Dexmedetomidine Infusion without Loading Dose in Surgical Patients Requiring Mechanical Ventilation: Haemodynamic Effects and Efficacy

We investigated the haemodynamic effects and the efficacy of a continuous infusion of dexmedetomidine without a loading dose in 50 patients having had cardiac surgery (n=33), complex major surgery (n=9) and multiple trauma (n=8). The mean age was 60 (±16) years, and the mean APACHE II score was 13 (±5). Dexmedetomidine was commenced at an initial rate of 0.2 to 0.4 μg/kg/h (depending on whether anaesthetic or sedative agents had already been used) and rescue analgesia and sedation was administered with morphine and midazolam respectively. Propofol was used if additional sedation was needed. Sedation was targeted to a modified Motor Activity Assessment Score. Eighty percent of patients required no or “minimal” rescue therapy (<10 mg midazolam /day and/or <10 mg morphine/day and/or <100 mg propofol/day). The cardiac surgery group needed the least rescue therapy. A statistically significant but clinically unimportant reduction in mean heart rate and mean systolic blood pressure was observed over the first six hours (P<0.0001, and P=0.009 respectively). The baseline heart rate of 85 (±17) beats per minute (bpm), fell to a low of 78 (±13) bpm at four hours and then remained stable throughout the infusion period. The systolic blood pressure fell from 125 (±22) mmHg to a low of 112 (±20) mmHg at 1.5 hours with minimal change afterwards.

Dexmedetomidine was an effective sedative and analgesic in this group of complex surgical and trauma patients with pronounced benefit in the cardiac surgery group. Omitting the loading dose avoided undesirable haemodynamic effects without compromising sedation and analgesia.

Predictive Value of Quick Sepsis-Related Organ Failure Scores following Sepsis-Related Medical Emergency Team Calls: A Retrospective Cohort Study

We conducted a cohort study of adult ward patients who had a Medical Emergency Team (MET) call triggered by confirmed or suspected sepsis in an Australian tertiary centre to assess the predictive utility of systemic inflammatory response syndrome (SIRS) and quick Sepsis-Related Organ Failure Assessment (qSOFA) scores for 28-day mortality over a 12-month period. Sepsis was the causative aetiology in 970 MET calls for 646 patients with a mean age of 68 years and median Charlson Comorbidity score (CCS) of 3.0. Four hundred and seven (63%) patients had microbiological identification of a causative organism with 35 (9%) demonstrating multi–drug resistance. The 28-day mortality rate was 22%. Independent risk factors for 28-day mortality included age (incidence rate ratio [IRR] 1.038; P <0.001) and CCS (IRR 1.102; P <0.001). qSOFA positive patients had a threefold risk of 28-day mortality compared to those who were negative (IRR 3.15; P=0.02). Both the SIRS and qSOFA score had poor sensitivity (86% versus 62%, respectively) for mortality as a sole diagnostic tool and should be investigated as part of a multiparameter panel within a large prospective study.

Experience with high frequency oscillation ventilation during the 2009 H1N1 influenza pandemic in Australia and New Zealand

During the 2009 H1N1 pandemic, large numbers of patients had severe respiratory failure. High frequency oscillation ventilation was used as a salvage technique for profound hypoxaemia. Our aim was to compare this experience with high frequency oscillation ventilation during the 2009 H1N1 pandemic with the same period in 2008 by performing a three-month period prevalence study in Australian and New Zealand intensive care units. The main study end-points were clinical demographics, care delivery and survival. Nine intensive care units contributed data. During 2009 there were 22 H1N1 patients (17 adults, five children) and 10 non-H1N1 patients (five adults, five children), while in 2008, 18 patients (two adults, 16 children) received high frequency oscillation ventilation. The principal non-H1N1 high frequency oscillation ventilation indication was bacterial or viral pneumonia (56%). For H1N1 patients, the median duration of high frequency oscillation ventilation was 3.7 days (interquartile range 1.8 to 5) with concomitant therapies including recruitment manoeuvres (22%), prone ventilation (41%), inhaled prostacyclins (18%) and inhaled nitric oxide (36%). Seven patients received extracorporeal membrane oxygenation, six having H1N1. Three patients had extracorporeal membrane oxygenation concurrently, two as salvage therapy following the commencement of high frequency oscillation ventilation. In 2008, no high frequency oscillation ventilation patient received extracorporeal membrane oxygenation. Overall hospital survival was 77% in H1N1 patients, while survival in patients having adjunctive extracorporeal membrane oxygenation was similar to those receiving high frequency oscillation ventilation alone (65% compared to 71%, P = 1.00). Survival rates were comparable to published extracorporeal membrane oxygenation outcomes. High frequency oscillation ventilation was used successfully as a rescue therapy for severe respiratory failure. High frequency oscillation ventilation was only available in a limited number of intensive care units during the H1N1 pandemic.

Daily sedation interruption; a glass half empty?

The last decade witnessed an exponential rise in the number of publications addressing management of sedation during critical illness. In 1998 Kollef and colleagues1 suggested that the use of continuous infusions of sedatives may be associated with prolonged duration of mechanical ventilation and intensive care unit (ICU) stay. This was followed by a landmark study by Kress and colleagues2 who demonstrated significant reduction in ventilation time and ICU stay with daily interruption of sedative infusions (DSI). Subsequent investigations have been consistent with the notion that strategies that reduce sedation depth such as algorithms and protocols for sedation management3-5 and the use of validated sedation scales6 can improve patient outcomes. This academic exuberance led to an endorsement of these strategies, and in particular DSI, by the UK Department of Health ( www.clean-safe-care.nhs.uk ), the Institute for Healthcare Improvement ( www.IHI.org ) and Safer Health Care Now! ( www.saferhealthcarenow.ca ).

The Effect of Dexmedetomidine on Agitation during Weaning of Mechanical Ventilation in Critically ill Patients

Ventilated patients receiving opioids and/or benzodiazepines are at high risk of developing agitation, particularly upon weaning towards extubation. This is often associated with an increased intubation time and length of stay in the intensive care unit and may cause long-term morbidity. Anxiety, fear and agitation are amongst the most common non-pulmonary causes of failure to liberate from mechanical ventilation. This prospective, open-label observational study examined 28 ventilated adult patients in the intensive care unit (30 episodes) requiring opioids and/or sedatives for >24 hours, who developed agitation and/or delirium upon weaning from sedation and failed to achieve successful extubation with conventional management. Patients were ventilated for a median (interquartile range) of 115 [87 to 263] hours prior to enrolment, Dexmedetomidine infusion was commenced at 0.4 μg/kg/hour for two hours, after which concurrent sedative therapy was preferentially weaned and titrated to obtain target Motor Activity Assessment Score score of 2 to 4. The median (range) maximum dose and infusion time of dexmedetomidine was 0.7 μg/kg/hour (0.4 to 1.0) and 62 hours (24 to 252) respectively. The number of episodes at target Motor Activity Assessment Score score at zero, six and 12 hours after commencement of dexmedetomidine were 7/30 (23.3%), 28/30 (93.3%) and 26/30 (86.7%), respectively (P <0.001 for 6 and 12 vs 0 hours). Excluding unrelated clinical deterioration, 22 episodes (73.3%) achieved successful weaning from ventilation with a median (interquartile range) ventilation time of 70 (28 to 96) hours after dexmedetomidine infusion. Dexmedetomidine achieved rapid resolution of agitation and facilitated ventilatory weaning after failure of conventional therapy. Its role as first-line therapy in ventilated, agitated patients warrants further investigation.

Sedation and Delirium in the Intensive Care Unit: An Australian and New Zealand Perspective

A survey was conducted to determine sedation and delirium practices in Australian and New Zealand intensive care units.

The survey was in two parts, comprising an online survey of reported sedation and delirium management (unit survey) and a collection of de-identified data about each patient in a unit at a given time on a specified day (patient snapshot survey). All intensive care units throughout Australia and New Zealand were invited by email to participate in the survey.

Twenty-three predominantly metropolitan, level III Australian and New Zealand intensive care units treating adult patients participated. Written sedation policies were in place in 48% of units, while an additional 44% of units reported having informal sedation policies. Seventy percent of units routinely used a sedation scale. In contrast, only 9% of units routinely used a delirium scale. Continuous intravenous infusion is the primary means of patient sedation (74% of units). While 30% of units reported routinely interrupting sedation, only 10% of sedated patients in the snapshot survey had had their sedation interrupted in the preceding 12 hours. Oversedation appears to be common (46% of patients with completed sedation scales). Use of neuromuscular blockade is low (10%) compared to other published studies. Midazolam and propofol were the most frequently used sedatives. The proportion of patients developing delirium was 21% of assessable patients. Failed and self-extubation rates were low: 3.2% and 0.5% respectively.

In Australian and New Zealand intensive care units, routine use of sedation scales is common but not universal, while routine delirium assessment is rare. The use of a sedation protocol is valuable and should be encouraged.

Assessment of the agreement between cardiac output measured by bolus thermodilution and continuous methods, with particular reference to the effect of heart rhythm

Cardiac output (CO) is a fundamentally important haemodynamic parameter and its continuous measurement has the potential to enable early recognition of haemodynamic trends and earlier therapeutic response. A method of continuous cardiac output (CCO) monitoring is now available for clinical use. The accuracy and reliability of this method has been confirmed in clinical trials but not, to our knowledge, in the presence of abnormal heart rhythms. A comparison was made between CCO and bolus thermodilution methods, to determine if there is a greater difference between their respective determinations of CO when heart rhythm is abnormal. A convenience sample of 38 intensive care patients was used to obtain 410 comparisons of CCO and bolus CO determinations. Heart rhythm associated with each comparison was determined. The comparison produced a measurement bias of -0.07 l/min and limits of agreement of -1.77 to 1.63 l/min. The bias of the two measurements was -0.35 l/min for sinus rhythm, -0.19 l/min for sinus tachycardia and -0.12 l/min for atrial flutter/fibrillation. Increased temperature and heart rate did not affect measurement agreement. In conclusion, the agreement between the bolus and continuous methods is clinically acceptable and is unaffected by the heart rhythms of sinus rhythm, sinus tachycardia and atrial flutter/fibrillation.

Tests of six continuous flow CPAP devices

Six continuous flow CPAP devices were tested for pressure fluctuation and stability of inhaled oxygen concentration under conditions of simulated respiration. Four of the systems, the Ambu, Auspap, Downs'-Vital Signs and the Dräger are commercially available and two, the Prince Henry (PHH) and the Prince of Wales (POW) systems were assembled from Bird respirator parts, which were available in the respective Intensive Care Units. All appeared to be clinically effective. The Ambu offers convenience and economy of gases, the Dräger showed the least pressure fluctuations. Three of the four commercial systems lacked certain safety features which could more easily be added to the two non-commercial devices.

Effect of adrenaline, fentanyl and warming of injectate on shivering following extradural analgesia in labour

This prospective, controlled study was undertaken to determine whether addition of adrenaline or fentanyl to bupivacaine or warming of the injectate had any effect on the incidence of shivering following extradural analgesia in the labouring parturient. Eighty-four patients were sequentially allocated to four groups (control, warm injectate, extradural adrenaline and extradural fentanyl). The adrenaline group had the highest incidence of shivering, the warm injectate and fentanyl groups the lowest. Extradural fentanyl also seemed promising in reducing shivering in pre-block shiverers. This paper also explores the rapidity of temperature decay of solutions of bupivacaine in different clinical situations.