-rate in the ECoG was analyzed using a non-linear mixed-effect method with a sigmoid Emax model. RESULTS: A similar 'depth of anesthesia' was achieved for each agent, as estimated by the approximate entropy. The mean (SD) values of Emax for the spike-rate vs. approximate entropy relationship were desflurane 0.5 (0.9), enflurane 17.2 (4.0), isoflurane 0.7 (1.2), and sevoflurane 5.3 (1.2) spikes/min. The spike rate caused by desflurane was similar to isoflurane and significantly lower than that of enflurane (P < 0.001), and sevoflurane (P = 0.009). CONCLUSION: Desflurane induces minimal cerebral cortical spike activity when administered to burst suppression, consistent with its low propensity for inducing seizures in non-epileptic brains. The agents can be ranked by their relative ability to cause spike activity: enflurane >> sevoflurane > isoflurane = desflurane.