Low-dose desmopressin improves hypothermia-induced impairment of primary haemostasis in healthy volunteers.

Mild hypothermia (34-35 °C) increases peri-operative blood loss. We have previously demonstrated the beneficial effect of in vitro desmopressin on impairment of primary haemostasis associated with hypothermia. This study evaluated subcutaneous desmopressin in 52 healthy volunteers, randomly assigned to receive either normal saline or desmopressin 1.5, 5 or 15 µg (with 13 in each group). Blood samples were collected before and 2 h after drug administration and incubated at 32 and 37 °C. Platelet function analyser PFA-100(®) closure times were measured. Hypothermia at 32 °C prolonged mean (95% CI) closure times (for adenosine diphosphate/collagen by 11.3% (7.5-15.2%) and for adrenaline/collagen by 16.2% (11.3-21.2%); these changes were reversed by desmopressin. A very small dose was found to be effective (1.5 µg); this dose did not significantly change closure times at 37 °C, but fully prevented its prolongation at 32 °C. Subcutaneous desmopressin prevents the development of hypothermia-induced impairment of primary haemostasis.

Analgesic and sedative effects of intranasal dexmedetomidine in third molar surgery under local anaesthesia.

BACKGROUND: Dexmedetomidine (DEX) is an alpha 2-adrenoreceptor agonist, which induces sedation and analgesia. This study aimed to determine whether intranasal DEX offered perioperative sedation and better postoperative analgesia. METHODS: Patients having unilateral third molar surgery under local anaesthesia were recruited and allocated to receive either intranasal DEX 1 µg kg(-1) (Group D) or same volume of saline (Group P) 45 min before surgery. Patient-controlled sedation with propofol was offered as a rescue sedative. Perioperative sedation, postoperative pain relief and analgesic consumption, vital signs, adverse events, postoperative recovery, and satisfaction in sedation and analgesia were assessed. RESULTS: Thirty patients from each group were studied. Areas under curve (AUC) of postoperative numerical rating scale (NRS) pain scores 1-12 h at rest and during mouth opening were significantly lower in Group D (P=0.003 and 0.009, respectively). AUC BIS values and OAA/S sedation scores were significantly lower before surgery and at the recovery area (all P<0.01) with significantly less intra-operative propofol used in group D (P<0.01). In group D, heart rate was significantly lower at recovery period (P=0.005) while systolic blood pressure in different periods of the study (all P<0.01), but the decreases did not require treatment. More patients from placebo group experienced dizziness (P=0.026) but no serious adverse event was found. No difference was found in postoperative psychomotor recovery and satisfaction in pain relief and sedation. CONCLUSIONS: Patients receiving intranasal DEX for unilateral third molar surgery with local anaesthesia were more sedated perioperatively with better postoperative pain relief. No delay in psychomotor recovery was seen.

Value of a single preoperative PFA-100 measurement in assessing the risk of bleeding in patients taking cyclooxygenase inhibitors and undergoing total knee replacement.

BACKGROUND: The usefulness of the PFA-100 in assessing the risk of bleeding in non-cardiac surgery is not clear. This study aims to examine this by correlating preoperative PFA-100 measurement with perioperative bleeding in patients receiving cyclooxygenase (COX) inhibitors. METHODS: PFA-100 with adenosine-5'-diphosphate (ADPCT) and epinephrine (EPICT) cartridges were measured before operation in consecutive patients undergoing elective total knee replacement and taking different COX inhibitors. Surgery and anaesthesia were performed by the same team using standardized techniques. Intraoperative blood loss and postoperative drain output were recorded by anaesthetists and nurses blinded to the PFA-100 measurements. Surgeons, similarly blinded, were asked to rate the quality of haemostasis. Correlation was sought between these data and PFA-100 measurements. RESULTS: Thirty patients were studied, involving 51 knees. Preoperative PFA-100 EPICT was correlated with drain output (r=0.30, P=0.03). The correlation becomes stronger when a 20% in vitro haemodiluted sample was used for measurement (r=0.42, P=0.01). Receiver-operating characteristic curve analysis using the diluted measurements [area under curve (AUC) 0.74 (95% CI 0.54-0.94)] suggested using a cut-off value of 188 s for EPICT, which will predict excessive drain output with 89% sensitivity, 54% specificity, and a likelihood ratio of 1.93. Diluted EPICT was also correlated with surgeon rating of haemostasis (r=0.36, P=0.04) although none of the measurements correlated with intraoperative blood loss. CONCLUSIONS: Preoperative PFA-100 prolongation is correlated with increased postoperative drain output. It can be a potentially useful preoperative measurement in patients taking COX inhibitors.

A comparison of dexmedetomidine and midazolam for sedation in third molar surgery.

This randomised, double-blind study compared dexmedetomidine and midazolam for intravenous sedation during third molar surgery under local anaesthesia. Sixty patients received either dexmedetomidine (up to 1 microg x kg(-1)) or midazolam (up to 5 mg), which was infused until the Ramsay Sedation Score was four or the maximum dose limit was reached. Intra-operative vital signs, postoperative pain scores and analgesic consumption, amnesia, and satisfaction scores for patients and surgeons, were recorded. Sedation was achieved by median (IQR (range)) doses of 47 microg (39-52 (25-76)) or 0.88 microg x kg(-1) (0.75-1.0 (0.6-1.0)) dexmedetomidine, and 3.6 mg (3.3-4.4 (1.9-5.0)) or 0.07 mg x kg(-1) (0.055-0.085 (0.017-0.12)) midazolam. Heart rate and blood pressure during surgery were lower in dexmedetomidine group. There was no significant difference in satisfaction or pain scores. Midazolam was associated with greater amnesia. Dexmedetomidine produces comparable sedation to midazolam.

Delayed epidural catheter removal: the impact of postoperative coagulopathy.

A retrospective analysis of 413 patients who received postoperative epidural analgesia under a standardized protocol found that 84 (20%) had a duration of epidural catheterization of greater than four days. The most common reasons were significant pain (n=64, 15%) and coagulopathy (n=26, 6%). Risk factor analysis for coagulopathy showed an odds ratio of 10.1 (95% confidence interval 4.2-24.5) for prolonged epidural catheterization among patients undergoing hepatectomy. Magnetic resonance imaging, performed in four patients with clinical signs suggestive of epidural haematoma, was negative for a space-occupying lesion in all cases. Eleven patients developed fever and clinical signs suggestive of epidural catheter-related infection, necessitating early catheter removal. Sixteen patients had persistent lower limb weakness at 24 hours after catheter removal. The signs soon resolved in all except two, one of whom had neuropathy related to intraoperative positioning and the other preoperative weakness. Accidental epidural catheter dislodgement occurred in 29 patients (7%) and is potentially hazardous if coagulopathy is unresolved. The risk-benefit ratio and factors complicating catheter removal, especially coagulopathy, should be considered when deciding whether to use epidural techniques.

Neurolytic celiac plexus block for visceral abdominal malignancy: is prior diagnostic block warranted?

Neurolytic celiac plexus block is a recognised treatment for visceral abdominal pain due to malignancy. The need for a diagnostic celiac plexus block prior to neurolytic blockade is of questionable value, as it may not predict a positive response and may incorrectly predict a lack of response. Our objective is to evaluate the efficacy of diagnostic celiac plexus block. The records of 59 patients treated with celiac plexus block during 1994-2000 were retrospectively reviewed. Diagnostic block was performed on 32 patients prior to the decision for subsequent neurolytic block (Group 1). Another 27 patients were directly treated with a neurolytic celiac plexus block (Group 2). Response of Group 1 to diagnostic and neurolytic blocks was compared. Data from Group 2 was used to project the response of Group 1 should those patients with negative response to diagnostic block proceeded to neurolytic block. A two-by-two table was then constructed. The diagnostic celiac plexus block predicted a positive response with a sensitivity of 93% and a specificity of 37%. The positive predictive value was 85% and the negative predictive value was 58%. The estimated "number needed to test" before a "true" nonrespondent to lytic block to be detected was 16.7. Therefore, a positive response to diagnostic block correlates positively with neurolytic celiac plexus block for abdominal visceral pain due to malignancy. However, diagnostic block is a poor predictor when the response is negative. Hence, its clinical role is questionable and may not be warranted for patients with terminal malignancy.

In vivo effect of haemodilution with saline on coagulation: a randomized controlled trial.

BACKGROUND: Previous studies have shown that 10-30% haemodilution with crystalloid may induce a hypercoagulable state demonstrable by using the Thrombelastograph (TEG). While most are in vitro studies, the few in vivo studies are limited by confounding surgical or 'environmental' factors. We conducted this randomized controlled study to evaluate the coagulation changes associated with in vivo haemodilution. METHODS: Twenty patients undergoing major hepatobiliary surgery were randomly allocated to one of two study groups. Group H (n = 10) had 30% blood volume withdrawn over 30 min and replaced with saline. Group C (n = 10) did not have any blood withdrawn. Blood samples were taken in both groups at 10, 20 and 30 min. Native TEG, complete blood count, coagulation profile, fibrinogen, antithrombin III, protein C and thrombin-antithrombin complex concentrations were measured. RESULTS: Compared with Group C, Group H patients had significantly greater shortening of r-time at 30 min (-30% vs +36%), greater shortening of k-time at all time points (-36% vs +17% at 10 min; -37% vs +44% at 20 min; -45% vs +49% at 30 min), and greater widening of alpha at 30 min (+71% vs +4%). The decrease in antithrombin III and other natural procoagulants and anticoagulants closely followed that of haematocrit, with the exception of thrombin-antithrombin complex. CONCLUSION: In vivo haemodilution of up to 30% with saline can induce a hypercoagulable state. The mechanism remains unclear as disproportionate dilution of natural anticoagulants was not detected. Thrombin-antithrombin complex concentration remained stable despite haemodilution in Group H, which may suggest increased thrombin generation.

The application of clinical simulation in crisis management training.

Since it was first introduced more than 30 years ago, clinical simulation has become a popular tool for medical training, particularly in crisis management. The modern high-fidelity patient simulator consists of a whole-body mannequin with integrated electronic patient monitoring; it is controlled by computers capable of simulating numerous clinical scenarios and patient characteristics, and reacting to various interventions appropriately. Simulator training is theoretically superior to conventional training in management of rare crisis situations, as it allows unlimited practice in a safe yet familiar environment. Training in clinical skills can be developed, together with competency in crisis management behaviours such as leadership and communication skills. Although there is evidence demonstrating the popularity, reliability, and validity of simulator training, its superiority over conventional training has not been proven, and research in this area is required.