Dynamic output and control of the hypothalamic-pituitary-adrenal axis in critical illness and major surgery.

The hypothalamic-pituitary-adrenal (HPA) axis is a neuro-endocrine system that regulates circulating levels of glucocorticoid hormones. These hormones are vital for normal homeostasis and play a pivotal role in the response to stress. Levels of cortisol fluctuate throughout the day in a diurnal rhythm, underlying which is an ultradian rhythm of approximately hourly pulses, and this pulsatility directly affects transcriptional outcomes. Pulsatility is not the result of a 'pulse generator', but is inherent within the system as a result of negative feedback. These patterns of secretion change in both acute and chronic illness as a result of inflammatory mediators, splanchnic nerve output, and central nervous system control. Levels of cortisol in both normal and illness states are highly dynamic and so previously used static assessment tools for diagnosing corticosteroid related critical illness insufficiency (CRCI) are not likely to be useful. Therapeutic regimens have also failed so far, to take secretory patterns into account. In this review we look at the dynamic control and effects of glucocorticoids and frame in this context the current evidence surrounding steroid use in critical care and major surgery.

Anaphylaxis admissions to UK critical care units between 2005 and 2009.

Anaphylaxis is a life-threatening emergency that may necessitate admission to a critical care unit. There are no reports of the frequency of admission to critical care units for patients with anaphylaxis or indeed any description of their demographic characteristics or outcomes. We analysed all physician-diagnosed cases of anaphylaxis over a 5-year period in national audit data from critical care units across the UK. Over the period 2005-2009, there were 81 paediatric and 1269 adult admissions with anaphylaxis admitted to UK critical care units (0.1% of admissions to paediatric units and 0.3% of admissions to adult units). Absolute numbers in both children and adults rose year on year. There were comparable proportions of admissions in female and male children (female = 47% and male = 53%; rate ratios (RR) = 0.88, 95% CI 0.64-1.20), but a greater proportion of adult female admissions (female = 65% and male = 35%; RR = 1.83, 95% CI 1.68-1.99). Survival to unit discharge was 95% (77/81) for children, and survival to hospital discharge was 92% (1166/1269) for adults. Each UK critical care unit is likely to see at least one anaphylaxis case per year. The number of admissions has risen in both children and adults. Although admission ratios between the sexes were comparable in children, there was a female preponderance in adult life. Survival rates were high at over 90%.

LMA Supreme insertion by novices in manikins and patients.

The LMA Supreme has been suggested for use in emergency situations by medical personnel with no experience in endotracheal intubation. We evaluated the LMA Supreme when inserted by non-anaesthetists, firstly in a manikin and then in patients. Fifty airway novices inserted a LMA Supreme in a manikin without any complications so we proceeded to the patient phase. Fifty airway novices inserted the LMA Supreme in anaesthetised patients undergoing elective surgery. First time insertion success rate was 86% and overall insertion success rate was 100%. Mechanical ventilation was successful in all cases. Median (IQR [range]) time to establish an airway was 34 s (26-40 [18-145] s). Median (IQR [range]) pharyngeal seal pressure was 23 cmH(2)O (19-28 [13-40] cmH(2)O). There were no important complications. Results are consistent with previous studies of use of the LMA Supreme by airway experts. We conclude that the LMA supreme is suitable for use by airway novices. Further research is needed before it may be recommended for cardiopulmonary resuscitation and emergency airway use.

Case series: Protection from aspiration and failure of protection from aspiration with the i-gel airway.

We present three patients of regurgitation while using the i-gel supraglottic airway in 280 patients. In two patients, the i-gel completely protected the airway from aspiration. In one patient, it did not provide complete protection. The i-gel has features designed to separate the airway and gastro-intestinal tracts and as such should offer some protection against aspiration. However, the efficacy of these features has not been confirmed, and further study is required to determine the safety profile of the device.

I-gel insertion by novices in manikins and patients.

The i-gel, a novel supraglottic airway, has been proposed for use during cardiopulmonary resuscitation. We evaluated the performance of this device in manikins and anaesthetised patients when used by novices: medical students, non-anaesthetist physicians and allied health professionals all unfamiliar with the i-gel. Fifty i-gels were placed in manikins. Eighty-eight percent (44/50) were placed on the first attempt with a median insertion time of 14 s (range 7-45). I-gels were placed in 40 healthy anaesthetised patients. Success on the first attempt was 82.5% (33/40) and on the second attempt 15% (6/40). After three attempts there were no failures. Median insertion time was 17.5 s (range 7-197). Median airway seal was 20 cmH(2)O (range 13-40). One case of regurgitation and partial aspiration occurred. Our results suggest the i-gel is rapidly inserted in both manikins and patients by novice users and compares favourably to other supraglottic airways available. Further work determining safety and efficacy during cardiopulmonary resuscitation is required.

Analysis of 1000 consecutive uses of the ProSeal laryngeal mask airway by one anaesthetist at a district general hospital.

BACKGROUND: The ProSeal laryngeal mask airway (PLMA), introduced to UK practice in late 2001, offers potential performance and safety benefits over other airways such as the classic laryngeal mask airway. There are no large series reporting its use. METHODS: Data from a prospective, consecutive series of 1000 size 3-5 PLMA uses, by one anaesthetist, were analysed to examine whether performance in routine and advanced practice is similar to that reported in formal trials. RESULTS: Patients were female in 52% of cases, median age 52 (range 8-101) yr, median weight 78 kg (10% over 100 kg, 24% over 90 kg). Procedures included 12% laparoscopic and 5% open abdominal surgery. Overall insertion success was 99.4%, (first and second attempt success 85% and 12%, respectively). Median insertion time was 12 s (93% <30 s). Insertion success did not differ between genders, or between mask sizes. Median airway seal was 32 cm H(2)O (range 8-40, 94% seal >20 cm H(2)O). Specific tests confirmed correct positioning in 98.5% of cases. Of six failures, two occurred during management of difficult airways. Minor airway obstruction occurred in 2.7%. Blood was visible on 8% of removed PLMAs and more commonly after more than one insertion attempt (38 vs 4.7%, chi(2) P < 0.0001). In three cases minor regurgitation without aspiration occurred. CONCLUSIONS: In the hands of a regular user, the PLMA was associated with a high rate of insertion success during routine and advanced use in relatively unselected patients. Correct placement rates approached 100%. The incidence of complications was low.