Venous air embolism: does the site of embolism influence the hemodynamic changes?

Three hundred and ninety-seven patients undergoing posterior cranial fossa surgery in the sitting position were prospectively studied to evaluate the incidence of venous air embolism (VAE) and its effects on hemodynamics. End-tidal carbon dioxide (ETC02) tension was monitored to diagnose VAE. A sudden and sustained decrease in ETC02 of more than 5 mmHg, in the absence of sudden hypovolemia, was presumed to be the result of VAE. The site of probable air entrainment (whether muscle, bone or tumor) was noted. Hemodynamic consequences were managed symptomatically. ETC02 monitoring detected VAE in 22% of the patients. The highest incidence of embolism resulted from muscles and tumor (40% in each case). Forty-two per cent of patients developed hypotension during the embolic episode (systolic BP less than 100 mmHg). Ten per cent of patients developed ventricular arrhythmias during the embolic episode. Air aspiration was successful in 4.8%. There were no statistically significant differences in the frequency of VAE among the different groups (P>0.05). Also, the frequency of hypotension and ventricular arrhythmias were not significantly different, irrespective of the source of VAE (P>0.05). The general condition of the patients in the preoperative stage had no influence on the incidence of embolism, hypotension or ventricular arrhythmias.

Hemodynamic response to skull pins application in children: effect of lignocaine infiltration of scalp.

BACKGROUND: Skull pins application following local anesthetic infiltration of scalp obtunds hemodynamic changes in adults. No such study is available in children. METHODS: 30 children undergoing elective suboccipital craniectomy with skull pins fixation, were randomly allocated either to control group I, or lignocaine group II. Whereas in group I, pins were applied without any scalp infiltration. In group II, pins were applied 1 min. after scalp infiltration with 0.5% lignocaine (plain) at each pin site. RESULTS: Mean arterial pressure and heart rate were recorded during pinning (peak increase),1,4,7 and 10 min later, and were compared with the baseline (parameters recorded approximately 20 min. after intubation). Mean arterial pressure in group I peaked from 77.0 +/- 9.19 to 113.87 +/- 13.7mmHg (P<0.001) and remained significantly high throughout the study period. In Group II peak increase in mean arterial pressure was from 91.64 +/- 16.39 to 101.85 +/- 15.87 mmHg (P<0.01) and remained high till 1 min. only. Pins placement resulted in significant increase in heart rate only during pinning (peak increase) and up to 1 min. in both the groups (P<0.01). CONCLUSIONS: In children, skull pins placement 1 min. after scalp infiltration with 0.5% lignocaine plain fails to prevent the hemodynamic changes arising during pins placement (peak change) and up to 1 min. after pins placement. However, the technique successfully blocks these changes beyond 1 min. post skull pins fixation.

Cardiovascular responses to scalp infiltration with reduced concentration of adrenaline.

A prospective randomized controlled study was carried out in 41 adult neurosurgical patients to find out the hemodynamic effects following scalp infiltration with 0.5% lignocaine with or without adrenaline. The patients were divided randomly into two groups. Group I patients (n=21) received 0.5% lignocaine with adrenaline (1:8,00,000) for scalp infiltration and group II patients (n=20) received 0.5% lignocaine without adrenaline. Continuous monitoring of ECG, heart rate and arterial blood pressure was carried out every minute for 20 minutes following scalp infiltration. Blood loss while raising the scalp flap was assessed by the neurosurgeon who was unaware of the study. No significant hemodynamic disturbances were observed in either group. However, Group I patients had significantly (p=0.001) less bleeding on incision. From this study, we conclude that 0.5% lignocaine with adrenaline (1:8,00,000) does not give rise to any cardiovascular disturbances during and following scalp infiltration. Rather, it minimises blood loss while raising the craniotomy flap.

Sympathetic blockade for the relief of chronic pain.

The sympathetic blocks are useful in many ways for relief of chronic pain. The sympathetic block can be caused at pre- and paravertebral sympathetic ganglia eg, stellate ganglia, coeliac plexus and lumbar sympathetic ganglia. Indications for sympathetic blockade are: Complex regional pain syndrome, phantom limb pain, central pain, acute pancreatitis, pancreatic cancer and cancer pain from upper abdominal viscera. Stellate ganglion blockade is required for the diagnosis, prognosis and therapy for painful and other conditions associated with sympathetic dysfunctions of head, neck and upper extremity. Coeliac plexus block is indicated in pain due to intra-abdominal cancer, stemming from organs innervated by coeliac plexus. Lumbar sympathetic block is indicated for diagnosis, prognosis and therapy for painful and other conditions associated with sympathetic dysfunctions like complex regional pain syndrome I and II, herpes zoster, amputation stump pain and inoperable peripheral vascular vasospastic diseases of the lower limb. Indications for superior hypogastric block are the prognostic and therapeutic purposes of cancer pelvic organs--uterus, cervix, bladder, prostate, urethra, testes and ovaries.

Airway management in critically ill neurological patients.

Respiratory complications play an important part in the morbidity and mortality of critically ill neurological patients. Assurance of airway patency is of primary concern in such patients. A plethora of airway maintenance techniques and devices have been recommended for securing and maintaining the airway. But, translaryngeal intubation through the oral route is the safest and most preferred technique. Proper assessment and adequate preparation of the patient before intubation helps to avert crises. In difficult intubation one may secure and maintain the airway by placing a laryngeal mask airway (LMA). The role of early tracheotomy in patients who require prolonged ventilatory support can not be overemphasized. However, the development of inert and softer endotracheal tubes with low pressure cuff has reduced the complications associated with endotracheal intubation. Finally and most importantly the best place to acquire competence in securing the airway is the operation theater not the intensive care unit.

Epilepsy surgery in India: All India Institute of Medical Sciences experience.

OBJECTIVES: Surgical treatment of epilepsy should be considered an important alternative to medical therapy. The identification of a suitable candidate, pre-operative evaluation requires a multidisciplinary team. The specific diagnostic studies required depend on the operative strategy and objective of surgical treatment. METHODS: In twenty patients with medically intractable epilepsy, who had clinical evaluation, electroencephalography (EEG), video-EEG monitoring using scalp electrodes, high resolution magnetic resonance imaging (MRI), neuropsychology, single photon emission computed tomography (SPECT) was done to localise the seizure focus. If the investigations were concordant resective surgery was performed. In case of frequent falls, atonic and tonic seizures, with generalised/multifocal discharges on EEG, a callostomy was done. Surgical outcome was assessed using Engel's 4 point scale. RESULTS: In 18 patients the seizure focus was localised, 13 had temporal lobectomy, five extra-temporal resection, and two had callosotomy. Fifteen patients had a follow-up of more than eight months, mean 20.5 (range 8-35 months), 13 had outcome I (seizure free), two had outcome II (occasional seizures), one-outcome III. Three were lost to follow-up and one patient died. There were no major post-operative complications. CONCLUSIONS: Surgical treatment of epilepsy is a safe, effective mode of therapy. Suitable candidates should be identified early and referred to appropriate centres.

Comparative study on proper placement of central venous catheters with & without stillete.

Observing a standard protocol, central venous catheterization was performed, via the right basilic vein, in 100 patients. At random, 50 patients received a catheter with stillete and 50 without stillete. Catheter tip was localized on a chest radiograph; 78 per cent with stilletes and 80 per cent without stilletes were properly positioned (either in the right atrium or the superior vena cava). Most common aberrant placement was in the right ventricle (14% of each type of catheters), and this did not produce any ventricular arrhythmias. Eight per cent of catheters with stillete and 6 per cent without stilletes were malplaced into the ipsilateral internal jugular vein. The incidence of proper and improper placement was similar with the two types of catheters. Silent catheter migration into the right ventricle is very frequent than recognized when an estimated catheter length is inserted without radiologic control.

Potassium homeostasis during & after cardiopulmonary bypass.

Potassium homeostasis was studied in 30 patients undergoing cardiac surgery by employing cardiopulmonary bypass (CPB) and moderate hypothermia, and using morphine, N2O, relaxant anaesthesia. There was a trend for hypokalemia, and for maintaining a K+ level of 4-4.5 mmol/l, K+ infusion was required during CPB (9.017 mmol/m2 BSA/h). K+ infusion required in the post-operative period was considerably less (1.532 mmol/m2 BSA/h). There was no significant difference in the K+ levels of patients receiving preoperative diuretic therapy, as compared to those not receiving such therapy. Potassium requirement was significantly higher in patients under-going CABG and valvular heart disease, as compared to congenital heart disease. The mean urinary loss of K+ during bypass was found to be 2.95 mmol/m2 BSA/h, which was only 32 per cent of that required to be infused (9.017 mmol/m2 BSA/h). The mean excretion of K+ in the post operative period was significantly higher (4.53 mmol/m2 BSA/h) than K+ required to be infused during this period (1.532 mmol/m2 BSA/h).

End tidal carbon dioxide monitoring for detection of venous air embolism.

With the aim of defecting the potential hazard of air embolism, end tidal carbon dioxide (ETCO2) was monitored in 238 patients undergoing neurosurgery (in the sitting position), for early detection of venous air embolism (VAE). Fifty six episodes (26.3%) of significant fall in ETCO2 were observed in 41 patients (17.2%). Haemodynamic disturbances occurred in only 26 patients (10.9%) and were always preceded by a fall in ETCO2. Thirteen patients had positive air aspiration and cardiac murmurs were heard in only six. One patient suffered severe hypoxaemia (PaO2 = 55 mm Hg) whereas two had severe haemodynamic disturbances, but could be promptly resuscitated.