Hydroxyethyl starches and dextran during hip replacement surgery: effects on blood volume and coagulation.

BACKGROUND: Colloid fluids influence the coagulation system by diluting the plasma and, potentially, by exerting other effects that are unique for each fluid product. We hypothesised that changes in the coagulation measured at the end of surgery would be mainly governed by differences in half-life between the colloid fluids. METHODS: Eighty-four patients were randomised to receive one of four colloids: HES 130/0.42/6:1 (Venofundin(®)), 130/0.4/9:1 (Voluven(®)), 200/0.5/5:1 (Haes-steril(®)) and 6% dextran 70 (Macrodex(®)). Blood samples were taken just before and after a preoperative 500 ml bolus, and also after subsequent elective hip replacement surgery. Volume expansion was estimated from the blood dilution and coagulation assessed by ROTEM, activated partial thromboplastin time, prothrombin international normalised ratio (PT-INR), D-dimer and thrombin-antithrombin complex (TAT). RESULTS: The blood volume expansion amounted to approximately 600 ml for all four colloids directly after infusion. Voluven(®) and Haes-steril(®) prolonged the aPT time and Venofundin(®) increased TAT. Although all colloids increased PT-INR and D-dimer, the ROTEM analyses showed that they consistently shortened the clotting time and weakened the clot strength. These effects were mainly unchanged after surgery, during which the haemorrhage averaged 500-600 ml. Macrodex(®) produced a stronger volume support at the end of the surgery (91% of infused volume; P<0.001) than the three starch solutions (42-60%). CONCLUSIONS: All tested colloid fluids induced a mild hypercoagulable state with faster clotting, but with weaker clot strength. The additive influence of surgery was relatively small, and postoperative changes in coagulation were mainly due to differences in the half-life of each colloid.

Implementing a pre-operative checklist to increase patient safety: a 1-year follow-up of personnel attitudes.

BACKGROUND: The operating room is a complex work environment with a high potential for adverse events. Protocols for perioperative verification processes have increasingly been recommended by professional organizations during the last few years. We assessed personnel attitudes to a pre-operative checklist ('time out') immediately before start of the operative procedure. METHODS: 'Time out' was implemented in December 2007 as an additional safety barrier in two Swedish hospitals. One year later, in order to assess how the checklist was perceived, a questionnaire was sent by e-mail to 704 persons in the operating departments, including surgeons, anesthesiologists, operation and anesthetic nurses and nurse assistants. In order to identify differences in response between professions, each alternative in the questionnaire was assigned a numerical value. RESULTS: The questionnaire was answered by 331 (47%) persons and 93% responded that 'time out' contributes to increased patient safety. Eighty-six percent thought that 'time out' gave an opportunity to identify and solve problems. Confirmation of patient identity, correct procedure, correct side and checking of allergies or contagious diseases were considered 'very important' by 78-84% of the responders. Attitudes to checking of patient positioning, allergies and review of potential critical moments were positive but differed significantly between the professions. Attitudes to a similar checklist at the end of surgery were positive and 72-99% agreed to the different elements. CONCLUSION: Staff attitudes toward a surgical checklist were mostly positive 1 year after their introduction in two large hospitals in central Sweden.

Non-invasive measurement of systolic blood pressure on the arm utilising photoplethysmography: development of the methodology.

Photoplethysmography (PPG) can be used to measure systolic blood pressure at the brachial artery. With a specially designed probe, positioned in the most distal position beneath a pressure cuff on the upper arm, this is possible. The distance between the light source (880 nm) and the photodetector was 20 mm. A test was performed on neuro-intensive care patients by determining blood pressure from the PPG curves, and, when it was compared with systolic blood pressure obtained from inserted indwelling arterial catheters, a correlation factor of r = 0.95 was achieved. The difference between blood pressure obtained using PPG and invasive blood pressure measurement was 3.9 +/- 9.1 mmHg (mean +/- SD), n = 19. The depth to the brachial artery was 13.9 +/- 4.1 mm (mean +/- SD), n = 18. A digital PPG system utilising pulsating light was also developed.

Moderate hypothermia for 359 operations to clip cerebral aneurysms.

BACKGROUND: Experimental data have suggested that hypothermia (32-34 degrees C) may improve outcome after cerebral ischaemia, but its efficacy has not yet been established conclusively in humans. In this study we examined the feasibility and safety of deliberate moderate perioperative hypothermia during operations for subarachnoid aneurysms. METHODS: A total of 359 operations for intracranial cerebral aneurysms were included in this prospective study. By using cold intravenous infusions (4 degrees C) and convective cooling our aim was to reduce the patient's core temperature to more than 34 degrees C within 1 h before operation. The protocol assessed postoperative complications such as infections, prolonged mechanical ventilation, pulmonary complications and coagulopathies. RESULTS: During surgery, the body temperature was reduced to a mean of 32.5 (SD 0.4) degrees C. Cooling was accomplished at a rate of 4.0 (SD 0.4) degrees C h(-1). All patients were normothermic at 5 (sd 2) h postoperatively. Peri/postoperative complications included circulatory instability (n=36, 10%), arrhythmias (n=17, 5%) coagulation abnormalities and blood transfusion (n=169, 47%), infections (n=29, 8%) and pulmonary complications (infiltrate or oedema while on ventilatory support) (n=97, 27%). Eighteen patients died within 30 days (5%). There was no significant correlation between the extent of hypothermia and any of the complications. However, there was a strong correlation between the occurrence of complications and the severity of the underlying neurological disease as assessed by the Hunt and Hess score. CONCLUSION: Moderate hypothermia accomplished within 1 h of induction of anaesthesia and maintained during surgery for subarachnoid aneurysms appears to be a safe method as far as the risks of peri/postoperative complications such as circulatory instability, coagulation abnormalities and infections are concerned.

The in vitro effects of crystalloids and colloids on coagulation.

Classically haemodilution is regarded as causing coagulopathy. However, haemodilution with saline seems to cause a hypercoagulable state both in vivo and in vitro. The aim of the present study was to measure the effect of mild to severe haemodilution using thrombelastography. Blood samples were taken in 12 healthy volunteers and divided into seven aliquots. One aliquot was undiluted and acted as control. The other six were diluted with normal saline, Ringer Acetate, 4% albumin, Dextran 70, 6% and 10% hydroxyethylstarch to 10%, 20%, 40%, 50% and 60% dilution. The dilution was checked by measuring the haemoglobin concentration. Each aliquot was placed in a temperature-controlled thrombelastography channel. Increased coagulation activity, as measured by thrombelastography changes, was detected at low and medium levels of dilution with all the tested solutions. At more than 40% dilution, coagulation returned to normal while in the case of dextran and hydroxyethylstarch coagulopathy developed. For crystalloids and albumin,dilution had to exceed 50% before coagulation was impaired. If these findings can be reproduced in vivo, they may have implications for transfusion practice and prophylaxis against thrombosis.

High incidence of pruritus after large doses of hydroxyethyl starch (HES) infusions.

BACKGROUND: There are several studies indicating a correlation between treatment with hydroxyethyl starch (HES) and pruritus. In order to see whether there is a possible dose-response relationship between HES and pruritus, we retrospectively studied 50 patients who had received HES in varying doses (cumulative dose 500-19500 ml) as hemodilution therapy after subarachnoid hemorrhage. METHODS: Of 50 consecutive patients, 6 were excluded due to severe neurological sequelae. A questionnaire was sent to the remaining 44 patients at 6 months (5-12 months) median (range) after the end of HES treatment. RESULTS: We received answers from 37 patients, of whom 54% reported pruritus. On average pruritus lasted for 15 weeks. There was significantly more pruritus in patients who received more than 5000 ml of HES versus those who received less than 5000 ml (P=0.023). Pruritus had a delayed onset and appeared as pruritic crises lasting for 2-30 min. It had a patchy distribution in most patients and no predilected locations. In 4 patients (20%) the pruritus lasted longer than 21 weeks. CONCLUSION: Our study indicates that there is a dose-dependency for the incidence of HES-induced pruritus, and that in some cases the pruritus may be severe and long-lasting.

Respiratory monitoring during MR imaging. The clinical value of a new fibre-optical monitor.

PURPOSE: To assess the clinical utility of a fibre-optical monitor for respiratory monitoring in patients undergoing MR imaging without general anaesthesia. MATERIAL AND METHODS: One hundred consecutive patients were included at each of 3 MR units (300 patients in total). The technicians estimated the value of monitoring the respiratory rate on a 5-graded scale. Conditions that might complicate the MR examination were noted. RESULTS: The respiratory monitor was well tolerated by 99% of the patients. It was rated as valuable or very valuable in one-third of the total group, but in slightly more than two-thirds of the group of patients with some condition that might have complicated the MR examination. The estimated value of respiratory rate monitoring did not correlate to the age or sex of the patients, the type of examination, or to whether contrast medium was used or not, but it was significantly more often considered valuable in patients placed in the head-first position than in those placed in feet-first. CONCLUSION: Respiratory rate monitoring during MR imaging seems to be valuable in many patients, particularly if some condition that might complicate the MR examination is present.

Reversibility of severe sagittal sinus thrombosis with open surgical thrombectomy combined with local infusion of tissue plasminogen activator: technical case report.

OBJECTIVE: To explore the controversial issue of anticoagulant therapy and indications for surgery in association with severe sinus thrombosis. METHODS: During the last 4 years, we have treated three patients with severe sinus thrombosis of the dural sinuses. All three patients received systemic anticoagulant therapy and, after experiencing neurological deterioration, underwent open thrombectomy and local thrombolysis. After the operation, aggressive intensive care was given and included cerebral perfusion monitoring, barbiturate administration, hyperventilation, and osmotherapy. The treatment was guided by repeated neuroradiological investigations. RESULTS: All three patients returned to their normal lives. CONCLUSION: Intracranial sinus thrombosis, even in the worst neurological state, should be treated aggressively. A cornerstone in treatment is systemic anticoagulant therapy and repeated neuroradiological studies. When, despite adequate anticoagulant therapy and intensive care, neurological deterioration occurs, a combination of open thrombectomy and local thrombolytic therapy should be considered.

Cerebrospinal fluid concentrations of propofol during anaesthesia in humans.

The concentration of propofol in and surrounding the human brain during propofol anaesthesia is unknown. We measured simultaneously the concentration of propofol in cerebrospinal fluid (CSF) from an indwelling intraventricular catheter and the concentration in arterial blood in five neurosurgical patients before, during induction (at 2.5 and 5 min) and during a maintenance propofol infusion (at 15 and 30 min). After induction of anaesthesia with propofol 2 mg kg-1, anaesthesia was maintained with an infusion of 8 mg kg-1 h-1 for 15 min and then reduced to 6 mg kg-1 h-1. The plasma concentration of propofol increased rapidly during induction and reached a plateau concentration of mean 2.24 (SD 0.66) micrograms ml-1 after 5 min. The concentration of propofol in CSF showed a slower increase during induction and remained almost constant at 35.5 (19.6) ng ml-1 at 15-30 min after induction. The CSF concentration of propofol that we measured was 1.6% of the plasma concentration and consistent with the high protein binding of the drug in plasma.

The dual-tube microsurgical suction instrument.

A dual-tube suction instrument intended for both macro- and microsurgery has been developed. A detachable air-tight inner tube is fitted into a conventional suction instrument; extending the ordinary sucking tube. The inner tube can easily be fitted, as well as removed from the other tube; a particular advantage in case the inner tube becomes obstructed. On removal of the inner tube the outer tube becomes cleaned and is at once, ready for re-use. Since the suction instrument does not have to be removed from the suction hose, valuable time is saved, enabling permanent sucking capacity.

Advances in pulse oximetry.

The interaction between light and tissue is the basis of pulse oximetry. This review focuses on the recent development of pulse oximetry, with special emphasis on the reflection oximetry utilized in fetal and cerebral oximetry.

Giving both enoxaparin and dextran increases the need for transfusion in revision hip arthroplasty.

OBJECTIVE: To find out if the need for transfusion was increased by volume substitution with dextran 70 in patients receiving prophylaxis against thrombosis with low molecular weight heparin. DESIGN: Open randomised controlled trial. SETTING: University hospital, Sweden. SUBJECTS: 40 patients undergoing revision hip arthroplasty. INTERVENTIONS: Enoxaparin 40 mg was given daily. Intraoperative normovolaemia was maintained with albumin (n = 20) or dextran 70 (n = 20). Intraoperative autotransfusion was used. Packed cell volume was kept above 0.29, if necessary with homologous blood. MAIN OUTCOME MEASURES: External blood loss, red cell balance. RESULTS: Dextran patients received 0.64 (0.2) g/kg of dextran (mean (SD)) and required more (p < 0.05) homologous blood (3.8 (2.4) units) than those receiving albumin (2.3 (1.6) units). The initial and final packed cell volumes were similar (0.40 and 0.32 compared with 0.41 and 0.32, respectively). The calculated loss of red cells was larger in the dextran group (1401 (511) compared with 1077 (374); p < 0.05). CONCLUSION: The combination of enoxaparin and dextran appreciably increased the need for transfusion compared with enoxaparin alone.

Intracranial subdural haematoma--a rare complication following spinal anaesthesia.

We present a rare case with postspinal headache resulting in an intracranial subdural haematoma. After 5 days of persistant headache the condition was recognized and diagnosed on a computerized tomography-scan (CT) of the skull. The patient was operated with evacuation of the haematoma 2 weeks after the spinal anaesthesia and recovered completely.

Pulse oximetry--clinical implications and recent technical developments.

The pulse oximeter has been shown to be a reliable monitor of arterial oxygen saturation and has therefore been recommended as mandatory monitoring for patients during anaesthesia and intensive care. In 1989 two review articles on pulse oximetry were published (1, 2) and two years ago Severinghaus and Kelleher summarized the literature between 1989 and October 1991 (3). Our aim is to focus the discussion on technical aspects and applications of pulse oximetry with special attention centered on recent developments. This review is consequently an update on pulse oximetry since the end of 1991, and the first on technically-based publications in the two last decades.

Presentation and evaluation of a new optical sensor for respiratory rate monitoring.

A new optical sensor for respiratory rate monitoring was simultaneously compared with an acoustic sensor and a transthoracic impedance plethysmograph during normoventilation in the respiratory rate range of 9-17 breaths per minute. The response characteristics of the optical sensor were then measured during simulation of central apnoea and tachypnoea. Visual observation was chosen as the reference method for monitoring the respiratory rate. The measurements were performed in ten healthy volunteers and the respiratory signals recorded on an analogue tape and strip-chart recorder and analysed off-line. The response characteristics of the fibre optic sensor corresponded well with those of the acoustic sensor and impedance plethysmograph. All three methods responded rapidly to an apnoeic event.

Changes in end-tidal carbon dioxide during gynecologic laparoscopy: spontaneous versus controlled ventilation.

STUDY OBJECTIVE: To study the changes in PETCO2 during spontaneous and controlled ventilation in patients undergoing gynecologic laparoscopy. DESIGN: Randomized, unblinded study. SETTING: Department of Gynecology, University Hospital, Linköping, Sweden; Central Hospital, Norrköping, Sweden. PATIENTS: Forty healthy patients undergoing gynecologic laparoscopy. INTERVENTIONS: Patients were divided into 4 groups: Group 1 breathed spontaneously via an endotracheal tube, while the other three groups underwent controlled ventilation to an initial PETCO2 of 3 kPa (22 mmHg) (Group 2), 4 kPa (30 mmHg) (Group 3), or 5 kPa (37 mmHg) (Group 4). MEASUREMENTS AND MAIN RESULTS: PETCO2 levels were measured at fixed time intervals. Arterial blood gas analyses were done to compare the difference between PETCO2 and PaCO2. In Group 1, PETCO2 increased soon after insufflation and remained above 6 kPa (44 mmHg) throughout the procedure. In Groups 2, 3, and 4, PETCO2 also rose after insufflation, and an initial PETCO2 of 4 kPa (30 mmHg) was ideal, as all PETCO2 values were less than 5.5 kPa (41 mmHg). Occasional episodes of arrhythmia were seen in Group 1. However, no major adverse effects were observed in any of the groups. CONCLUSIONS: In view of the high PETCO2 levels, spontaneous breathing should be avoided during gynecologic laparoscopy, and ventilation to an initial PETCO2 of 4 kPa (30 mmHg) is recommended during controlled ventilation.

Alfentanil or fentanyl during isoflurane-based anaesthesia for day-care knee arthroscopy?

Forty patients agreed to participate in a study to compare whether fentanyl or alfentanil used as analgesic is associated with quicker recovery following anaesthesia for outpatient arthroscopy procedure. Psychomotor tests including choice reaction time (CRT), perceptive accuracy test (PAT) and finger tapping test (FTT) were done prior to induction of anaesthesia with propofol (2-3 mg.kg-1). Patients were then divided into two groups: Group F (fentanyl) received 0.1 mg fentanyl prior to start of surgery and thereafter 0.05 mg every 30 min during the procedure. Group A (alfentanil) received 0.5 mg alfentanil prior to the onset of surgery and 0.25 mg every 15 min thereafter. Anaesthesia was then maintained using isoflurane (0.5-2%) in oxygen and air (FiO2 0.33) during spontaneous respiration with a face mask in a Bain's system. Psychomotor tests were repeated every 45 min postoperatively. Clinical recovery, visual analogue pain intensity score (VAS) and time to discharge home were also assessed by a nurse blind to the method used. Patients in Group A returned to baseline values on the FTT after 90 min while those in Group F did not return to baseline values until 135 min after the end of the operation. Clinical recovery and time to discharge home ("home ready") were also significantly longer in Group F. There was no difference in recovery as seen in the PAT and CRT between the groups. Also, there was no difference in the incidence of side effects and the pain intensity (VAS) scores were similar in the two groups at all time periods.(ABSTRACT TRUNCATED AT 250 WORDS)

Experimental evaluation of two new sensors for respiratory rate monitoring.

Visual observation was chosen as the reference method for measuring the respiratory rate in ten healthy volunteers. The new fibre-optic and acoustic sensors were simultaneously compared with capnography and transthoracic impedance plethysmography during normoventilation in the respiratory rate range of 6-24 breaths per minute and at a fixed respiratory rate of 13 breaths per minute. In addition a simulation of central apnoea was performed. All the measurements were recorded on an analogue tape recorder and a strip-chart recorder and analysed off line. The analyses of the recordings were performed by a person who was unable to see the monitoring systems. There was no discrepancy in the results of these methods. Each of the methods responded rapidly to an apnoeic event. The new fibre-optic and acoustic sensors correlate well with more traditional methods such as capnography and transthoracic impedance plethysmography for respiratory rate monitoring.