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.

A study of the attitudes of general surgical patients to the management of their postoperative pain showed that although 86% initially expressed satisfaction with their postoperative pain relief, a quarter of these did in fact have moderate, severe or unbearable, unalleviated pain. These, together with those who expressed dissatisfaction with their pain relief, constituted one third of the total number, indicating that a problem of postoperative analgesic management existed in the hospital. As a result, techniques of continuous intravenous infusion of narcotics and more frequent use of regional analgesia have been introduced.

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.

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.

We developed and introduced into clinical practice a leaflet to improve the delivery of information to patients before obtaining their consent to anaesthesia. The amount of information needs to be what a “reasonable” patient thinks appropriate; therefore we tested patients’ responses to three levels of information: “full” disclosure, “standard” disclosure (as contained in our leaflet) and “minimal” disclosure. Forty-five patients scheduled to undergo cardiac surgery were enrolled in the study. None of the information sheets caused a significant change in state anxiety score and only the “full” disclosure significantly increased knowledge about anaesthesia (P=0.016). All leaflets were easy to understand. When only one leaflet was provided 64–73% of patients thought the content was “just right”, whereas when all three leaflets were viewed together, 63% of patients thought the “minimal” leaflet withheld too much information.

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.

A closed-loop control system was constructed for automatic intravenous infusion of insulin to control blood sugar levels (BSL) in critically ill patients. We describe the development of the system. A total of nine subjects were recruited to clinically test the control system. In the patients who underwent closed-loop control of BSL, the controller managed to control only one patient's glycaemia without any manual intervention. The average BSL attained during closed-loop control approached the target range of 6-10 mmol/l, and had less deviation than when BSL had been maintained manually.

We conclude that closed-loop BSL control using a sliding scale algorithm is feasible. The main deficiency in the current system is unreliability of the subcutaneous glucose sensor when used in this setting. This deficiency mandates high vigilance during use of the system as it is being developed.

A retrospective review of obstetric anaesthesia charts was performed for all parturients receiving regional anaesthesia over a 22-month period. The incidence of headache, post dural puncture headache (PDPH) and various other complications of regional anaesthesia that had been prospectively assessed were noted, as was the anaesthetic technique used (epidural or combined spinal epidural (CSE)). PDPH was rare (0.44%) and occurred with similar frequency in those managed with either epidural or CSE anaesthesia or analgesia. The pencil-point spinal needle gauge (27 or 29) did not influence the incidence of PDPH. Following a CSE technique, the epidural catheter more reliably produced effective analgesia/anaesthesia as compared with a standard epidural technique (1.49% versus 3.18% incidence of replaced catheters respectively). We conclude, based on the results of this retrospective review, that CSE is acceptable with respect to the occurrence of PDPH and that it is possible it is advantageous in relation to the correct placement of the epidural catheter.

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.

Disorders of coagulation may occur after uncomplicated hepatic resection in patients who have normal preoperative coagulation profiles and liver function tests. We present a retrospective study performed in a tertiary care university teaching hospital examining changes in liver function tests and coagulation profiles in patients undergoing hepatic resection. Data were obtained for 124 patients. When compared to the preoperative values, prothrombin times were significantly increased throughout the postoperative period. Prolongation of the prothrombin time was related to both duration of surgery and hepatic resection weight. There was no relationship between prothrombin time and patient age. Disorders of coagulation occur after hepatic resection even in patients who have normal preoperative coagulation and liver function tests. This has implications for anaesthetic practice, particularly when considering the use of an indwelling epidural catheter in patients undergoing hepatic resection.