Anaesthesia and Intensive Care

In this study, we evaluated the performance of a humidified nasal high-flow system (Optiflow™, Fisher and Paykel Healthcare) by measuring delivered FiO₂ and airway pressures. Oxygraphy, capnography and measurement of airway pressures were performed through a hypopharyngeal catheter in healthy volunteers receiving Optiflow™ humidified nasal high flow therapy at rest and with exercise. The study was conducted in a non-clinical experimental setting. Ten healthy volunteers completed the study after giving informed written consent. Participants received a delivered oxygen fraction of 0.60 with gas flow rates of 10, 20, 30, 40 and 50 l/minute in random order. FiO₂, F_EO₂, F_ECO₂ and airway pressures were measured. Calculation of FiO₂ from F_EO₂ and F_ECO₂ was later performed. Calculated FiO₂ approached 0.60 as gas flow rates increased above 30 l/minute during nose breathing at rest. High peak inspiratory flow rates with exercise were associated with increased air entrainment. Hypopharyngeal pressure increased with increasing delivered gas flow rate. At 50 l/minute the system delivered a mean airway pressure of up to 7.1 cmH₂O. We believe that the high gas flow rates delivered by this system enable an accurate inspired oxygen fraction to be delivered. The positive mean airway pressure created by the high flow increases the efficacy of this system and may serve as a bridge to formal positive pressure systems.

Intensive care medical and nursing staff self-rate their communication skills as improved following attendance at the European Donor Hospital Education Programme (EDHEP) workshop. A prospective study was conducted to determine what impact EDHEP has on communication skills. Doctor-nurse pairs from 10 experimental and 10 control Intensive Care Units undertook two standardized simulated relative encounters (Breaking Bad News and Donation Request) at three measurement points (pre, post and follow-up).

Nurses showed no change in communication skills. Experimental group doctors showed significant improvement in breaking bad news and requesting donation; most of these improvements were not maintained. Control group doctors showed some improvement in breaking bad news, indicating that participating in measurement by itself initiates some transient change in communication skills.

Attendance at EDHEP does lead to significant improvement in some, but not all, communication skills essential in breaking bad news and requesting donation. Further research is necessary to determine what factors additional to EDHEP will contribute to enduring change in these particular skills.

Aspirin-sensitive asthma, aspirin-intolerant asthma, aspirin- (or non-steroidal anti-inflammatory drug [NSAID]) exacerbated respiratory disease are terms for a disorder commonly described as affecting adults aged >30y. With this perception, ibuprofen was administered for postoperative pain management to a 17-year-old boy with allergic rhinitis and previous severe asthma (at a time when well controlled), who then had a severe asthma exacerbation. Analysis of the literature in response to this case highlights four points:

1) NSAID-exacerbated asthma is not only a disorder of adults; it occurs in up to of 2% in asthmatic children, approaching probably 30% in older children with severe asthma and nasal disease.

2) The asthmatic reaction is dose-dependent and can occur with sub-therapeutic doses. Oral NSAID/aspirin challenge should be conducted in an environment where a severe asthma exacerbation can be appropriately managed.

3) The therapeutic use of non-selective [COX-1 preferential] NSAIDs should be avoided when sensitivity is known or suspected in adults and teenagers with severe asthma and chronic rhinosinusitis or nasal polyps. Use of these agents in younger children with mild episodic wheeze is probably safe.

4) Paracetamol use is probably safe, but aspirin-exacerbated respiratory disease may occur with clinical doses in a subgroup of aspirin-exacerbated respiratory disease patients. COX-2 selective inhibitors are probably safe, although this is controversial. Opioids and tramadol are suitable analgesic alternatives for patients with known or suspected susceptibility.

The efficacy of ginger for the prevention of postoperative nausea and vomiting was studied in a double-blind, randomized, controlled trial in 108 ASA 1 or 2 patients undergoing gynaecological laparoscopic surgery under general anaesthesia. Patients received oral placebo, ginger BP 0.5g or ginger BP 1.0g, all with oral diazepam premedication, one hour prior to surgery. Patients were assessed at three hours postoperatively. The incidence of nausea and vomiting increased slightly but nonsignificantly with increasing dose of ginger. The incidence of moderate or severe nausea was 22, 33 and 36%, while the incidence of vomiting was 17, 14 and 31% in groups receiving 0, 0.5 and 1.0g ginger, respectively (odds ratio per 0.5g ginger 1.39 for nausea and 1.55 for vomiting). These results were essentially unchanged when adjustment was made for concomitant risk factors. We conclude that ginger BP in doses of 0.5 or 1.0 gram is ineffective in reducing the incidence of postoperative nausea and vomiting.

This study compared the cardiac output responses to haemodynamic interventions as measured by three minimally invasive monitors (Oesophageal Doppler Monitor, the VigileoFlotrac and the LiDCOrapid) to the responses measured concurrently using thermodilution, in cardiac surgical patients. The study also assessed the precision and bias of these monitors in relation to thermodilution measurements.

After a fluid bolus of at least 250 ml, the measured change in cardiac output was different among the devices, showing an increase with thermodilution in 82% of measurements, Oesophageal Doppler Monitor 68%, VigileoFlotrac 57% and LiDCOrapid 41%. When comparing the test devices to thermodilution, the kappa statistic showed at best only fair agreement, Oesophageal Doppler Monitor 0.34, LiDCOrapid 0.28 and VigileoFlotrac -0.03. After vasopressor administration, there was also significant variation in the change in cardiac output measured by the devices. Using Bland-Altman analysis, the precision of the devices in comparison to thermodilution showed minimal bias, but wide limits of agreement with percentage errors of Oesophageal Doppler Monitor 64.5%, VigileoFlotrac 47.6% and LiDCOrapid 54.2%. These findings indicate that these three devices differ in their responses, do not always provide the same information as thermodilution and should not be used interchangeably to track cardiac output changes.

The USCOM (Ultrasonic Cardiac Output Monitors) device is a noninvasive cardiac output monitor, which utilises transaortic or transpulmonary Doppler flow tracing and valve area estimated using patient height to determine cardiac output. We evaluated USCOM against thermodilution cardiac outputs and transoesophageal echocardiography valve area measurements in 22 ASA PS4 cardiac surgical patients. Data collection commenced following pulmonary artery catheter insertion, with cardiac output measurements repeated after sternotomy closure. Failure to obtain transaortic Doppler readings using USCOM occurred in 5% of planned measurements. USCOM transaortic analysis was not planned for 11 patients with known aortic disease. Bias at the aortic window (n = 20) was -0.79 l/min with limits of agreement from -3.66 to 2.08 l/min. At the pulmonary window, failure to obtain Doppler readings occurred in 24% of planned measurements. Bias at the pulmonary window (n=36) was -0.17 l/min with limits of agreement from -3.30 to 2.97 l/min. The USCOM estimates of valve area based on height showed poor correlation with the echocardiographic measurements of aortic and pulmonary valves (r=0.57 and r=0.17, respectively). It was concluded that USCOM showed poor agreement with thermodilution. The estimated valve area was identified as one source of error.

Advanced haemodynamic monitoring remains a cornerstone in the management of the critically ill. While rates of pulmonary artery catheter use have been declining, there has been an increase in the number of alternatives for monitoring cardiac output as well as greater understanding of the methods and criteria with which to compare devices. The PiCCO (Pulse index Continuous Cardiac Output) device is one such alternative, integrating a wide array of both static and dynamic haemodynamic data through a combination of trans-cardiopulmonary thermodilution and pulse contour analysis. The requirement for intra-arterial and central venous catheterisation limits the use of PiCCO to those with evolving critical illness or at high risk of complex and severe haemodynamic derangement. While the accuracy of trans-cardiopulmonary thermodilution as a measure of cardiac output is well established, several other PiCCO measurements require further validation within the context of their intended clinical use. As with all advanced haemodynamic monitoring systems, efficacy in improving patient-centred outcomes has yet to be conclusively demonstrated. The challenge with PiCCO is in improving the understanding of the many variables that can be measured and integrating those that are clinically relevant and adequately validated with appropriate therapeutic interventions.

An anaesthetic technique for laryngeal microsurgery is described and evaluated using intravenous propofol infusion and topical lignocaine with the patient breathing spontaneously without an endotracheal tube. Eighty adult patients divided into two groups according to their ASA status (Group A; 58 ASA I and II; Group B; 22 ASA III and IV) were analysed. Operating conditions were good in all but one case. Good anaesthesia was achieved in about 70% of patients. The requirement for propofol was less in Group B. Blood pressures decreased signifcantly following induction (P < 0.001) but returned towards the preoperative values after ten minutes in Group A patients whereas the recovery was slower in Group B. Apnoea occurred on induction in about 40% of patients overall. P_aco₂ showed a similar small increase in both groups. Oxygenation was adequate. The results show that propofol as an infusion in this simple tubeless technique is satisfactory. As the technique was considered potentially hazardous in those patients with upper airway obstruction, such patients were not included in this study.’

A Perioperative Service has recently been introduced at Liverpool Hospital, a 460-bed university teaching hospital. This provides a co-ordinated system for managing all elective surgical patients from the time an admission is booked until hospital discharge. This paper describes the patient assessment, structure and staff requirements, benefits of and problems encountered with this service.

The patient's preoperative preparation occurs before hospital admission. Where possible, patients are admitted on the day of procedure, either as a day-only patient, or a day-of-surgery patient. Patients are initially admitted to a specifically designed Perioperative Unit, adjacent to the Operating Theatre Suite. Patients do not enter the surgical wards until after their operation. Planning of the hospital discharge process commences at the time of booking for operation.

Introduction of the Perioperative Service was staged process commencing in mid-1992. The hospital admits approximately 6,400 elective surgery cases each year. From July 1992 to December 1994, day-only patients were approximately 45% of these cases. Day-of-surgery admission patients increased from 6% to 35% of all cases over the same period. Appproximately 22% of elective surgical cases were seen in the Perioperative Clinic.

As the Perioerative Service became fully operational, the average length of stay for elective surgical procedures fell. There has been a reduction in the areas of cancellations due to unavailablity of beds, inappropriate preparation of patients, and non-attendance of patients for booked procedures. Patient acceptance is high. The existence of a perioperative system facilitates the planning and management of elective surgery with maximum quality and efficiency.